Abstract A complete hydrogeological understanding of the deep Upper Jurassic carbonate aquifer in the South German Molasse Basin is essential for the future development of this important drinking water resource and geothermally used system. Water chemistry data, δ 13 CDIC, 14C of the dissolved inorganic carbon (14CDIC) and stable water isotope ( δ 18 O and δD) measurements have been used to evaluate a promising groundwater dating approach with 14C of dissolved organic carbon (14CDOC). The pre-concentration of dissolved organic matter (DOM) was performed by the easy applicable solid phase extraction (SPE) with a styrene-divinylbenzene copolymer sorbent (PPL). Based on the sampling campaign of seven groundwater wells conducted between 2017 and 2019, it was shown that the groundwater is mainly of Ca-HCO3 type with some evidence of ion exchange between Ca2+ and Na+ at two of the investigated wells. The δD values ranged from -89.4 ‰ to -70.9 ‰ while δ 18 O values varied between -12.5 ‰ and -9.8 ‰. The obtained stable water isotope signatures indicated that the groundwater is of meteoric origin and was recharged during warm climate (Holocene), intermediate climate and cold climate (Pleistocene) infiltration conditions. The measured 14CDOC activities varied from 5.7 pmC to 51.1 pmC and the calculated piston-flow water ages (ORAs) ranged from 4,200 years to 25,248 years using an initial 14C0DOC of 85 pmC. The calculated ORAs showed a very good correlation to the infiltration temperature-sensitive δ 18 O values which were affirmed with noble gas infiltration temperatures for two wells after Weise et al. (1991) and were also in good accordance with the atmospheric temperature record of the northern hemisphere from Dokken et al. (2015) . The results reflect a consistent hydrogeological picture of the carbonate aquifer, which also supports the applicability of the SPE-PPL method for 14CDOC dating in groundwater with a low DOC content ( 30,000 years and generally to an overestimation of the apparent water ages. This study gives insights into the promising approach of 14CDOC groundwater dating in carbonate aquifers with low DOC contents and allows future sustainable groundwater resource management of the investigated aquifer system.

中文翻译：

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溶解有机放射性碳的地下水测年：碳酸盐含水层的一种有前途的方法

摘要 对德国南部 Molasse 盆地上侏罗统深层碳酸盐岩含水层的完整水文地质认识对于这一重要饮用水资源和地热利用系统的未来开发至关重要。水化学数据、δ 13 CDIC、溶解无机碳的 14C (14CDIC) 和稳定的水同位素（δ 18 O 和 δD）测量已被用于评估具有 14C 溶解有机碳 (14CDOC) 的有前景的地下水测年方法。溶解有机物 (DOM) 的预浓缩是通过简单适用的固相萃取 (SPE) 和苯乙烯-二乙烯基苯共聚物吸附剂 (PPL) 进行的。根据 2017 年至 2019 年间进行的 7 口地下水井的采样活动，结果表明，地下水主要是 Ca-HCO3 类型，有一些证据表明在两个调查井中 Ca2+ 和 Na+ 之间存在离子交换。δD 值介于 -89.4 ‰ 至 -70.9 ‰ 之间，而 δ 18 O 值介于 -12.5 ‰ 和 -9.8 ‰ 之间。获得的稳定水同位素特征表明地下水是陨石来源的，在温暖气候（全新世）、中间气候和寒冷气候（更新世）渗透条件下补给。测得的 14CDOC 活性在 5.7 pmC 到 51.1 pmC 之间变化，计算的活塞流水年龄 (ORA) 范围从 4,200 年到 25,248 年，使用 85 pmC 的初始 14C0DOC。计算出的 ORA 与渗透温度敏感的 δ 18 O 值具有很好的相关性，Weise 等[20] 之后的两口井的惰性气体渗透温度证实了该值。(1991) 并且也很好地符合 Dokken 等人的北半球大气温度记录。(2015)。结果反映了碳酸盐含水层的一致水文地质图，这也支持 SPE-PPL 方法在低 DOC 含量（30,000 年，通常高估表观水年龄）的地下水中进行 14CDOC 测年的适用性。该研究给出深入了解 DOC 含量低的碳酸盐含水层中 14CDOC 地下水测年的有前景的方法，并允许未来对所研究含水层系统进行可持续的地下水资源管理。(1991) 并且也很好地符合 Dokken 等人的北半球大气温度记录。(2015)。结果反映了碳酸盐含水层的一致水文地质图，这也支持 SPE-PPL 方法在低 DOC 含量（30,000 年，通常高估表观水年龄）的地下水中进行 14CDOC 测年的适用性。深入了解 DOC 含量低的碳酸盐含水层中 14CDOC 地下水测年的有前景的方法，并允许未来对所研究含水层系统进行可持续的地下水资源管理。(1991) 并且也很好地符合 Dokken 等人的北半球大气温度记录。(2015)。结果反映了碳酸盐含水层的一致水文地质图，这也支持 SPE-PPL 方法在低 DOC 含量（30,000 年，通常高估表观水年龄）的地下水中进行 14CDOC 测年的适用性。该研究给出深入了解 DOC 含量低的碳酸盐含水层中 14CDOC 地下水测年的有前景的方法，并允许未来对所研究含水层系统进行可持续的地下水资源管理。