Experimental And Model Study On The Transport Of Heavy Metal Copper In Different Soil Types

In recent years,coal mining has produced a large amount of industrial solid waste,and the continuous release of heavy metals into the ecosystem has caused environmental pollution,which has aroused wide concern around the world.In this study,the vertical migration process of heavy metal copper（Cu）in different types of soil and the effects of p H,initial concentration of heavy metal,soil type and other factors on Cu migration behavior were expounded through the heavy metal soil column migration test.Furthermore,SPSS software was used to analyze the orthogonal test results,and the output expression model was established and improved.The model of the concentration of heavy metal copper ion(Cu²⁺)in leachate under different conditions was output.The influence and contribution of each factor in the model to the results were analyzed using the holistic and item-by-item analysis methods.Finally,the model was optimized by taking the basic physical and chemical property parameters of soil as values,which provided a practical model for the remediation of Cu pollution in acid gangue dumps.The main conclusions are as follows:（1）With the increase of time,the concentration of Cu²⁺in the leachate gradually increased.The higher the concentration of Cu²⁺and other cations in the initial leachate,the shorter the time required for penetration and adsorption saturation.In addition,the electrical conductivity（EC）and oxygenation reduction potential（ORP）in the leached solution of the three soils increased with the extension of leaching time,while the p H decreased.The type and concentration of ions were the main factors that positively affected the change of EC.ORP was negatively correlated with soil p H and initial leachate Cu²⁺concentration,and was affected by the content of easily decomposed organic matter in soil.（2）Four models were established through different fitting methods such as step by step and input,and interaction item construction and case diagnosis optimization.After comparison of model R²,the optimal model was determined as follows:C（Xn）=0.002X10X16-0.014X10X15-0.637X10X12+1.763X10（Ln X12）-0.003X10X11+0.143X10（Ln X6）+0.003X1X10+0.051X1（Ln X5）-19.531X6（Ln X4）+13.566X2X11-1.419X8（Ln X11）-0.009X1X7-0.0001X1X1+6.592x13-546.499.（3）The model verification results show that the predicted Cu²⁺concentration in leached solution has a good correlation with the experimental values,and the prediction accuracy and overall robustness of the model are strong.The most important correlation factor of soil parameters is soil dissolved organic carbon content（DOC）,which is positively correlated with Cu²⁺concentration in leached solution,and has a combined interpretation ability of 32.4%for experimental results.Soil clay,sand and soil cation exchange capacity（CEC）are positively correlated,while soil organic carbon and organic matter contents are negatively correlated.The most important correlation factor of leaching conditions was the initial Cu²⁺concentration of leachate,which was positively correlated with the results,and the combined explanatory power was 85.0%.The other factors are leaching time,SO₄^2-content of leachate,depth of soil column and Mg²⁺of leachate with positive correlation.In addition,the leachate p H has a special rule,which is positively correlated when the value is<3.32 and negatively correlated when the value is>3.32.The analysis results of correlation and contribution between model factors and experimental results show that the overall explanatory ability of leaching condition related factors in this experiment is better than that of soil parameter related factors.The Cu²⁺migration rule in the fixed area can be predicted by a simplified model which is only affected by leaching conditions.The simplified model isC（Xn）=C1+C2X1+C3X11+C4（Ln X11）+C5X13-0.0001X1X1+X10（0.002X16-0.014X15-0.637X12+1.763（Ln X12）-0.003X11+C6X10+0.003X1）.