崇明岛湿地沉积物中六六六的长期变化趋势

采用同位素稀释质谱法,利用高分辨率气相色谱-高分辨率质谱法(HRGC-HRMS)分析测定了崇明岛东滩柱状沉积物样品的30个层段中HCHs的含量,对其垂直分布特征进行了初步探讨。沉积物中HCHs均被检出。东滩湿地沉积物中总∑HCHs含量范围为0.35~0.98ng·g-1dw,平均值为0.64ng·g-1dw,属于轻度污染。HCHs呈现明显的周期性变化。采用时间序列分析方法,统计分析了近60年来东滩湿地沉积物中HCHs变化的总体趋势与主要振荡周期。长期变化趋势表明东滩沉积物中HCHs在上世纪50年代初开始增长,高峰期出现在上世纪60至70年代。一些异构体在我国停止生产HCHs后,没有明显的下降趋势。频谱分析结果表明HCHs的分布表现出具有周期为大约8年的振荡特征,可能与气候变化周期相关。

Long-term Variation Trend of HCHs in the Sediment Core of Chongming Island Wetland

The concentrations of hexachlorocyclohexanes (HCHs) in the sediment cores taken from the Dongtan Wetland at the Yangtze River Estuary of the East China Sea were measured by isotope dilution mass spectrometry (IDMS) with HRGC-HRMS. The vertical distribution characteristics of HCHs concentrations with depth and possible influence by climate changes were preliminarily discussed. HCHs were found in all sediment layers. The total HCHs concentrations range from 0.35 to 0.98 ng·g^-1 dw with the average of 0.64 ng·g^-1 dw for the Dongtan Wetland, showing a low pollution level. The vertical distributions of HCHs isomers in the cores showed significant periodic variations. By time-series analysis, the long-term variation trends and frequency spectra of HCHs in the sediment cores of the Dongtan Wetland during the last 60 years were discussed. The long-term variation trends of HCHs in the wetland showed that these chemicals began to rise in the early 1950s with the maxima during the 1960s~1970s. Some isomers did not show significant declining trends after their productions were banned. The time-series generally show an 8-year periodicity, suggesting an influence of ENSO.