Size distribution and source of heavy metals in particulate matter on the lead and zinc smelting affected area

In order to understand the size distribution and the main kind of heavy metals in particulate matter on the lead and zinc smelting affected area, particulate matter （PM） and the source samples were collected in Zhuzhou, Hunan Province from December 2011 to January 2012 and the results were discussed and interpreted. Atmospheric particles were collected with different sizes by a cascade impactor. The concentrations of heavy metals in atmospheric particles of different sizes, collected from the air and from factories, were measured using an inductively coupled plasma mass spectrometry （ICP-MS）. The results indicated that the average concentration of PM, chromium （Cr）, arsenic （As）, cadmium （Cd） and lead （Pb） in PM was 177.3 ± 33.2 μg/m^3, 37.3 ± 8.8 ng/m^3, 17.3 ± 8.1 ng/m^3, 4.8 ± 3.1 ng/m^3 and 141.6 ± 49.1 ng/m^3, respectively. The size distribution of PM displayed a bimodal distribution; the maximum PM size distribution was at 1.1-2.1 μm, followed by 9-10 μm. The size distribution of As, cd and Pb in PM was similar to the distribution of the PM mass, with peaks observed at the range of 1.1-2.1 μm and 9-10 μm ranges while for Cr, only a single-mode at 4.7-5.8 μm was observed. PM （64.7%, As （72.5%）, cd （72.2%） and Pb （75.8%） were associated with the fine mode below 2.1 μm, respectively, while Cr （46.6%） was associated with the coarse mode. The size distribution characteristics, enrichment factor, correlation coefficient values, source information and the analysis of source samples showed that As, Cd and Pb in PM were the typical heavy metal in lead and zinc smelting affected areas, which originated mainly from lead and zinc smelting sources.

A practical method for identifying key factors in the distribution and formation of heavy metal pollution at a smelting site

Smelting activities are the main pathway for the anthropogenic release of heavy metals(HMs)into the soil-groundwater environment.It is vital to identify the factors affecting HMs pollution to better prevent and manage soil pollution.The present study conducted a comprehensive investigation of HMs in soil from a large abandoned Zn smelting site.An integrated approach was proposed to classify and quantify the factors affecting HMs pollution in the site.Besides,the quantitative relationship between hydrogeological characteristics,pollution transmission pathways,smelting activities and HMs pollutionwas established.Results showed that the soils were highly contaminated by HMs with a pollution index trend of As>Zn>Cd>Pb>Hg.In identifying the pollution hotspots,we conclude that the pollution hotspots of Pb,As,Cd,and Hg present a concentrated distribution pattern.Geo-detector method results showed that the dominant driving factors for HMs distribution and accumulation were the potential pollution source and soil permeability.Additionally,the main drivers are variable for different HMs,and the interaction among factors also enhanced soil HMs contamination.Our analysis illustrates how the confounding influences from complex environmental factors can be distilled to identify key factors in pollution formation to guide future remediation strategies.