| The remediation of heavy metal contaminated soil has become an urgent task for the safe production of agricultural products in China.Among many remediation technologies,phytoremediation is the most economical and safe method,but its remediation efficiency is low and the remediation time is long,which has become the most fatal shortcoming of this technology.Therefore,in this paper,the study on the phytoremediation of soil contaminated by cadmium and lead using Sedum alfredii was carried out with the method of indoor simulation and potted cultivation,which on the one hand seeks a way for the high value use of compost,on the other hand seeks a cheap and easily obtained remediation agent for heavy metals contaminated soil.The main results are as follows:1.Application of fulvic acid(FA)and humic acid(HA)could activate Cd and Pb in a short time.Although compost contained a large amount of FA and HA,its direct application had no activation effect on Cd and Pb,and even had a passivation effect.The resultss of FA and HA on available Cd in soil showed that both FA and HA had obvious effects on available Cd in soil,and FA was more active than HA.On the 5th day,the content of available Cd in soil with FA was higher than that in the control group by 15.4%-19.9%.The 0.1%FA treatment had the best effect on Cd activation.The activated Cd decreased and stabilized within 30 days,but was still higher than that in the control group by 7.0%-7.9%.The activation effect of HA on Cd was consistent with that of FA.On the 5th day,the content of available Cd in soil was higher than that in the control group by 7.6%-10.6%.On the 30th day,0.3%and 0.1%treatments still increased by 3.0%and 4.4%respectively.The results of FA and HA on available Pb in soil showed that both FA and HA had little effect on available Pb in soil.The activation of FA and HA to Pb only occurred in the first few days after addition.The available Pb of all FA and HA treatments was higher than that in the control in 5 days.The available Pb of 0.1%FA and 0.1%HA increased by 17.1%and 8.3%respectively.The results of compost on available Cd and Pb showed that after 30 days of applying different kinds of compost,available Cd decreased by 4.9%-12.3%and available Pb decreased by 16.3%-24.6%2.FA and HA extracted from different kinds of compost had obvious activation effect on soil Cd but not Pb.The results of compost FA and HA on available Cd showed that all kinds of compost FA had the best effect on available Cd on the 5th day.At this time,the available Cd of duck manure FA(DF)was the highest,which was higher than that of the control by 17.1%.After 5 days,the available Cd of each treatment group fluctuated,and reached a stable level on the 30th day.At this time,the available Cd of pig manure FA(PF)was the highest,which was higher than that of the control by 4.8%The effect of HA addition on Cd activation was slower than that of FA.The available Cd reached the peak on the 10th day,then fluctuated and decreased,and reached a stable level after 30 days.Among them,the available Cd of pig manure HA(PH)was the highest,which was higher than that of the control by 9.4%at the peak and higher than that of the control by 5.3%at the stable stageThe characteristics analysis of compost FA and HA showed that FA and HA might complexate with Cd through acidic functional groups such as phenolic hydroxyl group,amide group and carboxyl group,so as to improve the solubility of Cd in soil and then improve the availability of Cd.On the other hand,FA and HA could reduce soil pH and make hydrogen ions compete with cadmium ions for binding sites,thus releasing cadmium ions and improving the bioavailability of CdMorphological analysis results showed that FA and HA could transform reducible,oxidizable and residual Cd into weak acid extractable Cd,making the ratio of reducible Cd increase by 3.0%-4.8%,transform residual Pb into reducible Pb,making the ratio of reducible Pb increase by 2.0%-3.7%3.The application of compost FA and HA could significantly promote the growth of Sedum alfredii and the absorption and accumulation of Cd and Pb,significantly improve the remediation efficiency of Sedum alfredii to Cd contaminated soil,and effectively shorten the remediation time of Sedum alfredii.The results of different compost FA on Sedum alfredii.showed that PF had the best effect on promoting the growth of Sedum alfredii and absorbing Cd and Pb.The biomass of Sedum alfredii increased by 80.2%,the accumulation of Cd and Pb increased by 277.5%and 243.8%,respectively.The extraction rates of Cd and Pb were 36.5%and 3.9(?),respectively;The results of different compost HA on Sedum alfredii showed that PH had the best effect on promoting the growth and absorbing Cd of Sedum alfredii.The biomass of Sedum alfredii increased by 37.7%,the accumulation of Cd and Pb increased by 217.0%and 88.7%,and the extraction rates of Cd and Pb were 30.6%and 2.7(?),respectivelyThe change of Cd content in soil before and after remediation showed that compost FA and HA could improve the Cd recovery rate of Sedum alfredii.In the FA treatment group,the Cd remediation rate of PF was the highest,up to 43.5%,which was 2.8 times that of the control group.In the HA treatment group,the Cd remediation rate of PH was the highest,up to 34.6%,which was 2.2 times that of the control groupUnder the condition of 5.84 mg/kg of Cd in the tested soil,taking the risk control standard of soil pollution as the remediation objective(0.6 mg/kg),only planting Sedum alfredii needed 14 crops(28 months planting period)to reach the standard of Cd contaminated soil remediation,and the application of 0.1%PF could shorten the remediation time to 4 crops(8 months planting period),greatly reducing the remediation time. |
PDF Full Text Request