EXTRACTION OF HEAVY METALS IN A SEWAGE SLUDGE-TREATED LATOSOL
Abstract:
<p align="justify"> The presence of heavy metals is one of the main hazards against the use of sewage sludge in agronomy. In a field experiment applications of sewage sludge in medium-textured Dark Red Latisol (DRL) were evaluated by the extraction of essential or non-essential metals with a DTPA extractor. The experimental design consisted of randomized blocks subdivided into sections of 6 treatments of sewage sludge (0, 6, 20, 40, 60 and 80 t ha<sup>-1</sup>) during the first year and (0, 6, 20, 40, 60 and 80 t ha<sup>-1</sup>) during the second year. The experiment had 4 replications and 5 soil collection periods (0, 30, 60, 90, and 120 days of sludge incorporation). Sewage sludge was applied at a mean depth of 0-20 cm. Soil sampling was undertaken during the periods of sludge incorporation so that the elements available in the soil in different doses could be evaluated Soil samples were analyzed as to fertility level. Concentrations of the metals Cu, Zn, Cd, Ni, Co, Pb, and Cr were determined by atomic absorption in DTPA extractor solution. Concentrations of Cd, Ni, Co, Pb, and Cr were not detected since values were lower than the detection limit of each. Application of sewage sludge increased Cation Exchange Capacity (CEC) and there was an initial pH variation, albeit the latter returned concentration to its original level. Owing to the repetition of applied sludge, Cu and Zn rates in soil samples gradually increased during the two agricultural years caused by an increase in the doses of applied sewage sludge. </p>
<p align="justify"> The presence of heavy metals is one of the main hazards against the use of sewage sludge in agronomy. In a field experiment applications of sewage sludge in medium-textured Dark Red Latisol (DRL) were evaluated by the extraction of essential or non-essential metals with a DTPA extractor. The experimental design consisted of randomized blocks subdivided into sections of 6 treatments of sewage sludge (0, 6, 20, 40, 60 and 80 t ha<sup>-1</sup>) during the first year and (0, 6, 20, 40, 60 and 80 t ha<sup>-1</sup>) during the second year. The experiment had 4 replications and 5 soil collection periods (0, 30, 60, 90, and 120 days of sludge incorporation). Sewage sludge was applied at a mean depth of 0-20 cm. Soil sampling was undertaken during the periods of sludge incorporation so that the elements available in the soil in different doses could be evaluated Soil samples were analyzed as to fertility level. Concentrations of the metals Cu, Zn, Cd, Ni, Co, Pb, and Cr were determined by atomic absorption in DTPA extractor solution. Concentrations of Cd, Ni, Co, Pb, and Cr were not detected since values were lower than the detection limit of each. Application of sewage sludge increased Cation Exchange Capacity (CEC) and there was an initial pH variation, albeit the latter returned concentration to its original level. Owing to the repetition of applied sludge, Cu and Zn rates in soil samples gradually increased during the two agricultural years caused by an increase in the doses of applied sewage sludge. </p>
DOI: 10.48141/SBJCHEM.v13.n13.2005.17_2005.pdf
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