The Groot Aub (GA) settlement depends entirely on groundwater for domestic purposes and other development activities. Development activities are mainly agriculture, such as animal husbandry, chicken farming and crop farming using irrigation. However, these activities have the potential to contaminate the groundwater system. A total of 87 groundwater samples were collected from the boreholes in the study area during the dry and wet season. Water quality parameters (pH, salinity, total dissolved solids (TDS), electrical conductivity (EC) and hydrochemistry (Na+ > Ca2+ > Mg2+ > K+, and HCO3- > SO4(2-) > Cl-) of 5 boreholes and 1 reservoir tank were analysed. The dominant cations were attributed to cation exchange processes as a coupled exchange of Na+ + K+ replacing Ca2+; and Na+ replacing Mg²+ ions in the rock-water interactions. The HCO3- anion is attributed to underlying rich carbonate rocks in the study area and chemical reactions between groundwater and silicate minerals. TDS ranged from 639.01 to 1 998.96 mg/L. The microbial levels as indicated by heterotrophic plate count (HPC) values exceed the limits imposed by the local Namibian and WHO drinking water regulations. The Piper diagrams showed a mixed water type of mainly HCO3- and SO4(2-)anions and Na+ and Ca2+ > Mg2+ cations. The study shows that the elemental composition of the groundwater is impacted significantly by primarily anthropogenic activities and secondarily geogenic processes. Based on the results of this study it is recommended that a buffer zone be created between human activities and production boreholes to avoid further groundwater contamination.

Summary: The hydrological region 21 coast of Oaxaca has an active tourist dynamic, it generates significant economic income, and it is considered the fourth most important socioeconomic region in the state of Oaxaca. Similarly, hydrological region 23 coast of Chiapas, has an economy governed by tertiary sector activities and is comprised of the Istmo-Costa and Soconusco socioeconomic regions, the latter is the main region that contributes to the gross domestic product of the state of Chiapas. It should be noted that this socioeconomic growth has required a greater demand for water resources, which has led to water pollution. The deterioration of the area’s water resources is caused by the discharge of wastewater, solid waste and agrochemicals into natural waterways. In order to assess the state of the water resources of hydrological regions 21 and 23, 31 sampling sites were established in the spring of 2021 distributed in the main streams. Each sample was analyzed for chemical properties: pH, electrical conductivity (EC), major anions and cations (CO3 2-, HCO3-, Cl-, SO4 2-, Ca2+, Mg2+, Na+ and K+), total dissolved solids (TDS), percentage of sodium (%Na), adsorption ratio of sodium (RAS), residual sodium carbonate (RSC), permeability index (PI), as well as a hydrochemical evaluation. The waters of the hydrological regions 21 and 23 present as dominant facies the calcium-magnesium bicarbonate, whose possible origin is a consequence of the dilution process of the geological material (water-rock interaction) with low and medium concentrations. With respect to salinity, 45.16% are low salinity waters and 93.55% of the sites have low sodium, therefore, they are considered recommended for irrigation with moderate restrictions.

Resumen: La región hidrológica 21 costa de Oaxaca, presenta una activa dinámica turística, en ella se genera un ingreso económico importante y es considerada la cuarta región socioeconómica más importante del estado de Oaxaca. De igual manera, la Región Hidrológica 23 costa de Chiapas, tiene una economía regida por las actividades del sector terciario, está comprendida por las regiones socioeconómicas Istmo-Costa y Soconusco, ésta última es la principal región que aporta al producto interno bruto del estado de Chiapas. Cabe señalar, que dicho crecimiento socioeconómico ha exigido una mayor demanda del recurso agua, que ha ocasionado la contaminación del mismo. El deterioro de los recursos hídricos de la zona tiene su origen en la descarga de aguas residuales, de desechos sólidos y de agroquímicos a los cauces naturales. Con la finalidad de valorar el estado de los recursos hídricos de las regiones hidrológicas 21 y 23, se establecieron 31 sitios de muestreo en la primavera de 2021 distribuidos en las corrientes principales. En cada muestra se analizaron las propiedades químicas: pH, conductividad eléctrica (CE), aniones y cationes principales (CO3 2-, HCO3-, Cl-, SO4 2-, Ca2+, Mg2+, Na+ y K+), sólidos totales disueltos (STD), porcentaje de sodio (%Na), relación de adsorción de sodio (RAS), carbonato de sodio residual (CSR) e índice de permeabilidad (IP), así como una evaluación hidroquímica. Las aguas de las regiones hidrológicas 21 y 23 presentan como facie dominante la bicarbonatada cálcico-magnésica, cuyo posible origen es consecuencia del proceso de dilución del material geológico (interacción agua-roca) con concentraciones bajas y medias. Con respecto a la salinidad el 45.16% son aguas de salinidad baja y el 93.55% de los sitios tiene baja sodicidad, por lo tanto, se consideran recomendables para el riego con restricciones moderadas.

ABSTRACT The Oriental basin is located, due to its physiographic characteristics, in the lakes and volcanoes of the Anahuac, which in turn is included in the Transversal Neovolcanic Axis; a characteristic feature is presented, six volcanic cones whose origin is from phreatomagmatic explosion. The bottom is occupied by water, that receives the local name of Axalapascos; These are the crater-lakes (maars) Alchichica, Quechulac, Atexcac, La Preciosa, Aljojuca and Tecuitlapa. The composition and ionic concentration of groundwater in the Oriental basin is defined by the materials of volcanic origin with which it has contact. The quality of the water refers to its suitability for a specific use, that is, how well the quality meets the needs of the user. In this work, the concentrations of the main water ions of six crater lakes were determined. Studies of salinity and sodium, hydrochemistry, ionic composition and classification by specific ions are included. Samples and physicochemical determinations of water ions were carried out. Sodium (Na + ) and chloride (Cl - ) are the most dominant ions. The resulting SAR classifications show that they are not recommended due to the high concentration of the sodium ion, with the exception of the Quechulac and Aljojuca maars, which are conditioned. There are three crater lakes that are classified as bicarbonate-sodium, while the other three are chlorinated-sodium. It is concluded that most of the crater lakes have high salinity and sodicity and are not suitable for any use such as agricultural or human. Specific ions have low and medium concentration according to their classification.

RESUMEN La Cuenca Oriental de México se localiza, por sus características fisiográficas, en los lagos y volcanes del valle del Anáhuac, que a su vez se encuentra en el Eje Neovolcánico Transversal. Esta cuenca presenta un rasgo característico: seis conos volcánicos cuyo origen fue una explosión freatomagmática. El fondo está ocupado por cuerpos de agua, que reciben el nombre local de axalapascos y que son los lagos-cráter (maars) Alchichica, Quechulac, Atexcac, La Preciosa, Aljojuca y Tecuitlapa. La composición y concentración iónica de las aguas subterráneas en la Cuenca Oriental es definida por los materiales de origen volcánico con los que tiene contacto. La calidad del agua se refiere a su idoneidad para un uso específico, es decir, cumple o no con las necesidades del usuario. En este trabajo se determinaron las concentraciones de los principales iones del agua de seis lagos cráter. Se incluyen estudios de salinidad y sodicidad, hidrogeoquímica, composición iónica y clasificación por iones específicos. Se realizaron muestreos y determinaciones fisicoquímicas de iones del agua. El sodio (Na+) y el cloruro (Cl-) son los iones más dominantes. Las clasificaciones de la RAS resultantes muestran que estas aguas no son recomendables por la concentración alta del ion sodio, a excepción de los maars Quechulac y Aljojuca que son condicionadas. Se observan tres lagos cráter que se clasifican como aguas bicarbonatadas-sódicas, mientras que las otras tres son cloruradas-sódicas. Se concluye que la mayoría de los lagos cráter presentan alta salinidad y sodicidad y no son adecuados para ningún uso como el agrícola o humano. Los iones específicos tienen concentración baja y media de acuerdo a su clasificación.

Abstract: Groundwater discharges (GD) provide information for understanding the local hydrogeology of a region. This study comprehensively describes a GD in the coast of Quintana Roo, quantifying the volumetric discharge and describing the hydrochemistry and geophysics of the site in order to contribute to the knowledge of the coastal karst aquifer in Quintana Roo. The GD described is an oval opening with an approximate area of 0.0507 m2 where major elements, silicates, metals and stable isotopes of water (δ2H and δ18O) were quantified monthly. The contribution of the accumulated monthly rainfall (Qp) in the discharge flow was calculated; electrical resistivity tomography was performed to identify saturated zones and flow zones. In general, Na, K, Ca, Mg, and Cl tend to decrease as Qp increases. SiO2, ORP and salinity do not show clear relations with changes in Qp, only in some sampling events there was a positive relationship, while the rest of the time is negative or null. The water is sodium-potassium-chloride type. The contribution of groundwater dominates, seawater contributes between 2 and 16% of the flow. The greatest contribution of seawater is observed when the flow of the GD is low. The contribution of Qp is between 1 and 15% and is not measured immediately. Geophysics survey suggest the existence of a lens of free fresh water approximately 2.5 m thick and recharge zones, as well as the existence of small dissolution channels where groundwater flows. The results capture local and regional aquifer recharge events.

Resumen: Las descargas de agua subterránea (DAS) aportan información para entender la hidrogeología local dentro de una región. El objetivo de este estudio fue describir de manera integral una DAS en la zona costera de Quintana Roo para contribuir al conocimiento del acuífero kárstico costero en Quintana Roo. La DAS es una cavidad ovalada con un área aproximada de 0.0507 m2 donde mensualmente se cuantificaron elementos mayores, silicatos, metales e isótopos estables del agua (δ2H y δ18O). Se calculó el aporte de la precipitación pluvial mensual acumulada (Qp) en el caudal de la descarga, se realizaron tomografías de resistividad eléctrica para identificar zonas saturadas y zonas de flujo. En lo general el Na, K, Ca, Mg y Cl tendieron a disminuir cuando Qp aumenta. SiO2, ORP y salinidad no tuvieron una relación evidente con Qp durante el tiempo de medición. El agua es de tipo clorurada sódico potásica; domina el aporte de agua subterránea, el agua de mar contribuyó entre 2 y 16% del caudal. El mayor aporte del agua de mar se observó cuando el caudal de la DAS es bajo. La contribución de Qp fue de entre y 15% y no se observó de manera inmediata. La geofísica apunta a un lente de agua dulce libre de aproximadamente 2.5 m de espesor y zonas de recarga, así como la existencia de pequeños canales de conducción por donde fluye el agua subterránea. Los resultados capturan eventos locales y regionales de recarga del acuífero.

Resumen El presente trabajo se desarrolló en una cuenca rural del partido de Tandil, Provincia de Buenos Aires, Argentina. Su objetivo fue diseñar una red ambiental de monitoreo del recurso hídrico subterráneo en la cuenca del arroyo Chapaleofú, que integre, más allá de la mirada hidrológica clásica (hidrodinámica e hidroquímica), variables fisicoquímicas y de manejo del recurso en cada sitio de muestreo. De 104 perforaciones censadas se se leccionaron 36 aplicando en un SIG un mallado sobre la cuenca. En cada celda se seleccionó una perforación com parando las siguientes variables: accesibilidad, encamisado, mantenimiento, conductividad eléctrica, distancia a la perforación más cercana, distancia al baricentro de la celda, muestra directa del acuífero y toma de muestra y profundidad del nivel del agua en la misma perforación. La hidroquímica y la hidrodinámica se evaluaron en una campaña donde se tomaron muestras para análisis fisicoquímico y se midieron las profundidades del nivel del agua. Se relevaron variables de manejo del recurso (mantenimiento, estado, uso de suelo en el lote de la per foración y uso de suelo en el establecimiento) y se relacionaron con la potabilidad del agua. Se eliminaron otras 4 perforaciones que presentaron agua no potable. Se seleccionaron 20 perforaciones en el sector de serranías, 7 en el piedemonte y 5 en la llanura. La hidroquímica varió de bicarbonatada cálcica y/o magnésica en la serranía a bicarbonatada sódica en la llanura. No se encontró relación entre el manejo del recurso y su calidad, esto muestra la efectividad en la selección de sitios no contaminados.

Abstract This work was developed in a rural basin of the Tandil district, Province of Buenos Aires, Argentina. Its objective was to design an environmental network for monitoring the groundwater resource in the Chapaleofú stream basin, which integrates, beyond the classical hydrological view that evaluates the hydrodynamic and hydrochemistry, physicochemical and resource management variables in each sampling site, in a basin located in a rural area. 104 perforations were recorded and 36 were selected by applying a mesh over the basin in a GIS. In each cell, a perforation was selected comparing the variables: acces sibility, jacketing, maintenance, electrical conductivity, distance to the nearest perforation, distance to the center of the cell, direct sample from the aquifer, and sampling and water depth in the same drilling. Hydrochemistry and hydrodynamic were evaluated in a campaign in which samples were taken for physicochemical analysis and the depths of the water level were measured. The variables of resource management surveyed (maintenance, condition, use of soil in the drilling lot and use of soil in the establishment) were related to water potability. A second reduction of the perforations was made, removing four that presented poor quality. Twenty boreholes were selected in the hills sector, seven in the piedmont sector and five in the plain. The hydrochemistry ranged from calcium and / or magnesium bicarbonate in the hills sector to sodium bicarbonate in the plain. No relationship was found between resource management and water quality. This shows the effectiveness in the selection of uncontaminated sites.

RESUMEN El agua subterránea es la principal fuente de consumo en muchos centros urbanos y áreas rurales de Bolivia, tal es el caso del Municipio de San Pedro ubicado en el departamento de Santa Cruz. El presente estudio se realizó con la finalidad de determinar la calidad fisicoquímica del agua subterránea de consumo en 16 comunidades rurales ubicadas dentro del municipio de San Pedro. Los resultados mostraron valores de pH ligeramente alcalinos comprendidos entre 7,8 y 8,6 y la conductividad eléctrica mostró valores en un rango que va de 313,3 a 1189 µS/cm. Las aguas son predominantemente del tipo Na-HCO3 y contienen elevadas concentraciones de fluoruro (F-) en un rango que va de 2,1 a 6,4 mg/L excediendo el valor máximo recomendado por la Organización Mundial para la Salud (OMS). Cálculos de índice de saturación (IS) muestran que la fase mineral que podría dar origen al elevado contenido de F- en agua es la (F-Apatita).

ABSTRACT The main source of drinking water in many urban centers and rural areas of Bolivia is Groundwater. This is the case of the Municipality of San Pedro located in the department of Santa Cruz. The present study was carried out to determine the physicochemical quality of groundwater used for consumption in 16 rural communities located within the municipality of San Pedro. The results showed slightly alkaline pH values between 7.8 and 8.6 and electrical conductivity in the range 313.3 to 1189 µS/cm. The waters are predominantly of the Na-HCO3 type and contain high concentrations of fluoride (F-) in in the range 2.1 to 6.4 mg/L, exceeding thus, the maximum value recommended by the World Health Organization (WHO). Saturation index (SI) calculations showed that the mineral phase that could give rise to the high F- content in water is (F-Apatite).

RESUMO O conhecimento dos mecanismos que controlam a hidroquímica das águas subterrâneas é um requisito fundamental para compreender a evolução hidroquímica e avaliar a qualidade da água dos recursos hídricos subterrâneos. Por consequência, para compreender o processo que governa a variabilidade da hidroquímica e dinâmica de escoamento dos aquíferos Parecis e Ronuro, foi empregado uma abordagem combinando o uso de análises estatísticas e caracterização isotópica. A matriz de correlação permitiu verificar que os maiores coeficientes de correlação foram observados entre HCO3-, Ca2+, Mg2+ - Sr2+, SO42-. e F-, sugerindo que esses parâmetros são derivados da mesma fonte, provavelmente a interação rocha/água. Adicionalmente, também observamos correlação moderada a alta entre NO3-, Cl-, Na+, K+ e Ba2 +, que coletivamente são indicativos da contaminação por efluente doméstico. Complementarmente, a Análise de Componentes Principais permitiu identificar que grande parte da variância da histoquímica das amostras avaliadas é controlada por HCO3-, Ca2+ e Mg2+ associados à interação rocha-água. Quanto aos valores dos isótopos 18O e 2H, foi possível notar que as recargas do aquífero são de origem meteórica e que as amostras do Aquífero Ronuro são mais enriquecidas que as amostras SAP. Os resultados alcançados reforçam a capacidade das técnicas de análise estatística multivarida para discernir o processo principal que controla a variabilidade da hidroquímica da água subterrânea.

ABSTRACT Knowledge of mechanism controlling the hydrochemistry of groundwater are crucial requirement to understand the hydrochemical evolution and evaluate the water quality of subsurficial water resources. Thus, to understand the process governing the hydrochemistry variability and flow dynamics of the Parecis and Ronuro Aquifers, the use of statistical analysis and isotopic characterization were combined. In the correlation matrix it was found that the highest correlation coefficient was observed for HCO3-, Ca2+, Mg2+, Sr2+, SO42-, and F-, which suggested that these parameters are derived from the same source, most likely from rock–water interactions. Additionally, we noticed moderate to high correlation among NO3-, Cl-, Na+, K+, and Ba2+, which collectively are indicative of domestic sewage contamination. Finally, a principal component analysis (PCA) identified that the most variance in hydrochemistry from the evaluated samples was controlled by HCO3-, Ca2+ and Mg2+, which is associated with rock–water interaction. Regarding the 18O and 2H isotope values, it could be observed that the aquifer recharges were of meteoric origin and that the Ronuro Aquifer samples were more enriched than the PAS samples. This work reinforces the capability of multivariate statistics to discern the main process that controls the variability of groundwater hydrochemistry.

ABSTRACT This study focuses on the impact of the seasonal variability of rainfall on the availability of water Plateau Mbé between november 2017 and august 2018, we took 120 samples from eigth (08) water points (1 well, 4 drillings and 3 rivers) which we analyzed in the laboratory. The sample were used to characterize the physical and chemical elements of the water. The results obtained were treated with different methods. They show that the values of the analyzed waters between four (04) seasons do not show considerable variation and all comply with the standards prescribed by the WHO for drinking water except the proven abnormal temperature averaging 27 °C and an average pH of 5,0 thus confirming the character of acid water throughout this study area.

RESUMEN Este estudio se enfoca en el impacto de la variabilidad estacional de la lluvia en la disponibilidad de agua de la meseta Mbé entre noviembre de 2017 y agosto de 2018. Para caracterizar los elementos físicos y químicos del agua se analizaron en el laboratorio 120 muestras de ocho puntos de agua (un pozo, cuatro perforaciones y tres ríos). Los resultados muestran que los valores de las aguas analizadas en cuatro estaciones no evidencian una variación considerable y todos cumplen con los estándares prescritos por la OMS para el agua potable, excepto por la temperatura anormal comprobada que promedia 27 °C y un pH promedio de 5,0 que confirma el carácter ácido del agua en toda el área de estudio.

ABSTRACT The main objective of this study was to evaluate the groundwater quality for domestic, agriculture use and to describe fluoride contamination in groundwater and their impacts on human health. 67 groundwater samples were collected and analyzed for major ions. Water Quality Index (WQI), Piper diagram and Gibbs diagrams were calculated to measure the suitability of groundwater for drinking purpose. The hazards index value was calculated to estimate the noncarcinogenic risk to adult (male, female) and children suggested by the United States Environmental Protection Agency (USEPA). The irrigation indices were calculated to evaluate the quality of water for irrigation purpose. Statistical methods such as principal component and hierarchical cluster analysis were used to analyses the inter-relationship of data. Hydrochemistry of the samples shows, the major ions in the order of Ca2+>Mg2+>Na+ and Cl−>SO4− in the study area. WQI value of groundwater, 74.62% of sample locations are good and 25.38 % of sample locations need primary treatment for drinking purpose. The results of the hazards index show that 65.67% of the sample locations exceeds the tolerable limit for non-carcinogenic risk (greater than one) for children higher than the risk level for Male and female. Statistical report of PCA and HCA reveals that Ca-Na-HCO3-F has positive loading and TDS-EC has negative loading. The study results show that rock-water interaction and anthropogenic activities are the major factors that influence the quality of groundwater. The continuous intake of excess concentration fluoride causes bone diseases and teeth problems.

Resumo Este artigo apresenta os primeiros dados geoquímicos de detalhe da água dos arroios Camaquã das Lavras e Hilário, Lavras do Sul-RS. Neste estudo foram utilizadas análises geoquímicas e geoestatísticas para estabelecer as influências antropogênicas ou naturais na região. Os resultados permitiram classificar as águas como mole e intermediária com pH ácido e neutro. A condutividade elétrica variou de 37.2 a 62.9 μs cm-1 e a alcalinidade total entre 4 e 30 mg L-1. Razões e padrões de distribuição indicam que o intemperismo de argilominerais é dominante nas amostras investigadas. Seguido pelo intemperismo do feldspato em ambiente sob condições de dureza temporária. O enriquecimento de Cu, Rh e Cd é associado à depósitos minerais da região, à diversidade litológica e às atividades humanas. Todos os valores medidos atendem aos padrões estabelecidos pelas Portarias-Brasil nºˢ 2914/2011, 36-GM/1990 e 1469/2000.

Abstract This article presents the first detailed geochemical data of the water from Camaquã das Lavras and Hilário Streams from Lavras do Sul-RS. Geochemical and statistical analyses were used in this study to establish the anthropogenic or natural influence on the region. The results classified the waters as soft and intermediate with acidic and neutral pH. The electrical conductivity varies from 37.2 to 62.9 μs cm-1 and the total alkalinity ranges from 4 to 30 mgL-1. The distribution patterns and ratios indicate that clay mineral weathering is dominant on the investigated samples. It is followed by feldspar weathering in an environment under temporary hardness conditions. Cu, Rh, and Cd enrichment is associated with the many mineral deposits of the region, lithological diversity and human activities. All the measured values conform with the standards set by Brasil-Ordinance nos. 2914/2011, 36-GM/1990 and 1469/2000.

Abstract This study compares two mangroves with different land uses in the Jaguaribe River estuary, harboring large shrimp farms, and in the more pristine Pacotí River estuary. Normalized Difference Vegetation Index (NDVI) was used to compare the overall health of the forests. Measures of suspended matter (TSS), total (TP), particulate (PartP) and soluble reactive phosphorus (SRP) in the inflow and outflow waters of tidal channels draining the mangroves were performed during tidal cycles. NDVI varied from 0.65 in the Jaguaribe estuary to 0.85 in the Pacotí, suggesting the impact of shrimp farm effluents on mangrove canopy cover. The shrimp farm influenced site showed 10 times larger absolute ∑P (TP + PartP + SRP) = 1.2-5.2 kg.hr-1) flux than the pristine site (∑P = 0.22 kg.hr-1). Tidal balances showed smaller retentions of the total influx: 28-54%; 44-45%; 38-65% and 8-53% for TSS; TP; SRP; and PartP respectively, in the shrimp farm influenced site to over 93% of the total tidal input of TSS and all P fractions in the pristine mangrove. This suggests that mangrove phosphorus accumulation is decreased in the forest with lower NDVI and limits mangrove’s potential as a natural barrier to the nutrient transport to adjacent estuarine and coastal waters.

ABSTRACT: Chemical weathering and soil removal rates are responsible for the Earth’s landscape, composition of surface and groundwater, producing the soils and buffering the composition of the atmosphere. This study aimed to assess the chemical weathering and soil removal rates in the Sorocaba River basin, São Paulo State, Brazil, allowing answering the questions about the dynamics of fluvial transport of dissolved and suspended solids, the chemical weathering processes and associated atmospheric/soil CO2 consumption, and the relationship between chemical weathering and soil erosion rates. The annual specific flux of total suspended solids and total dissolved solids were 49.59 and 60.97 t/km2/yr. The chemical weathering process dominant in the Sorocaba River basin was the monosiallitization (RE = 2.4), with an associated atmospheric/soil CO2 consumption of 2.3 × 105 mol/km2/yr. The chemical weathering and soil removal rates were 7.2 and 29.8 m/Myr, respectively, indicating a soil thickness reduction. Finally, the soil removal rate in the Sorocaba River basin is almost 3-fold higher than the Cenozoic soil removal rates, being this difference related to the current land use which increased the soil removal processes.

ABSTRACT The Nor Yauyos Cochas Landscape Reserve (RPNYC) presents high Andean wetlands, whose peat bogs contain their subterranean waters, which are influenced by their hydrochemistry. Thus, these ecosystems are important sources of food, water, shelter and nesting place for a diversity of birds and wild animals. The objective of the research was to generate knowledge about the chemistry of the water deposited in the wetland of the Moyobamba sector, through the process of hydrochemical characterization and its temporal space variability. The methodology was based on the recording of the physicochemical properties (pH, temperature and EC) of 34 wells strategically distributed throughout the bofedal area, and the majority constituent analysis corresponding to a sample of 10 wells (anions: HCO3-, SO4 2 -, Cl-, CO3 -2 and cations: Na +, K +, Ca+2, Mg+2). The measurements were made considering the grouping in three sectors and by season (May, July and October of 2017, dry season and February of 2018, wet season). The data were analyzed from the Piper diagram (% meq / l) and specific statistical tests (Descriptive, ANOVA and correlation). The dominant water type was calcium bicarbonated (HCO3- - Ca+2) in 95% of the wells and magnesium bicarbonated (HCO3- - Mg+2) in the remaining 5%, influenced by the limestone present in their formations geological the HCO3-, Ca+2, Mg+2 and Na+ ions registered an increase in their concentration and EC as the dry season passed. While the pH of the water presented a slightly acid character (pH ≅ 6,6), with an average temperature of 8,1 ° C; this normal value is considered for this type of wetlands. A positive mean correlation was found between bicarbonate ions (HCO3-) and calcium (Ca+2) and a weak positive correlation between pH and EC.

RESUMEN La Reserva Paisajística Nor Yauyos Cochas (RPNYC) presenta bofedales altoandinos, en cuyas turberas se encuentran contenidas sus aguas subterráneas, las cuales están influenciadas por su hidroquímica. Así, estos ecosistemas son importantes fuentes de alimentación, agua, refugio y lugar de anidación para una diversidad de aves y animales silvestres. El objetivo de la investigación fue generar conocimiento sobre la química del agua depositada en el bofedal del sector Moyobamba, a través del proceso de caracterización hidroquímica y su variabilidad espacio temporal. La metodología se basó en el registro de las propiedades fisicoquímicas (pH, temperatura y CE) de 34 pozos (aniones: HCO3-, SO4 2-, Cl-, CO3 -2 y cationes: Na+, K+; Ca+2; Mg+2). Las mediciones se realizaron considerando el agrupamiento en tres sectores y por temporada (mayo, julio y octubre del 2017, temporada seca y febrero del 2018, temporada húmeda). Los datos fueron analizados a partir del diagrama de Piper (% meq/l) y pruebas estadísticas específicas (Descriptivos, ANOVA y correlación). El tipo de agua dominante fue la bicarbonatada cálcica (HCO3- - Ca+2) en el 95% de los pozos y la bicarbonatada magnésica (HCO3- - Mg+2) en el 5% restante, influenciadas por las calizas presentes en sus formaciones geológicas. Los iones HCO3-, Ca+2, Mg+2 y Na+ registraron un aumento en su concentración y CE a medida que transcurría la temporada seca. Mientras que el pH del agua presentó un carácter ligeramente ácido (pH ≅ 6,6), con temperatura promedio de 8,1°C, siendo considerado este valor normal para este tipo de humedales. Se encontró correlación positiva media entre los iones bicarbonato (HCO3-) y calcio (Ca+2), y una correlación positiva débil entre el pH y la CE.

Resumen Se evaluaron las características hidroquímicas de una cuenca intramontana, ubicada en la Sabana de Bogotá, usando indicadores y métodos estadísticos, basados en los datos fisicoquímicos de 10 pozos de monitoreo obtenidos durante dos campañas de muestreo realizadas en el año 2014, para determinar las características hidroquímicas generadas por la interacción agua/sedimento del acuífero y determinar las condiciones de calidad del agua subterránea. Para ello, (1) se aplicaron indicadores hidroquímicos para evaluar los procesos de interacción entre el agua y la matriz sedimentaria del acuífero, corroborados mediante (2) la aplicación del análisis de componentes principales, que develó asociaciones fuertes entre las variables (Na +, Mg 2+, Ca 2+, SO 2− 4 y HCO 3 − ), y la influencia de las variables T, pH y STD en los procesos hidroquímicos que gobiernan el acuífero, además (3) se analizaron los parámetros fisicoquímicos, comparándolos con la normatividad ambiental colombiana para consumo humano y para riego. Como resultados, se determinó que en la matriz agua-sedimento, se suscitan procesos de intercambio catiónico reverso y meteorización de los minerales presentes en las formaciones que conforman el acuífero analizado, así mismo, que las muestras de agua obtenidas no presentan características de calidad que permita su uso para riego o consumo humano.

Abstract The hydrochemical characteristics of an intramontane basin, located in the Bogotá Savannah, were evaluated using indicators and statistical methods, based on 10 monitoring wells physicochemical data, obtained during two sampling campaigns conducted in 2014, to establish the hydrochemical characteristics that are generated by the groundwater and sedimentary matrix interaction of the aquifer and determine the extracted groundwater quality conditions’ in the studied aquifer. To analyze the data, (1) hydrochemical indicators were applied to evaluate the groundwater and the sedimentary matrix interaction processes’ in the studied aquifer, which was corroborated by (2) principal components analysis, which allowed to disclose strong associations between the variables (Na +, Mg 2+, Ca 2+, SO 2− y HCO3−), and T, pH y TDS variables influence on the hydrochemical process that govern the analyzed aquifer, in addition (3) physicochemical parameters were compared with the Colombian environmental regulations, referring to human consumption and irrigation use. As results, in watersediment matrix was determined reverse cation exchange and minerals meteorization processes, present in the formations that conform the analyzed aquifer, likewise, the water samples obtained do not present quality characteristics that allow its use for irrigation or human consumption.

Underground coal gasification (UCG) is the conversion of coal in situ into a usable synthetic gas. One of the major environmental concerns with UCG is the possibility of groundwater from the coal seam aquifer contaminating the shallow aquifers via hydraulic connections. The coal seam aquifers are usually confined aquifers but can have hydraulic connections to the shallow aquifers due to faults/fractures or any man-made connections, including boreholes. The aim of this paper is to study groundwater hydraulic connections across various aquifers at the UCG site at Majuba, using hydrochemistry and stable isotope (6(18)O and 6²H) tools. Physical and chemical processes such as diffusion and condensation generate isotopic differentiation in natural waters that can be used to deduce the origins of different waters, and in groundwater the spatial isotopic distribution can be used to deduce hydraulic connections between different aquifers. The Majuba UCG site consists of shallow, intermediate, and saline deep aquifer systems at a depth of 70 m, 180 m, and 300 m respectively. Samples were taken from each aquifer system together with supplementary samples from an on-site water storage dam. The analyses of isotopic compositions led to the determination of the possible sources of each sample. The deep aquifer is represented by an isotopic signature that is depleted in heavy isotopes with average values of -41.7% and -7.02% for 8(18)O and 6²H respectively, while the shallow aquifer is enriched with corresponding average values of -19.9% and -3.3%. Hydrochemical data also showed different water types: a sodium chloride type in the deep aquifer and a sodium bicarbonate water in the shallow aquifer. The results indicate that the shallow aquifer and the deep aquifer are not hydraulically connected, and therefore it is unlikely that groundwater from the gasification zone would contaminate the shallow aquifer.