Maximum Acceptable Concentration Research Articles

A systematic workflow of data mining confirms widespread ecological risks of SDHIs fungicides contamination in aquatic environment.

Succinate dehydrogenase inhibitors (SDHIs) are widely utilized fungicides that have been detected in various environments, raising significant concerns regarding their toxicity to aquatic organisms. A comprehensive analysis of SDHIs contamination and associated ecological risks has been challenging due to scattered data and varying scale. This study consolidated residue data from 194 aquatic environments across six regions, up to June 2024, providing an overview of SDHIs distribution and conducting a global-scale aquatic ecological risk assessment. We analyzed 20 SDHIs, with boscalid, fluopyram, flutolanil, fluxapyroxad, mepronil, and thifluzamide being the most frequently detected across Asia, Europe, North America, South America, Africa, and Australia. The concentrations and types of SDHIs varied significantly among continents, with data sourced from water, sediment and aquatic organisms. Utilizing a web-based Interspecies Correlation Estimation-Species Sensitivity Distribution (ICE-SSD) model, we identified substantial sensitivity differences among species, with benzovindiflupyr showing the lowest LC50 of 3.5 μg/L, indicating a high risk when concentrations exceed 0.035 μg/L (Maximum Acceptable Concentration, MAC). Risk quotient (RQ) values revealed that flutolanil posed high risks to eight aquatic ecosystems and medium risks to five, while boscalid presented medium risk to one ecosystem. Our findings also demonstrated a significant correlation between the aquatic ecotoxicity of SDHIs and their characteristics (log Kow, solubility, and pKa). Collectively, we advocate for the restricted use of SDHIs and emphasize the necessity for further evaluation of their environmental behavior and integrated risks within the "One Health" framework.

Simultaneous synthesis of sulfonated reduced graphene oxide@graphene oxide hybrid material for efficient electrochemical sensing of silver ions in drinking water

One of the most important concerns around the world nowadays is the drinking water quality. Silver ions (Ag+) are one of the heavy metal ions that can seriously degrade the water quality and therefore, the human health. Hence, the World Health Organization (WHO) fixed the maximum acceptable concentration of these ions in drinking water at approximately 0.93 µM. Thus, the development of cost-effective and efficient techniques and tools that can help to quantify Ag+ ions in drinking water is of great importance. Herein, we used a new, simple, eco-friendly and low-cost synthesis route to synthesize a sustainable hybrid carbon material, namely sulfonated reduced graphene oxide@graphene oxide (S-rGO@GO) that was utilized as electrode material for Ag+ ions electroanalysis in drinking water. The successful synthesis of S-rGO@GO was evidenced by XRD, Raman spectroscopy, XPS, FE-SEM and EDX. The electrochemical characterization of S-rGO@GO revealed its good affinities towards Ag+ and its good electron transport abilities. The sensor prepared from S-rGO@GO (S-rGO@GO/GCE) showed good repeatability and reproducibility. S-rGO@GO/GCE optimization revealed that its best performance is achieved when 5 µL of 1 mg/mL of S-rGO@GO suspension in ultrapure water is used for its fabrication and when the electrodeposition (Ag+ to Ag0) is carried out at -0.1 V vs. SCE for 200 s. The calibration of S-rGO@GO/GCE exhibited a linear relationship in the concentration range of 0.2 to 1.4 µM, with a sensitivity of (0.605 ± 0.015) µA/µM; the statistic LOD was found to be 0.0007 µM. Furthermore, S-rGO@GO/GCE has shown a great potential for real samples analysis.

Geographic Information Systems for Water Quality Modeling in the Zhytomyr District Communities

Abstract To ensure safe and quality drinking water for residents of rural settlements who use their own wells, boreholes, and natural sources for domestic water supply, a comprehensive approach to evaluating the quality of underground drinking water using geographic information system (GIS) technologies is necessary. The purpose of the study was to assess the quality of drinking water sources of noncentralized water supply in rural settlements of the united territorial communities (UTCs) of Zhytomyr district and to create geoinformation models based on the research results. The following research methods were used during the research: analytical, field, laboratory, statistical, calculation, and cartographic. The research was conducted in 129 settlements of 12 UTCs of Zhytomyr district, where drinking water samples were collected from noncentralized water supply sources for further analysis in the Measurement Laboratory of Polissia National University, and the creation of geoinformation models using the ArcGIS Pro software package. It has been proven that the average pH level in none of the studied settlements exceeded the norm. The average nitrate concentration in the drinking water from noncentralized water sources exceeded the norm by 1.4–3.5 times, specifically in the water of the Pulyny, Cherniakhiv, Vilshanka, Volytsia, and Oliivka communities, exceeding the maximum acceptable concentration (MAC) limit by more than two times. Only in rural settlements in the Liubar community was the average iron content found to be above the norm by more than 1.9 times. Overall, it was established that the calculated value of the overall water quality class in the Zhytomyr district was 2.03, which is determined as “good,” clean water of acceptable quality. The best water quality was found in the Vilshanka, Cherniakhiv, and Stanyshivka communities, with a quality class range of 1.85–1.93, while the worst water quality was recorded in the Oliivka, Teterivka, and Liubar communities, with a quality class range of 2.13–2.31. It was determined that the highest contribution to the overall water quality was made by nitrate and iron content. The obtained research results and models based on them can be used by local governments of the studied communities to inform the population about the quality of drinking water and to develop a plan for improving the state of drinking water supply with the aim of increasing the level of environmental safety of drinking water.

Switchable hydrophilicity solvent-based hollow fibre liquid-liquid microextraction – headspace gas chromatography for determination of benzene and its derivatives in water samples


 
 
 
 A novel, cost-effective, simple and environmentally friendly method was developed for separating, preconcentrating and quantifying volatile analytes. That approach utilised switchable hydrophilicity solvent-based hollow fiber liquid-liquid microextraction in combination with headspace gas chromatography. The extraction was carried out from 1 l of water solution. 100 μl of nonanoic acid, immobilised within a polypropylene capillary, was selected as an extraction solvent. After the extraction, the capillary with the extract was transferred to a headspace vial, and headspace gas chromatographic analysis was performed. To facilitate the transition of volatile analytes to the headspace for subsequent analysis, nonanoic acid was converted to hydrophilic nonanoate by adding a sodium hydroxide solution.
 The effectiveness of the suggested strategy was demonstrated in the determination of benzene and its derivatives in water samples. Various parameters affecting the extraction and headspace gas chromatographic determination were investigated and optimised. Under the optimal conditions, the analytical characteristics of the proposed technique were determined.
 Using this approach, the limits of quantification for all analytes were found to be below the maximum acceptable concentration.
 
 
 

Assessing the ecological impacts of polycyclic aromatic hydrocarbons petroleum pollutants using a network toxicity model

Polycyclic aromatic hydrocarbons (PAHs) are significant petroleum pollutants that have long-term impacts on human health and ecosystems. However, assessing their toxicity presents challenges due to factors such as cost, time, and the need for comprehensive multi-component analysis methods. In this study, we utilized network toxicity models, enrichment analysis, and molecular docking to analyze the toxicity mechanisms of PAHs at different levels: compounds, target genes, pathways, and species. Additionally, we used the maximum acceptable concentration (MAC) value and risk quotient (RQ) as an indicator for the potential ecological risk assessment of PAHs. The results showed that higher molecular weight PAHs had increased lipophilicity and higher toxicity. Benzo[a]pyrene and Fluoranthene were identified as core compounds, which increased the risk of cancer by affecting core target genes such as CCND1 in the human body, thereby influencing signal transduction and the immune system. In terms of biological species, PAHs had a greater toxic impact on aquatic organisms compared to terrestrial organisms. High molecular weight PAHs had lower effective concentrations on biological species, and the ecological risk was higher in the Yellow River Delta region. This research highlights the potential application of network toxicity models in understanding the toxicity mechanisms and species toxicity of PAHs and provides valuable insights for monitoring, prevention, and ecological risk assessment of these pollutants.

Development of Plum Seed-Derived Carboxymethylcellulose Bioink for 3D Bioprinting.

Three-dimensional bioprinting represents an innovative platform for fabricating intricate, three-dimensional (3D) tissue structures that closely resemble natural tissues. The development of hybrid bioinks is an actionable strategy for integrating desirable characteristics of components. In this study, cellulose recovered from plum seed was processed to synthesize carboxymethyl cellulose (CMC) for 3D bioprinting. The plum seeds were initially subjected to α-cellulose recovery, followed by the synthesis and characterization of plum seed-derived carboxymethyl cellulose (PCMC). Then, hybrid bioinks composed of PCMC and sodium alginate were fabricated, and their suitability for extrusion-based bioprinting was explored. The PCMC bioinks exhibit a remarkable shear-thinning property, enabling effortless extrusion through the nozzle and maintaining excellent initial shape fidelity. This bioink was then used to print muscle-mimetic 3D structures containing C2C12 cells. Subsequently, the cytotoxicity of PCMC was evaluated at different concentrations to determine the maximum acceptable concentration. As a result, cytotoxicity was not observed in hydrogels containing a suitable concentration of PCMC. Cell viability was also evaluated after printing PCMC-containing bioinks, and it was observed that the bioprinting process caused minimal damage to the cells. This suggests that PCMC/alginate hybrid bioink can be used as a very attractive material for bioprinting applications.

Improving conventional household greensand treatment for efficient Mn(II) removal from drinking water

Geogenic contaminants pose a global threat to ensuring access to safe drinking water. Manganese (Mn) is a naturally-occurring redox-active element which in its reduced form, Mn(II), is a widespread groundwater contaminant. Prolonged consumption of water containing high levels of Mn has been linked to adverse effects on memory, attention, motor skills, and nervous system function, particularly in vulnerable groups including pregnant individuals and young children. In addition, Mn can lead to aesthetic issues such as altered taste, clogging, and damage to plumbing systems. While Mn has historically been regulated as an aesthetic concern, a mounting body of evidence linking health issues to Mn exposure through drinking water has heightened the challenges of using groundwater to meet drinking water needs. Recently, Health Canada established a health guideline which set a maximum acceptable concentration for total Mn in drinking water of 120 μg/L. Greensand (GS) filters are commonly used in conventional drinking water treatment systems for Mn(II) removal due to their cost-effectiveness and high exchange capacity. However, under certain conditions conventional GS systems may have a low Mn(II) removal efficiency (Galangashi et al. 2021) and encounter challenges related to Mn leaching (Outram et al. 2018), resulting in failure to meet health-related standards. Furthermore, GS filters typically undergo regeneration using potassium permanganate (KMnO4), a mild oxidant that results in the release of additional Mn waste byproducts during the regeneration of the filter. Recent research suggests that Mn-containing materials can effectively activate peroxymonosulfate (PMS) and produce reactive oxygen species (ROS) that facilitate contaminant degradation. This study aims to investigate whether PMS may be used to improve greensand treatment systems and enhance Mn(II) removal from drinking water. Batch experiments were performed to test the Mn(II) removal efficiency across a range of PMS concentrations (0-500 μM) and GS mass (0.1-3 g). Aqueous Mn concentrations were measured over time using inductively coupled plasma optical emission spectrometry (ICP-OES). Solid-phase reaction products were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The mechanisms of Mn oxidation were identified by quenching experiments and electron paramagnetic resonance (EPR) spectroscopy. The activation of PMS by greensand significantly increased the removal efficiency of Mn(II) compared to the conventional method (e.g., 96.83(±3.77)% at PMS = 500 µM vs. 5.77(±11.1)% at PMS = 0 µM). Our results attribute the mechanism underlying increased Mn removal in our improved treatment method to advanced oxidation processes that involve free radicals (e.g., hydroxyl radical (·OH) and sulfate radical (SO4·-)) and non-free radical pathways, with Mn oxides as the main oxidation products. This study provides a new treatment method for more efficient Mn(II) removal while simultaneously reducing Mn wastes produced during the regeneration cycle which allows for a more sustainable and holistic management of invaluable groundwater resources.

Seawater quality criteria and ecotoxicity risk assessment of zinc oxide nanoparticles based on data of resident marine organisms in China

Water quality criteria (WQC) for zinc oxide nanoparticles (ZnO NPs) are crucial due to their extensive industrial use and potential threats to marine organisms. This study conducted toxicity tests using marine organisms in China, revealing LC50 or EC50 values for ZnO NPs ranging from 0.36 to 95.6 mg/L across seven species, among which the salinity lake crustacean zooplankton Artemia salina exhibited the highest resistance, while diatom Phaeodactylum tricornutum the most sensitive. Additionally, the EC10 or maximum acceptable toxicant concentration (MATC) values for ZnO NPs were determined for five species, ranging from 0.03 to 2.82 mg/L; medaka Oryzias melastigma demonstrated the highest tolerance, while mysis shrimp Neomysis awatschensis the most sensitive. Based on the species sensitivity distribution (SSD) method, the derived short-term and long-term WQC for ZnO NPs were 138 μg/L and 8.37 μg/L, respectively. These values were further validated using the sensitive species green algae Chlorella vulgaris, confirming effective protection. There is no environmental risk observed in Jiaozhou Bay, Yellow River Estuary and Laizhou Bay in the northern coastal seas of China. This study provides important reference data for the establishment of water quality standards for nanoparticles.

Occurrence, source identification and ecological risk assessment of heavy metals in water and sediments of Uchalli lake – Ramsar site, Pakistan

Uchalli Lake is an internationally significant Ramsar site that needs protection for supporting migratory birds. The current study aimed to assess wetland health by examining water and sediments utilizing total and labile heavy metals concentration, pollution indices, ecological risk assessment, water recharge and pollution induction sources through isotope tracer techniques. Al concentration in water was of serious concern as it was 440 times higher than the maximum acceptable concentration of Environmental Quality Standard of the UK for aquatic life in saline waters. Labile concentration predicted very severe enrichment of Cd, Pb, and moderate enrichment of Cu. Modified ecological risk index predicted very high ecological risk in sediments. The δ 18O, δ2H and D-excess values indicate that the lake was mainly recharged by local meteoric water. Enriched values of δ 18O and δ2H suggest a high evaporation of lake water, making lake sediments more enriched with metals. Isotopic and D-excess values of groundwater suggest a quick rainwater recharge to groundwater around the Uchalli Lake. Nitrates isotopes indicate that the rainwater runoff is main source of induction of fertilizers, pesticides and soil bonded metals in the lake system. The lake is recharged by rainwater runoff, from catchment areas, that erode the soil particles and agricultural residual waste dumped in the lake.

Occurrence and environmental risk assessment of 22 pesticides in Brazilian freshwaters

Pesticide contamination in water resources is a global threat. Although usually found at low concentrations, pesticides raise considerable toxicological concerns, mainly when mixtures are considered. The occurrence of 22 pesticides (2,4 D, alachlor, aldicarb, aldrin, atrazine, carbendazim, carbofuran, chlordane, chlorpyrifos, DDT, diuron, glyphosate, lindane, mancozeb, methamidophos, metolachlor, molinate, profenofos, simazine, tebuconazole, terbufos, and trifluralin) was investigated, through consolidated database information, in surface freshwaters of Brazil. Moreover, scenarios of environmental risk assessment considering isolated compounds and mixtures were performed, as well as a meta-analytic approach for toxicity purposes. Pesticides in freshwater have been reported from 719 cities (12.9% of Brazilian cities), where 179 (3.2%) showed pesticide occurrence above the limit of detection or quantification. Considering cities with more than five quantified, 16 cities were prone to environmental risks considering individual risks. However, the number increased to 117 cities when the pesticide mixture was considered. The mixture risk was driven by atrazine, chlorpyrifos, and DDT. The national maximum acceptable concentrations (MAC) for nearly all pesticides are higher than the predicted no-effect concentration (PNEC) for the species evaluated, except aldrin. Our results show the need to consider mixtures in the environmental risk assessment to avoid underestimation and review MAC to protect aquatic ecosystems. The results presented here may guide the revision of the national environmental legislation to ensure the protection of Brazilian aquatic ecosystems.

Effects of Ammonia on Juvenile Sunray Surf Clam (Mactra chinensis Philippi) in Laboratory Tests

The current study aimed to determine the acute and sub-chronic toxicity of ammonia to juvenile surf clams (Mactra chinensis Philippi). Acute toxicity tests were conducted with seven concentrations of ammonium chloride using a 96 h static-renewal approach. Sub-chronic ammonia exposure tests (20 d exposures) were conducted with 6 concentrations at 20 °C. The 96 h median lethal concentration (96 h LC50) was 11.1 (10.0; 12.0) mg/L total ammonia nitrogen (TAN) and 0.56 (0.50; 0.60) mg/L unionized ammonia (NH3). The relative growth rate was significantly reduced at concentrations higher than 1.6 mg/L TAN (0.075 mg/L NH3) in the 20 d tests. The estimated maximum acceptable toxicant concentration (MATC) based on the reduced growth of juvenile M. chinensis was between 0.8 and1.6 mg/L TAN (0.038–0.075 mg/L NH3). Histopathological changes were evaluated in the surviving clams after 20 days of exposure. Exposure to 14.1 mg/L TAN (0.661 mg/L NH3) resulted in changes in the mantle, foot and digestive diverticulum. We also examined the antioxidant enzyme activities of superoxide dismutase (SOD) and catalase (CAT) in 10 d and 20 d at 6 different levels (plus a control) of ammonia from 0.8 mg/L to 14.1 mg/L TAN. Ammonia exposure at 0.8 mg/L TAN (0.038 mg/L NH3) significantly affected SOD and CAT activities. The level of enzymic activity decreased with the increasing concentration of TAN. The results improved our understanding of oxidative damage under ammonia exposure and provided data for the aquaculture of sunray surf clams.

Influence of Water Hardness on Chronic Toxicity of Potassium Chloride to a Unionid Mussel (Lampsilis siliquoidea).

Elevated concentrations of potassium (K) often occur in effluents from wastewater treatment plants, oil and gas production operations, mineral extraction processes, and other anthropogenic sources. Previous studies have demonstrated that freshwater mussels are highly sensitive to K in acute and chronic exposures, and that acute toxicity of K decreases with increasing water hardness. However, little is known about the influence of hardness on the chronic toxicity of K. The objective of our study was to evaluate the chronic toxicity of K (tested as KCl) to a commonly tested unionid mussel (fatmucket, Lampsilis siliquoidea) at five hardness levels (25, 50, 100, 200, and 300 mg/L as CaCO3 ) representing most surface waters in the United States. Chronic 28-day K toxicity tests were conducted with 3-week-old juvenile fatmucket in the five hardness waters using an ASTM International standard method. The maximum acceptable toxicant concentrations (geometric mean of the no-observed-effect concentration and the lowest-observed-effect concentration) increased from 15.1 to 69.3 mg K/L for survival and from 15.1 to 35.8 mg K/L for growth (length and dry wt) and biomass when water hardness was increased from 25 mg/L (soft) to 300 mg/L (very hard). These results provide evidence to support water hardness influence on chronic K toxicity to juvenile fatmucket. However, the chronic effect concentrations based on the more sensitive endpoint (growth or biomass) increased only 2.4-fold from the soft water to the very hard water, indicating that water hardness had a limited influence on the chronic toxicity of K to the mussels. These results can be used to establish chronic toxicity thresholds for K across a broad range of water hardness and to derive environmental guideline values for K to protect freshwater mussels and other organisms. Environ Toxicol Chem 2023;42:1085-1093. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

EVALUATION OF POTENTIALLY HAZARDOUS CONTAMINANTS IN ANTI-VIRAL HERBAL PRODUCTS USED IN CLINICAL PRACTICE

Objective: The main objective of this research was to collect information for consumers and practitioners of marketed non-registered preparations. According to the World Health Organization (WHO) (1998), only arsenic, cadmium, and lead have maximum acceptable concentrations in starting materials of 1.0, 0.3, and 10 ppm, respectively. The allowable limits for toxic heavy metals in raw herbal medicines (ppm) according to the WHO (2007) are 0.5, 2 ppm for mercury and chromium. Methods: The use of an atomic absorption spectrophotometer was used to determine the buildup of heavy metals such as arsenic (As), chromium (Cr), lead (Pb), mercury (Hg), and cadmium (CD) in commercialized formulations in India. A total of ten samples of herbal formulations containing Swertia chirata, Triphala, Haridra, Daruharidra, Kantakari, Brhati, Karcura, Sunthi, Marica, and Pippali were selected for this research. Results: The results of this survey show that levels of heavy metals exceeding the limits allowed in unlicensed herbal preparations marketed have been found in the plant-based formulations studied. The herbal formulations coded AV1, AV2, AV7, and AV8 were found to be contaminated by arsenic (As) and in AV2, AV4, AV6, AV7, AV8, and AV9 were found to be contaminated by lead (Pb) levels. Herbal formulations coded AV1, AV2, AV3, AV4, AV6, AV7, AV8, and AV9 were found to be contaminated by mercury level and chromium level was AV1, AV2, AV3, AV4, AV5, AV6, AV7, AV8, AV9, and AV10. Conclusion: This work shows that the heavy metal content has been found in plant-based formulations. Because these formulations accumulate in the body, they can damage the delicate organs of the patient.

Anodonta cygnea, a freshwater swan mussel, exposed to diazinon: toxicity thresholds in behaviour and physiology.

Swan mussels (Anodonta cygnea) have been suggested as suitable bioindicators for the presence of pollutants in the environment. Application of the physiological and behavioral markers in these sessile species can be beneficial for environmental monitoring. The present study aimed to investigate the relationship between the behavioral disorders of movement and siphoning associated with the inhibition of tissue Acetylcholinesterase (AChE). For experiments, overally 120 bivalves of Anodonta cygnea (mean total length 80.33 ± 6.7mm) were transported from the agricultural drains and canals in Sari county (Mazandaran Province, Iran) to our laboratory. First, the LC50-96h of diazinon was estimated according to the Organization for Economic Co-operation and Development (OECD1992) guideline with static water conditions. The sub-lethal toxicity pesticide experiments were conducted on the basis of the lowest observed effect concentration (LOEC) and the maximum acceptable toxicant concentration (MATC). The LC50-96h, LOEC, and MATC values of diazinon were 85.2, 42.1, and 8.5mg L- 1, respectively. Based on the observations of mussels' movement, the burrowing and displacement decreased with the concentration of toxicant in water. Moreover, the presence of diazinon in water and its exposure to experimental animals significantly reduces their siphoning rate. The RDA showed that the AChE activity had a higher correlation with the siphoning behavior than the movement behavior. The comparison of enzyme activity at different exposure and recovery times showed that there was a significant difference among the groups affected by the consumed pesticide (p = 0.001, between contrasts). The most remarkable morphometric characteristic was the siphon opening that was inversely correlated with the enzymatic activity. Studies in bioethics might benefit from paying attention to these traits that are directly related to the level of toxicity and behavioral adaptations required for animal survival.

Trihalomethanes in drinking water from three First Nation reserves in Manitoba, Canada.

Previous research indicates that the water distribution system used has a significant impact on the microbial quality of tap water sampled in First Nations reserves in Canada. This study tested tap water from homes in three First Nations reserves to compare the concentrations of four trihalomethanes and related water quality parameters between homes receiving piped water from a water treatment plant (WTP) versus homes equipped with cisterns that are filled by a water truck. Of all the samples collected across time from household taps, 75% of piped samples and 70% of cistern samples had TTHM concentrations exceeding Health Canada's maximum acceptable concentration (MAC) of 100µg L-1 total trihalomethanes (TTHMs) in treated water. In all communities and across sampling times, trichloromethane (CHCl3) was the dominant trihalomethane (42-96%) followed by bromodichloromethane (CHBrCl2) (3-37%) and dibromochloromethane (CHClBr2) (1-18%). Tribromomethane (CHBr3) always accounted for < 5% of TTHMs. Within each of the three First Nations reserves, the water distribution system had no significant effect on TTHM concentration at the household level. Sampling month had a significant effect on TTHM concentration due to temporal changes in dissolved organic carbon of the source water. Results suggest that families in the studied First Nations reserves receive drinking water with high TTHM concentrations and that improvements to the water treatment plant might be the most effective way to minimize trihalomethane formation.

Prielbrusye National Park Environmental Changes Due To Increasing Tourism Activity

Prielbrusye National Park is one of the most popular tourist destinations in Russia. In recent years internal tourism development, stimulated by restrictive measures (due to the COVID pandemic and geopolitical situation), resulted in significant growth of tourist flow to the national park’s territory. A surge in anthropogenic load on the park’s geosystems might degrade them and lead to environmental pollution. This research involved chemical studies of natural waters and snow from the south slope of the Elbrus and audit of the most popular tourist trails. The results have shown that in the snow alongside mountain hiking pistes to the Elbrus all the way up to 4,720 m above sea level (a.s.l.) oil stains concentration is up to 38 times higher than maximum acceptable concentration (MAC). Content analysis of heavy metals in snow cover on the Elbrus slopes and in the river Baksan has shown a significant rise in lead load over the period of 2015–2021 from the trace levels to 1.5 MAC, which is the result of increased anthropogenic load on the south slope of the Elbrus mountain. Ground observation of tourist trails has brought to light numerous patches of vegetation trampling, width extension and branching of the main trail, as well as campfire sites. The research results can be used as a rationale to take measures to reduce recreational load, to improve local geosystems’ condition and to develop a plan of action on nature conservation within the park’s territory.

Pilot Study on the Physical, Chemical, and Biological Determinants of Indoor Air Quality in University Classrooms

Abstract In the context of an escalating energy crisis, the burgeoning prevalence of remote work, and challenging climatic conditions, ensuring optimal indoor air quality (IAQ) has emerged as a pressing concern. This pilot study rigorously investigates the complex interplay between biological, chemical, and physical parameters that characterize IAQ, focusing specifically on university classrooms during active teaching sessions. Employing a comprehensive array of instrumentation – such as SAS SUPER ISO 100 for microbiological sampling, Aranet4 for monitoring relative humidity, temperature, and CO2 concentration, and PCE-PCO 1 and PCE-RSCM 16 for particulate matter (PM2.5 and PM10) quantification—the study spanned a duration of three days in November 2022 and covered classrooms of varying dimensions, both reliant on natural ventilation. An extensive collection of 52 microbiological samples were obtained and cultured on specialized growth media to differentiate between various classes of airborne microorganisms. Concurrently, the pilot study meticulously recorded students’ activity patterns, along with the temporal dynamics of window openings and closures. The colony-forming units per cubic meter (CFU/m3) fluctuated between 174 and 934 CFU/m3, with fungi constituting the majority. Furthermore, the CFU/m3 for fungi cultivated on Sabouraud Dextrose Agar ranged from 24 to 610 CFU/m3, whereas bacteria cultured on Trypticase Soy Agar and Mannitol Salt Agar exhibited ranges of 42–476 CFU/m3 and 42–254 CFU/m3, respectively. Contrasting these findings with extant guidelines that recommend microbiological contamination not exceeding 500 CFU/m3 highlights significant IAQ concerns. Thermal assessments revealed that the smaller classroom surpassed the acceptable indoor temperature threshold of 25 °C within an average duration of 50 minutes, while the larger classroom remained compliant. Notably, the highest CO2 concentrations recorded over the three-day period were alarmingly high: 2689 ppm, 1970 ppm, and 2131 ppm on the first, second, and third days, respectively. A 25-minute ventilation intervention was sufficient to reduce CO2 levels to 499 ppm, although existing literature stipulates that CO2 concentrations should not surpass 1000 ppm. Importantly, the pilot study highlighted the rapid increasing of PM2.5 and PM10 concentrations in crowded instructional settings, averaging 400 μg/m3 and 35 μg/m3, respectively. This underscores the necessity for a continuous air ventilation and purification mechanism during classroom activities. Despite these pivotal findings, the study identifies a glaring absence of standardized regulations or guidelines pertaining to maximum acceptable concentrations of particulate matter and microbial CFU in public indoor environments, indicating a critical area requiring immediate policy intervention.

Polycyclic Aromatic Hydrocarbon (PAH) Levels in Clarias gariepinus Dried with Traditional and Modern Smoking Kiln

The study compared the polycyclic aromatic hydrocarbon content of Clarias gariepinus dried by traditional and modern smoking methods at the teaching and research farm of the Department of Fisheries and Aquaculture Management, Nnamdi Azikiwe University Awka, Nigeria. The traditional method involved using firewood while the modern method involved using charcoal charged smoking kiln to dry the fish. Laboratory analysis of 16 polycylic aromatic hydrocarbons was done by gas chromatography. The traditionally smoked fish contained significantly higher (P&lt;0.05) concentrations of fluorene (0.63µg/ kg), anthracene (9.02µ/kg), Phenanthrene (3.34 µg/kg), pyrene (55.05 µg/kg) and benzo (a) anthracene (17.55 µg/kg) than the modern smoked fish. The average PAH concentration in traditionally smoked fish (14.568 µg/kg) was significantly higher (P&lt;0.05) than the average PAH concentration in the modern smoked fish (4.404 µg/kg). However the maximum acceptable concentration for most PAHs was not exceeded in the smoked fish samples, therefore fish studied was declared wholesome for human consumption. Recommendation of efforts geared towards processing fish with methods using charcoal smoke instead of wood smoke was upheld in order to reduce the levels of PAHs in smoke dried fish.

Radiative sky cooling in low-medium concentration photovoltaic systems

Low-medium concentration photovoltaics (LM-CPV) can significantly reduce cost by using cheap optical lenses to reduce the area of the solar cell. Recently, radiative sky cooling (RSC) has been demonstrated to be promising for CPV systems. However, in the reported designs of heat dissipation for CPV systems combining the radiative cooler and a heat sink, a simple flat heat sink was used. Therefore, the effect of the radiative heat dissipation was magnified, but the contribution of convection, which accounts for a significant share in the natural working environment of CPV, was inhibited. To give full play to the role of convection, in this paper, a heat dissipation design combining a radiative cooling layer (RCL) and a finned heat sink was proposed. The RCL was laid on the upper surface of the heat sink to enhance heat dissipation for RSC and realize the effects of thermal radiation. The contributions of the RCL in reducing the temperature of the device, heat dissipation, and obtaining a tolerable concentration ratio under different external environments were examined, and the law whereby the cooling effect of the RCL was influenced by the wind speed and ambient temperature was investigated. The results of numerical simulations shown that the proposed passive cooling device could ensure that the temperature of the solar cell did not exceed 71.5 °C at a concentration ratio of 200, and the maximum difference in temperature inside the device was less than 3.8 °C even in extremely harsh environments (wind speed, 0 m/s; ambient temperature, 50 °C), where this satisfies the requirements of heat dissipation in low-medium concentration silicon solar cells. The radiative heat dissipation power per unit area of the RCL was 201 W/m2, far exceeding the convective heat dissipation. Although the area of the RCL only accounted for 7.9 % of the total area of heat dissipation, its radiative ratio of heat dissipation exceeded 15 % of the total heat dissipation and led to a drop in temperature of 1.76 °C. Moreover, the increase in ambient wind speed significantly improved the cooling effect of the device, which could ensure the rise in the temperature of the solar cell relative to the environment to smaller than 5 °C. However, this also diluted the effect of radiative heat dissipation by the RCL. The increase in the ambient temperature significantly improved the ratio of radiative heat dissipation of the RCL to the overall heat dissipation, reaching 20.2 % when the concentration ratio was 100. In all cases, the cooling power per unit area of the RCL was higher than that of convective and conventional radiative heat dissipation. An even better cooling effect could be achieved by further increasing the relative area of the RCL. Finally, we found that the maximum acceptable concentration ratio of the device was approximately linearly related to the size of the heat sink, and using the RCL could enable the device to withstand an additional 10 ∼ 15 multiples of concentration. The work here provides a new technical option for reducing the cost and improving the efficiency of photovoltaic power generation through the systematic exploration of the influence of the RSC on cooling LM-CPV systems.

Study of fragmentation impact of small riverbeds by artificial waters on the quality of water resources

Purpose. Study the spatial distribution of artificial reservoirs in the Dnipropetrovsk region and fragmentation impact of small riverbeds on changes in the quality of water resources. Methodology. Field studies on the current state of small river basins were carried out, rivers were selected on the principle of different geographical location and levels of anthropogenic impact. Analytical laboratory studies of water salt composition and methods of mathematical analysis were used to establish the dependence coefficients of water mineralization level and fragmentation of the river basin on the water flow regulation. Findings. The structure of the spatial distribution of artificial reservoirs in the administrative districts of the region and their hydrological characteristics are generalized. It is shown that small volumes of accumulated water in relation to the total area of reservoirs are the cause of intensive heating and evaporation of water. Due to this, the hydrochemical parameters of water are worsen, which affects the environmentally safe water use. It was found that the level of mineralization, the content of sulphates and chlorides exceed the maximum acceptable concentrations in all studied rivers. There is a tendency of deterioration of water quality in the salt block, especially in rivers with significant regulation of artificial reservoirs. In this case, water salinity exceeds the norm by 712 times. Indicators of water mineralization of rivers with fewer ponds and less fragmentation of the river basin exceed the standards by 25 times. Originality. It is determined that among the main factors of anthropogenic impact on the state of aquatic ecosystems is the fragmentation of riverbeds by artificial reservoirs, which turned rivers into cascades of water evaporating ponds. There is a close relationship between the factors of water flow regulation and the level of water mineralization (coefficient of determination R2 =0.62), as well as the coefficient of fragmentation of the river basin (R2 = 0.61). This proves the possibility, in the conditions of research of small rivers, to estimate the degree of change (increase) of water mineralization level by the coefficient of water flow regulation Kw and the coefficient of river fragmentation by the area Practical value. The main directions and ways to normalize the ecological status of watercourses are given. The necessity of systematic study of the current ecological condition of small rivers of Dnipropetrovsk region and their basins is determined.