Temporal and Spatial Characteristics of Heavy Metals in Suspended Particulate Matter in Pearl River Estuary and Its Influencing Factors

Simultaneous sampling and observation were conducted at 16 stations in the Pearl River Estuary, and the temporal and spatial characteristics of the contents of six heavy metals (Cr, Cu, Zn, Pb, As, and Cd) were analyzed. The influencing factors of suspended particulate matter (SPM) were explored through the combined results of our statistical analyses. With the influence of discharge, temperature and particle size, the content of heavy metals in the dry season is higher than that in flood season. Regarding the estuary filter, the content of heavy metals in the estuary segment was lower than that in the far mouth segment, which was principally caused by the difference in salinity and sediment concentration between the two segments during the dry season. Both the sediment quality standard and enrichment factor methods were used to evaluate heavy metals. The results showed that the threat of heavy metals in the dry season was stronger than that in the flood season. As and Zn were more harmful to the ecological risk, while Cd, As, and Zn were the more abundant pollutants in the Pearl River Estuary. Heavy metal pollution was more severe in the far mouth segment. The degree of pollution for Cu, Zn, As, and Cd- which are classified as heavy pollution, severe to extremely heavy pollution, severe heavy pollution, and extremely heavy pollution, respectively-in the Beijiang River were higher compared to the Xijiang River and Dongjiang River. The pollution level of the six heavy metals in the four eastern outlets and four western outlets were similar, and the most serious pollution in Humen may be related to local industrial development. The source of heavy metals in SPM of the Pearl River Estuary is related to geological background, industry, and the mining area.