鸡粪热裂解对重金属Mn、Cu、Zn和Cr生物有效性的影响

The effects of chicken manure pyrolysis on the bioavailability of Mn,Cu,Zn,and Cr

畜禽粪便直接农用引起的重金属污染是社会普遍关注的问题,探索如何有效降低畜禽粪便重金属生物有效性的技术是急需解决的难题.本文通过分析鸡粪(CM)裂解前后Mn、Cu、Zn和Cr等4种重金属形态分布变化,并采用林地大型盆栽试验研究添加CM和鸡粪炭(CMB)处理对湿地松地上部分重金属吸收状况的影响.结果表明,与CM直接还田相比,添加CMB(400℃)处理降低Mn、Cu和Zn在湿地松地上部分的吸收量和富集系数,而处理之间植株Cr元素的吸收量和富集系数差异不显著.Tessier连续提取结果表明,Mn、Cu和Zn的交换态含量分别由CM的94.8、10.0和34.9 mg·kg^-1显著降为CMB的16.6 mg·kg^-1、未检测出和1.8 mg·kg^-1.CM裂解成CMB后,Cr元素残渣态含量显著提高.从元素质量守恒来看,CM制成CMB后Mn、Cu、Zn和Cr损失率分别为29.3%、35.6%、33.5%和3.3%.裂解油中Mn、Cu、Zn和Cr的金属总量分别占CM金属损失量的51.7%、53.0%、32.9%和13.1%.CM裂解成CMB后,91.7%的交换态Mn、几乎100%交换态Cu和97.5%的交换态Zn会随裂解转化为铁锰氧化态、有机结合态和残渣态形式或挥发而降低有效性.1年盆栽试验结果表明,在CMB处理中,土壤Mn、Cu和Zn交换态含量显著低于CM处理.相关性分析发现,植物体内重金属吸收量与土壤金属有效态含量显著相关,而与总量相关性不明显.由此可见,将鸡粪制成鸡粪炭是一种有效降低Mn、Cu和Zn生物有效性的途径.

Heavy metals pollution caused by application of poultry manure directly into farmland has been widely concerned,and effectively decreasing the bioavailability of heavy metals in poultry manure is urgently needed.This paper studied the speciation distribution changes of Mn,Cu,Zn and Cr before and after chicken manure(CM)pyrolysis and the effects of CM and chicken manure biochar(CMB)on heavy metal uptake in above ground part of Pinus elliottii by mesocosm experiment.The results show that the application of CMB(400°C)significantly reduced the uptake and enrichment coefficient of Mn,Cu and Zn in aboveground part of Pinus elliottii when compared to CM application,while no significant differences of Cr uptake and enrichment coefficient were found.Tessier sequential extractions results show that the content of exchangeable Mn,Cu and Zn significantly decreased from 94.8,10.0 and 34.9 mg·kg^-1 in CM to 16.6 mg·kg^-1,undetected level and 1.8 mg·kg^-1 in CMB,respectively,and the residual fraction of Cr was significantly increased after CM was pyrolyzed to CMB.The loss of Mn,Cu,Zn and Cr were 29.4%,35.6%,33.5%and 3.3%,respectively,when CM was converted to CMB.The amounts of Mn,Cu,Zn and Cr remained in bio-oil accounted for 51.7%,53.0%,32.9%and 13.1%of the total lost Mn,Cu,Zn and Cr,respectively.After CM was converted to CMB,91.7%of available Mn,nearly 100%of available Cu and 97.5%of available Zn in CM were transformed to fraction bounded to Mn-Fe oxides,fraction bounded to organic matters and residual fraction or volatilized during pyrolysis.After one year field mesocosm experiment,the soil exchangeable Mn,Cu and Zn in CMB treatment were lower than those in CM treatment.Correlation analysis results show that the uptake amounts of heavy metals in plant were positively related to the soil available heavy metals content,but not related to the total content.Our results suggest that converting CM to biochar provides a feasible way to reduce the bioavailability of Zn,Mn and Cu.