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通过分析运城盆地地下水的碳同位素组成,结合水化学特征,揭示了盆地深层承压地下水的补给期为22～3 ka BP(现代碳百分比(a14C)6～38 pmC)。浅层地下水(71～89 pmC)由现代水或现代水和老水混合组成。深层地下水氢氧同位素组成特征(δ18O～-10‰;δ2H～-70‰)表明地下老水在气候较冷的环境下受到补给,而浅层地下水的氢氧同位素组成(δ18O～-8‰;δ2H～-51‰)特征与现代西安降水组成相似。浅层地下水NO3-平均含量(31mg/L)比深层地下水(1.8 mg/L)高,硝酸盐的δ15N-δ18ONO3组成(0‰～5‰)揭示了硝酸盐的主要来源为综合肥料。此外,浅层地下水的TDS由于蒸散发、矿物溶解,可达8.5 g/L(平均2.0 g/L),深层地下老水TDS可达1.8 g/L(平均1.1g/L)水质相对较好。研究区目前主要开采深层地下水,受断裂带影响,浅层地下水已经侵入中深层地下水并与之发生混合,严重影响了中深层地下水的水质。如果发生大规模的浅层地下水与中深层地下水混合,会造成中深层地下老水的NO3-、TDS等含量越来越高。
By analyzing the carbon isotope composition of groundwater in the Yuncheng basin and combining with the hydrochemical characteristics, it is revealed that the recharge period of deep confined groundwater in the basin is 22 ~ 3 ka BP (modern carbon percentage (a14C) 6 ~ 38 pmC). Shallow groundwater (71-89 pmC) consists of a mixture of modern or modern water and old water. The characteristics of the hydrogen and oxygen isotopes in deep groundwater (δ18O ~ -10 ‰; δ2H ~ -70 ‰) indicate that the old underground water is replenished in colder climates while the hydrogen and oxygen isotopic composition of shallow groundwater (δ18O ~ -8 ‰; δ2H ~ -51% o) features similar to the precipitation in modern Xi’an. The average NO3 content of shallow groundwater (31 mg / L) is higher than that of deep groundwater (1.8 mg / L), and the δ15N-δ18ONO3 composition of nitrate (0 ‰ -5%) reveals that the main source of nitrate is synthetic fertilizer. In addition, TDS in shallow groundwater is as high as 8.5 g / L (average 2.0 g / L) due to evapotranspiration and TDS in deep underground water is 1.8 g / L (average 1.1 g / L). Water quality is relatively good . At present, deep groundwater is mainly exploited in the study area. Affected by the fault zone, shallow groundwater has intruded into and mixed with groundwater in the deep ground and seriously affected the quality of groundwater in the middle and deep groundwater. If large-scale shallow groundwater mixed with middle-deep groundwater, the content of NO3- and TDS in old and middle underground water will be higher and higher.