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    Characteristics of dissolved oxygen and pH variations in summer off the Qinhuangdao
    投稿時間:2019-11-29  修訂日期:2020-05-02
    中文關鍵詞:  秦皇島外海  低氧  酸化  耗氧速率
    英文關鍵詞:the sea off Qinghuangdao  hypoxia  acidification  oxygen consumption rate
    趙紫涵 天津科技大學 海洋與環境學院,天津 300457  
    宋貴生 天津大學 海洋科學與技術學院,天津 300072  
    趙亮 天津科技大學 海洋與環境學院,天津 300457 zhaoliang@tust.edu.cn 
    摘要點擊次數: 1238
    全文下載次數: 4347
          溶解氧(DO)是海洋生物生存不可缺少的要素。隨著人類活動的增加,全球近岸海域低氧情況愈發嚴重,已經成為威脅海洋生態系統健康的重要因素。通過對2017年5-9月秦皇島外海區域的觀測調查,探討了該海域低氧與酸化的形成機制并計算了月平均耗氧速率。結果表明,5月秦皇島外海水體混合較為均勻,表、底層DO濃度一致,均大于8 mg/L;6月開始形成密度躍層,與此同時底層DO濃度和pH開始下降;8月底層呈現明顯的低氧和酸化狀態,DO濃度下降至2~3 mg/L,pH下降至7.8以下;9月隨著層化消失,底層水體DO濃度和pH逐漸升高。相關性分析顯示,DO和葉綠素a (Chl a)以及pH具有良好的耦合性,說明秦皇島外海區域的低氧發生過程主要為局地變化。同時表明DO濃度和pH主要受水體中浮游植物的光合作用和有機物有氧分解的影響。通過箱式模型計算得到2017年6-8月密度躍層以下水體及沉積物耗氧速率為951~1193 mg/(m2·d)[平均為975 mg/(m2·d)]。綜合來看,水體分層是秦皇島外海低氧和酸化發生的先決條件,躍層以下的有機物分解耗氧則是底層水體發生低氧和酸化的重要原因。
          Dissolved oxygen is an indispensable element for the survival of marine organisms. With the increase of human activities, the situation of hypoxia in the global coastal waters has become exacerbated, which is considered as an important factor threatening the health of the marine ecosystem. The vertical distributions of water temperature, salinity and density were investigated in the offshore area of Qinhuangdao from May to September in 2017. Additionally, the average monthly oxygen consumption rate was evaluated, and hence the mechanism of hypoxia and acidification was discussed. The results showed that the water column in the studied area was vertically homogenous in May, and no obvious difference for dissolved oxygen (DO) between the surface and bottom layers, with the value larger than 8 mg/L. From June to August, the pycnocline presented in the mid of the water column. In this period, DO and pH in bottom water gradually decreased, and reached 2-3 mg/L for DO and less than 7.8 for pH in the end of August, suggesting significant hypoxia and acidification in this area. However, DO and pH in bottom water sharply increased in September, after the pycnocline disappeared. The result indicated that hypoxia and acidification of Qinhuangdao offshore waters are seasonal. DO was significantly correlated with chlorophyll a and pH, indicating that the hypoxic and acidified processes in the offshore area of Qinhuangdao were local. The evaluated oxygen consumption rate, based on the box model, in bottom water and sediment ranged from 951 mg/(m2·d) to 1193 mg/(m2·d) (mean: 975 mg/(m2·d)) from June to August in 2017. Comprehensive analysis showed that water stratification was the prerequisite for the occurrence of hypoxia and acidification in Qinhuangdao offshore waters, and DO consumption caused by organic matter decomposition was an important reason of hypoxia and acidification in bottom water.
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