Decrease In Metal Concentrations Research Articles

Dicranopteris pedata improves soil quality by enhancing nutrient deposition, decreasing metal concentration, and boosting microbial diversity on abandoned rare earth elements mining sites

Rare earth elements (REEs) mining exerts adverse impacts on soil ecosystems. Attempts to recover REEs-contaminated soils have been made through phytoremediation with Dicranopteris pedata. However, how it improves soil quality is still poorly understood. This study fully investigated the effects of D. pedata-aided phytoremediation on abandoned REEs mining sites, focusing on soil properties, REEs speciation, and microbial diversity. Results showed that D. pedata increased soil TC from 488 to 626 mg kg–1, soil TN from 20.1 to 57.0 mg kg–1, and soil TP from 232 to 259 mg kg–1, while decreased concentrations of soil Fe, Mn, and REEs by 37 %, 62 %, and 43 %, respectively. The plant efficiently removed labile REEs and elevated non-labile fractions. Additionally, D. pedata increased microbial diversity and reshaped microbial composition, with microbial communities such as p_Chloroflexota and p_Acidobacteriota being decreased from 22–47 % to 17–27 % (p < 0.01), and p_Pseudomonadota, p_Acidobacteriota, p_GAL15, and p_Bacteroidota being increased from 0.25–16 % to 5.3–26 % (p < 0.01). Several communities belonging to these phyla significantly correlated to soil properties and metal concentrations, suggesting their roles in improving soil quality. This study provides new insights into soil quality improvement after D. pedata aided-phytoremediation and highlights the beneficial use of phyto-microbial technology for remediating abandoned REEs mining sites.

Distribution, source identification, and contamination level of trace metals in the sediment of the Shari-Goyain River in Bangladesh: Implications for ecological health risks

The major issue associated with coal mine drainage is its contribution to river pollution, which occurs at the local, regional, and global levels. The pollution of surface sediment by heavy metals is a major environmental and health concern in coal mining and downstream areas. This study explored the concentrations of eight metal components in the sediments from the Shari-Goyain River of Bangladesh. The trend of decreasing metal concentration was identified as Fe > Mn > Ni > Zn > Cu > Cr > Pb > Cd in sediment. The level of metal pollution in the study area was assessed by using various indicators like geo-accumulation index (Igeo), pollution load index (PLI), contamination factor (CF), potential ecological risk factor, and risk index (RI). The sediment in the river exhibited PLI values ranging from 0.133 to 0.543, suggesting a low level of pollution from the evaluated heavy metals (PLI < 1). The mean Igeo showed that the study area was unpolluted whereas Ni showed unpolluted to moderately polluted status. For most of the metals, the sediment samples recorded a low degree of contamination (CF < 1) except Pb, Cd, and Ni which exhibited moderate degree of contamination (1 ≤ CF < 3). Through the application of various statistical analyses, coal mine drainage has been identified as the possible source of pollution of the analyzed metals in the Shari-Goyain River. However, the risk index and RI suggested a low risk of metal pollution in the studied areas. To improve the environmental conditions of the Shari-Goyain River, it is crucial to construct permanent sediment quality monitoring stations and conduct extensive ecological investigations.

Polyurethane sponges bearing cucurbituril adsorb Cr(III) and Pb(II) ions from contaminated water samples.

Water contamination with toxic metals causes harmful effects on the environment and to human health. Although cucurbiturils have carboxyl groups in their portal that can interact with metal ions, there is a lack of studies about their use as metal adsorbent. This scenario has motivated conduction of the present study, which addresses the use of cucurbit[6]uril (CB[6]) and cucurbit[8]uril (CB[8]) for adsorbing Pb and Cr from water samples, in free forms and immobilized in poly(urethane) sponges. The adsorption kinetics revealed that CB[8] leads to faster adsorption compared to CB[6], with equilibrium achieved in 8h for CB[8] and 48h for CB[6] for both metals, and achieved up to 80% of decrease in metal concentration. The Langmuir isotherm model provided a better description of adsorption for Cr and Pb in CB[6] and Pb in CB[8] with a maximum concentration adsorbed of 32.47mgg-1 for Pb in CB[6], while the Dubinin-Radushkevich model was more suitable for Cr adsorption in CB[8]. Sponges containing CB[6] and CB[8] have proven to be efficient for Pb and Cr remediation in tannery effluent samples, reducing Cr and Pb concentration by 42 and 33%, respectively. The results indicate that CB[6] and CB[8], whether used in their pure form or integrated into sponges, exhibit promising potential for efficiently adsorbing metals in aqueous contaminated environments.

Impact of Varied Lead Concentrations on Lead Accumulation in the Body, Heart and Gill Damage of Milkfish (Chanos chanos)

Milkfish (Chanos chanos) is valued in aquaculture for its affordability and nutritional richness. However, conventional farming techniques frequently result in suboptimal yields due to lead (Pb) contamination. Traditional milkfish ponds are typically situated near coastal areas, river waters, estuaries, ports, and industrial zones, rendering them susceptible to contamination, particularly from heavy metals, like Pb. This study aimed to analyze Pb accumulation in the body of milkfish juvenile, identify liver and gills damage, and examine the growth rate and survival of milkfish exposed to Pb at various concentrations. Juvenile milkfish were exposed to various concentrations of PbNO3, namely 0 mL.L-1, 0.08 mL.L-1, 0.8 mL.L-1, and 8 mL.L-1, including the non-exposed control group. The metal content of the fish bodies was measured using an AA spectrophotometer. Histological analysis of the liver and gills of the fish was performed to evaluate organ damage. The results showed significant Pb accumulation has been observed in milkfish exposed to high Pb concentrations. The control treatments showed a decrease in metal content, whereas treatments with high concentrations showed a significant increase. Exposure to Pb within 30 d can cause organ damage, such as inflammatory cells, secondary lamella fusion, and necrosis that occurs in the gills. In the liver, there is damage such as the accumulation of inflammatory cells, necrosis, and hydrofic degeneration. Pb exposure rapidly damages and disrupts milkfish's biological functions, influencing survival and growth. Pb exposure with doses 8 mL.L-1 significantly affected juvenile milkfish within approximately 60 min.

Reduction in acidity and heavy metal concentrations of acid mine drainage with organic matter and coal fly ash treatments in two different reclaimed-mining soils

Organic matter (OM) has a very crucial role in the management of acid mine drainage (AMD) using a passive treatment system, although information on the use of this system in different reclaimed-mining soils (RMS) is very limited. Therefore, this study aimed to determine the effect of adding OM to RMS with different characteristics. It was carried out by adding only OM or in combination with coal fly ash (CFA) to two RMS with different characteristics (Palam and Cempaka Soils) and quartz sand (control) in a batch reactor experiment. This was followed by the incubation of the mixture of soil/quartz-OM or soil/quartz-OM-CFA at 60% water holding capacity for 15 days. After incubation, AMD slowly flowed into the reactor, and its pH in the reactor was monitored every day for 30 days, while the concentrations of Fe (iron), Al (aluminum), and Mn (manganese) were measured on the 30th day. The results showed that the application of OM on Palam Soil only increased AMD pH by 0.38 units, while Cempaka Soil and quartz sand increased by 4.83 and 5.36 units, respectively. The addition of OM to Cempaka Soil and quartz sand also showed a higher reduction in heavy metals concentration in AMD than those in Palam Soil. It was also discovered that the application of OM combined with CFA led to a higher improvement in AMD quality than only using OM. This study demonstrated that the effect of OM addition on increasing pH and decreasing metal concentration on AAT management with the passive treatment system is controlled by soil characteristics.

Transition of an estuarine benthic meiofauna assemblage 1.7 and 2.8 years after a mining disaster.

Estuaries are transitional coastal ecosystems that are threatened by multiple sources of human pollution. In 2015, mining tailings from an upstream dam failure caused massive metal contamination that impacted benthic assemblages on the Brazilian Rio Doce estuary. In this study, we investigate and compare meiofaunal assemblages with eDNA metabarcoding 1.7 years (2017) and 2.8 years (2018) after the initial contamination by mine tailings in order to evaluate the continued impact of sediment mine tailing contaminants on the structure of benthic assemblages after the disaster. The community was dominated by Arthropoda and Nematoda 1.7 yr after the impacts (42 and 29% of meiofaunal sequence reads, respectively) but after 2.8 years Arthropoda (64.8% of meiofaunal sequence reads) and Rotifera (11.8%) were the most common taxa. This continued impact on meiofaunal assemblage revealed a lower phylogenetic diversity (7.8-fold) in 2018, despite overall decrease in metal concentration (Al, Ba, Cr, As, Fe, Zn, Mn, Pb, Cd, Co) in sediments. Our data suggests that differences in benthic assemblages and loss of diversity may be influenced by contaminants in sediments of this estuary, and indicate that broad eDNA assessments are greatly useful to understand the full range of biodiversity changes in dynamic estuarine ecosystems.

Evaluating the impact of Nalla Lai contamination on drinking quality of groundwater in Rawalpindi city, Pakistan

Abstract The scientific report assessed the impact of Nalla Lai wastewater on the groundwater quality of Rawalpindi city, Pakistan. A total of 19 wastewater and 49 groundwater samples were collected during September and October 2016 and have been analyzed in the laboratory to detect different water quality parameters. The results revealed that BOD (biological oxygen demand), COD (chemical oxygen demand), iron, and cadmium values in many wastewater samples were beyond the recommended value of the National Environmental Quality Standards 1997 (NEQs, 1997). In groundwater samples, the results of iron, cadmium, manganese, zinc, TDS (total dissolved solids), pH, color, and hardness were found elevated from the standard values in one or more samples as compared with the National Standard for Drinking Water Quality, 2010 (NSDWQ, 2010). The decreasing metal concentration order in groundwater samples was iron &amp;gt; zinc &amp;gt; manganese &amp;gt; copper &amp;gt; cadmium. Very interestingly, hardness was found at elevated levels in 75% of investigated groundwater samples. Microbiological contamination was detected in 83% of the analyzed groundwater samples. The study revealed the percolation of heavy metals and microbial contamination in the bore water, tube wells, hand pumps, springs, and hand-dug wells located nearby the Nalla Lai wastewater stream.

Integrated Assessment of Chemical and Biological Recovery After Diversion and Treatment of Acid Mine Drainage in a Rocky Mountain Stream.

Responses of stream ecosystems to gradual reductions in metal loading following remediation or restoration activities have been well documented in the literature. However, much less is known about how these systems respond to the immediate or more rapid elimination of metal inputs. Construction of a water treatment plant on the North Fork of Clear Creek (NFCC; CO, USA), a US Environmental Protection Agency Superfund site, captured, diverted, and treated the two major point-source inputs of acid mine drainage (AMD) and provided an opportunity to investigate immediate improvements in water quality. We conducted a 9-year study that included intensive within- and among-year monitoring of receiving-stream chemistry and benthic communities before and after construction of the treatment plant. Results showed a 64%-86% decrease in metal concentrations within months at the most contaminated sites. Benthic communities responded with increased abundance and diversity, but downstream stations remained impaired relative to reference conditions, with significantly lower taxonomic richness represented by a few dominant taxa (i.e., Baetis sp., Hydropsyche sp., Simulium sp., Orthocladiinae). Elevated metal concentrations from apparent residual sources, and relatively high conductivity from contributing major ions not removed during the treatment process, are likely limiting downstream recovery. Our study demonstrates that direct AMD treatment can rapidly improve water quality and benefit aquatic life, but effectiveness is limited, in part, to the extent that inputs of metals are captured and treated. Consideration should also be given to the effects of elevated major ion concentrations from the treated effluent not removed during the lime treatment process. Continued chemical and biological monitoring will be needed to quantify the NFCC recovery trajectory and to inform future remediation strategies. Environ Toxicol Chem 2023;42:512-524. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Studi Adsorpsi Logam Berat Besi (Fe) dan Timbal (Pb) Air Sungai Mahakam oleh Limbah Cangkang Telur dan Abu Gosok

Waste could be found easily anywhere such as eggshells and rubbing-ash. Being a non-usable rubbish, These type of waste can be usefull in someways with a right treatment and deep research on compound material with in. The physical content from these waste utilized to be an adsorbent, it adsorbs a metal content e.g Mahakam river water sample. Main purpose of this research was based on benefical content from eggshells and rubbing-ash as their ability decreasing metal content. This study concluded experimentally using adsorbtion methods, a device such as Atomic Absobtion Spectrophotometer (AAS) was used to test the decreasing effect on logam content. The obtained data from testing process used to analyzed a metal concentration that disolved in water sample. This study results on decreasing metal concentration such as Fe and also Pb on Mahakam river water sample. Fe concentrat on these water sample shows decline rate from 1,5 mg/L to 0,11 mg/L given certain treatment adding eggshels powder. And also Pb content reduced from 1,69 mg/L to 0,24 mg/L indicate a little waste content from treated water sample. Inference from this study suggest addition of eggshells and rubbing-ash waste in form of powder had decreasing-effect on soluble metal content from Mahakam River water sample.&#x0D;

Polymer Nanocomposite Containing Palladium Nanoparticles: Synthesis, Characterization, and Properties.

Composite nanomaterials have been prepared through thermal decomposition of palladium diacetate. The composite contains palladium nanoparticles embedded in high-pressure polyethylene. The materials were studied by a number of different physico-chemical methods, such as transmission electron microscopy, X-ray diffraction, X-ray absorption spectroscopy, electron paramagnetic resonance, and EXAFS. The average size of the nanoparticles is 7.0 ± 0.5 nm. It is shown that with the decrease of metal content in the polymer matrix the average size of nanoparticles decreased from 7 to 6 nm, and the coordination number of palladium also decreased from 7 to 5.7. The mean size of palladium particles increases with the growing concentration of palladium content in the matrix. It is shown that the electrophysical properties of the material obtained depend on the filler concentration. The chemical composition of palladium components includes metallic palladium, palladium (III) oxide, and palladium dioxide. All samples have narrow lines (3–5 Oe) with a g factor of around two in the electron paramagnetic resonance (EPR) spectra. It is shown that EPR lines have uneven boarding by saturation lines investigation. The relaxation component properties are different for spectral components. It leads to the spectrum line width depending on the magnetic field value. At first approximation, the EPR spectra can be described as a sum of two Lorentzian function graphs, corresponding to the following two paramagnetic centers: one is on the surface, and one is inside the palladium particles. Some of the experimental characteristics were measured for the first time. The data obtained indicate interesting properties of palladium-based nanocomposites, which will be useful for obtaining products based on these materials.

Removal Efficiency, Accumulation and Biochemical Response of Lemna minor L. Exposed to Some Heavy Metals

Both terrestrial and aquatic plants can be used for removing various pollutants such as hydrocarbons, heavy metals, etc via phytotechnology. This study applied different concentrations of Cd, Pb, and Cr (1, 4, and 8) mg/L to evaluate heavy metal removal and toxicological effects on Lemna minor L. in laboratory experiments for 12 days. At the beginning and the end of experiments, the parameters were measured, including fresh weight, relative growth rate (RGR), total chlorophyll, protein, and proline content, as well as other parameters measuring at the end of experiments such as metal remaining in water, removal efficiency, and bioconcentration factor(BCF) in plant. The results demonstrated a decrease in metal concentrations in aqueous solution at all treatments with different values. The highest removal efficiencies were Pb >Cr >Cd, respectively. It was 88.8 % at the 1 mg/L of lead and 22.22 % at 8 mg/L of Cd. The toxicological effects on plants as a response to selected metals were increased with increasing concentrations and periods of exposure. The reduction in fresh, dry weight, t. chlorophyll, and protein content were more in Cd>Cr>Pb respectively compared with increased in control treatments. The highest reduction at 8 mg/L of Cd were 0.329 µg/gram, 18.656 % for total chlorophyll and protein content respectively. The result showed the proline content increased with increasing concentration and the value was highest in Cd>Cr>Pb. The results suggest that Lemna minor L. is a good candidate for treating polluted water with heavy metals.

Developing diatom-based inference models to assess lake ecosystem change along a gradient of metal smelting impacts: Sudbury lakes revisited.

Mining and smelting activities have strongly influenced the Sudbury region (Ontario, Canada) since the late 19th century, leading to acidification and metal contamination in many local ecosystems. Regulations on restricting acidic emissions were enacted in the 1970s, after which a considerable volume of paleolimnological work was completed to study the impacts of acidification on Sudbury-region lakes and their subsequent biological recovery. Twenty years after the last regional diatom-based assessment, many lakes have undergone large changes in limnological variables, including increases in pH and dissolved organic carbon concentrations, as well as decreases in metal concentrations. Additionally, these lakes are under the potential impacts of newly emerging environmental stressors such as climate warming and road salt contamination. Here, we revisited a suite of Sudbury-region lakes (n = 80) to examine the relationships between their current water chemistry and diatom assemblages preserved in surface sediments using a canonical correspondence analysis. Although the pH gradient in our study lakes is shorter (pH ~1.4) than in earlier calibration studies conducted in this region, lake water pH was still identified as the strongest environmental variable shaping diatom distributions and was used to construct a robust inference model (R2boot = 0.73; RMSEP = 0.32). By assessing ecological changes experienced by a subset of these Sudbury-region lakes (n = 33) over the past few decades, we identified two major trends: an overall increase in diatom-inferred pH and a rise in the relative abundance of planktonic taxa. Our study provides useful insights into the autecology of major diatom taxa in acidified waters and highlights the importance of considering other anthropogenic stressors when assessing the recovery response of acid-impacted systems.

Mass-Balance Modeling of Metal Loading Rates in the Great Lakes

Major elements and nutrients are key water quality monitoring targets in the Great Lakes, but large-scale and long-term data for (trace) metals remains comparatively scarce. Consequently, the sources and processes controlling metal loading rates and potential accumulation in the lakes are not as well constrained. Here, we present a comprehensive assessment of select metal loads in the Great Lakes basin, aggregating tributary and connecting channel loads as well as estimates for atmospheric input and sedimentation. In total, 26,845 hydrometric and water quality datapoints from major environmental surveillance programs were compiled into mass-balance calculations and dynamic simulations for 1980–2020. Conservative element (Na, Cl) loads were used to calibrate the black-box approach, and mass-balance for these elements could be achieved at ≥90% and long-term trends accurately reproduced. In contrast, biogeochemically reactive (trace) metals Cu, Ni, Zn and Pb displayed highly variable source-sink behavior across the Great Lakes. Our results show that i) atmospheric inputs, tributary loads, and sedimentation all affect the concentrations and temporal trends of the studied metals but differently in the upper versus lower lakes, ii) smaller tributaries can be disproportionately important to lake-wide metal budgets, and iii) current loading rates may yield increasing lake-wide average Cl concentrations (e.g., up to 2.3 mg/L in Lake Superior) but decreasing metal concentrations (e.g., down to <0.25 μg/L Cu in Lake Ontario) by 2100. This work provides important quantitative baselines for metal loads in the Great Lakes and may help optimize surveillance and management strategies for the preservation of Great Lakes water quality.

Study of reduction of iron (Fe), copper (Cu) and lead (Pb) concents in leachate using electrocoagulation method with aluminum (Al) electrode

Leachate can be defined as the liquid resulting from the decomposition of waste and infiltration of rainwater in the landfill. Leachate has unique characteristics, it has a high content of organic, metals, acids, dissolved salts and microorganisms and due to the complex leachate content it requires processing in treating leachate. Electrocoagulation is one of technology that can be applied to remove organic and heavy metal content in leachate. In this study, it was seen how the effect of voltage and contact time using aluminum electrodes on decreasing the concentration of Fe, Cu and Pb in leachate then calculating the reduction efficiency of Fe, Cu and Pb. The treatment of electric voltages given in this study were 4, 8 and 12 volts with a contact time of 15, 30 and 45 minutes. The results showed metal removal reached 0.030 mg/L, 0.007 mg/L and 0.010 mg/L and with efficiencies of 99.476%, 99.364% and 98.214% for Fe, Cu and Pb parameters. The decrease in metal content by 21.8% is influenced by voltage and 3.74% is influenced by the contact time when tested using the Pearson Correlation Test. These results indicate that the leachate treatment process with electrocoagulation processing has great efficiency.

ИЗМЕНЧИВОСТЬ КОНЦЕНТРАЦИИ КАДМИЯ И СВИНЦА В ВОДЕ КРУПНОЙ РАВНИННОЙ РЕКИ ЗА 30-ЛЕТНИЙ ПЕРИОД НАБЛЮДЕНИЙ

The article presents new analytical data on the content of cadmium and lead in river water obtained by the authors using highly sensitive specialized methods of analytical spectrometry. For the first time, a more than thirty-year (1983-2018) study has been carried out, tracing the concentration of elements in the mid-stream water of the Oka River in the area of Prioksko-Terrasny Biosphere Reserve (PTBZ) - a location remote from the zone of formation of technogenic dispersion flow. The general trend was found to be characterized by a gradual decrease in metal content, correlating with the implementation of various environmental measures in the river basin. The trend of decreasing concentration is well expressed for cadmium from 1983 to 1991 and is weaker from 1992 to 2018. Estimates are made of the average regional anthropogenic-dependent concentrations of elements in the Oka River waters, exceeding the Clark (background) values for the world’s rivers significantly. It can be predicted that, if this trend persists, cadmium concentrations in the water of a large plain river will approach the background values for surface waters of the Russian plain.

Key factors influencing metal concentrations in sediments along Western European Rivers: A long-term monitoring study (1945–2020)

Since 1945, a large amount of heterogeneous data has been acquired to survey river sediment quality, especially concerning regulatory metals such as Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Large-scale syntheses are critical to assess the effectiveness of public regulations and the resiliency of the river systems. Accordingly, this data synthesis proposes a first attempt to decipher spatio-temporal trends of metal contamination along seven major continental rivers in Western Europe (France, Belgium, Germany, and the Netherlands). A large dataset (>12,000 samples) from various sediment matrices (bed and flood deposits – BFD, suspended particulate matter – SPM, dated sediment cores – DSC) was set up based on monitoring and scientific research from the 1950s to the 2010s. This work investigates the impact of analytical protocols (matrix sampling, fractionation, extraction), location and time factors (related to geology and anthropogenic activities) on metal concentration trends. Statistical analyses highlight crossed-interactions in space and time, as well as between sediment matrices (metal concentrations in SPM ≃ DSC > BFD) and extraction procedures (also related to river lithology). Major spatio-temporal trends are found along several rivers such as (i) an increase of metal concentrations downstream of the main urban industrial areas (e.g. Paris-Rouen corridor on the Seine River, Bonn-Duisburg corridor on the Rhine River), (ii) a long-term influence of former mining areas located in crystalline zones, releasing heavily contaminated sediments for decades (Upper Loire River, Middle Meuse section), (iii) a decrease of metal concentrations since the 1970s (except for Cr and Ni, rather low and stable over time). The improvement of sediment quality in the most recent years in Europe reflects a decisive role of environment policies, such as more efficient wastewater treatments, local applications of the Water Framework Directive and urban industrial changes in the river valleys.

Impact of mine pit lake on metal mobility in groundwater

Open pit mines are potential source of metal contamination. Three types of open pit mines, i.e. copper, quartzite and granite were selected to understand the mobility and behaviour of metals. Metal contamination due to abandoned open pit copper mines (Average Cu = 64.57 ± 90 µg/L) is observed more comparative to quartzite (Average Cu = 20.42 ± 34.39 µg/L) and granite mines (Average Cu = 9.67 ± 7.94 µg/L). Acid mine drainage (AMD) from copper mines result in dissolution of metals and contaminates groundwater in the downstream direction. Correlation used for source assessment confirms the influence of anthropogenic or abandoned pit mine on metal concentration in groundwater. It is observed that the impact of abandoned pit mine is more compared to tailings and overburden dumps. Dissolution and precipitation process control the metal abundance in downstream groundwater. Precipitation dominates dissolution process with distance and results in decrease in metal concentration. It also confirms the self-neutralisation and self-attenuation capacity of the aquifer. The study recommends restoration of abandoned open pit mines to their natural conditions to avoid metal contamination in downstream.

Holo- and hemimetabolism of aquatic insects: Implications for a differential cross-ecosystem flux of metals.

Increased metal concentrations in aquatic habitats come as a result of both anthropogenic and natural sources. Emerging aquatic insects that play an indispensable role in these environments, transferring resources and energy to higher trophic levels in both aquatic and terrestrial habitats, may inadvertently also act as biovectors for metals and other contaminants. This study measured levels of 22 different metals detected in biofilm, aquatic and terrestrial life stages of Trichoptera and Odonata, as well as riparian spiders, to examine the uptake and transfer from freshwater to terrestrial ecosystems. We show that emerging insects transfer metals from aquatic to terrestrial ecosystems, however with large losses observed on the boundary of these two environments. Significantly lower concentrations of most metals in adult insects were observed in both hemimetabolous (Odonata) and holometabolous insect orders (Trichoptera). In holometabolous Trichoptera, however, this difference was greater between aquatic life stages (larvae to pupae) compared to that between pupae and adults. Trophic transfer may have also played a role in decreasing metal concentrations, as metal concentrations generally adhered to the following pattern: biofilm>aquatic insects>terrestrial invertebrates. Exceptions to this observation were detected with a handful of essential (Cu, Zn, Se) and non-essential metals (Cd, Ag), which measured higher concentrations in adult aquatic insects compared to their larval counterparts, as well as in aquatic and terrestrial predators compared to their prey. Overall, all metals were found to be bioavailable and biotransferred from contaminated waters to terrestrial invertebrates to some degree, suggesting that risks associated with metal-contaminated freshwaters could extend to terrestrial systems through the emergence of these potential invertebrate biovectors.

Cleanup of sewage sludge spiked with Cd, Cu, and Zn: Sludge quality and distribution of metals in the “soil-plant-water” system

Corn was grown under greenhouse conditions in the presence of uncleaned versus cleaned municipal sewage sludge to assess the effectiveness of a chemical leaching process that uses an inorganic acid and strong oxidants to clean biosolids (i.e., to remove metals without reducing their agronomic potential). Specifically, our study analyzed physicochemical sludge from the Montreal (MSL) wastewater treatment plant (WTP) and biological sludge from the Becancour (BSL) WTP. Both biosolids were spiked with individual metals (dry weight basis): Cd (100 mg kg-1), Cu (3000 mg kg−1), and Zn (5000 mg kg−1), or their mixture. MSL biosolid enrichment led to the solubilization of added metals and removed 84–88% of Cd, 78–79% of Cu, and 79–81% of Zn. Similarly, BSL biosolid enrichment resulted in the removal of 86–88% of Cd, 80–81% of Cu, and 88–89% of Zn. The fractional distribution of metals varied between biosolids depending on their production process, stabilization, and initial metal concentration. In the MSL biosolids, only Cu partitioning was influenced by spiking, cleanup, and washing. The three metals (Cd, Cu, and Zn) occurred either in their crystalline phase or were linked to Fe oxide, organic matter, or carbonate. In the BSL biosolids, the metals that were not in their crystalline phase were only associated with Fe oxide. This study demonstrated that 99% of Cd and Cu and 97% of Zn contents remained in the soil; however, biosolid cleanup generally decreased metal concentrations in plants, leachate, and/or soil.

Numerical modeling of a double-walled spherical reservoir

Extensive and important class of multilayer shell structures is three-layer structures. In a three-layer structure, a rigid filler plays an important role, due to which the bearing layers are spaced that gives the layer stack high rigidity and durability with a relatively low weight. By combining the thicknesses of the bearing layers and the filler, the desired properties of a three-layer shell structure can be achieved. Compared with traditional single-walled, three-layer construction has increased rigidity and durability, which allows reducing the thickness and weight of the shells.&#x0D; In order to reduce the metal content of the spherical reservoir for storing liquefied gases, this work considers the design of a double-walled reservoir, in which the inter-wall space is filled with reinforced polyurethane. Numerical modeling made it possible to determine the parameters of the stress-strain state of the structure with an error of no more than 5 %. It has been established on the example of a reservoir with a volume of 4000 m3 that the spatial structure of the spherical reservoir wall can reduce the metal content up to 19 %. Field of application for the research results is the assessment of the stress-strain state of spherical reservoirs at their designing.&#x0D; Method for building the structure of a double-walled spherical reservoir in the SCAD software has been developed, which allows calculating the stress-strain state (SSS) by the finite element method.&#x0D; Numerical model of a double-walled spherical reservoir has been developed. It was found that to obtain calculation results with an error of P ≤ 5 % the size of the final element should not exceed 300×300×δ mm.&#x0D; Design of a double-walled spherical reservoir was investigated. Design parameters have been established to ensure the operational reliability of the structure with a decrease in metal content in comparison with a single-wall reservoir by 19 %.