Content status and assessment of heavy metals in soils from patato growing areas in Liuzhi， Panxian and Shuicheng counties， Guizhou province

The surface soils from patato growing areas in Luizhi， Panxian and Shuichen counties were sampled and the contents of seven heavy metals including As， Cd， Ni， Cr， Pb， Cu and Zn were measured. The pollution characteristics and ecological risk of heavy metals were respectively evaluated by means of single factor index， Nemerow index， geo-accumulation index， Hakanson’s ecological risk index and pollution load index. Meanwhile， the differences of different results were compared and explored. The results showed that the contents of As， Cd， Cu， Ni， Pb， Zn and Cr of surface soils were respectively 49.46， 1.17， 71.19， 29.96， 27.34， 100.34 and 13.31 mg/kg. The contents of As， Cu， Ni， Pb， Zn and Cr were in line with national soil environment quality standard（level 2） ， but the content of Cd was over standard， moreover， the over standard multiple was 1.95 and the exceeding standard rate of sampling points was 48.49%. Besides， the results of heavy metal pollution evaluated by Nemerow index and Hakanson’s ecological risk index reached agreement to three sampling areas， and the heavy metal pollution degree was Panxia n>Shuicheng>Liuzhi. In addition，The evaluation on pollution risk of each heavy metal acquired general consistence by geo-accumulation index and Hakanson’s ecologiacal risk index. As， Cr， Ni， Pb， Zn and Cu were not polluted，but Cd was slightly enriched. Finally，the pollution index in patato 7 growing areas evaluated by the mean of pollution load index was 0.73， the environmental quality classification was non-pollution. The results of different evaluation methods were different. It suggests that different evaluation methods and reference standards are chosen cautiously according to the research focus when soil environmental quality is evaluated.