Search Results (175)

Many effluents from human activities discharged into freshwater ecosystems cause chemical pollution. Chemical pollution in rivers is a serious threat to freshwater ecosystems due to the associated potential human health risks. This study determined the extent of chemical pollution, identified potential sources of pollution and assessed human health risk in the Moopetsi River, an intermittent river in the Limpopo Province of South Africa. Chemical analyses were conducted on water and sediment samples collected during high-flow, low-flow and intermittent-flow regimes. The findings showed seasonal variations in the chemical pollution levels in the sediments and the highest contamination was measured during intermittent flow. The enrichment factor and geoaccumulation index values identified chromium and nickel as major contributors to sediment contamination. The mean arsenic, chromium and nickel levels exceeded the established guideline values. An evaluation of human health risk was conducted using ingestion and dermal absorption pathways. The results showed that ingestion has greater non-carcinogenic and carcinogenic risks than dermal exposure, especially for children during intermittent flow. The elements of great concern for non-carcinogenic risk were chromium, manganese and nickel and for carcinogenic risk, they were arsenic, chromium, nickel and lead. The outcome of this study is useful for waste management and conservation to reduce environmental degradation and human health risk. Full article

Heavy metal contamination in paddy fields poses serious risks to food safety and crop productivity. This study evaluated the potential of native soil fungi as bioinoculants to reduce metal uptake in rice cultivated under contaminated conditions. Eight fungal strains—four indigenous and four allochthonous—were selected based on their plant growth-promoting traits, including siderophore production and phosphate solubilization. Additional metabolic analysis confirmed the production of bioactive secondary metabolites. In a greenhouse experiment, three rice cultivars were grown under permanent flooding (PF) and alternate wetting and drying (AWD) in soil enriched with arsenic, cadmium, chromium, and copper. Inoculation with indigenous fungi under AWD significantly reduced the arsenic accumulation in rice shoots by up to 75%. While AWD increased cadmium uptake across all cultivars, fungal inoculation led to a moderate reduction in cadmium accumulation—ranging from 15% to 25%—in some varieties. These effects were not observed under PF conditions. The results demonstrate the potential of native fungi as a nature-based solution to mitigate heavy metal stress in rice cultivation, supporting both environmental remediation and sustainable agriculture. Full article

The plateaus of north-central Mexico have an arid to semiarid climate and groundwater naturally contaminated with inorganic arsenic (iAs) and fluoride (F). Like other arid and semiarid areas, this region faces great challenges to maintain a safe supply of drinking and irrigation water. Studies conducted in the past few decades on various locations within this region have reported groundwater iAs, F, and nitrate-nitrogen (NO₃-N), and either their source, enrichment processes, health risks, and/or potential water treatments. The relevant findings are analyzed and condensed here to provide an overview of the groundwater situation of the region. Studies identify volcanic rocks (rhyolite) and their weathering products (clays) as the main sources of iAs and F and report that these solutes become enriched through evaporation and residence time. In contrast, NO₃-N is reported as anthropogenic, with the highest concentrations found in large urban centers and in agricultural and livestock farm areas. Health risks are high since the hot spots of contamination correspond to populated areas. Health problems associated with NO₃-N in drinking water may be underestimated. Removal technologies of the contaminants remain at the laboratory or pilot stage, except for the reverse osmosis filtration units fitted to selected wells within the state of Chihuahua. A recent approach to supplying drinking water free of iAs and F to two urban centers consisted of switching from groundwater to surface water. Incipient research currently focuses on the potential repercussions of irrigating crops with As-rich water. The groundwater predicaments concerning contamination, public health impact, and irrigation suitability depicted here can be applied to semiarid areas worldwide. Full article

Arsenic (As) contamination in groundwater represents a major global public health threat, particularly in alluvial aquifer systems where redox-sensitive geochemical processes facilitate the mobilization of naturally occurring trace elements. This study investigates groundwater quality, particularly focusing on the origin of arsenic contamination in shallow and deep alluvial aquifers of the Lower Sakarya River Basin, which are crucial for drinking, domestic, and agricultural uses. Groundwater samples were collected from 34 wells—7 tapping the shallow aquifer (<60 m) and 27 tapping the deep aquifer (>60 m)—during wet and dry seasons for the hydrogeochemical characterization of groundwater. Environmental isotope analysis (δ¹⁸O, δ²H, ³H) was conducted to characterize origin and groundwater residence times, and the possible hydraulic connection between shallow and deep alluvial aquifers. Mineralogical and geochemical characterization of the sediment core samples were carried out using X-ray diffraction and acid digestion analyses to identify mineralogical sources of As and other metals. Pearson correlation coefficient analyses were also applied to the results of the chemical analyses to determine the origin of metal enrichments observed in the groundwater, as well as related geochemical processes. The results reveal that 33–41% of deep groundwater samples contain arsenic concentrations exceeding the WHO and Turkish drinking water standard of 10 µg/L, with maximum values reaching 373 µg/L. Manganese concentrations exceeded the 50 µg/L limit in up to 44% of deep aquifer samples, reaching 1230 µg/L. On the other hand, iron concentrations were consistently low, remaining below the detection limit in nearly all samples. The co-occurrence of As and Mn above their maximum contaminant levels was observed in 30–33% of the wells, exhibiting extremely low sulfate concentrations (0.2–2 mg/L), notably low dissolved oxygen concentration (1.45–3.3 mg/L) alongside high bicarbonate concentrations (450–1429 mg/L), indicating localized varying reducing conditions in the deep alluvial aquifer. The correlations between molybdenum and As (rdry = 0.46, rwet = 0.64) also indicate reducing conditions, where Mo typically mobilizes with As. Arsenic concentrations also showed significant correlations with bicarbonate (HCO₃⁻) (rdry = 0.66, rwet = 0.80), indicating that alkaline or reducing conditions are promoting arsenic mobilization from aquifer materials. All these correlations between elements indicate that coexistence of As with Mn above their MCLs in deep alluvial aquifer groundwater result from reductive dissolution of Mn/Fe(?) oxides, which are primary arsenic hosts, thereby releasing arsenic into groundwater under reducing conditions. In contrast, the shallow aquifer system—although affected by elevated nitrate, sulfate, and chloride levels from agricultural and domestic sources—exhibited consistently low arsenic concentrations below the maximum contaminant level. Seasonal redox fluctuations in the shallow zone influence manganese concentrations, but the aquifer’s more dynamic recharge regime and oxic conditions suppress widespread As mobilization. Mineralogical analysis identified that serpentinite, schist, and other ophiolitic/metamorphic detritus transported by river processes into basin sediments were identified as the main natural sources of arsenic and manganese in groundwater of deep alluvium aquifer. Full article

Active and abandoned mining sites are significant sources of heavy metals and metalloid pollution, leading to serious environmental issues. This study assessed the environmental risks posed by potentially toxic elements (PTEs), specifically arsenic (As) and antimony (Sb), in the Technosols (mining residues) of the former Pejão coal mine complex in Northern Portugal, a site impacted by forest wildfires in October 2017 that triggered underground combustion within the waste heaps. Our methodology involved determining the “pseudo-total” concentrations of As and Sb in the collected heap samples using microwave digestion with aqua regia (ISO 12914), followed by analysis using hydride generation-atomic absorption spectroscopy (HG-AAS). The concentrations of As an Sb ranging from 31.0 to 68.6 mg kg⁻¹ and 4.8 to 8.3 mg kg⁻¹, respectively, were found to be above the European background values reported in project FOREGS (11.6 mg kg⁻¹ for As and 1.04 mg kg⁻¹ for Sb) and Portuguese Environment Agency (APA) reference values for agricultural soils (11 mg kg⁻¹ for As and 7.5 mg kg⁻¹ for Sb), indicating significant enrichment of these PTEs. Based on average I_geo values, As contamination overall was classified as “unpolluted to moderately polluted” while Sb contamination was classified as “moderately polluted” in the waste pile samples and “unpolluted to moderately polluted” in the downhill soil samples. However, total PTE content alone is insufficient for a comprehensive environmental risk assessment. Therefore, further studies on As and Sb fractionation and speciation were conducted using the Shiowatana sequential extraction procedure (SEP). The results showed that As and Sb levels in the more mobile fractions were not significant. This suggests that the enrichment in the burned (BCW) and unburned (UCW) coal waste areas of the mine is likely due to the stockpiling of lithic fragments, primarily coals hosting arsenian pyrites and stibnite which largely traps these elements within its crystalline structure. The observed enrichment in downhill soils (DS) is attributed to mechanical weathering, rock fragment erosion, and transport processes. Given the strong association of these elements with solid phases, the risk of leaching into surface waters and aquifers is considered low. This work underscores the importance of a holistic approach to environmental risk assessment at former mining sites, contributing to the development of sustainable remediation strategies for long-term environmental protection. Full article

Accumulating epidemiological evidence has indicated that arsenic exposure can lead to kidney injury. However, the underlying mechanisms of arsenic-induced nephrotoxicity have not been fully elucidated. In this study, the effect of sodium arsenite on the cell viability of HEK-293 cells was studied using a CCK-8 assay. Metabolomic and transcriptomic analyses were applied to identify differential metabolites (DMs) and differentially expressed genes (DEGs) in human renal cells exposed to arsenite, respectively. The results showed that the IC₅₀ of arsenite on HEK-293 cells was 25 μM. A total of 621 DMs were identified in arsenic-treated cells (VIP > 1, p < 0.05). The results of the metabolome analysis revealed that purine metabolism was the major affected pathway, with 21 DMs enriched within this pathway. Additionally, 9831 DEGs were obtained after arsenic exposure (|log₂FC| > 1, Padj < 0.05). The results of the transcriptome analysis showed that ECM–receptor interaction and cell adhesion molecules were the major altered KEGG pathways, with 54 and 70 enriched DEGs, respectively. Integrated metabolomics and transcriptomics analyses revealed that the predominant mechanisms underlying arsenic-induced nephrotoxicity were associated with the perturbations of lipid metabolism and purine metabolism. Overall, the present study provided comprehensive insights into the metabolic and transcriptional alterations in human renal cells in response to arsenic exposure, providing a referable scientific basis for subsequent arsenic-induced nephrotoxicity studies. Full article

Arsenic contamination in aquifers poses a significant global health risk due to its toxicity and widespread presence in groundwater used for drinking. Although several approaches for arsenic removal exist, many are either expensive or logistically difficult. This study assesses the efficacy of native limestones from two arsenic-contaminated regions in Mexico as a sustainable treatment alternative. Tested in batch and column experiments using synthetic solutions, as well as natural and arsenic-enriched groundwater, the limestones were characterized mineralogically (XRD) and chemically (XRF). Surface area, particle size, average pore volume in rocks, and competing anions (i.e., bicarbonate and sulfate) in groundwaters played important roles in removal performance. The results show that smaller particle sizes improve arsenic retention. Up to 87.6% of the arsenic was removed from groundwater containing 1.29 mg/L of arsenic when treated with rock particles smaller than 0.062 mm. Natural groundwater, however, in general, exhibited lower efficiency than synthetic solutions due to anion interference. Although site-specific evaluations are essential, these results indicate that limestone may be a cost-effective and locally accessible solution for addressing arsenic (As) contamination in regions with abundant limestone outcrops. Full article

The contamination of paddy soils with arsenic (As) and cadmium (Cd), coupled with the depletion of soil organic carbon (SOC), poses significant threats to rice yields and quality. There is an urgent need to identify a suitable soil additive capable of achieving simultaneous heavy metal remediation and promotion of organic matter enrichment. The current study introduced two novel iron (Fe)/magnesium (Mg)-based bimetal-oxide-modified rice straw biochar (RSB), namely RSB-Fe/Mn and RSB-Fe/Mg. It evaluated their effectiveness in As/Cd immobilization and SOC preservation. An 8-week cultivation experiment was carried out in sequential drying–flooding moisture fluctuation conditions, with the soil pore water As/Cd (PWAs/Cd) and SOC fractions monitored. The mechanisms of As/Cd immobilization were investigated using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS) characterizations. Results revealed that PWAs and PWCd were reduced by up to 67.1% and 80.2% during the drying period and by 27.0% and 76.5% during the flooding period, respectively. Additionally, SOC content increased by 16.3% and 33.9% with RSB-Fe/Mn addition during the drying and flooding period, respectively, with an increase in the mineral-associated organic carbon (MAOC) fraction. The study proves that RSB-Fe/Mn and RSB-Fe/Mg are effective for soil As/Cd passivation and SOC stabilization, offering a promising solution to mitigate As and Cd pollution in paddy soils while maintaining soil quality. Full article

As arsenopyrite is a typical arsenic-bearing sulfide ore, the biooxidation process of arsenopyrite is of great significance for the extraction of gold from arsenic-bearing gold ores and the generation of arsenic-bearing acid mine drainage. During the biooxidation of arsenopyrite, a large amount of arsenic is produced, which inhibits the growth and metabolism of microorganisms and thus affects the extraction of gold from arsenic-bearing gold ores. Therefore, the screening and enrichment of microorganisms with high arsenic resistance have become important aspects in the study of arsenopyrite biooxidation. As described in this paper, through arsenic acclimation, the maximum arsenic tolerance concentration of Acidithiobacillus ferriphilus QBS 3 isolated from arsenic-containing acid mine drainage was increased to 80 mM As(Ⅲ) and 100 mM As(V). Microorganisms with high arsenic resistance showed better bioleaching performance for arsenopyrite. After 18 days of bioleaching, the leaching rate of arsenopyrite reached 100% at a pulp concentration of 0.5%, and after 30 days of bioleaching, the leaching rate of arsenopyrite was 79.96% at a pulp concentration of 1%. Currently, research on arsenopyrite mainly focuses on the control and optimization of environmental conditions, but there have been few studies on the biooxidation process of arsenopyrite at the protein and gene levels. Therefore, combining the results of a one-month bioleaching experiment on arsenopyrite by A. ferriphilus QBS 3 and the analysis of arsenic resistance genes, a bioleaching model of arsenopyrite was constructed, which laid an experimental basis and theoretical foundation for improving the gold recovery rate from refractory arsenic-bearing ores and exploring the arsenic resistance mechanism of microorganisms during the arsenopyrite leaching process. Full article

Heavy metals (HMs), characterized by their non-biodegradable nature, are prone to enrichment in river sediments, thereby severely jeopardizing the equilibrium of ecosystems and human health. Given the critical importance of safeguarding valuable water resources, it is of utmost urgency to initiate research on HMs within the Yellow River Basin (YRB). This study collected river sediment samples from the Yellow River Basin and analyzed the distribution characteristics, health risks, and pollution sources of HMs utilizing the pollution index method, health risk assessment, and positive matrix factorization (PMF) model. The results demonstrate that arsenic (As), zinc (Zn), and cadmium (Cd) are the primary elements contributing to heavy metal (HM) pollution in the sediments of the YRB. The proportions of sediment samples with low HM pollution in the upstream, midstream, and downstream are 36.48%, 71.43%, and 72.73%, respectively, whereas the proportions of samples with moderate pollution are 63.16%, 28.57%, and 27.27%, respectively. The health risk assessment reveals that the non-carcinogenic risks posed by HM pollution in the sediments to adults are negligible, whereas those to children are not. Regarding carcinogenic risks, the carcinogenic risk index of As is significantly higher than that of the other HMs. The primary sources of HM pollution in the sediments are identified as traffic–industrial sources, agricultural–industrial sources, and industrial sources, with respective contribution rates of 32.47%, 44.87%, and 22.66%. As and Zn are prioritized as elements for health risk control, while agricultural–industrial sources are highlighted as the priority sources for pollution control. Full article

Microplastics and heavy metals (HMs) in soil pose significant environmental and health risks, yet the interactions between mulch film residues and HMs, and their effects on maize productivity, remain poorly understood. This study examined the impacts of long-term traditional polyethylene mulch film (TMF) and biodegradable mulch film (BMF) residues on soil properties, maize root accumulation of HMs, the arbuscular mycorrhizal fungi (AMF) community, and maize productivity under open field conditions. TMF residues significantly increased the soil total carbon (TC), C/N ratio, and bioaccumulation coefficients (BACs) of arsenic (As) and cadmium (Cd) while lowering soil pH and water content. These changes altered AMF colonization and enriched the Paraglomus genus, leading to enhanced maize leaf antioxidant activity and reduced chlorophyll content, although maize growth was not statistically affected. In contrast, they improved soil nutrient availability (e.g., nitrogen and phosphorus), increased TC and the C/N ratio, and reduced soil pH. Notably, BMF residues decreased the BACs of As and Cd, reduced AMF spore density without altering community structure, and ultimately enhanced maize biomass. These effects were associated with BMF’s ability to lower pH and chelate HMs, thereby mitigating their bioavailability and promoting plant growth. Furthermore, the enriched abundance of AMF species, particularly from the Claroideoglomus genus, facilitated heavy metal chelation and reduced HM accumulation in plants. The findings underscore the potential of BMF and AMF for co-remediation of microplastics and HMs, highlighting the importance of mulching strategies for sustainable agriculture. Full article

Monitoring river systems is crucial for understanding and managing water resources, predicting natural disasters, and maintaining ecological balance. Assessment of heavy metal pollution derived valuable data which are critical for the environmental management and regulatory compliance of the Jukskei River. Heavy elements were evaluated in the Jukskei River for seasonal impact, potential health risks, and contamination level with concentration levels ranging from 6900 mg/kg iron (Fe) to 0.85 mg/kg cadmium (Cd) in the dry sampling season and 6900 mg/kg Fe to 0.26 mg/kg Cd in the wet season. Enrichment factor analysis indicated high contamination levels of Fe and Pb in both dry and wet seasons. Moreover, pollution indicators revealed extremely high contamination of geo-accumulation and enrichment factors in the downstream to upstream in both seasons with a mild contamination factor for mercury (Hg). Principal Component Analysis revealed anthropogenic sources of arsenic (As), Cd, and Pb due to wastewater and agricultural pesticide application while Thorium (Th), uranium (U) and Hg were attributed as a results of gold mining activities. ANOVA and Pearson correlation analysis showed a high and moderate link between As–Pb, Cd–Pd, and As–Hg, which are significantly correlated. The potential ecological risk index assessment revealed a significant impact of heavy metals on the freshwater ecosystem. Full article

Water environments contaminated with arsenic (As) have become a significant environmental concern. Previous research has highlighted the detrimental effects of As on fish, but limited knowledge exists regarding its impacts on endocrine systems. To address this gap, zebrafish embryos were exposed to various concentrations (0, 25, 50, 75, and 150 μg/L) of arsenate (AsV) for 120 h post-fertilization (hpf). Our findings indicate that exposure to AsV significantly increases cortisol- and thyroid-stimulating hormone (TSH) levels while decreasing estradiol (E2) and testosterone (T) levels. Additionally, it initially decreases and then increases thyroxine (T4) contents. Furthermore, several key genes relevant to these endocrine systems also show significant influences. The results from principal component analysis demonstrate that TRH, TSH, TRHRb, and TRβ primarily affect the level of T4 while Cyp11b, StAR, hmgrb MC2R, and GR mainly influence cortisol levels. On the other hand, Cyp19a, Cyp17, 17βhsd, ERβ, LHR, hmgrb, and AR predominantly impact E2 and T levels. Transcriptomics and enrichment analysis reveal that these pathways are primarily associated with steroid hormone synthesis and transport. Furthermore, it was found that AsV stimulates the cAMP signaling pathway through a compensation mechanism. These results suggest that AsV may potentially act as environmental endocrine-disrupting chemicals with non-negligible interference effects on the endocrine system in zebrafish. This study holds theoretical value in assessing the environmental risk posed by As overall as well as providing an important basis for addressing human health issues and implementing preventive measures. Full article

Arabica coffee, one of the most valuable crop commodities, harbors diverse microbial communities with unique genetic and functional traits that influence bean safety and final coffee quality. In Ecuador, coffee production faces challenges due to the spread of pathogenic organisms across cultivars, leading to reduced yields and compromised quality. This study employed a shotgun metagenomic approach to characterize the indigenous microbial diversity present in the cell biomass of fermented coffee cherries from three Coffea arabica varieties: Typica (Group A), Yellow Caturra (Group B), and Red Caturra (Group C), originating from the Intag Valley in northern Ecuador, at two ripe stages: green (immature fruits) and ripe (red/yellow mature fruits). Gene prediction and functional annotation were performed using multiple databases, including EggNOG, COG, KEGG, CAZy, CARD, and BacMet, to explore the potential impact of microbial communities on bean quality and safety. Metagenomic sequencing generated over 416 million high-quality reads, averaging 66 million clean reads per sample and yielding a total of 47 Gbps of data. Analysis revealed distinct differences in species abundance based on the coffee variety and ripening stage. A total of 799,658 protein-coding sequences (CDSs) were predicted, of which 205,937 genes were annotated with EggNOG, 181,723 with COG, 155,220 with KEGG, and 10,473 with CAZy. Additionally, 432 antibiotic resistance genes (ARGs) were identified using CARD, and 8974 biocide and metal resistance genes (BMRGs) were annotated with BacMet. Immature cherries exhibited enriched pathways associated with resistance to antibiotics such as fluoroquinolones, penams, rifamycin, macrolides, carbapenems, and cephalosporins. The abundance of these pathways varied with the ripening stage and variety. Furthermore, green cherries showed a significant increase in BMRGs associated with resistance to substances including hydrochloric acid, copper, nickel, hydrogen peroxide, arsenic, and zinc. Among mature cherries, Typica and Red Caturra shared similar profiles, while Yellow Caturra displayed a divergent microbial and functional profile. These study findings emphasize the interplay between microbial diversity, ripening stages, and coffee varieties, providing a foundation for innovative approaches to enhance coffee quality through microbiome management. Full article

The Nevşehir coals are located in the Central Anatolian Crystalline Complex (CACC), Türkiye, and no reports exist on trace element, nitrogen, and carbon isotope composition data of the Nevşehir coals. The present study aims to geochemically characterise the Nevşehir coals to determine their trace elemental enrichment patterns and possible sources. Nevşehir coals are found within Late Miocene Kızılöz Formation (Arafa Member) rocks. These coals are part of the huminite maceral group; the dominant maceral group is ulminites. The minerals in coals are inorganic, such as oxidised framboidal pyrite, iron oxide minerals, quartz, clay, and carbonate minerals. Coals have great potential regarding trace elements. Benefits might arise from mining and using some of the critical elements derived from coal. Compared with the world coal average, the coal samples in this study are enriched in As (149.25 μg/g), V (245 μg/g), Cr (159 μg/g), Ga (18 μg/g), Ni (216 μg/g), Th (17 μg/g), Zn (143 μg/g), and U (54 μg/g). The arsenic content in this study is associated with inorganic components such as oxidised framboidal pyrite. Vanadium in coal is mainly associated with aluminosilicates and organic matter. Chromium originates from the clay minerals within coals. Uranium in coal is mainly associated with organic matter. Nickel and zinc in coal are predominantly associated with sulphides. The δ¹⁵N contents of the samples are comparable to those of several references, including plants, terrestrial creatures, and organic nitrogen. The δ¹³C–δ¹⁵N isotopic range and average values for four coal samples ranged from −25.66‰ to −25.91‰ (−25.80‰) and 3.6‰ to 4.3‰ (3.9‰), respectively, demonstrating that C3 type modern terrestrial vegetation was common in the palaeomires of the studied coal seams. Full article