Search Results (17)

The Permian Qipan Formation (P_1-2q) is the aim horizon for hydrocarbon source rocks in the piedmont area of southwestern Tarim Basin. In the present study, the depositional environment and geochemical characteristics of muddy hydrocarbon source rocks of P_1-2q were systematically evaluated using total organic carbon (TOC), Rock-Eval pyrolysis, vitrinite reflectance (Ro), reflected light microscopy, main and trace element, and biomarker parameters of 167 outcrop samples and 176 core samples. The TOC of P_1-2q is primarily concentrated within the range of 0.36% to 2.77%, with an average of 1.58%. This suggests that the overall evaluation of the hydrocarbon source rock is fair to good. The source rocks of P_1-2q predominately contain Type III and Type II₂ kerogen. The overall Tmax values of P_1-2q hydrocarbon source rocks are notably elevated, with the majority exceeding 490 °C or falling between 455 °C and 490 °C. The Ro value is between 0.90% and 2.00%, indicating that the maturity has reached a high, over-mature evolutionary stage. The trace element and biomarker parameters indicate that hydrocarbon source rocks of P_1-2q are predominantly slightly oxygen-rich, with a minor anoxic component. The asymmetric ‘V’ arrangement of the C₂₇-C₂₉ regular steranes indicates that the hydrocarbon parent material is predominantly derived from algae or aquatic organisms, with varying degrees of mixing with organic matter of terrestrial origin. The study of source rock geochemistry of the P_1-2q makes the exploration target of the southwest depression of the Tarim Basin more accurate in the complex tectonic geological environment. Full article

The Carboniferous-Permian coal measure strata in the Qinshui Basin exhibit highly lithium (Li) enrichment, with substantial exploitation potential. To further explore the enrichment mechanism of lithium in coal measure strata, the No. 15 coal of the Taiyuan Formation from the Gaoping mine is taken as the research object, and its mineralogical and geochemistry characteristics are evaluated using optical microscopy, X-ray diffraction, scanning electron microscopy, inductively coupled plasma mass spectrometry, X-ray fluorescence, and infrared spectral. The results show that the No. 15 coal is semi-anthracite coal with low moisture, low ash, low volatility, and high sulfur. Organic macerals are primarily vitrinite, followed by inertinite, and liptinite is rare; the inorganic macerals (ash) are dominated by clay minerals (predominantly kaolinite, cookeite, illite, and NH₄-illite), calcite, pyrite, quartz, siderite, gypsum, and zircon. The average Li content in the coal is 66.59 μg/g, with higher content in the coal parting (566.00 μg/g) and floor (396.00 μg/g). Lithium in coal occurs primarily in kaolinite, illite, cookeite, and is closely related to titanium-bearing minerals. In addition, Li in organic maceral may occur in liptinite. The No. 15 coal was formed in the coastal depositional system, and the deposition palaeoenvironment is primarily a wet–shallow water covered environment in open swamp facies; the plant tissue preservation index is poor, and aquatic or herbaceous plants dominate the plant type. The reducing environment with more terrestrial detritus, an arid climate, and strong hydrodynamic effects is favorable for Li enrichment in coal. The results have important theoretical significance for exploring the enrichment and metallogenic mechanisms of Li in coal. Full article

Lake Kolon (Hungary), situated in the middle of the Turjánvidék area between the saline lakes of the Danube valley and the Homokhátság, is one of the most significant natural aquatic habitats in the Danube–Tisza Interfluve region. The central question of this study is how the lake changed, and how environmental factors and human activities have influenced these paleoenvironmental changes in Lake Kolon. A multiproxy analysis of a core sequence (loss on ignition, grain size, magnetic susceptibility, and geochemistry) provided crucial insights. Notably, correlations are observed in the following relationships: (1) clay, organic matter, and elements derived from organic sources, such as Na, K, and Zn; (2) MS, sand, inorganic matter, and elements originating from inorganic sources, such as Fe, Al, Ti, Na, K, and P; and (3) carbonate content and elements originating from carbonate sources, such as Ca and Mg. The lake’s paleoenvironment underwent significant changes in the past 27,000 years. Late-Pleistocene wind-blown sand provided the bottom for an oligotrophic lake (17,700 BP), followed by a calcareous mesotrophic Chara-lake phase (13,800 BP). Peat accumulation, along with the eutrophic lake phase, began at the Pleistocene–Holocene boundary around 11,700 BP. From 10,300 BP, with the emergence of an extended peatland phase, the percentage of organic matter (peat) increased significantly. Anthropogenic changes occurred from around 9000–8000 BP due to the different emerging cultures in the Carpathian basin, and from 942–579 BP due to the Hungarian settlements and activity nearby, respectively. Full article

In Qinglong ore field, the paleo-oil reservoir is found to be associated with antimony deposits, and they have a close genetic relationship. In this study, the aromatics geochemistry of paleo-oil reservoir bitumen was studied to further discuss the thermochemical sulfate reduction (TSR) reaction and the mechanism of antimony mineralization. A total of 124 aromatic compounds were identified by gas chromatography–mass spectrometry (GC–MS) analysis in bitumen samples, including abundant phenanthrene series, dibenzothiophene series, fluoranthene series, chrysene series, and a small number of fluorene series, naphthalene series, dibenzofuran series, biphenyl series, and triaromatic steroid series. Aromatic parameters such as trimethylnaphthalene index (TMNr), methylphenanthrene index (MPI), methylphenanthrene distribution fraction (MPDF, F₁, and F₂), methyldibenzothiophene parameter (MDR), C₂₈TAS-20S/(20R + 20S), and benzofluoranthene/benzo[e]pyrene indicate that the Qinglong paleo-oil reservoir is in over maturity level. The abundance of phenanthrene and chrysene aromatic compounds and a small amount of naphthalene series, benzofluoranthene, fluoranthene, pyrene, anthracene, retene, perylene, and biphenyl suggest that the organic matter source of the paleo-oil reservoir was mainly low aquatic organisms, mixed with a small amount of higher plant. They detected a certain number of compounds, such as retene, triaromatic steroid series, and perylene, the ternary diagram of DBF–DBT–F and binary plot of Pr/Ph–DBT/P, DBT/(F + DBT)–DBF/(F + DBF), and Pr/Ph–DBT/DBF reveal that the source rock of the paleo-oil reservoir was formed in the marine environment of weak oxidation and weak reduction. The comprehensive analysis shows that the Qinglong paleo-oil reservoir originated from Devonian source rocks, just like other paleo-oil reservoirs and natural gas reservoirs in the Nanpanjiang basin. Abundant dibenzothiophene series were detected, indicating that the paleo-oil reservoir underwent a certain degree of TSR reaction. We believe that the gas reservoir formed by the evolution of the oil reservoir in the ore field participated in antimony mineralization; that is, hydrocarbon organic matter acted as a reducing agent and transformed SO₄²⁻ in oilfield brine into H₂S through TSR, providing reduced sulfur and creating environmental conditions for mineralization. Full article

Human impacts cause significant problems for shallow lakes in the karst regions of South China. In recent years, the ecological issues related to managing and restoring these critical aquatic ecosystems have come to the fore. Lingshui Pool (LSP) is one of the most-studied spring-fed lake ecosystems in south China, and it has well-preserved chronological profiles. The LSP was a very shallow lake before dam construction in 1962. Due to the dam’s construction, rapid development and urbanization, this important freshwater ecosystem has suffered severe eutrophication and environmental degradation. In order to determine the environmental effects of recent anthropogenic disturbances and establish conservation recommendations for this lake ecosystem, we analyzed diatoms and weak-acid leachable elements from a well-dated sediment core from LSP to reconstruct the changes in aquatic conditions and diatom diversity during the period AD 1960–2013. This revealed shifts in diatom assemblages, diversity, and geochemistry that were strongly linked to the construction of a dam in 1962 and rapid eutrophication after 1990. Diatom diversity was stable and relatively high when submerged macrophytes were present between 1962 and 1990. Thus, the reintroduction of endemic macrophytes could benefit the ecological stability and diversity of this shallow lake. Full article

Acid Mine Drainage (AMD) results from sulfide oxidation, which incorporates hydrogen ions, sulfate, and metals/metalloids into the aquatic environment, allowing fixation, bioaccumulation and biomagnification of pollutants in the aquatic food chain. Acidic leachates from waste rock dams from pyritic and (to a lesser extent) coal mining are the main foci of Acid Mine Drainage (AMD) production. When AMD is incorporated into rivers, notable changes in water hydro-geochemistry and biota are observed. There is a high interest in the biodiversity of this type of extreme environments for several reasons. Studies indicate that extreme acid environments may reflect early Earth conditions, and are thus, suitable for astrobiological experiments as acidophilic microorganisms survive on the sulfates and iron oxides in AMD-contaminated waters/sediments, an analogous environment to Mars; other reasons are related to the biotechnological potential of extremophiles. In addition, AMD is responsible for decreasing the diversity and abundance of different taxa, as well as for selecting the most well-adapted species to these toxic conditions. Acidophilic and acidotolerant eukaryotic microorganisms are mostly composed by algae (diatoms and unicellular and filamentous algae), protozoa, fungi and fungi-like protists, and unsegmented pseudocoelomata animals such as Rotifera and micro-macroinvertebrates. In this work, a literature review summarizing the most recent studies on eukaryotic organisms and micro-organisms in Acid Mine Drainage-affected environments is elaborated. Full article

Dissolved heavy metals (HMs), derived from natural and anthropogenic sources, are an important part of aquatic environment research and gain more international concern due to their acute toxicity. In this study, the geochemistry of dissolved HMs was analyzed in the upper Three Gorges Reservoir (TGR) of the Yangtze River (YZR) watershed to explore their distribution, status, and sources and further evaluate the water quality and HM-related risks. In total, 57 water samples were collected from the main channel and tributaries of the upper TGR. The concentrations of eight HMs, namely V, Ni, Cu, Zn, As, Mo, Cd, and Pb, were measured by ICP-MS. The mean concentrations (in μg/L) of eight HMs decreased in the order: As (1.46), V (1.44), Ni (1.40), Mo (0.94), Cu (0.86), Zn (0.63), Pb (0.03), and Cd (0.01). The concentrations of most HMs were 1.4~8.1 times higher than that in the source area of the YZR, indicating a potential anthropogenic intervention in the upper TGR. Spatially, the concentrations of V, Cu, As, and Pb along the main channel gradually decreased, while the others were relatively stable (except for Cd). The different degrees of variations in HM concentrations were also found in tributaries. According to the correlation analysis and principal component (PC) analysis, three PCs were identified and explained 75.1% of the total variances. combined with the concentrations of each metal, PC1 with high loadings of V, Ni, As, and Mo was considered as the main contribution of human inputs, PC2 (Cu and Pb) was primarily attributed to the contribution of mixed sources of human emissions and natural processes, and Zn and Cd in PC3 were controlled by natural sources. Water quality assessment suggested the good water quality (meeting the requirements for drinking purposes) with WQI values of 14.1 ± 3.4 and 11.6 ± 3.6 in the main channel and tributaries, respectively. Exposure risk assessment denoted that the health effects of selected HMs on the human body were limited (hazard index, HI < 1), but the potential risks of V and As with HI > 0.1 were non-negligible, especially for children. These findings provide scientific support for the environmental management of the upper TGR region and the metal cycle in aquatic systems. Full article

Mediterranean wetlands are severely affected by habitat degradation and related loss of biodiversity. In this scenario, the wide number of artificial farm ponds can play a significant role in the biodiversity conservation of aquatic flora. In the present contribution we show the preliminary results of a study on Mediterranean farm ponds of north-western Sicily (Italy), aimed to investigating the environmental factors linked to the occurrence of submerged macrophytes (vascular plants and charophytes). We studied the aquatic flora of 30 ponds and determined the chemical and isotopic composition of their water bodies on a subset of the most representative 10 sites. Results show that (1) farm ponds host few but interesting species, such as Potamogeton pusillus considered threatened at regional level; (2) Chara vulgaris, C. globularis and P. pusillus behave as disturbance-tolerant species, occurring both in nitrates-poor and nitrates-rich waters, whereas Stuckenia pectinata and Zannichellia palustris occur only in nitrates-poor waters. Although farm ponds are artificial and relatively poor habitats, these environments seem to be important for the aquatic flora and for the conservation of the local biodiversity, and can give useful information for the use of macrophytes as bioindicators in the Mediterranean area. Full article

Steppe and semi-desert lakes of Central Asia represent unique and still poorly known aquatic ecosystems. The paper provides summaries of multi-proxy environmental and biological investigations of the previously unexplored ground of Sibe lakes in the naturally pristine zone of East Kazakhstan, and of their contributions to people. Data on the taxonomic composition of zooplankton and zoobenthos of these freshwater lacustrine basins are presented in terms of the species’ frequency of occurrence; the abundance of the aquatic biomass and the analyzed water geochemical variables insofar as they are dependent and correlative. The qualitative and quantitative records display variability in the biocenosis diversity due to the lakes’ geochemistry and hydrology differences—some lakes being oligotrophic and others being moderately trophic. In the latter case, the lakes characterized by an increased macrozoobenthos biomass are favourable for local ichthyofauna. Sapro-biological analysis reveals the predominance of β-saprobic species in the zooplankton composition pointing to slight or moderate pollution of surface waters due to natural biotic substances. This observation is in agreement with differences in the water quality of solitary lakes. The uneven distributions of benthic invertebrates (in terms of taxonomy and species populations) in the water bodies suggest specific hydro-ecological conditions that predetermine the structure of the lakes’ biocenosis. The littoral part of the lakes is characterized by the highest abundance of zooplankton and benthic fauna. The Sibe lakes are an example of an autonomous functioning of the lacustrine basins in the upland arid steppe zone, which is characterized by pronounced climate “continentality” and a high level of the sub-aquatic flora and fauna endemism. The present results are relevant to the understanding of the ecosystems’ dynamics and the modern anthropogenic impacts upon the pristine parkland-steppe landscapes of Central Asia, with implications for regional nature protection and sustainable eco-recreation. Full article

The Tonghua Basin in Northeast China potentially contains shale oil and gas resources, but the exploration and development of these resources has been limited. The Sankeyushu depression represents the sedimentary center of the Tonghua Basin, and a large thickness of shale, the Hengtongshan Formation, was deposited in this depression. Exploratory engineering discoveries in recent years have confirmed that the Hengtongshan Formation has the potential to produce oil and gas. A series of methods, including inorganic and organic geochemistry and organic petrology, have been used to study the source material, organic matter maturity, depositional environment and oil-generating potential of the Hengtongshan Formation. Investigation of drill core samples has revealed that the Hengtongshan Formation in the Sankeyushu depression is mainly composed of black shale, with a small amount of plant fossils and thin volcanic rocks, and the content of brittle minerals (quartz + carbonate minerals) is high. The provenance of organic matter in the source rocks in the Hengtongshan Formation is a mixture of aquatic organisms (algae and bacteria) and higher plants, and there may be some marine organic components present in some strata.The organic matter was deposited and preserved in a saline reducing environment. Volcanism may have promoted the formation of a reducing environment by stratification of the lake bottom water, and the lake may have experienced a short-term marine ingression with the increase in the salinity. The maturity of the organic matter in all the source rocks in the Hengtongshan Formation is relatively high, and hydrocarbons have been generated. Some source rocks may have been affected by volcanism, and the organic matter in these rocks is overmature. In terms of the shale oil resource potential, the second member of the Hengtongshan Formation is obviously superior to the other members, with an average total organic carbon (TOC) of 1.37% and an average hydrogen index (HI) of 560.93 mg HC/g TOC. Most of the samples can be classified as good to very good source rocks with good resource potential. The second member can be regarded as a potential production stratum. According to the results of geochemical analysis and observations of shale oil and natural gas during drilling, it is predicted that the shale oil is present in the form of a self-sourced reservoir, but the migration range of natural gas is likely relatively large. Full article

This study presents the influence of rainfall and human perturbation on physical and chemical weathering rates, and carbon and nutrient yields in the basin of the Kaoping, a small mountainous river (SMR) in southwestern Taiwan. The study was derived principally from the spatial and temporal variability of aquatic geochemistry in the river during wet (1999–2000) and drought (2002) periods. The total, physical, and chemical weathering rates in the river basin ranged respectively from 4739, 3601, and 1138 g m⁻² year⁻¹ in the wet period to 1072, 656, and 416 g m⁻² year⁻¹ in the drought period, resulting mainly from a large difference in rainfall and river discharge between the two periods. The wet and drought periods were likely associated with La Niña and El Niño events, respectively. The weathering rates of the wet period were much higher than those reported from the world’s river basins, showing the unique characteristics of the SMR. The total carbon yield was derived mainly from dissolved inorganic carbon and was much higher in the wet period (140 g C m⁻² year⁻¹) than in the drought period (53.7 g C m⁻² year⁻¹). Taking silicate weathering (54.7 ± 10.2%) slightly over carbonate weathering (48.6 ± 9.5%) in determining dissolved ion loads, the Kaoping catchment may currently consume 0.155–0.298 MtC/year atmospheric CO₂ without considering the CO₂ released from chemical weathering. The nutrient yields were controlled mainly by human inputs but also enhanced by increased rainfall. Both regional and local climatic conditions and human impacts likely determined the weathering rates and total yields of carbon and nutrients. The SMRs may collectively contribute significantly to global fluxes of terrestrial sediments, geochemical matters, carbon, and nutrients to oceans. Full article

The partitioning of metals and metalloids between their dissolved and suspended forms in river systems largely governs their mobility and bioavailability. However, most of the existing knowledge about catchment-scale metal partitioning in river systems is based on a limited number of observation points, which is not sufficient to characterize the complexity of large river systems. Here we present an extensive field-based dataset, composed of multi-year data from over 100 monitoring locations distributed over the large, transboundary Selenga River basin (of Russia and Mongolia), sampled during different hydrological seasons. The aim is to investigate on the basin scale, the influence of different hydroclimatic conditions on metal partitioning and transport. Our results showed that the investigated metals exhibited a wide range of different behaviors. Some metals were mostly found in the dissolved form (84–96% of Mo, U, B, and Sb on an average), whereas many others predominantly existed in suspension (66–87% of Al, Fe, Mn, Pb, Co, and Bi). Nevertheless, our results also showed a consistently increasing share of metals in dissolved form as the metals were transported to the downstream parts of the basin, closer to the Lake Baikal. Under high discharge conditions (including floods), metal transport by suspended particulate matter was significantly greater (about 2–6 times). However, since high and low water conditions could prevail simultaneously at a given point of time within the large river basin, e.g., as a result of on-going flood propagation, snap-shot observations of metal partitioning demonstrated contrasting patterns with domination of both particulate and dissolved phases in different parts of the basin. Such heterogeneity of metal partitioning is likely to be found in many large river systems. These results point out the importance of looking into different hydroclimatic conditions across space and time, both for management purposes and contaminant modeling efforts at the basin scale. Full article

Lake Baikal is the largest freshwater body on Earth, once famous for its pristine conditions. However, the lake and its drainage basin with their unique ecosystems have in recent decades been subject to both climate warming above the world average and severe anthropogenic pressures from mining and agriculture. Although previous studies have targeted various hydroclimatic, geochemical, and biological conditions of the Lake Baikal basin, the heterogeneous nature and large size of the basin leave considerable knowledge gaps regarding ongoing metal contamination of the basin’s suspended sediments and waters. To address these knowledge gaps, the main objectives of this study are to (i) determine regional background values for water and suspended sediment quality with respect to multiple metals (representing undisturbed conditions) and (ii) further evaluate spatio-temporal concentration patterns of these metals, including regions with heavy anthropogenic impacts. We synthesize data from extensive field measurements within the Selenga River basin performed between 2011 and 2016, covering over 100 sampling locations. Results show that although the background metal concentrations (of both dissolved and suspended metal forms) in the alkaline Selenga River waters were close to the world averages, metal concentrations of up to two orders of magnitude above the background values were seen for Zn, As, Cd, Cu, Mo, and Pb in regions subject to anthropogenic impacts (cities and the mining industry). Specifically, dissolved As levels within the Selenga River basin were 2–5 times higher than the world average and well above the global guideline value in several regions. Notable hotspots for anthropogenic impacts of Cd were particularly found in Zakamensk and Ulaanbaatar. Our results highlight clear anthropogenic impacts and large-scale spreading of several pollutants of concern, with risks even to downstream parts including the Selenga delta and Lake Baikal. We expect that these results will aid in increasing the understanding of large-scale metal transport processes, as well as for designing relevant measures to mitigate further spreading of metals to Lake Baikal. Full article

This study was promoted by the recent efforts using larger benthic foraminiferal (LBF) shells geochemistry for the monitoring of heavy metals (HMs) pollution in the marine environment. The shell itself acts as a recorder of the ambient water chemistry in low to extreme HMs-polluted environments, allowing the monitoring of recent-past pollution events. This concept, known as sclerochronology, requires the addition of new parts (i.e., new shell) even in extreme pollution events. We evaluated the physiological resilience of three LBF species with different shell types and symbionts to enriched concentrations of Cd, Cu, and Pb at levels several folds higher than the ecological criteria maximum concentration (CMC) (165–166, 33–43, 1001–1206 µg L⁻¹, respectively), which is derived from aquatic organisms’ toxicity tests. The physiological response of the holobiont was expressed by growth rates quantified by the addition of new chambers (new shell parts), and by the chlorophyll a of the algal symbionts. The growth rate decrease varied between 0% and 30% compared to the unamended control for all HMs tested, whereas the algal symbionts exhibited a general non-fatal but significant response to Pb and Cu. Our results highlight that shell growth inhibition of LBF is predicted in extreme concentrations of 57 × CMC of Cu and 523 × CMC of Cd, providing a proof of concept for shell geochemistry monitoring, which is currently not used in the regulatory sectors. Full article

The Colorado River basin (CRB), the primary water source for southwestern North America, is divided into the 283,384 km², water-exporting Upper CRB (UCRB) in the Colorado Plateau geologic province, and the 344,440 km², water-receiving Lower CRB (LCRB) in the Basin and Range geologic province. Long-regarded as a snowmelt-fed river system, approximately half of the river’s baseflow is derived from groundwater, much of it through springs. CRB springs are important for biota, culture, and the economy, but are highly threatened by a wide array of anthropogenic factors. We used existing literature, available databases, and field data to synthesize information on the distribution, ecohydrology, biodiversity, status, and potential socio-economic impacts of 20,872 reported CRB springs in relation to permanent stream distribution, human population growth, and climate change. CRB springs are patchily distributed, with highest density in montane and cliff-dominated landscapes. Mapping data quality is highly variable and many springs remain undocumented. Most CRB springs-influenced habitats are small, with a highly variable mean area of 2200 m², generating an estimated total springs habitat area of 45.4 km² (0.007% of the total CRB land area). Median discharge also is generally low and variable (0.10 L/s, N = 1687, 95% CI = 0.04 L/s), but ranges up to 1800 L/s. Water pH and conductivity is negatively related to elevation, with a stronger negative relationship in the UCRB compared to the LCRB. Natural springs water temperature and geochemistry throughout the CRB varies greatly among springs, but relatively little within springs, and depends on aquifer hydrogeology, elevation, and residence time. As the only state nearly entirely included within the CRB, Arizona is about equally divided between the two geologic provinces. Arizona springs produce approximately 0.6 km³/year of water. Data on >330 CRB springs-dependent taxa (SDT) revealed at least 62 plant species; 216 aquatic and riparian Mollusca, Hemiptera, Coleoptera, and other invertebrate taxa; several herpetofanual species; and two-thirds of 35 CRB fish taxa. Springs vegetation structure, composition, and diversity vary strongly by springs type, and plant species density within springs is high in comparison with upland habitats. Plant species richness and density is negatively related to elevation below 2500 m. Human population in and adjacent to the CRB are growing rapidly, and ecological impairment of springs exceeds 70% in many landscapes, particularly in urbanized and rangeland areas. Anthropogenic stressors are primarily related to groundwater depletion and pollution, livestock management, flow abstraction, non-native species introduction, and recreation. Ensuring the ecological integrity and sustainability of CRB groundwater supplies and springs will require more thorough basic inventory, assessment, research, information management, and local ecosystem rehabilitation, as well as improved groundwater and springs conservation policy. Full article