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1.
Ecotoxicol Environ Saf ; 208: 111779, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396090

RESUMO

High levels of ammonium in groundwater is a potential threat to drinking water security and ecological status. The role of dissolved organic matter (DOM) in mobilization of natural ammonium in groundwater is crucial but the intrinsic link between them has still been poorly understood. This study used high-pressure size exclusion chromatography (HPSEC) and fluorescence excitataion-emission-matrix spectra (EEMs) with parallel factor analysis (PARAFAC) to elucidate the influence of DOM characteristics in groundwater systems having contrastive ammonium levels in Dongting Plain, central Yangtze River. The results indicate that NH4+-N concentration in groundwater of western plain (0-16.75 mg/L) are much higher compared with southern plain (0-1.5 mg/L). The groundwater in western plain is in a more reductive environment and characterized by larger molecular weight (MW) of DOM and lower polydispersity (ρ), whereas DOM with relatively small molecular weight and high polydispersity is detected in the south with a more oxidative condition. The groundwater in western plain is characterized by lower fluorescence index (f450/500) and biological index (BIX), and dominated by the high molecular weight terrestrial humic-like component and larger amounts of microbial humic-like components. Protein-like is the main component in groundwater of southern plain with higher f450/500 and BIX. The ammonium concentration in groundwater correlates well with molecular weight and increases significantly with the content of high molecular weight terrestrial humic-like component, indicating that mobilization of ammonium is more closely associated with the terrestrial organic matter of high molecular weight. This study further enriches the theory on mobilization of ammonium in Quaternary alluvial-lacustrine aquifer systems and provides theoretical basis for the local water supply security.


Assuntos
Compostos de Amônio/análise , Água Subterrânea/química , Rios/química , China , Monitoramento Ambiental , Análise Fatorial , Fluorescência , Espectrometria de Fluorescência
2.
Ecotoxicol Environ Saf ; 208: 111548, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396092

RESUMO

In order to understand the pollution status of groundwater with geochemical evolution and appraisal of its probable public health risk due to nitrate (NO3-) and fluoride (F-), a total of 93 groundwater samples were collected during pre-monsoon (May) period from Wardha sub-basin, central India. By employing Piper plot, transition from Ca-HCO3 type water (recharge waters) to Na-Cl (saline water) type water through mixed Ca-Na-HCO3, mixed Ca-Mg-Cl (reverse ion exchange waters) and Ca-Cl types (leachate waters), were observed. The Geogenic processes such as silicate, dolomite, halite and carbonate weathering along with calcite precipitation and ion exchange process were identified as major controlling factors for evolution and alteration of groundwater chemistry. The Saturation index highlighted that the groundwater in the area is oversaturated with respect to the mineral calcite and dolomite, and under saturated with gypsum, fluorite and halite. The high NO3- and F- concentration overpassing the permissible limit were found in 54.8% and 18.5% of samples. The plot of F- with Na+/Ca2+, Na+/Mg2+ and F-/Cl- established fluoride bearing rock weathering is responsible for F- contamination. Based on the cluster analysis, the groundwater was grouped into Cluster-I Ca-Na-HCO3 type (61.3%) and Cluster-II Na-Ca-HCO3-Cl type (30.1%). The total hazard index (HI) based on human health risk assessment (HHRA) model for cumulative NO3- and F- toxicity through oral and dermal pathways were computed as 100%, 97.85% and 96.77% for children, female and male populations respectively. The HQ(nitrate) > 1 through ingestion pathway were in 84.95%, 68.82% and 62.37%, and HQ(fluoride) > 1 in 83.87%, 62.37% and 43.01% of the groundwater samples were recorded for children, female and male population respectively. The risk assessment study highlighted very high toxicity and severe health impact of ingestion of contaminated groundwater on public health.


Assuntos
Monitoramento Ambiental , Fluoretos/toxicidade , Nitratos/toxicidade , Poluentes Químicos da Água/toxicidade , Carbonato de Cálcio , Carbonatos , Criança , Feminino , Fluoretos/análise , Água Subterrânea/análise , Água Subterrânea/química , Humanos , Índia , Troca Iônica , Magnésio , Nitratos/análise , Medição de Risco , Poluentes Químicos da Água/análise
3.
Ecotoxicol Environ Saf ; 208: 111478, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33091775

RESUMO

Metal-reducing bacteria play an important role in the release and mobilization of arsenic from sediments into groundwater. This study aimed to investigate the influence of nitrate on arsenic bio-release. Microcosm experiments consisting of high arsenic sediments and indigenous bacterium Bacillus sp. D2201 were conducted and the effects of nitrate on the mobilization of As/Fe determined. The results show arsenic release is triggered by iron reduction, which is regulated by nitrate. Increasing the nitrate concentration from 0 to 1 and 3 mM decreased Fe(III) reduction by 62.5% and 16.9% and decreased As(V) bio-release by 41.5% and 85.5%, respectively. Moreover, the results of step-wise Wenzel sequential extractions indicate nitrate addition prevents the transformation of poorly crystalline iron oxides to well crystalline iron oxides. Overall, nitrate appears to have a dual effect, inhibiting both iron reduction and arsenic release by incubation strain D2201. This study offers new insights regarding the biogeochemistry of arsenic in groundwater systems.


Assuntos
Arsênico/metabolismo , Bactérias/metabolismo , Ferro/metabolismo , Nitratos/metabolismo , Biodegradação Ambiental , Compostos Férricos/metabolismo , Sedimentos Geológicos/química , Água Subterrânea/química , Ferro/química , Nitratos/análise , Oxirredução
4.
Ecotoxicol Environ Saf ; 207: 111245, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32956896

RESUMO

Access to safe drinking water is one of the fundamental human rights and an important part of healthy living. This study considered various land use methods, used geostatistical analysis, and triangular random model to explore nitrogen pollution and estimate its potential risk to human health for local populations in Songnen Plain of Northeast China and recognize parameter uncertainties. Nitrate concentrations in groundwater ranged from 0.01 to 523.45 mg/L, more than 72.35% of the samples exceeded Grade III threshold (20 mg/L of N) as per China's standard, and nitrate nitrogen content is greater than 20 mg/L accounted for around 60% of the research area, mainly distributed in the eastern and central high plain area. The nitrate-nitrogen content of groundwater in the town land was significantly higher than that of agricultural land, and the ammonia nitrogen content was conversely. The townland's risk value was two times that of agricultural land, considering different land use methods would avoid overestimating or underestimating regional risk value. Non-carcinogenic risks (HI) of two land use were above the safety level (i.e., HI > 1), suggesting that groundwater nitrate would have significant health effects on the age groups, and further threaten children. There was a wide range of fluctuations in the uncertainty of nitrogen concentration and model evaluation parameters; triangular random model was more sensitive to data changes, which could reduce the uncertainty. The contribution rate of nitrate-nitrogen concentration to risk was above 90%, which explained the need for random sampling to improve the evaluation results reliability. The findings in this paper will provide new insight for solving uncertainties in water safety management.


Assuntos
Exposição Ambiental/estatística & dados numéricos , Água Subterrânea/química , Nitrogênio/análise , Poluentes Químicos da Água/análise , Agricultura , Amônia/análise , China , Cidades , Poluição Ambiental/análise , Humanos , Nitratos/análise , Óxidos de Nitrogênio/análise , Reprodutibilidade dos Testes , Medição de Risco/métodos , Água/análise , Abastecimento de Água
5.
Chemosphere ; 262: 128352, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182087

RESUMO

As organic pollution of soil and groundwater increases, the effective and economical remediation of contaminated sites has drawn growing attention. In this study, running-water (RW) was designed to modify alkali-heat/persulfate (MAH/PS) for integrated remediation of an actual organic-contaminated site. The degradation efficiency mainly reached 60%-99% for Benz[a]anthracene, Benzo[a]pyrene and total petroleum hydrocarbons (TPHs). MAH/PS was more effective in degrading Benzene and 1,2-Dichloroethane with simple molecular configurations. The pollutant degradation efficiencies decreased with increasing site depth and increased with increasing pollutant concentrations. Migration with RW enhanced site remediation. By monitoring the groundwater after remediation, it was found that residual TPHs presented anomalous diffusion; SO42- ranged from 8.00 to 237.00 mg L-1 to 8.00-290.00 mg L-1 and pH presented alkalescence (7.00-8.20). Mathematical models were established to describe the reaction process including the solubility equilibrium of calcium hydroxide, temperature equilibrium, and reaction kinetics. Moreover, MAH/PS provided a cost-saving approach for site remediation.


Assuntos
Recuperação e Remediação Ambiental/métodos , Poluentes do Solo/análise , Poluentes do Solo/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Álcalis , Benzo(a)pireno/química , China , Água Subterrânea/análise , Água Subterrânea/química , Temperatura Alta , Hidrocarbonetos/química , Modelos Teóricos , Oxirredução , Petróleo/análise , Poluição por Petróleo , Solo/química , Sulfatos/química
6.
Chemosphere ; 262: 127707, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32755691

RESUMO

The corrosion mechanisms of nanoscale zero-valent iron (nZVI) vary with different geochemical constituents, which affect the reductive dechlorination process of trichloroethylene (TCE). In this study, the effect of nZVI anaerobic corrosion on the reductive dechlorination of TCE with different groundwater geochemical constituents (Ca2+-SO42-, Ca2+-HCO3-, Na+-NO3-) was investigated. Microscopic characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM) combined with pH, oxidation-reduction potential (ORP) and dissolved Fe2+ in solutions to illustrate the corrosion mechanism of nZVI. In the four systems including ultrapure water (UPW), the reduction of TCE conformed to pseudo-first-order kinetics, the generation of Cl- accorded with zero-order kinetics, and multi-step reaction kinetics was used to fit the generation and degradation of chlorinated byproducts (Dichloroethylene, DCEs). Compared with UPW system, the dissolution corrosion of Ca2+-HCO3- and Ca2+-SO42- promoted the reductive dechlorination of TCE (kobs, TCE = 0.658 ± 0.010 & 0.245 ± 0.028 d-1 and kobs, Cl- = 41.682 ± 1.016 & 20.623 ± 1.923 µM⋅d-1 for Ca2+-HCO3- & Ca2+-SO42-, respectively) and the degradation of DCEs (0.444 ± 0.036 & 0.244 ± 0.040 µM⋅d-1 for Ca2+-HCO3- & Ca2+-SO42-, respectively); redox-active NO3- competed for electrons and passivated the surface of nZVI, which limited the reductive dechlorination of TCE (kobs, TCE = 0.111 ± 0.025 d-1 & kobs, Cl- = 14.943 ± 0.664 µM⋅d-1) and the degradation of DCEs (0.078 ± 0.018 µM⋅d-1), and the passivation layer promoted the adsorption of TCE. This study from the perspective of nZVI corrosion provides a theoretical basis for the long-term application of nZVI technology in the remediation of TCE-contaminated sites with different groundwater geochemical types.


Assuntos
Água Subterrânea/química , Ferro/química , Tricloroetileno/química , Poluentes Químicos da Água/química , Adsorção , Anaerobiose , Corrosão , Dicloroetilenos/química , Halogenação , Concentração de Íons de Hidrogênio , Cinética , Microscopia Eletrônica de Transmissão , Oxirredução , Purificação da Água/métodos , Difração de Raios X
7.
Ecotoxicol Environ Saf ; 207: 111512, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33254392

RESUMO

This study investigated 324 groundwater samples collected from the southwest plain of Shandong Province during the dry and wet seasons. Groundwater fluoride in the study area and the influencing factors were characterized and discussed using statistical analysis, ion ratios, Piper diagrams, the saturation index (SI) and ArcGIS software. In addition, the risk posed by groundwater fluoride to human health was assessed. The results showed that groundwater in the study area had elevated fluoride concentrations, with average dry and wet season concentrations of 1.15 mg·L-1 and 1.08 mg·L-1, respectively. Groundwater fluoride showed consistent spatial variations during the dry and wet seasons, with a significant regionalization pattern of low concentrations in the east and high concentrations in the west. Groundwater F- was significantly negatively correlated with Ca2+ and positively correlated with pH, HCO3- and Na+. Important factors identified as having an effect on groundwater F- in the study area included the balance of dissolution of fluorite and calcite, the weakly alkaline environment and cation exchange. In addition, hydrochemical types of high-fluoride groundwater in the study area were identified as mainly HCO3-Na and SO4·Cl-Na. The assessment of the risk of high groundwater fluoride to human health showed that children are more at risk compared to adults, with the risk during the dry season exceeding that over the wet season. It is recommended that water quality management in the study area prioritize the formulation of measures to mitigate high concentrations of fluoride in groundwater .


Assuntos
Monitoramento Ambiental , Fluoretos/análise , Poluentes Químicos da Água/análise , Adulto , Carbonato de Cálcio/química , Criança , China , Água Subterrânea/química , Saúde , Humanos , Minerais/análise , Sódio/análise , Qualidade da Água
8.
Environ Health Perspect ; 128(10): 107010, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-33124919

RESUMO

BACKGROUND: Groundwater is a main drinking-water source for Chinese rural residents. The overall pollution status of organic micropollutants (OMPs) and metals in the groundwater and corresponding health risks are unknown. OBJECTIVES: Our objective was to comprehensively screen for and assess the health risks of OMPs and metals in groundwater of rural areas in China where groundwater is used for drinking so as to provide a benchmark for monitoring and improving groundwater quality in future developments. METHODS: One hundred sixty-six groundwater samples were collected in the rural areas of China, and 1,300 OMPs and 25 metals were screened by GC-MS, LC-QTOF/MS, and ICP-MS analysis. To assess the noncarcinogenic and carcinogenic risks of the detected pollutants, missing toxicity threshold values were extrapolated from existing databases or predicted by quantitative structure-activity relationship (QSAR) models. Monte Carlo simulation was performed to account for uncertainties in the exposure parameters and toxicity thresholds. RESULTS: Two hundred thirty-three OMPs and 25 metals were detected from the 166 samples. The concentration summation for the detected OMPs ranged from 2.9 to 1.7×105ng/L among the different sampling sites. Cumulative noncarcinogenic risks for the OMPs were estimated to be negligible. However, high metal risks were calculated in 23% of the sites. Forty-two carcinogens (including 38 OMPs) were identified and the cumulative carcinogenic risks in 34% of the sites were calculated to be >10-4 (i.e., one excess cancer case in a population of 10 thousand people). The carcinogenic risks were estimated to be mainly associated with exposures to the metals, which were calculated to contribute 79% (0-100%) of the cumulative carcinogenic risks. DISCUSSION: The overall status of OMPs and metals pollution in the groundwater and the corresponding health risks were determined preliminarily, which may provide a benchmark for future efforts in China to ensure the safety of drinking water for the local residents in rural areas. The joint application of QSARs and Monte Carlo simulation provided a feasible way to comprehensively assess the health risks of the large and ever-increasing number of pollutants detected in the aquatic environment. https://doi.org/10.1289/EHP6483.


Assuntos
Exposição Ambiental/estatística & dados numéricos , Monitoramento Ambiental , Metais/análise , Poluentes Químicos da Água/análise , China , Água Potável/química , Água Subterrânea/química , Humanos , Medição de Risco
9.
Bull Environ Contam Toxicol ; 105(5): 758-763, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33068117

RESUMO

Cenotes are naturally occurring flooded caves that are frequent in Mexico's Yucatan Peninsula; they result from the collapse of limestone bedrock into the regional groundwater table. Cenotes in Quintana Roo are important ecological and economic hot spots but are susceptible to anthropogenic pollution. In this study, we collected water samples from 11 cenotes over multiple years to evaluate polycyclic aromatic hydrocarbon (PAH) concentrations and patterns as associated with tourist traffic. The primary PAHs detected in samples included fluoranthene, anthracene, phenanthrene and naphthalene, with total PAH concentrations increasing almost fivefold for cenotes sampled from 2016 to 2017. This is compared to only a 7% increase in tourist traffic during these years. Multivariate statistical analysis of the PAH concentration data suggests that diesel, gasoline and asphalt are the most likely pollution sources and that they are associated with periods of increased tourist traffic.


Assuntos
Monitoramento Ambiental/métodos , Poluição Ambiental/análise , Água Subterrânea/química , Hidrocarbonetos Policíclicos Aromáticos/análise , Poluentes Químicos da Água/análise , Região do Caribe , México , Análise de Componente Principal
10.
Chemosphere ; 261: 128078, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33113667

RESUMO

Per- and polyfluoroalkyl substances (PFAS) are used in a wide variety of consumer products, including ski waxes, and are widespread persistent and hazardous environmental contaminants. We examined the environmental impact of ski wax use at an outdoor recreation area with significant cross-country ski activity by measuring PFAS levels in melted snow, soil and water following a collegiate ski race. We found extremely high levels of long- and short-chain PFAS (C4-C14) contamination in snow at the race start line (∑[PFAS] 7600-10,700 ng/L), with the longer-chain analytes (C10-C14) predominating. The complement of 14 PFAS detected in snow matched what has been found in ski wax. This snow contamination was greatly reduced at a point 3.9 km into the race. Soil at the start line contained the four most predominant PFAS in snow at a mean individual concentration of 2.81 ng/g dry weight. Control soil contained only perfluorooctane sulfonic acid (PFOS), not found in other soil samples, at a concentration of 2.80 ng/g. Shallow groundwater from an on-site well contained only the shorter-chain PFAS (C4-C8), with a mean individual concentration of 4.95 ng/L. Our results suggest that ski wax use, from which fluorocarbons abrade at very high levels onto snow during a ski race, are the main source of PFAS contamination at our site. Regulation of ski wax use is warranted to reduce PFAS pollution.


Assuntos
Ácidos Alcanossulfônicos/análise , Monitoramento Ambiental/métodos , Poluição Ambiental/análise , Fluorcarbonetos/análise , Lubrificantes/química , Poluentes Químicos da Água/análise , Água Subterrânea/química , Maine , Esqui , Neve/química , Solo/química , Ceras
11.
Ecotoxicol Environ Saf ; 206: 111217, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32882574

RESUMO

Groundwater is an important resource for drinking and irrigation purposes and also the significant route of human exposure in most of the arid and semi-arid regions of the world. In view of this, 43 groundwater samples were collected and analyzed for various physico-chemical parameters. Particularly, this study integrates the groundwater contamination by comparing it to national guidelines and the impact of fluoride and nitrate on health risk were quantified through the model recommended by the United States Environmental Protection Agency (USEPA). The groundwater of the investigated region is slightly alkaline in nature with hydrochemical facies of groundwater is predominantly characterized by Ca2+-Mg2+-HCO3- and Ca2+-Mg2+-Cl- water types. The results show that the concentrations of groundwater nitrate and fluoride range from 2.2 to 165 mg/L and 0.84 to 4.3 mg/L, and 55.81% and 65% of groundwater exceed the national guidelines for drinking purposes, respectively. The pollution index of the groundwater (PIG) method unveiled that low quality and moderate quality of water account for 40% and 4.65% of collected groundwater samples, respectively. The results of non-carcinogenic health risk ranged from 0.63 to 5.31 ± 2.59 for adults, 0.85 to 7.18 ± 3.50 for children and 0.98 to 8.29 ± 4.04 for infants, indicating health risk was higher in infants and children as compared to the adults in the study region.


Assuntos
Monitoramento Ambiental/métodos , Fluoretos/análise , Água Subterrânea/química , Nitratos/análise , Poluentes Químicos da Água/análise , Qualidade da Água/normas , Adulto , Criança , Humanos , Índia , Lactente , Medição de Risco
12.
Chemosphere ; 254: 126859, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957279

RESUMO

Understanding the long-term fate, stability, and bioavailability of uranium (U) in the environment is important for the management of nuclear legacy sites and radioactive wastes. Analysis of U behavior at natural analogue sites permits evaluation of U biogeochemistry under conditions more representative of long-term equilibrium. Here, we have used bulk geochemical and microbial community analysis of soils, coupled with X-ray absorption spectroscopy and µ-focus X-ray fluorescence mapping, to gain a mechanistic understanding of the fate of U transported into an organic-rich soil from a pitchblende vein at the UK Needle's Eye Natural Analogue site. U is highly enriched in the Needle's Eye soils (∼1600 mg kg-1). We show that this enrichment is largely controlled by U(VI) complexation with soil organic matter and not U(VI) bioreduction. Instead, organic-associated U(VI) seems to remain stable under microbially-mediated Fe(III)-reducing conditions. U(IV) (as non-crystalline U(IV)) was only observed at greater depths at the site (>25 cm); the soil here was comparatively mineral-rich, organic-poor, and sulfate-reducing/methanogenic. Furthermore, nanocrystalline UO2, an alternative product of U(VI) reduction in soils, was not observed at the site, and U did not appear to be associated with Fe-bearing minerals. Organic-rich soils appear to have the potential to impede U groundwater transport, irrespective of ambient redox conditions.


Assuntos
Água Subterrânea/química , Resíduos Radioativos/análise , Solo/química , Urânio/análise , Poluentes Radioativos da Água/análise , Compostos Férricos , Microbiologia do Solo , Urânio/química , Compostos de Urânio/análise , Espectroscopia por Absorção de Raios X
13.
PLoS One ; 15(9): e0232437, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32986713

RESUMO

Subsurface microbial communities mediate the transformation and fate of redox sensitive materials including organic matter, metals and radionuclides. Few studies have explored how changing geochemical conditions influence the composition of groundwater microbial communities over time. We temporally monitored alterations in abiotic forces on microbial community structure using 1L in-field bioreactors receiving background and contaminated groundwater at the Oak Ridge Reservation, TN. Planktonic and biofilm microbial communities were initialized with background water for 4 days to establish communities in triplicate control reactors and triplicate test reactors and then fed filtered water for 14 days. On day 18, three reactors were switched to receive filtered groundwater from a contaminated well, enriched in total dissolved solids relative to the background site, particularly chloride, nitrate, uranium, and sulfate. Biological and geochemical data were collected throughout the experiment, including planktonic and biofilm DNA for 16S rRNA amplicon sequencing, cell counts, total protein, anions, cations, trace metals, organic acids, bicarbonate, pH, Eh, DO, and conductivity. We observed significant shifts in both planktonic and biofilm microbial communities receiving contaminated water. This included a loss of rare taxa, especially amongst members of the Bacteroidetes, Acidobacteria, Chloroflexi, and Betaproteobacteria, but enrichment in the Fe- and nitrate- reducing Ferribacterium and parasitic Bdellovibrio. These shifted communities were more similar to the contaminated well community, suggesting that geochemical forces substantially influence microbial community diversity and structure. These influences can only be captured through such comprehensive temporal studies, which also enable more robust and accurate predictive models to be developed.


Assuntos
Bactérias , Sedimentos Geológicos/microbiologia , Água Subterrânea/química , Metais Pesados/análise , Microbiota , Microbiologia do Solo , Bactérias/classificação , Bactérias/crescimento & desenvolvimento , Biofilmes , Reatores Biológicos/microbiologia , Filogenia , RNA Ribossômico 16S/genética
14.
Isotopes Environ Health Stud ; 56(5-6): 673-683, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32876495

RESUMO

This work applied environmental isotope techniques to validate the results of previous studies on recharge sources in a rural area in central Chile (34.3° S and 71.3° W) and discern the origin of nitrate contamination in wells. Stream water and groundwater samples were taken during three surveys, two during spring snowmelt and one in low-water conditions. Chemical analyses included major cations and anions, isotope analyses included 18O-H2O; 2H-H20; 3H-H20; 18O-NO3 - and 15N-NO3 -. The stable isotope data show that surface water and deep groundwater present depleted isotope values associated with recharge from the Andes Mountains and that shallow groundwater has more enriched isotope values that reflect the contribution of local recharge from rainwater infiltration. Depleted isotope values observed in shallow groundwater show the effect of recirculated river water used for irrigation. These results are consistent with the conceptual groundwater model developed in previous studies. Some wells have nitrate concentrations above the allowable limit for drinking water. The stable nitrogen isotopes indicate that nitrate is associated mainly with urea and ammoniacal fertilizers, and nitrate is attenuated by denitrification. The results of this study are relevant to improving management of groundwater resources used for drinking water.


Assuntos
Monitoramento Ambiental/métodos , Água Subterrânea/química , Nitratos/análise , Isótopos de Nitrogênio/análise , Rios/química , Poluentes Químicos da Água/análise , Agricultura , Chile , Água Potável/normas , Fertilizantes/análise , Estações do Ano , Ciclo Hidrológico , Poços de Água
15.
Isotopes Environ Health Stud ; 56(5-6): 533-550, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32893685

RESUMO

The Guaraní Aquifer System (SAG) is the largest transboundary aquifer in Latin America, extending beneath parts of Brazil, Paraguay, Argentina, and Uruguay. This paper presents the results of recent hydrogeological studies in the southern portion of the SAG. Locally, the abundance of surface water bodies precluded the use of conventional hydrological tools to characterize groundwater flows. Geological, hydrochemical and environmental isotope investigations were integrated to postulate a revised hydrogeological conceptual model. The revised geological model has provided a better definition of the geometry of the aquifer units and outlined the relevance of regional faults in controlling flow patterns. The new potentiometric map is consistent with groundwater flow from the SAG outcrops to the centre of the Corrientes Province, where upwards flows were identified. Hydrochemical and isotope data confirmed the widespread occurrence of mixing. Noble gas isotopes dissolved in groundwater (4He and 81Kr/Kr) provided residence times ranging from recent recharge up to 770 ± 130 ka. Groundwater age modelling confirmed the role of the geological structures in controlling groundwater flow. The southern sector of the SAG is a multilayer aquifer system with vertical flows and deep regional discharge near the Esteros del Iberá wetland area and along the Paraná and Uruguay rivers.


Assuntos
Monitoramento Ambiental/métodos , Água Subterrânea/química , Hélio/análise , Radioisótopos de Criptônio/análise , Rios/química , Ciclo Hidrológico , Argentina , Brasil , Fenômenos Geológicos , Modelos Teóricos , Poluentes Químicos da Água/análise
16.
Isotopes Environ Health Stud ; 56(5-6): 446-464, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32903064

RESUMO

In the eastern region of central Costa Rica, land use in the sub-basins of the Maravilla-Chiz and Quebrada Honda rivers (47 km2) is dominated by agricultural and livestock production, while groundwater resources constitute the main drinking water supply. This study aimed to (a) evaluate the location of groundwater recharge areas and groundwater flow paths, and (b) provide a characterization of the hydrochemistry and possible anthropic impacts. Groundwater was collected from 20 sites during the dry and rainy seasons and analysed for major ions, water stable isotopes and 222Rn. Approximated recharge areas were estimated through a local altitudinal line based on isotopic compositions in springs. The hydrochemical and isotopic characterization of groundwater showed that the main recharge areas occur in the upper part of the basin, except for springs in the middle part of the basin probably due to a certain hydraulic disconnection from the upper part that facilitates local recharge processes. In the lower basin, groundwater exhibited greater transit times and longer flow paths. Low nitrate, chloride and sulphate concentrations found in groundwater indicate low leaching of fertilizers or urban wastewaters. Our results are focused to improve water resources and agricultural management plans in a dynamic tropical landscape.


Assuntos
Monitoramento Ambiental/métodos , Fenômenos Geológicos , Água Subterrânea/química , Isótopos/análise , Ciclo Hidrológico , Abastecimento de Água , Altitude , Costa Rica , Nitratos/análise , Rios/química , Estações do Ano , Clima Tropical , Poluentes Químicos da Água/análise , Recursos Hídricos/provisão & distribução
17.
Isotopes Environ Health Stud ; 56(5-6): 431-445, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32930001

RESUMO

Intensive groundwater use has altered the local hydrological cycle within the Bajío Guanajuatense, Mexico. To improve the knowledge of this hydrogeological system and support water management in the area, groundwater end members were identified using multivariate statistical analysis. Pumped groundwater is composed of two well-mixed end members: (a) recent recharge, affected by a reuse cycle through irrigation where nitrate and chloride evolve and reach levels of 368 mg/L and greater than 100 mg/L, respectively, and (b) deep old groundwater. Mixing estimations show that most wells extract at least 70% of deep groundwater, and some of them extract more than 94%, posing a development and groundwater sustainability conundrum in the area.


Assuntos
Deutério/análise , Monitoramento Ambiental/métodos , Água Subterrânea/análise , Isótopos de Oxigênio/análise , Abastecimento de Água/métodos , Cloretos/análise , Água Subterrânea/química , México , Nitratos/análise , Análise Espaço-Temporal , Ciclo Hidrológico , Poços de Água
18.
Isotopes Environ Health Stud ; 56(5-6): 586-605, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32940532

RESUMO

Hosting the flattest sedimentary plains and highest Andean range of the continent, southern South America faces hydrological transformations driven by climate and land use changes. Although water stable isotopes can help understand these transformations, regional synthesis on their composition is lacking. We compiled for the first time a dataset of H and O isotopic composition for 1659 samples (precipitation, rivers, groundwater and lakes) along latitude (22.4°S to 41.6°S), longitude (55.3°W to 71.5°W), elevation (1-4700 m) and precipitation (∼50 to ∼1500 mm/a) gradients encompassing the Chaco-Espinal-Pampas plains, their adjacent Andean Cordillera and smaller mountain ranges in-between. Emerging patterns reveal (i) only slight seasonal isotope trends in precipitation with no effects of event size, (ii) Atlantic/Amazonian vs. Pacific moisture supply to rivers north and south of the 'arid diagonal' of the continent, respectively, (iii) uniform isotopic composition in Atlantic/Amazonian-fed rivers vs. poleward isotope enrichment in Pacific-fed rivers caused by the elevation decline of the Andes, (iv) strong direct evaporation effect in rivers and shallow (<1 m) phreatic groundwater of the plains. We provide the first integrated water isotope geographical patterns of southern South America helping to improve our understanding of its water cycling patterns at the atmosphere and the land.


Assuntos
Monitoramento Ambiental/métodos , Água Subterrânea/química , Camada de Gelo/química , Lagos/química , Rios/química , Ciclo Hidrológico , Altitude , Argentina , Deutério/análise , Isótopos de Oxigênio/análise , Paraguai , Uruguai , Água
19.
Isotopes Environ Health Stud ; 56(5-6): 480-494, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32951462

RESUMO

Glacial and periglacial basins contain the largest reserves of fresh water in the world. These areas are extremely sensitive to global warming and climate change. The dry Andes of South America are characterized by large periglacial areas. This study focuses on the water isotopic composition and hydrochemistry of a typical periglacial environment of the Andes, in the Vallecitos catchment (2400-5500 m a.s.l.), Cordillera Frontal, Argentina. Detailed fieldwork was conducted between 2013 and 2017 with 240 samples collected for major ions and physicochemical parameters, and 67 samples analysed for 2H and 18O. The chemical composition of precipitation is typical Ca-HCO3, while streams and groundwaters are Ca-MgSO4 type. The isotope content of precipitation shows a wide dispersion. The snow samples are in general more depleted than the rainfall. Some springs vary their composition seasonally, associated to the melting of perennial snow patches. In general, all samples from the upper basin present depleted isotope contents related to recharge at higher altitudes, whereas samples from the lower basin show more enriched values. Intermediate compositions reflect the melting of snow and degrading ice-rich permafrost. These results will give a better understanding of the dynamics of water to manage water resources.


Assuntos
Monitoramento Ambiental/métodos , Água Subterrânea/química , Chuva/química , Rios/química , Neve/química , Recursos Hídricos/provisão & distribução , Altitude , Argentina , Mudança Climática , Deutério/análise , Nascentes Naturais/química , Isótopos de Oxigênio/análise , Pergelissolo/química
20.
Sci Rep ; 10(1): 15379, 2020 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-32958794

RESUMO

Fluorescent natural organic matter at tryptophan-like (TLF) and humic-like fluorescence (HLF) peaks is associated with the presence and enumeration of faecal indicator bacteria in groundwater. We hypothesise, however, that it is predominantly extracellular material that fluoresces at these wavelengths, not bacterial cells. We quantified total (unfiltered) and extracellular (filtered at < 0.22 µm) TLF and HLF in 140 groundwater sources across a range of urban population densities in Kenya, Malawi, Senegal, and Uganda. Where changes in fluorescence occurred following filtration they were correlated with potential controlling variables. A significant reduction in TLF following filtration (ΔTLF) was observed across the entire dataset, although the majority of the signal remained and thus considered extracellular (median 96.9%). ΔTLF was only significant in more urbanised study areas where TLF was greatest. Beneath Dakar, Senegal, ΔTLF was significantly correlated to total bacterial cells (ρs 0.51). No significant change in HLF following filtration across all data indicates these fluorophores are extracellular. Our results suggest that TLF and HLF are more mobile than faecal indicator bacteria and larger pathogens in groundwater, as the predominantly extracellular fluorophores are less prone to straining. Consequently, TLF/HLF are more precautionary indicators of microbial risks than faecal indicator bacteria in groundwater-derived drinking water.


Assuntos
Fezes/microbiologia , Corantes Fluorescentes/química , Água Subterrânea/microbiologia , Triptofano/química , África , Água Potável/química , Água Potável/microbiologia , Monitoramento Ambiental/métodos , Fluorescência , Água Subterrânea/química , Microbiologia da Água , Abastecimento de Água/métodos
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