[Source Analysis and Risk Assessment of Heavy Metals and Fluoride Pollution in Soils of the Korla Oasis Area].

Abstract

To investigate the pollution status， pollution sources， and health risk of heavy metals and fluoride in soils of the Korla Oasis area， 6 180 soil samples were collected， and the content characteristics and spatial distributions of eight heavy metals （As， Cu， Cr， Pb， Hg， Ni， Zn， and Cd） and the non-metal F were determined and analyzed. The potential risk of heavy metals and fluoride and the presence of coldspot and hotspot areas were assessed using the land accumulation index method and the potential ecological risk index method. Correlation analysis and positive definite matrix factorization （PMF） modeling were utilized to resolve the sources of heavy metals and fluoride contamination quantitatively. The risk levels of heavy metals and fluoride in soils were quantified through Monte Carlo simulations and health risk assessment models. The results showed that the average contents of Cd， Ni， Pb， As， Cr， and F were high and exceeded the background values of surface soil in Xinjiang， F and Cd were enriched to a high degree， and there may be localized point sources of pollution for Hg. In terms of spatial distribution， Cu， Cd， Ni， Zn， Pb， As， and Cr showed a tendency of spreading from the aggregation area to the periphery， Hg was characterized by a point-like distribution， and the area of relatively high values of F was distributed in the middle of the study area in the form of a slice. The level of contamination in the study area was generally low， with the main contaminating element being Cd. The combined potential ecological risk of the soil is low， with Cd and Hg being the most important ecological risk contributors. Ecological risk hotspots are distributed in blocks and points in the western and eastern parts of the study area， and coldspots are distributed in blocks in the northern part of the study area. There are four potential sources of soil heavy metals and fluoride： industrial sources （Cd）， mixed agro-industrial sources （As， Hg， and Ni）， atmospheric precipitation sources （Pb and Cr）， and combined natural-agricultural sources （F）， contributing 8.9%， 13.5%， 9.6%， and 68.0%， respectively. The carcinogenic and non-carcinogenic risks of Ni， Cr， and As in soil to the recipient population were at tolerable levels， and the carcinogenic and non-carcinogenic risks of the remaining five heavy metals and F to the recipient population were negligible compared to the higher health risks to children， which need to be emphasized.