Ecological risk assessment and source identification of heavy metals in the sediments of the Danjiang River Basin: A quantitative method combining multivariate analysis and the APCS-MLR model

Abstract

The heavy metal content in river sediment is a sensitive indicator of pollution in aquatic ecosystems and plays a key role in understanding the risks, characteristics, and sources of heavy metal pollution in a region. This study combined traditional assessment methods with the Nemerow integrated risk index (NIRI), which is improved based on the potential ecological risk index (RI) and the Nemerow integrated pollution index (NIPI), to evaluate the pollution level of sediment in the Danjiang River. Based on principal component analysis (PCA), the absolute principal component score-multiple linear regression (APCS-MLR) model was employed to analyze the contribution of pollution sources. The study results showed that the average concentrations of most heavy metals exceeded their corresponding background values, and the distribution of heavy metal content was significantly influenced by human activities. The degree of pollution varied among the sampling sites, and the results of NIRI on the spatial distribution and severity of contamination are generally consistent with other assessment indicators, providing a more detailed and comprehensive delineation. The results of the multivariate statistical analysis indicate that Cu, Zn, Pb, and As mainly originated from natural sources, Cd and Ni primarily came from mixed sources such as agriculture and mining, while Cr was mainly associated with industrial activities. The APCS-MLR model results further confirm with high confidence that the sources of heavy metals in the sediments of the study area are complex, predominantly influenced by natural processes such as weathering and erosion. As the water source for the Middle Route of the South-to-North Water Diversion Project, the safety of the Danjiang River’s aquatic ecosystem is crucial for the health of nearly 100 million people in China. These findings provide an important foundation for Danjiang River water resource protection and offer a reference for ecological security and pollution prevention in other rivers.