Organometallic Compounds in the Environment, 2nd ...

Organometallic Compounds in the Environment Second edit ion

Edited by P.J. Craig School of Molecular Sciences, D e Mont f ort Universit y , L eicest er, UK

F irst Edition published by Longman, 1986. ISBN:0582 46361 0 Copyright

©

2003 John Wiley & Sons Ltd, The Atrium, Southern G ate, Chichester, West Sussex PO19 8SQ, England Telephone (+ 44) 1243 779777

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2002191061

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3

Organotin Compounds in the Environment

) &,0$ Dipartimento di Biologia, Universita di Padova, Padova, Italy

3- &5$,* DQG & +$55,1*721 Department of M olecular S ciences, De M ontfort University, L eicester, UK

,1752'8&7,21

Both inorganic and organotin compounds have extensive industrial uses, and these uses, environmental aspects and toxicological properties have been particularly well covered in several multi-volume and monograph publications in recent years [1–6]. Within these works are detailed accounts of organotin levels in aqueous, atmospheric, surface microlayer and sediment compartments for organotin species and so indicative summary levels only will be stated in this chapter. Similarly the analytical and toxicology aspects will be covered in overview format. Total organotin production is more than 50 000 tonnes per year, with about one-quarter of this being triorganotin biocides. About 4000 tonnes per year of TBT derivatives are manufactured [7], as wood preservatives, antifoulant and disinfectant biocides. Of total tin metal prepared, 7 % is for organometallic tin compounds. Useage details are given in Table 3.1. The tin–carbon bond is stable to water, atmosphere and heat (at least to 200 °C). UV radiation, strong acid and electrophilic reagents cleave the tin– carbon bond. Solubility in water varies greatly with R and X in R nSnX 4 n and on their relative numbers. Toxicity is dealt with in detail in Section 3.8, but is mentioned here in view of the biocidal uses. M aximum toxic effect in R nSnX 4 n is usually achieved for R 3 SnX; however, unless X is toxic it does not have much effect on overall toxicity. Within R 3 SnX the nature of R profoundly effects toxicity to a single species and relative toxicity to different species. Et 3 SnX is most toxic to mammals, Bu 3 SnX to aquatic life. Increase in chain length of R decreases toxicity. D etailed surveys are given in R eferences [7–9]. Tables 3.2 and 3.3 give an overview of modes of entry and general toxicity. The industrial uses, toxicities and modes of entry of organotin compounds are given in Tables 3.1, 3.2 and 3.3. Table 3.1 presents an overview. In environmental terms, the role of tributyltin (TBT) is the most important, and the Organometallic Compounds in the Environment Edited by P.J. Craig # 2003 John Wiley & Sons Ltd

102

Introduction

7DEOH Industrial applications of organotin compounds Application

Compound

Comment

R3 SnX Agriculture fungicides (C6 H5 )3 SnX (X OH, OAc) antifeedants (C6 H5 )3 SnX (X OH, OAc) (c-C6 H11 )3 SnX acaricides (X OH, N:C N:C N) w w w j j H H (C6 H5 (CH3 )2 CCH2 )3 Sn)2 O

Antifouling paint, biocides

Wood preservative, fungicides Stone preservation, Disinfectants Molluscicides (field trials)

Total biocidal use is about 20 % of total organotin production. Ph3 SnX used as an antifungal agent, (cC6 H11 )3 SnX used as acaricide. Can enter surface run off. 450 tonnes pa TBT. Used in USA in 1987 for antifouling paint useage. Controlled since 1982

(C6 H5 )3 SnX (X OH, OAc, F, Cl, SCS:N(CH3 )2 , OCOCH2 Cl, OCOC5 H4 N-3) (C6 H5 )3 SnOCOCH2 CBr2 COOSn (C6 H5 )3 (C4 H9 )3 SnX (X F, Cl, OAc) ((C4 H9 )3 Sn)2 O (C4 H9 )3 SnOCOCH2 CBr2 COOSn(C4 H9 )3 (C4 H9 )3 SnOCO(CH2 )4 COOSn(C4 H9 )3 ( CH2 C(CH3 )(COOSn(C4 H9 )3 ) )n w w ((C4 H9 )3 Sn)2 O Applied as 1±3 wt-% in a (C4 H9 )3 Sn(naphthenate) solvent ((C4 H9 )3 Sn)3 PO4 ((C4 H9 )3 Sn)2 O (C4 H9 )3 SnOCOC6 H5 ((C4 H9 )3 Sn)2 O (C4 H9 )3 SnF ((C4 H9 )3 Sn)2 O R2 SnX2

Heat and light stabilizers R2 Sn(SCH2 COO-i-C8 H17 )2 (R CH3 , C4 H9 , C8 H17 , for rigid PVC (C4 H9 )OCOCH2 CH2 ) (R2 SnOCOCH CHCOO)n w (R C4 H9 , C8 H17 ) (C4 H9 )2 Sn(OCOCH CHCOOC8 H17 )2 w (C4 H9 )2 Sn(SC12 H25 )2 Homogeneous catalysts for RTV silicones, (C4 H9 )2 Sn(OCOCH3 )2 (C4 H9 )2 Sn(OCOiC8 H17 )2 polyurethane foams and transesterification (C4 H9 )2 Sn(OCOC11 H23 )2 (C4 H9 )2 Sn(OCOC12 H25 )2 reactions ((C4 H9 )2 SnO)n

70 % of total organotin use. Prevents loss of HCl from polymer at 180±2008C Used at 5±20 g kg 1 PVC. Organotins can leach into food, beverage, waters sewage sludge.

(continues)


103

7DEOH (continued) Precursor for forming SnO 2 films on glass Anthelmintics for poultry

(CH 3 )2 SnCl2 (C 4 H 9 )2 Sn(OCOC 11 H 23 )2 56Q;

Heat stabilizers for rigid R Sn(SCH 2 COO-i-C 8 H 17 )3 a (R CH 3 , C 4 H 9 , C 8 H 17 , PVC C 4 H 9 OCOCH 2 CH 2 ) (C 4 H 9 SnS15 )4 (C 4 H 9 Sn(O)OH)n Homogeneous catalysts C 4 H 9 Sn(OH)2 Cl for transesterification C 4 H 9 SnCl3 reactions Precursor for SnO 2 films C 4 H 9 SnCl3 on glass CH 3 SnCl3 a a These compounds are used in combination with the corresponding R 2 SnX 2 derivatives Adopted with permission from this work, first edition

synthesis methods of these compounds generally may be indicated by a brief description only (Table 3.4). Essentially the tetraalkylated form may be considered to be synthesized and the desired mono di- or tri-compound produced by redistribution (e.g. Equation 3.1) 3Bu4 Sn SnCl4 !4Bu3 SnCl

(3..1)

Individually, the Grignard or aluminium routes, followed by disproportionation to the compound chosen, tend to be used. Methods are discussed in detail elsewhere [5]. The required counter ion, e.g. Cl , is introduced by a nucleophilic substitution. The methacrylate copolymer (F igure 3.1) is synthesized by a free radical initiated attack on the C C bonds from TBT methacrylate monomer w and methylmethacrylate monomer to give a copolymer. Organotin waste during manufacture is generally removed by incineration at ! 850 C but UV radiation and K M nO 4 or ozone oxidation have been used [10]. With this in view, the question of organotin compounds in the environment can be reduced to the behaviour of TBT in aqueous and sediment matrices although organotin release from landfill sites has been researched in recent years (see below), and there is some organotin leaching from polyvinylchloride (PVC). Similarly, tripropyltin (TPT) compounds used in agriculture are also toxic to aquatic life. TBT essentially degrades sequentially to dibutyltin (DBT) and monobutyltin (M BT) so the chemistry of the latter two arising from their uses in PVC merges into the former. The use of TBT copolymer also reduces to the aqueous chemistry of the TBT cation, as the antifoulant works by sequential hydrolysis of the TBT moiety from the polymer backbone. Interestingly the

104

Use of TBT in Antifouling Preparations CH3

CH2

CH3

C

CH2

C

C O

C

OCH3

O

O Sn(n -Bu)3

H2O

)LJXUH Methacrylate TBT copolymer

TBT copolymer systems also may include copper compounds and organic biocides in order to give broad spectrum effectiveness against organisms resistant to TBT. Environmental studies do not usually focus separately on this aspect of TBT-based antifouling paints. There is some evidence for direct input of M BT and DBT from PVC materials to the environment, but most comes from TBT degradation.

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F ouling of ships means the attachment and growth of e.g. algae, shell fish and weeds on the outer hull and on large vessels hundreds of tonnes of fouling may grow within one year. Driving the non-smooth vessel through the water becomes correspondingly more difficult and expensive. Various triorganotin species were noted as being very effective as antifoulants (TBT is effective at a few ng L 1 as a biocide for algae, zooplankton, molluscs and the larval stages of some fish). Triphenyltin species (TPT) are also effective but less used. TBT was first used in ‘free association’ formulations where the biocide is physically mixed with the other paint ingredients and slowly dissolves in use to reduce TBT. These coatings last for about 2 years. By 1974 the methyl methacrylate– TBT copolymer system (TBT-MM A) had been developed [10] (F igure 3.1). These ‘self polishing’ systems release TBT steadily from the top few nanometers, exposing a free TBT-containing polymer surface below. This system can last for more than 5 years before exhaustion. The basic advantages are that release of TBT is controlled, constant and just sufficient for the purpose. The term ‘self polishing’ arises from the fact that decay of the polymer still leaves a smooth surface on the hull of the boat, reducing drag and fuel costs. When the copolymer is exhausted the boat can then be directly repainted.

105

Organotin Compounds in the Environment 7DEOH Possible direct modes of entry of organotin into the environment Medium

Species

Source

Air

R 3 SnX

Agricultural spraying Volatilization from biocidal treatments Antifouling paint sprays Landfill Incineration of organotin Treated or stabilized waste materials Landfill Glass coating operations— spraying of organotins onto glass at high temperature to give SnO 2 films Landfill Agricultural applications Wood preservation Burial of organotincontaining waste materials Antifouling coatings Molluscicides Overspraying from agricultural applications Land run-off from agricultural useage Industrial processes, e.g. slimicides in paper M anufacture Landfill Leached from PVC Landfill

R 3 SnX, R 2 SnX 2 , and R SnX 3

R 2 SnX 2 and R SnX 3

Soil

R 3 SnX R 3 SnX, R 2 SnX 2 and R SnX 3

Water

R 3 SnX

R 2 SnX 2 and R SnX 3 Taken from this work, first edition, with permission

7DEOH

Species specific of triorganotin compounds, R 3 SnX toxicity

Species

R in most active R 3 SbX compound

Insects M ammals Gram-negative bacteria G ram-positive bacteria, fish, fungi, M olluscs, plants F ish, fungi, molluscs F ish, mites

CH 3 C2H 5 n-C 3 H 7 n-C 4 H 9

Taken from this work, first edition, with permission

C6H 5 c-C 6 H 11 C 6 H 5 (CH 3 )2 CCH 2

106

Legislation on TBT

7DEOH

Synthesis of tetrabutyl tin

(1) Grignard (2) Wurtz (3) Aluminium (4) D irect

4RMgX SnCl4 !R4 Sn 4MgClX 4BuCl 8Na SnCl4 !Bu4 Sn 8NaCl 4R3 Al 3SnCl4 !3R4 Sn 4AlCl3 BuBr Na=Sn !Bun SnBr4 n

Treatment of the Queen Elizabeth 2 in 1978 was reported to result in fuel cost savings of 12 % annually [11]. D espite the environmental problems discussed below, TBT replacement paints (containing, for example, cuprous oxide with an organic biocide) are probably not as effective as copolymer TBT over a 5-year service life [12]. However, for small vessels, non-TBT systems are now used (see below). Generally the TBT copolymer market has not declined, but 90 % of TBT is now being used mainly by the world’s commercial shipping and 10 % for pleasure craft. The rate of release of TBT is given in Pg cm 2 day 1 with a design rate of 1.6 (the maximum proposed limit by the U S EPA and the IM O is 4 Pg). Bearing in mind the environmental decay of TBT (see below), it is assumed that open-ocean loss of TBT is not an environmental problem. However, recent work showing elevated TBT levels in higher marine animals makes this assumption less firm (see below and Section 3.8). Generally, tin concentration in the paint can be up to 3 % with an initial leach rate of 6 Pg S n cm 2 day 1 . Large vessels in harbour and inshore small fishing boats and pleasure craft have given rise to the main TBT environmental problem. A large vessel in port for 3 days might lose 200 g of TBT to the waters, 600 g if freshly painted. This can lead to concentrations in large marinas or dockyards of 100–200 ng Sn dm 3 in the water [13]. In smaller estuaries, marinas, etc., for smaller pleasure craft dissolved TBT can be in the range 10–70 ng dm 3 [14]. Much of this can arise from hosing of vessels prior to repainting where actual fragments of paint containing TBT may be removed from the hull during cleaning (i.e. the ‘self polishing’ effect is evidently not always achieved in practice!).

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The effects of TBT on non-target organisms are discussed in Section 3.8, but the actions to remove environmental problems are discussed for completeness in this section. Essentially, legislation being a national function in a complex world, control has been imposed on a piecemeal basis. H owever, the degree of harmonization has been better in the case of this late-developing pollutant, with attitudes and structures being better advanced than in the case of earlier environmental pollutants. The focus on control of TBT has been multifaceted, viz.


107

(i) The release rates are defined to correspond to minimal rates needed for effect, i.e. 1..6–4 Pg cm 2 d 1 maximum. (ii) F ree association (i.e. free releasing) paints are now banned in many countries. (iii) The focus has been on near shore effects where reported environmental damage is greatest. (iv) Prohibitions for use have therefore been focused on smaller vessels ( 25 metres in length, i.e. inshore craft). (v) The health of local economic assets (e.g. oyster beds) has been a factor of importance. (vi) R eduction by good management and organization of the entry of TBT into the environment from dock and boatyards, etc., has also been a tactic. (vii) N evertheless a total ban on TBT, ocean wide, is proposed by the IM O in 2008. It is only reasonable to point out an environmental bonus of TBT in that its use is estimated to save 4 % of the fuel use of the worlds fleet (about 7.2 M tonnes) which is about 22 M tonnes of emitted CO 2 and 0.6 M tonnes of emitted SO 2 [15]. Environmental legislation in several countries has been based on a realization of the persistence of TBT in the environment (several years half-life on sediments) and damage to marine species at very low concentrations (e.g. 0.1 ppb or ng dm 3 ). In addition, larvae of marine organisms are particularly sensitive [16]. However, there is less evidence of harm to humans (but see Section 3.8) [17]. The general pace of legislation has been rapid, e.g. EU Directive 677, 1989. The first ban (of TBT on boats of 25 m length) was in F rance in 1982 (because of the damage to oyster beds). In 1987 the U K restricted the use of copolymer paints with ! 75 % TBT and effectively eliminated free-association paints [18]. N umerous states of the U SA followed suit. In some countries TBT can only be supplied in containers ! 20 dm 3 (to discourage small scale use). F ull details for actual and proposed legislation are given elsewhere [19,20]. At present only Austria, Switzerland and New Zealand have totally banned TBT. On the other hand many other countries still have little or no control over TBT. The philosophy of control and legislation on TBT is based on a view regarding its toxicity and its environmental persistence in sediments being much greater than that in water. These properties are discussed later in this chapter (Sections 3.7 and 3.8). Continuing monitoring work gives a guide to the effectiveness of legislation and tends to demonstrate rapid clearance from water after legislation but much slower removal from sediment.

',675,%87,21 ,1 7+( (19,5210(17

U ses of methyltins are not thought to lead to the significant presence of methyltins in water and sediments. However, methyltins have been found in

108

Distribution in the Environment

the environment probably as a result of a process of biomethylation (see Section 3.6). Similarly octyltins have not been reported away from point source use. It is also assumed that M BT and D BT found in the aquatic environment arises from decay of TBT rather than direct input of the former species. In sea water, following hydrolysis, TBT exists as a cation complexed to chloride, carbonate and hydroxide [21]. It is rapidly absorbed onto suspended particulate material and hence, in due course, sediment [8]. This happens more rapidly than does aqueous decay, so TBT tends to be found in sediments on removal from the water column. As noted, most recent monitoring work has demonstrated clearly that TBT concentrations in water decline quite rapidly once the input of TBT is reduced or eliminated. M any surveys have illustrated this and the reader is referred to numerous detailed reference sources for quantitative information [22–26]. The initial response rate is rapid, usually less than 5 years. With a log K OW of 3.7 [27] TBT is quite lipophilic and would be expected to bioaccumulate. Bioaccumulation factors in various species range from 1000 to 30 000 (see also Section 3.8) [28]. Bioaccumulation to surface microlayer increases TBT concentrations over subsurface water two to tenfold [29]. Bioaccumulation factors to organisms are discussed in the toxicity section (Section 3.8). R ecovery from sediments is much slower and apparently variable. That the water above the sediment tends to clear rapidly suggests that, although there is a reservoir of TBT in the sediment, it is not completely available for replenishment of TBT lost from the water layer by non-use and decay. Table 3.5 gives some half-lives of TBT in sediments and other media [30–36]. In a work of this length only indicative examples can be given but these are intended to be representative. Tables 3.6 and 3.7 show a list of organotin compounds that have been observed and measured in the natural environment (the analytical techniques developed to make these measurements are discussed below). F rom Tables 3.6 and 3.7 the following deductions can be made: (i) TBT decays sequentially to DBT and MBT. (ii) The organotin derivatives may be reduced (i.e. converted to hydrides) in the environment. (iii) They may also be biomethylated. (iv) Some are volatile (TBTO, hydrides). (v) Landfill sites make a contribution to organotin levels in the environment. It should be noted that, as for most organometallics in the environment (except for arsenic, see Chapters 5 and 6) there is no information on the TBT or any other organotin counterion other than in the case of the saturated tetraorganotin and the volatile hydrides and TBT in seawater (where complexation with OH , Cl , and CO 23 takes place) [21]. One may speculate on the existence of organotin counter ions, but there is no evidence.

109

Organotin Compounds in the Environment 7DEOH Some estimated half-lives for TBT Medium

Half-life

R eference

F reshwater Estuarine water Seawater Water/sediment mixture Estuarine sediment Marine sediment

6–26 days, (light), 4 months (in dark) 1–2 weeks 6–127 days 5 months–5 years 3.8 years 1–4, 100–800 days 1.85–8.7 years 140 days (TPhT)

8, 30, 31 8, 31 31 32, 33 34 35, 36 35, 36 8

Soil

7DEOH Organotin species detected in the natural environment. R eproduced with permission from R ef 8 Species

Compartment

R eferences

Bu 3 Sn

Sediment, water, surface microlayer, marine animals As above As above Algae, microbial cultures, sediments As above Harbour sediments, surface water As above, sediment, surface water Sediment, surface water Atmosphere, surface water, landfill gas, sewage gas Water, domestic waste deposit water

Very many; see e.g. R efs 1–9

Bu 2 Sn 2 BuSn 3 SnH 4 M en SnH 4 n Bu 3 SnMe Bu 2 SnMe2 BuSnMe3 M e4 Sn M e3 Sn , Me2 Sn 2 , M eSn 3 BuSnH 3 Bu 2 SnH 2 EtMe3 Sn Et 2 M e2 Sn Et 3 M eSn Et 4 Sn

Sediment, landfill gas, sewage gas, waste water As above Landfill gas As above As above As above

As above As above 37–41 As above 40, 42–44 40, 42–44 40, 44, 45 40, 41, 46–49 38, 43, 47, 50, 51 40, 41, 48, 49, 51 40, 48, 49, 51 48 48 48 48

Transfers of organotins from sediment to water have been estimated at between 50 and 790 nmol m 2 y 1 . Water-to-air fluxes have been calculated at between 20 and 510 nmol m 2 y 1 . In conjunction with this, methylation and reduction have lead to the observation of volatile organotin species suggesting a considerable mobilization of tin, including to atmosphere [52]. Prior to legislation, or to its effects becoming noticed, water concentrations of TBT in polluted zones were recorded at up to 1–2000 ng Sn L 1 . Surface microlayer levels were up to 25 000–36 000 ng Sn L 1 . Sediment levels of up to 5500 ng g 1 were noted although levels of hundreds of ng Sn g 1 were more common. Sewage sludge had similar levels, with sewage treatment plant effluent up to 55 200 ng SnL 1 Bioconcentration factors in organisms are discussed below.

110

Distribution in the Environment

7DEOH Some butyltin levels measured in the natural environment. Adapted with permission from Hoch, R ef. 8, pp. 732 and 735 and refs therein Butyltin concentrations in water (ng Sn L 1 ) Location Sado Estuary, Portugal San Pedro R iver, Spain Cadiz Bay, Spain Guadalete R iver, Spain Antwerp harbour, The N etherlands Ganga Plain, India Marinas in The Netherlands

MBT

DBT

TBT

18–60 6.9–14.4 8.90–41 9.8–25 51–76

52–160 5.5–14.3 8.3–68 5.7–39.5 217–283

39–870 9.3–16.3 8.3–488 9.9–116 765–1000

2–70 3–310

2–101 0.1–810

3–20 0.1–3620

Concentrations of butyltin compounds in municipal wastewater (ng Sn L 1 ) and sewage sludge (Pg Sn kg 1 dry wt) M BT Zu¨ rich, Switzerland Goslar, Ost Bomlitz Hildesheim (1994) Hildesheim (1996) Harsefeld Sarnia, Canada Toronto, Canada

245 10 35 135 136 64 16–31 440

D BT

TBT

523 60 40 215 269 78 11–61 210–305

157 15 15 140 83 12 5–175 245–277

Comparison of butyltin concentrations in river, lake, marine and harbour sediments (ng Sn g dry wt) Location San Pedro R iver, Spain Guadalete R iver, Spain Cadiz Bay, Spain Bay of Arcachon, F rance San Diego Bay, California Pearl Habor, Hawaii Lake System Westeinder, The N etherlands Leman Lake, Switzerland Hamburg, Germany Toronto, Canada Vancouver, Canada

Depth (cm)

MBT

DBT

0–10 0–10 0–10 0–51 0–6 0–6 a

1.9–6.1 16.1–129 1.2–31 6–156 2–185 5–533 6–100

1.5–8.7 20.5–510 1.1–52 5–141 2–265 4–367 6–96

a a a a

186 430 580 3360

295 610 248 8510

TBT 0.7–11.1 26.5–601 1.6–225 16–161 2–242 4–2830 6–520 627 5200 539 10780

1

111


7DEOH continued Comparison of the concentration of butyltin compounds in body and tissues of various organisms (ng Sn g 1 wet wt) Animal

Tissue

Bottlenose dolphins, Italian coastal Blubber waters Liver Bluefin tunas, Italian coastal waters Liver Muscle Blue sharks, Italian coastal waters Liver Kidney Harbour porpoises, Black Sea; Liver Sea otters, Californian Liver coastal waters K idney Brain Zebra mussels, lake system Body Westeinder, The Netherlands Eel Body R oach Body

MBT

DBT

TBT

55 150 38 15 6.6 8.7 8–35 7–360 7–61 2.4–24 21–120

16 800 125 8.6 5.1 26 50–164 21–5820 3.7–200 1.8–105 20–160

41 250 46 39 19 105 15–42 19–3020 4–210 2.7–140 180–2500

13–63 7–34

9–40 20–210

50–390 160–2500

a not stated

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