Hypoxia off the Changjiang (Yangtze River) Estuary: Oxygen depletion and organic matter decomposition
Hypoxia off the Changjiang (Yangtze River) Estuary: Oxygen depletion and organic matter decomposition
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DOI：
10.1016/j.marchem.2011.03.005
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发表时间：
2011-07
期刊：
影响因子：
3
通讯作者：
Zhuoyi Zhu;Jing Zhang;Ying Wu;Ying-ying Zhang;Jing Lin;Sumei Liu
中科院分区：
文献类型：
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作者：
Zhuoyi Zhu;Jing Zhang;Ying Wu;Ying-ying Zhang;Jing Lin;Sumei Liu
在2006年长江口特别干旱的年份，于6月至10月进行了3个航次的调查，研究了长江口海域的耗氧过程。从1959年到2006年的缺氧区数据表明，近年来缺氧区的面积急剧增加，缺氧中心在2006年向北移动。8月，北方地区的缺氧面积（溶解氧，或DO，<62. 5 μM）为15，400平方公里，与墨西哥湾相当。南部海域也出现了大面积的低DO（62.5 μM < DO < 94 μM）。近底层沃茨中颗粒有机碳（POC）、溶解无机磷（DIP）、溶解无机氮（DIN）和表观耗氧量（AOU）呈现耦合变化。例如，AOU与POC/营养物之间存在关系（POC/DIP：r =-0.47，POC/DIN：r =-0.50; p < 0.001，n = 86），AOU与水柱的Δσ之间存在关系（r = 0.66，p < 0.001，n = 86; Δσ =近底沃茨密度-表层沃茨密度）。有趣的是，北方和南方地区的氧气消耗是分开发展的，并且它们表现出明显的差异。南部地区的氧耗较轻，且相对较长，而北方地区的氧耗较明显，且较短。AOU与无机营养盐之间的不同关系，表明南、北方地区的耗氧机制不同。这可能是由于1）溶解的有机营养物作为除无机形式之外的另一种分解产物的影响，2）和/或在近底层沃茨中分解的有机物质的不同化学组成。
In an especially dry year (2006) in the Changjiang Estuary, three cruises were conducted between June and October, to study the process of oxygen depletion. Data for the hypoxic zone pooled for 1959 through 2006 suggest that a dramatic increase in the area of hypoxia has occurred in recent years, and that the center of hypoxia moved northwards in 2006. In August, the hypoxic area (dissolved oxygen, or DO, < 62.5 μM) in the northern region was 15,400 km2, which is comparable to that in the Gulf of Mexico. A large area of low DO (62.5 μM < DO < 94 μM) also was found in the southern region. In near-bottom waters, particulate organic carbon (POC), dissolved inorganic phosphorus (DIP), dissolved inorganic nitrogen (DIN) and apparent oxygen utilization (AOU) showed coupled variation. For example, relationships can be found between AOU and POC/nutrients (POC/DIP: r = −0.47, POC/DIN: r = −0.50; p < 0.001, n = 86), and between AOU and Δσ of the water column (r = 0.66, p < 0.001, n = 86; Δσ = densitynear-bottom waters− densitysurface waters). It is interesting that oxygen depletion in the northern and southern regions developed separately, and they showed distinct differences. Oxygen depletion in the southern region is milder and relatively long lived, whereas in the northern region it is more pronounced and short lived. The different relationships between AOU and inorganic nutrients, indicates different mechanisms for the occurrence of oxygen depletion between the southern and northern regions, respectively. This can be due to 1) the influence of dissolved organic nutrients as another decomposition product besides inorganic forms, 2) and/or different chemical composition of organic matter that decomposed in the near-bottom waters.