| Heavy metal pollution in farmland soil has become one of the main environmental problems that need to be solved urgently in China.Heavy metal pollution in farmland soil is mainly caused by the unreasonable use of pesticides,fertilizers and sewage irrigation.Heavy metals enter the soil through different channels,which poses a serious threat to the quality of the soil environment and the quality of crops,which in turn affects human health through the food chain.The pollution sources of farmland soil in Panzhihua area are mainly unreasonable agricultural irrigation,application of phosphate fertilizer,solid waste,mining,exhaust gas emission,etc.The heavy metal pollution of farmland soil in Yanbian County is the unreasonable application of pesticides and fertilizers and unreasonable irrigation Caused by the random stacking of solid wastes such as ore dressing slag and blast furnace slag.Biochar is a substance that is pyrolyzed under the anaerobic or anoxic conditions to form a porous and porous material with high carbon content.Biochar can increase the carbon storage in the soil,and can change the original physical and chemical properties of the soil.At present,the research on the impact of biochar on the changes of various forms of heavy metals in soil and the amount of crop transfer and accumulation is one of the important topics.In this study,biochar decomposed by anaerobic decomposition of corn,rice and other stalk biomass was selected as the remediation material,and a heavy metal contaminated soil in a farmland of Panzhihua Yanbian County was selected as the test site for field field research and a random block design was adopted to hybrid rice varieties.“Y Liangyou 973”is a test crop to study the changes of soil physical and chemical properties at the tillering stage and mature stage of rice after the application of biochar,the relationship between biochar and rice transfer and enrichment of heavy metals Cd,Cr,Cu,Ni,Zn,and The contents of different forms of Cd,Cr,Cu,Ni,Zn in soil changed.The results achieved are as follows:1.The effect of biochar on the physicochemical properties of the soil at the tillering stage and the mature stage of rice shows that after applying biochar,compared with the control group,the soil p H value at the tillering stage and the mature stage of the rice is under 1.0 kg·m-2 Generally speaking,with the application of biochar,there was an upward trend.Among them,the p H value of the soil during rice maturity was the highest under the treatment of 1.5 kg·m-2,which was an increase of 0.71 units compared with the control group;The contents of organic matter,available phosphorus and available potassium in the soil under the treatment of 0.5kg·m-2 and1.5 kg·m-2were significantly higher than those of the control group,and the tillering stage of rice under the treatment of 0.5 kg·m-2and 1.0 kg·m-2 Compared with the control group,the total nitrogen content of the soil at the mature stage was higher than that of the control group,and the opposite was observed under the treatment of 1.5kg·m-2.2.The research on the effect of biochar on the changes of various organ contents in the tillering stage and the mature stage of rice shows that,after applying biochar,compared with the control group,the 1.5 kg·m-2 treatment significantly reduced the Ni content in the roots of rice during the tillering stage of rice.,Cu content of stems,Cd content of leaves;1.0 kg·m-2 treatment can effectively reduce the Cu,Cd,Zn content of the roots;at maturity,the Cu content in brown rice after 1.0 kg·m-2treatment decreased by 17.19%,1.5 kg·m-2 treatment reduced the contents of Cd,Cr and Ni in brown rice,of which the Cr content decreased most obviously,reaching25.57%.3.The relationship between biochar and rice transfer enrichment of Cd,Cr,Cu,Ni,and Zn shows that the coefficient of rice transfer Cd and Zn is up to 1.5 kg·m-2,and its value exceeds 1 and is significantly higher than that of the control group..The 1.5kg·m-2treatment has the smallest concentration of Cr and Cd in brown rice than other treatments.The 1.0 kg·m-2 treatment enriches Cu and Ni in brown rice,and the 0.5kg·m-2 treatment enriches Zn in brown rice.The volume is the smallest compared with other treatments.After applying biochar,the total amount of heavy metals enriched in a single rice plant showed an upward trend compared with the control group.The total amount of Cr enriched in the whole plant under 0.5 kg·m-2 treatment was the largest,and that in the whole plant under 1.0 kg·m-2 treatment.The total amount of Ni enriched was the largest,and the total amount of Cd,Cu and Zn enriched in the whole plant was 1.5 kg·m-2.4.The results of biochar on the change of different forms of Cd,Cr,Cu,Ni,Zn in the soil show that The reduction rate of Cd content under 0.5 kg·m-2 treatment was 6.5times that of the control group,and the reduction rate of Ni content under 1.0kg·m-2treatment was as high as 57.55%,an increase of 22.80%compared with the control group.The 1.5kg·m-2treatment reduced the percentage of weak acid extractable Cd and oxidizable Cr,respectively,by 6.0%and 2.80%,and increased by3.60%residual Cr.The 0.5 kg·m-2and 1.0 kg·m-2 treatments increased 4.90%and 3.20%reducible and residual Cd,respectively,and the percentage of oxidizable Cd remained almost unchanged.The application of biochar has little effect on the Cr content of the weak acid extraction state and the reducible state.The weak acid extraction state and the oxidizable state Cu showed a decreasing trend with the increase of biochar,and the reducible state Zn,Cu,Ni,weak acid extraction state Zn With the increase of biochar,the oxidizable Zn is basically unchanged under the treatment of 1.0 kg·m-2and 1.5 kg·m-2. |
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