High surface water-groundwater connectivity characterizes watersheds underlain by karsts, increasing contaminant transport risks. However, karsts are highly complex, making research necessary to understand the transport of contaminants from the surface, through the aquifer, to discharge areas. In Yucatan, the lack of waste water treatment raises the risk of groundwater contamination. We monitored stable isotopes (δ¹⁸O-NO₃ and δ¹⁵N-NO₃), cadmium, and lead to document waste water contamination and transport during the rainy and dry seasons, using water samples collected along the Ring of Cenotes during each season. Specific conductance and pH showed no consistent seasonality, with conductance ranging from 0.5 to 55 mS/cm and pH ranging from 6.6 to 8.6 for most samples. Nitrate concentrations in the cenotes averaged 205 ± 260 μM and no seasonal pattern was observed. Cd and Pb concentrations were 0.1 to 37.9 μg/L and 0.2 to 243.2 μg/L, respectively. Nitrate stable isotope values were 2.6 to 27.2‰ for δ¹⁸O and 1.2 to 20.7‰ for δ¹⁵N. The statistical relationship between δ¹⁵N and δ¹⁸O, in dry season samples, indicated that denitrification was occurring. A scale measure for waste water recognition showed: (1) high variability among sites probably related with dry/rainy seasons and/or diverse anthropogenic activities; and (2) specific water quality variables that contribute to contamination at each site during each season. Importantly, our analyses indicate that in the area surrounding the Ring of Cenotes, waste water exhibits spatial and temporal patterns related to complex transport and dilution processes, as is the case in karsts in general.

中文翻译：

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尤卡坦半岛的地下水质量：来自稳定同位素和金属分析的见解

高地表水-地下水连通性是岩溶下流域的特征，增加了污染物运输的风险。然而，岩溶非常复杂，因此有必要进行研究以了解污染物从地表、通过含水层到排放区的迁移。在尤卡坦，缺乏废水处理增加了地下水污染的风险。我们监测了稳定同位素（δ ¹⁸ O-NO ₃和δ ¹⁵ N-NO ₃)、镉和铅，使用每个季节沿 Cenotes 环收集的水样记录雨季和旱季期间的废水污染和运输。比电导率和 pH 值没有表现出一致的季节性，大多数样品的电导率范围为 0.5 至 55 mS/cm，pH 值范围为 6.6 至 8.6。cenotes 中的硝酸盐浓度平均为 205 ± 260 μM，没有观察到季节性模式。Cd 和 Pb 的浓度分别为 0.1 至 37.9 μg/L 和 0.2 至 243.2 μg/L。δ ¹⁸ O的硝酸盐稳定同位素值为2.6～27.2‰，δ ¹⁵ N为1.2～20.7‰。δ ¹⁵ N与δ ¹⁸的统计关系O，在旱季样品中，表明正在发生反硝化作用。废水识别的尺度测量显示：(1) 可能与旱季/雨季和/或多种人为活动有关的地点之间的高度可变性；(2) 在每个季节导致每个地点污染的特定水质变量。重要的是，我们的分析表明，在 Cenotes 环周围的区域，废水表现出与复杂的运输和稀释过程相关的空间和时间模式，就像一般的岩溶情况一样。