近4万年来雷州半岛北部地区汞沉积及其影响机制

雷州半岛地处热带北缘,受东亚季风影响强烈。以取自雷州半岛北部下录地区的埋藏泥炭沉积作为研究材料,测试分析了该岩心的汞浓度及其分布情况,将测试结果与其他气候环境代用指标如孢粉、炭屑、烧失量（LOI）以及有机碳同位素（δ13C_org）等进行对比分析,讨论自MIS（Marine Isotope Stages）-3晚期（约40 cal ka B.P.）至全新世早期（约6.9 cal ka B.P.）区域气候与环境变化影响下的汞沉积过程及可能的影响机制。结果显示:近4万年以来,沉积物的汞浓度与乔木类孢粉浓度的变化较吻合,两者之间显示出较高的相关性,揭示了晚更新世晚期以来,森林群落作为重要的地表汞库,在地区汞沉积过程中起到固定、储存和传输作用。此外,汞浓度与岩心中炭屑沉积通量（指示了区域性野火发生状况）的变化存在相反趋势,反映了区域性野火活动对地表植被以及土壤有机质的焚毁破坏,造成地表汞向大气的释放,不利于汞在地表和沉积物中的沉积与保存。对比不同区域的汞沉积记录发现,晚更新世晚期以来,下录泥炭汞浓度记录与全球其他地区汞记录、粉尘记录等具有较高的相似度,特别是MIS-2时期均存在明显峰值,反映了全球气候变化影响下,大气粉尘沉降对地表汞的输送和沉积具有较大贡献。

Deposition and Possible Influence Mechanism of Mercury in Northern Leizhou Peninsula over Past 40000 Years

Leizhou Peninsula is located in the northern tropics of China, which is strongly affected by the East Asian monsoon. A peat sediment core was drilled in Xialu, northern Leizhou Peninsula and the mercury concentration in the core was measured. Comparison and analysis are discussed regarding pollen concentration, charcoal concentration, loss on ignition （LOI） and organic carbon isotope （δ13C_org） in the core, the mercury deposition process and its possible impact mechanism driven by regional climate change from the late Marine Isotope Stages-3 （MIS-3） （~40 cal ka B.P.） to Early Holocene （~6.9 cal ka B.P.）. The results show a high correlation between the mercury concentration and tree pollen concentration in the core, which may indicate that the forest community was the main mercury pool on the ground surface, storing and transporting atmospheric mercury during its deposition. Conversely, the opposite trend was evident for concentration of mercury compared to charcoal content （which indicates regional paleofire events）, an indication that wildfires had burnt and destroyed forest and surface soil organic matter, causing the emission of mercury from the surface to the atmosphere, thus tending to prevent its deposition and storage in surface sediment. A comparison of mercury deposition records in different regions shows a close similarity between mercury records in Xialu peat sediments and those in other parts of the world. Records from the MIS-2 period in particular show synchronous typical peaks, indicating that atmospheric dust deposition contributed greatly to the transportation and deposition of surface mercury under the influence of global climate change.