杭州湾表层沉积物有机碳分布、来源及近20年来的变化

Distribution,provenance and changes in the past 20 years of organic carbon in the surficial sediments in Hangzhou Bay

中文关键词:  表层沉积物  有机碳  来源  杭州湾

英文关键词:surficial sediments  organic carbon  provenance  Hangzhou Bay

中文摘要:

      根据2002年、2008年、2012年、2017年和2022年夏季采样分析结果，对杭州湾表层沉积物中有机碳（TOC）时空分布变化进行了研究。结果表明研究区TOC平均值分别为0.55%（n=16）、0.50%（n=112）、0.44%（n=38）、0.53%（n=38）和0.51%（n=38），总体上呈现南北高东西低的“X”形平面分布特征，高值区出现在北岸金山至南汇咀海域和南侧镇海至慈溪海域，相关性分析表明TOC分布受到沉积物类型的控制，主要赋存于细颗粒沉积物内。沉积物的氧化还原环境也对TOC分布有显著影响。分区进行5个年份TOC统计分析显示，20年来北部海域先减后增，变化较为明显，南部和东部海域2017年增大之后减小，西部海域变化不大。TOC随时间的变化受到自然条件和人为活动造成的长江入海泥沙和有机物质通量下降、海洋源增加等因素的影响。C/N、δ13C特征表明，研究区沉积物中有机碳陆源贡献比例大都在30%～70%，站点差异较大，北岸近岸海域和东南侧海域陆源有机碳比例较高，湾中部和东部海域有机碳的海洋源比例较高。

英文摘要:

      Based on the sampling and labortary testing in the summer of 2002, 2008, 2012, 2017 and 2022, the distribution pattern,provenance and changes in the past 20 years of organic carbon of the surface sediments in Hangzhou Bay were discussed. The results showed that the average total organic carbon (TOC)content of 2002，2008，2012，2017 and 2022 were 0.55%、0.50%、0.44%、0.53%和0.51%, respectively, higher in the north Jinshan-Nanhui tidal trough(＞0.6%) and south Zhenhai and Cixi offshore muddy areas(＞0.5%) and lower in west sandy (＜0.4%) and the east region (0.4%～0.5%)of the bay. Correlations between TOC and grain size and Eh indicate that hydrodynamically driven sediment differentiation and redox environment exert a significant control on the transport and accumulation of sedimentary organic carbon in Hangzhou Bay, with its preferential deposition in the fine-grained sediments. Statistical analysis of five periods of TOC in four areas showed obvious decrease and then increase in the northern area, increased over 2002 to 2017 then reduced in the southern and eastern areas and no clear change in the western area. related to potential effects of the declining sediment and organic matter loads caused by natural conditions change and anthropic influences. The C/N、δ13C characteristics of the sediment showed that terrestrial contribution of the TOC was 30%～70%, vared widely in different areas in Hangzhou Bay, with more land sources which mainly carried by Changjiang River suspended sediments in the northern and south-eastern areas, while more marine origin in the central and eastern areas of the bay.