| In order to accurately understand the status of farmland quality and the impact of heavy metal pollution in ecologically fragile zone in western China, based on the data of second national land survey, multi-objective regional geochemical survey and soil fertility survey of agricultural l
and, using GIS technology and statistical methods, the comprehensive evaluation of farmland natural quality considering heavy metal pollution was conducted in Yuzhong County, Lanzhou City, Gansu Province. The results showed: ① The site conditions and soil physical properties of farmlands were relatively good in the study area, in which the class-4 farmlands whose quality was relatively good took the highest proportion. However, the fertility of farmlands was relatively poor, in which the class-2 and class-3 farmlands whose quality was relatively poor took 99.63% of the total area. ② The average contents of As, Cd, Cr, Cu, Hg, Pb and Zn were higher than the regional background values, in which those of Cd and As exceeded the assessment standard of soil environment quality. ③ Accordi
ng to the comprehensive evaluation of soil heavy metal pollution, Qingcheng Town, Heping Town and northeastern part of Mapo Town were highly polluted areas. ④ The farmland natural quality in the southern and central area was better than that in the northern mountainous area, and it showed an overall trend of gradual deterioration from south to north except for some abnormal sites. In conclusion, soil pollution caused by heavy metals has become a serious problem in the ecologically fragile zone of western China, although the natural quality of farmlands is mainly affected by rainfall, slope and other natural conditions. |