| Cadmium is one of the potentially very toxic pollutants in the soil,and it is difficult to biodegrade after entering the soil environment.In the process of planting structural adjustment,there are fundamental changes in crop types after the dewatering of rice soil with heavy metal pollution.Therefore,the absorption and migration characteristics of different plants in the process need to be studied in depth.Selecting of heavy metal Cd contaminated paddy soil to be abandoned as research material,Cultivating different vegetables indoors,the distribution characteristics of heavy metal Cd between roots,stems and leaves of plants were discussed,and the basic data were provided for the restoration and reuse of abandoned paddy fields.The main findings of the study are as follows:(1)The soil column leaching test showed that the effect of leaching and descending Cd was not obvious.In leaching,soil Cd migration is small,and the release process of soil Cd has a rapid release period and a stable equilibrium period.During the process of leaching the soil with distilled water,the rapid release period of Cd in soil was short.After the soil leaching amount reached 4000 ml,the total Cd of soil decreased by less than 0.05 mg/kg,and then entered a stable equilibrium period.Therefore,it can be considered that reducing the soil Cd content by a single leaching method is difficult to achieve.(2)In paddy soils,the phenomenon of high Cd and available Cd in surface soils occurs when the paddy soils are planted in arid state,but the soil organic matter balance and acid-base balance will not be destroyed.The results of the analysis suggest that the higher soil Cd and available Cd in surface soil are related to the degree of surface root development.Combining the characteristics of soil Cd and available Cd was high in surface soils,deep plowing techniques can effectively balance the soil with high Cd content in surface soil.(3)In paddy soil,vegetables were grown under drought,and the Cd of vegetables in heavy pollution group was exceeded,while the Cd content of vegetables in medium pollution group was not exceeded.The results showed that the enrichment factors of cabbage were 8.63%,6.76%and 7.53%,respectively.The enrichment ability of three vegetables to Cd was as follows:Chinese cabbage>Water spinach>White radish.In addition,the Cd content of vegetables in the moderately polluted group did not exceed the standard,and even did not reach the 1/2 of the national standard limit,compared with the rice planting(rice crops have exceeded the standard),in the Cd Polluted Paddy field to carry out the drought planting vegetables should be safer.(4)The accumulation of vegetable organs to Cd is mainly affected by the rate of Cd migration and the rate of biomass growth in vegetables.The concentration of organs of three vegetables on Cd is:cabbage is Cd(root)>Cd(leaf)>Cd(STEM),white radish is Cd(leaf)>Cd(STEM)>Cd(root),The empty cabbage is Cd(root)>Cd(STEM)>Cd(leaf),and the Cd content of the White radish root in the edible part is the lowest.Therefore,it is more suitable to grow white radish in the dry soil contaminated with Cd than to grow cabbage and vegetables.In conclusion:paddy soil dry planting conditions,select the appropriate crop planting,can produce safe and healthy vegetables,can re-use of abandoned farmland to promote. |
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