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首页> 外文期刊>Estuarine Coastal and Shelf Science >Distribution and sources of particulate organic matter in the water column and sediments of the Fly River Delta, Gulf of Papua (Papua New Guinea)
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Distribution and sources of particulate organic matter in the water column and sediments of the Fly River Delta, Gulf of Papua (Papua New Guinea)

机译：巴布亚湾（巴布亚新几内亚）的弗莱河三角洲水柱和沉积物中有机颗粒物的分布和来源

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摘要

Suspended particles from surface and bottom waters and surficial sediments from the seabed were collected throughout the Fly River subaqueous delta region during the monsoon season in January 2003. Because of the unusually low river discharge associated with a strong El Nino, water-column salinities were relatively high (10 to 32) throughout most of the delta, with brackish salinities (< 10) only measured within the main distributary channel of the Fly River. The concentration and composition of particulate organic matter (POM) in these samples showed distinct spatial differences and marked contrasts between water column and seabed samples. Overall, relatively low concentrations of total suspended solids (TSS), particulate organic carbon (POC) and particulate nitrogen (PN) were measured in surface (27 ± 50, 0.83 ± 1.2, and 0.05 ± 0.05 mg/L, respectively) and bottom (400 ± 743, 7.1 ± 7.3, and 1.7 ± 7.2 mg/L, respectively) waters throughout the delta. Particles in both surface and bottom waters displayed elevated organic carbon contents (%OC > 4 wt.%), relatively high organic carbon:nitrogen molar ratios (OC:N > 20 mol:mol) and quite depleted stable isotopic compositions of organic carbon (δ~(13)C_(OC) < -27per thousand). In contrast, surface sediments in the seabed displayed spatially uniform compositions that were characterized by markedly lower %OC contents (1.1 ± 0.8 wt.%), lower OC:N ratios (17 ± 9 mol:mol) and relatively enriched δ~(13)C_(OC) compositions (-25.5 ± 1.1 per thousand). The radioisotopic compositions of OC from a selected set of seabed samples (Δ~(14)C_(OC) of -408 ± 82 per thousand) indicate OM in surface sediments is old (~(14)C ages of 2800 to over 6000 years before present). The ratios of organic carbon to mineral surface area exhibited by these sediments are within the typical (mono-layer equivalent) ranges characteristic of shelf sediments and do not reflect the preferential removal of terrigenous OM. Overall, these compositions indicate that while water-column POM appears to be derived mainly from terrigenous vascular plant debris and riverine/estuarine phytoplankton, the source of most of the sedimentary POM is aged, soil OC ultimately derived from C3 vegetation. We speculate that the concentrations and sources of suspended POM in the water column of the Fly River delta region reflect the conditions of low river discharge, low wave energy and neap tides encountered at the time of sampling. In contrast, POM compositions in surface sediments are consistent with the transport and deposition of old, mineral-bound OC most likely eroded from the upland regions of the Fly River watershed, which is characterized by steep slopes, high precipitation and C3 tropical forests and grasslands.
机译：在2003年1月的季风季节期间，在整个Fly河水下三角洲地区收集了地表和底水的悬浮颗粒以及海床的表层沉积物。由于厄尔尼诺现象强烈，河水流量极低，因此水柱盐度相对较高。在整个三角洲的大部分地区都很高（10至32），仅在弗莱河的主要分流河道中测得的盐度（<10）微咸。这些样品中颗粒有机物（POM）的浓度和组成显示出明显的空间差异，并且在水柱和海底样品之间存在明显的对比。总体而言，在表面和底部分别测量了相对较低的总悬浮固体（TSS），颗粒有机碳（POC）和颗粒氮（PN）浓度（分别为27±50、0.83±1.2和0.05±0.05 mg / L）。整个三角洲中的水（分别为400±743、7.1±7.3和1.7±7.2 mg / L）。地表水和底水中的颗粒均显示出较高的有机碳含量（％OC> 4 wt。％），相对较高的有机碳：氮摩尔比（OC：N> 20 mol：mol）和相当贫的稳定同位素组成的有机碳（ δ〜（13）C_（OC）<-27 /千）。相比之下，海床中的表层沉积物显示出空间上均一的成分，其特征在于％OC含量（1.1±0.8 wt。％）明显较低，OC：N比例较低（17±9 mol：mol）和相对富集的δ〜（13） C_（OC）组成（-25.5±1.1 /千）。一组选定海床样品中OC的放射性同位素组成（Δ〜（14）C_（OC）为-408±82 /千）表明表面沉积物中的OM很旧（〜（14）C年龄为2800至6000多年在此之前）。这些沉积物表现出的有机碳与矿物表面积之比在架子沉积物特征性的典型（单层当量）范围内，并不反映陆源性有机质的优先去除。总体而言，这些成分表明，虽然水柱POM似乎主要来自陆生维管植物碎片和河流/河口浮游植物，但大多数沉积POM的来源已老化，而土壤OC最终来源于C3植被。我们推测，飞河三角洲地区水柱中悬浮POM的浓度和来源反映了采样时遇到的低河流量，低波能和潮汐的情况。相反，地表沉积物中的POM组成与老的，矿物结合的OC的运输和沉积一致，最有可能从Fly River流域的高地地区侵蚀，其特征是陡峭的斜坡，高降水量和C3热带森林和草原。

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