Risk assessment and source analysis of heavy metal pollution in wetland sediments in the northern Yellow River Delta

The contents of Cu, Pb, Zn, Cr, Ni, Cd, As and Hg in 39 surface sediment samples collected in June 2021 from the northern wetland of the Yellow River Delta were determined, and the risk assessment and source analysis of heavy metal pollution in the sediments of the northern wetland of the Yellow River Delta were carried out. Results show that the average contents of eight heavy metal elements in the surface sediments of the wetland in the northern Yellow River Delta were in the order of Cr＞Zn＞Ni＞Pb＞Cu＞As＞Cd＞Hg, which were lower than the soil background values of Shandong Province except for As. The sediments were mainly sandy silt, and the spatial distribution characteristics of heavy metal elements are similar, which may be affected by the “grain size effect”. The cumulative index and potential ecological hazard index (RI) revealed that Cd and Hg were the main pollutants and important potential ecological risk factors in the study area. Correlation analysis and factor analysis showed that the sources of Cu, Pb, Zn, Cr, As, and Hg might be soil parent materials, industrial activities, and oilfield exploitation, and the sources of Ni and Cd might be from agricultural activities, aquaculture and oilfield exploitation. Cluster analysis showed that Cr could be placed into separate category. Through factor detection analysis, it was found that clay content, TOC and water content had a greater explanatory power on the RI, indicating that they had a greater impact on the RI value. The interaction detection analysis showed that the interaction of any two influencing factors resulted in two-factor enhancement or nonlinear enhancement, indicating that the complex environment aggravated the potential ecological hazards of wetlands. This study provided a scientific support for the control of heavy metal pollution in wetlands in the northern Yellow River Delta.