Source identification and spatial variability of nitrogen, phosphorus, and selected heavy metals in surface water and sediment in the riverine systems of a peri-urban interface

This study was conducted, using an elaborate sampling activity of surface water and sediment within an industrially developed periurban interface with a riverine system in Wuxi, Taihu Lake area, China, to address the following objectives: (i) to identify possible sources of selected nutrients such as N and P, and heavy metals such as Cu, Zn, Pb, Cr, and Cd in surface water and sediments, and (ii) to determine the spatial variability of these elements around the source areas. The results showed that concentrations of N and P in the surface water and Cu, Zn, Cr, and Pb in most of sediments had exceeded trigger levels established by the nation, while all metal concentrations in surface water were still below the levels. The source identification of these pollutants in water and sediments in terms of their spatial distribution pattern and principal component analysis showed that: (i) Pb, N and organic carbon (OC) were closely related to the influence of urban runoff and domestic wastewater; (ii) Cu and Cr were related to the influence of industries; and (iii) P and Zn were related to the effect of both urban and industries. The results of this study showed that urbanization is the main contributor for N and P in the peri-urban interface instead of agricultural sources. The concentrations of N, P, Cu, Zn, Pb, and Cr in the sediment along the main river decreased with the distance away from the source area. The concentrations of these elements decreased to the background levels at about 4.5-5.5 km downstream of the source of origin.