Physicochemical properties and heavy metal pollution characteristics and correlation analysis of sludge landfill

Abstract

ABSTRACT Heavy metal content and speciation of sludge, physicochemical properties of sludge, and the correlation between heavy metal content and speciations were investigated in this work. Results demonstrated that organic matter content of sludge ranged from 158.4 to 474.5 g kg−1, total nitrogen content from 9.95 to 27.45 g kg−1, total phosphorus content from 22.72 to 41.45 g kg−1, and total potassium content from 5.04 to 11.20 g kg−1. The sludge contains high content of organic matter, phosphorus and potassium and low content of nitrogen, it indicated that the sludge has a big prospect of agricultural use, and it could improve and increase soil fertility. Cu and Zn content exceed the agricultural use standard. Heavy metal speciations analysis indicated that Cu mainly exists in oxidizable speciation; Zn and Cd mainly exist in exchangeable and reducible speciation; Mn and Pb mainly exist in residual speciation; Cr, Ni, As and Hg mainly exist in oxidisable and residual speciations. These results indicated that Zn and Cd migration and bioavailability are strong in the environment, whereas Cu, Cr, Ni, As and Hg are weak. Mn and Pb are most stable in the sludge in these heavy metals. The correlation analysis indicated that heavy metal content and physicochemical properties obtained a positive correlation, such as with the heavy metal content, and total carbon, total nitrogen, ammonia nitrogen content obtained a positive correlation with heavy metal content, heavy metal had the same source and synergistic effect, and heavy metal content obtained a positive correlation with speciation in the sludge sample.