Ecotoxicity assessment of soil irrigated with domestic wastewater using different extractions

Abstract

The toxicity of soil irrigated with treated domestic wastewater (site A) and untreated gray wastewater (site B) were investigated. Soil extracts were prepared using distilled water, acid solvent (0.1 mol·L−1 HCl), and organic solvent (acetone:petroleum ether: cyclohexane = 1:1:1) to understand the type of pollutants responsible for the ecotoxicity associated with wastewater irrigation. The soil toxicity was assessed using a luminescence inhibition assay with Vibrio fischeri for acute toxicity, a micronucleus assay with Vicia faba root tips and a single cell gel electrophoresis assay of mice lymphocytes for genotoxicity. The physicochemical properties and the heavy metal (HM) contents of the irrigated soil were also analyzed. The results indicated that the wastewater irrigation at site A had no effects on the soil properties. With the exception of Pb, Zn, Fe, and Mn, the accumulation of HMs (Cu, Ni, and Cr) occurred. However, the irrigation at site A did not result in obvious acute toxicity or genotoxicity in the soil. The soil properties changed greatly, and HMs (Cu, Ni, and Cr) accumulated in site B. There were significant increases in the acute toxic and genotoxic effects in the soils from site B. The ecotoxicity in site B came primarily from organic-extractable pollutants.