Journal
ECOLOGICAL INDICATORS
Volume 145, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.ecolind.2022.109658
Keywords
Lacustrine groundwater discharge; Radon; Nutrients loads; Dongting Lake; Geological conditions
Categories
Funding
- National Natural Science Foundation of China
- Project of Hubei Provincial Key Research and Development
- National Key Research and Development Program of China
- [42177181]
- [U21A2026]
- [4201001051]
- [2020BCA088]
- [2021YFA0715900]
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This study quantifies the rates of lacustrine groundwater discharge (LGD) and associated nutrient loads in contrasting geological conditions in East Dongting Lake (EDL) and discusses the influence of geology on the spatial differences. The results show that geological conditions significantly affect LGD rates and associated nutrient loads in the lake area.
The spatial patterns of lacustrine groundwater discharge (LGD) and associated nutrient inputs are crucial for effective management and protection of lakes. Multiple factors have been found to influence the spatial differ-ences in LGD rates and associated nutrients loads, but the influence of geological conditions on the differences have not been well understood. In this study, we quantified LGD rates and associated nutrients loads on the west and east of the lake with contrasting geological conditions of East Dongting Lake (EDL) within central Yangtze catchment and discuss the influence of geology on the spatial differences, through 222Rn mass-balance model, water chemistry coupled with existing geological data. The results showed that LGD rates were 34.76 +/- 23.36 mm/d in the east EDL which is characterized by hilly geomorphy, deep/fast/narrow flowing, coarse-grained lakebed and large hydraulic gradients (0.004-0.006). Surprisingly, LGD rates were higher (71.47 +/- 52.16 mm/d) in the west EDL which is characterized by alluvial-lacustrine plain geomorphology, shallow/sluggish flowing, clayey or silty lakebed and low hydraulic gradients (0.0002-0.0015). The remaining factor determining the higher LGD rates in the west EDL is the permeability of the porous aquifer connected with the lake. The groundwater around the east EDL existed in a less confined environment, and frequent flushing led to low concentrations of nutrients. By contrast, rapid burial of sediments and deposition of paleo-lake sediments since Last Deglaciation formed an organic-rich and reducing environment, which facilitated the enrichment of geo-genic nutrients. As a result, the loads of LGD-derived nutrients in the west generally exceeded that in the east by one order of magnitude. The study provides new understanding of the spatial differences in LGD and associated nutrients input to the large lakes resulting from variations in geological conditions, thus serving as a reference for ecological protection of lakes.
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