Based on the monitoring data of 18 river sections, this study investigated the spatiotemporal distribution, sources and ecological risks of 8 heavy metal ions in the upper reaches of Wujiang River, and analyzed the influence of dissolved organic matter (DOM) on the migration and distribution of heavy metals. The results showed that the overall content of heavy metals in the upper reaches of Wujiang River was low with significant seasonal variations, and the average concentrations of Cr, Fe, Co, Ni, Cu, As, Cd and Sb were 0.71, 19.20, 0.17, 1.09, 0.73, 0.65, 0.06 and 1.22 μg/L, respectively, which were all lower than the level of Class III of the Environmental Quality Standard for Surface Water. Principal component analysis revealed a homology among Cr, Fe, Co, Ni, Cd and Sb, primarily sourced from natural origins. Cu was additionally affected by industrial activities including electroplating, printing and dyeing, while as was partially originated from the application of pesticides and fertilizers. Heavy metals showed positive correlations with DOM and its fluorescent components C1–C4, indicating that DOM could promote the migration and enrichment of heavy metals in water. Cr, Fe, Co, Ni and Sb showed significant positive correlation with DOM characteristic parameters SUVA₂₅₄ and BIX, further confirming that DOM with higher aromaticity and biological reactivity showed higher metal affinities. The evaluation results of single factor and Nemerow comprehensive pollution index suggested that the pollution level of heavy metals in the upper reaches of the Wujiang River retained relatively low, rendering it an ideal source of drinking water. However, the potential ecological risks of heavy metals under the influence of DOM need more concern. 

the upper reaches of Wujiang River, heavy metals, dissolved organic matter (DOM), spatiotemporal distribution, source apportionment, risk assessment

基于乌江上游18个断面的监测数据, 对8种金属离子的时空分布、来源和生态风险进行分析, 并探究DOM对重金属迁移和分布特征的影响。结果表明, 乌江上游河段重金属含量整体上较低, 季节差异显著, Cr, Fe, Co, Ni, Cu, As, Cd和Sb的平均离子浓度分别为0.71, 19.20, 0.17, 1.09, 0.73, 0.65, 0.06和1.22 μg/L, 均低于国家地表水环境质量III类水质标准。主成分分析结果表明, Cr, Fe, Co, Ni, Cd和Sb存在同源性, 以自然来源为主, Cu还受到电镀、印染等工业活动的影响, As部分来源于农药和化肥的施用。重金属浓度与DOM及其荧光组分C1~C4正相关, 表明DOM对金属离子在水体中的迁移和富集具有促进作用。Cr, Fe, Co, Ni和Sb离子浓度与DOM特征参数SUVA₂₅₄及BIX显著正相关, 进一步证实DOM芳香度和生物活性越高, 与金属离子的结合能力越强。单因子和内梅罗综合污染指数评价结果表明, 乌江上游水体重金属污染水平较低, 可作为理想的饮用水源, 但应关注DOM影响下的重金属潜在生态风险。