The Remediation Of Cd Contamination In Farmland Soil By Several Plant Rotation Models

Selection of suitable tolerant crops is the key to the phytoremediation of heavy metal pollution in soil.In this study,8 crops with strong tolerance to heavy metals were selected for field experiments in wangcheng,liling,zhuzhou and xiangtan county,respectively.Herein,we planted rapeseed,red beet,endive,compositae in winter,and peanut,okra,sorghum,and endive in summer for crop rotation,in order to to establish eight crop rotation systems with two or three season?Red beet-peanut,helianthus annuus-peanut,rape-helianthus annuus,rape-sorghum,helianthus annuus-sedum alfredii-peanut,peanut-sedum alfredii-helianthus annuus,sedum alfredii-chicory and tobacco-peanut-chicory?,and simultaneously performed endive and endive mowing experiments to investigate the potential of these eight plant rotation models for the repair of heavy metals.The experiment was carried out in light Cd-contaminated soil in Qunli Village,Wangcheng District,Changsha.Two crop rotation systems,winter red leaf beet-summer peanuts and spring oil sunflower-summer peanuts were cultivated.The results show that except peanut fruit,the bioaccumulation coefficient of peanut,sunflower and red leaf beet to Cd is greater than 1.All these three crops have strong extraction capacity to Cd.It can take away Cd 40.80 g per hectare and 53.34 g per hectare,respectively,by the rotation of oil sunflower-peanut,red leaf beet-peanut for one season.The repair efficiency of Cd is 5.74%and 7.50%.Both of these planting patterns have a great potential to repair Cd pollution in soil.The total amount of soil Cd extracted in the rape-okra mode and rape-sorghum mode in one season were 33.82 g·ha^-1 and 36.18 g·ha^-1,respectively.The soil Cd repair efficiency was low,which was 4.22%and 4.52%.Commercial crops and ultra-enriched crops were rotated on Cd lightly polluted soil in huangshazhou village,liling city,to explore the remediation potential of heavy metals in four models:helianthus annuus-sedum alfredii-peanut,peanut-sedum alfredii-helianthus annuus,tobacco-peanut-chicory and sedum alfredii-chicory.The Cd enrichment coefficient of all crops in the peanut,oil sunflower and sedum alfredii model was greater than 1 except the peanut.The two rotation patterns of helianthus annuus-sedum alfredii-peanut and peanut-sedum alfredii-helianthus annuus could remove 114.12 g·ha^-1 and 105.6 g·ha^-1,respectively,and the restoration efficiency of Cd in soil was about 15.46%and 14.53%.A season of tobacco-peanut-chicory rotation can remove a total of 85.71 g·ha^-1 of cadmium,the repair efficiency of Cd is10.30%.Under the model of sedum alfredii-chicory,the cadmium in the overground part of sedum alfredii was 71.99g,and the cadmium in the overground part was 15.06 times as much as that in the underground part.Twelve cuts of chicory could remove a total of 77.56 g·ha^-1 of cadmium.The total amount of cadmium that can be taken away by the alfred stonecrop and chicory in the rotation season of liling city is 154.32 g·ha^-1,with the repair efficiency reaching 21.43%and great potential for repair.With the plantings of endive and endive for the herbage mowing experiment on the Cd slightly contaminated soil in daba village of zhuzhou county and shanyin village of xiangtan county,it is found that the efficiency of the single mowing is lower?2-5%?.In summary,considering the efficiency and economic value of restoration,the tobacco-peanut-chicory and peanut-sedum alfredii-oil sunflower model not only has high restoration efficiency,but also has good economic value,it can be used as an excellent alternative model to the traditional rapeseed-rice system.