Groundwater quality in coal-bearing regions is often compromised by natural and anthropogenic sulfide mineral oxidation, challenging the application of standard environmental limits. This study’s main objective was to evaluate the effectiveness of different statistical outlier removal methods for establishing geochemically coherent natural background levels (NBLs) from historical databases, using the Transgressive Sand sequence aquifer in the South Santa Catarina Coalfield, Brazil, as a representative case study. Using a historical dataset of 66 analyses from 19 unimpacted wells, we compared three techniques: the interquartile range, the modified Z-score, and the iterative Grubbs’ test. The resulting datasets were used to estimate NBLs for pH, Eh, electrical conductivity, sulfate, Fe, Al, and Mn, and were further assessed using Pearson correlation and principal component analysis (PCA), as combining statistical filtering with hydrochemical validation is essential for ensuring robust interpretation. Results show the Grubbs’ test was the most robust method, preserving natural data heterogeneity and providing the most geochemically consistent dataset. The NBLs estimated from the Grubbs’ dataset revealed naturally acidic conditions (pH 4.4–6.3) and elevated concentrations of Al, Fe, and Mn, frequently exceeding Brazilian drinking water standards. PCA of the Grubbs’ data explained 60

The increasing demand for consumer products has led to the continuous introduction of novel substances into the environment. This contributes to contamination of environmental compartments and poses potential risks to human health. Many of these substances are classified as emerging contaminants and are detected at trace levels in various matrices, including groundwater. This study investigates the presence of emerging contaminants in shallow groundwater from a nonindustrial urban area potentially impacted by domestic wastewater, with an emphasis on per- and polyfluoroalkyl substances (PFAS). Twenty groundwater samples were collected in São Paulo city, Brazil, from older neighborhoods suspected of sewage collection system leakage, covering an entire hydrological cycle, that is, both dry and wet seasons. Samples were analyzed using liquid chromatography coupled with mass spectrometry (LC–MS/MS). PFAS were detected in concentrations ranging from 4.8 to 45.7 ng/L, with PFOS and PFOA being the most prevalent. Additionally, pesticides (1.1–736 ng/L), hormones (< LOQ–8.0 ng/L), pharmaceuticals (2.9–255 ng/L), and industrial compounds (14.1–314 ng/L) were also quantified in the samples. Although these concentrations are considered background levels associated with diffuse sources, the findings highlight the need for more comprehensive studies to assess the occurrence, sources, and potential health impacts of emerging contaminants in groundwater systems.

Groundwater quality in coal-bearing regions is often compromised by natural and anthropogenic sulfide mineral oxidation, challenging the application of standard environmental limits. This study aims to define Natural Background Levels (NBLs) for groundwater of Transgressive Sand Sequence aquifer interval in the South Santa Catarina Coalfield, Brazil, and to evaluate the effectiveness of different statistical methods for this purpose. Using a historical database of 66 analyses from 19 unimpacted wells, we compared three outlier removal techniques: the interquartile range (IQR), the modified Z-score, and the iterative Grubbs' test. The resulting datasets were used to estimate NBLs for pH, Eh, electrical conductivity, sulfate, Fe, Al, and Mn, and were further assessed using Pearson correlation and Principal Component Analysis (PCA) to verify hydrogeochemical coherence. Results show the Grubbs' test was the most robust method, preserving natural data heterogeneity and providing the most geochemically consistent dataset. The NBLs estimated from the Grubbs' dataset revealed naturally acidic conditions (pH 4.43–6.25) and elevated concentrations of Al, Fe, and Mn, frequently exceeding Brazilian drinking water standards. PCA of the Grubbs’ data explained 60% of the total variance, effectively separating variables associated with sulfide oxidation. This study demonstrates that the Grubbs' test is a superior tool for establishing realistic NBLs in geologically complex areas, highlighting that generic water quality legislation may be inadequate for recovery and rehabilitation targets of regions with significant mineralization.

This study presents a hydrogeological characterization that fills knowledge gaps in an area where a complex geological scenario connects two fractured (granite/metamorphic rocks and diabase) and one porous (sedimentary rocks) aquifer systems. Previous groundwater studies from the four local deep supply wells suggested the sedimentary aquifer as the source of uranium (similar to 60 mu g/L) in one of the wells. Despite the water extraction interruption from this well, this finding needed to be supported by evidence provided by the geological and structural characteristics of the aquifers. Data collected through video inspection, caliper, optical (OPTV), and acoustic borehole televiewers (ATV) revealed the predominance of the crystalline aquifer in the area. As recorded by video inspection, the well ' s borehole with high U intersects the crystalline rocks at several open fractures and presents the highest gamma radiation values. Therefore, we infer that the origin of dissolved U is the weathering of primary minerals locally occurring in those rocks. The U leaching and complexation as calcium-uranylcarbonates favors its solubility in that specific aqueous medium, as shown by hydrogeochemical modeling using PHREEQC. Additionally, the major ions and trace elements concentrations allow the division of the wells into two groups: a) two with higher U concentrations, influenced by the granite/metamorphic aquifer and possibly longer residence times, and b) the other two wells with lower U concentrations, higher nitrate concentrations, influenced by the diabase aquifer, possibly have younger residence times.

This study refines the hydrogeological conceptual model of an area with three interconnected aquifers, namely the Crystalline Aquifer System (CAS - igneous and metamorphic rocks), which is in contact with the Tubara similar to o Aquifer System (TAS - sedimentary rocks) and the Diabase Aquifer System (DAS - diabase rocks). The detailed investigation involved geophysical logging and hydraulic and hydrodynamic characterization with straddle packers in a local tubular well, in which groundwater presents high uranium concentrations. Hydrogeochemical and isotope (delta H-2, delta O-18, H-3, delta C-13, C-14) analysis in this well and in other three neighboring wells, with lower U concentrations, showed that ancient and modern waters (H-3 from <0.8 to 1.12 TU, C-14 from 69.43 to 78.72 pMC) mix within the aquifer. During groundwater pumping, vertical fractures in the diabase aquifer possibly induce water mixing and recharge of the deeper levels of the aquifers from shallow layers. The high [U] are related to ancient waters from a confined aquifer hosted in CAS that reaches the wells through hydraulically active fractures located deeper than 159 m depth. Groundwater apparent ages do not increase systematically with depth, revealing a complex circulation model for CAS. The results obtained from the other wells, which are all located on drainage lineaments, reveal that one extracts modern water from DAS and TAS, another one extracts modern and ancient water from DAS and CAS, and the third extracts only ancient water from CAS, confirming the complexity of the local hydrogeology. Regarding regional groundwater management, the study revealed the need to characterize the sources of groundwater in each well, in order to protect modern waters from anthropogenic contamination and to protect ancient groundwater from overexploitation, as CAS hosts groundwaters recharged thousands of years ago or more.

In the Brazilian state of São Paulo, contaminated sites (CSs) constitute threats to health, environment and socioeconomic situation of populations. Over the past two decades, the Environmental Agency of São Paulo (CETESB) has monitored these known CSs. This paper discusses the produced dataset through digitising the CETESB reports and making them accessible to the public in English. The dataset reports on qualitative aspects of contamination within the registered sites (e.g., contamination type and spread) and their management status. The data was extracted from CETESB reports using a machine-learning computer vision algorithm. It comprises two components: an optical character recognition (OCR) engine for text extraction and a convolutional neural network (CNN) image classifier to identify checked boxes. The digitisation was followed by harmonisation and quality assurance processes to ensure the consistency and validity of the data. Making this dataset accessible will allow future work on predictive analysis and decision-making and will inform the required policy-making to improve the management of the CSs in Brazil.

Existem propriedades e regiões contaminadas que têm sido denominadas no exterior como Áreas Complexas em virtude de desafios técnicos ou não técnicos que requerem estratégias e prazos atípicos para sua restauração. Uma área de estudo desse tipo, com mais de 20 anos de gerenciamento ambiental, foi objeto de modelagem implícita para auxiliar no detalhamento e avaliação do seu Modelo Conceitual Temporal. Os resultados reforçaram o entendimento claro e holístico sobre sua evolução e seus desafios, incluindo Plumas Combinadas geradas de fontes com localização distinta. Foi confirmado que as intervenções na área se beneficiaram de entendimentos regionais e aspectos de Gerenciamento Adaptativo, tais como a definição de objetivos intermediários e o contínuo aperfeiçoamento do modelo conceitual e da remediação. Concluiu-se que o reconhecimento de Áreas Complexas e a aplicação de Gerenciamento Adaptativo têm o potencial de auxiliar no gerenciamento de mais locais no Brasil. Recomenda-se que isso seja feito contemplando adaptações e considerações locais, tais como: englobar, na definição de Áreas Complexas, que os desafios devem, comprovadamente, apresentar alta complexidade e requerer tempos atípicos para sua restauração ou reabilitação (mais de 15 anos, em São Paulo); considerar como desafio técnico o extenso manto de intemperismo de regiões tropicais úmidas; apreciar como desafio técnico e não técnico o alto número de poços de captação não outorgados; considerar como desafio não técnico a existência de conflitos socioeconômicos; e avaliar, inclusive com estudos isotópicos, a possível presença de Plumas Combinadas.

Most of the contaminant conceptual models in weathered crystalline bedrock aquifers in Brazil rely on data collected using conventional site investigation methods, at insufficient spatial resolution for associating contaminant distributions with observed heterogeneity. The DFN methodology was adapted for the characterization of a chlorinated solvent contaminated weathered crystalline bedrock aquifer, located in the region of the Jurubatuba district, Sao Paulo city, Brazil. The objective of this research is to establish a detailed 1-D conceptual model to show variable contaminant distribution within the bedrock matrix under different fracture and weathering conditions. The numerous depth-discrete rock sample analyses, assigned to specific geologic features, indicate the presence of PCE-Dense Non-Aqueous Phase Liquid (DNAPL) at discrete-depth intervals along the profile. These zones are mainly related to the lithological contacts and interfaces among the weathered bedrock. The soft and hard weathered-bedrock transition zone does not indicate a sharp decrease in the contaminant mass retention within the bedrock matrix for the studied area. This indicates that contaminant mass storage in the bedrock remains beyond this drilling method-defined interface, which can potentially sustain dissolved VOC concentrations over time and maintain the continuous vertical mass flux into deeper parts of the aquifer. There is a demonstrated need for an appropriate characterization methodology including high-resolution soil coring and sampling to delineate contaminant distribution over crystalline weathered bedrock aquifers. This is a key assumption for the definition of appropriate remedial and groundwater management strategies.

Este trabalho analisou a contaminação por nitrato no Sistema Aquífero Bauru (SAB) na área urbana do município homônimo, relacionando sua ocorrência com a urbanização. A metodologia utilizada incluiu: i) cadastro e tratamento de dados hidroquímicos de 634 poços tubulares; ii) levantamento da evolução do esgotamento sanitário desde 1976 a 2022; iii) análise do uso e ocupação do solo; e iv) avaliação da evolução das concentrações de nitrato entre 1999 e 2022. A análise das concentrações recentes de nitrato em 151 amostras de águas subterrâneas, provenientes de 76 poços selecionados, permitiu identificar concentrações de até 23 mg/L N-NO3-, que se distribuem,sobretudo, na região central da cidade, ocupada entre 1910 e 1980, com esgotamento sanitário mais antigo (anterior a 1976) e densidade de ocupação urbana de média a alta. Tendências de aumento nos valores das medianas (Md) das concentrações de nitrato foram observadas, de 0,20 a 3,29 mg/L N-NO3-. As análises estatísticas entre as concentrações de nitrato, idades da mancha urbana e da rede de esgoto, densidade de ocupação urbana e profundidade dos poços mostraram que a urbanização e o saneamento controlam a presença desse contaminante no aquífero.

• Combination of multiple high-resolution borehole characterization methods. • Hydrogeologic unit boundaries are not predicted solely from the geologic logs. • Variable hydraulic connectivity between and within fresh and weathered units. • Higher transmissivities associated with intercalation of fracture sets and 3 lithologies.

Chlorinated ethanes and ethenes isotopic analyses in groundwater and hydrogeochemical results from a former industrial area in Sao Paulo (Brazil) were used to confirm the existence and allow further characterization of source areas and their commingled plumes, both before and after thermal and bioremediation treatments. Prior to full scale remediation, a recently identified off-site source area with unknown history and limited access for further intrusive works presented lower δ13C values (-6.5‰ to -1.8‰ for 1,2-DCA) than the downgradient on-site source area (+8.6‰ to +20.0‰). Intermediate δ13C values for 1,2-DCA were identified further downgradient from the sources, within commingled plumes patterns. The isotope and concentration results show the typical degradation patterns associated with biotic reductive dechlorination for chlorinated ethenes and dihaloelimination for 1,2-DCA. Results following remediation treatments show further levels of isotopic enrichment, for chlorinated ethenes and chlorinated ethanes in the tropically weathered and deeper fractured bedrock (gneisses) groundwater. Hydrogeochemical results, isotopic mass balance and Carbon-Chlorine isotope slopes data are coherent with remediation treatment and a complex commingled plume setting. The results of this study confirmed the Temporal Conceptual Model proposed by Hart et al. (2021) and identified the need for further studies to evaluate isotopic dynamics under thermal remediation, including thermal-induced hydrolysis processes.

Conventional analytical methods determine the concentration of compounds used to estimate the presence of environmental contamination capable of posing risk to human and ecological receptors. While these target analytes help regulators and environmental professional identify and manage potentially harmful conditions, these compounds can be generated by many natural and anthropogenic (man-made) sources and conventional methods alone fail to compositionally differentiate subsurface sources of contamination in complex environments. This case study demonstrates the advantage of using both conventional and forensic testing methods to accurately identify the source(s) of volatile hydrocarbon contamination in soil vapor samples for the development of an accurate conceptual site model in a neighbourhood near industrial facilities in Rio de Janeiro State, Brazil. The goal of this study was to differentiate potential impacts from a local steelmaking plant from fugitive hydrocarbons associated with more generic human activity in urban settings. This case study demonstrated the advantage of constructing chemical fingerprints from conventional volatile organic compound (VOC) method TO 15 and a forensic volatile hydrocarbon method using an enhanced version of method TO 15 (PIANO). The chemical fingerprints of vapor samples collected from subsurface soil gas and sewers were analysed and compared to laboratory reference samples. These data determined that the VOCs detected in neighbourhood soil vapor samples were associated with fugitive petroleum products migrating in the sewer pipelines and not with the steelmaking wastes emplaced near the residential area. This article discusses the forensic data and chemical signatures that support these findings, and the use of environmental forensic techniques to evaluate environmental data associated with complex scenarios, involving multiple contamination sources.

A demanda por água subterrânea no estado do Espírito Santo vem crescendo consideravelmente frente aos eventos de escassez que marcaram os últimos anos. No entanto, a carência de conhecimentos hidrogeológicos compromete a locação de poços e a previsão da qualidade das águas, especialmente nos terrenos de rochas cristalinas. Este trabalho teve como objetivo uma avaliação hidrogeoquímica e da qualidade da água subterrânea do Sistema Aquífero Cristalino na Bacia Hidrográfica do Rio Itapemirim (BHRI), situada no sul do estado do Espírito Santo, descrevendo as variações composicionais e os condicionantes que influenciam a qualidade da água subterrânea. A compartimentação litológica e geomorfológica da bacia e as condições climáticas são os fatores que influenciam na hidrogeoquímica em escala regional, enquanto o uso e a ocupação do solo exercem influência pontual. Na porção da Alta BHRI, com relevo acidentado e predomínio de atividades agropecuárias, ocorrem principalmente águas bicarbonatadas cálcicas e bicarbonatadas cálcicas-magnesianas, pouco mineralizadas comparativamente à porção central da bacia, com composição química governada essencialmente pelo intemperismo das rochas silicáticas. Embora sejam águas de boa qualidade, alterações locais podem ocorrer em razão do nitrato proveniente de atividades antrópicas. Na porção da Média BHRI, com menores altitudes e relevo mais suave, as águas são predominantemente bicarbonatadas sódicas e cloretadas sódicas, com maior mineralização em relação à porção alta da bacia em razão da contribuição de rochas silicáticas em associação com litotipos carbonáticos, como mármores e calciossilicáticas. Nessa porção da bacia, as condições climáticas, com temperaturas mais altas e menor umidade do ar na área central da bacia, topograficamente mais rebaixada, também podem contribuir com o enriquecimento mineral em decorrência da evaporação da água que infiltra

No contexto brasileiro, aquíferos cristalinos fraturados têm importância significativa para o abastecimento público e privado nas regiões mais povoadas e de maior relevância econômica, o que justifica a necessidade de se avançar cada vez mais no seu conhecimento. Em geral, entretanto, várias das técnicas e ferramentas adequadas para a investigação desse meio geológico ainda são pouco exploradas na totalidade, tanto para as tarefas de locação de novos poços, como para a previsão do comportamento de contaminantes em situações de investigação de áreas contaminadas. Neste estudo, se pretende chamar a atenção para a aplicação conjunta de técnicas convencionais para o desenvolvimento de um modelo conceitual geológico numa área contaminada em aquífero fraturado, cujos resultados embasam as etapas de investigações subsequentes, mais avançadas. A metodologia integra três técnicas tradicionais e não invasivas, com escalas de investigação se desenvolvendo da regional para a local (top-down): (1) análise de lineamentos; (2) amostragem estrutural em afloramentos; e (3) imageamento geofísico pelo método de caminhamento elétrico. No caso estudado, as três técnicas geraram resultados progressivamente consistentes para a melhor caracterização do aquífero, possibilitando a identificação dos trends estruturais e dos principais grupos de fraturas da região. Assim, os lineamentos identificados guardaram ótima correlação com os trends estruturais identificados em campo; similarmente, zonas de baixa resistividade identificadas nos caminhamentos elétricos coincidiram com a localização dos lineamentos e das zonas de fraturas. A correlação entre os resultados das três etapas foi fundamental para a melhor compreensão da dinâmica de fluxo do aquífero, estabelecendo, em escala local, o modelo conceitual geológico-estrutural e as estruturas que apresentam maior potencial para fluxo de água e, potencialmente, para o transporte de contaminantes.

Temporal Conceptual Model can enhance the long-term management of contaminated Complex Sites. This type of contaminated land model is defined here as the sequential or combined representation over time of single time conceptual models (named here as Snapshot Conceptual Models) including contaminant evolution, most likely causes, eventual receptor changes and uncertainties. Understanding contamination behaviour in crystalline fractured rock within tropical humid regions involves several technical complexities and typically requires long term management. This was the case of a Former Supply Well area managed over 20 years for land reuse, located in the water stressed Metropolitan Region of Sao Paulo. A Temporal Conceptual Model approach was voluntary developed for the Former Supply Well area that, together with complementary characterization activities, was used to enhance the understanding, remediation and monitoring of its unconfined aquifer system. They indicated that the contamination concentrations in the Former Supply Well and multilevel wells changed intensively over time. It was identified that the contaminant distribution was controlled by the extensive rock weathering levels and variations in: pumping regimes, well reconfigurations, effects of several stages of remediation works, influence of other source areas and dynamics of a likely commingled plume. The further understanding of the hydrogeology specific conditions allowed the advancement of communication with stakeholders, management works and local land reuse plans.

The geological scenario of thick weathering materials over a fresh bedrock is characteristic of tropical climate regions. The application of the Discrete Fracture Network (DFN) methodology relying on multiple, high resolution measurements methods on continuous cores and/or boreholes in such geological conditions, particularly in a contaminated area, is unprecedent. A total of 977 structures were described, between rock cores, geophysical profiling and outcrops, with emphasis on brittle structures due to their importance for groundwater flow. Five fracture sets were characterized, related to lithology. The correlation of these fracture sets with large structures from regional studies indicated the representativeness of this detailed survey. Finally, it is expected that the model presented here can be applied in the management of other contaminated areas of similar geological contexts, particularly in Brazil, where the discussions regarding contaminated fractured aquifers are still quite recent.

A new version of the computer program FLASH (Flow-Log Analysis of Single Holes) is presented for the analysis of borehole vertical flow logs to estimate fracture (or layer) transmissivities and far-field hydraulic heads. The program is written in R, an open-source environment. All previous features have been retained and new features incorporated including more rigorous parameter estimation, uncertainty analysis, and improved data import. The program has a dynamic user interface compatible with most operating systems.