Long-term effects of heavy metals from composted ... - Springer Link

3 downloads 55 Views 539KB Size Report
Mar 18, 1993 - and Tabatabai 1979), and L-asparaginase (Frankenberger and Tabatabai 1991 a) has been demonstrated. While the effect of sewage sludge ...
Biol Fertil Soils (1994) 17:257-262

9 Springer-Verlag 1994

Pier Lodovico Giusquiani 9 Giovanni Gigliotti Daniela Businelli

Long-term effects of heavy metals from composted municipal waste on some enzyme activities in a cultivated soil

Received: 18 March 1993

A 3-year field experiment on a calcareous Fluventic Xerochrept planted with corn (Zea mays L.) was carried out to evaluate the effects of amending the soil with high and low rates of composted municipal waste on soil enzyme activities (alkaline p h o s p h o m o n o esterase, phosphodiesterase, arylsulphatase, dehydrogenase, and L-asparaginase). These enzyme activities all increased when compost was added at rates of up to 90 t ha -1, and the phosphatases continued to show a linear increase with compost rates of up to 270 t h a - 1. The addition of mineral fertilizer increased enzyme activities in unamended soil, and masked the stimulating effect of compost on the amended soils. Heavy metals did not affect soil enzyme activities up to a compost addition of at least three times the amount specified by Italian law. Abstract

Municipal waste compost Heavy metals 9 Enzyme activities Key words

9

Calcareous soil

9

Introduction The application of composted municipal waste to agricultural land can improve soil fertility due to its high organic matter content (Chen and Avnimelech 1986; Giusquiani et al. 1988). Municipal waste composts, however, contain large quantities of heavy metals whose presence in soilg may negatively influence enzyme activities. The inhibiting effect of heavy metals such as Cd, Cr, Cu, Ni, Pb, and Zn on urease (Tabatabai 1977), amidase (Frankenberger and Tabatabai 1981), acid and alkaline phosphomonoesterase (Juma and Tabatabai 1977), arylsulphatase (A1-Khafaji and Tabatabai 1979), and L-asparaginase (Frankenberger and Tabatabai 1991 a) has been demonstrated. While the effect of sewage sludge containing heavy metals on soil enzyme activities has been investigated extensively

P.L. Giusquiani (~) 9 G. Gigliotti 9 D. Businelli Istituto di Chimica Agraria dell'Universit~t degli Studi di Perugia, Borgo XX Giugno, 72, 1-06121 Perugia, Italy

(Frankenberger et al. 1983; Reddy et al. 1987), studies on the effect of municipal waste compost on soil enzyme activities are limited. In experiments carried out under laboratory conditions, Perucci and Giusquiani (1990) and Perucci (1990) found that arylsulphatase, deaminase, phosphatase, protease, and urease activities were stimulated in a soil mixed with 25 g kg -1 of composted municipal waste. They ascribed this result to the addition of organic rfiatter which may compensate for the inhibitory effect of the heavy metals. In this paper we report the results of a 3-year field experiment on a soil cropped to corn (Zea mays L.) designed to evaluate the effect of normal and high municipal waste compost-loading rates (up to 270 t ha-1 over 3 years) on alkaline phosphomonoesterase, phosphodiesterase, aryfsulphatase, dehydrogenase, and L-asparaginase activities. These enzymes were chosen for their known sensitivity to heavy metals present in compost (Juma and Tabatabai 1977; A1-Khafaji and Tabatabai 1979; Frankenberger and Tabatabai 1991 a).

Materials and methods Field study The experimental field consisted of thirty-six 56.25-m2 plots cropped with corn (Zea mays L.), with amendments made in a completely random design with four replications per treatment. The amendments were all made in March, 60 days before seeding, and the compost was incorporated into the first 25-30 cm of soil by ploughing. Mineral fertilizer was added yearly by incorporating it jointly with the compost at rates of 300, 65.5 and 125 kg ha -1 of N, P, and K, respectively. One-year treatments were amended only in the ist year, and 3-year treatments were amended each year as follows. The treatments comprised (1) untreated control; (2) 1-year compost application at 30t ha 1; (3) 3-year compost application at 10t ha -~ year -1 for a total application of 30 t ha-l; (4) 3-year compost application at 30t ha -1 year -~ for a total application of 90t ha-J; (5) 3-year compost application at 90 t ha-1 year- ~ for a total application of 270 t ha-l; (6) untreated control + mineral fertilizer; (7) 1-year compost application at 30t ha -1 + mineral fertilizer;

258 (8) 3-year compost application at 10t ha -1 year i for a total application of 30 t ha -1 + mineral fertilizer; and (9) 1-year compost application at 90 t ha 1 + mineral fertilizer. Soil samples were collected from the surface layer (0-25 cm) in October at the end of the 3rd year. The moist soil was sieved (2 ram), and stored in plastic bags at 4 ~ in the dark if not used at once.

Soil and compost The calcareous soil, a clay-loam, mixed, mesic Fluventic Xerochrept typical of the mid-Tiber Valley, was located near Perugia, Italy. Urban waste compost was obtained from the Gesenu Municipal Waste Treatment Plant in Perugia, Italy. Compost was produced mechanically under aerobic conditions by fast fermentation (25 days) (Businelli et al. 1988). The analytical characteristics of the soil (Table 1) and the compost (Table 2) were determined according to standard procedures (Societa Italiana Scienza del Suolo 1985) except for total organic C and humified organic C (extracted with 0.1 M NaOH + 0.1 M Na4P207 according to Kononova 1966), which were determined by the Walkley and Black wet dichromate oxidation method (Nelson and Sommers 1982); cation exchange capacity was determined in BaC12 by the Gilman method (Rhoades 1982); available P was determined by the Olsen method (Olsen and Sommers 1982); NH~-N was extracted with 2 M KC1 and determined by steam distillation (Keeney and Nelson t982). The total heavy metal concentration was measured by atomic absorption spectrophotometry (Perkin Elmer Model 560) after the samples had been mineralized in concentrated HNO3-HC104 (2: 1). The available heavy metals were extracted by shaking 10g sample with 10ml 0.5M CH3COONH4 + ethylenediaminetetracetic acid at pH 4.65 on a reciprocating shaker. After 1 h, the samples were centrifuged, and the metals in the supernatant were determined with a Perkin Elmer Model 560 atomic absorption spectrophotometer.

Table 2 Compost characteristics. All data are expressed on a dry

basis (105 ~

and triplicates agreed to within 5% Elements (rag kg- 1)

Moisture (07o) Ash (07o) pH (HzO) Total organic C (%) Humified C (07o) Total N (%) C :N Total P (%) Total K (%) Total S (%)

29.5 44.2 7.6 27.4 11.7 1.9 14.4 0.9 1.1 0.5

Cd Cr Cu Mn Ni Pb Zn

Total

Available

5 81 240 640 52 750 647

2 6 104 480 9 592 338

These procedures involve the spectrophotometric determination (wavelength 400 nm) ofp-nitrophenol released after 1 h at 37 ~ by 1 g soil. Data are expressed as gg p-nitrophenol h -1 g-i dry weight soil. Dehydrogenase activity was determined by the method of Sparling (1981) which involves the spectrophotometric determination (wavelength 546 nm) of triphenyltetrazolium formazan (TTF) released after 18 h at 35 ~ by 3 g soil. Data are expressed as ~tg TTF h-1 g-i of dry weight soil. L-asparaginase (EC 3.5.1.1) activity was assayed by the method of Frankenberger and Tabatabai (1991b). This procedure involves the determination of NH2 released by steam distillation, as described by Keeney and Nelson (1982) after 2 h of incubation at 37 ~ with 5 g soil. Data are expressed as ~tg NH~- 2 h -1 g-1 dry weight soil.

Statistical analysis Enzyme activities Alkaline phosphomonoesterase (EC 3.1.3.1), phosphodiesterase (EC 3.1.4), and arylsulphatase (EC 3.1.6.1) activities were assayed with the methods of Eivazi and Tabatabai (1977), Browman and Tabatabai (1978), and Tabatabai and Bremner (1970), respectively.

Analysis of variance was used to analyse the data. Separation between average values was performed by calculating both linear and quadratic components and Fisher's least significant difference (Little and Jackson Hills 1978).

Results and discussion Table 1 Soil characteristics. All data are expressed on a dry basis

(i05 ~ and triplicates agreed to within 5070. (CEC Cation exchange capacity) Available Cd value represents the limit of the sensitivity of the method Elements (rag kg- 1)

pH (H20) CaCO 3 (070) CEC (mEq 100g -1) Bulk density (g cm- 3) Sand (%) Silt (%) Clay (%)

8.3 14 17 1.5 30.0 41.7 28.3

Texture

Clay loam

Total organic C (%) Humified C (%) Total N (%) C:N

0.76 0.30 0.06 12.6

P K Cd Cr Cu Mn Ni Pb Zn

Total

Available

571 7269 1 31 34 I650 64 81 68

8.8 157