淹水条件下羊粪生物炭对重金属复合污染土壤中Pb、Zn有效性影响

Effect of Sheep Manure Biochar Application Under Flooding Condition on the Availability of Pb and Zn in Heavy Metal Contaminated Soil

【目的】探讨淹水条件下羊粪生物炭对重金属复合污染土壤中Pb、Zn有效性的影响,为矿区重金属污染农田土壤治理提供依据。【方法】以云南某铅锌矿区附近受污染的农田土壤为研究对象,通过静态培养试验,研究淹水条件下不同添加量(0%、2.5%、5.0%和7.5%)羊粪生物炭对污染土壤中pH和Pb、Zn有效性的影响,并用毒性特征淋溶方法(TCLP)对其生态环境风险进行评价。【结果】与对照相比,羊粪生物炭处理土壤pH值提高0.04~0.11个单位,土壤有效态Pb、Zn质量分数显著降低32.01%~58.09%、6.44%~9.15%,土壤pH与土壤有效态Pb、Zn质量分数分别呈极显著负相关和显著负相关;从重金属赋存形态来看,羊粪生物炭明显促进土壤中Pb、Zn钝化,其中5.0%羊粪生物炭处理下钝化效果最佳,土壤中更稳定的可氧化态和残渣态Pb质量分数最高、分别为64.05%和27.50%;土壤中Zn主要向可氧化态转化,残渣态Zn为降低趋势,但降幅较小。随着羊粪生物炭添加量增加,TCLP提取态Pb、Zn质量分数均显著降低,可有效降低污染农田土壤生态风险。【结论】针对铅锌矿区附近受重金属污染农田土壤,采用淹水配施羊粪生物炭的方法,可降低土壤中Pb、Zn有效性和生态风险,5.0%羊粪生物炭添加量对土壤重金属Pb、Zn的钝化效果最佳。

【Objective】The study was conducted to explore the effect of sheep manure biochar on the availability of Pb and Zn in soil polluted by compound heavy metals under flooding conditions,and provides the basis for controlling heavy metal pollution of farmland soil.【Method】Using the polluted farmland soil near a lead-zinc mining area in Yunnan as the research object,static culture experiments were conducted to study the effects of different addition rates of sheep manure biochar(0%,2.5%,5.0%and 7.5%)on the pH and availability of Pb and Zn in polluted soil under flooding condition.And the ecological and environmental risks were evaluated by the toxicity characteristics leaching procedure(TCLP).【Result】Compared with the control,the soil pH value of sheep manure biochar treatment increased by 0.04-0.11 units,and the mass fractions of soil available Pb and Zn were significantly reduced by 32.01%-58.09%and 6.44%-9.15%,respectively.The soil pH and mass fractions of soil available Pb and Zn showed extremely significant negative correlation and significant negative correlation,respectively.From the perspective of heavy metal occurrence forms,sheep manure biochar significantly promoted the passivation of Pb and Zn.Among them,5.0%sheep manure biochar treatment had the best passivation effect,promoting the transformation of heavy metal Pb into more stable forms in soil,resulting in the highest mass fractions of oxidizable and residual forms,which were 64.05%and 27.50%,respectively.In the soil,Zn mainly transformed into an oxidizable state,but residual Zn showed a decreasing trend with a relatively small decrease.The mass fractions of Pb and Zn extracted by TCLP significantly decreased with the increase of biochar addition rate,effectively reducing the ecological risk of polluted farmland soil.【Conclusion】For heavy metal contaminated farmland soil near lead-zinc mining areas,the method of flooding combined with applying sheep manure biochar can reduce the availability and ecological risks of Pb and Zn in soil.The addition amount of 5.0%sheep manure biochar has the best passivation effect on soil heavy metals Pb and Zn.