| As the indispensable natural mineral resources in human industrial activities, the lead and zinc mineral resources play an important role in our economic development. But we have neglected the environmental pollution caused by exploiting the lead and zinc mineral resources for a long time, which results in the pollution in a great amount of lead and zinc tailings.The article provides the theoretical basis for treating the heavy mental pollution in soil of lead and zinc mineral waste lands and the surrounding areas in Changhua of Hainan Province. Firstly, I collect 56 soil samples from the soil in the Changhua lead and zinc mineral waste lands and surrounding areas by the field study. Then I determine the heavy metal contents in soil of the waste lands and take advantage of the multivariate statistical analysis to analyze the heavy metal contents in research areas so as to reveal the distribution regularity of heavy metal pollution in research areas. Moreover, I evaluate the heavy metal pollution for the soil samples by the multidisciplinary comprehensive research method and combine the different valuation methods in China and abroad to carry out the more reasonable analyses and evaluation for soil quality in Changhua lead and zinc mineral waste lands and the surrounding areas. At last, the following conclusions are reached:(1) Cr in Changhua lead and zinc mineral waste lands and the surrounding areas coefficient of variation was 52.76%, the coefficient of variation was relatively small, which indicates that the distribution of Cr heavy metals is relatively uniform, the discrete degree is relatively low. The dispersion degree of Cu, Cd,Pb is very high, the distribution is very uneven, Zn and Ni. As discrete degree is the highest, the most uneven distribution. The content of heavy metal elements Cu, Zn, Cd, Pb average value is very high. Are the soil background value of Hainan province 35.57, 52.66, 363.40, 144.25 times, the content ratio of Cd>Pb>Zn>Cu; the average content of Ni was slightly higher than the background values of Hainan, the average content of Cr and As were significantly lower than the soil background values of Hainan Province, but its maximum values higher than the soil background value in Hainan.(2) The heavy metal elements Cu-Pb and Zn-Cd were highly correlated, the correlation coefficient is above 0.9, so there is a large possibility that they came from the same pollution. Cr and As are not highly correlated with other heavy metal elements, but they have some correlation with each other. Principal component analysis showed that high correlation is among three of the most load heavy metal elements, thus it can be seen that their pollution are came from the same elements. Cluster analysis shows that the heavy metal element Zn-Cd are of the same calss, so as the Pb-Cu and Ni-As-Cr.(3) Heavy metals content semivariogram model fitting shows that the semi-variogram model of As and Cr is bulbiform, while the semi-variogram model of Cu,Ni,Pb and Zn is Gaussian, only the Cd is for exponential model. In the study, heavy metals all show strong spatial correlation, the spatial variability is mostly caused by the soil parent material,climate and topography. The high content area of As is reclamation and tailing area, the maximum value of Cd and Zn are fastened on three area: the east of the tailing area,service area and turning place of the river, the maximum value of Pb and Cu are fastened on the two sides of the bridge, service area and around residential area, the east of the tailing area and extend to msot of the whole northwestward and midwest of the reclamation area. Cr mainly distributes the and southwest of the river end. Ni is fragmented distribution in the study area, at the mean time, the content of these two heavy metals are both lower than the national soil quality standard level.(4) According to the third level of the national soil quality standard, in the study area, nealy all of the Cd are sreious pollution level. Cu is a little lighter, only around the bridge and along the road to the south area. The northeast area is the clean area of Pb and Zn. The serious pollution area of Pb is the north of the tailing area, the perimeter of the reclamation area and the prolongation area to the northwest. The serious pollution area of Zn is fastened on the sevice area, the left side of the bridge,the east side of the tailing area, the north of the reclamation area and the turning place of the river and extend to the northwest. Nemerow pollution evaluation shows that Cu belong to light pollution levels, while Zn, Cd and Pb were severe pollution levels.Cumulative Index to pollution evaluation shows that Cd is most serious polluted,to a level of very serious pollution, shich followed by is Pb, basically all under the most serious pollution level. The pollution of the Cu and Zn for the study area is relatively light. The potential ecological harm level of the seven kinds of heavy metals were: Cd>Pb>Zn>Cu>As>Ni>Cr. Among them, the potential ecological risk index value of Cd is reached to 363.370, which reaches a critical level. the potential ecological risk index value of Pb is reached to 123.317, which reaches a critical level.Other elements of the potential risk index is below 40,belongs to minor contamination,and the comprehensive risk potential index value is 514.596, which is serious pollution. Cd contribution are most which reached a maximum of 70.62%. |
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