Screening Of Highly Enriched Plants And Comparison Of The Phytoremediation Potential By Different Crop Rotation Models In Mild And Moderate Cadmium Polluted Farmland

Highly enriched plants and their rotation can extract heavy metals from soil and realize the phytoremediation in contaminated soil.In this study,the cadmium extraction ability of 20highly enriched plants?Sedum alfredii Hance,Calendula off icinalis L,tobacco,Celosia cristata L,Sedum spectabile and Oil Sunflower?in moderate and mild cadmium-contaminated farmland in Zhuzhou were studied.Afterwards,suitable crops and rapeseed were selected for rotation experiment.Double-oil rotation mode,Soybean-Rape and black bean-rape rotation mode,economic crop and oil crop rotation mode,tobacco-rape,okra-rape,sorghum-rape rotation mode,were carry out to explore the potential capacity phytoremediation of various plant rotation modes to soil cadmium.The results shows that:?1?The heavy metal enrichment ability of twenty kinds of enrichment plants was discussed.The results showed that Sedum alfredii Hance,Calendula off icinalis L,tobacco,Celosia cristata L,Sedum spectabile and Oil Sunflower all showed excellent cadmium enrichment ability in moderate and mild cadmium-contaminated soils.Among them,Sedum alfredii Hance had the strongest cadmium enrichment ability,with BCF value of 149.5,followed by Calendula off icinalis L leaves,with BCF value of 33.37.Sedum alfredii Hance,Calendula off icinalis L,tobacco,Celosia cristata L,Sedum spectabile and Oil Sunflower all showed strong ability of cadmium extractable.The total Cd extract quantity were 287.38,201.04,146.03,128.44,117.63 and 91.73 g·ha^-1,respectively,which were suitable for phytoremediation of moderate and mild cadmium-contaminated soils.The other plants also showed a considerable ability to extract heavy metal cadmium.?2?Black soybean-rapeseed and soybean-rapeseed crop rotation showed higher extraction capacity of cadmium.In the black Soybean-Rape rotation model,black soybean showed a strong cadmium accumulation ability.The Cd contents in roots,stems,leaves and shells were 2.14,2.63,4.10 and 1.34 mg·kg^-1,respectively,with enrichment coefficients above 1.The contents of leaves and stems in different parts of rape were 7.13 and 4.73mg·kg^-1 respectively.Transport coefficient of black soybean was higher than that of soybean.Heavy metals extracted from oil crops were mainly concentrated in stems and leaves.A round of black Soybean-Rape rotation can extract 73.52 g·ha^-1 and 51.68 g·ha^-1 of cadmium from the soil,,respectively.?3?The phytoremediation potential of tobacco-rape,okra-rape and sorghum-rape rotation models for moderately and mildly cadmium-contaminated farmland was analyzed through crop rotation between economic crops and oil crops.The results showed that the three cropping patterns could extract cadmium from soil effectively,and the tobacco-rape cropping pattern had the strongest ability for cadmium extraction.After a round of tobacco-rape cropping,the extraction of Cd was about 176.75 g·ha^-1,and the Cd in soil decreased from0.993 mg·kg^-1 to 0.925 mg·kg^-1,and the restoration efficiency was 7.9%.However,there was little difference between okra-rape rotation and sorghum-rape rotation in the recovery efficiency of heavy metal cadmium,which was about 2.1%.