RESUMO

A hydro-geochemical characterization was conducted in the northern part of the Sonora River basin, covering an area of 9400 km2. Equipotential lines indicated that groundwater circulation coincided with the surface water flow direction. Based on the groundwater temperature measured (on average ∼21 °C), only one spring exhibited thermalism (51 °C). Electrical conductivity (160-1750 µS/cm), chloride and nitrate concentrations (>10 and >45 mg/L) imply highly ionized water and anthropogenic pollution. In the river network, δ18O values revealed a clear modern meteoric origin. Focused recharge occurred mainly from the riverbeds during the rainy season. During the dry season, diffuse recharge was characterized by complex return flows from irrigation, urban, agricultural, mining, and livestock. Drilled wells (>50 m) exhibited a strong meteoric origin from higher elevations during the rainy season with minimal hydrochemical anomalies. Our results contribute to the knowledge of mountain-front and mountain-block recharge processes in a semi-arid and human-altered landscape in northern Mexico, historically characterized by limited hydrogeological data.

Assuntos

RESUMO

Stable isotope ratios of nitrogen and oxygen (15N/14N and 18O/16O) of nitrate (NO3-) are excellent tracers for developing systematic understanding of sources, conversions, and deposition of reactive atmospheric nitrogen (Nr) in the environment. Despite recent analytical advances, standardized sampling of NO3-) isotopes in precipitation is still lacking. To advance atmospheric studies on Nr species, we propose best-practice guidelines for accurate and precise sampling and analysis of NO3- isotopes in precipitation based on the experience obtained from an international research project coordinated by the International Atomic Energy Agency (IAEA). The precipitation sampling and preservation strategies yielded a good agreement between the NO3- concentrations measured at the laboratories of 16 countries and at the IAEA. Compared to conventional methods (e.g., bacterial denitrification), we confirmed the accurate performance of the lower cost Ti(III) reduction method for isotope analyses (15N and 18O) of NO3- in precipitation samples. These isotopic data depict different origins and oxidation pathways of inorganic nitrogen. This work emphasized the capability of NO3- isotopes to assess the origin and atmospheric oxidation of Nr and outlined a pathway to improve laboratory capability and expertise at a global scale. The incorporation of other isotopes like 17O in Nr is recommended in future studies.

Assuntos

RESUMO

Bull shark (Carcharhinus leucas) is a near-threatened elasmobranch species capable of moving between the fresh and salty waters of tropical and subtropical coastal areas, for which we still lack important ecological information. During their first years of life, bull sharks use estuarine systems as nursery areas, making them highly susceptible to environmental and anthropogenic pressures. We studied the trophic ecology of juveniles found in the Coyote estuary, a potential nursery area in Costa Rica, to understand the potential impact of further bull shark declines and gain knowledge that could aid in their conservation. We analysed the trophic ecology of juvenile bull sharks [81-103 cm total length (TL)] in the Coyote estuary, Costa Rica, using stable isotopes of δ15 N and δ13 C. Since one problem using this technique in juveniles is the confounding effect of the maternal signature, we sampled different tissues (muscle and plasma), verified the status of the shark's umbilical scar and identified the size at which the isotope signature is a result of the animal's current diet. The isotopic values of the muscle tissue reflected the maternal isotopic signature. In contrast, plasma values reflected the diet of juvenile bull sharks >95 cm TL and with a closed umbilical scar. Juvenile bull sharks fed primarily on teleost fishes of the order Anguilliformes and Siluriformes, and have a high trophic position (≥4.0) in the Coyote estuary. Our findings suggest that this estuary is an important feeding site for juvenile bull sharks of the Pacific of Costa Rica. Thus, the protection of essential habitats such as the Coyote estuary will benefit not only bull shark conservation, but also the conservation of an array of fish species that also use this habitat as a rookery, many of which are of commercial interest.

Assuntos

RESUMO

Global bottled water consumption has largely increased (14.35 billion gallons in 2020) [1], [2], [3], [4], [5] during the last decade since consumers are demanding healthier and safer forms of rehydration. Bottled water sources are normally labeled as mountainous and pristine mineral springs (fed by rainfall and snow/glacier melting processes), deep groundwater wells or industrial purified water. The advent of numerous international and national-based bottled water brands has simultaneously raised a worldwide awareness related to the water source and chemical content traceability [6]. Here, we present the first database of stable isotope compositions and reported chemical concentrations from imported and national-based bottled waters in Costa Rica. In total, 45 bottled waters produced in Costa Rica and 31 imported from USA, Europe, Oceania, and other countries of Central America were analyzed for δ18O, δ2H, and d-excess. Chemical compositions were obtained from available bottle labels. National-based bottle waters ranged from -2.47‰ to -10.65‰ in δ18O and from -10.4‰ to -78.0‰ in δ2H, while d-excess varied from +4.2‰ up to +17.0‰. International bottle waters ranged between -2.21‰ and -11.03‰ in δ18O and from -11.3‰ up to -76.0‰ in δ2H, while d-excess varied from +5.0‰ up to +19.1‰. In Costa Rica, only 19% of the brands reported chemical parameters such as Na+, K+, Ca+2, Mg+2, F-, Cl-, NO3 -, SO4 -2, CO3 -2, SiO2, dry residue, and pH; whereas 27% of the international products reported similar parameters. The absence of specific geographic coordinates or water source origin limited a spatial analysis to validate bottled water isotope compositions versus available isoscapes in Costa Rica [7]. This database highlights the potential and relevance of the use of water stable isotope compositions to improve the traceability of bottled water sources and the urgent need of more robust legislation in order to provide detailed information (i.e., water source, chemical composition, purification processes) to the final consumers.

RESUMO

Increasing energy consumption and food production worldwide results in anthropogenic emissions of reactive nitrogen into the atmosphere. To date, however, little information is available on tropical urban environments where inorganic nitrogen is vastly transported and deposited through precipitation on terrestrial and aquatic ecosystems. To fill this gap, we present compositions of water stable isotopes in precipitation and atmospheric nitrate (δ18O-H2O, δ2H-H2O, δ15N-NO3-, and δ18O-NO3-) collected daily between August 2018 and November 2019 in a tropical urban atmosphere of central Costa Rica. Rainfall generation processes (convective and stratiform rainfall fractions) were identified using stable isotopes in precipitation coupled with air mass back trajectory analysis. A Bayesian isotope mixing model using δ15N-NO3- compositions and corrected for potential 15N fractionation effects revealed the contribution of lightning (25.9 ± 7.1%), biomass burning (21.8 ± 6.6%), gasoline (19.1 ± 6.4%), diesel (18.4 ± 6.0%), and soil biogenic emissions (15.0 ± 2.6%) to nitrate wet deposition. δ18O-NO3- values reflect the oxidation of NOx sources via the ·OH + RO2 pathways. These findings provide necessary baseline information about the combination of water and nitrogen stable isotopes with atmospheric chemistry and hydrometeorological techniques to better understand wet deposition processes and to characterize the origin and magnitude of inorganic nitrogen loadings in tropical regions.

Assuntos

RESUMO

The Corumbataí River basin (São Paulo, Brazil) has a critical situation regarding water availability due to the intensive use to support agriculture and urbanization, requiring scientific information to face water demand. The aim of this study is to present a hydrological characterization based on the analysis of seasonal isotope variations (rainfall, groundwater, and surface water) and hydrometric data. Results indicate that baseflow contribution varies from 50 % to 70 % of the total flow, and water isotopic composition denotes a seasonal regime marked by the mixing of surface and groundwater in the wet period and groundwater discharge during the dry season. The results presented indicated the strong seasonal connection between atmospheric inputs and water movement across the basin, which poses an urgent need to diversify monitoring methods and create feasible regional and political regulations to control the effects on basin water resilience in the face of climate change and growing demand.

Assuntos

RESUMO

The Chaco-Pampean Plain (Argentina) is the strongest economic region and the most inhabited in the country, comprising approximately 66% of the country's population (26,500 million) [1]. In this region, surface slopes are very low (<0.1%) and due to the current climatological features, floods and droughts alternate over time. Salinity and alkalinity of water and soil increase towards the flattest sector of the basin, as well as the contents of arsenic and fluoride, which restrict their human use. Worldwide, population growth and global warming, in addition to political decisions, are leading to abrupt land use changes. Under this premise, identifying and quantifying the hydrological processes that control water quantity and its chemical quality become an imperative task [2]. This data article provides a long-term hydrological dataset from a sector of the Chaco-Pampean Plain, the Del Azul creek basin. Hydrological data such as flow rates and piezometric levels, and physical-chemical (i.e., major and minor solutes, and trace elements) and isotopic (δ18O, δ2H; and d-excess) data from rainwater, surface (creek and wetland) and groundwater (at two depths) are available. Rainwater samples are derived from three precipitation collectors installed at different altitudes (monitoring period: 2010-2019; n = 57). Surface water samples were collected at three sampling sites located along the Del Azul Creek and six wetlands (monitoring period: 2018-2019; n = 12). Groundwater samples were collected from 17 piezometers with depths ranging between 3 and 10 m, and from 12 piezometers of 30 m depth, all located throughout the entire basin (monitoring period: 2018-2019; n = 115). Sampling campaigns were performed during the austral dry (summer) and wet (spring) seasons. This dataset provides useful information to understand a) how water moves from recharge to discharge areas, b) how water acquires salinity, and c) how particular solutes of concern, such as arsenic and fluoride, are distributed in space and time across in an extensive plain.

RESUMO

Water use by anthropogenic activities in the face of climate change invokes a better understanding of headwater sources and lowland urban water allocations. Here, we constrained a Bayesian mixing model with stable isotope data (2018-2019) in rainfall (N = 704), spring water (N = 96), and surface water (N = 94) with seasonal isotope sampling (wet and dry seasons) of an urban aqueduct (N = 215) in the Central Valley of Costa Rica. Low δ 18O rainfall compositions corresponded to the western boundary of the study area, whereas high values were reported to the northeastern limit, reflecting the influence of moisture transport from the Caribbean domain coupled with strong orographic effects over the Pacific slope. The latter is well-depicted in the relative rainfall contributions (west versus east) in two headwater systems: (a) spring (68.7 ± 3.4 %, west domain) and (b) stream (55.8 ± 3.9 %, east domain). The aqueduct exhibited a spatial predominance of spring water and surface water during a normal wet season (78.7 %), whereas deep groundwater and spring water were fundamental sources for the aqueduct in the dry season (69.4 %). Our tracer-based methodology can help improve aqueduct management practices in changing climate, including optimal water allocation and reduced evaporative losses in the dry season.

Assuntos

RESUMO

This work presents a weekly carbon isotope composition analysis (June 2017-January 2018) of carbon dioxide (CO2) and methane (CH4) in a tropical urban atmosphere (Central Valley, Costa Rica). δ13C values of CO2 and CH4 ranged from -12.2 to -5.9 ‰, and from -51.6 to -46.3 ‰, respectively. Mixing ratios of CO2 and CH4 varied from 384.2 to 528.5 ppmv, and from 1.860 to 2.613 ppmv, respectively. δ13C spatial variation and mixing ratios of CO2 and CH4 were influenced by the atmospheric stability and air circulation patterns in the metropolitan area. Low δ13C values and large mixing ratios were observed in the southwestern area of the valley during the rainiest period (September-November). Preliminary linear relationships between reciprocal CO2 mixing ratios and δ13C values indicate that CO2 emissions in the Central Valley are probably related to respiration processes and fossil fuel combustion, although CO2 enriched in 13C from volcanic degassing was also detected. Under stable atmospheric conditions, CH4 data seems to reflect the influence of emissions near the sampling sites. These preliminary results based on the carbon isotope technique demonstrate potential for carrying out atmospheric studies at tropical urban locations with different terrain characteristics and atmospheric mixing conditions.

Assuntos

RESUMO

Under a changing climate, projections estimate that over the next thirty years, extreme Tropical Cyclones (TCs) will increase in frequency, with two to three times more Category 4 and 5 hurricanes in the Atlantic basin between 20°N and 40°N. In recent years, the Caribbean Sea and Atlantic Ocean basins have experienced several extreme TCs, resulting in extensive human, ecological, and economic damage [1], [2], [3]. To improve understanding of TCs and their potential impacts in the face of climate change, physically based understanding of past climate and modern TC dynamics is necessary. Despite the well-known Atlantic hurricane season, surface observations of the isotopic evolution of TC's moisture and the propagation of isotopically distinct pulses across surface and subsurface water reservoirs are lacking. In this data article, we provide novel high frequency sampling of surface rainfall isotope compositions (δ18O, δ2H, and d-excess in ‰) for Hurricanes Otto (Costa Rica, 2016), Nate (Costa Rica, 2017), Irma (Cuba and The Bahamas, 2017), Maria (Cuba and The Bahamas, 2017), and Dorian (The Bahamas, 2019). These five TCs were characterized by unprecedented impacts during continental and maritime landfalls and passages. In total, 161 surface rainfall samples were collected in passive devices [4] with event-based and daily frequencies, resulting in the first surface isotopic tempestology anatomy across the Caribbean Sea and Atlantic Ocean basins to date. Derived rainfall from TCs often results in large input amounts of isotopically distinct water over an area from few hours to several days, and therefore this unique isotope composition is propagated through surface and shallow subsurface reservoirs. Our data also include spring (N=338) and surface water (N=334) isotope compositions following the impact of Hurricane Otto and Tropical Storm Nate in central Costa Rica. As this region is well-known for its diverse rainfall dynamics and as a climate change 'hot spot' [5], [6], [7], our data provide an opportunity to improve and complement modern and past climate interpretations often derived from satellite products and calcite-δ18O paleoclimatic archives in light of climatic forcing, TC rainfall amounts and recharge rates, and the hypothesized climatic-induced decline of past Mesoamerican civilizations.