Pollution characteristics, spatial distributions, and source apportionment of heavy metals in cultivated soil in Lanzhou, China

For the purpose of pollution assessment, human health risk assessment and quantitative source apportionment of heavy metals in cultivated soils, a total of 382 cultivated soil samples were collected from cultivated of Lanzhou in September 2019. Various indices, including pollution index (PI), Nemerow integrated pollution index (NIPI) and potential ecological risk index (RI) were used to analyze the pollution levels caused by heavy metals. Human health risk assessment, geographic information system (GIS) and positive matrix factorization (PMF) receptor modeling were employed to analyze the human health risk and source of heavy metals. The results showed that mean concentrations of Hg exceeded the national soil pollution risk screening value (GB 15618–2018). Spatially, except Cr in the study area, Pb, Cd, As, Cu, Zn and Ni have high value in Chengguan and Qilihe. Hg has high values in study areas outside Chengguan, Anning and Qilihe. The Nemerow integrated pollution index showed that the moderate and severe samples sites were 37.70% and 3.66%, respectively. The potential ecological risk indicates that most of the sampling sites are moderate risks. According to the health risk assessment results, the carcinogenic and non-carcinogenic risks of heavy metals to the human body are insignificant. Based on positive matrix factorization, there are four main sources of eight heavy metals. Pb, Cd, Zn and Ni were attributed to traffic sources; Hg were closely related to agricultural activities and medical treatment; Cr, Cu and Ni originated from natural source, As was derived from industrial activity. In this study enhance understanding of the pollution levers of heavy metals in Lanzhou cultivated soils, and also serves as reference for pollution source apportionment in other regions.