Organic and inorganic carbon reservoirs are investigated in surface and groundwater in the semi to hyper-arid Río Loa Basin in Northern Chile. Part of the study area is within the Andean volcanic arc, and volcanism is responsible for large inputs of ¹⁴C-depleted CO₂ which hampers groundwater residence time estimations using dissolved inorganic carbon (DIC). To better understand the area’s carbon system, we investigated ¹⁴C and δ¹³C in dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in groundwater and surface water. DOC concentrations are low in all water samples analyzed, 16–53 μM. Fluorescence and δ¹³C measurements on DOC indicate that dissolved organic matter (DOM) entering groundwater has characteristics of humic compounds derived from terrestrial plants in the recharge area. Fluorescence is lost in groundwater in the lower part of the system due to microbial or abiotic degradation. Changes in ¹⁴C_DOC and δ¹³C_DOC also indicate that microbial activity contributes to DOC, possibly from geogenic CO₂. While the range of ¹⁴C_DIC is very large, 1.6 to >50 pmC, that of ¹⁴C_DOC is restricted between 53 and 72 pmC. We estimated C residence times in the volcanic arc, based on corrected ¹⁴C_DOC, are <3,200 years compared to ¹⁴C_DIC estimates that range from 2,000 to 15,000 years. While uncertainties in the estimate due to sources and sinks of DOC within the different aquifers exist, the range in age is somewhat restricted, despite the large distances that separate different sampling points and the different types of aquifers sampled. This leads us to conclude that wetter climate conditions in the past increased recharge and storage of the aquifers, and DOC inputs to recharging water was enhanced by more widespread plant growth during those past wet climates.

在智利北部半干旱至超干旱的里奥洛阿盆地，研究了地表和地下水中的有机碳和无机碳储层。研究区域的一部分位于安第斯火山弧内，而火山活动负责大量消耗¹⁴ C的CO ₂，这妨碍了使用溶解的无机碳（DIC）估算地下水的停留时间。为了更好地了解该地区的碳系统，我们研究了¹⁴ ℃，δ ¹³在地下水和地表水溶解的有机碳（DOC）和溶解的无机碳（DIC）C。在所有分析的水样中，DOC浓度都很低，为16–53μM。荧光和δ ¹³DOC上的C测量结果表明，进入地下水的溶解性有机物（DOM）具有在补给区衍生自陆生植物的腐殖质化合物的特征。由于微生物或非生物降解，系统下部地下水中的荧光损失。在变化¹⁴ Ç _DOC和δ ¹³ Ç _DOC还表明微生物活性有助于DOC，可能来自环境地球化学CO ₂。虽然¹⁴ C _DIC的范围非常大，为1.6至> 50 pmC，但¹⁴ C _DOC的范围却限制在53至72 pmC之间。根据校正后的¹⁴，我们估算了在火山弧中的C停留时间C _DOC小于3200年，而¹⁴ C _DIC估计为2,000到15,000年。尽管存在由于不同含水层内DOC的来源和汇而造成的估算不确定性，但尽管分隔不同采样点和不同类型含水层的距离很大，但年龄范围还是受到一定限制。这使我们得出结论，过去潮湿的气候条件增加了含水层的补给和储存，而在过去的潮湿气候中，植物的生长更加广泛，从而增加了DOC补给水的投入。