越南红河水下三角洲表层沉积物中有机物分布及来源分析

DISTRIBUTION AND SOURCE OF ORGANIC MATTER IN THE SURFACE SEDIMENTS FROM THE RED RIVER SUBAQUATIC DELTA, VIETNAM

采用总有机碳(OC%)、总氮(TN%)、有机碳同位素组成(δ13C)以及木质素方法,对越南红河水下三角洲表层沉积物进行研究,结合粒度数据,分析其有机物分布以及来源。结果表明,红河口表层沉积物的(C/N)mol在2.7—18.7之间;有机碳(OC%)和总氮(TN%)在近岸粒径大的站位含量低,粒度小的站位含量高;δ13C(‰)在22.8—25.9之间;Λ8(mg/100mgOC)在0.2—4.9之间。使用简单二端元模型计算后发现陆源有机物在表层沉积物中占的比例在3.7%—89.5%,并且与粒径大小有关,粒径大陆源有机物比例低,粒径小陆源有机物比例高,说明水动力分选是控制陆源有机物分布的主要因素。C/V和S/V分别为0.29±0.13和0.87±0.18,表明该区域的陆源有机物来源于被子植物的草本和木本部分混合。V系列的酸醛比(Ad/Al)v在0.38—2.43之间,平均值为0.70,说明该区域陆源有机物经历了中等程度的降解。

The Red River in Vietnam is a typical tropical river, and its continental shelf receives a lot of terrestrial input Several surface sediments from the Red River subaqueous delta were collected and analyzed for elemental, stable carbon isotopes and lignin phenols. C/N ratios varied from 2.7 to 18.7, corresponding with bulk δ^13C （‰） values of-22.8‰- -25.9‰. A8 （A8 = sum of vanillyl, syringyl and cinnamyl phenols produced by CuO oxidation of 100mg organic carbon） values lied between 0.2 and 4.9mg/100mgOC, which were much higher than those of other reported areas. Besides, A8 values showed obvious linear relationship with δ^13C, which implied that a simple two end-member model could be applied to calculate the contribution of terrestrial organic matter input. The results showed the percentage of terrestrial organic matter in the surface sediments varied from 3.7% to 89.5%, which was strongly related to the grain size. C/V （0.29±0.13） and S/V （0.87±0.18） ratios indicated that this terrestrial organic matter originated from the mixture of woody and non-woody angiosperm plants. （Ad/Al）v values （average value 0.70） suggested that this terrestrial organic matter in the subaqueous delta was moderately degraded.