[Multiproxy Comprehensive Analysis for Source Apportionment and Pollution of Heavy Metals in Urban Drinking-water Source Soils from the Lanzhou Reach of the Yellow River].

To elucidate the pollution characteristics and sources of heavy metals in the soil of drinking water sources in urban areas of the Yellow River Basin, the soil in the water source areas for urban drinking water in the Lanzhou section of the Yellow River was selected as the research object. The content characteristics of heavy metals, including As, Cd, Cr, Hg, and Pb, were analyzed. The pollution degree of heavy metals was quantified systematically using the geo-accumulation index, contamination factor, pollution load index, and improved Nemerow comprehensive pollution index. Correlation-clustering analysis, the positive matrix factorization （PMF） model, and the absolute principal component scores-multiple linear regression （APCS-MLR） model were jointly applied to quantitatively analyze the pollution sources and their contribution rates of heavy metals. The results indicated that： ① The soil in the water source areas for urban drinking water in Lanzhou was alkaline, and, with the exception of Cr, the average content of heavy metals in the soil, including As, Cd, Hg, and Pb, exceeded the background values of soil in Gansu Province. Particularly, Hg and Pb exhibited significant spatial distribution variations, indicative of strong anthropogenic influences. ② The overall pollution level of the water source area soil was mild, with Hg identified as the primary pollutant and localized pollution observed for As and Pb, whereas Cd and Cr showed no substantial contamination. ③ The enrichment of heavy metals in the water source area soil was influenced by a combination of industrial, traffic, coal combustion, and natural sources. The PMF model identified 41.40% as industrial-traffic sources, 32.92% as coal combustion sources, and 25.68% as natural-industrial sources. The APCS-MLR model distinguished 36.36% as industrial-traffic sources, 22.32% as coal-industrial sources, and 41.31% as natural sources. These findings provide a scientific basis for ensuring the health of soil in the water source areas and the safety of drinking water in the urban area of Lanzhou.