Dynamic change in particulate palladium concentrations in a mangrove wetland water environment and its mechanism in Dongzhai Harbor, China.

Palladium (Pd), in platinum group elements (PGEs), is widely used as a catalyst in vehicle exhaust catalytic converters (VECs). The cumulative level of Pd in the environment is growing rapidly, and the potential threat to human health is increasing. In this paper, the mangrove wetland in Dongzhai Harbor, Hainan Province, China, was taken as the research area for the collection of water samples. The particulate Pd was determined by microwave digestion and inductively coupled plasma-mass spectrometry (ICP-MS). The particulate Pd showed a decreasing trend from the estuary to offshore. The land origin of Pd in the mangrove wetland was explained. The Pd concentrations in the suspended state were lower in the wet season than in the dry season. Tide had an obvious influence on particulate Pd. The concentrations of particulate Pd at spring tide were higher than those at neap tide. The concentrations of particulate Pd at ebb tide were higher than those at flood tide. The rainfall intensity also had a strong influence on the particulate Pd. The particulate Pd increased after moderate and light rain but decreased after heavy rain. The pH, redox potential(Eh), and Cl had little effect on particulate Pd in the water environment. This study is helpful for understanding the environmental geochemical characteristics of Pd in mangrove wetlands and provides a theoretical basis for the study of Pd in urban coastal mangrove environment.