稻田土壤可溶性有机碳荧光组分对砷甲基化的影响

Effects of soluble organic carbon fluorescence components on arsenic methylation in paddy soil

以浙江省绍兴市上虞地区砷污染水稻土为对象,采用厌氧培养试验研究了秸秆和猪粪两种不同有机物料施用后土壤溶液中甲基砷及有机碳荧光组分含量变化,初步探索了两者可能存在的关联。结果表明:秸秆与猪粪处理及其不同添加量水平显著影响土壤溶液中甲基砷浓度,厌氧培养5 d后,秸秆处理3种添加量(分别以0.5%、1.0%和1.5%的总有机碳添加量计)水平下的甲基砷浓度分别增加了40.3%、24.2%和24.0%,猪粪处理3种添加量(分别以0.5%、1.0%和1.5%的总有机碳添加量计)水平下的甲基砷增加量低于秸秆处理,增幅分别为15.5%、6.9%和3.8%;厌氧培养前后土壤溶液中总有机碳消耗量与甲基砷增加量呈显著正相关(P<0.05);秸秆与猪粪处理后土壤溶液中有机碳荧光组分和性质存在明显差异,秸秆源有机碳的腐殖化程度低,生物可利用性相对更高,且含有更多的可溶性微生物副产物(SMP)、芳香蛋白类Ⅰ(APⅠ)和芳香蛋白类Ⅱ(APⅡ);厌氧培养5 d后,荧光指数、芳香蛋白类、富里酸类物质(FA)和腐植酸类物质(HA)与甲基砷浓度均呈显著正相关(P<0.05),而腐殖化指数与甲基砷浓度负相关,但相关性不显著(P>0.05)。综合来看,不同类型有机物料降解后有机碳荧光组分存在明显差异,其中APⅡ、FA和HA浓度可能是影响砷甲基化的重要因素,相关结果有利于明确稻田砷甲基化过程的关键碳分子形态以及服务于今后水稻直穗病预警防控。

The difference between methylated arsenic and organic carbon fluorescence components in soil solution after application of two different organic materials,straw and pig manure,was investigated through an anaerobic cultivation experiment in arsenic-contaminated paddy soil in Shangyu area of Shaoxing City,Zhejiang Province.The possible relationship between methylated arsenic and organic carbon fluorescence components was preliminarily explored.The results indicated that straw and pig manure treatment at different addition levels significantly affected the content of methylated arsenic in soil solution.After 5 days of anaerobic cultivation,methylated arsenic increased by approximately 40.3%,24.2%,and 24.0%under three application levels of pig manure addition(0.5%,1.0%,and 1.5%,respectively,calculated based on total organic carbon);the increment of methylated arsenic under pig manure treatment was lower than that under straw treatment,with an increase of 15.5%,6.9%and 3.8%under three application levels of pig manure addition(0.5%,1.0%,and 1.5%,respectively,calculated based on total organic carbon).The consumption of total organic carbon in soil solution was significantly positively correlated with the increase of methylated arsenic after anaerobic cultivation(P<0.05).Significant differences were observed in the fluorescence composition and properties of organic carbon in soil solution under straw and pig manure treatment;the organic carbon fromstraw source had lower humification degree, higher bioavailability and more soluble microbial products(SMP), aromatic protein Ⅰ(APⅠ),and aromatic protein Ⅱ(APⅡ). After 5 days of anaerobic cultivation, the fluorescence index, aromatic proteins, fulvic acid(FA), andhumic acid(HA)were significantly positively correlated with the content of methylated arsenic(P<0.05), and the humification index wasnegatively correlated with methylated arsenic content(P>0.05). In summary, the organic carbon fluorescence components are significantlydifferent after degradation of different types of organic materials;APⅡ, FA, and HA contents may be important factors affecting arsenicmethylation.