BACKGROUNDThe Jiulong area in western Sichuan is an important rare metal production area in China, which has a large resource potential. As an ecological protection barrier on the upper reaches of the Yangtze River, the ecological environment of this area is fragile. Facing the huge opportunities of mining development and under the current situation of 'environmental protection first', it is urgent to investigate the environmental background of this area to support the development of national energy strategy.

OBJECTIVESTo evaluate the ecological risk of heavy metals in soils from the Jiulong Li-Be mining area.

METHODSA total of 352 soil samples were collected. The concentration of 7 heavy metals (Cd, As, Pb, Cr, Cu, Ni, Zn) in soil was analyzed by NexION 300x inductively coupled plasma-mass spectrometer (ICP-MS). The comprehensive assessment methods including geoaccumulation index, pollution load index, potential ecological risk index, and health risk model, combined with GIS spatial analysis were used to study the spatial distribution characteristics and ecological risk of heavy metals in the soil.

RESULTSThe average concentration of all 7 heavy metals in the soil in Jiulong did not exceed the Chinese national standard. There was no soil heavy metals pollution in the studied area. Compared with the soil background value of Sichuan Province, the average concentrations of As and Pb were lower than the background; the concentrations of Cd, Cr, Cu, Ni, and Zn were higher than the background, which were 2.44, 1.04, 1.15, 1.28, and 1.17 times the background values, respectively. The spatial distribution characteristics of these elements except As were affected by biotite granite in the study area. The high concentration center of Pb and the low concentration center of Cr, Cu, Ni and Zn had an obvious correspondence with the spatial position of the rock mass. Except for the weak accumulation indicated by Cd I_geo, there was no accumulation of other heavy metals. Similarly, there was no potential ecological risk in the study area, except for the slight potential ecological risk of Cd. Spatially, the distribution of Cd single element potential ecological risk index was related to the rock mass, and the area without potential ecological risk corresponded to the location of the biotite granite rock mass. Heavy metals in the soil can enter the human body through direct contact with hands, mouth, and skin, and through inhalation. The hand-to-mouth approach is the most important way to generate health risks among all 3 approaches. Except hand-to-mouth approach of Cr, which has an acceptable and normal natural carcinogenic risk, there is no carcinogenic risk for other metals.

CONCLUSIONSAt present, there is no pollution of heavy metals in the soil in the studied area. The potential risk of heavy metals is low, and there are no non-carcinogenic and carcinogenic risks. However, due to the cumulative effect of heavy metals in the soil, close attention must be paid to changes in the concentration of heavy metals in the soil in the future mining development process, to prevent the risk caused by heavy metals pollution.