Abstract
Stable isotopes (e.g., δ2H and δ18O) in tap water are important tools to understand the local climate or environment background, water sources and the state of regional water supply. Based on 242 tap water samples, 35 precipitation samples and 24 surface water samples gathered in the urban area of Lanzhou, the basic spatiotemporal characteristics of isotopes in tap water, their connection with isotopes in other water bodies and change during the process from raw water to tap water are discussed in detail, combining the information of local tap water supply and water source. It can provide reliable help for understanding the isotope characteristics of local tap water, regional water supply management and determination of tap water source of in a small area. Except for the establishment of a new data set of isotopes in tap water with complete time series and uniform spatial distribution of sampling sites, other results show that: (1) The Local Tap Water Line (LTWL) of Lanzhou is δ2H = (6.03 ± 0.57) δ18O + (−8.63 ± 5.44) (r2 = 0.41, p < 0.01). (2) For seasonal variations, δ2H and δ18O in tap water both are higher in autumn and lower in spring. The diurnal and daily variations of isotopes in tap water are not large. As for spatial variations, the monthly mean values of δ2H and δ18O in tap water at each sampling site show little difference. The isotopes in tap water collected from one single sampling site can be considered as a representative for isotopes in tap water in the area with a single tap water source. (3) Isotopes in tap water show weak connection with precipitation isotopes, but exhibit good connection (consistent seasonal variation, similar numerical range, small numerical difference and high correlation) with isotopes in surface water, which is the direct water source. Isotopes in water change little from raw water to tap water. Isotopic composition of tap water in Lanzhou can be used as a representative of isotopes in surface water.
Highlights
The isotopes in tap water collected from one single sampling site can be considered as a representative for isotopes in tap water in the area with a single tap water source
Stable isotopes (δ2 H and δ18 O) in 242 tap water samples gathered at 7 sampling sites, 35 precipitation samples and 24 surface water samples collected in the urban area of Lanzhou were discussed around these issues
A new urban tap water isotope composition dataset with complete time series and uniform spatial distribution of sampling sites was established in this study
Summary
Stable isotopes in water (e.g., δ2 H and δ18 O) are significant indicators of hydrological processes and ecological patterns [1,2,3,4,5], and they have been widely used as tracers in climatology, hydrology, ecology and forensic studies [6,7,8], e.g., tracking atmospheric sources [9,10], tracing water source of plants [11,12,13], identifying the origin of forensic samples [14,15,16] and so on [17,18]. Stable isotopes (e.g., δ2 H and δ18 O) in tap water come to be important tools to understand the climate and environment characteristics in local area and water resources, monitor complex hydrological systems impacted by human activities, and reflect the state of regional water supply [24,43,44]. It is necessary to establish a data set of isotopes in tap water with a complete time series and uniform spatial distribution of sampling sites, in order to analyze these problems Studying these problems and combining the information of local tap water supply or water source can provide reliable help for understanding the isotope characteristics of local tap water, regional water supply management and determination of tap water source in a small area. Stable isotopes (δ2 H and δ18 O) in 242 tap water samples gathered at 7 sampling sites, 35 precipitation samples and 24 surface water samples collected in the urban area of Lanzhou were discussed around these issues
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