Scientific registration number: 2271 Symposium n o : 25 Presentation : poster. OLIVEIRA Fernando Carvalho (2) ; MATTIAZZO Maria Emilia (2)

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1 Scientific registration number: 2271 Symposium n o : 25 Presentation : poster Copper, Nickel and Zinc availability to corn plants in acid soils amended with sewage sludge (1) Disponibilité en cuivre, en nickel et en zinc pour le maï s de sols acides amendés avec des boues de station d épuration OLIVEIRA Fernando Carvalho (2) ; MATTIAZZO Maria Emilia (2) (1) Research project sponsored by FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) (2) Escola Superior de Agricultura «Luiz de Queiróz»/ Universidade de São Paulo/ CP 9, , Piracicaba/São Paulo/Brazil Introduction Soils under tropical climate are generally acids and poor in organic matter and this way sewage sludge addition to these soils is a practice to be considered. Besides the benefits of the organic matter present in the sludge it also must be considered the presence of trace metals in this material. The availability to plants of trace elements and consequently its entrance in food chain has been an environmental concern about the use of sewage sludge on acid soils (King & Hajjar, 1990; Kuo, 1990; Xue & Harrison, 1991; Smith, 1994). The plant ability in absorbing these elements is, according Juste and Solda (1985), also dependent on the plant growing period, the average soil temperature and the interactions between the several elements that can be present. The estimate of this availability through the use of chemical extractants has been studied by several authors (Leschber et al 1985; Ure, 1990) but there is not an agreement on this matter. This experiment was made in order to have information on heavy metals availability to corn plants and ways to make an estimate of it considering that the use of sewage sludge on Brazilian acid soils is a practice to be adopted in a coming future. Material and Methods The soil samples used in the experiment were collected from the top layer soil (0-0.20m) of a sugarcane region in São Paulo State/ SP/ Brazil and they were classified as a Typic Quartzipsamment (sandy soil) and Typic Haplorthox (clay soil). The collected soil samples, after dried and sieved (4 mm sieve), were separated in two portions, in one of them it was added 0,1 mol L -1 sulfuric acid in order to decrease the soil ph in one unit. The amount of acid used was determined in previous studies (Oliveira, 1995). The 1

2 acidified soil samples were dried and sieved again. Some chemical characteristics of the soils (with and without the acid sulfuric addition) used in the experiment are shown on Table 1. Table 1 - Chemical properties of the soils used in the experiment. Soils Sandy ph C org P K Ca Mg H+Al Al (CaCl 2) g dm -3 mg dm -3...(mmol c dm -3 ) Clay (1) The soils with lower ph value were treated with sulfuric acid. The sludge used in the experiment resulted from an anaerobic and sludge-activated process treatment of raw sludge from the city of São Paulo. Some chemical analysis results of the sludge made according method described in Eaton et al. (1995) are shown in Table 2. Table 2 - Chemical analysis of the sewage sludge used in the experiment. ph (in water, ratio 1 : 2.5) Organic Carbon (g kg -1 ) Total N (g kg -1 ) Total P (g kg -1 ) 7.78 Total K (g kg -1 ) 1.11 Total Ca (g kg -1 ) Total Mg (g kg -1 ) 2.96 Total S (g kg -1 ) Total Fe (g kg -1 ) Total Cu (mg kg -1 ) Total Ni (mg kg Total Zn (mg kg -1 ) C : N ratio 9.73 (*) Data referred to the dry material with the exception of ph. The experiment was conducted in pots having a polyethylene hose at the bottom that drove the soil percolates back to the pots. The amount of each soil placed in the pots was: 4.0 kg for the sandy soil and 3.8 kg for the clay soil. Sewage sludge was added to the soils at rates corresponding to 0; 13.5; 27.0 and 40.5 Mg ha -1 in a dry weight basis (0; 50; 100; 150 Mg ha -1 in a wet weight basis). In the check treatments (no sludge added) soil was incubated with CaO in order to have a ph level equivalent to the treatments with the addition of sludge. The amount of CaO was determined in previous incubation studies (Oliveira, 1995). All the pots were watered until 70% of the soil water holding capacity. After this first addition, water was replaced periodically. The treatments were made with 3 replications. 2

3 After an incubation period of 63 days, the soils were sampled and analyzed for Cu, Ni and Zn using the extractants: solution 0.05 mol L -1 CaCl 2 ; DTPA and solution 0.1mol L -1 HCl. In all extracts, the metals were determined by atomic absorption spectroscopy. The methods used for the extraction are shown in Table 3. Table 3 - Methods used for the metals extraction. Extractants Soil : extractant ratio Extraction time Methodology adapted from 0.1mol L -1 HCl 1:5 24 h Page et al. (1982) 0.05 mol L -1 CaCl 2 1:5 24 h Sauerbeck & Styperek (1985) 0.05 mol L -1 DTPA 1:5 24 h Lindsay & Norvell (1978) After the sampling, the soils were seeded with two seeds per pot with corn (Zea mays, L. cv. Cargill 901). At the end of a growth period of 55 days the plants were harvested, washed with 0.1mol L -1 HCl and deionized water, dried, weighed, grinned and analyzed for the metals Cu, Zn and Ni following nitric-percloric acid digestion and determination of the metals by ICP. The statistics for these soil and plant data were made considering a factorial scheme 2X2X4 for soil type, ph before incubation period and sludge level added, using a SAS program (SAS Institute Inc., 1994). Results and Discussion The amounts of Cu, Ni and Zn removed by the extractants after the incubation period are shown in Table 4. The statistics for these data appears on Table 5. The results related to the extractor CaCl 2 are not presented in this Table because they were bellow the detection limit level of the analytical method used for the analysis. Since, as can be seen ahead, the metals added by sludge showed plant availability it means that this extractor was not efficient in anticipate the metals plant availability in these types of soils. 3

4 Table 4 - Amounts of Cu, Ni and Zn removed from soils by the extractants. ph at Sludge Copper Nickel Zinc Soils Sampling Addition...mg extracted... (CaCl 2) (Mg há -1 ) HCl DTPA HCl DTPA HCl DTPA Sandy Clay Copper added to treatments by sludge : 0; 9.77; and mg pot -1. Nickel added to treatments by sludge: 0; 4.85; 9.71 and mg pot -1. Zinc added to treatments by sludge : 0; 32.05; and mg pot bellow the method detection limit Table 5 - Statistics for the chemical extractants used extractable elements ( mg ) Source of variation Copper Nickel Zinc HCl DTPA HCl DTPA HCl DTPA Soils * * ns * * ns ph Ns * ns ** ** ** Sludge addition ** * ** ** ** ** Interactions Soils x ph Ns ns * ** ** ** Soils x Addition Ns ns ns ns ns ns ph x Addition Ns ns ns * ** ** Soils x ph x Addition Ns ns ns ** * * LSD 5% (Soils) LSD 5% (ph) LSD 5% (Addition) LSD 5% (ph in Soils) LSD 5% (Soils in Addition) LSD 5% (Addition in ph) LSD 5%(Addition in soils in ph) CV % *, significant at 5%; **, significant at 1%; ns, not significant. Considering the amounts removed by DTPA and HCl it can be noticed that most part of the added metal was removed by the extractants and these amounts depend on the soil 4

5 ph at the moment of the sampling being Zn the element more sensitive to the ph increase. The dry matter produced in each treatment and the results of Cu, Zn and Ni analysis in plant material are shown in Table 6 and the statistics for these data are shown in Table 7. Examining these tables it can be noticed that dry matter production was significant different depending on the sludge level added. In treatments with lower initial ph the plant showed less dry matter production mainly in the sandy soil. The metals concentration in plants showed highly significant differences only in the highest level of sewage sludge added, but even in this condition no symptoms of metal toxicity was noticed. Considering the total amount of the metal absorbed by plants can be seen its increase with the increase of the amount of sludge added. Although the increase on metal availability added to soils by sludge it was always corresponding to less than 1% of the addition. The small crop uptake of metals by crops was observed Chang et al (1987) and Petruzzelli et al (1989). It also can be noticed differences in the Zn/Cu absorption rate, showing that with the increase of the amount of Cu in soils there was a corresponding decrease on Zn absorption. Table 6. Dry matter production, concentration of Cu, Ni and Zn in plant material and total amounts of these metals absorbed by the corn plants. Sludge ph at Plant Dry Copper Nickel Zinc Soils Addition planting Wt (Mg há -1 ) (CaCl 2) (g pot -1 ) (mg kg -1 ) (µg) (mg kg -1 ) (µg) (mg kg -1 ) (µg) Sandy 0 * Clay 0 *

6 Table 7. Statistics for plant dry weight and content of Cu, Ni and Zn expressed in concentration and total amount absorbed in each treatment. Source of variation Plant dry wt Copper Nickel Zinc (g pot -1 ) (mg kg - (µg) (mg kg - (µg) (mg kg - (µg) 1 ) Soils Ns ** ** ns ns * ns ph ** ns ns ns ns ** ** Sludge addition ** ** ** ** ** ** ** Interactions Soils x ph Ns ns ** ns ns ** ns Soils x Addition Ns ** ** ns ns * ** ph x Addition Ns ** * ns ns * * Soils x ph x Addition Ns ** * ns ns ** * LSD 5% (Soils) LSD 5% (ph) LSD 5% (Addition) LSD 5% (ph in Soils) LSD 5% (Soils in Addition) LSD 5% (Addition in ph) LSD 5% (Addition in soils in ph) CV % *, significant at 5%; **, significant at 1%; ns, not significant. The correlations made between the metal level in plant and amount removed by DTPA and HCl are shown on Table 8. Examining this Table can be noticed the dependency of the extractors on the metal, on the soil, on the soil ph. No one single extractor can be used to estimate plant availability of trace elements. Table 8 -Regression equations for metals removed by the extractants and absorbed by plants. Interactions Soils Regression equation R 2 Copper x 0.1mol L -1 HCl Sandy *y = x 0.88 Copper x 0.1mol L -1 HCl Clay *y = x 0.88 Copper x 0.05mol L -1 DTPA Sandy *y = x 0.88 Copper x 0.05mol L -1 DTPA Clay **y = x 0.80 Nickel x 0.1mol L -1 HCl Sandy **y = x 0.85 Nickel x 0.1mol L -1 HCl Clay *y = x 0.58 Nickel x 0.05mol L -1 DTPA Sandy **y = x 0.85 Nickel x 0.05mol L -1 DTPA Clay **y = x 0.72 Zinc x 0.1mol L -1 HCl Sandy *y = x 0.67 Zinc x 0.1mol L -1 HCl Clay **y = x 0.85 Zinc x 0.05mol L -1 DTPA Sandy *y = x 0.61 Zinc x 0.05mol L -1 DTPA Clay **y = x 0.83 *, significant at 5%; **, significant at 1%. Conclusions In the sludge amended soils the plants showed a better growth than the plants in treatments with no sludge. Only when the applied rate was corresponding to 40.5 Mg ha -1, the levels of Cu, Ni and Zn were significantly different from the plants in 1 ) 1 ) 6

7 the no sludge treatments, but even in this condition the plants showed no symptoms of the metal toxicity. The amount of the metals absorbed by the plants was inferior to 1% of the added amount. The extractors used to evaluate the metals availability showed dependency on the metal and soil considered. Bibliography Eaton, A.D.; Clesceri, L.S.; Greenberg, A.E. Standards methods for the examination of water and wastewater. 19 ed. Washington, D.C., American Public Health Association, Chang, A.C.; Hinesly, T.D.; Bates, T.E.; Doner, H.E.; Dowdy, R.H.; Ryan, J.A.Effects of long term sludge application on accumulation of trace elements by crops. In: Page, A.C.; Logan, T.J.; Ryan, J.A. Land application of sludge. Chelsea, Lewis Publ., p Juste, C. & Solda, P. Factors influencing heavy metal availability in field experiments with sewage slugs In: Leschber, R.; Davies, R.D.; L Hermité, P. Chemical methods for assessing bioavailability metals in sludge and soils. London, Elsevier, p King, L.D. & Hajjar, L.M. The residual effect of sewage sludge on heavy metal content of tobacco and peanut. Journal Environmental Quality, Madison, 19: , Kuo, S. Cadmium buffering capacity and accumulation in Swiss chard in some sludge-amended soils. Soil Science Society of America Journal, Madison, 54: 86-91, Leschber, R.; Davies, R.D.; L Hermité, P. Chemical methods for assessing bioavailability metals in sludge and soils. London, Elsevier, p. Lindsay, W.L. & Norvell, W.A. Development of a DTPA soil test for zinc, iron, manganese and copper. Soil Science Society of America Journal, Madison, 42: 421-8, Oliveira, F.C. Metais pesados e formas nitrogenadas em solos tratados com lodo de esgoto. ESALQ/USP, p. (Dissertação de Mestrado) Page, A.L.; Miller, R.H.; Keeney, D.F. Methods of soil analysis 2 ed., Madison, ASA; SSSA, p. Petruzzelli, G; Lubrano, L.; Guidi, G. Uptake by corn and chemical extractability of heavy metals from a four year compost treated soil. Plant and Soil 116: Ure, A.M. Methods of analysis for heavy metals in soils. In: Alloway, B.J. ed. Heavy metals in soils. New York, John Wiley, p Sauerbeck, D.R. & Styperek, P. Evaluation of chemical methods for assessing the Cd and Zn availability from different soils and sources. In: Leschber, R.; Davies, R.D.; 7

8 L Hermité, P. Chemical methods for assessing bioavailability metals in sludge and soils. London, Elsevier, p Xue, Q., and Harrison, H.C. Effect of soil zinc, ph, and cultivar on cadmium uptake in leaf lettuce (Lactuta sativa L. Var. Crispa). Communications in Soil Science and Plant Analysis, New York, 22(9/10): , SAS Institute, Inc JMP Statistic and Graphics Guide Version SAS Institute, Inc., Cary, N.C. Smith, S.R. Effect of soil ph on availability to crops of metals in sewage sludge-treated soils. I. Nickel copper and zinc uptake and toxicity to ryegrass. Environmental Pollution, Essex, 85(3), , Key words: heavy metals, plant availability, extractants, acid soils. Mots clés : métaux lourds, biodisponibilité, extracteur, sol acide 8