| Reclamation and utilization of industrial and mining wasteland plays an important role in improving the ecological environment and promoting the full utilization of land resources.However,toxic and harmful substances(heavy metals)are released into soil environment due to long-term mining,solid waste stacking and leaching loss of wastewater.So even after reclamation,there are still have many heavy metal pollution problems in reclamation soil.And with the advance of reclamation time,the sustainability of reclaimed land quality is poor.In this paper,the reclaimed soil of sulphur mine wasteland were taken as the research object.The characteristics of heavy metal content in reclaimed soil were explored through field sampling and testing,especially the distribution characteristics,pollution status,bioavailability and evolution of heavy metals content in the reclaimed soil of the abandoned land were mainly explored.The purpose is to provide basis for improving the quality of reclaimed soil and environmental restoration.The main results are as follows:(1)The average contents of Cr,Ni,Cd and As were 162.01 mg/kg,63.01 mg/kg,1.02 mg/kg and 12.57 mg/kg,respectively.The total amount of four heavy metals in different soil depths did not show the same migration characteristics.The content of Cr and As in the middle layer was the highest,the content of Cd in the surface layer was the highest,and the content of Ni in the bottom layer was the highest.The assessment results of heavy metal pollution in reclaimed soil show that Cd was the main environmental risk factor,and the ecological risk was high.Empirical Bayesian Kriging spatial interpolation showed that the spatial distribution patterns of heavy metals were different.(2)The average available contents of Cr,Ni,Cd and As were 0.103 mg/kg,0.674 mg/kg,0.307 mg/kg and 0.527 mg/kg,respectively.With the increase of soil profile depth,the available content of heavy metals showed a gradual decline.The results of bioavailability evaluation of heavy metals showed that the order of bioavailability coefficients of several elements in surface soil was Cd > As > Ni > Cr.The bioavailability of Cd was stronger.At the same time with the increase of soil profile depth,the bioavailability coefficient decreased gradually.(3)The available content of Cd was significant positively correlated with the total amount.The correlation of other elements was not significant.Soil pH and SOM also played an important role for the available heavy metals.With the decreased of pH,the available content of Ni,As and Cr in soil increased obviously.With the increased of SOM,the available content of heavy metals increased gradually.GWR effectively revealed the spatial relationship between various factors and available heavy metals,and reflected the effect of different factors on available heavy metals in reclaimed soil.(4)With the passage of reclamation time,As,Cd and Cr in soil showed increasing first and then decreasing trend,while Ni decreasing year by year in soil.Compared with the average content of heavy metals in 2015 and 2017,the average content of other elements was decreased,except Cd.The results of spatial evolution of heavy metal content in reclaimed soils showed that,the spatial distribution of As,Cd,Cr and Ni were similar,mainly reducing as a whole from 2015 to 2017.Influencing factors of heavy metal content evolution showed that the change of pH and SOM may had some indication for the evolution of heavy metals in surface soil.It is necessary to regulate and control the pH and organic matter content of reclaimed soil reasonably in order to improve soil quality.Figure [21] table [12] reference [128]... |
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