Spatial distribution, pollution levels, and source identification of heavy metals in wetlands of Suzhou Industrial Park, China

As one of the earliest national demonstration ecological industrial parks (EIPs) in China, Suzhou Industrial Park (SIP) is developed on the principles of material and energy recycling and cleaner productions since 1994 when it was established. Therefore, assessing the pollution level and distribution produced by different industries and taking corresponding countermeasures to deal with the pollution have become a challenge for all the enterprises of SIP. Few studies have been conducted to determine the heavy metal pollution condition of SIP. This research is conducted to yield valuable information on the spatial distribution, possible sources and pollution levels of heavy metals in the wetlands of SIP. For these purposes, concentrations of 12 heavy metals are analysed in sediments from wetlands in SIP. To reveal the contamination level of SIP, geo-accumulation index (I-geo) and enrichment factor (EF) are used in this study and results reflect that anthropogenic Ga, Pb and Sb are the heavy metal contaminants spreading throughout the wetlands of SIP. This may be explained as the result of atmospheric deposition and contaminated runoff associated with human activities. Multivariate statistical analyses, such as Pearson's correlation matrix and principal component analysis, reveal that sewage and runoff are sources of heavy metals to the wetlands of SIP, so is continuous discharge from the combined sewer overflow. Additionally, the non-point source of heavy metal contamination, such as industrial fly ash, traffic emissions and agricultural pollution, cannot be neglected. Therefore, more efforts should be made to create stricter environmental regulations according to the national EIP development guidelines.