The Technical Optimization Of The Immobilization Of Heavy Metals In Farmland Soil By Several Materials

With the development and utilization of mineral resources,the rapid development of industrial production,the excessive use of pesticides and chemical fertilizers in agricultural production process,the heavy metal pollutants entered the soil,which in turn make the soil continuously polluted,especially the farmland soil.The remediation of contaminated soils by heavy metals has attracted world-wide focus.The purpose of this paper is to study the remediation effect on heavy metal polluted soils of different materials and optimize relevant technical parameter,based on in situ chemical remediation method,which can provide some theory reference for the remediation of four kinds of soil polluted by heavy metals in farmland.In this paper,the effects of seven kinds of materials on the remediation of Cu,Zn,Hg and Cd contaminated soils were studied and the economical and effective inactivation materials were selected.After that,the addition gradients and sampling interval time of the screened materials were studied.Finally,availability of the heavy metals towards Indian mustard was evaluated through pot experiments.The main conclusions are as follows:(1)Cu,Zn,Hg and Cd respective contaminated soils were treated with seven kinds of materials,namely iron ore powder,coal gangue,phosphate rock powder,weathered coal,diatomite,wood vinegar and chitosan.The results showed that after 5 weeks,the available content of heavy metals in the soil gradually stabilized of most additional materials;After 7 weeks,the contents of available Cu in the soils were significantly decreased by weathered coal and phosphate rock,with 73% and 49% reduction,respectively;The iron ore powder and the weathered coal had effective inactivation effect on Zn in soil,which could reduce the available Zn content by 82.2% and 72.6%;Both diatomite and iron ore could effectively reduce the available Hg in soil and the reduction rate was 51.7% and 48.5%;The diatomite had efficient remediation effect on Cd in soil,the available Cd in soil was reduced by 51.3%.On the contrary,chitosan could increase the content of Cu,Zn and Hg in the soil to a certain extent.(2)Zn,Hg and Cd in the soil were determined by the addition amount of four kinds of materials: weathered coal,iron ore powder,diatomite and chitosan,respectively.The effects of different materials addition levels on the availability of Cu were studied.The results indicated that the content of available heavy metals in the soil gradually stabilized after 5 weeks of addition.7 weeks later,the content of available heavy metals in the soil decreased caused by the increase of addition amount,when the dosage reached a certain level,the amount of available heavy metals decreased steadily,the dosage of weathered coal was 450 g/kg,the content of available Cu decreased by 81.3%;When the addition of iron ore powder was 150 g/kg,the content of available Cu in soil decreased to a certain level,the content of available Hg reduced by 62.6% when the diatomite content was 350 g/kg,and decreased by 58.9% when the dosage of chitosan was 60 g/kg.(3)The results of pot experiment showed that the biomass of Brassica chinensis L.was decreased by the treatments of high content of weathered coal and iron ore powder and,and all treatments of treatments chitosan reduced it,while all different adding amounts of the diatomite treatments could increase that of it;Compared to the control,when the content of weathered coal was greater than 150 g/kg,which had little effect on the content of Cu in the aboveground part of Brassica chinensis L.by adding weathered coal.The content of Zn in the aboveground part of the Brassica chinensis L.was the lowest and was 21.5% lower than that of the control,when the added amount of iron ore powder and was 150 g/kg;When the amount of diatomite was 250 g/kg,the absorption of Hg in the upper part of Brassica chinensis L.came to be the lowest content,which decreased by 48.3% compared to the control;The absorption of Cd came to be the lowest value in the Brassica chinensis L.upper part when the content of chitosan was 60 g/kg,and decreased by 77.1% compared to the control.