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青藏高原中部表层土壤中多氯联苯的分布和手性特征
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摘要
青藏高原中部地区这个持久性有机污染物(POPs)全球运移研究的重要背景区域,采集了海拔在3711 m到5352 m之间的44个表层土壤样品,以及各采样点相对应的草样品。分析测定了土壤样品中多氯联苯(PCBs)的122种同系物的含量,PCBs的总含量为66.98~150.81 ng/kg,平均含量为100.64 ng/kg。通过皮尔森相关性分析发现PCBs的总含量与采样点的高度和土壤样品的粘土矿物含量呈显著线性正相关。测定了CB-95、CB-136和CB-149的对映体分数(EF),发现CB-136和CB-149均以右旋对映体分子为主,CB-95的洗脱顺序不确定,但有相类似的趋势。对EF值和可能的影响因素,包括含量、粘土矿物含量、土壤有机碳含量、高度、纬度和经度之间进行了皮尔森相关分析,发现CB-95、CB-136和CB-149的EF值与采样高度和各自含量呈正相关,可能的解释是环境空气温度随高度增加而降低,高山冷捕获作用加强,使得空气中沉降到土壤的PCBs的量随高度增加而增加,并引起EF值的变化。对该现象形成机制的进一步讨论,需要空气监测数据等更多的研究。在对映体的水平上研究手性农药的环境地球化学行为,可以更准确的评估其对人类健康以及生态环境的危害。
引文
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