In the urban area of Rio Cuarto groundwater is used for domestic supply. The objective of the current research was to investigate the water dynamics and nitrate contamination in an unconfined aquifer system of Rio Cuarto River basin. Stable isotopes of water (δ¹⁸O and δ²H) and nitrate (δ¹⁵N–NO₃ and δ¹⁸O–NO₃) were used and combined with conventional chemical techniques and mixing modelling approaches to determine the recharge areas and identify the main origin of nitrate pollution. More enriched water isotope values were recorded in Rio Cuarto city than in the piedmont and mountains indicating local recharge for well batteries 2 and 3. The well battery 1 and the infiltration gallery showed more negative isotopic values, demonstrating a strong influence by the recharge from the piedmont sector (impoverished groundwater). The δ¹⁵N–NO₃ values and the Bayesian modeling showed that the dominant nitrate contamination source in the urban area is the on-site sanitation systems whereas in the peri-urban area nitrate contamination originates mostly from animal wastes. Both sources supply the aquifer with anthropogenic organic matter (>50%). The highest δ¹⁵N–NO₃ values were correlated with low dissolved oxygen values, indicating the occurrence of denitrification processes in some places. High NO₃ ions in the rural sector were attributed to the application of fertilizers and consequent nitrification processes. The samples from Rio Cuarto river located upstream of the Rio Cuarto City and close to the infiltration gallery showed the highest input from fertilizers (~40%), due to surrounding agricultural fields. The municipal well batteries showed good water quality (freshwater of low to extremely low nitrate concentration) which is linked to the high hydraulic conductivity of the aquifer that increases its capacity to dilute the contaminants. These results will be useful for local water administrators to improve water management.

在里奥夸尔托市区，地下水被用于生活用水。当前研究的目的是调查里奥夸尔托河流域无限制含水层系统中的水动力学和硝酸盐污染。的水稳定同位素（δ ¹⁸ O和δ ² H）和硝酸盐（δ ¹⁵ N-NO ₃和δ ¹⁸ O型NO ₃）与常规化学技术和混合建模方法结合使用，以确定补给区并确定硝酸盐污染的主要来源。在里奥夸尔托市记录的富集水同位素值比在山麓和山区要多，这表明井电池2和3的局部补给。井电池1和入渗廊道显示出更多的负同位素值，表明来自井补给的强烈影响。山麓地区（地下水贫乏）。的δ ¹⁵ N-NO ₃值和贝叶斯模型表明，城市地区主要的硝酸盐污染源是现场卫生系统，而在城市周边地区，硝酸盐污染主要来自动物粪便。两种来源都为含水层提供了人为有机物（> 50％）。最高δ ¹⁵ N-NO ₃值与低溶解氧值相关，说明反硝化处理的在一些地方发生。高NO ₃农村部门的离子归因于肥料的使用和随之而来的硝化过程。来自里奥夸尔托市上游且靠近渗透廊的里奥夸尔托河的样本显示，由于周围的农田，肥料的投入最高（约40％）。市政井筒显示出良好的水质（硝酸盐浓度低至极低的淡水），这与含水层的高水力传导性有关，从而增加了其稀释污染物的能力。这些结果对于当地水管理者改善水管理将是有用的。