| In so much treatment methods of heavy metals in contaminated soil,itu chemo-immobilization has the advantages of low input,quick effect and easy operation,and can better meet the need of controlling heavy metal pollution in soil.In this paper,the effects of calcium carbonate,humic acid and cow dung on the plant effectiveness of Ni in soil were studied by pakchoi planting experiments in greenhouse,and the changes of physicochemical properties of soil and the occurrence patterns of Ni elements were also explored.After adding calcium carbonate,humic acid and cow dung,the fresh weight of the single plant cabbage showed an upward trend.In the range of 6.4-7.0g·kg-1 of calcium carbonate and the humic acid of 7.0-8.3g·kg-1,the fresh weight of single plant of pakchoi reached the maximum value.Under the influence of cow dung(0-12g·kg-1),the fresh weight of pakchoi increased gradually,and the increase was between 31.3%and 326.3%.The content of Ni element in the plant of pakchoi was positively correlated with the content of Ni in the soil?P<0.01?.Under the same Ni pollution level,after adding calcium carbonate,humic acid and cow dung,the content of Ni in the plant of pakchoi decreased compared with that of the control group without the control agent,which indicated that three kinds of regulators could inhibit the plant effectiveness of heavy metal Ni.Within the scope of the 6-12g·kg-1of calcium carbonate and the humic acids of 5.9-6.9g·kg-1,the Ni element in the pakchoi plant was the minimum,and the content of Ni in the pakchoi plant decreased with the increase of the amount of cow dung,which decreased between 11.9%and 62.1%with the increase of the dosage of the regulator under different Ni pollution levels.Calcium carbonate,humic acid and cow dung as soil heavy metal fixing agent can reduce the content of exchangeable Ni in soil.In the state of calcium carbonate dosage is less than 6g·kg-1,the ratio of exchangeable Ni in soil decreases with the increase of the amount of calcium carbonate,exchangeable Ni converting to carbonate binding state and organic binding state.With the continuous increase of calcium carbonate(6-12g·kg-1),the content of the exchangeable Ni decreases.Regression analysis showed that with the calcium carbonate to 6.1-8.4g·kg-1,the ratio of exchangeable Ni had a minimum.The effect of humic acid was similar to that of calcium carbonate,the percentage of exchangeable Ni in soil reaches the lowest level when the amount of humic acid 6.2-7.5g·kg-11 is applied.Under the influence of cow dung(0-12g·kg-1),the content of exchangeable Ni decreases gradually and transforms into carbonate binding state and organic binding state.To sum up,the application of calcium carbonate,humic acid and cow dung can change the soil physical and chemical properties,so that the exchange of Ni content decreased to varying degrees,reducing the risk of migration to plants,and can promote the physiological metabolic process of pakchoi grown in soil.When using calcium carbonate and humic acid as regulators,the dosage should be controlled in the range of 6-8g·kg-1to achieve the best comprehensive effect. |
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