Spatial distribution and contamination assessments of heavy metals in sediments of Wenzhou river network

In order to investigate the spatial distribution pattern and degree of heavy metal pollution in river network sediments of Wenzhou, 29 sediment samples were collected, and using atomic fluorescence spectrometry (AFS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) heavy metal concentration in the samples were analyzed. The Kriging interpolation map reflected the spatial distribution of heavy metal. Comprehensive geo-accumulation index based on the Nemerow index method was established to assess the pollution degree. Pearson correlation analysis method and principal component analysis method were employed in sources analysis. Results show that heavy metal concentration varies significantly at different sites. The area with highest Cd and Zn concentrations is the centralized urban and industrial area of the main stream of this river network, while the highest concentrations of As, Pb, Hg, Cu, Ni and Cr were found to be in machinery industrial park. Sediments are contaminated by Hg, Cd, Cu, Zn, Ni and Cr. The order of degree of contamination is as follows: machinery industrial park>urban areas of the main stream>Sanyang Wetland>outskirt and rural area>drinking water source area. Hg, Cd, Cu, Zn, Ni and Cr have similar pollution sources which are mainly anthropogenic sources.