Geochemical and isotopic evidence of shallow groundwater salinization in a reclaimed coastal zone: the Yellow River Delta, China

Abstract

This paper aims to improve the current knowledge of groundwater salinization processes of a young coastal aquifer in the Yellow River Delta (YRD) and to assess the impact of both the transfer of irrigation water from the Yellow River and seawater intrusion, using a combination of hydrochemical-isotopic measurements. The major ion/Cl -ratios generally closely follow the mixing line between freshwater end-member (the Yellow River) and saline water end-members (salt groundwater or seawater), indicating the importance of mixing under natural and anthropogenic influences. The examination of stable isotope in groundwater (ranging from -9.0 to -3.5 % for d18 O and from -73 to -29 % for dD, respectively) and chloride concentrations (*2 to 629 meq/ L) confirms that the saline end-member is associated with saltwater rather than present seawater, and most groundwater samples are plotted on mixing lines between the Yellow River and saltwater. The similar range in stable isotopes (d 18 O and dD) and Cl -compositions between saltwater and confined aquifer supports the hypothesis that upward seepage of confined saline water intruded the shallow aquifer. Moreover, the deviations in some cases from mixing line imply water-rock interaction is also important in dominant control on groundwater chemistry, such as cation exchange, SO 4 2-reduction, and NaCl solution. The brackish water was characterized by slight excess of Na ? and deficit of Ca 2? compared to nonreactive mixing line. This indicates that the coastal aquifer is generally freshening with respect to extensive irrigation network, as well as the transfer from the Yellow River for ecological recharge into wetland.

Advancements in water and ecological risk assessment in the Yellow River Delta, North China: Implications for legal frameworks in environmental protection and public health

“…In the YRD, agricultural water accounts for a large proportion, and the large-scale development of the Yellow River and groundwater makes the water resources situation extremely severe. The fragile coastal wetland ecosystem and concentrated industrial and agricultural activities make the ecological environment in this region face serious threats (An et al, 2011;Liu et al, 2016) The YRD of China has received considerable attention due to its unique geographical location and delicate ecosystem, which render it particularly susceptible to water eco-environmental problems and require water resource protection measures. Over the past few decades, numerous studies have been conducted on the hydrological cycle mechanisms, water resource utilization, water environmental pollution and ecosystem evolution in the YRD (Xie et al, 2015;Zhi et al, 2021).…”

“…In the YRD, agricultural water accounts for a large proportion, and the large‐scale development of the Yellow River and groundwater makes the water resources situation extremely severe. The fragile coastal wetland ecosystem and concentrated industrial and agricultural activities make the ecological environment in this region face serious threats (An et al, 2011; Liu et al, 2016). Recent studies highlight the significance of public health in the YRD, demonstrating the profound impact of degraded water quality on the well‐being of the local population.…”