The use of renewable resources alternative to fossil fuels, thus contributing to the reduction of CO₂ emissions, requires the assessment of eventual negative impacts on the environment. This study was devoted to the characterization of low-enthalpy geothermal resources and the potential contamination of geothermal effluents into the aquatic system. Thirty-five groundwater samples were collected in the Campidano (southern Sardinia, Italy), an area showing heat flow anomalies and thermal occurrences. Hydrogeological features inferred by literature were implemented by data acquired at each sampling site. Physical–chemical parameters, major, minor and trace components in groundwater were determined, together with the isotopic composition of the water. Six hydrogeological units with variable permeability were identified. According to geological and hydrogeological modeling, four of the six units appeared hydraulically connected, although not everywhere. The predominant groundwater flow was seen from north-east to south-west. The water temperature was in the range 17–42 °C, pH ranged from 6.7 to 8.6, dissolved oxygen varied from < 0.2 to 7.8 mg L⁻¹ and electrical conductivity from 0.8 to 10 mS cm⁻¹. Predominant cations were Na⁺ and Ca²⁺, predominant anions were either Cl⁻ or HCO₃⁻. The more saline waters showed anyhow a marked Na⁺–Cl⁻ chemical composition. Most waters were found either at near equilibrium with respect to calcite or slightly saturated, but under saturated with respect to gypsum. Isotopic values of δ²H and δ¹⁸O in the water samples indicated a meteoric origin. Particular attention was paid to potential contaminants, which should be evaluated when thermal waters are used in spa treatments and balneology. Concentrations of NO₃⁻ and NH₄⁺ above the Italian limits established for drinking water (50 mg L⁻¹ and 0.5 mg L⁻¹, respectively) occurred in one oxygenated groundwater and five reduced groundwater samples, respectively. Fluoride concentrations exceeding the Italian limit of 1.5 mg L⁻¹ were observed in three groundwater samples. The mean value of As was 3.2 µg L⁻¹, with one groundwater exceeding the 10 µg L⁻¹ of the legal value. The groundwater with the highest temperature (42 °C), an artesian well, was characterized by relatively high concentrations of Cl⁻, F⁻, Li, B, Ge, Rb, Mo, Cs, W, Sc and Ga. Overall results allowed to identify the area most suitable for geothermal exploitation. Deep fluids, probably located at a depth > 1 km, would rise up along faults or fractured zones in the granitic–metamorphic Paleozoic basement. Maximum temperatures of 90 °C in the thermal reservoir were estimated by silica and Na–K–Ca geothermometers. The δ¹⁸O enrichment shift occurring at high temperature was not observed. Due to high concentrations of some contaminants (e.g. Mo, W, B, F⁻), geothermal effluents derived from exploitation should be either re-injected or treated before discharge for avoiding the contamination of aquatic systems.

使用可再生资源替代化石燃料，从而有助于减少CO ₂排放，需要评估最终对环境的负面影响。这项研究致力于低焓地热资源的表征以及地热废水进入水生系统的潜在污染。在坎皮达诺（意大利南部撒丁岛）收集了35个地下水样本，该区域显示了热流异常和热事件。文献推断的水文地质特征是通过在每个采​​样点获得的数据来实现的。确定了地下水的物理化学参数，主要，次要和痕量成分，以及水的同位素组成。确定了六个渗透率可变的水文地质单元。根据地质和水文地质建模，六个单元中有四个出现了液压连接，虽然不是到处都有。从东北到西南方向看到了主要的地下水流。水温范围为17–42°C，pH范围为6.7至8.6，溶解氧范围为<0.2至7.8 mg L^-1和0.8至10 mS cm ^-1的电导率。主要阳离子是钠⁺和Ca ²⁺的，主要的阴离子要么氯^-或HCO ₃ ^- 。更盐水水域无论如何显示出明显的Na ⁺ -Cl ^-化学成分。发现大多数水相对于方解石处于接近平衡状态或略微饱和，但相对于石膏则处于饱和状态。的δ值的同位素² H和δ ¹⁸水样中的O表示流星起源。特别注意了潜在的污染物，在温泉水疗和美容学中使用热水时应评估这些污染物。NO浓度的₃ ^-和NH ₄ ⁺上述（50毫克的L建立了饮用水意大利限制^-1和0.5毫克的L ^-1分别）发生率分别为一个含氧地下水和五个减少地下水样品，。在三个地下水样品中观察到氟化物浓度超过意大利的1.5 mg L ^-1限值。As的平均值为3.2 µg L ^-1，其中一个地下水超过10 µg L ^-1法律价值。具有最高温度（42℃）的地下水，自流井，其特点是相对高浓度的Cl ^-，F ^- 。，李，B，葛，RB，钼，铯，W，Sc和镓允许总体结果确定最适合地热开采的区域。可能位于> 1 km深度的深层流体将沿着花岗—变质古生代基底中的断层或断裂带上升。二氧化硅和Na–K–Ca地热仪估算了热库中的最高温度90°C。的δ ¹⁸在高温下出现ö富集移未观察到。由于高浓度的某些污染物（例如钼，钨，B，F ^-），为避免对水生系统造成污染，应在排放前重新注入或处理源自开发的地热废水。