Reviewon Groundwater Nitrate Contamination ...

Japan Rainwater Catchment JapanRainwaterCatchmentSystems

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Reviewon

Groundwater Nitrate Contamination: Causes, Effects and Remedies

-A GuidelineforEtheientManageinent Strategies -

Md, Abul Fazali,MasayukiImaizumi2, Ishida3,[[bshihikoKawachi4, [RikeoTsuchihara5, JunichiroTakeuchi6Satoshi and Abul Hasan Md. Badiul Alam7 Abstract: Literaturesare reviewed to give aii overview of the causes, effects and rcmedies nitrate contamination. It isevident that groundwater nitrate contamination isa worldwide needs to be controlled because of itsimplications on human hcalth. Many environmental, drologicaland agricultural factorsare associated with groundwater nitratc contamination. sources, mainly due to application of excess nitrogen-based fertilizer to the agricultural and

manure,

uncontrolled

septic

tanks,

be

cause

nitrate

contamination.

As

a remedy

of groundwater problern,which geological,hyAnthropogenic fields,Iivestock

thc problem,

of

treat-

but treatment process isexpensive and all nitrates cannot be removcd frorn the water by any of the techniques. Therefore,rather than nitrate removal from cont･aminated water, protection of groundwater frornpotentialcontarnination ispreferred,A locationspecific management rnodel isindeed needed, which establishes the relationship between the managernent indicators and thc groundwater nitrate concentration. Literaturesshow that-usual processes of managing nitrate-contarninated aquifers are: to identify the sources and causes of containination and then to find out a maiiagernent model either by aquifer vulncrability analyses or simulation technique. However, in most of the cases it isvery diMcultto construct a definitecorrelation between the groundwater nitrate conc,entrations and aquifer vulncrability limitsmanagement of nitrate-contaminated potential indicators,which aquifers using the vulnerability map. On the other hand, groundwater nitrate sinrulation is also complicated due to the comp]exity of nitrate leachingfiuxestimation. Most of the nitrate simulation models are require many input parameters, thus limitingtheir actual fieldapplication. physically-based,which On the contrary, there are very few conceptual models requiring lessdata, but t･heirpredictivecapability with regard of assessing the impacts of alternativernanagement these practices is questionable, To overcotne problerns we must, have to find out alternative techniques. For instance,incorporatingArtificial Neural Network (ANN)in vulnerability analyses or developingnitrate leachingrnode] of conceptual quasi-physical type may bc a solution. Keywords: Groundwaternttrate contamtnatton; Causes; Effects; Remedtes; Management strategzes ment

of contaminated

water

may

a

sol-tion,

1 Introduction

In many countries of the world, groundwater isthe important source of water supply for domestic, industrialand agricultural needs, Groundwater makes twenty-two percent of the world's supply of t'reshwater 1999). In the United States, (pt'Iiller, groundwaterprovides drinking water formore than up

about

IJSPS Post-DoctoralResearch Fcllow, Laboratory of Groundwater Resources, Department of RegionalResources, NationalInstitute for Rural Engineering, 2-1-6 Kannondai, Tsukuba-shi, Ibaraki, 305-8609 Japan 2Head of Laboratory, Laboratory of Groundwater Resources, Department ef Regioiial Resources,NationalInstitute for Rural Engineering, 2-1-6 Kannondai, Tsukllba-shi, Ibaraki, 305-8609 Japan 3Senior Researcher, Laboratory ofGroundwater Resources, Department of Regional Resources, NationalInstitute for RuEngineering,2-1-6 Kannoiidai, Tsukuba-stii, Ibaraki,3058609 Japan aProfessor, Graduate Schoolof Agricultural Science, Kyoto IJnivcrsity,KiLashirakawa-oiwakc-cho, Sakyo-ku, Ky.oto, 6e68502 Japari OResearcher, Laboratory of Groundwater Re$ources,Deof Regioria] Resources, National Institute for Rural part,iiient Engineering, 2-1-6 Kannondai,T$ukuba-shi, Ibaraki, 305-8609 ral

Japan

SInstructor,

Graduate Schoel"f Agricultural Science,KyUTiiversity, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto, 6e6-8502 Japar] 7Postgraduate Student,Graduate School ef Agricultural Sci{mce, KyoLo University, Kitashirakawa-oiwake-cho, Sakyooto

ku, Kyoto. 606-8502 Japari

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the Nation'spopulation and itisthe sole

one-halfof source and

of some

drinking water formany large cities

gle largestconsumer is agriculture, where

rural

communities

(Solley 1993). The sinof water in the United States et

more

al.,

than one-hundred

billion

gallons of water are used each day forthe irrigation of crop land (Miller, 1999). Literaturesshow that most of the countries depend, at leastpartially,on groundwater to mect their water demaiid. In many parts of India, Thailand, Vietnam, Bangladesh and Japan, groundwater is the sole source of water supHowever,' nowaply fbr various human activities. days,nitrate in groundwater has become one of the key environmental issues because of itsirnplications

human health. In recent years, groundwatcr nitrate contamination has been reported from many countries of the world. It has fbund in the United States,UK, Denmark, the Netherlands,Czech Republic,Lebanon, Costa Rica, Africa, China, Japan, India, Vietnam, Israel,Turkey, Australia,New Zealand and many other countries. Hallberg(1989) stated that concentration of nitrate in groundwater has raised 60 fbld in USA. In the USA, groundwater nitrate contarnination was found in mariy places, such as in California(Pfenning and McMohan, 1996; Zhang et al., on

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1998), in Virgiiiia 2003), in Texas (HuChemical formulafbrnitrate isNOi. Nitrogensimu(Bhmnbla, et al., 1998), in Illilation rnodels are based on the nitrogen cycle. There dak, 2000),in Indiana (Bernard many literatures on nitrogen cy, cle in different･ scinois et al., 2000), and in Arkansas axe (Samuel (Peterson 1 repreet al., 2002). According to WHO in USA in entific and in the Internet. Figure (1998) joiirnals 1986, a nitrate concentration of 44 mg/L sents the nitrogen cycle which iscomplied from rnany (10mg of in 40 surface water literaturescollected from the Internetand the nitre N03-N per liter) was exceeded 1)y and 568 groundwatersupplies. A nitrate concentragen cycle described Birkinshawand Ewen (2000), Tindall et al. (1995) and Boltz tion up to 1,500 mglL was found in groundwater in Lunn et at. (1996), an

agricult･ural

area

of

India. In Denmark

(1978).

thc

and

Netherlands,nitrate concentrations are increasing by O.2to 1.3mg/L per year in some areas. In 15 Euronearly 10 rnillioiipcopleare exposed pean countries, to

levels in drillking water

nitrate

national

nitrate

A

(50mglL,

standard

above

expressed

the interin terins of

that in Scotland many aquifers covering 200,OOO km2 areas are at risk from nitrate contamination and MacDonald, 2001). During the lasttwo decades,groundwater nitrate concentration in Japan has increasedsteadil,v. due to the de-

intensiveagriculture.

In

some

Japan

100 mg/L,

was

Africa,Girard and

(1999)

(1995)

problem and we are in a continuous threat it. Therefore,forthe survival of our futuregenerwe have to our ation, protect groundwaterenviron-

of

ment,

2

The out

main

aiin

of

thc causes,

ter nitrate

this

effects

literature review and

coiitamination

guideline for the coiitaminated

eMcient

remedies

to

and

of

provide

management

is to find groundwaa of

detailed nitrate-

groundwateraquifers.

cycle

icalmodification

16eeJOURNAL

of

nitrite

speciaiized

OF RAINWN'ER CNCHMENT

bacteria.

SYSTEMS

and

main

nitrogen nitrate

of

components

am-

eomponent,

cornponent,

cycle are:

the

and nitrogen

deposition, 2)

fixation by

nitrogen

changes to NOi after mixing with rainisdepositedto the soil. This NOi directly contributes to the nitrate partof the nitrogen cycle, Some NH4+ may also produceby the atmospheric fixation, which directly contributes to the ammonium of the nitrogen cycle, In the industry,nitropart is fixed with other eompounds, high temperature gen make nitrogen-based fertilizers and pressure to ammonium nitrate, etc.), Nitrogen can be readily

then

(urca,

available

after

of

application

soil.

to

the

cycle.

crops

AIfalfa)can (Soybeans, and

nitrate

part

or

gen

fertil-

nitrogen-based

It directly contributes

nium

produce

of

nitrogen

nitrogen

the

ammo

Legume

fixatmospheric

nitro-

simiiar

compoimds

to the

bacteriapresent in the fbrm of noodles in their roots. These produced nitroif used by the crop itself, gen products are directl,v, to the ammonium or nitrate in excess it contriblltes chemical

of

cycle

fertilizers by some

the

nitrogen nitrogen

contributes

nitrogen

by

mainly

water and

that

itis necpollution at first the nitrogen eycle. Nitrateis a essary to uriderstand found inthe soil and used form of nitrogen commonly by plants forbuilding amiiio acids, DNA and proteins. Nitrate is commonly produced by the chem-

organic

component

muspheric

3.1 Nitrogen cycle [[bunderstand the nitrate

are:

processes of nitrogen

ning,

part

3 Nitrate

a

(NHt)

(N03-)ion, The

izcr to the

Objective

as

of

1) atmospheric

Africa,

worldwide

In N2.

gas, thc plants and other organisms nitrogen in this form. Most of them in the form of ammonium ion exists

legurnecrops, 3) nitrogen fixation by livingbacteria, 4) chernical fertilizcr, and 5) Organic matter. Atrnospheric to iiitric oxide (NO)by lightgaseous N2 fixes

(2001) (1983)

in West (1997)

largest

matter.

fixand denitrificadecomposition,nitrification tion. The fistmain step of nitrogen cycle is the nitrogen fixation, i.e., changiiig to gaseous nitrogen in soil are: solid form, Sources of solid nitr(}geii

Some Islandsof Ok-

Marcel

nitrate

soil organic

ation,

in Ontario,UK, and Halwani et al. in Lebanon. The aforernentioned literatures isa indicatethat groulldwaternitrate contamination Lampinan

nitrogen

and

main

inawa, Japan are potentially contaminated from nitrate. Thind and Kansal observed nitrate contamination in Ludhiana,India,Thorsen et al. in South in Jutland,Denmark, Heatsoi]et al.

(2001)

use

The seeond

nitrogen.

is the nitrogen

most

use

monium

(Japan

of

contains

atmosphere

nitrogen

areas,

iiimany

ot' nitrogen

cannot

it has reached or even exceeded the unacceptable in N03-N. The levelfbr drinkingwater, 10 mglL .JapaneseEnvironrnentalAgency showed that 5.691･ (173of 3,374)tested wells and 4.7% (64of 1,362) water excecded the stanwells used for drinkillg Environmental Agency, dard level in 1999 2000). The highestconcentration of nitrate in the wells

volume

However,

(Ball

of

of

of air the

shows

velopment

source source

ions).

report

from Figur'c1 that nitrogen can exdifferent forms, The largest nitrogen isfound in the atmosphere, 78%

It is evident ist in soil zene

cycle.

cy. cle.

Living bacteria fixes at-

(NH3)

to produce the ammonia to the organic-N component

The

secoiid

main

step

is the decomposition.Manure,

of

of

the

nitrogen

municipal disleaflitter, etc.

crop residues, dead roots to organic decompose at dfferentrates and change matter contains organic nitrogen in matter. Organic residues arc decommany different forms. Organie is fraction, which posed to produce active organic

posal,

fVOL,8 NO.2 2003

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Fignre 1: The

nitrogen

cyclc

showing

the important part of the organic matter significant

cation

condition,

nitrogen

exchange

capacity.

major

since

Under

processes of nitrate transformatien

it has

natural

by lightningand legume fixation

issignificantly lower than that by livingbactere nitrogen produced from organic matter, leaseof nitrate from the organic nitrogen isslow and the overall gainand lossof nitrogen within the nitroDisturbaiices occur when cycle is in equilibrium. gen sigartificial supply of fertilizers and waste disposals

crops ria

and

cycle, nificantlycontribute nitrate to the nitrogen This is becairse fertilizers contribute NHt and N03almost halfof the steps of the ionsafter bypassing of the nitrogen cycle, which causes non-equilibrium system. Waste disposal,in small quantities, can be absorbed intonatural system, but in largequantities it can corrtribute significant amount of nitrate

Final product of Organic-N (NH3),Living bacteriathat fixes nitrogen alsocontributes in this part. Ammonia is transfbrmed to NH4+ ioiiby the processcalled mineralization. Other contributors such as chemical fertilizerand legume crop can coiitribute NHt in this with part. A portion of these total NH4+ ionsincludes the NHt ions produced back from the N03- ionsby some specialized bacteria and then turn back to NH3. This process is called immobilization. However, this Flrrom process is temporary and not so significant. to the

nitrogell

cycle.

is the arnmonia

the

rest

ammonia

NH4+

a

part

can

loss to the

atmosphere

(NH3)gas by the process called

as

volatiliza-

called miThis processis sometimes reduces the chance fixation, which significantly celle leaching to the groundwater, Amof ammonium monium is released from the colloids by the way of cation exchange. When released, most of the ammonium isoften chemically altered into nitrite (NOi) by Nitrosomonas bacteria,Furthermodificatioii by converts the nitrite to nitrate Nitrobacterbacteria oxBoth of these processes involve chemical (N03-), is the idation and are known as nitrification, which third main step of nitrogen cycle. Plantsdo not take nitrite (N02-) becauseit istoxic forthem; possibility leaching is also very low since itis of nitrite (N02-) not water soluble, On the other hand, nitrate (NOi) isthe convenient form of nitrogen forplant uptake, nitrate can easily leachintogroundand any excess soluble. Therefbre,one water since it is very water way of the nitrate nitrogen lossis the leaching,Surfacerunoff also carries some nitrate and other nutrients from the top soil to the lakesand streams causing eutrophication problem. Nitrogen can be lost nitrate a unfrom by process called denitrification and this is the der certain environmental condition, main nitrogen cycle. If some fourthand last step of NHt leachesto the groundwater,itcan alsotake part in nitrification and denitrification processes depending on the environment of the saturated zoiie. When soil pore spaces are fi11ed with water, there are small rooms fbroxygen to penetrate. This process is comsoil

colloids.

tion. R)r high temperature and high soil pH, rate is high. Net NHt ions after immoof volatilization

mon

bilization and

In thisaJiaerobic

voiatilization

are

ready

to contribute

to the plant. However, plants take only small concentration of NHt through their roots, because large concentration of NH4+ is toxic forthem. Nitrogen in the fbrm of NH4+ can be absorbed onto the surface of clay has particle in the soil. The ion of ammonium a positive molecular charge that is normally held by

leaching

and

and

in clay they

reduces

soil, are

nitrate

(N20)gas,

and

soil

where

fi11edwith condition,

into

pore

water

are

without

(N2) or

nitrous

CAI-CHMENT

oxide

fbr their respiraby the Heterotrophic out

tion. When nitritc is reduced bacteria, it is converted into nitric oxide All of these gases then diffuse into the thus completing the nitrogen cycle.

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tiny

very

rnovement.

Heterotrophic bacteria

nitrogen

is taken

oxygen

spaces

(NO)gas. atmosphere,

ieer3e\yl

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3.2 Sources of soil nitrate It can be seen from Figure1 that the illdirect soitrces of

soil

nitrate

freeliviiig at,iiiospheric

are

fixationbacteria, crop ter,

inanure,

intoorganie

nitrogen

dead

residues,

disposal, etc.

waste

inatter,

the

contribute organic

iiiat-

to the soil through differentprocesses wit}i t,hehe}p uf bacteria aiid rnicroorga,nisins. This is the natural process. Differellt, ter

ukiinately

eontribute

anthrupogenic

sources

"itrate

such

fertilizers, septic

tank

potential sources

of nitrate

as

chemical

are

the

(Hallberg

contamination

Kecncy, 1993),Chemical fertilizers direc:tl.v contribute nitrate to the soil. Legume crops also rnay have directcffect on nitrate. Nitrogc,n is also found in geologic deposits. Organic materials in ligniteand bituminouscoal, clan and caliche soils, marine shales, and to nitrogen and ammoplaya lakesare converted nia, which may, be thc primar}, source of nitrate. alld

-Thich

causes

nitrate

et al. Oeiieina

reaches

peint

a

where

itcannet

hold

soluble,

effle(/'tsalso.

4 Causes of nitrate contamination Potentia] sources of iiitrate and causes of llitrat,e con),tany literatures show t'imination are inter-related, sources cause Lhat mainly anthropogenic greundwaHalwalli et al. C1999) ter nitrate contamination, that

groulldwater

nitrate

cont,amination

ofthe

Leballon isdue to the overAkkar plain in iiorthern resultiiig in the application of excess nifertilization, trogen. They found that 14 out of the 15 wells had a

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OF RAINWNER

CAFCHMENT

SYSTEMS

and

arrirnoniuni

in

a

sandst.one

aquifer

(1998)

at.

water

3.4 Nitrate contamination in drinking water exXVhen concentration of nitrate ceeds soine standarcl liillit (tobe discussedlatcr),it called niLrat･e aff'ects healthof huTnan and aiiimals, Excess nitrate, has environcontaniination of water.

stated

pellution iu

studied iiitrate (]996) pollutie" ef grou"din iiorthern C･hiiia, where ther(ihas been a drarr}aticinc,reasein ijitrogeii ftrtilizer usage siiice et

because it is attached to the soil and resists rr}ovement with swater. The tbrces that cause ammonium to attach to the soil are somewhat, likethe forcesthat cause inetal objects to become attached to a inagnet. Nitrate (NOi)leachcsto the groundwat,er easily bcwit･h the soil surface and it cause it is not attached

mental

at.

attributed iiitrate pollut･ionof in the Netherlands to agricttltural acgroundwaLer tivity,mainly fertilizer and livestock manure. Zhang

water. This happens becausethe air spaces between seil particlesbeceme fi11ecl with water, As these air spaces fi11, causes water to move gravtty down through the soil profile,As water moves down throughthe soil, nitrogen can be carried with it. This iscalled leaching. Nitrite (NOi) forinof riitrogen geTierallydoes iiot leach,becauseitisnot water suluble. Unlikenit/rate the arrimonium (N03-), (NH4) fornidoes not leach

water

nitrate

beiieathNottiiighaiii, Eiigla,nd. The coiitaininat･ioii origiiiated froinfttrti}izer and soil organic nitrogeii.

anymore

isve,ry

reviewed

France,Gerrnany., The Net,hcrlands and England). They docurriented high iiitrate lei,els, above 50 ing!L nitratc, beneathagricnltural landsand groundwaterrecharge areas. Fcrtilizationand livestock iiianure wcrc principal sourccs of the nitrate in .ff.rouiidwater. Bernhard et al. (1992) als() documented nitrate pollution in Fhrance.Thc problem fol]owed conversion of land use fronigrasslands to intensive cultivation of Similarl,y, Rivers et al. (1996) identig.rain corn.

Killpackand Buchholz (1993) gave a good description of nitrate leachingto groundwater, whtch isas follows:when soil becomes excessively wet through soil

Strebelet

contarninatioll.

(I989) O991) Europe (including Belgium, Denmark, Fried

fied nitrate

the

of ni-

,Japan

3.3 Nitrate leaching

rainfa11,

(internis

rnglL

ions), wlt.h a rn,axiinuni of 163 rrig/L. EnAgency (2000) stated that nitrat･e concentration in groundwater in Japan has increa$ed steadily due to the developinent of intensive agriculture. Albertsand Spoiner(1985) stated that about two-third of the nitrate iiitrogeii below the root zone could be attributed to nitregen fertilizer sourc;es, amd

nitrogen-rich

industrialwastes

and

50

above

vironinent･al

leaf lit-

roots,

con{/entration

trate

nitrogen

"rhich

and

iiitrate

1980, High concei}trations, up to 3()Oing!L nitrate wcre reported, On the Africari content, Las.crstedt･ et al. (1994) reported nitrate in grouiidwaterof eastcrn BoLswana. Deep leaching fi/orii pit latriiiescaused Faillat reportecl nitrate the contaniinatioii, (1990) of beneath a deft)rested contarriinat･ioii grouMdwater region of the k,oryCoast that was converted to croplan(i.In the Dv,liddle East, fertilizer alld sewage cffluent, used forirrigatienhas containinatcd shallow greundwater in Israel{Ronenand ),Iagaritz,1985). survc,,x,,cd nitrate Kaearogluand Guna.v(1997) pollu{/'ointion in an alluvial aquifer beneath the urba]i Titrkey.Septictank and eonLaniplex of Eskisehir, inat,ed "rater frornthe Persuk l{iverwere prin('ipaJ nitrate sources. High nit,rate levelsiu grc)undwater Australia (Dillon have also beellfbund iiisouthern et al., 1991) and New Zealand (Burdeii, 1982).Prinin those couiitries includefercipal Tiitrate sources tilizerapplied to pastures a"d wast,c froinlivestock, Iiic:ontest of Lhe USA, in Sta[Forclcounty of Kansas 42 wc,11s, ingroundwater samples werc takeri ft'o]n and shalio-, and cluding deep (irrigation) (domestic Nitrate-N coiicenLrations oi' sampled froin 1.3 to 1:S.3ing/]. with a inean Young, 199,5). Fert,iltmd of 5.4 mglL reasons of izer aiid livestock inanure "･'ere tlie inain contaminal,jon, IiiSussex Coimty, Delaware 199293 data froin1,300 private wells showed that 259(, Prot,ectioiiAgc,nc.y) exceeded EPA (Envirenmental stock) wells

wells.

ranged

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standard zie

et

10

of nitrate concentration,

al.,

1995). Poultry

(Macken-

mg/L

was

manure

the main

rea-

(2000)

of pollutioii. Samuel et al. mentioned that groundwater nitrate contamination in Illinois is due to the naturally occurring organic matter. Fertilizerand livestock manure were the sourccs of contamination in [[lexas arid Maidment, 1995) and fertilizer was the main source in West Virginia son

(Thomas

2003), When (Bhumbla, high concentration

a

natural

of

nitrate

sources

contribute

the groundwater,

to

disturbaiice, Oiieexample of this ist･heeffect of forestedareas on the leachingof nitrate to the groundwater.Natural, mature forestsconserve nitrogen but human disturbances can leadto nitrate pollution of the groundwatcr. IIowever, while this is a potential pr()bleinfor a very, smal1 source groundwater,forestsrepresent it isimsually

of

nitrogen

as a result of anthropogenic

to

compared

Keeney, 1993). Table 1 summaries

the

(Hallbcrg and

agriculture

causes

groundwater ni-

of

in different regions of the world. Itisevident from Tkiblc1 that anthropogenic sources, mainly due to application of excess nitrogen-based fertilizer to the agricultural fields,livestock manure,

hemoglobiridue to immaturity of certairi enzymes, and that the kidneys of infants have inferiorexcretory power which may favor retention of nitrite for longerperiods oftime. Comly (1987) mentioned that infants below 6 months in age are more smsceptible to nitrate. Young anirnals are also more siisceptible to t･hetoxie effects of nitrate. In addition, cows, sheep alld horsesbut not chicken or hogs,are sen$itive to high levels of nitrate becausc of the characteristics of their digestive systems. Nitrate toxicity is not normally a problem foradults or grown animals due to the rapicl absorption and disposalof nitrate in the mature digestivesystem. Some reports say that the additional

effects

of

of nitrosamines

nitrate

which

(1956)

Barnes

stated

ever,

recent

isno

evidence

Magee

that

nitrate is thought to be

in humans

exposurc

is formatioii

nitrite

cause cancer.

fbrsorne fbrms of guideline of WHO fbran association

responsible

nitrate

and

may

cancer

in adult.

(1998)

and

says

How-

that there

betweennitrite the

risk

and

and

of cancer.

trate contamination

and

septic

imcontrolled

tanks, cause

nitrate

contam-

ination. 5 Efft]ctsof 5.1 Health

nitrate

efR]cts

Nitratebecomos water

centaining

NN'hen

nitrate

nitrite

in the

contamination

humans high levels of

toxic to

and nitrate

animals

when

is ingested.

is consumed. ' it can be converted to digestive tract and a medica] condition

known as methaemoglobinemia or blue baby syndrorne can occur, Therefore,actually nitrate does not directlyafft]ct health. It is the nitrite that atL foc:ts health, Onc nitrite molecule reacts wit･h two molecules of hemoglobin to form methacmoglobin. In acid mediums, such as the stomach, the reactioiioceurs quiterapidly. This altered formof blood protein prevents thc blood cells froriiabsorbing oxy-

leadsto slow sufft)cation, particularly of gen whieh the infantswhich may lead to death (Gustafson, 1993; Finley, 1990). Because of the oxygen deprivation, the infant will often take on a blue or purhence named ple tingein the lipsand extremities, blue baby syndrome 1987). Other signs of (Cornly., infant rnethaemoglobinemia are g'astrointestinal disturbaiices, sueh as vomiting and diarrhea. Comly cited several factorsthat make infants more (1987) susceptible to nitrate compounds than aduits. The isthat infantspossess much less oxprimary reason idizable heinoglobin t,han adults, so a greater percentage of their hemoglobin isconverted to methemoglobin which greatly decreasesthe blood ability to carry oxygen, Other possible reasons are that nitrite ion may be more strongly bound by infantile 's

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5.2 Environmental Nitrate contaniination

effects

also has harmful effects in the The primary effeet is the killing of fish and other aquatic life. Whcn rivers and lakesbecome contarninated, algae start to bloom. When the algae die,the oxygen is sucked out of the water, ki]ling Lhe aquatic life. One of the primary examples of this is the Gulf of Mexico shrimp industrywhich has feltthe detrimentaleffects of nitrate eontamination fre' m nitrogen fertilizer runoff in the Midwest (Miller,

environment,

1999).

5.3 Guidelines set (1998)

WHO

the guideline for maximum conin drinking water as 50 mglL (asnitrate ion, if converted as nitrate nitrogen it is 11.3mglL) on the basisof methaemoglobinemia in infants,The European Community Nitrate Directivefollowsthe same guideline 1991). centration

of

nitrate

(EC) (CEC,

The U.S, EPA has established a drinking-water standard ot' 10 mg/L nitrate as nitrogen nitrate ion (a$ it is 44.27 mg/L) Environmental Protection (U.S. Agency,1995),Japan Environmental Agency (JEA) also has the samc as the EPA standard of 10 mglL iiitrate

as

nitrogen

in drinking

water

(WaterQual-

ityBureau, 1983). Nitrate concentrations in natural ground waters are usually lessthan 2 mg/L (Mueller et al., 1995). surhendealingwith nitrate concentration, it is important to look at whether the concentration isexpressed in terrnsof nitrate ion or nitrate nitrogen,

6 Factors

affecting groundwater tamination According to [[bwnsendand Ybung and

Buchholz (1994) and Haller et

tors affecting

OF RAINWMER

groundwater

CAI'CHMENT

nitratc

nitrate

con-

Killpac:k (1995), al. fac(2003),

contamination

are


Japan Rainwater Catchment Systems JapanRainwaterCatchmentSystemsAssociation{JRCSA)

[Rible1: Main

Association (JRCSA)

eauses

of

groundwater

Main

Regions Asia Japan Northern China Europe Belgium

nitrate

causesof

in different regions

contaminatien

Delaware

Illiiiois Middle

et Strebel

Fertilizer and livestock manure Fertilizer Fertilizer and livestock maiiure PoultryinaJiure NatuTalsoil organic matter

Bhumbla (2003) Townsend and Ybung (1995) Thoinas and Maidment (1995)

Over fertilization R]rtilizer and sewage Septictank

Halwani et al. (1999) Ronen and Magaritz C1985) Kacaroglu aiid Gunay (1997)

Rivers

Samuei

eMuellt

and baeteria ¢

and

soil aerobic

soil

temperature,

pH and EC land 3) Land factors:

pattern and topograp!ry factors:type of crops and growing 4) Agricultural apand time of fertilizer seasons; type, amount irriand time of plication;and amount, method use

gation application 5) Hydrologicalfactors:distanceto groundwater and discharging table; recharge ratel recharging effective area; hydraulicconductivity, porosity and bedrock and sorption of surface, sub-surface soils; and water pH, Eh, EC and temperature 6) Geologicalfactors:type of the materials present aJid bedrock soils; thickin surface, sub-surface and thickness and location ness of the aquifer; of clay iayer

20NJOURNAL

et al.

(1995)

(2000)

et aL

Dillonet

microorganisms;

condition;

(1998)

(1996)

waste fertilizer and livestock Flertilizer and livestock waste

1) Environmental factors:rainfall; evaporation; temperature; sun shine hours; and presentof nitrogen gas in the atmosphere and moisture 2) Soilfactors: soil texture, structure content; denholdingcapacity; organic matter anaerobi

al.

Lagerstedtet at. (1994) Riillant, (1990)

natural factors,which ase associated with prozone within ducing highernitrate in the subsurface with the nitrogen ¢ ycle and other factorsassociated agriculture, hydrology and geology. These can be categorized into the fo11owing seven groups:

and

at.

Pit latrines Defbrestation

the

sity of

et

Mackenzie

Africa

EasternBotswana IvoryCoast Australia Southern Australia New Zealand

al.

Strebei Strebelet Strebclet al. Oenema et al. et

East

Lebanon Israel Mrkey

Eried (1991) (1989), Ried (1991) (1989), Ried (1991) at. (1989), Ried (1991) (1989),

Fle]rtilizer and livcstock manure Fertilizer and livestock manure Fertilizerand livestock manure and livestock manure Fertilizer Livestockmanure Plertilizer and soil organic mattcr

USA

West Virgmla Kaiisas [Ikexas

world

Japan Env. Agency(2000) Zhang et al. (1996)

fertilizer

Germaiiy France The Netherlands England

the

contaminationReferences

Intensiveagriculture

Denrnark

of

OF RAINWAT-ER CAg-CHMENT

SYSTEMS

Burdcn

al.

(1991)

(1982)

7) Other factors: densityof irrigation we]ls; irrigation return flows,and floodflows A

climate

with

rainfa11

exceeding

evapo-transpi-

leads to the movement of rainwater to that more recharge. Any exgroundwater produces cess nitratesthat are present in the groundwaterto the groundwater. High recharge zone are carried shine hours favoratmospheric temperature and sun ration

nitrogeii

often

fixation by lightning.

cannot hold water for Loose-textured soil (sandy) longertime. W}iter from such low moistureholding rapidly to the dowiiward,thusincapacity soil moves creasiiig the chance of nitrate leaching.Soilorganic niatter, temperature, EC, pH, densityof microorganeonditioii control the niisinsand aerobic-anaerobic rate. nitrate trificatioii rate that controls prodllction

A land regularly used foragricultllre needs to bc and increases the chance of nifertilized frequently, trate pellution. Area having the higher density of waste disposalalso faces high risk of nitrate pollut,hereis the tion. If topography of the land is fiat, and high recharge, possibilityof having low runoff will favor nitrate leaching, which Agricultureplays a major role in groundwater ni-

(2003)

Bhuinbla stated that trate contamination. increasc nitrate leaching are to crops that are likely have requirement, those that have a high nitrogen

AfOL8

NO.2 2003 NII-Electronic NII-Electronic

Library Service



If as well as on depth to groundwater. depth to is shallow and the underlygreenhouse groundwater crops are more likely ing soil is sandy, the potential fornitrate to enter crops, orchards, atid vegetable high.However, ifdepth to to receive high application rates of nitrogen fertiliz- groundwater isrelatively is deep and the underlying soil isheavy ers. Any excess nitrogen that is not used by plants groundwater may become a source of pollution. Nitrateleaehing clay, nitrate will not }ikely enter groundwater. In from fertilizer use depends on whether it is amm} soine cases where dense hardpaiisare present, nibe greater trate leachingwill not progress beyond the depth of niacal, nitrate or organic. Leaching may nitrate fertilizer is used, Nitrate losses are the hardpan (Killpack and Buchholz, 1994),Therewhen a in fore, management of nitrate eontamination should be likely to be more when all the nitrogen isapplied vulnerability that determines one application compared to when it is applied in on the basisof aquifer sourees on split applications. Fallapplication causes high nieffects of different groundwater nitrate trate losses. Irrigation also enhances nitrate leachcontamination. Pbr assessing nitrate vuliierability of nitrate are ing.Flirequent fioodirrigation will cause more groundwater aquifers, generally two approaches InformationSystems (GIS) leachingcompared to the regulated sprinkler irrigafbllowed: a) Geographic high economic

trogen

value,

or

High-value

use.

tend to be ineMcientin nicrops

such

tion.

Shorterthe distancefrom the ground surfaces to of nitrate leaching. the water table, higherthe change High hydraulicconductivity of thevadoze zone transof fersnitrate to the groundwatertable quickly. [[tsrpe aquifer material and porosity are alsoimportantfactors forgroundwater nitrate contamination. Karsts having macro is more susceptible to aquifer pores nitrate contamination than alluvial aquifer. Aley stated (1977)

is most

that transport through

pores

macro

during precipitation events and fivetimes as much to groundwater recharge as rnatrix fiow.Groundwater temperature, pH, Eh and EC hErveeffect oii t･herate of denitrification from the saturated zone which controls final of nitrate in groundwater. concentration Locationand thickness of clay material play important roles in controlling groundwater nitrate pollution.A dense clay layerbelow the soil moisture zone can resist potential movement of nitrate to the can

significant

contribute

groundwater.

Irrigation return flowsand floodfiowsmay fecton nitrate pollution. They can enhance

have efi the

rate

from the unsaturated zone to if nitrate in thegroundwater, excess exists theunsaturated zone. [[bwnscnd and Ybung fbund sigof

nitrate

conditions,

as

movement

(1995)

positivecorrelation between densityof irrigationwells and grouiidwaternitrate concentratioiis. nificant-

b) Statisticalapproach.

approach

and

7.1 GIS

approach

ability

to

assessing

nitrate

vulner-

of aquifers

Mackenzie et al. (1995) and Bernard et al. (1998), Bal1 and McDonald (2001) used GIS approach for assessing nitrate vulnerability of the United States, Sussex county of Delaware and Scotland,respectively,

Ball

where

and

McDonald

presented (2001)

The steps associated detailsof the methodology. assessing nitrate vulnerability with GIS approach for of aquifer are shown in Figure 2, which is the coinfrom the aforementioned pilation of such methods literatures. Figure 2 shows that GIS approach fbr vulnerability assessment is on the basisof some potential maps, which are digitalized and combined. The approach of showing potentialityof a particular parameter that contributes groundwater nitrate contaminatioii islittle biteasicr, becausein most of the cases itisvery dificultto determinethe actual parameter value,

such

as

estimating

load,groundwater

nitrogen

Each parameter is sub-divided in some classes, and then effects of twu parameters are comrecharge

etc,

bined. Figure 3 is an example of combing nitrogen loarlpotential map and groundwater recharge potential map to get nitrate risk potential map. Thc key of nitrate leachingrisk potential ison the basisthat any one of load potential or recharge potenis low, leachingrisk will be low. E]om the rest, when any one of loadpotential or recharge potential is medium, leaching risk will be medium. The leachwhen

7 Assessment

of

nitrate

of aqui-

vulnerability

fersNitrate nerability

sess

in groundwater generallyfbllows the vulor risk map. So,it is important to as-

groundwater nitrate

vulnerability

beforegoing

to take any remedial action. Nitratevulnerability of groundwater refers the degree of nitrate contamination potential in different zones of the aquifer. In an aquifer region, nitrate leaching potential in different zones would be differentdue to varying natural, environmental

and

man-made

causes.

However, whether

to leach downwards from a high leachingpotential zone and rcaches into the groundnitrate

water

continues

depends

on

underlying

soil and/or

bedrock

JOURNAL

tial

ing risk

be high if both of Ioad potential and potential are high. Here, forthe classification of nitrogen loadpotential and recharge potential as high,medium, low (or any other classes) from the observations, fieldexperience is applied. If any two of the adjacent classes of input of any parameter are statically insignificant, then their respective adjacent will

recharge

be statically iiisignificant, R]r exlow classes ef nitrogen load postatically insignificant, then medium and of nitrate leachingrisk potential may be

output

classes

ample,

ifmedium

tential are

low classes

OF RAINWAJ-ER

may

CAT-CHMENT

and

SYSTEMS

IVOL,8 NO.2 2003M21


Library Service


Association (JRCSA)

II Fllilllllii'ilii,lli lliii l illll .urtmtc I,t""ty.yhlLi/t.1g.'el/tg)tlLl/.h

Sub

i

'"'

r

SoKdV-･.ltLl,

-]l,/te･h//1./L//./ 'liil;';.L,i:kl,z,1i･`

,ablt/k/,/ttt///t/M-S'/

?::1/1

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ul rtsk

,!mt xt/lnt/ah/1/t.t. pt,dtFn/al

ltLn/lt',//tg,ut-tL///tt//be/zat,"/ton/h///t/i Ftt./Ft,t//tdg/t-i//J",//tt////.ra/t,////,e///t,///////,

:]/t/7/but///n//f]t/Tt.tTt"tntt/t/t,//////t///L.tttu//t]tt,//t'

Figure 2:Flow

chart

of

the GIS

approach

of

assessing

nitrate

vulnerability

()f aquifer

Figure. 3: Description of nitrate leac:hingrisk potentia} rnatrix basecloll nitrogen ]oad potential and groundwater recharge potenLial

differentparainct Siinilarl},

statically insignificant･. ters are (llassified and maps

to

assess

iiitrate

nitrate

combined

assess

nitrate

coiicentrations

are

nitrate

two

defined

the

shows

forthe

conc,eiitrations

inaps as

into is shown risk

different areas foliows:

and

GIS fbrBoarders, dist,ribution of same a,rea, In these classes

are

and

very

E )･Ioderatelyvuliierablc aquifc,rs + Moderhigh nitrate leaching'potential

Class 1 Local

cathments

associated

Class 2 I]ocalcatchllients includingArea B CIass 3 The

A Highly vulnerab]e aquifers + High and very high llitrate leachingpoteiitial Area B Highly vulnerabie aquifers + Moderately high r!itrate leachingpoteiitial

It caii be

Area C Moderately very high nitrate

>

22 asJOURNAL

t High

wit,h

Area A

upland

additional

portion

of

c;lass

to

1

1 when

class

and

2

catch-

IrlelltS

Area

vulnerable

aquifers

leaching potential

and

act,ual

catctrnent

vulnerability

nitrate

ately

classified

prepare(i using

map

Figure 5 Scot･laiid.

high Area

vulnerability

t,hreedifferentgroups. Suminary, sta,tistics in Table 2, Figure 4 shows the c,ombined vulnerability

Area D Low

GIS

using

of aquifer.

vulncrability

In EasternScotlancl te of aquife.rs

are

aquifers

t High

and

strong' currence.

is > 50

frorri Figures4 arid 5 that there is a relationship between Iand use and aquiktr c)c679/ of sources in C]ass1 ancl 2 catchiTients seen

mgfL

;-)O rnglL

nitrate,

169L

of sources

in elsewhere

is

nitrate.

leaching potential

OF RAINWNER

CAI'CHMENT

SYSTEMS AfOL.8NO.2 2003 NII-Electronic Library Service


Association (JRCSA)

RiskAreasSurfacevvetercatehments S7coO

RAreaA EI]AreaB

X'vlh"

[]clessA []cdess2 NC4ass3 DAreac =]AreaDfiSlglgeAreaE

tt 'x'

rm m

t-

x"""ti

tt'''Atttvtl)Etl'

NorthSee Eyemtr

L"S

66000 .-fi.x:e.'x' y,t-xbt

'sgttttttt'ttzz'tsttstlit V.v =.tN#x.' "s't{xt{t-,c,x."t..xs."s{t'F' :"Gfib"Sditr.vv･...-lnyk ImMtri .q' -' .s.x.t')kK.(.,..3 am ''f' " '""vpt''{-,'gS-f-sS}:.'s`tsx}dr. E"gle"d nvgv'tt..xxt'ttv C>..:I ,'-tNtZ.,:L.Ltiv.' (t"1tt)t...r.',KKE.ig..'t.Ii-.the"}tt"'-tK

NFX

esoe

sN+s-ye

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± tt+ "!tktifttt"tLttH

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---Lh

exufjecthufpt,'

'+vx

i

eteooo

tlux'h tstttt'tt'

'.l"tvt

6ooeo 3toeee32eeeo33ooOO3400003seoeo3600003700003eoeeo3ecooD4000co

Figure4Combined

risk

(aftcr

Ball and

L

6rccoe

e.-+ltSV-h.Olobt"

dnd

zones

vuinerabihty

McDonald

(2001))

Nntate(mglL)Surfecewatercatchments 05 y.i"svCIass"

;2So24eeMclass2

ecosoMCtass3 t}50

ssoeco

hNa"

t

"

'.tttht

.e''

".

..rS's"f"t"4.

htx"hvtVttt''',l.1'tAnerteitbetg{,S.'."-."t oc-'tOg.'key.bMv'

ktL--",ffvl-''

\

.Lyt"h{`,.etttl'tt

'k-"xlki/)1･i･beg...sr.vtht-tc.v.

x"i."

,

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hsi

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teg

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t

i,,/k-.gk

--t)tltttKSl. "

t"x HIEt:-ili'･iiM as',gv,,t$,,irl･i,:..gt.i,.,,･si/.,/1.I eb･.e"vt4eu)titXtt-ttii p tt"".r.tttlv'tt '/gkll.i,.i,w...y.

tctt'i"-.'MttLL

'jt-ttt-xtitt

"i'',p"eqE..{.e,.,

"'of.eta/"

.g

S200x'

t

'

t'ut"litv-"rk.'it..,l.-,ir,xxNs' ha

't")c.k..,su...yx.ho

6tti".;.a.

Gsoeeo'''

e3ooco-tl

forthe Boardes,Scotland

catehments

O-.l.VX".xt

t"ttn"eut"-

/ttt'

associated

Appmxborltdnnyetonliting .-vhrgeFehd4url.".Nvt ' ttSvtV

-:1'Eas

'thlttLG

and

'

''".t"'t`,'":t.s･.?ss･g.'.xkr.

tt>)'LhXr"

Vtx,S.is?2..-.

.Spt:twEiiiiXvNX.I"vJL"t 6teooo

H-tetigxhh

x)

'x

{?llt -

M-s

rm

-mt"

tSt-v･tc{ltvxL

soeco 3toeoo32oooe33oooo34oooe3

Figure5Nitrate

data and

36oooe37oooo3scooe39oooo400ooO

edtchments

fbrthe Borders,Scotland(after Ball and

JOURNALOF

RAINWATER CNCHMENT

McDonald(2001))

SYSTEMS

tVOL 8 NO 2 2003g23


Library Service



Table 2: Summary. statistics fbrnitratc data from highlyvulnerable

(after

in Eastern Scotland

NitrateLeaching High or

No

(2001))

McDonald

and

aquifers

(mglL)

of

data pointsNitrate 25 percentileMediaii 75 percentile 5494558706 292633.2 46,5 59.558.533 46 1015.6

High

very

Ball

Moderate}y High Moderate or Low

All

44

approach Statistical

7.2

Townselld and

Ytmng

(1995)

rnent

used

ing'nitrate

to

assessing

nitrate

a

statistical

Evans

Maid-

and

forassess-

approach

groundwater for Kansas

of

[fexasof the United States,respectively. In approach, faetorsassociated with groundwater vulnerability of nitrate containination are dctermined by the te$t of significaiice,. Finall.yusing all the identified factors.a regression inodel that describesthe grouiidwater nit･rate concentration is and

statistieal

inade,

if possible. Once the

is rnade,

model

it ceuld

be used to control of nitrate pollution. Z[t}wnsend and Ydiing (1995) conducted statistical tests on a varithat rr}ight･ affect or control nitrateN c;oncentrations in groundwater of Kansas. Indeincluded well type, depth of well, variables pendent depth to watcr, depth below water table,clay thickness above the screen, irrigation-welldensit,y, , irrigasoil texture, Nonparametric st･atistion pract･ice and tics were used because of the small number of samof the distribution of many ples and the non-norinal U test wa$ used parameters. The Mann-Whimey collcentrato test the hypothesisthat the nitrate-N depth tions of twe subgroups of a variable of well < 18 m (60ft)and depth of well ) 18 m ft)]were drawn from the same population. This hypothesiswas rejected ifthe calculated probability vakue was lessthan O.IO. Iiiother worcls, the subgroups of the variable were cletermined to be sigand occurrence of nitrat,cnificant in the distribution et.y of variables

lexample:

(60

(p)

N

The Spearinancorreiation

cencentration.

sis was

cal

to detcrminewhether

ttsed

relationship$

concentrations

The Spearman

(,,xit and

observed

aforementioned

nitrate-N variabies.

coeMcient

corre}ation

analy-

definable statisti-

between the

several

r.

shows

the

of the relationship the p value shows is positive er negative; regression the sigiiificance levclfort,hetest. Multiple or rnethods were used to definea prcdictive equation Statistical model based on all available information. aiialyses for the Kaiisasarea indicatedthat sha]low to contamination susceptible groundwater is more than deepcr groulldwater and that lower nitrate-N are concentrations probable in wclls with a greater Irrigationthe well screen. thickness of clay above significant a statistically well densityshowed I)ositive and

$trength tioiiship

correlatioii

with

24 asJOURNAL

nitrate-N

whether

coneentrations

OF RAINWNER

foundto re$u}t frornthe two

CNCHMENT

the

of

rela-

shallow

versus (flood

methods

Nor

difference in nitrate-N

significaiit

trations was

and (1995)

vuhierability

Ne

wells.

of aquifers

vulnerability

center-pivot)

used

concen-

irrigation in the area.

difi)renees in nitrate-N concentrations between sandy aiKi loaJnysoils. They regression modcl that could not findout a defiiiite nitrate coneentration of can describesgroundwat･er Kansas groundwater, The maximurn correlation coeMcient (r2)they follndwas O.30. SimllarlyEvans there

were

rvIaidment thc relationship and

significant

(]995)

liiiearregres$ioii

used

to

assess

between nitrate exceedence probabilities potential indicatorparameters forfivedifferent aquifers of Texas, The dominant parameter was the aquifer from which the sample was drawii. Setting Lhis aside, the

oiiLv

dicatorwas average relation between the tamination

and

the

consistently

annual

rainfall.

in-

sigllificant

No

significant

spa,tial patteriis of nitratc consale

of

nit･rogen

fertilizers was

found. contam8 Simulation of groundwater nitrate ination Simulatien of groundwater iiitrate centamination means

of

(ielineation

nitrate

groundwater fiow forspatial though the

groundwater

aquifer

conceiitrations aiid

nitrate

vulnerability

time

with

dornains, Al-

follow in most of t･he cases a definite correlatien

concentrations

map,

itis veri, diracultto construc;t and betweenVthegroundwaternitrate concentrations This 1irnits aquifer vulnerability poteiitialindicators. management

the

of

aquifers

iiitrate-contaminated

In this situation

map.

vulnerability

using

a simuiation

ro]e. Moreover, it is the can play a major technique to see the long-term effect of cont,amis inatioii.However, groundwater nitrate simulation not straightforward, since the behaviorof nitrogen in soil is known to be complex. Many complicated The fo1processes are involved in nitrate simulation.

rnodel only

lowingsteps

are

associated

with

groundwater

nitrate

simulation:

l) Estimating groundwater recharge, which carries contamination load sources nitrogen loadfroindifferent 2) Estiiiiating nitrate 3) Combining step 1 and 2 forestimating leachingflux steady-state 4) Calibrating and valSdating groundand incorporated nitrate water flow model rnodel

SYSTEMS A/OL,8 NO.2 2003 NII-Electronic Library Service


Catchment Systems Systems Association{JRCSA) Association (JRCSA)

[[1)ble3:Compamison of

datarequirementbetween

NITSand IMPACT

nitrate

transformationmodels

Model Comparison

Model NITS(Birkinshaw and Ewen

Data requirement Initial concentration of nitrate in manure, litter, and humus concentration of carbon in manure, litter, and humus (2000)) pools; Initial Time-varyingfertilizer application rates and pools; Litteradditions; date

of

application;

Timevarying

manure

application

rates

and

date

Livestockdensity;Soil organic matter concentrations; Wet and dry depositionrates of ammonium and nitrate; Carbon concentration; Carbon nitrogen ratio in biomass and humusi dispersion coeficient; Environrnental reductioll factor; EMciency reduction factor; Humufication fraction; DistributioncoeMcient; Degree of satMineraluration; Denitrification factor;Nitratediffusion cunstant; izationrate; Moisture content; Nitricpotential; and Crop type and of application;

IMPACT

(Andrews (1997)) et

al.

growlng season Daily rainfal1; Daily rechargei

Amount, dateand method of Amount, date and method of fertilizerapplication; Percentagedry soils and total N contents; Type, depth,porosity and moisture content of soil; Flow type; Initial concentration of nitrateand ammoniuin; and Crop type and growing season sludge

application;

5) Calibratingand validating transient groundwater flowmodel and incorporated iiitrate model. Fbr each

aforementioned

and all sub-models

veloped

step, a sub-model

isde

aJ/eincorporated together

simulation modeling system. Fifinitedifference method is used in nitrogen simulation model. The most diMcultpart of nitrogen simulation model isthe estimation of nitrate leachingflux.From the nitrogen cycle, we may

to get nite

a

nitrogen

element

or

that many nonlinear and complex processes involved in nitrate transformation, which makes trate leaching fiux inodel complicated. see

are ni-

Birkinshawand Ewen (2000) reviewed models relatedto nitrogen transformation and nitrate leaching: e,g,, ANIMO and Kroes, 1991), (Rljtema DAISY (Hansen, 1990), LEACHN, part of the LEACHM model and Hutson, 1989), (Wagenet SOILN (Johnsson et al,, 1987) and WAVE (Vdnclooster et al., 1995). However, these models are limitedto the crop root zone only, which cannot handle nitrogen transformation in saturated zone. [Ibovercome this limitation, Birkinshaw and Ewen developed a nitrogen transformation model, (2000) NITS, and incorporated in SHETRAN, a 3D river catchment modeling system, which allows nitrogen transformation and transportation in unsaturatedsaturated mediums. Lunn et al. (1996) developed a Nitrogen Modeling System (NMS),which is apin Tyne basin, UK plied for the nitrate simulation iiifourstages: determinationof nitrogen input categories; simulation of plant uptake and decay using the farm management model EPIC; simulation of initialnitrate profilesin the unsaturated zone with the one-dimensional transport model MP; and finally a simulation of nitrate traiisport by the SHETRANUK catchment flow and transportmodeling system.

JOURNALOF

model Thorsen et al. (2001) used DAISY and incorit in MIKE SHE, a 3D distributed catchment porated model, forthe complete simulation of water and nitrate transport in Karup catchment in Jutland,Denmark, Refgaard et al. 0999) al$o used MIKE SHEI nitrate in two largeDAISY coupling forsimulating inscale Danish catchments, Lasserreet al. (1999) corporated AgriFlux,a GIS integrated nitrate transin MODFLOW, a 3D groundwater fiow port model, model, to simulate nitrate contamination, Allof the models abovementioned are physically-based. Only Andrews et al. (1997) used IMPACT, a conceptual vertical nitrate leachingmodel foragricultural

and

sewage

aquifer

of

Heng ple

sludge

and

conceptual

require

in uncoiifined

Nikolaidis(1998) stated models

relatively

ilyaccessible, models

managernent

Chalk

East Anglia, UK.

with

while regard

are

attractive

lessdata, which

that the simbecause they ame usually

eas-

the predictive capability of these of assessing thc impacts of alpractices is questionable due

ternative agricultural to the serni-empirical nature of the process descriptions, On the contrary, a key problem in using the more complex catchment models operationally liesin the generallylargedata requirements prescribed by the developersof such model codes. Let us consider SHETRANI NITS, as an example data requirement forthe physically-based models. Figure 6 shows the schematic diagram of SHETRAN catchment model and Figure 7 shows the nitrogen cycle used in NITS component. Both figuresshow that for simulating nitrate using SHETRAN/ NITS modeling system a lot of processes are involvedthus requiring many input data, The requirement of large input data for the physically-based models limits their actual fieldapplication in many cases. Thble 3 of

RAINWNER

CIvrCHMENT SYSTEMS,4f9gsi NII-Electronic ."tSll

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Fynperatden

Figure 6: Schematicshowing some the Birkinshaw and Ewen (after

Figure 7: The

nitrogen

cycle

as

main

represented

by NITS the ceinparison of data requirement IMPACT modeling technique of nitrate transformation. It can be seen from Table 3 that NITS iiiodel requires many data,which are diMcultto obMIKE SHE! DAISY modeling system has tain. The the similar limitation. shows and

Ichioii et estilnatc

al.

developed (2001) contamination

non-point

a niethodolc)gy.

to

flux(i.c,i., nitrate

leaching)to groundwater as an inverse problem solution by incorporating geneticalgorithm with a $olute transport

ble of

plume sioii

successfully

and

ifobservation and

accurately

only

are some

are

contamination within

capa-

time-

estimating source

ar-

the contamination

hydraulicconductivity

aquifer

coeficient

strated

wells

is indeed

which

model,

leaching fluxesin

varying

cas,

sirnulation

properly. known.

and

disper-

'l'heydemon-

hypotheticalexarnples.

The conbe mseful ifsources

tamination flim,estimated to see the long-termeffect ef coirtamination other agrieulof pollution,their Ioadte the soil and rcmain and hydrological factors tural,environmental in this way,

26 taJOURNAL OF RAINWATER

may

CNCHMENT

processes represellted

(2000))

in SHETRAN

in NITS(after Birkinshawand Ewcn Usuallythe aim

constant.

the

of

(2UOO)) fiuxes-

non-point

in agrit,iinationis to findout the effects of changes cultural praetices aiid the effeetiveness of possible reforexistiiig polluted sitcs, which is medial measures between the leacha relationship done by acquiring either and differentmanagem(,mt indieai,ors ing fltix analyby the modeliiig techniques or by regression ses. Therefore,the leaching fiiixestjmated by the cannot be used as a Ichionet at. (2001) tool forthe protection of groimdwater source, since ithas no from non-point contarninatien indicators. However, relation with the management leachingfiux,estimat･ed in this way, may play an iin-

of

method

management

portant

in

role

9 Remedies

establishing

the relationship

groundwater

of

nitrate

rnodel.

contami-

.

nation

There

are two

ter nitrate

from water

types

of

contamination. and

tamillation in

SYSTEMS AIOL.8 NO.2 2003

another

for the groundwaOne is clean-up of nitrate ispreventionof nitrate conselution

water.


Library Service



isabsent, producingnitroN20). The microbial re(N2, duction of nitrate to gaseous nitrogen products is termed dissimilatory denitrification or nitrate respito be ration. Generallydenitrificationis considered nian anoxic occurring in the of presence process, trate and the absence of oxygen, The process proceeds through a series of four steps, from nitrate to compounds

9.1 Clean-up of nitrate

Halleret

al.

from

mentioned (1993)

water

that in dealingwith

the nitrate problem in subsurface waters, there are two options fbrachieving safe nitrate Ievels. Firstof all there are non-treatment techniques that consist of

blendingdrinkingwater or changing water sources. The second alternative isthe treatmcntprocesses.

els of nitrate

with

to

easy

of

source

(Haller

et at.,

2003).

9.1.2 Tltreatment

The

use

of

change,

and

treatment processes includesion

reverse

chemical

reduction

ex-

biologicaldenitrification

osinosis,

to

actually

portions

remove

the pollutant.

of

Ion

a)

exchange

In the ion exchange substitute

chloride

(Cl-)

-

although Natural biological denitrification occurs, not extensively, in aquifers in which a siifficient organic carbon is present.Wasource of reducing denitrification by ter treatment processes stimulate compounds as iajectionof nutrients. Such organic methanol, methane, and starch or mixtures glucose, of these (e.g., a sugary brewery waste) can be used as carbon sources and Jorgensen, (Halling-Soresen

1993).

Bie-treatmentcan

remove nitrates down to 2-10 total nitrogen (Hiscock et al., 1991),potentiallybelow the typical limitof 10 mglL as nitratereviews related to biological deninitrogen, Some Bruce and Edward trificationof nitrate are: mglL

process,special resins are used to ions forthe nitrate rariical.

and

NitrateNOi -, N02- - NO N20 - N2 NitrogenGas

under-

water with lower levhigherlevelsuntil a safe ifpossiblejustavoid the prob-

waters

or quantity isreached, lern by utilizing another

quite

are

cDcygen

NO

gases.

mtrogen

9.1.1 Non-treatment The noii-treatment sources stand in their logic;combine

when

gen gases

of

This rnethod of nitrate removal requires several steps (2002), the proMichal et al, (2002) and Bruce and Dina (2002). fbrsuccessfu1 decontamination.Essentially, Even though it isan effective nitrate-removal techcess relies on the factthat water solution must be is slow, diMcultto electronically neutral, and therefore by insertinga nelogy, biologieal denitrification Bacteria negative ion, another negative ion can be removed control, and itproducesaJi organic residue. nitrate radiare sensitive to heavy-metalions and to changes in from the water. Besides the negative the composition of the influent stream. cal (N03-), common anions includecations or posid) Cemical reduction tiveionsare calcium, magnesium and sodium (Guter, 1981).b) Detailsof the chemical denitrificationcan be found Reverse osmosis in the homepage of Jacek (2003) including the The phenomenon list of wide literature review. Chemical methods of water flowthrough a semi perineable membrane for decomposing nitrate can be divided into two that blocks the transport of salts nonspecific methods and methods de or other solutes through itisknown as osmosis. Osgroups: mosis isa fundamentaleffect inall biological systems. signed fbr nitrate decomposition,Supercritical war It isapplied to water purificationand desalination, ter oxidation (SCWO) is a nonspecific nitrate waste material treatment, and many other chemical decomposing method based on the use of various oxand biochemicallaboratoryand industrialprocesses. idizers(e.g., oxygen, nitrate and ferric ion)in supercritical water of water: When two water (or other solvent) volumes are sep3740C, 22.9 point (critical MPa arated by a semi permeable membrane, water will water is an excell=218atm]). Supercritical flowfrom the side of low solute concentration, to the lentsolvent forgassesand most organics. Usuallyit side of high solute concentration. The flow may be allows an effective oxidation of organic eompounds stopped, or even reversed by applying external to water and carbon dioxide;semetimes it is necespressure on the side of higherconcentration. In such a sary to add a heterogeneouscatalyst. Inorganic salts case the phenomenon is called reverse osmosis. are almostinsoluble in supercritical water ifthe temc) Biological denitrification perature > 4250C, All phosphorus, chlorine, or sulBiological denitrificationutilizes bacteria to denifur compounds exposed to SCWO are converted into trifyaqueous nitrates in the absence of oxygen. The or sulfates and may be precipphosphates, chlorides, ba teria are heterotrophic(more correctly chem} itated and separated. The SCWO is energy intensive heterotrophic), that require aii energy source either processes and require high pressure. Consequently, in the form of organic carbon, carbon dioxideor the capital expenditures are high. sulpher. These denitrifying bacteriaare a form of Thermal methods of decoinposition can use either £

anaerobic as

electron

respirators acceptors

that

use

for the

nitrate oxidization

andlor of

nitrite organic

JOURNAL

the nitrate disproportionate reaction tion of nitrate by an added reducing

OF RAINWAI-ER

CAI'CHMENT

or

the reduc-

agent.

Dispro-

SYSTEM9 IYRLc't8rpsnQi'c2 NII-Electronic Library Service



portionation cari bc used to decompose solid nitrates, but itdoes produce toxic oxides of nitrogen. But the high tempcratures and pressuresrequired make ther-

dccompositionunattractive.

mal

Low-ternperature, low-prcssure methods of nitrate reduction and are based on electrolytic chernical reactioiis. In the electrocheinical niethods, nitrate is reduced at the cathode. The two generalized half reactlons

arc:

Cathode: 2N03- + 12H+ + 10e' = N2 + 6H20 An()de:2H20 = 2H+ + 02 + 4eThe

real

is more complicated The mechanism and

mechanism

fullyunderstood,

not of

electrochemical

nitrate

depend

reduction

cathode materiall usually a special trocle surface is iiecessary to achieve eMciency

of

The

inost

nitrtlte

to

still

and

eraciency

cata]ytic

high

the

on

elec-

rcduction

nitrogen.

important thing to

notc about thc procedures is that neither of these methods is collipletely effective in removing all the nitrogen from the water. [[lreatment can remove some of thc nitrate, but with varying eth-

clean

abovementioned

ciencies,

inueh

of

which

found in the

stances

up

stated (2003)

Bhumbla

depend

can water

on

other

(Haller et

sub-

2003),

al.,

that incorporationof

afore-

technologics forremoval of nitrates intoa trcatmcnt system could subst･antially increase

into aquifers, terways, animal cals

protection, grassed

wcllhead

management,

waste

nutrient

wa-

man-

have high deirrigation manageinent fbrprotecting groundwater froin greo of effectiveness nitrate centamination. However, groundwater nitrate data obtained from the protected wellhead agement

area may

and

not represent

the actual status of

regional

Therefbre,in additioll groundwater contamination. to wellhead should be given to protection, einphasis managemeiit protect aquifer and as$ociated practices care on proshould be giveiihigh priority. Special tecting wellheat1 froinuitrate contarriination is necessary forthe drinkingwater wells. Reviews on management practices for protecting

et al., groundwater nitrate contamination (Haller 2003; Greg and Robert･,2000; Edward, 2003; and Logan, 1990) show that the followingfivetypes of management be given priority: practiees should

1) Agricultural management

2) Land

managcment

3) Soilinanageinent

4) Irrigation managernent 5) Animal

waste

management･

inentioned water

the

cost

of

treatment.

water

One Califoriiia water

treatmcnt district estimated thatwellhead nitrate-N m3). Thus, cost $375 million per gallons($O.0825 per once an aquifer is contarriinated with nitrate, itwill cost a largeamount of money to use that aquifer as TheTefore, a more a souree of drinkingwater. prunitrate contamination of dent approach isto prevent groundwater. of

in

contaminatiome

nitrate

groundwater of Prevention of groundwater nitrate contarnination a region should be on the basisof the sources and in that region, and factorsthat cause contamination model, i.e,,the correlation between the managernent t,hedifferent management indicators and groundwater nitrate concentration. However, all the associatcd factors cannot, be controlled. A region that faces nitrate coiitamination solely due to the grouiidwater and

natural

Literatures show t･ocontrol. isa nitrate containination

causes

be dificult

would

that in inost man-made

of

the areas

problcm,

which

t,hercfore comes from the introducing is to control the by jt possible problem management appropriate practlces. as havTable 4 shows general practices identilied effect oit ing a positive protectillggroundwaterquality.Eva[Luate each practice fora particulam farm or field. Itis seeii from Table 4 that antibacksiphoii dc}arithropogenic

vices

that

28NJOURNAL

;i

the faet that

an

accurate

r-

estimation

of

net

nitrogen

is very diMcult to determine (Hallberg Keeny, 1993).Therefore,farmersusually apply an excess of nitrogen fertilizcr. If the farmer adds large ainounts of fertilizer in the begiimillg, then he isforcedto use more and more each year. Therefbre, fertilizer should it is important to know how much of be applied on the basisof nitrogeii requirement creps and its availability iiithe soil. More precise and timely nitrogen soil test would strengthen the case for limiting nitrogen applications. Sincelarmover-dose fertilizer, itispossible to ers usually apply fertilizer. A maintain good crop yield with reduced bctween the yield loss,ifhappens, and compromise water qualityimprovement is also important. Use sources. Apply fertilizer in split slow relcase nitrogen applications and apply when rainfa11 isminimal. are also Selectionof crops and growing seasons nitrate coniinportantfor controlling groundwater of tamination. Selecterops that require low ameunt nitrogen for their growth and can be grown during does not favormuch nitrate leachthe period which ing.Crop rotation caii also be helpfiilin controlling availability and

9.2 Prevention

enviromnental

9.2.1 Agricultural management isto reduce the Thc most importantstep forfarmers amount of nitrogen fertilizer to the crops. This is easier said than done becausemost farmersconsider t nitrogen fertilizer to l)e cheap insuranee agalnst, 1991). The inaifi problem is a crop failure (Looker,

sources,

and

of prevent directintroduction

OF RAINWIYT-ER CNCHMENT

agrichemi-

SYSTEMS

groundwater

AfOL,8 NO,2 2003

nitrate

contamination.


Association (JRCSA) {JRCSA)

Japan Rainwater Catchment Systems JapanRainwaterCatchmentSystemsAssociation

Table 4:Effectiveness and

of

farmingpracticcs for protectinggroundwaterfrom pesticide Logan, T.J. (1990)) (after

nitrate contarnination

Farming practice

Degree of effectiveness"

PesticidesNitrate Structural Irrigation systems Antibaeksiphondevices Animal waste storage Subsurfacetiledrainage Wellhead protection

MHNLH

MHMMH

HHH

HMM/L

MNNHM

NHHNH

Cultural

Grassed waterways Cover cropping Low-input farming Management Integratedpest management Animal waste management Nutrient

*H

9.2.2 Land

The most to select

management

Pesticidemanagement Irrigation management M medium, =high,

L

=

N

and

=low

management

of 1and management is land use pattern. FDr animal farming and intensiveagriculture, areas that have high vulnerability of aquifer contamination by nitrate should be avoided. fallow lands favornitrate contaniination, so lands should be crop-covered or

important matter

appropriate

grass-covered.

9.2.3 Soil management By adding organic

amendments,

pra £ ticing conser-

=

none

the installation of a

a

rystore.

animal

waste

storage faeility termed as These facilities are proven to store without leaking.

10 A guideline of .

management

strat-

egles

The

steps

associated

the

with

management

of

a

by a flow chamt in Figure 8. The steps mentioned here are the summary of the management strategies indicated in different aft)rementioned literatures. However, aquifer

nitrate-contaminated

these are put

holdingca-

efficient

Slur-

are

shown

to give an overview

Ligether

that

so

a

duce the chance of groundwater nitrate contaJnina tion, Soilthat has suMcient organic matter requires a low amount of fertilizer fbrcrop growth, thus reducing the chance of groundwater nitratecontami-

be managed eMciently, Moreover, to overcome the problems,usually found in some steps of presentmanagement strategies,probablesolutions are discussed.Management strategies, discussedhere,are solely on the basisof aquifer protection from contamination, The fo11owingare the necessary steps for eMcient

nation.

management

9.2.4 Irrigationmanagement Switchiiig from furrow irrigationto

1) Problem identification 2) Nitrogeiisource identification 3) Associatedcauses/factors identification

vation

tillage

pacity

of

and

cover-cropping,

water

the soil can be improved, which

duce nitrate ieachingfluxrate,

tion

applies

more

water

evenly,

and

will

re-

ultimately

sprinkler

reducing

the

re-

irrigachance

leaching below the crop zone, If furrow irrigation is employed, use surge flowtechniques to of

nitrate

apply

evenly,

Flood irrigation should be

EMcient allocation

avoided, amount

more

water

and

to control

of

tirne of application

nitrate

irrigationwater, its are also important

leaching,

of a nitratecontaminated

waste

management

Proper handling aJid storage of animal wastes prevent nitrate leaching. Animal wastes should be stored in concrete is pits, Another possible solution

JOURNALOF

aquifer:

4) Effect assessment

5) Analyses 6) Remedial measures identification

10.1 Problem

The

extent

and

severity

should

contamination

9.2.5 Animal

aquifer could

nitratcrcontaniinated

of the groundwater be identifiedfirstby

nitrate survey-

ing well-water samples from statistically representative observation locations. Observationwells should

be

any biasness, and water samfrom the randomly-selected wclls be tested accurately in the laboratoryfor

selected

ples thus should

RAINWArER

without

collected

CMCHMENT

SYSTEMS

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fied.These includeidentification of: 1) [[bpographic 2) Land use 3) Rainfall, evaporapatterii, pattcrn, tion and groundwater recharge 4) Aquifer pattern, thickness distribution geologic pattern, 5) Clay pattern and 6) Groundwater head distributioll pattern. 10.4 Effect assessment The ultimate harrn of groundwater nitrate centamt･here inationis the healtheffect. However, thollgli are a

lotof

studies

on

sources.

causes

and

remedies

itishard to get any literature c)n pcople exposed to and actually affected from even fora highly groundwater nitrate containination contarninated arca. Therefore, this type of $tudy is coiitamination,

of nitrate

also

needed.

10.5 Analyses The fbllowingaiialyses take any

remedial

coiitaminatcd

are

needed

measure

beforegoing to

ot' managing

nitrate-

aquifer:

1) Estimatingnitrate Ieachingfiux,ifpossible, otherwise identifying nitrate leaching potential 2) Identifying aquifer vulnerability potential 3) Identifying aquifer contamination potential 4) Assessiiig long-tcrmeffeet of contaminat･ion by Figure 8: Flow chart showing managcmcnt egies for groundwater nitrate

strat-

natloll

Field-tests using field-kits nitratemeasurement. wells should should be avoided. Some observation long-term contamibe selected to see the trends of nation, and water samples should be collected and A more frequentsamtested biweeklyor monthly. weekly) during the period of peak anthrop!ing(say, pogenicactivities may lead to the betterunderstandIn periodic water ingof the trends of contamination, but not only t･henitrate (NOi) quality assessment, found of the cations and anions usually also most iiithe groundwater or at leastcations and anions compound as N02-, NH4+) of other nitrogen (such Finallyaerial and time disshould be measured. be presented to see the and itstrends.

tribution of nitrate should extent of the contamination

10.2 Nitrogen

identification

source

AII of the possible major gen in the contaminated

Particular pogenicsources,

emphasis

and

miiior

sources

of nitro-

should be identified. be given to the anthr} and location of feramount FVom disposalapplication. region

should such

as

manllre and waste tilizer, of the nitrogen, its regional information the detailed loarl distribution on sllrfeLce soil cycling and process should

be identified.

10.3 Causeslfaetors identification ame associated with the site-spccific Fax]tors that should be idcntinitrate contamination groundwater

30pmJOURNAL

OF RAINWAI-ER

CMCHMENT

the

sirnulation

model,

contami-

ifpossible

10.6 Remedial measures The main target of reinedial rneasures is to protect aquifer from contamination by changing the manageable factorsdescribedin section 9,2,so that we get crop yield with [[t)handle this managemellt

optimurn

a strong

minimum

contamination.

driver,we need to have between the inanagement incontamination potential. How-

relationship

dicatorsand aquifer that in most of the cases ever, ithas been mentioned by the it is diMcultto establish such a relationship regression analyses. In such a case, it isexpected by introducthat this problem could be overcome To ing an Artificial Neural Network (ANN)model. we siinulate the effect of long-termcontamination, must have to estimate nitrate leachlngfliix.Fbr d} ingso, wc have to findout or developa nitrate leachingfiuxmodel of conceptual quasi-physieal type, as a between the data requirement of a fu11y compromise physical-based

fu11ycoiiceptual rameter

aquifer

values

from

rnodel

or

and

estimation

black box

of management short-term

and

accuracy

of a

Optimum pafactors, which protect long-termcontaminamodel.

tion, could be findout using any optimization nique likeGenetic AIgorithm (GA).

tech-

11 Conclusions numfroni a considerable Literatures are reviewed scientific ber of papers publishedin difft)rent jourto give nals and of articles published in the Internet of eff6cts and remedies an overvicw ef the causes, A of nitrate contamillation. guideline groundwater

SYSTEMS AtOL.8 NO.2 2003 NII-Electronic Library Service



managing

nitrate-contarninated

aquifers

The fbllowing conclusions from this literature review:

could

vided.

e

Groundwater

which

cause

a

e

due to applicafertilizer to the

tanks, cause of

remedy

taminated

be

mainly

nitrogen-based

trolled septic tiOII.

ment

be controlled be-

fields, livestock manure

agricultural

As

water

may

be

a

of con-

but treat-

solution,

processisexpensive and from the water.

uncon-

contamina-

cannot

all nitrates

removed

Thc

to the prudent solution approach problem is the protection of groundwater from

by

adopting

model.

present

and

groundwater

nitrate

contamination,

long-term effects a

of

nitrate

leachingfiuxmodel of conceptual quasi-physical type is needed as a compromise between the data requirement of a fu11y physical-based model and estimation accuracy of a fu11y conceptual or a blackbox model.

wnb

site:

http:!!www.caf.wvu.edulNforage/ni-

pp.4683-4690.

Burden, R.J.(1982): NitrateContaminationofNew [131

Acknowledgement The authors would liketo thank the Japan Society forthe Promotion of Science for supporting this research from the post-doctoral research fund.

(JSPS)

References

[1]Albert, E.E., and

Spomer, R.G. (1985): Nitrate as Movement in Deep Loess Soils, American Society

AgriculturalEngineering Paper 85-2030, ASAE, St. Joseph,MI, p.16. A Model for Relating Land Use [2]Aley, T.J. (1977): and GroundwaterQuality in Southern Missouri, Dilamarter, R.R. and Csallant,S.C.(Eds.), Hydrologic Probternsin Karst Regions,Western Kentucky University, Bowling Green,KY, pp.323-332. Andrews, R.J., Lloyd, J.W. and Lerner, D.N. [3] Modelling of Nitrate Leaching from Arable (1997): Land into Soil and Chalk 2 -Model Confirmation and Application to Agriculturaland Sewage Sludge Management, Joumal oje likedrology, 200(14), pp.198-221. Cround[4]Ball, D.F. and MacDonald, A.M. (2001): water Nitrate vailnerable Zones forScotiand, Commissioned Report CRIOI1250, British Geological Survey, MurchisonHouse, Edinburg, p.64.

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net,

Ewen, J. (2000): Nitrogen Transformation Component for SHETRAN Catchment Nitrate1[leansport Modelling, Journal ofHydrology,230(1-2),pp.1-17. Boltz, G.H. (1978): Soil (]hemistrltA. Basic Ele[10] ElseveirSciencePublishers ments, B.V. Bruce, E.L. and Dina, L. (2002): [[Yeatment of [111 Perchlorateand Nitrate-contaminated Groundwater in an Autotrophic, Gas Phase, Packed-bed Bioreactor, Water Resean:h, 36(14),pp.3647-3653. Bruce, O.M. and Edward, D.S. (2002): Hy[12] drogenotrophic Denitrificationin a Microporous Membrane Biorea£ ter, VVaterResearch,36(19),

Incorporationof the Artificial Neural Network model into the aquifer vulnerability (ANN) analyses may be a technique of gettingan ap[[b simulate

R.H.

[9]Birkinshaw,S.J.,and

appropri-

strategies.

propriate regional management

T.N., Barbara, C.R., Kerie, J.H. and DenA National Look at Nitrate Con(1998): tamination of Groundwater, Joumal of PVdter Conditioning and Purijicatton, 39(12), pp.76-79. Bernhard, C., Carbiener, R. and Cloots, A.R. [6J Nitrate Pollution of Groundwater in the (1992): -A multidisciplinary Asatian Plain (Fli,ance) Study of an Agricultural Area:The Central ried of the III river, thvzronmental Geolqgyand Wdter Sciences, 20(2),pp.125-137. Groundwa[7]Beseki,G. and MacConchie, J, (1999): ter Recharge Modelling using the Monte Carlo [fechnique, Manawatu Region, New Zealand, Journat of Hydrology, 224(3-4),pp,137-148. Agricultutal Practices and [8]Bhumbla, D.K. (2003): Nitrate Pollution of Water, VVest Virpinia Uiiiversity Extenston Seroice,Published in the Internis,

tratepollutionlnitrate.htm

more

ate management

.

and

nitrate

the problem, treatment

potentialcontamination e

world-

to

needs

Anthropogenicsources, tion of access

e

is a

contamination

problem, of its implications on human health.

wide

.

nitrate

[5]Bernard

isalso pro be drawn

Zealand Aquifers: A Review, IVew Zealand Joumal ofScience,25, pp,205-220. CEC (1991): Concerning the Protection of Waters [14] Against Pollution Caused by Nitratesfrom Agricultural Sources,Council Directive31 Decernber1991, 9116761EEC. Qt]lJoumal Eur. Commun., 375(1), pp.1-8. Comly,H.H, (1987): Cyanosis in Infaiits Caused by [15] Nitrates in Well Wiiter, Journalof the Arnerican Medical Assoczation,257, pp.2788-2792. Dillon, P.J., Rngusa, S.R. and Richardson, S.B. [16] (1991):Biochemistry of a Plume of Nitratecontaminated Groundwater, In: Bogardi, I., Kuzelka, R,D. (Eds.), Nitrate Contamination:ExConsequence, and Control, NATO ASI Seposure, rial G: EcologicalScience,Springer, Berlin, 309, pp,173-180. Edward, B.A. (2003):Farming Practices for [17] Groundwater Protection, Cbtlege ofAgriculture and Horne Economies- IitformationDepartment, Computer Resource Unit, Wtishington State University, Website: http:1!cru.cahe.wsu.edulCEPublicationsleb1716!eb1716.html Evans, T.A., and Maidment, D.R. (1995): A Spa[18] tial and Statistical Assessment of the Viilnerability of [Ilexas Groundwater to Nitrate Contarnination7 (]llVVR Onltne Report 95-2, University of [fexas,

RAINwATER CAT'CHMENT SYSTEM,S, NII-Electronic

Library Service



Web

http:!!www.ce.utexas.edufprof/maid-

site:

ment!GISIIydro/docs!reportslevanslrep95.2.htin

Sources of r19]fail}at,J.P. (1990):

Nitrate in Fissure

Groundwaterin the IIumid TropicalZone -The Example

of

Ivory Coast, Joumal

of

Hydrotogy, 113,

111L

Hudak, l35]

pp,231-264.

228(1-2),pp.37-47. E,, Hiramatsu, K., Kawaehi, T. and Kitamiira, K. (2001), Estimation of Long-[[brm Change in Non-Poiiit･ Contamination Flux to Groundwater using Genetic Algorithm. 71uns. ofJSiRDE, 215, pp.31-39.

Jacek, D. (2003): Nitrate Removal [37]

and Convc.irsion Nitrogen. ChemDen -A SimpleChemicalProeess ConvertsNitrate Pollutantsto Nitrogen Gas, Artzcle zn the Intemet, Web site: http:lfwww.land.govf

to

projectslnitrate/index.htm

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