Spatial and temporal analysis of stable isotopes in tap water across China

Abstract:

Stable isotopes in water (δ²H and δ¹⁸O) are important indicators of hydrological and ecological pattern and process. Water isotopes have been used to trace atmospheric moisture source, identify source of groundwater and surface water charge, reconstruct paleoclimate, and so on. Tap water appears to reflect pervasive features of regional integrated hydrological process. China is a large-size country with high variations in both environmental and geographical factors including temperature, precipitation amount, relative humidity, latitude, altitude et al. Here we present a first national-scale survey on stable isotope of tap water across China. More than 1000 tap water samples have been collected from 93 cities across China by monthly between December 2014 and November 2015. Stable isotope composition of tap water ranged from -132.1‰ to -25.6‰ (δ²H) and from -17.5‰ to -4.2‰ (δ¹⁸O). The Meteoric Water Line is δ²H = 7.77 δ¹⁸O + 5.79 (r² = 0.95) and the LMWL of Chinese precipitation is δ²H =7.6δ¹⁸O+ 9.94 (r²= 0.97). Spatial distribution of stable isotopes present typical “continental effect”, isotope values generally decrease from coastal regions to inland. Isotopes in different regions present different correlations with temperature, precipitation amount, latitude and altitude as a result of varied moisture source and local water supply. The results of the study could provide mapping information of tap water for fundamental isotope hydrological studies in different regions of China.