典型农药污染地块土壤中异味物质的筛查与分布特征研究

针对我国农药污染地块修复过程中异味扰民的突出环境问题，开展地块土壤中异味物质的筛查，明确异味物质在土壤中的分布至关重要. 本文以某典型农药污染地块土壤为研究对象，通过对土壤气样品全扫描分析、异味清单比对、异味活度值计算、累计异味贡献率分析等方法，筛查确定土壤中主要的异味物质；基于筛查结果，通过土壤样品采集，应用GC-MS分析，查明土壤中主要异味物质的污染程度和空间分布. 结果表明:①该典型农药污染地块土壤中涉及二甲基硫醚、二甲基二硫醚、甲苯、三氯乙烯、二硫化碳、氯仿、邻-二甲苯、间/对-二甲苯、苯、噻吩、甲基环己烷、正己烷、四氯乙烯、乙苯和四氯化碳15种异味物质，异味活度值分别为7 287.5、2 755.6、714.8、676.7、438.5、294.5、229.4、74.7、55.4、50.0、49.6、18.9、3.1、1.7和0.6. ②累计异味贡献率超过90%的主要异味物质为二甲基硫醚、二甲基二硫醚、甲苯和三氯乙烯，四者最高含量分别为10.9、48.5、797.7和33 000.0 mg/kg，主要分布在除草剂车间、菊酯车间、敌敌畏车间、氧化制氯车间、百草枯车间和氧乐果车间等生产区域. ③异味物质含量普遍随土壤埋深的增加表现为先增后降，主要分布在1.8~6.8 m的粉质黏土和6.8~10.6 m的粉土中. 研究显示，农药污染地块土壤中异味物质种类复杂，可采用累计异味贡献率分析法进行筛查；地块土壤中异味物质的空间分布主要与生产过程、土壤埋深和土壤性质有关. 

Screening and Distribution Characteristics of Odorous Substances in Soil of Typical Pesticide-Contaminated Site

The prominent environmental problems caused by odors in the remediation of pesticide-contaminated sites in China have become important for screening the odorous substances in the soil and clarifying the distribution of odor substances in the soil. In this study, a typical pesticide-contaminated site was selected as the study area, the main odorous substances in the soil were screened by scan analysis of soil gas samples, compared with the odor list, and the odor activity values and cumulative odor contribution were calculated. Based on the screening results, soil samples were collected and analyzed by GC-MS to determine the extent of pollution and spatial distribution of the main odor substances in the soil. The results showed that: (1) The main odorous substances found at the site were dimethyl sulfide, dimethyl disulfide, toluene, trichloroethylene, carbon disulfide, chloroform, o-xylene, m/p-xylene, benzene, thiophene, methylcyclohexane, n-hexane, tetrachloroethylene, ethylbenzene, and carbon tetrachloride (15 kinds of odor substances). Their Odor Activity values were 7,287.5, 2,755.6, 714.8, 676.7, 438.5, 294.5, 229.4, 74.7, 55.4, 50.0, 49.6, 18.9, 3.1, 1.7 and 0.6, respectively. (2) The main odor substances with cumulative odor contribution of more than 90% were dimethyl sulfide, dimethyl disulfide, and toluene, trichloroethylene. The highest contents of these main odor substances were 10.9, 48.5, 797.7 and 33,000.0 mg/kg, respectively. The main distribution areas of these odorous substances on site included storage tank and dichlorvos production areas and herbicide, pyrethroid, oxidation chlorine production, paraquat, and omethoate workshops. (3) The vertical distribution generally showed a trend of increasing first and then decreasing. These odorous substances were mainly concentrated in the 1.8-6.8 m silty clay layer and the 6.8-10.6 m silt soil layer. The research shows that there are many kinds of odor substances in the soil of pesticide-contaminated sites, and the cumulative odor contribution analysis method can be used to screen the odor substances. The spatial distribution of odor substances in the soil of the study area is mainly related to the production process, soil depth, and soil properties.