Classified Management And Control Practice Of Cadmium Contaminated Farmland Soil

In order to cope with soil pollution major challenge and improve soil quality and ensure soil safety in agricultural land,on 28th of May 2016,the State Council of the People's Republic of China issued the Action Plan for the Prevention and Control of Soil Pollution.The plan emphasized classified management of agricultural land to ensure environmental safety in agricultural production and required the safe utilization rate of contaminated farmland to reach 90%by 2020.In this context,the study carried out classified management and control practices in the study area of Zhejiang province.The main results are summarized as follows:(1)This study summarized the research results of plot experiments in the early stage,approach the pattern of the safe use in the farmland soil with lightly and moderately cadmium-pollution,and carried out the extension practice in Wenlin.Through the descriptive statistical analysis of the soil physical and chemical properties and heavy metal concentrations of 365 surface soil samples(0-20 cm)samples in study area,the results showed that the soil was generally acidic with an average pH of 5.72 in study area.The Cd contamination was the most prominent,with the exceeding rate of 53.15%.There was mainly lightly and moderately Cd-contaminated soil by degree of contamination.28 rice grain samples were collected in the three regions(northwest,central and east)with prominent Cd contamination in the study area,half of the Cd of rice grain samples exceeded Cd legal threshold(0.2 mg/kg)of the National Food Safety Standard Maximum Levels of Contaminants in Foods(GB 2762-2017).On the basis of Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land(trial)(GB 15618-2018),agricultural land was classified into three categories:priority land for protection(2535 hm2),land of safe use(364 hm2)and land under strict control(52 hm2)combined with single factor evaluation method and nemero index method,geostatistics spatial interpolation analysis,and zonal statistics analysis.The practice of safe utilization pattern was employed in the lightly and moderately Cd-contaminated soil(225 hm2)in 2018.The safety technology pattern was applied to the early rice,late rice and single-cropping rice,respectively.The rate of qualified of rice was 90.4%(198 rice grain samples).The results showed that the pattern of soil safe use in farmland with lightly and moderately Cd-contaminated could ensure the safety of rice production within one year,and its stability of safe utilization still need to be further explored.(2)Through investigation of vegetables and the corresponding soil in the upland soil of study area,found that the Cd concentration in the taro and soybean which grown on heavy Cd-contaminated soil exceeded Cd legal threshold of GB 2762-2017 badly,for this type of soil should be strictly control its uses.In the lightly and moderately Cd-contaminated soil,eggplant,melon and golden melon are slightly out of Cd legal threshold of GB 2762-2017.The alternative planting method for this kind of soil can be safely used.The Cd concentrations in the three sugarcane varieties(wenling qingpi,wenling fruit sugarcane and guangdong huangpi)and rape(zheyou 50)planted by substitution did not exceed Cd legal threshold of GB 2762-2017,which was suitable for growing in local upland soil with lightly and moderately Cd-contaminated.Based on the practice of safe utilization of paddy field and upland,the safe utilization planting model of rice-rape rotation was put forward.In the local lightly and moderately Cd-contaminated soil,it has been proved that the safe utilization planting model of rice-rape rotation can not only ensure the rice and rape food safety,but also can uptake 16.65-31.95 g/hm2 Cd from the soil.Rice-rape rotation pattern proposed a feasible strategy for the phytoextraction of Cd contaminated soil as the agricultural benefit could be guaranteed at sacrifice of remediation time.(3)The results showed that Soliva anthemifolia(Juss.)R.Br.had a strong Cd accumulation capacity by the field survey,and the shoot Cd bioaccumulation factor reached 32.1.The tolerance and accumulation characteristics of Soliva anthemifolia(Juss.)R.Br.were testified by hydroponic experiment.It was observed that the concentration range of Cd in the hydroponic culture solution which Soliva anthemifolia(Juss.)R.Br.was able to grow was 0-100 ?mol/L.Among all the Cd treatments,the bioaccumulation factor of Cd in Soliva anthemifolia(Juss.)R.Br.was greater than 1 and the maximum was 99.43.When the Cd treatment was 300 gmol/L,the Cd concentration of shoots reached the maximum of 3,311.0 mg/kg.In the hydroponic experiment,Soliva anthemifolia(Juss.)R.Br.showed strong Cd accumulation capacity,which is a potential Cd accumulator.In the future,the remediation effect and tolerance characteristics of Soliva anthemifolia(Juss.)R.Br.in local contaminated-soil need to be further explored.By the adjustment of the agricultural cropping structure in the arable land under strict control,the energy plants and hyperaccumulator were planted.Among the energy plants,these plants(sweet sorghum varieties:Dalishi,Tianjingyihao,Tianjingerhao and ordinary sorghum,pennisetum hydridum and festuca arundinacea)have a stronger Cd accumulation capacity.The bioaccumulation factor of pennisetum sinese is relatively small,but it has the maximum biomass,it's also has a strong Cd phytoextraction efficiency.The Cd phytoextraction efficiency of ryegrass was the weakest.Because of the economic benefit,energy plant was a good choice for the adjustment of cropping structure of heavy Cd-contaminated farmland.Among the hyperaccumulator,Sedum alfredii Hance and Sedum plumbizincicola had significantly higher Cd accumulation capacity than others,and the Cd bioaccumulation factor in stems and leaves of both plants were 1,003,423.52 and 90.58 and 170.18,respectively.For the phytoremediation of heavy Cd polluted farmland,Sedum alfredii Hance and Sedum plumbizincicola should be the good choice.