Guarani Aquifer System Research Articles

Impact of hydrophobic and hydrophilic surface properties on Pseudomonas aeruginosa adhesion in materials used in mineral water wells

Microbiologically contaminated water is a significant source of infections in humans and animals, with Pseudomonas aeruginosa (PSA) being particularly concerning due to its ability to thrive in water environments and its resistance to many disinfectants. Therefore, this study investigates the adhesion potential of PSA strains on various materials used in mineral water extraction wells, focusing on hydrophobic and hydrophilic properties. Mineral water samples were collected from three wells (P-01, P-07, and P-08) within the Guarani Aquifer System and Fractured Aquifer System (SAF) in Brazil. The physicochemical properties of the water, including concentrations of Sr (strontium), Fe (iron), Si (silicon), SO4 2− (sulfate ions), Cl− (chloride ions), and ORP (oxidation-reduction potential), were analyzed. Results indicated higher PSA adhesion on hydrophobic materials, particularly high-density polyethylene (HDPE) and geomechanically plasticized polyvinyl chloride (PVC). Multiple correlation analyses revealed positive correlations between PSA adhesion on hydrophilic materials and Sr, Fe, Si, SO4 2−, and Cl− concentrations. Conversely, ORP negatively correlated with bacterial adhesion on PVC surfaces, suggesting higher ORP values reduced PSA attachment. These findings highlight the importance of water composition and material properties in influencing bacterial adhesion and potential biofilm formation in mineral water extraction systems.

Three-dimensional model and environmental fragility in the Guarani Aquifer system, SE-Brazil

The Guarani Aquifer System (GAS) is a vast transboundary continental sedimentary basin in southern South America, encompassing sedimentary rocks and basalt flows across Uruguay, Paraguay, Argentina, and Brazil. It serves as a crucial water resource for urban supply and irrigation. This study aims to propose geophysical, geometric, and fragility models of the GAS in a critical exploitation area, utilizing geological data, geophysical logs, geomorphometry, and information from tubular wells. The models define distinct geophysical ranges for each formation and identify contacts between sedimentary and basaltic rocks. Integration of horizontal and vertical spatial distributions of geophysical and geological data forms a 3D model, revealing basaltic flows and intrusions distribution in fragile areas between formations, and potentially connecting aquifer layers. Natural fragility zones, characterized by high fracture densities, are observed in the central-east region, while outcrop and recharge areas of the main aquifer hydrofacies are found in the north. The 3D model highlights similarities between the topography of the Botucatu Formation (KJb – eolian sandstones) and the potentiometry of GAS at local scales, and overexploitation zones in Ribeirão Preto's city center. The assessment prioritizes areas at risk and conservation strategies for sedimentary aquifers, emphasizing interactions between surface and groundwater and addressing issues of overexploitation, identifying high-impact risks on GAS hydrodynamics and water quality.

How much rainwater contributes to a spring discharge in the Guarani Aquifer System: insights from stable isotopes and a mass balance model

ABSTRACT Outcrops play an important role in groundwater recharge. Understanding groundwater origins, dynamics and its correlation with different water sources is essential for effective water resources management and planning in terms of quantity and quality. In the case of the Guarani Aquifer System (GAS) outcrop areas are particularly vulnerable to groundwater pollution due to direct recharge processes. This study focuses on the Alto Jacaré-Pepira sub-basin, a watershed near Brotas, a city in the central region of the state of São Paulo, Brazil, where groundwater is vital for supporting tourism, agriculture, urban water supply, creeks, river and wetlands. The area has a humid tropical climate with periods of both intense rainfall and drought, and the rivers remain perennial throughout the year. Therefore, the aim of this study is to investigate the interconnections between a spring and its potential sources of contribution, namely rain and groundwater, in order to elucidate the relationships between the different water sources. To achieve this, on-site monitoring of groundwater depth, rainfall amount, and stable isotope ratios (deuterium (2H) and oxygen-18 (18O)) from rain, spring discharge, and a monitoring well was carried out from 2013 to 2021. The results indicate that the mean and standard deviations for δ18O in rainwater exhibit higher variability, resulting in −4.49 ± 3.18 ‰ VSMOW, while δ18O values from the well show minor variations, similar to those of the spring, recording −7.25 ± 0.32 ‰ and −6.94 ± 0.28 ‰ VSMOW, respectively. The mixing model’s outcomes reveal seasonal variations in water sources contribution and indicate that groundwater accounts for approximately 80 % of spring discharge throughout the year. Incorporating stable isotopes into hydrological monitoring provides valuable data for complementing watershed analysis. The values obtained support the significance of the aquifer as a primary source, thereby offering critical insights into stream dynamics of the region.

Dyke positioning according to sedimentary basins markers by processing airborne magnetic data at basalt covered areas

SUMMARY Airborne magnetics have found few applications in investigating basalt-trapped areas because anomaly interferences from deep and shallow sources prevent clear identification of subjacent dyke systems. The structural positioning of dykes is of major importance in basin studies due to their role as a heat source for maturing organic matter and plumbing capacity to feed intrusive bodies and surface lava flows. Aeromagnetic data in such a scenario can outline faults and the basin framework but faces difficulties in identifying the distribution of dykes seated at different depth levels. We present a procedure that sequentially combines conventional processing techniques to identify and retrieve the magnetic anomaly content with 2-D properties, as expected from tabular dykes with contrasting magnetic properties with respect to the background medium. The mean direction of 2-D anomalies is quantitatively evaluated by tracking the directions in which the horizontal component of the transformed anomaly mostly vanishes. The observed field is then cosine-direction filtered to retain the anomaly content along this mean direction. Once isolated, the filtered 2-D content of the anomaly is interpreted with multiple thin-sheet models to determine the dyke distribution and their respective depths to the top. The inferred depths are interpreted concerning basin stratigraphic markers to recognize dykes possibly serving as a heat source for geothermal or petroleum and gas maturation, acting as compartments to aquifer systems, or determining the location of former conduits once feeding the lava flow volcanism. The developed procedure is applied to the Ponta Grossa Dyke Swarm, along its northwestern continuation beneath the basalt-capped sedimentary sequences of the Palaeozoic Paraná Basin. The distribution of the dykes recognizes a sequence confined to the bottom Palaeozoic formations with petroleum and gas potential, a sequence intercepting the upper layers forming the Guarani aquifer system (GAS) and dykes at different depth levels within the basalt Serra Geral traps, indicative of at least two feeding events supplying the Mesozoic surface lava flows.

Bacterial diversity of mineral well water from ten sources belonging to the Guarani aquifer system: Assessment by cultivation-dependent and cultivation-independent methods and their correlation with water physicochemical properties

Mineral water must be safe for consumption. The study aimed to assess the bacterial diversity of mineral water samples collected directly from extraction wells through both cultivation-dependent and cultivation-independent analysis and their correlation with physicochemical properties. The physicochemical characterization included the analysis of 40 different minerals and parameters such as pH, conductivity, oxidation-reduction potential (ORP), total dissolved solids (TDS), salinity (PSU), and temperature (T). For the cultivation-dependent analysis, the counts included heterotrophic bacteria at 22 and 36 °C, total coliforms (TC), Escherichia coli (EC), and Pseudomonas aeruginosa (PSA). The cultivation-independent analysis comprised 16 S rRNA metataxonomic data analysis. The pH of the mineral water samples at wells ranged from 5.02 to 6.73 (non-dimensional), conductivity ranged from 20 to 174 μS/cm, ORP varied between 3.1 and 289 mV, TDS ranged from 10 to 87 mg/L, PSU ranged from 0.01 to 0.08 (non-dimensional), and the temperature range was between 19 and 22 °C. The results revealed counts of PSA in the mineral water samples from wells P-01 and P-02, with an average of 0.18 log CFU/250 mL. The samples from well P-09 exhibited average counts of EC at 0.40 log CFU/250 mL (0.5 SD) and TC at 1.00 log CFU/250 mL (0.0 SD). At 36 °C, the heterotrophic bacterial counts in mineral water samples from all wells were <1.0 log CFU/mL. However, at 22 °C, the samples from wells P-01, P-03, and P-04 showed average heterotrophic bacterial counts of 1.11 log (0.03 SD), 1.61 log (0.09 SD), and 1.30 log (0.02 SD) CFU/mL, respectively. The microbiota varied among the analyzed wells, indicating different microbial community profiles likely influenced by the soil microbiota rather than the physicochemical parameters of the well water samples.

Unravelling recharge mechanisms along the Guarani aquifer system (SAG) outcrop in southern Brazil

Unravelling recharge mechanisms along the Guarani aquifer system (SAG) outcrop in southern Brazil

THE GUARANI AQUIFER IN SANTA CATARINA

This is a study about the Guarani Aquifer in the state of Santa Catarina. Groundwater is a very important source both for its economic and social value. It is known that drinking water is an essential natural resource for the maintenance of life on the planet, but that it is becoming scarce due to factors such as irregular rains, climatic conditions, combined with population growth and irrational use. Thus, a bibliographic research is carried out in order to deepen the knowledge about the Guarani Aquifer System, its location and its use in that State. This study addresses: water as a precious liquid; groundwater and aquifer formation and more specifically the Guarani Aquifer its characteristics, uses and vulnerability and its connection with the Serra Geral Aquifer System in Santa Catarina. It also points out the importance of the involvement of the countries that are part of the Guarani Aquifer (Brazil, Paraguay, Argentina and Uruguay) in the search for more effective and controlled ways to use these transboundary waters.

Isotopes of nitrate and gadolinium fingerprints to assay human inputs in Guarani Aquifer System

The use of environmental tracers brings comprehensive benefits to the management of water resources since it helps to prevent their pollution, minimize public health risks, and thus reduce the impact of urbanization. In Brazil, the Guarani Aquifer System (GAS) has strategic and environmental importance, making its preservation and sustainable exploitation mandatory. The present study aimed at evaluating sources of contamination in the GAS using the combination of geochemical data and two environmental tracers: nitrate isotopes (15NNO3 and 18ONO3) and one rare earth element (Gadolinium-Gd). For that, five wells-four exploiting the GAS and one the Bauru Aquifer System (BAS)-were selected to discuss the human inputs in groundwater used for public supply in an urban area. Traditional physicochemical analyses were conducted for six campaign samplings and nitrate monitoring for this period was evaluated on a time scale, also considering the accumulated rainfall. Besides that, the double isotopic method (DIM), e.g., δ18ONO3 e δ15NNO3, was applied to identify the fractionation and enable the distinction of the nitrate contamination source. In addition, the determination of anomalies of Gd, a wastewater-derived contaminant, was also performed to verify recent human inputs in groundwater. The results show that the local existence of nitrate in the GAS and BAS-even at low concentrations (values from 0.26 to 6.68mg L-1)-originated from anthropogenic inputs (septic waste), as indicates the typical isotopic signals ratio in the isotopic approach. Associated with that, the evaluation of Gd permitted the separation of groundwater samples into older or more recent leakages. The use of environmental tracers to assess anthropogenic inputs in groundwater reiterates the importance of adopting more effective protection strategies for water resources management systems, in order to prevent contamination.

Assessment of River-Aquifer Interaction and Nitrogen Contamination in an Agricultural Zone Located in the Guarani Aquifer System Outcrop Area.

The excessive use of nitrogen fertilizers is responsible for an increase in nitrate concentrations in water bodies, which in the future could led to an irreversible contamination compromising the water resource quality. In this way, understand the water movement within a watershed and evaluate the impacts related to agricultural practices is relevant for water management, especially in an environmental fragile region, such as the outcrop area of the Guarani Aquifer. Water samples from a small watershed located at the Guarani Aquifer region in São Paulo state, representing surface water and groundwater discharge in riverbeds from two creeks, as well as groundwater (springs and wells) were collected for isotopic ratios (δ18O e δ2H) and nitrate determination. The results indicated that the river flow is mostly supplied by groundwater discharge, and despite the observed concentrations of nitrate in groundwater reaching the creeks, the current scenario indicate contamination in the surface water, above the regulatory levels. Therefore, the expansion in sugarcane production increases the possibility that the released nitrate reaches high levels in the future in this watershed.

Spectro-temporal analysis of anthropic interference in water production in the Guarani Aquifer

The Guarani Aquifer System is one of the largest freshwater reservoirs in the world and has been widely exploited due to the quantity and quality of the stored water. The outcropping areas are considered highly vulnerable, and anthropic interference can influence the recharge potential and cause changes in water quality. The purpose of this research was to spectrally and temporally analyze the anthropic interference in water production in the Guarani Aquifer in four distinct areas located in the outcrop and recharge areas located in the State of São Paulo, Brazil, from 2012 to 2018. Rainfall data were obtained using the CHIRPS dataset, and the actual evapotranspiration rate was obtained using the MODIS product. The lithology and piezometric level data were obtained through RIMAS of the Geological Service of Brazil. The piezometric level monitoring wells were used as a reference to delimit the study areas and the distance to eliminate overlapping spatial resolutions of the remote sensing products. The area bounded by the buffer is equivalent to 31,412 ha. The recharge was estimated with the ESPERE using the water table fluctuation method. The end classifications of land use were obtained using the normalized difference vegetation index through remote sensing data. The study area located in the municipality of Boa Esperança do Sul - SP had the largest area of exposed soil with a median of 2936 (ha) and the lowest recharge potential with a median of 338 mm/year. The study area located in the municipality of Bofete - SP had the smallest area of exposed soil with a median of 516 (ha) and the highest recharge potential with a median of 502 mm/year. The study area located in the municipality of Brotas - SP showed the lowest evapotranspiration rate, with a median of 639 mm/year. The municipality of São Simão - SP had the largest forest area, with a median of 18,009 ha. Although water resource policies have significantly influenced the valuation of groundwater, studies that assess changes in land use variables using time series analysis and evaluate how these changes influence water dynamics in the hydrological cycle are still lacking. The study aims to contribute technical support to the decision-making process of the National System of Water Resources Management (SINGREH) and State Law 9866/1997 to contribute to the sustainability of the Guarani Aquifer System.

Combined use of statistical Bayesian model and strontium isotopes deciphering the high complexity groundwater flow in the Guarani Aquifer System (GAS)

The Guarani Aquifer System (GAS) is one of the most important groundwater reservoirs in Latin America. Even though its geological aspects and hydraulic behavior are deeply studied, questions regarding hydraulic connections between the GAS and the overlying (SGAS) and underlying (PRE-GAS) aquifers within the Paraná Sedimentary Basin geological framework are recently being pursued. This paper presents a new tracer approach within the GAS, incorporating strontium isotopes in a statistical Bayesian model. The multi-pronged approach is used to quantify mixing proportions and identify different processes related to water-rock interaction and hydrochemical data. Strontium isotopic ratio ranged from enriched values (>0.711) associated with higher GAS groundwater contribution, to lower values associated with contribution from the SGAS (∼0.707) and PRE-GAS (∼0.709) units, as well as isotopic fingerprint associated with direct rainwater recharge. As groundwater flows through the GAS, the mixing proportions between the end-members changes along with the hydrogeochemical evolution. Near recharge zones, GAS represents the dominant source (38% ± 10%), followed by PRE-GAS (28% ± 16%), SGAS (19% ± 11%) and rainwater (14% ± 10%). In transition waters between outcrop and confined areas, the GAS contribution remains dominant (48% ± 9%), followed by PRE-GAS (37% ± 14%) and SGAS (14% ± 8%). In the GAS confined zone, where contributions from rainwater and SGAS is absent, 87Sr/86Sr ratio is more associated with waters from PRE-GAS (53% ± 16%) than from GAS (46% ± 16%). This behavior indicates that groundwater flow in the GAS represent a more complex and vulnerable groundwater mixing system, closely related to the regional geological context of a closed intracratonic basin, than previously understood. The use of strontium isotopes as a hydrogeochemical tracer applied in a statistical mixing model, contributes to a more refined understanding of regional groundwater flow and water origin in the GAS.

Unravelling groundwater and surface water sources in the Esteros del Iberá Wetland Area: An isotopic approach

In the Esteros del Iberá Wetland Area (EIWA, NE Argentina), the southern sector of the transboundary Guarani Aquifer System (SAG) is overlain by the Ramsar listed Iberá Wetlands and several rivers, that combined extend across 37,930 km2 and represent one of the largest freshwater systems on the South American continent. Previous hydrogeological studies encompassing the entire SAG proposed preferential discharge of groundwater of various origins and ages to the EIWA. In this study, a multi-tracer study using major ionic species, δ18O, δ2H and 222Rn was conducted in lagoons, rivers, wells, and boreholes in the EIWA to confirm if discharge from the transboundary SAG is contributing to the surface water system. End-member Mixing Analysis (EMMA) determined the existence of four main end-members: groundwater from the SAG, more saline groundwater from the deeper Pre-SAG, and two poorly mineralised end-members from shallow, Post-SAG. EMMA calculations clearly illustrated complex binary and ternary mixing patterns involving the four end-members and highlighted the role of geological structures, specifically regional steep faults, in controlling the mixing patterns. 222Rn activities allowed in-situ identification of preferential deep groundwater discharge into both surface waters and shallow groundwaters. These findings provide strong evidence for the widespread existence of upward flows along major faults in this sector of the SAG, inducing complex mixing flow patterns and explaining the presence of old groundwater in shallow aquifers. Mapping the sources of water and the hydrological interactions are relevant for improving water balance estimates and develop management policies towards the preservation of these wetlands.

The Ajuricaba Basin Creek chemical signature of water resources: Geological sources and anthropogenic contributions

The Ajuricaba Basin Creek is located west of the Parana State, it is part of the Parana 3 Hydrographic Basin and it is located at southwest of the Marechal Candido Rondon county. Its area of around 18 km2 is manly used for agricultural purposes. The basin is part of the Serra Geral Aquifer System (SGAS), which comprises basic volcanic rocks of the Serra Geral Group. The main objectives of this study are the characterization of the hydrogeochemical environments and the understanding of the dissolved elements sources, both geological and human, in order to create a water circulation model of the basin. Two field campaigns, in August and November 2019, were done to collect water samples from surface waters (SW), phreatic aquifer (PA) and fractured aquifer (FA). During the 2019 field campaigns, the temperature, pH, total dissolved solids (TDS) and electrical conductivity (EC) were measured on site. Physicochemical parameters (SiO2, HCO3−, CO3−2, Cl−, F−, PO4−3, SO4−2, NO3−, NO2−, Ca+2, Mg+2, Na+, K+, Fe total, Mn+2, Nb, S, V, Zn, Al, Sr, Ba, P, Ti) of the collected samples were analysed. Preexisting data from December 2010 was also used to observe historical changes in water quality through time. Based on this data, statistical (univariate and correlation) and hydrochemical analysis were conducted in order to characterize the hydrogeochemical environments and surface and groundwater flows in the basin. Historical analysis revealed that SW and PA samples have the most significant impacts on water quality with double the median concentration of NO3− and three to nine times the concentration of Cl−. Hydrochemical analysis showed that SW have higher concentrations of HCO3−, Cl−, NO3−, Ca+2, Mg+2, Al, Sr, Ba and Fe, high TDS and neutral to acid pH. PA has the lowest TDS and acid pH and its main ions are HCO3−, NO3−, Ca+2 and Mg+2. In addition, FA was divided in: FA (Ca+2) with HCO3−, Ca+2 and Mg+2 as main ions, neutral pH and low TDS and FA (Na+) with CO3−2, HCO3−, SO4−2, Na+, V, Nb and P as main ions, basic pH and high TDS. SW has a similar pattern to PA and FA (Ca+2) indicating that the rivers are discharge zones for both aquifers. FA (Ca+2) has a similar hydrochemical signature to SGAS, confirming it origins. In opposition, the FA (Na+) aquifer hydrochemical signature differs from the SGAS and, in fact, is more similar to the one of the confined Guarani Aquifer System (GAS), suggesting a higher residence time. Fa (Na+) waters have higher TDS and basic pH, indicating a higher residence time and depth associated with the ascension of even deeper flows from GAS towards the basin. In addition to the hydrochemical model, this research also highlights the potential of the multielement-hydrochemistry to understand the relations between surface and groundwater resources contributing for the management of water resources in watersheds.

Baseline of the outcropping Guarani Aquifer System in Rivera and Tacuarembó, Uruguay: Piezometry and Vulnerability

The piezometric, water table and vulnerability baseline of the outcropping Guaraní Aquifer System (GAS) in the departments of Rivera and Tacuarembó (Uruguay) is presented. The flow network and chemical composition are essential to understanding underground dynamics and identifying recharge and discharge zones, preferential flow directions, and determining hydraulic gradients. It is essential to analyze its evolution in time and space from the baseline, for the management and protection of the resource. Vulnerability was determined by applying the GOD and EKv methods, obtaining similar results, with areas of high and moderate vulnerability in most of the studied area. The risk of groundwater contamination was determined using the method of Foster &amp; Hirata(34), obtaining high risk for potentially polluting loads from lack of sanitation, solid household waste, irregular settlements, and gas stations, in areas of moderate and high vulnerability. Industrial and mining activity and a cemetery represent a moderate risk in most cases. Having maps of vulnerability and risk of groundwater contamination is essential to identify the most vulnerable areas and implement detailed study, control, and protection tools aimed at conserving and mitigating impacts on GAS.

Hydrogeochemical, Geophysical and Geological Assessment of the Recharge Zone of Guarani Aquifer System in Alegrete, southern Brazil

The state of Rio Grande do Sul has a huge part of the Guarani Aquifer, having a recharge area in its central and western region and, therefore, this investigation was focused on the city of Alegrete. There is no annual plan for water resources in the state and, hence, it is required to evaluate the hydrogeochemical, geophysical and geological characteristics where the aquifer has its recharge regions. Thus, some data were acquired, having chemical analysis of the water in different wells (mostly in rural areas) and refraction seismic and geoelectrical surveys. In addition, the geological information was obtained from the public database SIAGAS (Sistema de Informações de Águas Subterrâneas – ground water information system). Then, different maps of chemical parameters and a Piper diagram were made. Moreover, the refraction seismic and geoelectrical data were processed and interpreted, concatenating these results with the geological data obtained from the SIAGAS wells, mapping the different formations and static levels of the aquifer. A high concentration of lead, chromium and cadmium along with phosphate was found. Additionally, by means of geophysical surveys, a line was pointed out as a possible aquifer, which could be used for human, agropastoral or industrial activities after treatments of altered values.

Geophysical and geological surveys to understand the hydrogeological behavior in an outcrop area of the Guarani Aquifer System, in Brazil

In some Brazilian states, after the long period of drought in the years 2014 to 2015, the issue of water crises became the focus of several studies. Some of these studies propose the use of groundwater to avoid water crises. However, many of these do not understand or ignore the hydrological processes of aquifer recharge and discharge. Understanding the recharge and discharge processes is essential to prevent problems related to aquifers and better understand the exchange relationships between surface and underground reservoirs. Geophysical applications are used to study these hydrological processes of recharge and discharge, however there is a deficit regarding the use of the Electrorestivity method in this type of study. The present work delimited an area close to the escarpment of the Basaltic Cuesta front in the municipality of Ipeúna (SP). The objectives were to understand the recharge and discharge processes using the Electrical Resistivity Tomography (ERT) and a stratigraphic survey. The chosen area is in an outcrop area of the Guarani Aquifer System (GAS), a place known to be important in the recharge of this transboundary aquifer. The stratigraphic survey was carried out by walking along the access road to the study area. In the geophysical survey, 10 parallel lines of electrical resistivity tomography (ERT) were performed in Schlumberger array. The measured resistivity values ranged between 5000 Ω m and 20 Ω m. Data collected in the field were processed and represented in two-dimensional and three-dimensional logarithmic models. Through the correlation between stratigraphy and 2D models, it was possible to locate the porous and fractured aquifers, as well as to relate the resistivity values with the rocks present in the area. The 3D model provided a better visualization of the electrical resistivity values at different depths in the study area. In this way, it was possible to delimit the presence of water in the geological framework. The presence of water inside a large sandstone lens flowing towards the Cuesta front was identified. The geophysical and stratigraphy surveys provided information for the generation of a geological framework model, its relationship with groundwater flow and hydrological processes. The work also reduces the gap of geophysical studies in Guarani Aquifer System and the use of electrical resistivity tomography to understand the hydrological processes of aquifers.

Hydrogeochemical analysis, geophysical assessment and geological mapping of the recharge zone of the Guarani Aquifer system in Santa Cruz do Sul, Brazil

A large part of the Guarani Aquifer is in the state of Rio Grande do Sul (southern Brazil). Aquifer?s recharge area is in the central and western regions of the state. So, this work was focused on the municipality of Santa Cruz do Sul. Because there is no water resources plan in the state by 2022, the hydrogeochemical, geophysical properties, and geological characteristics of the aquifer recharge region were evaluated. Field data were gathered, including chemical analysis of water in different wells and geophysical surveys in refraction seismic and geoelectrical methods. In addition, geological information was obtained from the Groundwater Information System (SIAGAS) public database. The different chemical parameters were mapped to perceive some elements? concentrations in Santa Cruz do Sul according to the SIAGAS data. In addition, the seismic refraction data and geoelectric method were processed and interpreted, concatenating all these results with the geology obtained from SIAGAS wells. The existing formations and the static level of the Guarani Aquifer were mapped using geological data. A high concentration of lead in the region which is a possible aquifer was found using geophysical methods. If located in this area aquifer could be used for human, agropastoral, or industrial after treatments.

Identificação da interação rio-aquífero, por meio de gradientes de temperatura, em área de afloramento do Aquífero Guarani

ABSTRACT The use of temperature as a natural tracer in hydrology is noticed since the 1960s. In recent years, there has been a revival of the use of this physical property in the investigation of water cycle. The main reasons are the cost reduction of temperature measurements and the development of distributed temperature sensing. Here, we present a study of the groundwater-surface water interaction in the Onça Creek Watershed (Guarani Aquifer System outcrop) using stream discharge data and temperature as a natural tracer. Two Parshall flumes were installed 1.2 km apart to quantify stream discharge and determine groundwater contribution. We used an optic fiber cable to identify interaction locations and a probe with thermistors to measure the vertical temperature gradient and estimate flux rates. The results show a discharge difference of ~250 m3.h-1 between both flumes, which we interpret as baseflow contribution. The distributed temperature sensing allowed the identification of regions with gaining behavior. Discharge rates between 200 and 300 mm.day-1 were determined from vertical temperature measurements, which agrees with the streamflow data. The study demonstrated that temperature is attractive as natural tracer in tropical conditions, where the groundwater temperature is higher than the surface water temperature, especially during the winter.

Quantification of Carbon Cycling in a Large Aquifer Using Reactive Transport Modelling

Continental scale aquifers can store significant amounts of carbon as a result of immense water volumes, substantial concentrations of dissolved inorganic carbon (DIC) and its reactions with a matrix, thus contributing the global carbon storage and cycle. However, concentration of dissolved solutes may vary significantly over distances, which causes interpretative challenges and difficulties in process quantification. This occurs in the Guarani Aquifer System in South America, which is a subject of extensive research due to a significant strategic role in water supply. Dissolved CO2is expected to dissociate and undergo reactions with aluminosilicate minerals, but it is unknown how much DIC may get immobilised in the aquifer. To quantify the processes, we performed reactive transport modelling which combines hydrological and geochemical information followed by global sensitivity analysis. We show that more than a half of the infiltrated CO2may be consistently precipitated as CaCO3. The DIC concentrations across the aquifer depend primarily on the input carbon concentrations and the plagioclase hydrolysis rate, while other parameters including hydraulic conductivity, recharge rate and mineral stability are of the minor importance. We present how advanced modelling techniques may be used to interpret and quantify processes controlling water quality in continental scale groundwater systems.

Disposal of pharmaceuticals wastes by the population of an outcrop area of the Guarani Aquifer System in Southern Brazil

Pharmaceutical waste is considered emerging pollutant that can contaminate water sources and underground water, besides is serious problem for waste management in Brazil. The objective of this study was to evaluate the pharmaceutical consumption for human use and the way expired and unused medicines are disposed by the population. The study was carried out in two neighborhoods of the Lages, under outcrop of the Guarani Aquifer, in southern Brazil. In this descriptive and quantitative study, data collection occurred between August and October of 2018 via a questionnaire completed by 309 participants. The questions addressed about sociodemographic data, information on the medicine consumption, disposal of pharmaceuticals residue and about the basic sanitation in the neighborhood. The pharmaceuticals class most used were anti-hypertension and diuretics, indicating an elevated occurrence of non-transmittable chronic illnesses. About 68% of participants stated that there are leftovers of medications after medical treatment and 70.2% that there is expired medication at household. The disposal of leftover and expired pharmaceutical was in domestic waste, followed by discharged into domestic sewage. Only a small percentage (&lt;15%) of the participants adequately dispose of their medication waste. The inadequate disposal of household pharmaceutical in the study area can result in contamination by chemical substances of the Guarani Aquifer and superficial waters.