Large inputs of groundwater and associated fluxes of alkalinity and nutrients into Jiaozhou Bay, China

• Published in: Hydrogeology journal Vol. 28; no. 5; pp. 1721 - 1734
• Main Authors: Zhang, Yan, Wang, Xuejing, Li, Hailong, Song, Dehai
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2020; Springer Nature B.V
• Subjects: Alkalinity; Aquatic Pollution; Coastal ecology; Coastal waters; Dry season; Earth and Environmental Science; Earth Sciences; Ecological effects; Fluxes; Geology; Geophysics/Geodesy; Groundwater; Groundwater discharge; Hydrogeology; Hydrology/Water Resources; Isotopes; Local precipitation; Mass balance; Mineral nutrients; Nitrogen; Nutrient sources; Nutrients; Phosphorus; Radium; Radium isotopes; Radon; Radon isotopes; Rainy season; Rivers; Seasonal variation; Seasonal variations; Seasons; Seepage; Silicates; Waste Water Technology; Water Management; Water Pollution Control; Water Quality/Water Pollution; Wet season; China; Jiaozhou Bay; Hydrochemistry; Radon; Submarine groundwater discharge; China; Radium
• ISSN: 1431-2174; 1435-0157
• DOI: 10.1007/s10040-020-02144-8

Submarine groundwater discharge (SGD) as a major source of alkalinity has rarely been studied in Jiaozhou Bay, China. The presented study used radon ( 222 Rn) and radium isotopes to investigate SGD and its influence on alkalinity and nutrient inputs into the bay. Time-series observations of 222 Rn were used to quantify groundwater dynamics over tidal time scales and the results showed that the SGD rates at point-scale were 0–67.2 (mean: 17.8) cm/day and 0–43.6 (mean: 12.3) cm/day in wet and dry seasons, respectively. Using radium mass balance models, the SGD in the whole bay was estimated to be (1.29–2.60) × 10 7  m 3 /day in wet season and (5.81–6.83) × 10 6  m 3 /day in dry season. Thus, both sets of results indicated higher SGD fluxes in wet season than in dry season. Such a seasonal variation pattern suggests a rapid response to local precipitation. The alkalinity fluxes associated with SGD were generally greater than those from the local rivers. Among the nutrient sources, SGD contributed about 63, 24 and 37% of total dissolved inorganic nitrogen, reactive phosphorus and silicate inputs, respectively. These results demonstrated that groundwater seepage is a major factor driving alkalinity and nutrients (especially dissolved inorganic nitrogen) into Jiaozhou Bay. SGD may have an important influence on the budgets of elements (C, N, P) and ecological environments in coastal waters.