Evaluation for the heavy metal risk in fine particulate matter from the perspective of urban energy and industrial structure in China: A meta-analysis

The distribution of the heavy metals (HMs) in fine particulate matter (PM2.5) with the evolution of the urban industrial structure is attracting much attention in developing countries. In this study, a meta-analysis was conducted to re-evaluate the pollution by 7 HMs (Pb, Cd, As, Cu, Mn, Cr and Ni) in the PM2.5 from 14 main cities in China. The standard mean difference (SMD) was served as the effect size. The most severe pollution by Pb, Cd, As, Cu, Mn, Cr and Ni was found in Foshan, Jinan, Wuhan, Foshan, Xi'an, Jinan and Shenzhen, respectively. The SMD5 of each HM from the 14 cities were merged using the random-effect model, indicating that As was the HM causing the most pollution, followed by Mn, Pb, Cd, Ni, Cu and Cr. The HM SMD5 as pollution indices were connected to city factors (energy, industry, traffic and environmental policy) using principal component analysis (PCA). General emission sources for HMs were assessed on the city scale, and it was concluded that coal consumption was still the main source for Pb, Cd, As, Cu and Mn pollution but electronic manufacturing industries were new sources responsible for Cr and Ni pollution. Thereinto, electronic manufacturing affected Ni pollution strongly, which was supported by the significance of the meta-regression analysis and the chemical speciation of Ni in PM2.5 compared to electronic waste. Thus, coal combustion mainly contributed to atmospheric HM pollution but there were also contributions from electronic manufacturing. Our results provide a novel method to assess the source and risk of atmospheric HMs accompanying urban industrial changes. (C) 2019 Elsevier Ltd. All rights reserved.