南太行山山前平原地下水水化学以及同位素组成研究

Hydro-chemical and Isotopic Compositions of Groundwater in Piedmont Plain of the South Taihang Mountain

采用环境同位素和水化学方法,通过分析南太行山山前平原不同类型水体氢氧稳定同位素(δD和δ18O)、溶解性无机碳同位素(δ^(13)C-DIC)和水化学组成特征,探讨不同水体来源以及人类活动对地下水水质的影响过程。研究区地下水氢氧同位素组成表明,区内地下水均来自大气降水,补给区和排泄区浅部含水层地下水较深部含水层地下水氢、氧同位素值均偏正,氘盈余值(d值)也偏小,显示浅部含水层地下水受蒸发作用影响。同时排泄区地下水氢、氧同位素值较补给区地下水偏正,显示排泄区地下水经历较明显的蒸发过程。研究区地下水溶解性无机碳碳同位素(δ^(13)C-DIC)组成表明,补给区和排泄区浅部含水层地下水δ^(13)C-DIC值较深部含水层δ^(13)C-DIC值均偏负,显示浅部含水层地下水无机碳更多来源于有机物分解。同时排泄区地下水δ^(13)C-DIC值较补给区地下水δ^(13)C-DIC值偏负,表明排泄区地下水溶解性无机碳受有机物分解影响较大。研究区地下水水化学组成表明,补给区地下水水化学类型以Ca-HCO3型为主,排泄区地下水水化学类型以Na-HCO3-SO4型为主。结合同位素组成特征,补给区地下水水化学组成主要受溶滤作用和人类活动的影响,排泄区地下水水化学组成则受溶滤作用、蒸发浓缩作用、阳离子交换作用和人类活动的共同控制。

Characteristics of hydrogen, oxygen and dissolved inorganic carbon isotopes and hydro-chemical compositions of different water bodies in piedmont plain of the South Taihang Mountain were illustrated by using environmental isotopes and hydro-chemical technologies, to determine sources of different water bodies and effect of human activities on groundwater quantity. The composition of hydrogen and oxygen isotopes demonstrates that local groundwater completely derives from local atmospheric wet deposition. The hydrogen and oxygen values of groundwater buried in shallow aquifer are more positive than those of groundwater in deep aquifer both in recharged and discharged area, indicating that groundwater in shallow aquifer is affected by evaporation. Meanwhile, the hydrogen and oxygen values of groundwater in discharged area are also more positive than those of groundwater in recharged area, showing that groundwater in discharged area has experienced obvious evaporation. The composition of dissolved inorganic carbon isotopes demonstrates that δ13C-DIC values of groundwater in shallow aquifer are more negative than those in deep aquifer both in recharged and discharged area, indicating that the dissolved inorganic carbon in shallow groundwater derives mainly from organic carbon deposition. At the same time, δ13C-DIC values of groundwater in discharge area are also more negative than those in recharged area due to relatively more organic carbon deposition. Groundwater in recharged area is dominated by Ca2＋ and HCO3 , and that in discharged area is dominated by Na＋ , HCO3 and SO4 2-.Combining with isotope compositions, we could conclude that hydro-chemical compositions of groundwater in recharged area are mainly controlled by dissolution and human activities, and those of groundwater in discharged area are mainly affected by dissolution, evaporation and concentration, cation exchange and human activities.