汾河下游河岸带土壤中重金属污染特征评价及污染源分析

[Objective] This study aims to understand the pollution characteristics and sources of heavy metals in the riparian soil of the lower reaches of the Fenhe River. [Methods] We collected 32 soil samples from 8 sections in the lower reaches of the Fenhe River and analyzed the content and distribution characteristics of heavy metals. The degree of heavy metal pollution and potential ecological risks were evaluated using the single-factor pollution index method and the potential ecological risk index method. The sources of heavy metals were analyzed through principal component analysis (PCA) and positive matrix factorization (PMF). [Results] 1) The content of heavy metals in the riparian soils of the lower reaches of the Fenhe River was generally low, but the enrichment effects of Pb and Hg were significant. The points with higher contents of Cu, Zn, Cr, Pb and Hg were mainly distributed in urban suburbs and the industrial areas concentrated along the riverbanks. The content of heavy metals in the Yellow River estuary area was relatively low. 2) The potential ecological risk index (PERI) was the highest downstream of Linfen City, at river confluences, and in Hejin City. Hg and Pb were at moderate-severe and moderate ecological risk respectively. This may be affected by the emission of Hg vapor from coal-fired power plants and coking plants downstream of Linfen City and Hejin City, as well as the sedimentation of smoke dust from lead smelters. The river confluences were areas where substances precipitated and accumulated, which was conducive to the enrichment of heavy metals. Industrial parks were scattered in areas such as Xiangfen County and Jishan County, resulting in a higher content of heavy metals in the middle of the lower reaches than in areas flowing into the Yellow River. In the areas with moderate ecological risks of heavy metals Hg and Pb, the contribution rates of Hg and Pb were 54.92% and 31.28%, respectively, indicating that Hg and Pb were the key elements for controlling soil heavy metal pollution in the lower reaches of the Fenhe River. 3) The correlation analysis results among heavy metals showed that there was a significant correlation between Zn and Pb, with a correlation coefficient of 0.671, indicating the influence of human activities on heavy metals in the soil. The high content of Pb in the soil may be caused by the waste gas and waste residue from surrounding industrial and mining enterprises. Dust and wastewater from human activities also caused Zn to enter the soil. The results showed that agricultural production was an important source of Zn and Pb. The unreasonable use of chemical fertilizers and pesticides for agricultural irrigation in the lower reaches of the Fenhe River led to the long-term accumulation of Zn and Pb in the soil, and the exhaust emissions from agricultural machinery also caused the accumulation of Pb in the soil. The dust and waste gas from mining, smelting, and electroplating production of minerals in the study area were deposited into the soil after rainfall, resulting in an increase in the contents of Zn and Pb in the soil. 4) According to PMF simulation, the main source of Hg was industrial production. Cu in the soil had multiple sources, including industrial production, agricultural activities, and transportation. Cr was relatively stable and less affected by human activities. The changes in Cr content were mainly influenced by soil parent materials and geological activities. [Conclusion] In summary, the main sources of heavy metal pollution in the soil along the lower reaches of the Fenhe River are human activities and industrial production. Controlling heavy metal sources at the origin can gradually reduce the heavy metal pollution in basin soils. At the same time, it can also reduce the heavy metal content in the tributary basins of the Yellow River, which is conducive to the overall ecological protection of the Yellow River.