Arsenic Contamination Research Articles

Arsenic Reduces Methane Emissions from Paddy Soils: Insights from Continental Investigation and Laboratory Incubations.

Arsenic (As) contamination and methane (CH4) emissions co-occur in rice paddies. However, how As impacts CH4 production, oxidation, and emission dynamics is unknown. Here, we investigated the abundances and activities of CH4-cycling microbes from 132 paddy soils with different As concentrations across continental China using metagenomics and the reverse transcription polymerase chain reaction. Our results revealed that As was a crucial factor affecting the abundance and distribution patterns of the mcrA gene, which is responsible for CH4 production and anaerobic CH4 oxidation. Laboratory incubation experiments showed that adding 30 mg kg-1 arsenate increased 13CO2 production by 10-fold, ultimately decreasing CH4 emissions by 68.5%. The inhibition of CH4 emissions by As was induced through three aspects: (1) the toxicity of As decreased the abundance and activity of the methanogens; (2) the adaptability and response of methanotrophs to As is beneficial for CH4 oxidation under As stress; and (3) the more robust arsenate reduction would anaerobically consume more CH4 in paddies. Additionally, significant positive correlations were observed between arsC and pmoA gene abundance in both the observational study and incubation experiment. These findings enhance our understanding of the mechanisms underlying the interactions between As and CH4 cycling in soils.

Fabrication of Fe-Ti heteroatom-based metal-organic framework with vantage defects for high-efficient arsenic removal from water

Arsenic (As) contamination in water remains a formidable concern due to its high toxicity and detrimental impacts on human health and the environment. Selective adsorption utilizing solid adsorbents has emerged as a promising method for the removal of arsenate (As(V)) from drinking water. However, current adsorbents encounter limitations in effectively reducing relatively low-concentration As(V) from water. Here, we designed a Fe-Ti heteroatom-based metal–organic framework (MOF) MIL-125(Ti,Fe) with vantage defects for efficient As(V) removal. In the batch adsorption experiments, MIL-125(Ti,Fe) exhibited an exceptional removal efficiency of 99.3 % from the 10 ppm As(V)-containing water, which clearly overperformed counterpart MOF adsorbents of MIL-125(Ti) and MIL-101(Fe). Kinetic analysis indicated that the adsorption behavior of all three adsorbents followed pseudo-second-order kinetics. Importantly, dynamic breakthrough experiments demonstrated that MIL-125(Ti,Fe) could effectively reduce the As(V) concentration from 1 ppm to 3 ppb, well below the safety limit of 10 ppb set by WHO. Mechanistic analysis revealed that the arsenic adsorption mechanism of MIL-125(Ti,Fe) involved chemical adsorption between As(V) and the incorporated Fe as well as formed oxygen vacancies in MIL-125(Ti,Fe), which acted as essential adsorption sites and interacted with As(V) through the formation of Fe-O-As groups. The novel MIL-125(Ti,Fe) adsorbent demonstrated its great potential for arsenic removal, particularly in treating relatively low-concentration As-contaminated water.

Mitigation of heavy metal toxicity in pigeon pea by plant growth promoting Pseudomonas alcaliphila strain PAS1 isolated from contaminated environment.

The risk of arsenic contamination is rising globally, and it has negative impacts on the physiological processes and growth of plants. Metal removal from contaminated soils can be accomplished affordably and effectively with plant growth promoting rhizobacteria (PGPR)-based microbial management. From this angle, this research evaluated the mitigation of arsenic toxicity using the bacteria isolated from contaminated site, Mettur, Salem district, South India. The newly isolated bacterial strain was screened for plant growth promotion potential and arsenic tolerance such as (100ppm, 250ppm, 500ppm, 800ppm and 1200ppm). The metal tolerant rhizobacteria was identified using 16S rRNA gene sequence analysis as Pseudomonas alcaliphila strain PAS1 (GenBank accession number: OQ804624). Pigeon pea (Cajanus cajan) plants were used in pot culture experiments with varying concentrations of arsenic, (5ppm, 10ppm and 25ppm) both with and without bacterial culture, for a period of 45days. At the concentration of 25ppm after the application of PAS1 enhanced the plant growth, protein and carbohydrate by 35.69%, 18.31% respectively. Interestingly, P. alcaliphila strain PAS1 significantly reduced the stress-induced elevated levels of proline, flavonoid, phenol and antioxidant enzyme in pigeon pea plants was 40%, 31.11%, 27.80% and 20.12%, respectively. Consequently, PAS1 may significantly reduce the adverse effects that arsenic causes to plant development in acidic soils, improve plant uptake of nutrients, and increase plant production. The findings of this study reveal that P. alcaliphila PAS1 is intrinsic for phytoremediation by reducing arsenic accumulation in the root and shoot.

Characteristics and Mechanism of Hematite Dissolution and Release on Arsenic Migration in Heterogeneous Materials

The migration of arsenic in groundwater is influenced by the heterogeneity of the medium, and the presence of iron minerals adds complexity and uncertainty to this effect. In this study, a stratified heterogeneous sand column with an embedded hematite lens at the coarse-to-medium sand interface was designed. We introduced an arsenic-laden solution and controlled groundwater flow to investigate the spatiotemporal characteristics of arsenic migration and the impact of hematite dissolution. The results showed that the medium structure significantly influenced the arsenic migration and distribution within the lens-containing sand column. The clay layers directed the lateral migration of arsenic, and the arsenic concentrations in deeper layers were up to seven times greater than those on the surface. The extraction experiments of solid-phase arsenic revealed that the main adsorption modes on quartz sand surfaces were the specific adsorption (F2) and adsorption on weakly crystalline iron–aluminum oxides (F3), correlating to the specific and colloidal adsorption modes, respectively. Monitoring the total iron ions (Fe(aq)) revealed rapid increases within the first 14 days, reaching a maximum on day 15, and then gradually declining; these results indicate that hematite did not continuously dissolve. This study can aid in the prevention and control of arsenic contamination in groundwater.

High arsenic contamination in the breast milk of mothers inhabiting the Gangetic plains of Bihar: a major health risk to infants

Groundwater arsenic poisoning has posed serious health hazards in the exposed population. The objective of the study is to evaluate the arsenic ingestion from breastmilk among pediatric population in Bihar. In the present study, the total women selected were n = 513. Out of which n = 378 women after consent provided their breastmilk for the study, n = 58 subjects were non-lactating but had some type of disease in them and n = 77 subjects denied for the breastmilk sample. Hence, they were selected for the women health study. In addition, urine samples from n = 184 infants’ urine were collected for human arsenic exposure study. The study reveals that the arsenic content in the exposed women (in 55%) was significantly high in the breast milk against the WHO permissible limit 0.64 µg/L followed by their urine and blood samples as biological marker. Moreover, the child’s urine also had arsenic content greater than the permissible limit (< 50 µg/L) in 67% of the studied children from the arsenic exposed regions. Concerningly, the rate at which arsenic is eliminated from an infant’s body via urine in real time was only 50%. This arsenic exposure to young infants has caused potential risks and future health implications. Moreover, the arsenic content was also very high in the analyzed staple food samples such as rice, wheat and potato which is the major cause for arsenic contamination in breastmilk. The study advocates for prompt action to address the issue and implement stringent legislative measures in order to mitigate and eradicate this pressing problem that has implications for future generations.

Environmental contamination of arsenic: pathway analysis through water-soil-feed-livestock in Nadia District (India) and potential human health risk.

This study investigated arsenic (As) concentrations in diverse environmental components and their potential impact on the health risks faced by residents of the arsenic (As)-contaminated Nadia district in West Bengal, India. A random selection of 182 cattle and 255 goats from 40 livestock farmers in the district revealed that both animals and humans were naturally exposed to elevated arsenic levels through contaminated drinking water, foods, grasses, concentrate feeds, various fodder tree leaves, and other food/feed resources. The mean As concentration in roughages (483.18µg/kg DM) was significantly higher (p < 0.001) than in tree leaves (391.53µg/kg DM), and concentrate feed/ingredients (186.66µg/kg DM). Pond water exhibited higher arsenic levels (106.11µg/L) compared to shallow tube well water (47.96µg/L) and deep tube well water/tap water (10.64µg/L and 10.04µg/L, respectively). The mean arsenic concentration in soils DM of fodder fields, crop fields, and grassland was 10.25, 10.58, and 10.20mg/kg, respectively. It was observed that protein-rich feeds had lower levels of arsenic accumulation (p < 0.048), while fiber-rich feeds containing more cellulose, hemicellulose, and lignin had higher arsenic levels (p < 0.017). Goats consumed 73.46% more arsenic per kg body weight compared to dairy cows. Although chronic and sub-chronic arsenic exposure in the district did not typically manifest symptoms or visible signs in ruminant animals, concentrations in the hair and feces of both cattle and goats exceeded normal values. Cattle feces had significantly higher arsenic (410.43µg/kg DM) levels (p < 0.001) than goat feces (227.00µg/kg DM), and arsenic concentration in cattle hair (1917.74µg/kg DM) was also significantly greater (p < 0.001) than goat hair (1435.74µg/kg DM). Arsenic levels in milk samples from both species were below 10µg/kg. Liver (356.02µg/kg DM) and kidney (317.22µg/kg DM) contained significantly higher (p < 0.001) levels of arsenic compared to muscle (204.23µg/kg DM), and bone (161.98µg/kg DM) in local meat-type adult male goats. The skin accumulated the highest amount of arsenic (576.24µg/kg DM) among the non-edible parts of the goat carcass. The cumulative cancer risk value for adults was 4.96 × 10-3, exceeding the threshold value (1 × 10-6). This suggests a significant risk of cancer development for the population in arsenic-affected areas. Non-cancer risks (hazard indexes) were estimated at 11.01 for adults. Our observations revealed that the highest bioaccumulation of arsenic occurred in the hair of cows, and goats in the examined localities. The biotransformation factor (BTF) for hair was much higher compared to other excreted samples from both species. The calculated BTF followed the order: hair > feces > milk for cows and goats. Livestock farmers in Nadia district are advised to carefully select feed resources, prioritizing those high in crude protein and low in neutral detergent fiber, and they should provide drinking water from deep aquifers to ensure the safety of milk and meat for human consumption.

Activated carbon-mediated arsenopyrite oxidation and arsenic immobilization: ROS formation and its role

The oxidative dissolution of arsenopyrite (FeAsS) is a significant source of arsenic contamination in nature. Activated biochar (AC), a widely used environmental remediation agent, is prevalent in ecosystems and participated in various geochemical processes of arsenic and iron-containing sulfide minerals. However, the impact of AC-arsenopyrite association on reactive oxidation species (ROS) generation and its contribution to As transformation were rarely explored. Here, ROS formation and the redox conversion of As during the interaction between AC and arsenopyrite were investigated. AC-mediated arsenopyrite oxidation was a two-stage process. At stage I, the heterogeneous electron transfer from arsenopyrite facilitated O2 reduction on AC, enhancing arsenopyrite dissolution and ROS formation. TBA, PBQ and catalase inhibited 86.40 %, 79.39 % and 49.66 % of As(III) oxidation, respectively, indicating indicated that HO˙, (O2•)- and H2O2 were responsible for As(III) oxidation. However, at stage II, the mobility of As was highly restricted, especially increasing AC addition. Besides adsorption, AC retained appreciable As through catalyzing insoluble ferric arsenate formation and growth by promoting Fe(II) and As(III) oxidation and functioning as nuclei. These findings deepen our understanding of the coupling behavior of AC-arsenopyrite and its influence on geochemical cycling of arsenic in mined surroundings, which has important implications for mitigating arsenic pollution.

Effective Removal of Arsenic from Copper Matte by Sodium Carbonate

Residual arsenic in copper matte is a source of arsenic contamination in subsequent processes in the smelting section of copper pyrometallurgy. In order to solve the impact of arsenic in copper matte on the subsequent process of smelting, this study removes arsenic from copper matte by adding an arsenic removal agent to the molten copper matte. The results show that the most difficult arsenic phase in copper matte is the residual arsenic in copper-arsenic alloys, based on which sodium carbonate was selected as the arsenic removal agent. The arsenic content in the copper matte was reduced by 98% under the optimal experimental conditions of a reaction temperature of 1250 °C, 4% sodium carbonate addition, and a reaction time of 60 min. The experimental results of the reaction mechanism show that sodium carbonate plays two main roles in the process of removing the intractable residual arsenic in copper matte. One is that sodium carbonate has a low melting point, which enhances the fluidity of the reactants. The other is that it can provide oxygen to the reaction system and convert arsenic in the copper-arsenic alloy into gaseous arsenic and arsenate. This study can provide new ideas for controlling arsenic pollution in copper pyrometallurgy.

Stabilization and Remediation of Arsenic-Contaminated Soil: Fly Ash-Based Technology for Industrial Site Restoration

Arsenic contamination of various environmental components poses a serious threat to human and animal health. Soil As contamination is particularly hazardous, as soil is a vital pathway to the food chain. We conducted experiments on soil from a typical pharmaceutical and chemical industry relocation site in Hubei Province, focusing on modification using fly ash through mechanical and chemical mechanisms. We subjected varying proportions of lime, ferrous sulfate, and fly ash to mechanical ball milling and used these mixtures to perform remediation of arsenic-contaminated soil and site restoration. Our findings are as follows: in soil culture experiments, the As stabilization efficiency reached 90% within 90 days with ferrous salt-modified fly ash. In actual site restoration, As-stabilization efficiency exceeded 95% across different soil depths within 30 days, demonstrating significant stabilization effects. Optimal modified dosages were determined as 2% ferrous sulfate and 2% fly ash. After stabilization, As in the soil primarily existed in amorphous iron-aluminum oxide-bound (F3) and crystalline iron-aluminum oxide-bound (F3 + F4) and residual (F5) states. Fluctuations in the moisture content and pH mainly activated F3 and F4, transitioning them into exchangeable (F1) and surface-adsorbed (F2) states. Arsenic leaching was predominantly associated with the F1 form. Fly ash-based restoration technology demonstrates promising capabilities in waste treatment and pollution control, offering significant potential for widespread application.

​Statistical-based optimization and mechanism assessments of Arsenic (III)​ adsorption by ZnO-Halloysite nanocomposite​

Arsenic contamination in aqueous media is a serious environmental problem, especially in developing countries. In this research, the Box-Behnken response surface methodology was used to optimize the most relevant variables affecting arsenic adsorption on the ZnO-halloysite surface, including temperature, adsorbent dosage, pH, contact time, and As (III) initial concentration. The regression analysis indicated that the experimental data were appropriately fitted to a quadratic model with the adjusted R-squared value (R2) of 0.982 for As(III) adsorption capacity and a linear model with R2 of 0.931 for As(III) removal. The p-values for both adsorption capacity and removal efficiency were below 0.05, with F-values of 116.91 and 115.58, respectively, supporting the model’s validity. The optimum conditions for maximum removal of As(III) were determined through numerical and graphical optimization using the desirability function. It was found that the optimum conditions for adsorption were pH = 7.99, contact time of 3.99 h, As(III) initial concentration of 49.96 mg/L, and adsorbent dosage of 0.135 g/40 ml. The accuracy of the optimization procedure was confirmed by a confirmatory experiment, which showed a maximum arsenic removal of 91.31% and an adsorption capacity of 12.63 mg/g under optimized conditions. Moreover, XPS analysis was performed at different pH levels to investigate the As (III) adsorption mechanism. The results demonstrated that As(III) adsorption occurs at acidic and neutral pH levels. On the other hand, when pH is increased to 8, As (III) oxidizes to As (V), and then adsorption occurs.

Assessing Arsenic Contamination in Groundwater: A Comprehensive Review of NCR Districts in Haryana.

Assessing Arsenic Contamination in Groundwater: A Comprehensive Review of NCR Districts in Haryana.

Environmentally Sustainable Detection of Arsenic using Convolutional Neural Networks and Imidazole-Based Organic Probes: Application in Food Samples and Arsenic Album.

Arsenic contamination poses a significant health risk, particularly when it infiltrates water supplies. While current detection methods offer precise analysis, they often involve complex instrumentation not suitable for field use. This study presents a novel approach by developing two probes, A1 and A2, based on 4-diethylaminosalicyladehyde, 2-hydroxy-1-naphthaldehyde, and 1,2-diaminoanthraquinone. These probes are highly sensitive and selective for detecting arsenite (As(III)) and arsenate (As(V)) in water, food samples, and homeopathic medicine with limits of detection in the nanomolar range. To elaborate our contribution to on-site arsenic detection, we introduce a convolutional neural network-based image recognition system. This system interprets images of the probes' colorimetric response, effectively categorizing different ranges of arsenic concentrations in parts per million (ppm). Our approach offers a real-time, cost-effective, and user-friendly solution for arsenic detection, extending its applicability from scientific laboratories to in-field conditions and even household monitoring. The findings fill critical research gaps in real-time detection methods, potentially revolutionizing the way we monitor environmental contaminants like arsenic.

Kinetics, Thermodynamics, and Mechanistic Studies of Arsenic Removal Utilizing Natural Soil as Adsorbent.

The contamination of water sources with the heavy metal contaminant arsenic (As) causes substantial risks to humans, animals, and other living organisms. Therefore, the introduction of methods for the removal of As is important. The present study aimed to investigate the adsorption model and mechanism of As removal utilizing natural soil adsorbents. The batch adsorption technique was used to analyze the impacts of various parameters such as contact time, initial As concentration, pH, and temperature. Adsorption mechanisms were studied through adsorption kinetic, isotherm, and thermodynamic models. The batch adsorption study findings indicate that the optimal conditions for maximum As removal were achieved by application of 2.2 g of adsorbents in 50 μg/L of As solution for 60 min of contact time at a pH of 5.5 ± 0.5 and a temperature of 40 °C. The highest removal efficiency was achieved when red soil was employed as the adsorbent. The kinetic, isotherm, and thermodynamic models revealed that As adsorption was a chemisorptive, nonspontaneous, and endothermic process.

Arsenic Contamination in Eastern India: Exploring the Impact, Mitigation, and Bioremediation Strategies

Arsenic Contamination in Eastern India: Exploring the Impact, Mitigation, and Bioremediation Strategies

NATURAL EXPOSURE TO ARSENIC-INDUCED GENOTOXIC EFFECTS IN DIABETIC AND NON-DIABETIC INDIVIDUALS

Arsenic contamination in drinking water is a global health issue linked to various adverse health outcomes, including genotoxic effects. Understanding these effects in different populations, including diabetic and non-diabetic individuals, is critical for developing targeted public health interventions. Objective: This study aimed to investigate the genotoxic effects of arsenic exposure in diabetic and non-diabetic individuals residing in arsenic-contaminated and control areas. Methods: In this cross-sectional study conducted from January to June 2024, 100 participants were recruited from areas with known differences in arsenic water contamination levels. Participants were divided equally between arsenic-contaminated and non-contaminated regions, with 15 diabetic and 20 non-diabetic individuals selected from each group. A standard questionnaire was administered to collect demographic data and medical history. Additionally, 12 water samples from the contaminated area were analyzed for arsenic concentration. Genotoxic effects were assessed using the comet assay, and DNA damage was quantified using an empirical numerical rating system. Results: Significant DNA damage was observed in the blood cells of individuals from the arsenic-contaminated area compared to those from the non-contaminated area. Diabetic individuals showed similar patterns of DNA damage to non-diabetics within the same exposure group. Even in the non-contaminated group, slight DNA damage was detected, suggesting potential contributions from other environmental factors. Conclusion: The findings demonstrate that arsenic exposure is associated with significant genotoxic effects in both diabetic and non-diabetic populations. DNA damage in non-contaminated areas also indicates a possible impact of other environmental factors. These results highlight the need for ongoing monitoring and mitigation strategies to address arsenic contamination and its health impacts.

Two-dimensional distribution of arsenic species in the riparian zone regulated by As-Fe co-transformation under varying river water proportions and bicarbonate concentrations

Arsenic (As) contamination of groundwater is a major issue in global environmental health. In the riparian zone, mixing river water and groundwater with different substances is proposed to affect arsenic transformation and distribution. However, the distribution of arsenic species in the riparian zone and its co-transformation with iron under varying river water proportions and bicarbonate (HCO3–) concentrations remain unclear. The two-dimensional distributions of arsenic species, including exchangeable (Ex-As), carbonates-bounded (Carb-As), FeMn(hydr)oxide-bounded (Ox-As), organic-bounded (Om-As) and residual arsenic (Res-As), were investigated in three typical profiles of the riparian zone near the lower reaches of the Hanjiang River, China. The apparent enrichment of arsenic in the pore water, either As(III) and As(V), and in the sediment, mainly Carb-As and Ox-As, were observed in the profiles. The correlation analysis showed that the distributions of arsenic species in the riparian zone were primarily related to dissolved or total organic matter (DOC or TOC), Fe, HCO3–, dissolved oxygen (DO) and oxidation–reduction potential (Eh). Further batch experiments mixing simulated river water and groundwater with different proportions and HCO3– concentrations demonstrated that the forming of the arsenic-rich area in the riparian sediment was derived from the oxidation of Fe(II) and As(III) from groundwater, controlled by the varying DO from river water and HCO3– from organics degradation. These results provide more knowledge of the transforming process of arsenic in the riparian zone and a better understanding of the role of the riparian zone in arsenic restraint.

Arsenic contamination in rice consumption in Bandung city - West Java

Abstract Arsenic contamination in rice is of concern due to the potential health risks associated with various health problems, including certain types of bladder and lung cancers and skin lesions. Arsenic is a naturally occurring element that can be found in soil and water and its contamination in rice is possible. Meanwhile, rice is a staple food in Indonesia and its consumption is widespread across the country. According to the US Department of Agriculture, Indonesia is the world’s fifteenth-largest rice consumption with 128.6 kg per capita per year thus arsenic in rice is a concern. This study was conducted to measure the arsenic contamination in rice consumed by people in Bandung. Bandung was preferably selected due to its high population. As the capital city of West Java, its population hits more than 2.5 million and places it as the 5th most populated area in Indonesia. Ten rice samples were collected from a traditional market in Bandung, West Java. The sample was prepared using the Indonesian Regulation Standard (SNI) method and measured by ICP-MS. The arsenic concentration in rice was found varies between 0.0775-0.2550 mg/kg. The maximum allowable arsenic content for consumption based on the Indonesian National Standard (SNI) is 0.4 mg/kg, according to the World Health Organization (WHO) is 0.3 mg/kg, and according to the European Commission Standard for parboiled milled rice, the maximum level is 0.15 mg/kg. The HQAs value was higher than 1 (HQAs &gt; 1), the rice in Bandung Market have potential for non-carcinogenic risk in long-term. ILCRAs result in this study between ILCR &gt; 10−3 and &gt;10−4 indicates threshold cancer risk for rice consumption. By calculating the ILCR, scientists and policymakers can prioritize interventions, implement regulatory measures, and develop strategies to reduce exposure levels, ultimately mitigating the potential cancer risks within a given population. It is important to note that the study should be continued over the next few years, to monitor the potential health risks associated with consuming contaminated rice.

Development of cost-effective inorganic arsenic extraction method for resource-limited regions: Analysis of efficiency and regulatory implications

This study evaluated the effectiveness of coke and lemonade extraction methods compared to the standard 1 % v/v HNO3 method for determining inorganic arsenic (iAs) concentrations in rice bran samples using a field-deployable method (Arsenator field kit). The limit of detection (LOD) for the methods was 45 μg kg−1, comparable to existing literature. The extraction efficiencies were assessed by comparing iAs recovery rates, with coke extraction yielding the highest recovery of 127.4 %, followed by lemonade at 116.2 %, and HNO3 at 100 %. Statistical analysis indicated strong correlations between the extraction methods, particularly between HNO3 and coke (Pearson correlation coefficient, 0.990), suggesting that coke extraction is a reliable alternative to the traditional HNO3 method. However, lemonade extraction showed a lower correlation (0.940) and higher false negative rates, indicating potential limitations for regulatory compliance. Notably, at the maximum contaminant limit (MCL) of 0.100 mg kg−1, coke extraction produced an 8 % false positive rate with no false negatives, while lemonade extraction had an 8 % false positive rate and a 17 % false negative rate. This study underscores the potential of coke extraction as a cost-effective and efficient alternative for assessing iAs levels in rice products, especially in resource-limited settings. Recommendations include the standardization of coke extraction protocols and the development of robust monitoring programs to ensure food safety and public health protection against arsenic contamination. Overall, the findings contribute valuable insights for improving arsenic detection methods and regulatory compliance in food safety practices.

Potential of Heavy Metals and Microplastics Contamination in River Mpanga, Fort Portal, Kabarole District, Uganda

Anthropogenic environmental pollution is a major development challenge in Ugandan rivers and lakes, the key drivers being industrialization, agriculture, and urbanization. The aim of the study was to assess the potential of heavy metal and microplastic contamination in River Mpanga, Fort Portal, Uganda. Triplicate water and sediment samples were collected from three sampling sites, preserved, and analyzed at the Chemistry Department, Makerere University for heavy metals, while microplastics analysis was conducted at NaFIRRI, Jinja. Sediment heavy metal contamination was assessed from the geoaccumulation index, while microplastic characterization and quantification were determined from stereomicroscopy and morphological features. Arsenic was the most prevalent metal with a mean concentration of 13.2 ppm thus higher than permissible maximum limits of WHO. The mean concentrations (ppm) of copper, lead, and cadmium were 0.01, 0.01, and 0.001 respectively, and below the permissible maximum. Sediment samples revealed very strong arsenic contamination, strong contamination for copper, moderate to strong contamination for lead, and a potential lack of contamination for cadmium. The higher concentrations of the heavy metals in the sediments compared to water could be attributed to bioaccumulation, as evidenced by the high geoaccumulation values. Microplastics occurred throughout the river and included fragments, filaments, film, pellets, form, and fibers. The presence of heavy metals and microplastics was attributed to anthropogenic activities within the river vicinity, which discharged heavy metal-laden waste into River Mpanga. High arsenic concentrations and sediment accumulation of contaminants pose serious potential public health threats to the local communities.

Nectopsyche sp (Trichoptera: Leptoceridae) sublethal effects caused by different concentrations of arsenic (As): a biochemical markers approach.

Environmental impacts related to arsenic (As) contamination are a persistent issue of particular interest in Latin American countries with increasing mining activities. In Ecuador, the redefinition of public policies to promote the increase in mining since 2008 has led to a significant rise in the presence of this heavy metal in rivers and effluents, sometimes exceeding the 0.1 mg L-1, limit recommended by Ecuadorian Environmental Regulations. This study aimed to evaluate the sublethal effects through the detection of biochemical biomarker changes (Catalase, Antioxidant capacity by FRAP, and Glutathione S-transferase) generated in larvae of Nectopsyche sp following prolonged exposure to different concentrations of As (C1 = 0.05 mg L-1, C2 = 0.1 mg L-1, C3 = 0.8 mg L-1) in a controlled environment, emulating the maximum limits allowed by current Ecuadorian legislation. While As concentration levels in water increased, so did levels in the tissue of Nectopsyche sp specimens. On the other hand, behavioral parameters (mortality and mobility) did not show differences in either time or As concentrations. However, both Catalase and Antioxidant capacity by FRAP levels tended to decrease with increasing As concentration, and in both cases, the differences were significant. Additionally, Glutathione S-transferase activity did not increase significantly. These results preliminarily demonstrate that biochemical responses change with varying As concentrations in Nectopsyche sp and are affected at behavioral and biochemical levels produced by the As at chronic levels.