Study On The Migration Characteristics Of Cu And PAHs In Soil And Groundwater And Soil Remediation In Mining Activity Affected Area

Coal is the most important disposable energy in China at this stage,and its status as the main energy will not change in a short period of time.Although the number of coal mines is decreasing year by year,the area of China affected by mining activities is still large.Huabei Linhuan Industrial Park located in the main coal mining base in East China,which is subject to the combined effects of industrial activities,mine mining and agricultural production,and has a complex ecological environment.Previous monitoring identified potential risks of copper（Cu）and polycyclic aromatic hydrocarbons（PAHs）in soils in the study area.Previous monitoring identified potential risks of Cu and PAHs in soils in the study area.In this study,the soil and groundwater of the Huai Bei Linhuan Industrial Park were selected as the main research objects,and the changes in the distribution of Cu and PAHs contents were monitored.The main pollution sources and transported characteristics were studied using Cu stable isotopes(δ⁶⁵Cu)and the characteristic ratio method,and the contribution of anthropogenic sources in the polluted area was quantified using the isotope mixing model and PMF model.In addition,Cu and PAHs stress tests were conducted on Brassica（Brassica chinensis L.）to analyze the response of Brassica to the complex pollutants.Based on this,compost,biomass charcoal and modified biomass charcoal were prepared from the same raw materials to investigate the effect of passivated materials on the composite contaminated soil and Brassica.The main research results are as follows:（1）The content and distribution of heavy metals and PAHs in groundwater and soil in the study area were clarified.The content of Cu in groundwater was significantly different between the contaminated and uncontaminated areas.PAHs monomers did not exceed the standard but spatial differences were significant.The highest concentrations of Cu and Zn in soils were distributed in the contaminated areas.Cd,Cr,and Mn had similar spatial distribution patterns,and the results of correlation analysis were verified with each other and the spatial distribution patterns of heavy metals.Soil profile characteristics showed similar migration patterns of heavy metals in the profiles,except for Cu.PAHs are 100%lightly contaminated in uncontaminated area samples,and heavy pollution reached 37%in the samples of contaminated area,PAHs were more contaminated in the study area.（2）The transported characteristics,sources and contributions of Cu in soil and groundwater were analyzed.Analysis ofδ⁶⁵Cu in soil,plants,water and source samples showed that Cu isotope fractionation was influenced by a combination of mining activities,bedrock and biogeochemical processes.The migration of Cu in the uncontaminated zone profile was controlled by oxidative dissolution of gangue and fly ash-generated dust on the soil surface,with the surface enriched in heavier Cu isotopes,while the uncontaminated zone was influenced by the biogenesis.The bottom of the profile was subjected to the adsorption of Fe and Mn oxides.Compared with the uncontaminated area,theδ⁶⁵Cu in groundwater in the contaminated area were higher and the migration of Cu was related to the water-soil particle interactions.Quantitative analysis of Cu in soils from contaminated areas using a hybrid model showed that mining inputs accounted for the major source of Cu in soils from contaminated areas（contribution of 72%）.（3）The migrated characteristics and sources of PAHs in soil and groundwater were investigated,and the content of PAHs and TOC were positively correlated and negatively correlated with water content.The mobility of PAHs showed a pattern of LMW>MMW>HMW,the proportion of 2+3rings in groundwater reached more than 80%.Sources of PAHs in soil and groundwater were quantified using PMF model simulations and SPSS 20.0 stepwise method to establish linear regression equation contributions.The results showed that PAHs of groundwater in areas affected by mining activities mainly originated from coal and biomass combustion（46.4%）,gasoline combustion and oil spills（20.1%）,coking sources（18.2%）and traffic emissions（15.3%）.PAHs in soil mainly originated from coking and coal combustion（31.0%）>biomass combustion and gangue solid waste accumulation（25.8%）>traffic emissions（24.5%）>petroleum spills and industrial combustion（18.7%）.（4）The effects of Cu,PAHs and combined pollution on the growth of Brassica were analyzed.When the concentration of Cu was 0-200 mg·kg^-1 under the stress of contaminant alone,it was the threshold of toxic stimulation for the growth of Brassica,and the threshold of chlorophyll was smaller(≤30.47mg·kg^-1).Under combined pollution stress,seed germination and chlorophyll value showed antagonism at low concentration and synergism at high concentration.Under combined pollution stress,ΔM values of plant biomass increased with concentration,and the antagonism was obvious.The activities of CAT,POD and SOD increased first and then decreased（except POD under Cu stress）under single and combined pollutant stress.Under PAHs stress,the contents of Nap,Phe and Pyr in aboveground and underground parts of Brassica were significantly positively correlated with the exogenous concentration of PAHs.Compared with Cu stress and combined pollution stress,PAHs promoted the accumulation of Cu in Brassica in a certain range.The enrichment coefficient of root system was higher than that of stem and leaf in all stresses.The effects of passivation materials on compound contaminated soil and Brassica were clarified.The characterization and isothermal adsorption of three passivating materials,compost（C）,biochar（B）and iron-modified biochar（Fe-B）,prepared from the same raw material were studied.The adsorption results showed that the adsorption effect of Phe was C<Fe-B<B;the adsorption effect of Cu was C<B<Fe-B.The results of Cu occurrence morphology and PAHs bioavailability showed that B and Fe-B promoted the conversion of Cu from weak acid extraction state and oxidizable state to residue state,and reduced the availability of heavy metals.The addition of C,however,activated Cu（Ⅱ）.B had the most significant adsorption effect on Phe,and C reduced the effectiveness of PAHs through microbial degradation.The addition of passivating agent promoted the growth of Brassica and reduced the enrichment of pollutants in plants.B was the passivating agent with the best effect.The results of this study provide a new method for tracing the source of heavy metal Cu in the area affected by mining activities,and a new discussion on the effect of different preparation of green raw materials on the remediation of Cu-PAHs contaminated soil.The Cu isotope database and the fingerprint of PAHs pollution sources were improved.It provides scientific basis for the impact and restoration of the ecological environment in the process of mineral resources exploitation,and provides theoretical support for ensuring food safety.