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A Case Study of the Effects of Sewage Sludge Application on Soil Properties and Heavy Metal Availability in the Thessaloniki Plain (Greece)

Tziachris, P., Lekakis, E., Zambetoglou, K., Metaxa, I., Papadopoulos, F.
Waste and biomass valorization 2017 v.8 no.5 pp. 1803-1811
acid soils, bioavailability, cadmium, calcium, calcium carbonate, case studies, chromium, cobalt, copper, crops, ecotoxicology, electrical conductivity, exchangeable calcium, heavy metals, iron, lead, magnesium, manganese, nickel, nitrogen, nutrients, organic matter, pH, phytotoxicity, plant growth, plant nutrition, risk, sewage sludge, soil amendments, soil properties, wheat, zinc, Greece
The amended soils chemical properties as affected by the application of a single dose of sewage sludge were evaluated over a 1-year period. Three soil groups based on their pH values were examined. Data on pH, organic matter, CaCO₃, electrical conductivity, exchangeable Ca and Mg, concentration of nine metals (Cd, Co, Cr, Pb, Zn, Ni, Fe, Mn, Cu) and nutrients before the application of sewage sludge in 2013 and after the wheat growing period in 2014, were statistically analyzed. Results showed that the application of lime stabilized sewage sludge significantly increased the electrical conductivity, CaCO₃ and Mg in all soil groups as well as pH and Ca of acidic soils, while the organic matter was not affected. The levels of concentrations of most DTPA-extractable metals in soil, either decreased or remained the same as they were before the sludge application. Soil Zn was the only metal that increased in the acidic soil group, however in concentrations largely below ecotoxicological limits. It is concluded that the application of lime stabilized sewage sludge to soils may take place with no risk of increasing heavy metal bioavailability to phytotoxic levels. Further benefits to crops are provided by favoring pH conditions for plant growth in acidic soils and by improving plant nutrition via nitrogen addition.