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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2018-207
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
07 May 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).
Evaluation of flushing time, groundwater discharge and associated nutrient fluxes in Daya Bay, China
Yan Zhang1,2,3,*, Meng Zhang4,*, Hailong Li2,3,*, Xuejing Wang3, Wenjing Qu1,2, Xin Luo5,6, Kai Xiao1,2, and Xiaolang Zhang3 1MOE Key Laboratory of Groundwater Circulation and Environment Evolution and School of Water Resources and Environment, China University of Geosciences-Beijing, Beijing 100083, China
2State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences-Beijing, Beijing 100083, China
3School of Environmental Science and Engineering and Shenzhen Key Laboratory of Soil and Groundwater Pollution Control, Southern University of Science and Technology, Shenzhen 518055, China
4Zhong Di Bao Lian (Beijing) Land and Resource Exploration Technology Co., Ltd, Beijing 100193, China
5Department of Earth Sciences, The University of Hong Kong, Hong Kong, China
6Shenzhen Research Institude, The University of Hong Kong, Shenzhen, China
*These authors contributed equally to this work.
Abstract. Radium quartet have been widely used to quantify the flushing time of water body and submarine groundwater discharge (SGD) in coastal zones. However, previous apparent age model based on mass balance of radium isotopes usually neglected the effects of rivers, open sea water end-member, sedimentary input, atmospheric deposits and recirculated seawater (RSGD). To enhance accuracy in estimating flushing time and SGD, here we present an improved model and then apply in Daya Bay, China. The flushing time estimated by the improved model is 11.8–27.7 d in Daya Bay. It is found that the previous model overestimated the flushing time by 10.7 %–103 %. Considering the radium losses caused by RSGD, the SGD flux is estimated to be (3.87–5.09) × 107 m3 d−1 based on the derived flushing time. The SGD associated nutrient fluxes are estimated to be (1.36–1.76) × 106 mol d−1 and (2.53–3.26) × 104 mol d−1 for DIN and DIP, respectively, about 20 times greater than those from local rivers. The primary production supported by all the external DIN inputs is determined to be 323–390 mg C m−2 d−1, in which SGD provide approximately 73.1 % of total primary production. Our results reveals that SGD plays an important role in nutrient balance and may be responsible for the frequent outburst of red tides in Daya Bay. The present study provides baseline data for evaluating environmental effects in Daya Bay and similar coastal bay systems elsewhere.
Citation: Zhang, Y., Zhang, M., Li, H., Wang, X., Qu, W., Luo, X., Xiao, K., and Zhang, X.: Evaluation of flushing time, groundwater discharge and associated nutrient fluxes in Daya Bay, China, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2018-207, in review, 2018.
Yan Zhang et al.
Yan Zhang et al.

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Short summary
Previous apparent age model usually neglects the effects of the key factors and results in the uncertainty of flushing time estimation for coastal waters. To enhance the accuracy of flushing time and submarine groundwater discharge (SGD), we present an improved model and then apply in Daya Bay, China. The nutrient inputs from SGD are compared with those from the local rivers and other external sources. The analysis indicates that SGD has an important influence on the ecological environment.
Previous apparent age model usually neglects the effects of the key factors and results in the...
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