山东烟台地区苹果果园土壤中DDTs和HCHs残留分布特征与来源解析

Distribution Characteristics and Source Apportionment of DDTs and HCHs in Soils from Apple Orchards in Yantai,Shandong Province

为研究不同土壤类型中有机氯农药的残留特征、降解程度和来源途径,采集了山东烟台9个不同地质单元苹果园根系土壤和剖面土壤样品,用电子捕获检测器气相色谱法测定其中的滴滴涕(DDTs)和六六六(HCHs)。结果表明,研究区所有类型根系土壤中DDTs和HCHs均未超出《土壤环境质量标准》的二级土壤限值(500 ng/g);土壤中DDTs的残留量及检出率均高于HCHs,DDTs检出率为100%,平均残留量为71.7ng/g,而HCHs的检出率为19.70%,平均残留量为7.9 ng/g;根系土壤中DDTs各异构体平均浓度依次为p,p'-DDT>p,p'-DDE>o,p'-DDT>p,p'-DDD,而HCHs大部分以α-HCH形式存在,部分以β-HCH、γ-HCH存在。不同类型土壤中有机氯农药残留分布特征明显不同:DDTs在棕壤土(臧家庄)中最高(145.5 ng/g),在中粗粒砂土(武宁)中最低(24.1 ng/g);而HCHs在细砂质壤土(蛇窝泊)中最高(27.9ng/g)。各剖面土壤DDTs均在<20 cm层位中残留最高。DDTs和HCHs来源解析表明:研究区土壤为好氧条件;麻砂棕壤(官道和桃村)、黏细壤土(牟平)、细砂质壤土(蛇窝泊)和棕壤土(臧家庄)近年来仍有新的DDTs输入;大部分根系土壤均未发现HCHs新来源,但麻砂棕壤(桃村)在HCHs禁用后可能仍存在林丹的使用。

In order to study characteristics of residues,levels of degradation and sources of organochlorine pesticides（OCPs）,Gas Chromatography-Electron Capture Detector（GC-ECD） was used to determine concentrations of DDTs and HCHs in 9 different types of root system soil and soil profiles from apple orchards in Yantai,Shangdong Province.None of the DDTs and HCHs in the soil samples exceeded the guidelines of 500 ng/g in the Chinese environmental quality standard for soils.The mean concentration of DDTs and HCHs were 71.7 ng/g and 7.9 ng/g,respectively.The detection rate of DDTs was 100%,while only 19.7% of soil samples contained HCHs.The mean levels of DDTs isomers hosted in the root system soil decreased in the following orders： p,p′-DDT p,p′-DDE o,p′-DDT p,p′-DDD,while HCHs isomers were mainly α-HCH with minor β-HCH and γ-HCH.Distribution of OCPs varied in different types of soil： highest concentration of DDTs occurred in brunisolic soil（Zangjiazhuang,145.5 ng/g） and lowest occurred in medium-grained sandy soil（Wuning,24.1 ng/g）.The highest concentration of HCHs occurred in fine sandy loam（Shewo,27.9 ng/g）.DDTs in soil profiles accumulated in depths within 20 cm.The results of source apportionment of DDTs and HCHs indicated all soil from the research area was aerobic.There were new sources of DDTs for linen sandy brunisolic soil（Guandao and Taocun）,fine loam（Muping）,fine sandy loam（Shewo） and brunisolic soil（Zangjiazhuang）.No new sources of HCHs for most root system soil were apparent,but lindane may still have been used in linen sandy brunisolic soil（Taocun） after HCHs were restricted in China.