Geochemical Indicators Research Articles

Mechanism of arsenic accumulation in sediments of the northern China: Insight from provenance, weathering processes and paleoenvironmental changes

Fluctuations in sedimentary As burial have been reported throughout geological timescales, but detailed weathering pathways governed by climatic evolution are poorly understood. To this end, we reconstructed various climatic stages utilizing lithologies, geochemical indicators, and dating data and illustrated the physical–chemical pathways that affect As accumulation and release. The results revealed six climate changes. The climatic evolution was a consequence of the relative intensities of the East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM). Higher sedimentary As, Fe, and Feclay concentrations are observed in the cold-arid climates and suggest As accumulation occurred due to strong physical erosion. Moreover, correlations between Feclay and clay minerals indicate favorable clay minerals during cold-arid climates (e.g., illite, chlorite, and illite–smectite mixed layer) enhanced the accumulation of Fe-rich clay minerals and then As burial. In warm-humid climates, intense biogeochemical processes prevailed and contributed to crystalline Fe enrichment, which might accelerate As release. This analysis shows climate shifts alter solid As partitioning in sedimentary basins and potentially result in significant impacts with respect to global As contamination.

Electro-sequence valorization of specific enablers of aquifer vulnerability and contamination: A case of index-based model approach for ascertaining the threats to quality groundwater in sedimentary beds

This work was set up to appraise the quality of groundwater within a newly established university using index-based techniques and the intention is to generate vulnerability potential maps that can guide in avoiding vulnerable aquifer systems. The study used geo-electrical technology to evaluate the lithological sequence of the hydrogeological units and their first-and second-order geo-electric properties, as well as the geochemical constituents of groundwater. The results showed that the hydrogeological units are composed of sequences of sands, including fine to gravelly sands minimally laced with sandy clay, according to the results of geo-electrical technology. Layers 2 and 3 were accessible by the twenty VES (V1-V20) in which current gained access to designated economic and prospective aquifer systems. The aquifer systems considered have resistivity values ranging from 26.3 to 3576.5Ωm and mean value of 832.97Ωm. The five vulnerability models deployed showed very high spatial variability and moderate negative and positive binary correlations, construed to be due to subjectivity in the weight-rate assignment. The coefficients of variation (CV) from sensitivity analysis (SA) indicated variation in the vulnerability index due to topography (9.7%) and the impact of the vadose zone (4.3%), which are marginally higher than the 1.6% displayed by other parameters. The groundwater displayed WHO's disallowed concentrations of heavy ions, and the SA indicated that CV for the groundwater geochemical contamination is variably high in cadmium ions (140.9%) followed by manganese ions (132%) and copper ions (88. 2%) across the wells. The moderately variable contribution distributions across the wells are nickel ions (48.8%), lead ions (41.6%), chromium ions (39.8%) and iron ions (35.0%). All the geophysical and geochemical indices affirm that the groundwater is vulnerable and contaminated and therefore requires monitoring and management.

Search for the Substantiation of Reasonable Native Elemental Background Values and Reference Variables in Topsoil on Glaciogenic and Postglacial Deposits in a Vilnius Peri-Urban Area

Geochemical indices used to identify the emerging anomalies of potentially harmful elements in topsoil depend on background values (BVs). For urban sites, it is reasonable to estimate native BVs through the targeted selection of peri-urban sampling sites or by distinguishing a useful background subset (BS) within the peri-urban dataset. Here, the goals were to examine the influence of Quaternary deposits on various types of topsoil variables, identify the variables most helpful for cluster analysis intended for the choice of background subset (BS), and compare background values (BVs) based on different background subsets. Composite topsoil samples from a peri-urban area were used for the determination of the following variables: contents of 26 elements and components of the bulk mineralogical composition, as well as the sand, silt, and clay fractions and loss-on-ignition (LOI) at 550 °C and at 950 °C. Although Quaternary lithology influences topsoil elemental contents or granulometric fractions, percentages of illite, kaolinite, orthoclase, quartz, albite, dolomite, and LOI at 550 °C, the choice of BS, according to it, is not recommended, as BVs based on topsoil texture are superior. However, cluster analysis using topsoil fractions < 2, <63, and >63 μm or the contents of Al, Fe, K, Ti, Ga, Nb, Rb, and Si are preferable. It is recommended to use these reference variables for the selection of BS.

Geochemical Compositions of Size‐Fractioned Sediment Samples From the Yangtze and Yellow Rivers: Implications for Chemical Weathering, Fractionation Behavior of Provenance Tracers, and Sources of Radial Sand Ridges

AbstractRiver sediments are valuable archives of the environmental conditions within their catchments. The Yangtze and Yellow Rivers are the most active fluvial systems for sediment transport in East Asia, and they are regarded as potential sediment sources for the radial sand ridges (RSRs) in the southwestern Yellow Sea. We used the geochemical compositions of size‐fractioned sediment samples from the Yangtze and Yellow Rivers to characterize chemical weathering, the fractionation behavior of provenance tracers, and the sources of RSRs. For the Yangtze and Yellow River sediments, the (Rb + Sr)/Ti ratio is a reliable chemical weathering proxy that is grain‐size independent. The chemical indices of Chemical Index of Alteration, Rb/Sr, (Rb + Sr)/Ti, and acid‐leached elements from common grain‐size fractions together reveal that the Yangtze River basin undergoes stronger chemical weathering than the Yellow River basin, indicating that the chemical weathering is dominated by latitudinally‐dependent climatic variations. The dissolution and precipitation of amorphous Fe‐Mn oxides can result in the significant fractionation of La/Y, La/Sc, Nb/Co, La/Co, (La/Sm)N, (La/Yb)N, Ti/Sc, Zr/Y, Zr/Co, and Cr/Ta, whereas Zr/Ti and Zr/Nb are largely unaffected. Based on the robust provenance tracers of Zr/La, La/Hf, (La/Yb)N, Zr/Nb, Ti/Zr, and Hf/Ta, we conclude that the RSRs in the southwestern Yellow Sea are mainly derived from Yangtze River sediments, and that part of the clay fraction is from the Yellow River. In future research, we suggest that established geochemical indicators of chemical weathering and sediment provenance can be applied to the deposits of the Yangtze and Yellow River Deltas, the Yellow Sea, and the East China Sea.

Extraction and imaging of indicator elements for non-destructive, in-situ, fast identification of adverse geology in tunnels

The lag in quantitative methods and detection techniques for geologic information has resulted in time-consuming and human-experienced geologic analysis in tunnels. Geochemical indicators of rocks can be used to identify adverse geology and to explain the intrinsic causes of damage to normal rocks. This study proposes a method to identify adverse geology by extracting and imaging the indicator elements. The mapping relationship between rock components and geologic bodies is quickly determined by indicator element extraction based on factor analysis, and then the data are gridded for image output. The location and size of the target adverse geology are visually identified through the distribution images of the indicator elements, thus reducing data dimensions and analysis time. A non-destructive, in-situ and fast element detection technique in tunnels was adopted to speed up the process of geology identification. The accuracy of the detection was validated by comparing field and laboratory test results. This study further confirms and refines the previous research, and the results provide references for geological, mining and underground projects.

The mechanism of organic matter accumulation in the archipelago marine sediments: Insights from the Middle Devonian Givetian mudstone with low TOC in the Youjiang Basin, South China

Despite the fact that the mean values of total organic carbon (TOC) content in the Luofu Formation are relatively low, at or below 1.0 wt%, it still has the potential to be a veritable source rock. To elucidate the influences of various paleogeographic factors on sedimentary environments, 25 samples from Well A on the slope and 32 samples from Well B in the basin centre were selected for study. The samples were analyzed by thin section microscopy and field emission-scanning electron microscopy, along with X-ray diffraction and geochemical analyses (TOC content, sulfur content, organic petrography, inorganic carbon isotope and major and trace elements) in order to understand variations in and controls on the mineralogy, lithofacies, depositional environments, as well as the organic matter accumulation mechanism. The results of our study indicate that mudstone of the Luofu Formation was deposited into 4 lithofacies groups, namely as the siliceous lithofacies, mixed lithofacies, argillaceous lithofacies and calcareous lithofacies. The siliceous lithofacies mudstone was developed in the deep-water columns, while the mixed lithofacies mudstone was deposited on shallow-water columns. The organic matter accumulation model of the Luofu Formation can be further divided into the following four stages, each with its own unique characteristics: (1) The organic matter accumulation was caused by the relatively high productivity and dysoxic basin bottom water columns; (2) The organo-mineral complexes may promote the organic matter accumulation to some extent; (3) The organic matter enrichment was facilitated by the dysoxic/anoxic conditions and relatively high productivity from the basin to the slope; (4) The organic matter was preserved at shortened exposure duration of oxic conditions on the slope. The correlations between various geochemical indicators (redox, paleoproductivity and terrestrial debris flux) and TOC content suggest that oxic water columns and low productivity are the main reasons for the widespread mudstone with low TOC. The organic-rich mudstone, as the target stratigraphic section for exploration, may be deposited in the basin bottom water columns away from upwelling and close to hydrothermal activity in stage 3.

Ecological and geochemical assessment of soil cover on the territory of Ufa city

The relevance. The need for constant monitoring of the state of natural environments because of Ufa increasing industrialization. This study is especially relevant due to the presence of enterprises of various industries (petrochemical, energy, metal construction, timber processing, chemical) located on a fairly small territory of the millionaire city. The aim. To determine the degree of technogenic pollution of the soil cover from industrial facilities in the study area. It is necessary to assess the impact of industrial emissions, as well as emissions from stationary and mobile sources for development of measures aimed at reducing the impact of chemical elements on the environment. Methods. Instrumental neutron activation analysis, atomic absorption spectroscopy, kappametry, mathematical statistics, mapping (spatial distribution of indicator geochemical indicators and content of the main pollutants). Results. The paper introduces the results of the analysis of the content of 29 chemical elements in the soil cover on the territory of Ufa according to the study of 104 samples. For each industrial area of the city, the priority elements-pollutants from the list of the analyzed ones were identified. Areas with high traffic congestion, as well as areas near oil refineries, are characterized by increased concentrations of As and LREE group (La, Ce, Nd). Elevated levels of Br and Sc are observed in areas near energy complexes. Increased concentrations of REE (Nd, Tb, Lu) were detected around the objects of the timber industry complex. A special situation is observed with the concentrations of some metals (Cr, Zn, Co). The entire territory of the city is characterized by increased concentrations of elements of the transition metal group due to the presence of a large metalworking complex and heavy automobile traffic. Using statistical methods of data interpretation, associations of chemical elements were identified and divided by possible genesis: mainly natural (Ca-Sr), mixed (Cs-Rb, Br-Ta-Na), mainly technogenic (Sb-Zn, Ba-As-Cr-Hg, Th-Lu-Hf-Yb, Ce-La-Nd). The constructed maps-schemes of spatial distribution, the total indicator of pollution and magnetic susceptibility determined that the territory of Ordzhonikidze district and the territory of the Dema railway station can be considered as the most susceptible to anthropogenic influence.

Unraveling the early Paleozoic tectonic history of the South Qinling Belt: Evidence from geochronology, geochemistry, and Sm-Nd isotopes of meta-sedimentary rocks

The determination of the petrogenesis and age of meta-sedimentary rocks plays a crucial role in enhancing our understanding of regional tectonic evolution. In this study, we conducted comprehensive geochemical, zircon U-Pb, and Sm-Nd isotope dating analyses of the biotite gneiss of the Changjiaoba group to investigate the tectonic evolution of the South Qinling belt. The age range of detrital zircons from the biotite gneiss was estimated to be 446–2798 Ma, with prominent peaks observed at approximately 454, 660, 790, 1998, and 2770 Ma. The earliest data indicate that the final sedimentary age of the Changjiaoba group corresponds to the late Ordovician. The protoliths of the biotite gneiss were argillaceous rocks, classified as parametamorphic rock. The chondrite-normalized rare earth element (REE) diagram exhibited right-inclined patterns with negative Eu anomalies. The upper continental crust (UCC)-normalized trace element patterns exhibited insignificant enrichment of Ba, Sr, and K; negative anomalies of Hf, Th, U, and Ti; and depletion of Cr and Ni. Geochemical indicators suggest that the precursor sediments are felsic rocks that have undergone moderate weathering. The εNd (t) values of the biotite gneiss (−10.2 to −3.4) suggest a mixture of a few juvenile crust components and abundant ancient material, indicating an arc-realted setting. Collectively, our findings suggest that the primary material sources of the Changjiaoba group were predominantly the North Qinling belt during the Paleozoic and the Yangtze block during the Neoproterozoic. The tectonic setting discrimination diagrams imply that the biotite gneiss were formed in an active continental margin environment, supporting the notion of the northward oceanic subduction during the early Paleozoic. In conclusion, our study provides valuable insights into the composition and deposition history of the Changjiaoba group in the South Qinling belt, contributing to our understanding of the regional geology.

Assessment of potentially hazardous elements in soils of the Boyacá industrial corridor (Colombia) using GIS, multivariate statistical analysis, and geochemical indexes

In the industrial corridor of Boyacá, Colombia, population growth is accompanied by anthropogenic activities such as industrial operations, vehicle exhaust fumes, mining, smelting, atmospheric deposition, and excessive use of chemical products to promote crop growth. These activities are known to have a significant impact on urban and rural soils, contributing significantly to elevated concentrations of potentially hazardous elements in the environment. This industrial corridor is an area of economic and social development that needs to provide reference information that will allow us to know the state of soil quality to preserve and manage the public and geoenvironmental health of this region. Anthropogenic activities have contributed to the accumulation of potentially hazardous elements in the environment, affecting various levels of life and creating risks with economic and social implications. However, igneous activity or detrital deposition also enriches soils and creates geochemical anomalies in specific locations. In these cases, the identification of potentially hazardous elements involves the determination of likely sources of contamination and their relationship to the geological setting. In this study, the concentrations of As, Cd, Pb, Mn, Fe, Zn, Hg, Cu and Ni were determined in eighty-one soil samples from the Boyacá industrial corridor (Colombia). The sequential trend of the concentrations of potentially hazardous elements was as follows: Fe > Mn > Zn > Ni > Cu> Pb > As > Cd > Hg. Furthermore, the application of spatial analysis criteria in GIS software with multivariate statistical tools and geochemical indices allowed the identification of anthropogenic and geogenic sources. Most of the potentially hazardous elements were found in soils exposed to industrial and agricultural activities, except for iron. This element showed low variability in all samples, regardless of the geological formations. Due to the lack of reference values for potentially hazardous elements in Colombia, the concentrations were compared with the environmental standards of the Environmental Protection Agency (EPA) and the Ecuadorian Ministry of Environment, Water and Ecological Transition (MAE). The results demonstrate the complexity of the soil and represent the first exploratory study of potentially hazardous elements in this industrial corridor. These results are the starting point for the establishment of geochemical background lines in Colombia and for inspection policies for areas where productive activities converge.

Late Quaternary palaeoenvironmental reconstruction of a Chobe Enclave landform (NW Botswana) based on pedological and geochemical indices

Late Quaternary palaeoenvironmental reconstruction of a Chobe Enclave landform (NW Botswana) based on pedological and geochemical indices

Zoning of highways of the Cherkasy region according to the degree of formation of ecosystem relations

The research is due to the great attention paid to the preservation and restoration of biodiversity in the countries of the European Union. Purpose. Carrying out zoning of the Cherkasy region according to the degree of completeness of the formation of roadside landscapes ecosystemsю Methods. From a methodological point of view, zoning is considered as one of the main methods of geographical analysis a nd synthesis. Zoning performs the function of a general geographic method of organizing spatial diversity in the geographic envelope and systematizing territorial formations at the regional level, which makes it an essential element of a systematic approach in geography. Results. The monitoring parameters of the infrastructure components of the main highways of the Cherkassy region (Kyiv-Odesa and Vinnytsia-Uman) used by us can be used for zoning, provided they are combined into logically formed factor groups. In particular, we combined all the initial parameters into the following groups of factors: natural-geographic factor: geolocation (geographic coordinates), air temperature and humidity, natural radiation background; degree of anthropogenic impact: noise level, dustiness, some geochemical indicators, proximity (or remoteness) of the road surface from agricultural land; the degree of manifestation of ecosystem relations: the number of plant species and their recurrence, the presence of invasive species and those that are indicators of salinity and waterlogging, the presence of species included in the National Catalog of Biotopes of Ukraine. Based on the list of main groups of factors, the main indicator of zoning will be the degree of completeness of the formation of roadside ecosystems. Conclutions. Taking into account the activation of ruderal flora at the exits from gas stations, or on remote sections of highways, it can be asserted that in these locations the Le Chatelier-Brown principle is fully in effect, according to which the biosphere compensates for the harmful effects from the outside with its diversity. The author sees prospects for further research in the expansion of the list of objects, in particular, it will be very interesting to investigate the formation of ecosystem relations on secondary communication routes.

Source variations in volatile contents of Bransfield Strait back-arc and Phoenix/West Scotia mid-ocean ridge lavas, northern Antarctic Peninsula

We present the first volatile contents (H2O, CO2, Cl, F, S) of young (< 6 Ma) submarine basaltic glasses from the Phoenix and West Scotia mid-ocean ridges and the Bransfield Strait back-arc of the South Shetland subduction zone in the Antarctic Peninsula.The volatile contents of the MORB glasses correspond well with those of published Pacific MORB and reflect covariations in source enrichment and extent of melting. Our results support the hypothesis that decreasing spreading rates at the Phoenix Ridge resulted in preferential melting of less abundant enriched MORB mantle, due to its greater fertility and higher volatile contents, relative to the more abundant depleted MORB mantle.The volatile contents of the Bransfield Strait back-arc glasses correlate with geochemical indicators of subduction processes and reveal an along-axis spatial distribution consistent with a toroidal inflow of sub-slab asthenosphere around the edges of the subducting plate into the mantle wedge. This inflow should be considered when assessing spatial and geochemical variability at subduction zones, particularly those with slab windows and tears.A small group of Bransfield Strait samples have volatile contents that do not correlate with geochemical signals of subduction influence. We speculate that these samples reflect flux melting of residual enriched mantle brought beneath the Bransfield Strait via corner flow following recent alkaline magmatism in the far eastern regions of the Antarctic Peninsula.Our new data on lavas from the W7 segment of the West Scotia Ridge reveal their source was significantly affected by subduction processes. Unexpectedly, these lavas have CO2-H2O pressures of vapor saturation that suggest they were collected in-situ and erupted relatively recently (∼6 Ma), at odds with previous interpretations of their origins. We suggest they originated from a subduction-modified mantle (lithosphere or asthenosphere) left behind by the eastward-migrating South Sandwich subduction zone sometime over the past ∼30 Myr. These lavas demonstrate the long-lasting effects of subduction processes on the upper mantle and their potential to influence melt compositions even in non-subduction environments today.We use the compositions of lavas from the Phoenix Ridge and Bransfield Strait to estimate mantle potential temperatures; our results agree well with global estimates for mid-ocean ridges and subduction zones, respectively.

Assessment of heavy metal contamination of sediments in popular tourist beaches of the Kerala State, southern India: Implications on textural and mineralogical affinities and mitigation

Beaches form one of the most contaminated sedimentary environments by a myriad variety of anthropogenic activities, including tourism and recreational activities. The concentrations of metals and their pollution levels were studied for four tropical tourist beaches in Kerala state, Southern India. Bulk geochemical and mineralogical analyses of 16 sediment samples were performed to determine the environmental status and the environmental risk level using various geochemical indices. Based on the enrichment of TiO2 and SiO2 concentrations, the samples were grouped into ilmenite-rich samples (IRS) and quartz-rich samples (QRS) respectively and the geochemical signatures are significantly different. Mineralogically, the IRS group is dominated by ilmenite, quartz, sillimanite, zircon and rutile while the QRS group consists of quartz, spinel and calcite and garnets are common in both groups of sediments. Despite the variation in the trends of pollution indices, it has been found that Kovalam beach sediments are enriched with W, Th and U where, IRS with enrichment of W, U and Th while QRS only enriched with W and Th and not U. The mineralogical affinity of W with secondary tungsten-bearing minerals has been documented by the XRD analysis and these metals are mainly controlled by the geogenic sourced minerals. However, in terms of ecological risk, Pb, As and Cu have a considerable to moderate risk in both groups of sediments. Overall, both group of sediments shows a moderate risk. Based on the biological effect assessment the elements of concern are Pb and Zn in IRS and possible effect by the Cr, Cu and As in IRS and only by Cu in QRS. Though the prevalence of geogenic and anthropogenic processes and influences of metal enrichments are documented by the study, their relative influences, mobility and bioavailability need to be systematically studied.

Middle Permian astronomically forced upwelling in the Yangtze carbonate platform: Implications for organic matter preservation and benthic biomass

The continental shelf and slope, with upwelling systems, are usually accompanied by the formation of oxygen minimum zones, thereby stimulating marine paleoproductivity and promoting organic matter (OM) enrichment. However, due to a more oxygen-enriched environment, a distinct paleoecological characteristic, and the uncertainty of upwelling effects, it remains ambiguous whether a similar mechanism of OM preservation occurs in the adjacent carbonate platform. Here, limestone–marl alternations (LMAs) that developed in the Yangtze Carbonate Platform (YCP) during the Middle Permian were selected as the research object and compared with the chert–mudstone alternations developed on the Lower Yangtze continental shelf (LYCS). Both sets of rhythmites belong to the contemporaneous products of the Permian Chert Event in South China.Considering that the Middle Permian rhythmites in South China contain the Milankovitch record and that upwelling was controlled by astronomically forced monsoons, this study investigated the impact of upwelling on the carbonate platform by adopting astronomical cycle research. Based on GR data, a framework of astronomical cycles was established. The suboxic to anoxic conditions of the YCP are supported by evidence from syngenetic pyrite framboids, Ce/Ce* ranges, and UEF–MoEF covariation. Upwelling geochemical indicators and the detection of a pivotal (∼210-kyr) astronomical cycle regarding upwelling indicate that the YCP was affected by upwelling. The paleoproductivity/OM/fossil-related data exhibit this ∼210-kyr astronomical cycle, and the correspondence between the converted AMs determines that upwelling enhanced marine primary paleoproductivity and OM preservation. However, the intensities of short eccentricity cycles exceed those of the ∼210 kyr cycle in the time series analyses of data from the nearshore YCP. Additionally, the covariations between the upwelling proxy and total fossil content confirm the impact of upwelling on biomass of benthic organisms. Therefore, the (monsoon-driven) upwelling system in the continental shelf can extend to the carbonate platform. After reaching the platform, under the control of a (an) (astronomically forced) climatic–oceanic system, limited upwelling can stimulate primary productivity and marine OM preservation; however, upwelling reduces biomass in the bottom water. In the nearshore side of the platform, detrital dilution likely replaces upwelling as the primary stimulus for productivity. Moreover, this study reveals and explains the ∼200-kyr cycles in the Permian strata of South China for the first time.

Metasomatism and depletion of the southern Gawler Craton from combined mantle xenocryst and AusLAMP magnetotelluric data

Metasomatised mantle is considered a prerequisite for the formation of many major ore deposits. Since magnetotellurics (MT) is strongly sensitive to mantle metasomatism, MT is a useful tool for analysis of mineral systems that incorporate a metasomatised mantle as a key ingredient. In this work, we combine recently reported kimberlite-hosted mantle xenocryst data from the southern Gawler Craton and Adelaide Superbasin with AusLAMP MT models. We find good correlations between mantle MT conductors and geochemical indicators of mantle metasomatism from clinopyroxene xenocrysts, with the most metasomatically enriched lithospheric mantle beneath the Adelaide Superbasin and more depleted mantle beneath the Gawler Craton. There is a significant step in lithospheric thickness across the Adelaide Superbasin, and particularly around the Terowie kimberlite cluster. Combined with the fertile mantle, this helps explain this region’s prospectivity for sediment-hosted copper deposits. High mantle resistivities and depleted geochemical compositions towards the central Gawler Craton on and north of the Eyre Peninsula are consistent with melting of previously metasomatised mantle, including during production of the Gawler Range Volcanics and Hiltaba Suite Large Igneous Province. Most of the major iron oxide copper gold (IOCG) and gold deposits in the region lie on the edge of this zone of mantle melting, consistent with mineral systems models that require melting of previously metasomatised mantle in the generation of these deposits.

Features of Using the Lithogeochemical Indicators for the Reconstruction of Paleoclimate and Composition of Demolition Sources in the Late Jurassic-Lower Cretaceous West Siberian Sedimentary Basin

For the rocks of the Upper Jurassic-Lower Cretaceous Bazhenov formation, a significant positive linear dependence of the Th, Hf, Sc, La content on the Al2O3 content was revealed, and their terrigenous genesis was confirmed. It has been determined that the samples in which the distribution of the values of the Sc/Al2O3 and La/Al2O3 ratios does not satisfy the linear dependence are mixed clayey-siliceous rocks with a P2O5 content 1 mas. % or substantially pyritized (in which the content of pyrite exceeds the content of S and C/S ≤ 1), as well as siliceous mudstones with a SiO2 content 70 mas. % by weight. It is concluded that before analyzing geochemical indicators for reconstructing the conditions of formation of the Bazhenov formation, in addition to carbonated rocks, rocks of the above types, as well as rocks that have undergone late diagenetic kaolinization, should be excluded from the analysis. The conditions of formation of the studied deposits were reconstructed based on the analysis of the values of a number of geochemical modules and indicators. As a result of the study of CIA, CIW variations, it was confirmed that the climate in the Late Jurassic-Early Cretaceous period in the West Siberian sedimentary basin was warm, semiarid. It was revealed that during the entire period under review, it did not change significantly. For the deposits of the Bazhenov formation, a number of indicators such as (La/Yb)N, Eu/Eu*, as well as the distribution of trace element content values on the triangular diagram Th‒La‒Sc, suggest that in the central and southeastern regions of the formation distribution area, the sources of demolition of the mafic composition prevailed.

Ecological risk assessment of heavy metals in the coastal sediment in the South-western Bay of Bengal

Dynamic coastal waters are often polluted by chemical pollutants, affecting coastal ecosystems. A total of four scientific coastal cruises up to 10 km offshore from the coastline along the Chennai-Puducherry coast during 2019-20 were conducted. This study examined the spatiotemporal distribution of heavy metals (Cr, Cu, Pb, Cd, Ni, Zn, As, Co, Mn) in the coastal sediments using various geochemical indices, including the Geo-accumulation Index (Igeo), Enrichment Factor (EF), Contamination Factor (CF), and Ecological Risk Index (ERI), to understand the impacts, environmental risks, and pollution status in coastal and marine systems. The heavy metal concentrations of Cr, Cu, Pb, Cd, Ni, Zn, As, Co, and Mn in sediments are 16.48-74.70 μg/g, 2.01-3.78 μg/g, 1.37-17.54 μg/g, 0.20-21.76 μg/g, and 5.73-40.53 μg/g, 4.73-53.54 μg/g, 2.09-28.18 μg/g, 1.80-9.02 μg/g, 70.27-346.22 μg/g, respectively. The Igeo results revealed that none of the metals reached up to the contamination level except for Cd and As which showed a slightly contaminated level of the sediment. ERI indicated that coastal sediments are at moderate to high ecological risk from heavy metals. This study will help policymakers make informed decisions for combating or remediating metal pollution to safeguard the coastal environment.

Assessment of heavy metals bioaccumulation in Silver Birch (Betula pendula Roth) from an AMD active, abandoned gold mine waste.

Acid mine drainage (AMD) is generally outlined as one of the largest environmental concerns, characterized by very low pH value of mine waste, heavy metals and high sulphate content. This extremely hostile environment reduces plant ability to develop and grow. Present study focuses on a silver birch (Betula pendula Roth), a pioneer species that grows on an extremely hostile gold mine waste, to investigate the bioaccumulation of rare metals (thallium (Tl) and indium (In)), as well as nine other more common heavy metals (bismuth (Bi), cadmium (Cd), cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), nickel (Ni), silver (Ag) and zinc (Zn)), and to asses phytoextraction and phytostabilization potential of silver birch. Additionally, parameters determining AMD process and overall contamination (pH, electrical conductivity (EC), sulphates (SO42-), arsenic (As), iron (Fe), oxidation-reduction potential (ORP), turbidity, dissolved oxygen (DO), total dissolved solids (TDS), acidity, hardness, X-ray diffraction (XRD) and radioactivity) were determined in mine waste and drainage water samples. To assess the heavy metals bioaccumulation and mine waste status, statistical geochemical indices were determined: bioaccumulation factor (BCF), pollution load index (PLI), geochemical abundance index (GAI) and exposure index (EI). The results show that silver birch bioaccumulates the essential elements Cu, Ni, Mn and Zn, and the nonessential elements Tl (average BCF = 24.99), In (average BC = 23.01) and Pb (average BCF = 0.84). Investigated mine waste was enriched by Bi, Ag and Cd according to positive values of GAI index. Present research provides a novel insight into bioaccumulation of nonessential heavy metals in silver birches who grow on the extremely hostile mine waste, and they exhibit significant phytoremediation potential.

Paleodepositional environment and hydrocarbon generation potential of the Paleogene lignite in the Barmer Basin, Rajasthan, India

The Barmer Basin in Rajasthan is considered one of the most important petroliferous sedimentary basins of India. Apart from a hydrocarbon-producing source rock, the basin also hosts some significant lignite deposits of Giral fen and Kapurdi bog developed during the late Paleocene to early Eocene, being currently under exploitation. Applying organic petrology, geochemical, mineralogical techniques, and Rock-Eval pyrolysis on samples obtained from seams in both mines, the paleodepositional settings in both areas were reconstructed, and the hydrocarbon generation potential was assessed. The Tmax (377–427 °C) and PI (0.01–0.09) values in the studied samples from the Barmer Basin indicate an immature nature of the organic matter. HI values range from 66 to 476 mg HC/g TOC, revealing that the Giral and Kapurdi lignite contains mostly Type III and mixed Type II-III kerogen and can generate mainly gaseous hydrocarbons, although few samples have liquid hydrocarbon generation potential. Significant values of TOC (20–60 wt%) reveal that they may act as a good source of hydrocarbons and make them favourable for the generation of hydrocarbons. The concentrations of major oxides and selected trace elements indicate that the Giral and Kapurdi lignite was developed in warm humid to some extent arid warm climate and oxic conditions prevailed in the basin. Petrographic indices suggest the peat accumulation occurred in a dry forest mire under limnic to limnotelmatic conditions. The indicators further suggest the lignite originated from the bog and fen under mesotrophic to ombrotrophic hydrological condition. The Giral and Kapurdi lignite were determined to be ortho-lignite or low-rank lignite C rank, immature for hydrocarbon generation. The lignite derived mainly from herbaceous vegetation with a higher contribution of woods in the Giral fen compared to the Kapurdi bog. Geochemical indicators suggest the presence of freshwater conditions and a shift from freshwater to brackish water conditions within the basin.

Integrated surface geochemical and seismic surveys for hydrocarbon exploration - A case study from southern Poland

Surface geochemical surveys were carried out in the Pawłosiów area in the eastern part of the Carpathian Foredeep. The research included an analysis of the molecular composition of soil gas samples as well as measurements of the calcite content, magnetic susceptibility and pH of soil samples. The results obtained were integrated with a geological-seismic model. Changes in the concentrations of total alkanes C2–C5 in relation to changes in indirect geochemical indicators showed “compensatory” character. This means that in places where alkane concentrations were increasing, negative anomalies of magnetic susceptibility and a decrease in pH values were observed. It may be related to the intensity of the oxidation processes or reduction of the magnetic minerals in, as well as the reduced permeability of, the Miocene layers in the zones analysed. Moreover, the complex geochemical-geophysical interpretation showed a zone of anomalous values of the total C2–C5 alkanes in the Pawłosiów area, which is suitable for prospecting. The research performed proved that a thorough analysis of the seismic record allowing subtle DHI anomalies appearing within the Miocene formations to be located, combined with the use of direct and indirect geochemical indicators, can help in identifying an area in terms of hydrocarbon potential. This applies in particular to this type of foreland basin, within which geological formations lie flat, and positive structures (anticlines) are hardly visible in seismic sections. In this type of structure, hydrocarbons can be accumulated in traps of a hybrid character (conventional and unconventional). The extensive zone of geochemical and geophysical anomalies found in the area of Pawłosiów may indicate the presence of this type of hydrocarbon accumulation.Comprehensive research, including direct and indirect geochemical methods in combination with a seismic survey, allows for a better assessment of the hydrocarbon potential of the studied area.