Measurement Uncertainty and Risk of False Compliance Assessment Applied to Carbon Isotopic Analyses in Natural Gas Exploratory Evaluation.

The concept of uncertainty in an isotopic analysis is not uniform in the scientific community worldwide and can compromise the risk of false compliance assessment applied to carbon isotopic analyses in natural gas exploratory evaluation. In this work, we demonstrated a way to calculate one of the main sources of this uncertainty, which is underestimated in most studies focusing on gas analysis: the δ13C calculation itself is primarily based on the raw analytical data. The carbon isotopic composition of methane, ethane, propane, and CO2 was measured. After a detailed mathematical treatment, the corresponding expanded uncertainties for each analyte were calculated. Next, for the systematic isotopic characterization of the two gas standards, we calculated the standard uncertainty, intermediary precision, combined standard uncertainty, and finally, the expanded uncertainty for methane, ethane, propane, and CO2. We have found an expanded uncertainty value of 1.8‰ for all compounds, except for propane, where a value of 1.6‰ was obtained. The expanded uncertainty values calculated with the approach shown in this study reveal that the error arising from the application of delta calculation algorithms cannot be neglected, and the obtained values are higher than 0.5‰, usually considered as the accepted uncertainty associated with the GC-IRMS analyses. Finally, based on the use of uncertainty information to evaluate the risk of false compliance, the lower and upper acceptance limits for the carbon isotopic analysis of methane in natural gas are calculated, considering the exploratory limits between -55‰ and -50‰: (i) for the underestimated current uncertainty of 0.5‰, the lower and upper acceptance limits, respectively, are -54.6‰ and -50.4‰; and (ii) for the proposed realistic uncertainty of 1.8‰, the lower and upper acceptance limits would be more restrictive; i.e., -53.5‰ and -51.5‰, respectively.

Marine coastal chemistry related to inland inputs in San Jorge gulf and the adjacent north coast.

Coastal regions are sectors where human activities impact the marine ecosystem, and if necessary control measures are not taken, they can generate negative consequences for health and ecosystem services. Within the framework of the Pampa Azul initiative and under the One Health paradigm, the interconnection between the terrestrial and marine environments of the San Jorge Gulf and the adjacent north coast has been studied. In November, 2022, a campaign was carried out aboard the R/V "Mar Argentino" at thirty-four stations near the coast. There, for the first time, simultaneously with in-situ measurements of physical variables, macronutrients (NO3-, PO4-3, Si(OH)4 and NH4+), particulate silica (BSi and LSi), trace metals in the particulate material (Cd, Cu, Cr, Fe and Pb) and the phytoplankton community were analyzed. The results showed a high nutrient dynamic, with a significant influence of natural stratification and anthropogenic condition due to the discharge of effluents off the cities of Comodoro Rivadavia and Caleta Olivia. Under natural conditions, NO3- and Si(OH)4 limited the surface primary production by 47 % and 41 %, respectively. Additionally, due to the anthropogenic contribution, NH4+ concentration reached 3 µM, increasing the proliferation of nanophytoplankton, among other consequences. As a result of nutrient dynamics, the uptake of Si(OH)4, the growth rate of diatoms and their production of BSi were decoupled. Furthermore, a significant correlation between LSi and Fe in particulate matter was evidenced, opening new lines of research that relate dust storms to primary productivity in this marine environment. The measured concentrations of trace metals do not appear to be a biological risk; however, contamination by Cd (37.6 µg g- 1 d.w.) and Cu (214.97 µg g- 1 d.w.) off Camarones poses a significant concern that must be addressed in the immediate future.

Modeling groundwater redox conditions at national scale through integration of sediment color and water chemistry in a machine learning framework.

Redox conditions play a crucial role in determining the fate of many contaminants in groundwater, impacting ecosystem services vital for both the aquatic environment and human water supply. Geospatial machine learning has previously successfully modelled large-scale redox conditions. This study is the first to consolidate the complementary information provided by sediment color and water chemistry to enhance our understanding of redox conditions in Denmark. In the first step, the depth to the first redox interface is modelled using sediment color from 27,042 boreholes. In the second step, the depth of the first redox interface is compared against water chemistry data at 22,198 wells to classify redox complexity. The absence of nitrate containing water below the first redox interface is referred to as continuous redox conditions. In contrast, discontinuous redox conditions are identified by the presence of nitrate below the first redox interface. Both models are built using 20 covariate maps, encompassing diverse hydrologically relevant information. The first redox interface is modelled with a mean error of 0.0 m and a root-mean-squared error of 8.0 m. The redox complexity model attains an accuracy of 69.8 %. Results indicate a mean depth to the first redox interface of 8.6 m and a standard deviation of 6.5 m. 60 % of Denmark is classified as discontinuous, indicating complex redox conditions, predominantly collocated in clay rich glacial landscapes. Both maps, i.e., first redox interface and redox complexity are largely driven by the water table and hydrogeology. The developed maps contribute to our understanding of subsurface redox processes, supporting national-scale land-use and water management.

Unexpected contributions by carbonates and organic matter in a silicate-dominated tropical catchment: An isotope approach.

The understanding of global carbon has rarely extended to small-scale tropical river basins. To address these uncertainties, this study aims to investigate the importance of rock weathering and organic matter turnover in the carbon cycle in a terrain dominated by crystalline silicate rocks. The geochemical composition of the dissolved and particulate carbon phases (DIC, DOC and POC) and their stable carbon isotopes were studied in the Deduru Oya River in Sri Lanka. Dissolved inorganic carbon (DIC) was the most dominant carbon phase and its contribution to the total carbon pool varied between 67 and 89 %. Furthermore, the δ13CDIC values in the river varied between -1.1 and -16.5 ‰. The lithological characteristics and molar ratios between Ca2+, Mg2+ and HCO3- indicated rock weathering mainly by CO2 and carbonic acid. The δ13CDIC values for groundwater input were -15.9 ‰, while for carbonate weathering, mainly due to fertiliser input, they reached a value of -12.7 ‰. This input was fed into an isotope mass balance to determine the relative contributions. However, the isotope mass balance was only plausible after correcting for the effects on the δ13CDIC caused by degassing and photosynthesis. Our study demonstrated that carbonate weathering and organic matter turnover are essential components of the river carbon cycle even in a silicate dominated catchment. They can represent up to 60 % of the DIC pool. Combined with the higher organic matter turnover and high pCO2 in the river water, it can be suggested that the Deduru Oya River acts as a net source of CO2 in the atmosphere. Our study shows that CO2 degassing and in-stream photosynthesis in tropical river systems need to be considered along with chemical weathering to account for carbon transport and turnover in tropical rivers.

Fe-rich X-ray amorphous material records past climate and persistence of water on Mars.

X-ray amorphous material comprises 15-73 wt.% of sedimentary rocks and eolian sediments in Gale crater. This material is variably siliceous and iron rich but aluminum poor. The presence of volatiles is consistent with the existence of incipient weathering products. To better understand the implications of this material for past aqueous conditions on Mars, here we investigate X-ray amorphous material formation and longevity within terrestrial iron rich soils with varying ages and environmental conditions using bulk and selective dissolution methods, X-ray diffraction, and transmission electron microscopy. Results indicate that in situ aqueous alteration is required to concentrate iron into clay-size fraction material. Cooler climates promote the formation and persistence of X-ray amorphous material whereas warmer climates promote the formation of crystalline secondary phases. Iron rich X-ray amorphous material formation and persistence on Mars are therefore consistent with past cool and relatively wet environments followed by long-term cold and dry conditions.

Stable isotope analysis in soil prospection reveals the type of historic land-use under contemporary temperate forests in Europe.

The determination of δ13C and δ15N values is a common method in archaeological isotope analysis-in studying botanical and human remains, dietary practices, and less typically soils (to understand methods of agricultural cultivation, including fertilization). Stable isotope measurements are also commonly used in ecological studies to distinguish different ecosystems and to trace diachronic processes and biogeochemical mechanisms, however, the application of this method in geochemical prospection, for determining historic land-use impact, remains unexplored. The study at hand focuses on a deserted site of a Cistercian manor, dating from the thirteenth to fifteenth centuries. Isotopic measurements of anthropogenically influenced soils have been compared to approximately 400 archaeobotanical, soil, and sediment samples collected globally. The results reveal the potential of isotope measurements in soil to study the impact of past land use as isotope measurements identify specific types of agricultural activities, distinguishing crop production or grazing. δ13C and δ15N ratios also likely reflect fertilization practices and-in this case-the results indicate the presence of cereal cultivation (C3 cycle plants) and fertilization and that the site of the medieval manor was primarily used for grain production rather than animal husbandry.

Isolation and Characterization of Thermophilic Bacteria from a Hot Spring in the State of Hidalgo, Mexico, and Geochemical Analysis of the Thermal Water.

Hot springs worldwide can be a source of extremophilic microorganisms of biotechnological interest. In this study, samplings of a hot spring in Hidalgo, Mexico, were conducted to isolate, identify, and characterize morphologically, biochemically, and molecularly those bacterial strains with potential industrial applications. In addition, a physicochemical and geochemical examination of the hot spring was conducted to fully understand the study region and its potential connection to the strains discovered. The hot spring was classified as sulfate-calcic according to the Piper Diagram; the hydrogeochemical analysis showed the possible interactions between minerals and water. Eighteen bacterial strains were isolated with optimal growth temperatures from 50 to 55 °C. All strains are Gram-positive, the majority having a rod shape, and one a round shape, and 17 produce endospores. Hydrolysis tests on cellulose, pectin, and xylan agar plates demonstrated enzymatic activity in some of the strains. Molecular identification through the 16S rDNA gene allowed classification of 17 strains within the Phylum Firmicutes and one within Deinococcus-Thermus. The bacterial strains were associated with the genera Anoxybacillus, Bacillus, Anerunibacillus, Paenibacillus, and Deinococcus, indicating a diversity of bacterial strains with potential industrial applications.

Structural insights linking H-bridging of archaeal GDGTs to high temperature.

Isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs), characteristic membrane lipids of archaea, are widely used in ecological and geochemical studies, especially for paleoenvironmental reconstruction. Glycerol monoalkyl glycerol tetraethers (GMGTs, also known as H-GDGTs), a unique variant of GDGTs, have covalent bonds linking the two alkyl chains. Despite some studies suggesting a link between GMGTs and high temperatures, the reliability and mechanisms remain unclear. Using molecular dynamics simulations, we elucidated the mechanism connecting GMGTs to high temperatures. Our findings show that H-bridging linkages reduce the distance between alkyl chains, leading to thicker and denser membranes with lower fluidity and permeability. The diffusion coefficient of GMGTs decreased by approximately 35 % compared to GDGTs, indicating their role as a archaeal high-temperature adaptation. This study provides a mechanistic basis for using archaeal GMGTs in geochemical studies and enhances confidence in their use for paleotemperature reconstruction.

Large shallow lake response to anthropogenic stressors and climate change: Missing macroinvertebrate recovery after oligotrophication (Lake Balaton, East-Central Europe).

East-Central Europe's largest shallow lake, Balaton, experienced strong eutrophication in the 1970-80s, followed by water quality improvement and oligotrophication by 2010 CE. Recently however, repeated cyanobacterial blooms occurred and warned that internal P-recycling can act similarly to external P load, therefore we need a better understanding of past water level (WL) and trophic changes in the lake. In this study we discuss the last 500-yr trophic, WL and habitat changes of the lake using paleoecological (chironomids, pollen) and geochemical (sediment chlorophyll, TOC, TS, TN, C/H ratio, major and trace element) methods. We demonstrate that the most intensive and irreversible change in the macroinvertebrate fauna occurred during the period of economic boom between the First and Second World War (∼1925-1940 CE), when large-scale built-in and leisure use of the lake has intensified. At that time, the Procladius-Microchironomus-Stempellina dominated community transformed to Procladius-Chironomus plumosus-type-Microchironomus community that coincided with land use changes, intensified erosion and water-level regulation in the lake with the maintenance of year-round high WL. This was followed by the impoverishment and population size decrease of the chironomid fauna and Procladius dominance since 1940 CE, without any recovery after 1994 CE despite the ongoing oligotrophication. Accelerated rate of change and turnover of the fauna was connected to an increase in the benthivorous fish biomass and eutrophication. The basin lost almost completely its once characteristic Stempellina species between 1927 and 1940 CE due to trophic level increase and seasonal anoxia in the Szemes Basin. Reference conditions for ecosystem improvement were assigned to 1740-1900 CE. We conclude that in spite of the ongoing oligotrophication, the re-establishment of the Procladius-Microchironomus-Stempellina assemblage is hampered, and requires fish population regulation.

Environmental behaviour of iron and steel slags in coastal settings.

Iron and steel slags have a long history of both disposal and beneficial use in the coastal zone. Despite the large volumes of slag deposited, comprehensive assessments of potential risks associated with metal(loid) leaching from iron and steel by-products are rare for coastal systems. This study provides a national-scale overview of the 14 known slag deposits in the coastal environment of Great Britain (those within 100 m of the mean high-water mark), comprising geochemical characterisation and leaching test data (using both low and high ionic strength waters) to assess potential leaching risks. The seaward facing length of slag deposits totalled at least 76 km, and are predominantly composed of blast furnace (iron-making) slags from the early to mid-20th Century. Some of these form tidal barriers and formal coastal defence structures, but larger deposits are associated with historical coastal disposal in many former areas of iron and steel production, notably the Cumbrian coast of England. Slag deposits are dominated by melilite phases (e.g. gehlenite), with evidence of secondary mineral formation (e.g. gypsum, calcite) indicative of weathering. Leaching tests typically show lower element (e.g. Ba, V, Cr, Fe) release under seawater leaching scenarios compared to deionised water, largely ascribable to the pH buffering provided by the former. Only Mn and Mo showed elevated leaching concentrations in seawater treatments, though at modest levels (<3 mg/L and 0.01 mg/L, respectively). No significant leaching of potentially ecotoxic elements such as Cr and V (mean leachate concentrations <0.006 mg/L for both) were apparent in seawater, which micro-X-Ray Absorption Near Edge Structure (µXANES) analysis show are both present in slags in low valence (and low toxicity) forms. Although there may be physical hazards posed by extensive erosion of deposits in high-energy coastlines, the data suggest seawater leaching of coastal iron and steel slags in the UK is likely to pose minimal environmental risk.

Characterization of the inhalable fraction (< 10 µm) of soil from highly urbanized and industrial environments: magnetic measurements, bioaccessibility, Pb isotopes and health risk assessment.

Soil in urban and industrial areas is one of the main sinks of pollutants. It is well known that there is a strong link between metal(loid)s bioaccessibility by inhalation pathway and human health. The critical size fraction is < 10 µm (inhalable fraction) since these particles can approach to the tracheobronchial region. Here, soil samples (< 10 µm) from a highly urbanized area and an industrialized city were characterized by combining magnetic measurements, bioaccessibility of metal(loids) and Pb isotope analyses. Thermomagnetic analysis indicated that the main magnetic mineral is impure magnetite. In vitro inhalation analysis showed that Cd, Mn, Pb and Zn were the elements with the highest bioaccessibility rates (%) for both settings. Anthropogenic sources that are responsible for Pb accumulation in < 10 µm fraction are traffic emissions for the highly urbanized environment, and Pb related to steel emissions and coal combustion in cement plant for the industrial setting. We did not establish differences in the Pb isotope composition between pseudo-total and bioaccessible Pb. The health risk assessment via the inhalation pathway showed limited non-carcinogenic risks for adults and children. The calculated risks based on pseudo-total and lung bioaccessible concentrations were identical for the two areas of contrasting anthropogenic pressures. Carcinogenic risks were under the threshold levels (CR < 10-4), with Ni being the dominant contributor to risk. This research contributes valuable insights into the lung bioaccessibility of metal(loids) in urban and industrial soils, incorporating advanced analytical techniques and health risk assessments for a comprehensive understanding.

Oral bioaccessibility of potentially toxic elements in various urban environmental media.

An important aspect of geochemical studies is determining health hazard of potentially toxic elements (PTEs). Key information on PTEs behaviour in the human body in case of their ingestion is provided with the use of in vitro bioaccessibility tests. We analysed and compared oral bioaccessibility of a wide range of PTEs (As, Cd, Ce, Cr, Cu, Hg, La, Li, Ni, Pb, Sb, Sn, Zn), including some that are not often studied but might pose a human health hazard, in soil, attic dust, street dust, and household dust, using Unified BARGE Method (UBM). Additionally, feasibility of usage of scanning electron microscope techniques in analyses of solid residuals of UBM phases was tested. Results show that bioaccessible fractions (BAFs) of PTEs vary significantly between individual samples of the same medium, between different media and between the gastric and gastro-intestinal phases. In soil, attic dust and street dust, bioaccessibility of individual PTE is mostly higher in gastric than in gastro-intestinal phase. The opposite is true for PTEs in household dust. In all four media, with the exception of Pb in household dust, among the most bioaccessible PTEs in gastric phase are Cd, Cu, Pb, and Zn. During the transition from the stomach to small intestine, the mean BAFs of most elements in soil, attic dust, and street dust decreases. The most bioaccessible PTEs in gastro-intestinal phase are Cu, Cd, Ni, and As. Micromorphological and chemical characterisation at individual particle level before and after bioaccessibility test contribute significantly to the understanding of oral bioaccessibility.

Hydrogeochemical signatures of spring water in geologically diverse terrains: a case study of Southern Western Ghats, India.

Out of 5 million Indian spring water systems, a few were characterised for hydrochemistry and freshwater potential. The present study focuses on analysing the hydrochemistry, discharge, and drinking/irrigation water quality of both cold and thermal spring clusters namely Southern Kerala Springs (SKS) and Dakshina Kannada Springs (DKS) of Southern Western Ghats, India. Currently, eleven springs from SKS and ten from DKS including one thermal spring (TS) with temperature ranges from 34 to 37 °C were considered. The study revealed that cold springs (CS) of SKS are Na-Cl type, while the thermal and cold-water springs in DKS are Na-HCO3 and mixing water type, respectively. Two distinct mechanisms predominantly define the hydro-chemical composition of the springs-SKS are influenced by precipitation, whereas DKS is likely by chemical weathering processes. While comparing the major ions and saturation indices of thermal springs (TS), it is evident that silicate minerals predominantly affect the chemical composition of water. CaCO3- is oversaturated in TS water and tends to precipitate as a scale layer. PCA showed that both geogenic and anthropogenic factors influence water chemistry. WQI categorized the CS in both the clusters are in the "Excellent" rank as compared to TS. Irrigation water quality signifies that the cold springs are only suitable for irrigation. Moreover, it is evident from the discharge that both SKS and DKS were rainfed in nature. Discharge monitoring designated that the CS could augment drinking water supplies in the nearby regions indicating the necessity of conservation and sustainable use considering future freshwater scarcity.

Estimating internal phosphorus loading for a water quality model using chemical characterisation of sediment phosphorus and contrasting oxygen conditions.

The Finnish Archipelago Sea (AS) has long been subject to intensive anthropogenic phosphorus (P) loading. The area suffers from seasonal hypoxia and cyanobacterial blooms despite reductions in nutrient discharge from the catchment and point sources. Internal loading may even dominate the P budget. Previous estimates of internal P loading have limitations (e.g., in spatial coverage and infrequent measurements). We present the first area-wide estimates of the magnitude of internal P loading based on the long-term release of P stored in the sediments. Modelling the internal P loading in the AS is challenging due to the complexity of biogeochemical processes in the sediment-water interface, as well as the heterogenic topography of the seafloor. Instead, we calculated estimates of internal P loading based on data from previous studies on sequential chemical extraction of sediment P, sediment physical characteristics (e.g., organic content, location of muddy seabed substrates), and near-bottom oxygen (O2) conditions. The estimates in three scenarios of contrasting O2 conditions were based on potentially mobile P pools in the sediments, recycled from sediment to water (i.e., loosely-bound or exchangeable P, P bound to reducible iron oxy(hydr)oxides, and labile organic P). The potentially mobile P pools were determined by chemical extraction methods (modified from Psenner et al., 1984 and Ruttenberg, 1992). The internal P loading under presumable O2 conditions was estimated to be fivefold that of waterborne P input to the AS; comparable to previous estimates for hypoxic areas in the Baltic Sea. Our estimates revealed wide spatial variability in the internal P loading, depending on O2 conditions and seabed sediment substrate. The site-specific P release estimates are included in a water quality model used by regional authorities, which increases the model's reliability for estimating the impact of human activities on the water quality across the AS.

Community-based, cost-effective multispecies mangrove restoration innovation to maximize soil blue carbon pool and humic acid and fulvic acid concentrations at Indian Sundarbans.

Sundarbans is the world's largest and most diverse contiguous mangrove ecosystem. In this pilot study, three plots (around 1 ha each) were selected, where one site (S1) had 1 year of community involvement, another site (S2) had a community network to support the restoration initiatives for 2 years, while a control site (C) was devoid of any post plantation community protection. Rhizophora mucronata (Rhizophoraceae), Sonneretia caseolaris (Lythraceae) and Avicennia marina (Acanthaceae) were planted at the sites in 2012. After 6 years (in 2017), at S1, the monitoring showed low survival rate for salinity-sensitive species, 2% for R. mucronata and 4% for S. caseolaris. At S2, R. mucronata has high survival rates, i.e. 71%, followed by S. caseolaris with 40%, whereas at C, the survival rate of both species was 0%. At S1 and C, the salinity-tolerant A. marina replaced the planted mangroves partially (S1) or entirely (C). At S2, available soil P increased by 17.5%, in 6 years, and the overall blue carbon pool showed a linear increase from 64.4 to 88.6 Mg C ha-1 (34.3% rise). S1 showed a minimum increment in P and the blue carbon pool (6.9% rise), while site C showed fluctuations in the blue carbon pool with only a 3.1% increase. Humic acid and fulvic acid concentrations in the S2 site indicate positive functional carbon sequestration in the edaphic environment. The community involvement increased the plantation cost (567.70 USD) of S2, in comparison to S1 (342.52 USD) and C (117.34 USD), but it has resulted in better restoration and survival of the mangroves. The study concludes that community participation for at least 2 years can play a significant role in the conservation of mangrove ecosystems and the success of restoration initiatives in tidal, saline wetlands and would aid in compliance with the United Nations Sustainable Development Goal 14 (Life Below Water) targets.

Metal record of copper-based antifouling paints in sediment core following marina construction and operation.

Marinas are central hubs of global maritime leisure and transport, yet their operations can deteriorate the environmental quality of sediments. In response, this study investigated the metal contamination history associated with antifouling paint uses in a sediment core collected from Bracuhy marina (Southeast Brazil). Analysis target major and trace elements (Cu, Zn, Pb, Cd and Sn), rare earth elements (REEs), and Pb isotopes. The modification in Pb isotopic ratios and REEs pattern unequivocally revealed sediment provenance disruption following the marina construction. Metal distribution in the sediment core demonstrates that concentrations of Cu and Zn increased by up to 15 and 5 times, respectively, compared to the local background. This severe Cu and Zn contamination coincides with the onset of marina operations and can be attributed to the use of antifouling paints.

Oxygenation of Earth's atmosphere induced metabolic and ecologic transformations recorded in the Lomagundi-Jatuli carbon isotopic excursion.

The oxygenation of Earth's atmosphere represents the quintessential transformation of a planetary surface by microbial processes. In turn, atmospheric oxygenation transformed metabolic evolution; molecular clock models indicate the diversification and ecological expansion of respiratory metabolisms in the several hundred million years following atmospheric oxygenation. Across this same interval, the geological record preserves 13C enrichment in some carbonate rocks, called the Lomagundi-Jatuli excursion (LJE). By combining data from geologic and genomic records, a self-consistent metabolic evolution model emerges for the LJE. First, fermentation and methanogenesis were major processes remineralizing organic carbon before atmospheric oxygenation. Once an ozone layer formed, shallow water and exposed environments were shielded from UVB/C radiation, allowing the expansion of cyanobacterial primary productivity. High primary productivity and methanogenesis led to preferential removal of 12C into organic carbon and CH4. Extreme and variable 13C enrichments in carbonates were caused by 13C-depleted CH4 loss to the atmosphere. Through time, aerobic respiration diversified and became ecologically widespread, as did other new metabolisms. Respiration displaced fermentation and methanogenesis as the dominant organic matter remineralization processes. As CH4 loss slowed, dissolved inorganic carbon in shallow environments was no longer highly 13C enriched. Thus, the loss of extreme 13C enrichments in carbonates marks the establishment of a new microbial mat ecosystem structure, one dominated by respiratory processes distributed along steep redox gradients. These gradients allowed the exchange of metabolic by-products among metabolically diverse organisms, providing novel metabolic opportunities. Thus, the microbially induced oxygenation of Earth's atmosphere led to the transformation of microbial ecosystems, an archetypal example of planetary microbiology.IMPORTANCEThe oxygenation of Earth's atmosphere represents the most extensive known chemical transformation of a planetary surface by microbial processes. In turn, atmospheric oxygenation transformed metabolic evolution by providing oxidants independent of the sites of photosynthesis. Thus, the evolutionary changes during this interval and their effects on planetary-scale biogeochemical cycles are fundamental to our understanding of the interdependencies among genomes, organisms, ecosystems, elemental cycles, and Earth's surface chemistry through time.

Geochemical evaluation and the mechanism controlling groundwater chemistry using chemometric approach and groundwater pollution index (GPI) in the Kishangarh city of Rajasthan, India.

This study is primarily focused on delving into the geochemistry of groundwater in the Kishangarh area, located in the Ajmer district of Rajasthan, India. In pursuit of this research goal, the sampling locations were divided into three parts within the Kishangarh region: Badgaon Rural (KSGR), Kishangarh Urban (KSGU), and the Kishangarh RIICO marble industrial area (KSGI). Various analytical methods have been executed to assess the suitability of groundwater for various purposes based on pH, electric conductivity, total dissolved solids, hardness, salinity, major anions, and cations. The ionic trend of anions and cations was found as HCO3- > Cl- > SO42- > NO3- > Br- > NO2- > F- and Na+ > Ca2+ > Mg2+ > K+, respectively. Applying statistical techniques such as principal component analysis (PCA) and Pearson correlation matrix analysis (PCMA) makes it evident that the physicochemical attributes of water sourced from the aquifers in the study area result from a blend of diverse origins. In addition, Gibbs, Piper, Durov, and scatter plots were used to assess groundwater's geochemical evolution. Piper plot demonstrated the two types of groundwater facies, Na-HCO3- and Na-Cl, implying significant contributions from evaporitic dissolution and silicate weathering. Also, the scatter plots have evaluated the impression of mine acid leachate, evaporitic dissolution, and silicate weathering to upsurge salt formation in the groundwater. The pollution risk evaluation within the study area was conducted using the groundwater pollution index (GPI). This index revealed a prominent concern for pollution, particularly in the northern segment of the study region. As a result, it can be inferred that the fine aeolian sand and silt formations in the northern part are relatively more vulnerable to contamination.

Forensic Geochemistry Reveals International Ship Dumping as a Source of New Oil Spill in Brazil's Coastline (Bahia) in Late 2023.

In the present study, we applied forensic geochemistry to investigate the origin and fate of spilled oils like tarballs stranded at the beaches of Bahia, in northeastern Brazil, in September 2023, based on their fingerprints. Saturated and aromatic compounds were assessed by gas chromatography, and the oceanic surface circulation patterns were deciphered to determine the geographic origin of the spill. Contamination by petroleum represents an enormous threat to the unique, species-rich ecosystems of the study area. The geochemical fingerprint of the oil spilled in 2023 did not correlate with those of previous events, including the one in 2019, the one in early 2022 in Ceará, and an extensive spill across the Brazilian Northeast in late 2022. However, the fingerprint did correlate with crude oils produced by Middle Eastern countries, most likely Kuwait. The oil of the 2023 spill had a carbonate marine origin from early mature source rocks. These findings, together with the moderate weathering of the 2023 tarballs and the ocean circulation patterns at the time of the event, indicate that the oil was discharged close to the shore of Brazil, to the east or southeast of Salvador, by a tanker on an international route in the South Atlantic.

Multivariate analysis applied to X-ray fluorescence to assess soil contamination pathways: case studies of mass magnetic susceptibility in soils near abandoned coal and W/Sn mines.

Determining the origin and pathways of contaminants in the natural environment is key to informing any mitigation process. The mass magnetic susceptibility of soils allows a rapid method to measure the concentration of magnetic minerals, derived from anthropogenic activities such as mining or industrial processes, i.e., smelting metals (technogenic origin), or from the local bedrock (of geogenic origin). This is especially effective when combined with rapid geochemical analyses of soils. The use of multivariate analysis (MVA) elucidates complex multiple-component relationships between soil geochemistry and magnetic susceptibility. In the case of soil mining sites, X-ray fluorescence (XRF) spectroscopic data of soils contaminated by mine waste shows statistically significant relationships between magnetic susceptibility and some base metal species (e.g., Fe, Pb, Zn, etc.). Here, we show how qualitative and quantitative MVA methodologies can be used to assess soil contamination pathways using mass magnetic susceptibility and XRF spectra of soils near abandoned coal and W/Sn mines (NW Portugal). Principal component analysis (PCA) showed how the first two primary components (PC-1 + PC-2) explained 94% of the sample variability, grouped them according to their geochemistry and magnetic susceptibility in to geogenic and technogenic groups. Regression analyses showed a strong positive correlation (R2 > 0.95) between soil geochemistry and magnetic properties at the local scale. These parameters provided an insight into the multi-element variables that control magnetic susceptibility and indicated the possibility of efficient assessment of potentially contaminated sites through mass-specific soil magnetism.