Heavy Metal Migration Analysis And Ecological Risk Assessment Of Rainwater Pipe (ditch) Sediments In Open Pit Mining Area

In order to explore the migration and potential ecological risk of heavy metals in the rainwater pipe(ditch)sediments of open-pit mines,this paper selects the rainwater pipe ditch in an open-pit mine in Jiangxi as the research object,and analyzes the total and morphological changes and their migration and transformation patterns before and after rainfall of the heavy metals in the rainwater drainage ditch in different areas of the mining area in the wet season,dry season and flat water period,and different evaluation methods were used for ecological risk assessment.The main analysis results are as follows:(1)Possible sources of heavy metals in the rainwater gully sediments of the study area:Cd and Pb may originate from mining and mineral mining activities;Cu may be derived from mining activities;Zn and Cr may be derived from residential life and industrial gold-plated appliances use and mining activities.(2)The relationship between the total amount of heavy metals and the active state: the five heavy metals Cu,Zn,Pb,Cd and Cr in the sediments of the rainwater pipe(ditch)in the mining area,the total amount and the active state(ie non-residual state)content are significantly positive correlation.Linear regression analysis showed that the total linear effect of Cu,Zn,Pb and Cd was better than that of the active state,indicating that the content of active state of these four heavy metals changed with the total amount;the linear simulation effect of total amount and active state of Cr was not Good,indicating that the active state content does not change significantly with the total amount.(3)Before and after rainfall in the wet season,the change of total amount of heavy metals in the rainwater pipe ditch of open-pit mining area: the total performance of Cu,Cd and Cr after the rain showed a decreasing trend,while the total amount of Zn and Pb showed an increasing trend after the rain;The morphological change of heavy metals: Cu,Cd,Cr decreased the average percentage of residual state after rain,and the average percentage of residual Zn and Pb residual state increased.(4)Effects of different rainfall intensities on the total amount of heavy metals in the rainwater gully sediments during the wet season,dry season and flat water period: the total amount of Cu,Zn and Cr changes with the rainfall intensity during the wet season-dry season-flat water period first increase and then decrease,the total content of Pb increases from the wet water period to the dry season to the flat water period,and the total content of Cd decreases after the high water period-dry season-flat water period;the effect on heavy metal form: The percentage of the total content of the Zn,Pb,Cd and Cr four heavy metal residues is increasing,indicating that the non-residual state is undergoing migration to the residual state,the potential migration capacity is reduced,and the potential ecological risk is also reduced.(5)Ecological risk assessment results: According to the risk assessment criteria,the five heavy metals have different degrees of pollution.The pollution risks in the wet season,dry season and flat water period are Cd>Cr>Zn>Pb>Cu;secondary phase and primary The results of phase distribution ratio method showed that the five heavy metal pollutions were affected by human sources.The potential ecological risks of Cu,Zn,Pb and Cd were higher and the Cr was relatively lower before and after rain in three different periods.The pollution load index method was used.The evaluation results show that the composite pollution degree of each sample is higher before and after rain,and the heavy metal complex pollution in the whole research area is also serious.The results of potential ecological risk index evaluation showed that the composite ecological risk of each sample in the study area was strong in different periods,and composite pollution generally showed the highest contribution rate of Cu and Cd.