Evolutionary process of saline groundwater influenced by palaeo-seawater trapped in coastal deltas: A case study in Luanhe River Delta, China

Dang, Xianzhang; Gao, Maosheng; Wen, Zhang; Jakada, Hamza; Hou, Guohua; Liu, Sen

doi:10.1016/j.ecss.2020.106894

Cited by 10 publications

(5 citation statements)

References 42 publications

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“…1b). The first Holocene aquifer (Q 4 ) is a phreatic or semiconfined aquifer with a bottom depth of 15-30 m, is primarily composed of fine sand and slit, and involves fresh, brackish, saline, and brine groundwater (Dang et al, 2020). The second Late Pleistocene aquifer (Q 3 ), the third Middle Pleistocene aquifer (Q 2 ), and the fourth Early Pleistocene aquifer (Q 1 ) have bottom depths of 120-170, 250-350, and 350-550 m, respectively.…”

Section: Hydrogeologymentioning

confidence: 99%

“…Groundwater is an important freshwater resource for domestic consumption and agricultural activities in this region (Cary et al, 2015;Jayathunga et al, 2020). However, groundwater salinization poses a significant threat to everyday living and development activities (Tulipano, 2005;de Montety et al, 2008). In recent decades, groundwater salinization in coastal zones has prompted widespread concern and has been widely studied.…”

Section: Introductionmentioning

confidence: 99%

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Saline groundwater evolution in the Luanhe River delta (China) during the Holocene: hydrochemical, isotopic, and sedimentary evidence

Dang

Gao

Wen

et al. 2022

Hydrol. Earth Syst. Sci.

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Abstract. Since the Quaternary Period, paleo-seawater intrusions have been suggested to explain the observed saline groundwater that extends far inland in coastal zones. The Luanhe River delta (northwest coast of the Bohai Sea, China) is characterized by the distribution of saline, brine, brackish, and fresh groundwater from the coastline inland. The groundwater in this region exhibits a wide range of total dissolved solids (TDS): 0.38–125.9 g L−1. Meanwhile, previous studies have revealed that this area was significantly affected by Holocene marine transgression. This study used hydrochemical, isotopic, and sedimentological methods to investigate groundwater salinization processes in the Luanhe River delta and its links to paleo-environmental settings. Isotopic results (2H, 18O, 14C) allowed old groundwater recharge to be distinguished from new groundwater recharge. Hydrochemical analysis using the PHREEQC code indicated that the salt in saline and brine groundwater originates from a marine source. The 18O–Cl relationship diagram yields three-end-member groundwater mixing, and two mixing scenarios are suggested to explain the freshening and salinization processes in the study area. When this was interpreted along with data from paleo-environmental sediments, we found that groundwater salinization may have occurred since the Holocene marine transgression. The brine is characterized by radiocarbon activities of ∼ 50–85 pMC and relatively depleted stable isotopes, which are associated with seawater evaporation in the ancient lagoon during delta progradation and mixing with deeper fresh groundwater, which was probably recharged in the cold Late Pleistocene. The brackish and fresh groundwaters are characterized by river-like stable isotope values, where high radiocarbon activities (74.3–105.9 pMC) were formed after the washing out of the salinized aquifer by surface water in the delta plain. This study presents an approach that utilizes geochemical indicator analysis with paleo-geographic reconstruction to better assess groundwater evolutionary patterns in coastal aquifers.

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Section: Hydrogeologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Saline groundwater evolution in the Luanhe River delta (China) during the Holocene: hydrochemical, isotopic, and sedimentary evidence

Dang

Gao

Wen

et al. 2022

Hydrol. Earth Syst. Sci.

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“…The brackish and low TDS saline groundwater with modern age (e.g. G08-15, G09-15), and rapid increase in Electric Conductivity profile (Dang et al, 2020), are compelling evidence that freshening processes have occurred in the delta plain, as shown by the δ 18 O-Clrelationship diagram (Fig. 9).…”

Section: Interpretation Of Palaeo-environmental Developmentmentioning

confidence: 98%

Saline groundwater evolution in Luanhe River Delta, China since Holocene: hydrochemical, isotopic and sedimentary evidence

Dang

Gao

Wen

et al. 2021

Preprint

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Abstract. Since the Quaternary Period, palaeo-seawater intrusions have been suggested to explain the observed saline groundwater that extends far inland in coastal zones. The Luanhe River Delta (northwest coast of Bohai Sea, China) is characterized by the distribution of saline, brine, brackish and fresh groundwater, from coastline to inland, with a wide range of total dissolved solids (TDS) between 0.38–125.9 g L−1. Meanwhile, previous studies have revealed that this area was significantly affected by Holocene marine transgression. In this study, we used hydrochemical, isotopic, and sedimentological methods to investigate groundwater salinization processes in the Luanhe River Delta and its links to the palaeo-environmental settings. The isotopic results (2H, 18O, 14C) show that deep confined groundwater was recharged during the Late Pleistocene cold period, shallow saline and brine groundwater was recharged during the warm Holocene period, and shallow brackish and fresh groundwater was mainly recharged by surface water. The results of hydro-geochemical modeling (PHREEQC) suggest that the salty sources of salinization are seawater and concentrated saline water (formed after evaporation of seawater). The 18O–Cl relationship diagram shows that saline and brine groundwater are formed by three end-member mixings (seawater, concentrated saline water and, fresh groundwater). In contrast, brackish groundwater is formed after the wash-out of saline groundwater by surface water. Using palaeo-environmental data from sediments, we found that palaeo-seawater intrusion during the Holocene marine transgression was the primary cause of groundwater salinization in the study region. Seawater was found to evaporate in the lagoon area during the progradation of the Luanhe River Delta; the resulting concentrated saline water infiltrated into the aquifer, eventually forming brine groundwater due to salinity accumulation. Surface water recharge and irrigation, on the other side, would gradually flush the delta plain's saline groundwater. This study provides a better understanding of saline groundwater evolution in other similar coastal zones.

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“…Most of the freshwater and brackish water isotopic compositions are similar to those of river water, indicating groundwater is closely linked to surface rivers. The freshwater with stable isotopic compositions that plot at the bottom left of Figure 6 may be related to groundwater recharge under cold conditions during the late Pleistocene (Han D. et al, 2011;Han F. et al, 2011;Li et al, 2017;Dang et al, 2020).…”

Section: Isotopesmentioning

confidence: 99%

Hydrogeochemical characteristic and recognization of saline groundwater formation and evolution in silty coast of the Yellow Sea and Bohai Sea, Eastern China

et al. 2023

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Saline groundwater is a valuable unconventional water resource in silty coastal zone, which contain complex and fragile sedimentary and hydrological environments that are widely distributed and vulnerable to human activities. Coastal groundwater salinization along the eastern coast of China since the late Pleistocene is thought to be a response to global environmental change. Previous studies have shown a spatial and temporal link between the development of saline groundwater and deposition of marine strata. However, groundwater salinization is becoming an increasing problem in coastal zone, and the hydrogeochemical characteristics and cause of the groundwater salinization or desalinization remain poorly understood. In this study, we compared the hydrogeochemical characteristics and relationships between saline groundwater and the sedimentary environment in two representative, muddy coastal zone of the Yellow Sea coast (YSC) and Bohai Sea coast (BSC). Our monitoring results show that the groundwater varies from fresh water, to brackish water, saltwater, and brine moving offshore of the BSC, with total dissolved solid (TDS) concentrations of 203–184,196 mg/L. In contrast, brine is absent from the YSC, where the TDS concentrations range from 280 to 41,690 mg/L. The relationships between δ2H and δ18O values indicate that freshwater–seawater–brine and freshwater–seawater mixing are the main processes leading to enrichment in TDS in the BSC and YSC, respectively. Based on the relationship between the major cations, Cl−, and Cl/Br ratios, the results show that the groundwater salinity is primarily due to saltwater intrusion and secondly to water–rock interactions (i.e., evaporitic salt dissolution and cation exchange). The regression curves on plots of Na–Cl and (Ca+Mg)–(CO3+SO4) have negative slopes (−0.33 and −0.34, respectively) for the groundwater samples from the BSC and YSC, indicating the Na in groundwater exchange for Ca due to seawater or residual seawater intrusion. The saline groundwater (or brine) samples with reverse ion exchange indicate that seawater or residual seawater has invaded the aquifer, and in which Na+ is replacing Ca2+ and Mg2+. These results enhance our understanding of the formation and evolution of saline groundwater, and provide insights into groundwaters in other silty coastal zones.

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Evolutionary process of saline groundwater influenced by palaeo-seawater trapped in coastal deltas: A case study in Luanhe River Delta, China

Cited by 10 publications

References 42 publications

Saline groundwater evolution in the Luanhe River delta (China) during the Holocene: hydrochemical, isotopic, and sedimentary evidence

Saline groundwater evolution in the Luanhe River delta (China) during the Holocene: hydrochemical, isotopic, and sedimentary evidence

Saline groundwater evolution in Luanhe River Delta, China since Holocene: hydrochemical, isotopic and sedimentary evidence

Hydrogeochemical characteristic and recognization of saline groundwater formation and evolution in silty coast of the Yellow Sea and Bohai Sea, Eastern China

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