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Engineered capping systems are efficient tools for the safety concept for landfills and contaminated land, consisting of multilayer barriers installed at the top of the deposited waste, even years after its closure. The efficiency of such systems is closely associated with avoiding rainwater infiltration into the waste body, a process that can be assessed and monitored with geophysical methods, such as Electrical Resistivity Tomography (ERT). A surface geomembrane capping of approximately 900 m2 was installed over an abandoned unlined landfill in southeastern Brazil and ERT surveys were adopted to assay the effectiveness of the intervention measure. It was possible to verify significantly more resistive regions below the geomembrane and an increase in conductivity values only at approximately 6 m, at the groundwater level of the area. Thus, the reduction of rainwater input possibly, even in the short term, reduces the moisture content and prevents the formation of leachate sheets in unlined landfills, leading the deposit to be more isolated from the surroundings. Lateral flow affected distances as far as 2.5 m from the capping borders, showing that about 70% of the capped area was effectively isolated from the rainfall infiltration. Therefore, capping contributed to reducing leachate production and can be considered an effective method for mitigating impacts from old unlined landfills. [ABSTRACT FROM AUTHOR]

This research aimed at evaluating the effects of capping on the mitigation of impacts generated by a closed unlined landfill in São Carlos, SP, Brazil. Physicochemical and microbiological analyses (16S rRNA sequencing) of buried solid waste samples were performed, in capped and uncapped areas. Even though leachate pockets could still be encountered in capped areas, the capping construction reduced oxygen availability and created more reducing conditions, propitiating the development of sulfate-reducing bacteria and possibly contributing to the precipitation of the metals Pb, Cd, Ni, Co, As, and Zn as metal sulfides, causing their immobilization. The microbial populations adapted to the anaerobic conditions created under capped zones belonged to the phyla Firmicutes, Chloroflexi, and Euryarchaeota and the genera Methanosaeta, Hydrogenispora, Smithella, and Gelria. Differently, the phyla Acidobacteria, Proteobacteria, Bacteroidetes, and Actinobacteria were more abundant in samples from the uncapped zones, in which the abundance of different genera varied homogeneously. Methanogenic activity was not impaired by the intervention measure, as assessed by the specific methanogenic activity (SMA). Capping of old unlined landfills brings benefits to the immobilization of metals and does not impair microbial degradation, being effective for the mitigation of impacts on soils and water resources. [ABSTRACT FROM AUTHOR]

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 6.68 mg 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. [ABSTRACT FROM AUTHOR]

General Circulation and Earth System Models are the most advanced tools for investigating climate responses to future scenarios of greenhouse gas emissions, playing the role of projecting the climate throughout the century. Nevertheless, climate projections are model-dependent and may show systematic biases, requiring a bias correction for any further application. Here, we provide a dataset based on an ensemble of 19 bias-corrected CMIP6 climate models projections for the Brazilian territory based on the SSP2-4.5 and SSP5-8.5 scenarios. We used the Quantile Delta Mapping approach to bias-correct daily time-series of precipitation, maximum and minimum temperature, solar net radiation, near-surface wind speed, and relative humidity. The bias-corrected dataset is available for both historical (1980–2013) and future (2015–2100) simulations at a 0.25° × 0.25° spatial resolution. Besides the gridded product, we provide area-averaged projections for 735 catchments included in the Catchments Attributes for Brazil (CABra) dataset. The dataset provides important variables commonly used in environmental and hydroclimatological studies, paving the way for the development of high-quality research on climate change impacts in Brazil. [ABSTRACT FROM AUTHOR]

The traditional approach to characterize extreme rainfall events is based on using past observed data to fit a probability distribution, which is used to associate a certain probability of occurrence to a rainfall magnitude, under a stationary assumption. Observed series, however, may exhibit trends and abrupt changes, resulting from the natural hydro climatic variability and the climate change context, which are not usually considered in the stationary modelling procedure and which may affect the characterization of extreme events. In this paper, it was evaluated the presence of these temporal changes in rainfall series and their impact to estimate design quantiles, using rainfall data of 317 stations, located in São Paulo State, Brazil. The results showed that extreme rainfall events are changing in the state. Low-return period events (up to 10 years) are intensifying. Moderate- and high-return period events, on the other hand, did not present a clear spatial pattern. Trends and abrupt changes may significantly influence the estimation of design quantiles. The presence of the former in rainfall series exhibited more influence on low-return period events, showing, however, no clear relationship with high-return period design quantiles. The presence of the latter seems to influence the characterization process, affecting estimated quantiles of all evaluated return periods. Such findings highlight the need to consider the presence of trends and abrupt changes and their influence on design quantiles for a more reliable characterization. [ABSTRACT FROM AUTHOR]

A better understanding of climate change impacts on water security beyond climate variability is of critical importance to tackle water vulnerabilities exacerbated by increasing extreme weather events. Thus, studies on water security in a changing climate help decision-makers to overcome existing political and socioeconomic challenges worldwide. In this study, future water security of two basins was assessed under climate change and demand scenarios by contrasting water demand with probabilistic levels of water availability to identify possible drivers of insecurity. The Guariroba and Jaguari basins are the main sources for supplying water to Campo Grande city and the São Paulo Metropolitan Region, respectively. The physically-based SWAT+ model was calibrated to simulate the basins' hydrological response to three climate change scenarios from a CMIP6 multimodel ensemble: SSP2-4.5 (medium forcing), SSP3-7.0 (high forcing), and SSP5-8.5 (high forcing). The Guariroba basin already presented scarcity indices close to the security threshold in the baseline period. The imbalance between availability and demand was the main driver of water insecurity in this basin. Despite showing a low scarcity risk in the Jaguari basin in the baseline, this risk considerably increased in the future periods due to a decrease in precipitation. A reduction in water demand of 20% by 2070 was not sufficient to improve water security in both basins. These findings indicate that a lack of policies for adapting demand to a changing availability exacerbates hydrological droughts. More stringent measures to balance water availability and demand are critical for improving water security in an uncertain future. [ABSTRACT FROM AUTHOR]

This study assessed the bacterial populations in a non-sanitary landfill around Guarani Aquifer recharge zone in Brazil. Samples from two different positions (sites 1 and 2) at three different depths were evaluated, totaling six solid waste samples; two samples from an impacted stream were also collected. 16S rRNA sequencing was performed using the Ion S5TM XL platform; 3113 operational taxonomic units (OTUs) and 52 phyla were identified. Proteobacteria (37%) and Firmicutes (28%) were the most abundant phyla in the landfill, whereas Proteobacteria (~ 50%) and Bacteroidetes (~ 10%) were more profuse in surface water samples. Canonical correlation analysis (CCA) enabled us to clearly separate the samples according to their spatial location (site 1 or 2) or environmental matrix (surface water or solid waste samples), showing that microbiological populations are strongly associated with site-specific conditions and the kind of environmental matrix they come from. Environmental factors that mostly influenced the microbial communities were organic matter, oxidation–reduction potential, moisture, alkalinity, nitrogen (TKN), sodium, potassium, and zinc. Exiguobacterium (phylum Firmicutes) was overwhelmingly dominant at site 1 and was associated with higher concentrations of organic matter and potassium. Differently, site 2 did not present such dominant genera and was more diverse having lower concentrations of organic matter and nutrients. Distinct environments co-exist inside the same waste deposit, including zones which are representative of active and closed landfills and the occurrence of considerable physicochemical and microbiological shifts within short distances. Those shifts indicate that microbial populations are well adapted to the heterogeneity typical of urban solid waste, which is possibly beneficial to contaminant degradation. [ABSTRACT FROM AUTHOR]

Improper landfills (waste dumps) are common waste disposal systems in developing countries and represent sources of environmental pollution. These sites defy researchers and managers because they lack structures to collect liquid, solid and gaseous samples, which make it challenging to monitor local environmental quality. In this work, we show one device for sample collection to monitor leachate quality in a closed waste dump in Brazil. During the installation of this device (Leachate Monitoring Station, LMS), interesting facts about the structural, physical, and chemical composition of an old dump could be visualized. Two different kinds of leachate were found: the accumulated leachate (AL), a thick dark fluid entrapped above non-degraded material, and the mobile leachate (ML), a lighter liquid which flowed into the LMS, and thus was not stagnant like AL. In the AL, the chemical oxygen demand and total ammoniacal nitrogen average concentrations were about 21,500 mg/L and 1000 mg/L, respectively, which were considerably higher than the ML concentrations, of about 1100 mg/L and 200 mg/L, respectively, for the same parameters. Thus, despite the lower concentrations of hazardous substances in the ML, the waste body stores pockets of leachate (AL) with significant concentrations of hazardous compounds, even after 15 years of the dumpsite closure. Moreover, waste solubilization assays showed that the solid material could not be considered inert according to the Brazilian Standard Norm NBR 10004/2004. The installation of the LMS enabled a new understanding about pollutant accumulation inside waste deposits and provided an effective, low-cost tool to monitor leachate production in non-sanitary landfills. The results warn about the risks that old dumpsites still pose to the environment and reinforce the need for a post-care action plan for managing uncontrolled waste deposits. [ABSTRACT FROM AUTHOR]

The inadequate disposal of solid waste, a common practice in developing countries, can represent an important pollution source since the closure of these deposits typically does not include the adoption of monitoring, isolation, or remediation techniques. Even so, several disposal areas are abandoned, without performing long-term monitoring in order to evaluate the depletion of contaminants' concentrations. This research aimed at comparing current and historical physicochemical data of water resources surrounding a non-sanitary landfill situated in a Guarani Aquifer recharge zone. The primary objective was to recognize whether significant changes in contaminants concentrations occurred, as well as if the area still poses a significant threat to the environment, 20 years after ending disposing activities. Samples from eight monitoring wells and three surface water points (upstream and downstream to the deposit) were evaluated in the periods of 1996–1997 and 2016–2019. The parameters pH, electrical conductivity (EC), alkalinity, chemical oxygen demand (COD), oxidation-reduction potential (ORP), chloride, nitrate, iron, manganese, calcium, and magnesium were investigated. Contamination has been detected in the landfill surroundings since the ending of the waste disposal (1996–1997), even though its intensity reduced within short distances from the waste mass. Nevertheless, no statistical variation occurred in 20 years' time considering COD, chloride, calcium, magnesium, and ORP. Moreover, increases of EC, pH, alkalinity, iron, and manganese concentrations were observed for the years of 2016–2019. The results indicate that the evaluated contaminants do not suffer depletion in the surroundings of non-sanitary landfills in sandy aquifers, considering a time span of 20 years. This study also suggests that those areas need to be adequately remediated to permit other future land uses. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Stochastic methods based on time-series modeling combined with geostatistics can be useful tools to describe the variability of water-table levels in time and space and to account for uncertainty. Monitoring water-level networks can give information about the dynamic of the aquifer domain in both dimensions. Time-series modeling is an elegant way to treat monitoring data without the complexity of physical mechanistic models. Time-series model predictions can be interpolated spatially, with the spatial differences in water-table dynamics determined by the spatial variation in the system properties and the temporal variation driven by the dynamics of the inputs into the system. An integration of stochastic methods is presented, based on time-series modeling and geostatistics as a framework to predict water levels for decision making in groundwater management and land-use planning. The methodology is applied in a case study in a Guarani Aquifer System (GAS) outcrop area located in the southeastern part of Brazil. Communication of results in a clear and understandable form, via simulated scenarios, is discussed as an alternative, when translating scientific knowledge into applications of stochastic hydrogeology in large aquifers with limited monitoring network coverage like the GAS. [ABSTRACT FROM AUTHOR]

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Due to the general lack of appropriate surface waste dumpsites in North-Rhine-Westphalia (Germany), placing filter ashes and desulphurisation residues from power plants in underground coal mines has become an attractive alternative. The residues can be injected as a hydraulic suspension into exploited coal seams. In this paper, we summarize the fundamental geotechnical aspects that define the hydrochemical barriers for underground repositories. The environmental advantages and disadvantages of this concept are discussed. Laboratory and field investigations as well as modelling are presented in order to establish the environmental reliability of such repositories. [ABSTRACT FROM AUTHOR]

Copyright of Grundwasser is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)