کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5770877 | 1629903 | 2017 | 9 صفحه PDF | دانلود رایگان |
- Magnitude of submarine groundwater discharge (SGD) in Daya Bay was estimated using radon tracing.
- Multiple radon time series for both seawater and groundwater produced more accurate estimation.
- SGD-driven dissolved nitrates, inorganic phosphorous, and reactive silicate were elevated.
- Both water and nutrient fluxes are comparable to or even higher than those supplied by local rivers.
Daya Bay, a semi-closed bay of the South China Sea, is famous for its aquaculture, agriculture and tourism. Although routine environmental investigations in the bay have been conducted since the early 1980s, evaluations of submarine groundwater discharge (SGD), an important process in exchange between groundwater and coastal seawater, and its environmental impacts have never been reported. In this study, naturally occurring radon isotope (222Rn) was measured continuously at two sites (north-west and middle-east sites) and used as a tracer to estimate SGD and associated nutrient inputs into the bay. The SGD rates estimated based on the 222Rn mass balance model were, on average, 28.2Â cm/d at north-west site and 30.9Â cm/d at middle-east site. The large SGD rate at middle-east site may be due to the large tidal amplitude and the sandy component with high permeability in sediments. The SGD-driven nutrient fluxes, which were calculated as the product of SGD flux and the difference of nutrient concentrations between coastal groundwater and seawater, were 3.28Â ÃÂ 105Â mol/d for dissolved nitrates (NO3-N), 5.84Â ÃÂ 103Â mol/d for dissolved inorganic phosphorous (DIP), and 8.97Â ÃÂ 105Â mol/d for reactive silicate (Si). These nutrient inputs are comparable to or even higher than those supplied by local rivers. In addition, these SGD-driven nutrients have a nitrogen-phosphorous ratio as high as â¼43, which may significantly affect the ecology of coastal waters and lead to frequent occurrence of harmful algal blooms.
Journal: Journal of Hydrology - Volume 551, August 2017, Pages 784-792