雅浦海沟南部海水低分子量有机酸的分布特征

Distribution Characteristics of Low Molecular Weight Organic Acids in the Southern Yap Trench

    摘要
  • 摘要: 本研究分析了雅浦海沟南部4个CTD站位以及海水-沉积物界面5个站位共74个海水样品中低分子量有机酸（Low Molecular Weight Organic Acids, LMWOAs）的浓度，初步探究了雅浦海沟南部海水LMWOAs的垂直分布特征及其与各海水化学与生物参数的相关关系。结果表明，雅浦海沟南部海水含有乙酸（Acetic Acid, AA）和甲酸（Formic Acid, FA）两种LMWOAs，浓度范围分别为0～43.64和4.88～47.89 μmol/L，浓度均值分别为(19.18±14.15)和(10.03±9.06) μmol/L，研究区域1 000 m水深处出现LMWOAs浓度的低值区。海沟东西侧海水LMWOAs浓度显著低于中部海水。雅浦海沟南部海水-沉积物界面上覆水中AA浓度较高，浓度范围为18.90～40.63 μmol/L，平均浓度为(33.93±8.22) μmol/L；FA浓度较低，浓度范围为5.09～14.82 μmol/L，平均浓度为(8.48±3.87) μmol/L；LMWOAs在西侧上覆水浓度高于东侧上覆水。雅浦海沟南部海水中AA、FA和总有机酸（Total Organic Acids, TOA）在溶解有机碳（Dissolved Organic Carbon, DOC）中的占比范围分别为0～17.92%、1.10%～25.66%和2.33%～25.66%，均值分别为7.52%、4.10%和11.62%，其AA浓度与DOC浓度存在极显著正相关关系，而FA浓度与总有机碳（Total Organic Carbon, TOC）浓度存在极显著正相关关系，FA浓度变化受海水微生物活动的影响更为显著。雅浦海沟不对称的“V”地形造成的“漏斗效应”导致其深层和深渊层海水容易积累LMWOAs，出现较高的LMWOAs浓度。

     

    Abstract: This study analyzed the concentrations of low molecular weight organic acids (LMWOAs) of 74 seawater samples from 4 CTD stations and 5 stations at the seawater-sediment interface in the Southern Yap Trench. Their vertical distribution characteristics and their correlations with various seawater chemical and biological parameters in the Southern Yap Trench were preliminarily explored. The results showed that the seawater in the Southern Yap Trench contained two kinds of LMWOAs, acetic acid (AA) and formic acid (FA), with concentration ranges from 0 to 43.64 and 4.88 to 47.89 μmol/L, respectively. Their average concentrations were (19.18±14.15) and (10.03±9.06) μmol/L, respectively. The low concentration area of LMWOAs appeared around the 1 000 m depth. The concentrations of LMWOAs in the seawater at the east and the west side of the trench was significantly lower than those at the central region of the Southern Yap Trench. In the overlying seawater from the sediment-seawater interface, the AA concentrations were higher, with a range of 18.90-40.63 μmol/L and an average concentration of (33.93±8.22) μmol/L; and the FA concentrations were lower, with a range of 5.09-14.82 μmol/L and an average concentration of (8.48±3.87) μmol/L. The concentration of LMWOAs was higher in the overlying seawater on the west side of the Southern Yap Trench and lower in the overlying seawater on the east side of the trench. The proportions of AA, FA and total organic acids (TOA) in the dissolved organic carbon (DOC) in the seawater of the Southern Yap Trench ranged from 0 to 17.92%, 1.10% to 25.66% and 2.33% to 25.66%, respectively; with mean values of 7.52%, 4.10% and 11.62%, respectively, with an extremely significant positive correlation between AA concentrations and DOC concentrations, and an extremely significant positive correlation between FA concentrations and total organic carbon (TOC) concentrations, and the FA concentrations were more significantly affected by the activity of marine microorganisms. The “ funnel effect” caused by the asymmetric “ V”-shaped topography of the Yap Trench facilitated the accumulation of LMWOAs in its bathypelagic and abyssal seawater layers, resulting in higher concentrations of LMWOAs.

     

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