Fig. 3 Daily variations in precipitation, air temperature,
evaporation, and humidity in the plot from
May 2018 to Jun 2019. The shaded area indicates the rainy season.
3.2 δ18O
and δ2H isotope composition of precipitation in Wuhan
As a direct source of soil water in the test area, precipitation
dramatically affects the soil water content. Moreover, the change in the
precipitation reflects the shift in air environmental factors
(temperature and humidity), which is vital for calculating the isotope
composition enrichment limit. Herein, it was used as the basis for
analyzing the δ18O and δ2H isotopes
in soil water at the test site.
As shown in Table 1, the maximum values of δ18O and
δ2H in the local precipitation isotopes continue to
increase, whereas the minimum values initially increase and subsequently
decrease. The overall average value exhibits an increasing trend. The
concentration of the majority of the precipitation isotope samples was
negative, and there were only five positive values. The reason for the
occurrence of these five positive values may have been that the water
vapor of these samples had different sources or experienced intense
secondary evaporation during their decrease, thus resulting in the
enrichment of heavy isotopes and a lack of light isotopes.