海南岛双池玛珥湖揭示的历史时期人类活动影响下大气汞沉降的高分辨率记录

以取自海南岛北部双池玛珥湖SCH17-04岩芯全长为420cm的沉积物为材料, 对其开展了AMS¹⁴C测年和总汞浓度、总有机碳、常量地化元素、干密度等指标的测试分析。通过对多代用指标的综合比对分析, 并结合历史文献资料, 着重探讨了815~1510A.D.时段内区域气候环境与人类活动影响下的汞沉积过程及其可能影响因素。研究结果表明: 在研究时段内, SCH17-04岩芯中汞浓度(Hg_-C)为0.22~3.11μg/g, 汞沉积通量(Hg_-AR)为0.01~1.92μg/(cm²·a)。进一步分析发现, 双池玛珥湖沉积物中汞浓度与各环境代用指标之间呈现出变化步调的不一致性, 揭示了有机质吸附、土壤侵蚀、气候变化、海洋释放等自然因素可能对沉积物中汞积累的贡献较为微弱。综合岩芯记录与史料记载分析发现, 主要与人类活动关系较为密切的大气汞沉降输入占据着主导地位, 其中人为汞信号始于约940A.D., 对应于五代十国时期, 并且在约940~1130A.D.(五代十国中后期和北宋)和约1320~1420A.D.(元朝中后期和明朝初期)期间, 特别是在后一时期, 出现显著的人为汞通量峰值阶段, 这与历史上海南岛人口数量变化趋势较为吻合, 揭示了人类活动(如金属冶炼和开采、战争叛乱、人口迁移等)在这些时期对自然界中的汞释放与积累具有重要影响。

A high-resolution record of atmospheric mercury deposition under the influence of historical human activities revealed by Shuangchi Maar Lake,Hainan Island

Mercury has a long history of being used by humans and released into the environment during the pre-industrial era. Yet, uncertainty exists regarding the timing and magnitude of mercury emissions during the pre-industrial era. Here, a 420cm-long sediment core(19°57'N, 110°11'E) from Shuangchi Maar Lake, northern Hainan Island, South China, was utilized for AMS 14C dates and measurements of total mercury concentration, total organic carbon, geochemical elements and dry density. Based on a thorough comparison and analysis of multi-proxy indicators and historical documents, the process of mercury deposition from 815A.D. to 1510A.D. and its potential influencing factors over the research period under the influence of regional climate, environment, and human activities were investigated. The results showed that Hg-C ranged from 0.22μg/g to 3.11μg/g, and Hg-AR varied from 0.01μg/(cm2 ·a) to 1.92μg/(cm2 ·a). Further investigation revealed that there were discrepancies between Hg-C and the environmental proxies, suggesting that natural processes like organic matter adsorption, soil erosion, climate change, and marine degassing might have contributed little to the mercury buildup in the sediments. Based on the analysis of core records and historical documents, the atmospheric mercury input, which was mostly due to human activities, was dominant. The beginning of the anthropogenic mercury signal, which corresponded to the Five Dynasties and Ten Kingdoms period, started around 940A.D. There were substantial peak stages of anthropogenic mercury flux during about 940~1130A.D.(middle and late Five Dynasties and Ten Kingdoms and Northern Song Dynasty)and about 1320~1420A.D.(middle and late Yuan Dynasty and early Ming Dynasty), particularly in the latter period. The variation trend of anthropogenic mercury flux in the core was determined to be consistent with the curve of historical population change in Hainan Island. It was revealed that during these periods, human activities(such as metal smelting and mining, war rebellion, population migration, etc.)had a significant impact on the emission and accumulation of mercury in the environment.