Reveal the threat of water quality risks in Yellow River Delta based on evidences from isotopic and hydrochemical analyses

This study aims to evaluate the seasonal and spatial characteristics of hydrochemistry and D-O isotopes and identify the eco-environmental threats under the background of saline intrusion and human activities in Yellow River Delta (YRD). Analyses for major ions (i.e., K+, Na+, Ca2+, Mg2+, SO42- , HCO3- and Cl-), nitrate ion (NO3- ) and isotopic composition are performed for precipitation, river water, wetland water and sea water. Based on the range of 82H and 818O as well as their relations, the mixing between multiple sources and evaporation are confirmed. Electrical conductivity (EC), concentration of NO3-, soluble sodium percentage (SSP) and magnesium hazard (MH) are employed as indicators to reflect the ecological risks from salinity, agricultural pollutants, sodium and magnesium. By hierarchical cluster analysis (HCA), the samples of wetland water are grouped associated with those of river water. The characteristic reflects 3 patterns of risks in wetlands, including saline intrusion, human activities and their mixed influence.

Automated summary

This study evaluates the seasonal and spatial characteristics of hydrochemistry and D-O isotopes in the Yellow River Delta, and identifies the eco-environmental threats caused by saline intrusion and human activities. The analysis of major ions, nitrate ions, and isotopic composition confirms the mixing between multiple sources and evaporation. Various indicators, such as electrical conductivity, concentration of nitrate, soluble sodium percentage, and magnesium hazard, are used to assess ecological risks. Hierarchical cluster analysis reveals three patterns of risks in the wetlands, including saline intrusion, human activities, and their combined influence.