Study On Morphological Characteristics Of Heavy Metals In Soil And Ecological Remediation Approach In Ningdong Energy And Chemical Industry Base

In order to investigate the distribution of heavy metals in the soil in the chimney subsidence area of the Ningdong Energy and Chemical Industry Park,the ecological risk situation,this paper measures the heavy metals in the surface soil of the Ningdong Chemical Industry Park and their different forms,in order to study the soil heavy metals in the chemical production area due to atmospheric deposition The enrichment and heavy metal morphology distribution provide data and theoretical support for guiding the site heavy metal in situ repair.In view of the soil types and nutrient content in the Ningdong region,while reducing the heavy metal content in the aeolian sandy soil,it should also take into account the improvement of soil texture and land utilization.In this paper,while monitoring and evaluating heavy metals,0.75 t·hm-2,1.5 t·hm-2,and 2.25 t·hm-2 were applied at 6%of chitosan-modified biochar and 20%of FeCl3-modified biochar.Six charcoal treatments were combined with ryegrass to carry out planting experiments.The physical and chemical and biological properties of the soil and the plant growth status were used to evaluate the soil improvement effect of the test site,providing new ideas and new methods for ecological restoration in Ningdong area.The results show:(1)The average contents of heavy metals Cu,Cr,Cd,Pb in the surface soil of the wasteland near the Ningdong Chemical Park were 41.13,1 81.5,0.12,33.91 mg·kg-1,respectively.The measurement results slightly exceeded the local heavy metal background values.However,it meets the national farmland soil environmental quality standards;the sources of heavy metals Cu,Pb,and Cd are consistent,and they are more likely to be disturbed by humans;the pollution sources of heavy metals Cr are more extensive,and may be subject to human disturbances and soil parent materials The influence of multiple factors;heavy metals Cu and Pb mainly exist in the form of residues,and Cr and Cd mainly exist in the form of carbonates.The evaluation results of the potential ecological risk index indicate that the risk of heavy metals in order from high to low is Cd>Cu>Pb>Cr;the evaluation results of RSP method indicate that the risk of heavy metals from high to low is Cd>Cr>Cu>Pb.Based on the above results,Cd is the main pollutant.(2)The contents of DR0.25WR0.25,MWD and organic matter all increased with the increase of the application amount of the two modified biochars,and reached their maximum when the application amount was 2.25 t.hm-2.The PAD and ELT values showed a trend of decreasing first and then increasing with the increase of the application amount of biochar.When the application amount was 1.5 t·hm-2,the soil aggregates were the most stable.The effect of chitosan-modified biochar on soil structural properties was better than that of FeCl3-modified biochar.Both modified biochars can significantly increase the content of organic matter,total nutrients and quick-acting nutrients in the soil.When the application amount of FeCl3-modified biochar is 2.25 t·hm-2,the effects of increasing organic matter,full-nutrient and quick acting nutrients are higher than others The processing is most significant.The application of modified biochar in aeolian sand soil can significantly reduce soil bulk density and increase soil porosity and water content.Taken together,the effects of modified biochars with different modification methods and application rates on the porosity,moisture content,and bulk density of aeolian sandy soils.The modification method with FeCl3 is the best,and the applied amount of biochar is 2.25 t·hm-2 is the best,followed by 1.5 t·hm-2.Compared with CK,the porosity and water content of Fe2.25 treatment increased by 24.08%and 16.17%,and the bulk density decreased by 6.21%.(3)The contents of bacteria,fungi and actinomyces in the soil and soil enzyme activity also increased to varying degrees under different application amounts and modification methods of biochar.In terms of different modification methods,FeCl3-modified biochar has better effects on increasing the H2O2 enzyme activity,invertase activity,and fungal colony count of aeolian soil than chitosan modified biochar;chitosan modified biochar has effects on soil urease.The effect of increasing the activity and the number of actinomycete colonies is better than that of FeCl3-modified biochar;the two modified biochars have the same effect on increasing the number of bacterial colonies.Under the same modification method,the three enzyme activities and the number of microbial colonies in the soil are based on the applied amount of modified biochar 2.25 t·hm-2>applied amount of modified biochar 1.5 t·hm-2>applied amount of modified biochar 0.75 t·hm-2.(4)Both modified biochars can significantly reduce the available Cu Cr,Cd,and Pb contents in the aeolian sand soil,and with the increase in the amount of modified biochar application,the contents of available heavy metals have a tendency to decrease.From the perspective of different applied amounts of biochar,the effect of 2.25 t·hm-2 was the best From the perspective of different modification methods,FeC13-modified biochar and chitosan modified biochar reduced the effective heavy metals.quite.(5)After the application of two modified biochars,the yield of ryegrass and the content of N,P,and K in ryegrass were significantly increased compared with the control CK without biochar.From the perspective of different applied amounts of biochar,the effect of 2.25 t·hm-2 was the best.From the perspective of different modification methods,the increase in nutrient content and yield of chitosan-modified biochar compared with FeCl3-modified biochar is slightly more significant.The contents of heavy metals Cu,Cr,Cd,and Pb in the upper and lower rye grasslands decreased with the increase of the amount of biochar.Under the treatment of biochar,the enrichment coefficients of heavy metals in all parts of ryegrass were reduced,and the enrichment capacity of heavy metals in the aerial parts showed a trend of Cd>Cr>Cu>Pb,and the underground parts showed Cd>Cu>Pb>Cr trend.Since the effective heavy metal ions in the soil were significantly reduced after the application of modified biochar,the toxicity of heavy metals to ryegrass was also reduced.