Sources, Distribution Characteristics, and Risk Evaluation of Typical Heavy Metals in Sludge from Industrial Parks

Although pollution caused by heavy metals in sludge has recently attracted extensive attention, little is known about the distribution characteristics, potential ecological risks, and sources of heavy metals in sludge collected from industrial parks. In this study, we collected sludge from 89 centralized wastewater treatment plants in industrial parks, a certain city, and analyzed the content and related characteristics of eight heavy metals. The spatial distribution analysis of typical heavy metals showed relatively high contents of Cr, Ni, Cu, and Zn in the sludge in the main urban metropolitan area, which can be correlated with the degree of industrial development and human activities. The determined potential ecological risks (E _i ) were higher for Hg and Ni than for other heavy metals; the combined ecological risk value (RI) of the main urban metropolitan area was increased compared to other districts and counties. The analysis of heavy metal sources indicated that Cr, Cu, and Zn in the sludge originated from the same source, associated with the mechanical equipment manufacturing industry. Hg and Pb came from the same source and could be related to electroplating, chemical, and electronic manufacturing industries. The presented results provide a basis for studying the heavy metal pollution characteristics of sewage sludge.