Seasonal and spatial dynamics of trace elements in water and sediment from Pearl River Estuary, South China

In this study, spatial and seasonal dynamics of trace elements (Cu, Pb, Zn, Cd, As) in water and sediments were examined in the Pearl River Estuary (PRE), South China. The spatial variations of all the studied trace elements in sediments show the general decrease pattern from northwest to southeast side of the PRE, suggesting that the main sources of these trace elements may originate from terrestrial (rock and soil) weathering and human activities (e.g. agricultural, industrial and municipal wastewaters) via riverine inputs. The dissolved Cu, Pb, Cd, As, and Zn in PRE ranged from 0.34 to 3.26, 0.19 to 4.58, 0.0015 to 0.30, 0.16 to 8.18, 3.74 to 36.10 μg/L, respectively. There are obvious seasonal changes of dissolved trace elements in the PRE aquatic system. The maximum seasonal averages of all the dissolved trace elements excluding Zn were observed in summer, whereas dissolved Zn showed the minimum in this season. The overall spatial pattern of all the dissolved trace elements excluding Zn demonstrates decreasing trends from inshore to offshore, and the highest concentrations of dissolved Cu, Cd, As, and Zn appeared in the western part of PRE or the mouths of Pearl River, suggesting strong riverine and anthropogenic local inputs. PCA and correlation analysis show that the geochemical behavior of dissolved Cu and As are complicated and the dynamics of these two elements are controlled by various physicochemical parameters, whereas physicochemical parameters might play a relatively small role in the distributions of other studied trace elements.