基于Cl^-和氢氧稳定同位素的敦煌盆地地下水演化与补给

Groundwater recharge and geochemical evolution of Dunhuang Basin based on Cl-, δ(18O) and δ（D）

应用Cl-和氢氧稳定同位素示踪剂研究了敦煌盆地第四系含水层的地下水演化与补给过程.结果表明绝大多数地下水样品中c(Na+)/c(Cl-)>1,碳酸盐的平衡反应和反硝化作用使地下水中ρ(HCO3-)和ρ(NO3-)较低.一般情况下地下水中Mg2+的来源与Ca2+相似,但由于含镁岩如白云岩、菱镁矿在水中的溶解性大于含钙盐,因此ρ(Mg2+)高于ρ(Ca2+).芒硝的溶解对Na+和SO42-有重要的贡献.敦煌盆地地下水氢氧同位素沿当地大气降水线分布,反映了敦煌盆地第四系地下水起源于大气降水.南湖地下水主要接受党河上游冰雪融水的补给,敦煌浅层地下水广泛接受河流侧渗补给,反映了现代地表水补给的特点.敦煌深层地下水同位素值很低,可能是由于过去较冷时期的古水补给.

The groundwater recharge and geochemical evolution of Quaternary aquifers of the Dunhuang Basin were studied using Cl-and stable isotopes and the results showed that c(Na+)/c(Cl-)>1 in most groundwater samples,carbonate equilibrium reaction and denitrification madeρ(HCO3-)andρ(NO3-)concentrations lower in groundwater.Under normal circumstances,the source of Mg2+in groundwater is similar to that of Ca2+.Theρ(Mg2+)in groundwater was higher thanρ(Ca2+)because of its solubility in water was higher than that of calcium salts.Glauber’s dissolution had an important contribution to Na+and SO42-.The hydrogen and oxygen isotopes of the groundwater in the Dunhuang Basin were distributed along the local meteoric water line,thus reflecting that the Quaternary groundwater in the Dunhuang Basin had originated from atmospheric precipitation.The groundwater in South Lake mainly received a supply of ice and snowmelt water from the upstream of the Danghe River.The shallow groundwater in Dunhuang was widely accepted by the lateral seepage replenishment of river,reflecting the characteristics of the modern surface water recharge.Dunhuang deep groundwater isotope values werevery low,probably due to the ancient water recharge of a colder period.