氰(C_2N_2)在3种类型土壤中的吸附与消解动态

Adsorption and Degradation Dynamic of Cyanogen in Three Types of Soil

氰(C2N2)是一种具有替代溴甲烷潜力的新熏蒸剂,明确C2N2在3种类型土壤(沙质土、壤土和粘质土)中的吸附行为与消解动态对C2N2的安全应用与风险评估具有重要的意义。采用静态平衡法研究了C2N2在3种类型土壤中的吸附与挥发行为,采用溶剂顶空法测定了C2N2在3种类型土壤中的消解动态。结果表明,土壤对C2N2具有较强的吸附能力,熏蒸4h,85%以上的C2N2被土壤吸附,熏蒸12h,98%以上的C2N2被土壤吸附,其吸附强度为粘质土>壤土>沙质土。熏蒸期间C2N2在沙质土、壤土和粘质土配气瓶内消退较快,熏蒸48h的消退率分别为94.12%、96.70%和98.27%。同时,C2N2在土壤中可快速转化产生HCN,熏蒸后1h达到最大值,其浓度为粘质土>壤土>沙质土,而后快速下降。通风后C2N2及其转化产物HCN在土壤中易于挥发和消解,C2N2和HCN在3种类型土壤中的挥发速率相近,在沙质土、壤土和粘质土中C2N2的消解半衰期分别为15.82、14.56h和12.43h,HCN分别为17.52、20.82h和24.27h。

Cyanogen（C2N2） is a new type of fumigant that has a potential to replace methyl bromide.So it is of important significance to ascertain the absorption behaviour and degradation dynamic of C2N2 in three types of soil（sand,loam and clay） for its safety application and risk assessment.Absorption and volatilization behaviour of C2N2 in three types of soil was investigated using the static equilibrium method.Degradation dynamics of C2N2 in three types of soil was determined using the solvent headspace method.Results showed that three types of soil had a very high C2N2 adsorption capacity with a rate being over 85% within 4 h of fumigation and over 98% within 12 h.The order of adsorption capacity was clay,loam and sand soil.The reduction rates of C2N2 in the headspace over three types of soil（sand,loam and clay） were very high within fumigation,94.12%,96.70% and 98.27% within 48 h of fumigation,respectively.The absorbed C2N2 could be quickly transformed into HCN.The concentration of HCN peaked within 1h of fumigation in three types of soil,in which was highest in clay soil,medial in loam soil and lowest in sand soil,and quickly began to drop after 1h of fumigation.Under the aeration condition,C2N2 and HCN transformed from C2N2 were easily volatilized and degradated in soil,and their volatilization rates in three types of soil were similar.The half lifes of C2N2 in sand,loam and clay soil were 15.82 h,14.56 h and 12.43 h,respectively,and the half lifes of HCN were 17.52 h,20.82 h and 24.27 h,respectively.