Evaluation and Source Analysis of Heavy Metal Pollution in Sediments of the Yellow River Basin Based on Monte Carlo Simulation and PMF Model

Abstract

As sediment is an essential component of rivers, the enrichment of heavy metals in sediment presents a serious threat to the aquatic environment. Many industrial cities are located along the Yellow River, and heavy metal pollution is a prominent problem in these areas. Thus, the study of heavy metal pollution in sediments of the Yellow River basin is of vital significance to the safety of the Yellow River basin ecosystem. In this study, we collected data on the concentrations of heavy metals (Pb, Cd, Cr, As, Zn, Cu, Ni, and Hg) in the sediments of the Yellow River basin from 2000 to 2020. We first analyzed the spatial distribution characteristics of heavy metals based on descriptive statistics and geostatistics and then used the Monte Carlo method to evaluate the probability of the ground accumulation index(Igeo), potential ecological risk, and toxicity units. Finally, the number of pollution sources and their contribution rates were determined by combining the positive definite matrix factor (PMF) decomposition model and Pearson correlation analysis. It was found that the mean values of ω(Pb), ω(As), ω(Zn), ω(Ni), ω(Cu), ω(Hg), ω(Cr), and ω(Cd) in the Yellow River basin sediments were 26.92, 11.78, 87.17, 31.13, 24.96, 0.07, 73.36, and 0.58 mg·kg-1, which exceeded the mean soil background values in the Yellow River basin provinces by 1.27, 1.08, 1.26, 1.05, 1.09, 2.32, 1.14, and 5.95 times, respectively, among which Cd exceeded the standard by the largest factor and should be taken seriously. The Igeo was ranked as Cd>Hg>Cr>Cu>Pb>Zn>As>Ni, and Cd and Hg showed medium-severe pollution. The proportions of heavy ecological risk in sediments in the upper, middle, and lower reaches of the Yellow River basin were 18.6%, 15.7%, and 7.1%, respectively, with a decreasing trend. Heavy metals in the sediments of the Yellow River basin were in a low-toxicity state. The PMF-Pearson correlation analysis showed that the four sources of heavy metals in the Yellow River basin sediments were mining sources (42.2%), natural activities (38.3%), agricultural activities (11.6%), and electroplating wastewater (7.9%). The results of this study can provide a basis for developing relevant pollution prevention and control measures in the Yellow River basin.