汞(Hg)元素作为一种全球性循环元素,对环境的影响正逐渐成为人们关注的焦点之一.为揭示寒旱区达里诺尔湖沉积物的Hg污染历史及人类活动对湖泊沉积物中Hg污染的影响,通过采集湖泊沉积物岩芯(编号DL1),在建立DL1岩芯沉积地层年代框架的基础上,结合沉积物粒度特征、总有机质(TOC)含量等指标参数的变化,对DL1岩芯记录的地质历史上的Hg含量变化特征及环境意义进行了综合分析.结果显示,沉积物记录的Hg元素污染具有明显的阶段性变化特征: 2400~ 1400 cal. a BP,Hg含量呈逐渐降低趋势,期间降水量呈逐步减少趋势,区域气候显著干旱; 1400~ 200 cal. a BP,Hg含量相对稳定,呈小幅度波动变化,对应了区域气候的干-湿交替;近200 cal. a BP以来,Hg含量明显增加,这可能是受人类活动影响的结果.整体上,地质历史上DL1沉积物中Hg含量变化受气候干冷-暖湿交替周期性变化影响较大.而近200 cal. a BP来Hg与TOC等指标间显著正相关,则显示了沉积物中有机质可能吸附了大量的Hg元素,使其呈顶端富集趋势,进而对湖泊水生态环境造成影响.
英文摘要:
Mercury (Hg) as one of the global circulation elements has become the focus of public attention with respect to its impact on the environment. In order to get a better understanding of the historical contaminant processes and effects of Hg by human activities,a core (DL1) was sampled from the sediment in Dali-Nor Lake. The change characteristics and environmental significance of Hg were analyzed based on the sedimentary strata age,variation of sediment grain size,and total organic matter (TOC) content. The results showed that the contents of Hg recorded in the sediment had obvious characteristics of stage change. According to the chronological order,the sediment characteristics could be obviously divided into three stages. The first stage was from 2400 cal. a BP to 1400 cal. a BP. The Hg contents showed a decreasing trend during this period. This indicated that the precipitation decreased gradually and the regional climate was significantly drought. The second stage was from 1400 cal. a BP to 200 cal. a BP. The Hg contents slightly fluctuated with time,indicaing that the climate maintained steady with alternative dry and wet changes. The third stage was since 200 cal. a BP with sharp increase of Hg content. This is most likely due to the effects of human activities. Overall,the change of Hg contents in DL1 core was mainly influenced by the dry-cold and warm-wet alternative changes of the climate. The positive correlation between Hg and TOC contents in the past 200 years showed that a large amount of Hg might be adsorbed by the organic matter,which leads to an enrichment tendency on the top layer. This in turn impacts the ecological environment of the lake.