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对海南岛万泉河口沙美内海柱样K3和K4沉积物进行生物地球化学指标总有机碳(TOC)、总氮(TN)、有机碳同位素(δ13C)、氮同位素(δ15N)的分析,以及210Pb定年了解其近代变化特征,追踪沉积物有机质来源的变化,提取沉积环境演变及人类活动的信息。K3中TOC的变化介于0.51%~1.12%,K4变化介于0.43%~1.49%,而其随时间的变化反映了流域内人类活动的历史。17世纪TOC含量明显增加记录了明末清初开始流域内广泛种植农作物的活动,19世纪以来TOC含量逐渐增加,至现代达最高值,对应了工业革命以来人类活动的增强。K3和K4的δ13C值变化分别在-24.38‰~-21.02‰之间和-24.74‰~-20.17‰之间,δ15N值变化分别在2.20‰~4.62‰之间和2.39‰~5.02‰之间,映证了本区沉积物有机质是陆源物质和海洋物质混合的特点。明末清初开始流域内广泛种植玉米等农作物造成δ13C值增加和δ15N值减少;自19世纪以来至现在,该区的经济活动增加,人口的持续增长,尤其是近50年来化肥农药的大量使用,造成陆源输入的有机碳含量大幅增加,使δ13C值减少和δ15N比值增加。δ13C值自19世纪以来就逐渐变轻,说明陆源和海洋有机碳的比例发生了变化,较轻的陆源有机碳比例相对增加,较重的海洋有机碳比例相对减少,反映了玉带滩沙坝的增长、沙美内海封闭、海水交换作用减少的状况。C/N比值分别从底部的16.19和17.36到顶部减小为11左右,自19世纪以来呈明显减小的趋势也反映了沙美内海泻湖自生的藻类有机质供应越来越多,也说明了其逐渐封闭、水动力条件越来越弱,与外海的交换作用逐渐减少的状况。
The biogeochemical indexes TOC, TN, δ13C and δ15N of K3 and K4 sediments in the Shameihai sea-mouth samples of Wanquan estuary of Hainan Island were analyzed, and 210Pb Studying the changing features of modern times, tracking the changes of sources of sediment organic matter, and extracting the information of sedimentary environment evolution and human activities. The change of TOC in K3 ranged from 0.51% to 1.12%, and the change of K4 ranged from 0.43% to 1.49%, while the change with time reflected the history of human activities in the basin. In the 17th century, the TOC content increased markedly and recorded the extensive planting of crops in the basin in the late Ming and early Qing dynasties. Since the 19th century, the TOC content gradually increased to the highest level in the modern era, corresponding to the enhancement of human activities since the Industrial Revolution. The δ13C values of K3 and K4 varied from -24.38 ‰ to -21.02 ‰ and from -24.74 ‰ to -20.17 ‰, respectively. The δ15N values varied from 2.20 ‰ to 4.62 ‰ and from 2.39 ‰ to 5.02 ‰, respectively, This shows that the organic matter in the sediment is characterized by the mixture of terrestrial and marine materials. Since the late Ming and early Qing dynasties began to plant corn and other crops extensively in the basin, resulting in an increase of δ13C value and a decrease of δ15N value. Since the19th century up till now, the economic activity of the area has increased and the population has continued to grow, especially in the past 50 years , Resulting in a significant increase in the input of organic carbon by terrestrial sources, reducing the δ13C value and increasing the δ15N ratio. The δ13C value has gradually become lighter since the 19th century, indicating that the ratio of terrestrial and marine organic carbon has changed, the proportion of lighter terrestrial organic carbon has increased, and the proportion of heavier marine organic carbon has decreased, reflecting that of the Jade Belt Dam Growth, the closure of the Shamian Sea, the reduction of seawater exchange. The C / N ratio decreased from 16.19 and 17.36 at the bottom to 11 at the top, and the decreasing trend since the 19th century also reflected the increasing supply of organic algae in the spontaneous algae of the Salmonella lagoon, Closed, the hydrodynamic conditions are getting weaker, with the exchange of the sea off the situation gradually reduced.