Impacts of fluvial flood on physical and biogeochemical environments in estuary-shelf continuum in the East China Sea
Impacts of fluvial flood on physical and biogeochemical environments in estuary-shelf continuum in the East China Sea
复制标题
河流洪水对东海河口陆架连续体物理和生物地球化学环境的影响
DOI：
10.1016/j.jhydrol.2021.126441
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发表时间：
2021
影响因子：
6.4
通讯作者：
Ding Pingxing
中科院分区：
文献类型：
--
作者：
Ge Jianzhong;Zhang Jingsi;Chen Changsheng;Ding Pingxing
陆地-海洋相互作用对沿海和陆架地区陆地物质的运输命运起着至关重要的作用。巨型河流的洪水排放包含大量的水、泥沙和营养物质，可能会对海岸系统的物理和生物地球化学动态造成重大而复杂的影响。在这项研究中，在从长江口到东中国海(ECS)的一个地区进行了一次大洪水前后的现场调查。评价了洪水对自然环境和生物地球化学环境的影响。结果表明，河流洪水促进了低盐度河流羽流及其沉积物/营养物质锋面的近岸扩张。然而，河口的叶绿素a升高的面积并没有明显扩大。应用数值模型研究了三峡大坝对河口陆架连续体洪水作用的空间强度和时间持续时间的贡献。结果预测陆架水的最大纬向离岸位移为2°。盐度和硝酸盐表现出保守的膨胀，其松弛时间(~2个月)长于叶绿素a和磷酸盐。在TGD调节的水流事件停止后，盐度和硝酸盐的影响仍然存在，但磷酸盐和叶绿素a迅速恢复。洪水降低了河口和近岸海域的溶解氧浓度，但对近岸过渡区的溶解氧浓度影响不大。相反，非TGD调节增加了局部DO浓度，从而降低了缺氧风险。TGD已成为长江口-ECS连续体环境变化的重要人为驱动因素。
Land-ocean interaction plays an essential role in the transport fate of terrestrial matters in the coastal and shelf regions. Flood discharge from a mega river, containing massive water, sediment, and nutrient loads, could result in substantial and complex impacts on the physical and biogeochemical dynamics of coastal systems. In this study, field campaigns were conducted in a region from the Changjiang River Estuary to the East China Sea (ECS) before and after a significant flood. The impacts of the flood on physical and biogeochemical environments were assessed. The results revealed that the fluvial flood enhanced the offshore expansion of the low-salinity river plume and associated sediment/nutrient fronts. However, the area of elevated chlorophyll-a at the river mouth did not expand noticeably. A numerical model was applied to quantify the contribution of the Three Gorges Dam (TGD) to the spatial intensity and temporal duration of fluvial flood effects on estuary–shelf continuum. The results predicted a maximum of 2° latitudinal offshore displacement of the shelf water. Salinity and nitrate exhibited conservative expansions, with a longer relaxation time (~2 months) than chlorophyll-a and phosphate. After the TGD-regulated flow event ceased, salinity and nitrate effects persisted, but phosphate and chlorophyll-a recovered rapidly. The flood decreased the dissolved oxygen (DO) concentration around the river mouth and the offshore region, but not in the nearshore transient area. In contrast, the non-TGD regulation increased the regional DO concentration, which reduced the hypoxia risk. The TGD has become a crucial anthropogenic driver of environmental changes in the Changjiang Estuary-ECS continuum.