To reconstruct the deposition rate of polychlorinated biphenyls (PCBs) in different historical periods and to examine the temporal and spatial trend of PCBs pollution, we analyzed the changes of PCBs concentration and deposition rate in peat cores and lake sediments, and evaluated the suitability of peat cores and lake sediments for studying PCBs deposition trend. Through the dating analysis of all samples, we found that peat bog could well record the historical sedimentation of PCBs. PCBs did not degrade in peat, and it was thus feasible to use peatland to examine the settlement of PCBs. In this study, the reconstruction time of ∑11PCBs in peat was from the beginning of 19th century to the beginning of 21st century. The mean inventory of ∑11PCBs in three peat cores of each bog changed between (37.0±5.4) and (47.2 ±27.8) μg·m-2, with the standard deviation between 14.9% and 58.9%. The highest concentration of ∑11PCBs was 6.8 ng·g-1DW, while the maximum deposition rate of reconstructed PCBs was up to 989.7 ng·m-2·a-1. The trend of deposition rate was first increasing and then decreasing. After the year 1980, the deposition rate was substantially decreasing, which was consistent with the prohibition of PCBs production in the United States in 1979. Meanwhile, the analysis of sediment samples in the lake near bog showed that concentration and maximum deposition rate of the lake sediment were comparable to those of the nearby bog. The concentrations of Di- to Hepta-PCB congeners were evenly distributed along the sediment profile. Therefore, lake sediments could not be used to analyze the historical sedimentary model of low order PCBs. This study reconstructed temporal and spatial variation of PCBs in atmospheric environment in different historical periods, which could provide basic data for the evaluation of regional environmental quality.
为了重建不同历史时期多氯联苯(PCBs)的沉降速率以研究其污染的时空变化趋势,本研究分析了PCBs在泥炭芯和湖泊沉积柱芯中浓度和沉降速率的变化规律,并评估了泥炭芯和湖泊沉积柱芯用于PCBs沉降变化研究的适用性。对采集柱芯进行定年分析发现,泥炭沼泽可以很好地记录PCBs历史沉降变化,并且泥炭中的PCBs没有出现降解情况,因此采用泥炭地研究PCBs沉降变化是可行的。本研究中泥炭地11种多氯联苯同系物(∑11PCBs)的重建时间为19世纪初至21世纪初,对泥炭中PCBs含量检测发现,每个沼泽的3个泥炭芯中∑11PCBs的单位面积埋藏量均值在(37.0±5.4)～(47.2±27.8) μg·m-2之间变化,标准偏差在14.6%～58.9%,∑11PCBs的最高浓度可达6.8 ng·g-1DW,重建的PCBs沉降最大速率可达989.7 ng·m-2·a-1。沉降速率的变化趋势为先增后减,1980年后明显下降,这与美国在1979年禁止生产PCBs相符。对沼泽附近湖泊的沉积物取样分析发现,湖泊沉积物柱芯各深度所对应的浓度和最大沉降速率与附近沼泽相近。但湖泊沉积物剖面中2～7阶PCBs同系物的浓度分布均匀,表明湖泊沉积物无法用于分析低阶PCBs的历史沉降变化。本研究重建了不同历史时期大气环境中PCBs的时空变化规律,可为评价区域环境质量提供基础资料。.
Keywords: lake sediment; ombrotrophic bog; polychlorinated biphenyls (PCBs); settlement change.