Spatial distributions and risk assessments of nutrients and heavy metalsin sediments from an impounded lake of China's South-to-NorthWater Diversion Project.

The high-density distribution patterns of the nutrients (C, N, P) and heavy metals (Fe, Mg, Zn, Cr, Pb, Ni, Cu, Cd) in sediments from Lake Luoma, as well as their pollution status and ecological risks, were characterized, to comprehensively understand potential environmental impacts of inter-basin water transfers. TN, TP, and OM were measured from 162.50 to 4360.00 mg kg-1, 165.00 to 1302.50 mg kg-1, and 1% to 13%, which were primarily accumulated in the eastern, northwest, and western regions, respectively. A total of 8 heavy metals except for Fe generally exhibited a similar distribution pattern, reflected by a gradually decreasing trend from northwest to southeast region. The averaged concentrations of heavy metals decreased as follows: Fe > Mg > Zn > Cr > Pb > Ni > Cu > Cd. Comprehensive pollution risk assessments indicated that the sediments of Lake Luoma were heavily polluted by TN, OM, and Cd. Multivariate statistical analyses demonstrated that the main pollution sources of Zn and Ni were fertilizers and pesticides, Cd and Pb are mainly derived from industrial wastewater, and TN and OM may come from natural and agricultural factors. This research can provide data support for water pollution control and drinking water diversion management in the Lake Luoma basin.