Characterizing the Changes in the Source Apportionment of Metal in Surface Waters by an Integrated Approach

Based on long-term monitoring data of typical surface water from 1999 to 2016, this study evaluated the temporal, spatial, and source changes of seven trace metals. The results show that average concentrations of trace metals were Zn (248.61 mu g L-1) >> Mn (74.27 mu g L-1) > Ba (72.4 6 mu g L-1) > Al (44.11 mu g L-1) > As (6.36 mu g L-1) > Ni (3.29 mu g L-1) > Cd (2.98 mu g L-1). There is a decreasing trend in the concentrations of Al, Cd, Mn, Ni, and Zn. Pollution levels in the midstream are relatively higher than in the upstream and downstream. A wavelet analysis suggested that the Al and As contamination levels exhibited clear periodic oscillations. According to the source apportionment analysis, the pollution sources of A, B, and C periods were determined, among which historical mining, industrial, agricultural, and geological natural sources were the main contributors. Anthropogenic pollution sources during stage B accounted for the largest proportion, reaching 76.54%. Historical mining source emissions remained relatively stable (43.17, 34.99, and 40.83%), but the proportion remained at the highest level. The health risk assessment shows that there is no obvious health risk, and As and Cd have certain cancer risk.