Migration Of Heavy Metals Research Articles

Microcystis-dominated paddy crusts enhancing the cadmium accumulation in rice plant (Oryza sativa L.)

Paddy crusts (PCs) influence seriously on the heavy metal migration and transformation in the paddy field system. However, their quantitative effect on heavy metal accumulation in rice plant has been rarely reported. In this study, the influence of microcystis-dominated PCs on Cd content and physicochemical properties of the surface soil, water and rice plants (Oryza sativa L.) during PCs' overall life cycle was investigated. During the PC growth period (0–15 d), the Cd content in the surface soil (0–10 cm) and water decreased by 10–20% due to the accumulation effect. However, during the perish period (15–35 d), the Cd content in the surface soil and water increased by 20–30%, as Cd stored in the PCs was re-released. Moreover, the decomposition of PCs produced a large amount of low-molecular-weight organic substances (<500 Da), significantly increasing the bioavailable acid-soluble Cd in the surface soil. Finally, the PCs increase 25–80% and 60–85% Cd content in rice root and shoot, respectively. A structural equation model demonstrated that the contribution to the Cd in rice roots in the sequence: Cd in surface water > PC > surface soil. Potted experiments using sandy, clay, sandy loam soil containing 0.8–3.5 mg/kg of Cd collected from six provinces’ paddy field in southern China confirmed that PCs increased the Cd accumulation in rice plants by as much as 25–80%. Consequently, the presence of PCs can enhance the Cd concentration in rice plants, and the removing PCs could be a potential effectively approach to reducing Cd content in rice plants.

The impact of microbial community structure changes on the migration and release of typical heavy metal (loid)s during the revegetation process of mercury-thallium mining waste slag

The effect of changes in microbial community structure on the migration and release of toxic heavy metal (loid)s is often ignored in ecological restoration. Here, we investigated a multi-metal (mercury and thallium, Tl) mine waste slag. With particular focus on its strong acidity, poor nutrition, and high toxicity pollution characteristics, we added fish manure and carbonate to the slag as environmental-friendly amendments. On this basis, ryegrass, which is suitable for the remediation of metal waste dumps, was then planted for ecological restoration. We finally explored the influence of changes in microbial community structure on the release of Tl and As in the waste slag during vegetation reconstruction. The results show that the combination of fish manure and carbonate temporarily halted the release of Tl, but subsequently promoted the release of Tl and arsenic (As), which was closely related to changes in the microbial community structure in the waste slag after fish manure and carbonate addition. The main reason for these patterns was that in the early stage of the experiment, Bacillaceae inhibited the release of Tl by secreting extracellular polymeric substances; with increasing time, Actinobacteriota became the dominant bacterium, which promoted the migration and release of Tl by mycelial disintegration of minerals. In addition, the exogenously added organic matter acted as an electron transport medium for reducing microorganisms and thus helped to reduce nitrate or As (Ⅴ) in the substrate, which reduced the redox potential of the waste slag and promoted As release. At the same time, the phylum Firmicutes, including specific dissimilatory As-reducing bacteria that are capable of converting As into a more soluble form, further promoted the release of As. Our findings provide a theoretical basis for guiding the ecological restoration of relevant heavy-metal (loid) mine waste dumps.

Study on The Transport and Transformation of Heavy Metal Lead from Agricultural Land in An Abandoned Mining Area in Southwestern Yunnan

In this paper, the heavy metals in the agricultural land around an abandoned mine in southwest Yunnan Province were taken as the object of study, 15 samples of topsoil, middle soil and deep soil were collected, and 5 maize plants were randomly selected in the soil sampling points to study the migration and transformation of heavy metal lead in the soil-maize system in the agricultural land around the abandoned mine. The results showed that the soils in the study area were enriched with heavy metal Pb, which was generally expressed as surface soil &gt; middle soil &gt; deep soil; the migration capacity of heavy metal Pb in different organs of maize: roots &gt; leaves &gt; stems and kernels. The results of the study can be used as a basis for judging the migration and transformation of heavy metals in soil-crop systems, providing new theoretical support for the migration of heavy metals in soils around abandoned mining areas, and promoting the ecological remediation of heavy metal pollution in agricultural land.

Vertical migration behavior simulation and prediction of Pb and Cd in co-contaminated soil around Pb-Zn smelting slag site

Heavy metal migration in soil poses a serious threat to the soil and groundwater. Understanding the migration pattern of heavy metals (HMs) under different factors could provide a more reasonable position for pollution evaluation and targetoriented treatment of soil heavy metal. In this study, the migration behavior of Pb and Cd in co-contaminated soil under different pH and ionic strength (NaCl concentration) was simulated using convective dispersion equation (CDE). We predicted the migration trends of Pb and Cd in soils after 5, 10, and 20 years via PHREEQC. The results showed that the migration time of Cd in the soil column experiment was about 60 days faster than that of Pb, and the migration trend was much steeper. The CDE was proved to describe the migration behavior of Pb and Cd (R2 > 0.75) in soil. The predicted results showed that Cd migrated to 15–20 cm of soil within 7 years and Pb stayed mainly in the top 0–6 cm of soil within 5 years as the duration of irrigation increased. Overall, our study is expected to provide new insight into the migration of heavy metal in soil ecosystems and guidance for reducing risk of heavy metal in the environment.

Synergy of phosphate and hyperthermophilic bio-drying reduces pollution of sludge bio-drying: Reducing ammonia emissions and heavy metal migration risk

Hyperthermophilic bio-drying has stronger organic matter degradation and drying ability than the conventional bio-drying. However, ammonia emissions during the hyperthermophilic bio-drying are significantly higher than those during the conventional bio-drying process due to the higher temperature and pH value. Phosphate has been reported to reduce ammonia emissions during composting. Meanwhile, both the degradation of organic matter and the addition of phosphate buffer can promote the formation of EPS. EPS exhibits strong passivation and adsorption properties for heavy metals and organic pollutants, thus positively impacting the control of pollution in bio-drying products. Furthermore, the formation of EPS and the risk of the migration of heavy metals during hyperthermophilic bio-drying have not been reported. According to the results, compared to conventional bio-drying, the hyperthermophilic bio-drying significantly increased the yield of EPS and generated more active groups, reducing the migration risk of Cu, Zn, Cr, Pb, Cd, As, and Ni. The comprehensive potential ecological risk was reduced by 29.71%, which was higher than the reduction achieved by conventional bio-drying (13.81%). The addition of phosphate significantly reduced the ammonia emissions from the hyperthermophilic bio-drying and retained more nitrogen. Meanwhile, it promoted the formation of EPS and the enrichment of active groups, further reducing the migration risk of heavy metals. Moreover, the addition of phosphate buffer further reduced the comprehensive potential ecological risk of the products obtained from.

Monitoring of the content and migration of heavy metals in the soils–melliferous plants–bees–beekeeping products system in biocenoses of the combat areas

Aim. To determine the specificities of perennial dynamics in the number of the main corn insect pests in different natural and climatic zones of Ukraine under climate change. Methods. The field, laboratory, mathematical methods were used. The materials of the phytosanitary entomological monitoring of the State Service of Ukraine on Food Safety and Con- sumer Protection (2005–2021) in the basic 161 enterprises in Ukraine’s regions using methodologically standardized annual registrations of the main harmful organisms of agrocenoses (Borzykh еt al, 2018). Six groups of the main corn insect pests were investigated: corn borers (Ostrinia nubilalis Hübner), wireworms (Elateridae) and false wireworms (Te- nebrionidae), cutworms (Noctuida), southern dusty surface beetle (Tanymecus dilaticollis Gyllenhal), cotton bollworm (Helicoverpa armigera Hübner), and cereal aphids (Schizaphis graminum) Rondani. The database of the Hydrometeoro- logical Center of Ukraine was used to analyze climate parameters (2005–2021). The statistical analysis of the data was conducted using MS Excel and the linear correlation-regression analysis according to Pearson, Student’s criterion was used to evaluate the reliability (probability) of the correlation coefficients. Results. The results of correlational analysis of the state of populations of the main corn insect pests demonstrated that climate change has not considerably affected the number of corn borers as well as wireworms and false wireworms in all the natural and climatic zones of Ukraine yet. A reliable moderate reverse correlation (r = –0.309) was found between the number of cutworms and the sum of effective temperatures (SET) only for the Forest-Steppe conditions – under the increase in the SET, the number of these insects was smaller. The number of the southern dusty surface beetle was in direct, reliable, moderate correlation (r = 0.335) with the SET in the Steppe, for instance, the pest responded to the increase in the SET with the rise in its number. The number of cotton bollworms in Polissia was in reliable moderate correlation (r = –0.489) with the SET. The number of cereal aphids was in a reliable moderate direct correlation (r = 0.529) with the SET in Polissia: at the increase in the SET, the number of these pests was increasing. Conclusions. Conclusions: Climate changes do not considerably affect the state of the populations of the main corn insect pests in all the natural and climatic zones of Ukraine yet: we found the correlations between the number of insect pests and the SET which did not exceed such values as weak, moderate, and conspicuous. Significant changes in the state of insect pest populations should be expected if the sum of effective temperatures during the vegetation period will considerably affect the performance and feeding qualities of the cultivated plants.

Migration and morphological transformation patterns of heavy metals on sludge cells and extracellular polymeric substances (EPS) under the influence of different treatments.

The impediment of sludge resource utilization stems from the presence of heavy metals within the sludge matrix. To optimize heavy metal removal techniques from undried sludge, it is essential to study the distribution of heavy metals in the sludge flocs structure and the changes in morphology in the sludge cells after different treatments. In this study, the sludge was subjected to chemical treatments using citric acid (CA), EDTA, and saponin, as well as electrokinetic treatment at 2 V/cm. The distribution and migration of Cu, Ni, and Zn in sludge flocs after various treatment methods were analyzed. The heavy metals were found to migrate from intracellular to extracellular polymeric substances (EPS) without causing extensive sludge cell lysis. They gradually diffused outward with the dispersion of the EPS layer. The migration efficiency of the three heavy metals in the sludge flocs was Zn, Ni, and Cu. This was mainly related to the initial distribution and morphology of the heavy metals. Under the influence of chemicals and an electric field, the acid-soluble and reducible heavy metals in the cells partially migrated to the EPS, while the stable heavy metals transformed into an unstable state. Furthermore, the order of chemical reagents in terms of their effect on the migration efficiency of heavy metals was CA > EDTA > Saponin, owing to the varying binding strengths of heavy metals and their impact on the degree of loosening of the EPS. Especially after CA treatment a greater proportion of Cu, Ni, and Zn were transferred from the cells to the EPS. The acidification effect near the anode during electrokinetic treatment intensifies the migration of heavy metals. This study provides basic research for subsequent engineering optimization aimed at removing heavy metals from sludge.

Effect of DOM derived from composting on the changes of Pb bioactivity in black soil

Exogenous dissolved organic matter (DOM) plays an important role in the migration and transformation of heavy metals in soil. This study investigated the effect of composting-DOM with different maturity on changes of Pb bioactivity in soil, and evaluated the soil environmental factors driving these changes. The results showed that the activating ability of DOM to Pb in chernozem and dark brown soil increased by 4.11%−22.42% and 13.22%−30.15%, respectively. And the order followed: fresh manure (FDOM) > immature compost (IDOM) > mature compost (MDOM). The pH and dissolved organic carbon (DOC) were the main factors driving the changes in diethylenetriaminepentaacetic acid extraction (DTPA) -Pb in chernozem and dark brown soil, respectively. In chernozem, the input of MDOM can reduce the proportion of easily mobile fractions of Pb. While, DOM promotes the transformation of Pb from organic bound and residual fractions to exchangeable and carbonate bound fractions under other conditions. Moreover, the input of DOM can also drive the transformation of Pb species by regulating soil pH, electrical conductivity (EC), organic matter (SOM), DOC, and enzyme activity.

Application and Parameter Optimization of Electro-Kinetic Geosynthetics Electrodes Based on the Wild Horse Optimizer in Horizontal Electric Field Sludge Dewatering

This study systematically compared the performance of five corrosion-resistant electrode materials for electro-dewatering. Through a comprehensive analysis of dewatering efficiency, energy consumption, and corrosion resistance, conductive plastic composite electrodes (EKG) were selected as the optimal electrode material for experimentation. Additionally, the impact of electric field strength and electrode spacing on the efficiency and energy consumption of electro-dewatering (EDW) was investigated. The results showed that the increase in electric field intensity could improve the solid content and dewatering efficiency of the sediments, but the corresponding energy consumption also increased. The increased spacing of the plates reduced the dehydration effect and increased the energy consumption. By employing the Wild Horse Optimization algorithm, empirical and multifactorial response models for the dewatering solidification process were established, aimed at predicting the dewatering performance and energy consumption. The study concludes that for the remediation of heavy metals, the electric field strength should not exceed 10 V/cm to avoid excessive heavy metal migration and potential adverse chemical reactions.

Effect of NaCl on the migration of heavy metals during the non-isothermal and isothermal combustion of sludge: Static and dynamic analyses

Chlorine has been proven to promote the volatilization of heavy metals during sludge combustion. This work compared the migration of heavy metals with NaCl addition under different combustion modes at 900 ℃. The combustion modes have less effect on the mineral phase of residues, but the volatilization and toxicity reduction of heavy metals were more pronounced under isothermal combustion. The mineral evolution, release of Cl, and migration of metals were dynamically tracked by the continuous sampling at different combustion time under isothermal combustion. It was found that the volatile matter and fixed carbon burned almost simultaneously, and the addition of NaCl promoted them. As combustion proceeded, the minerals gradually crystallized and the heavy metals were volatilized due to the direct and indirect chlorination. Meanwhile, the chlorination and volatilization of Zn was less than that of Pb due to its effective solidification by minerals. The combination of the adsorption by exposed char and solidification by sludge minerals influenced the dynamic leaching behavior of metals. These results will help understand the interactions between heavy metals, inorganic Cl, and Fe-Si-Al minerals during combustion, which will further help optimize the combustion strategy for both stabilization or enrichment of heavy metals when inorganic chlorine exists.

Impact Assessment of Electroplating in the Leaching of Harmful Metals from Utensils

AbstractElectroplating is a widely used technique in the manufacturing of utensils for household and commercial use. This process involves the deposition of a metal coating onto a base material, such as steel or brass, to improve the aesthetics, durability, and corrosion resistance of the utensil. Several studies have investigated the migration of heavy metals from utensils, but there is a lack of research specifically focused on the impact of electroplating on this phenomenon. Therefore, this research article aims to assess the impact of electroplating by analyzing the migration of heavy metals from such utensils. The objective of this research is to assess the impact of electroplating on the migration of heavy metals from utensils. The research also aims to evaluate the impact of coating thickness. Stainless‐steel and brass utensils (Plate, Tumbler, and Bowl) are purchased. The samples are analyzed as per standard test methods based on inductively coupled plasma mass spectrometry (ICP‐MS) techniques. Leaching stimulant is used for extraction process. Testing is performed in an ISO/IEC 17025: 2017 accredited laboratory. The experiments reveal that the electroplating process decreased the migration of lead from the utensils. These findings highlight the need for stricter regulations and standards to ensure the safety of electroplated utensils.

Migration and Transformation of Heavy Metal and Its Fate in Intertidal Sediments: A Review

Intertidal sediments are rich in biological resources, which are important for material circulation and energy exchange. Meanwhile, these areas can be treated as sinks as well as sources of coastal heavy metal pollutants. Due to the influence of the tide, the intertidal sediments are in a state of periodic flooding and exposure, and environmental factors such as dissolved oxygen, salinity and overlying water pressure are changeable. Heavy metals in sediments are prone to migration and transformation with the dynamic effects of tidal water and the changes in the environment factors, which increase the bioavailability of heavy metals. In this review, the characteristics of distribution and the bioavailability of heavy metals in intertidal sediments are described; the migration and transformation behavior of heavy metals and its influencing factors under tidal conditions are analyzed; and the mechanisms of heavy metal’s migration and transformation in the intertidal zone are summarized. Moreover, the bioaccumulation of heavy metal by organisms and the remediation techniques are discussed. Therefore, this review systematically summarizes the states of existence, the transport mechanisms, and the fate of heavy metals in the intertidal sediment, fills in the research gap of the cycling of heavy metal in the intertidal zone, and provides a theoretical basis for the control of heavy metal pollution.

Effects of Coal Gasification Slag on the Migration of Cd2+ and Pb2+ in Soil

In recent years, coal gasification slag has been widely used as an adsorbent in many countries worldwide. To better understand remediation of soil heavy metal pollution by coal gasification slag, it is necessary to examine and analyze the influence mechanism of the adsorption characteristics of coal gasification slag on the migration of heavy metal ions in the soil. In this study, we used a soil water movement model and convection-dispersion equation and constructed a model of heavy metal migration after soil improvement by coal gasification slag; then, we evaluated and predicted the influence of heavy metal infiltration with liquid on groundwater after soil improvement. Combined with the soil column experiment, HYDRUS-1D software was used to predict the migration behavior of heavy metals in the soil. The results showed that the dispersion of the sample with coal gasification slag was smaller than that of the original soil sample, and the permeability coefficient of the soil was reduced by 59.34%; after adding coal gasification slag, the adsorption rates of Cd2+ and Pb2+ on the soil samples were higher than 95% and 99% respectively. The constructed heavy metal migration model was fitted well and predicted the migration behavior of heavy metals in the soil satisfactorily. The addition of coal gasification slag can effectively prevent the infiltration of Cd2+ and Pb2+ in the soil and can mitigate groundwater pollution. Therefore, using the adsorption characteristics of coal gasification slag to study the migration behavior of Cd2+ and Pb2+ in soil has important practical significance for soil adsorption and provides a new idea for the comprehensive utilization of coal gasification slag.

Potential Migration and Health Risks of Heavy Metals and Metalloids in Take-Out Food Containers in South Korea.

The consumption of take-out food has increased worldwide; consequently, people are increasingly being exposed to chemicals from food containers. However, research on the migration of metals from containers to food is limited, and therefore, information required to determine the health risks is lacking. Herein, the amount of transfer of nine metals and metalloids (Pb, Sb, Cd, Ge, Co, Mn, Sn, As, and Hg) from food containers to food in South Korea was assessed from take-out food containers classified into paper and plastic container groups. The sample containers were eluted over time by either warming with 4% acetic acid at 70 °C or cooling with 4% acetic acid at 100 °C /deionized water at 25 °C. It was analyzed using an inductively coupled plasma mass spectrometer and a direct mercury analyzer. The reliability of the quantitative results was verified by calculating the linearity, limit of detection, and limit of quantification. We found that the amount of metals and metalloids (Pb, Sb, Cd, and Co) eluting over time was highly significant in the plastic group. Regardless of the food simulant and elution time, the amount of Sb transferred from the food containers to food was substantially higher in the plastic (average concentration: 0.488-1.194 μg/L) than in the paper group (average concentration: 0.001-0.03 μg/L). Fortunately, all food containers were distributed at levels safe for human health (hazard index: 0.000-64.756%). However, caution is needed when warm food is added to food containers. Overall, our results provide baseline data for the management and use of take-out containers.

Kinetics release of heavy metal Cu from sediment affected by the mimic vegetation under unidirectional flows and regular waves

The process of heavy metal contamination in wetlands is becoming increasingly prevalent due to rapid urbanization. Heavy metals deposited in the sediment can be re-released into the water under disturbances, leading to significant impacts on the water environment and ecosystem. The release of heavy metals in wetlands is a complex phenomenon involving the intricate interplay of physicochemical and biological mechanisms. To gain insights into the adsorption-desorption processes of Cu under the influence of hydro-sediment dynamics, indoor experiments were conducted in this study, considering the presence of mimic vegetation at a short-term scale. The biological processes were not explicitly considered in these experiments. To analyze the kinetic processes of heavy metal migration at the water-sediment interface influenced by mimic vegetation under different hydrodynamic conditions, several equations were utilized, including the pseudo-second-order kinetic equation, double constant rate equation, Elovich equation, and parabolic diffusion equation. The pseudo-second-order kinetic equation can best simulate the Cu release process, with R2 ranging from 0.98 to 0.99. In order to enhance the accuracy of our predictions, the stem-Reynolds number (Red) is introduced into the original pseudo-second-order kinetic equation to account for the influence of mimic vegetation on the release of heavy metals. As a result of this improvement, the release processes of Cu were better predicted using the updated equations. The error between the improved equation and the actual measured value is reduced to less than 10 %. These improved methods are suitable for both unidirectional flow and wave conditions affected by mimic vegetation, and they offer vital parameters for numerical simulations of heavy metal transport in riverine or coastal wetlands. This research contributes to a better understanding of the complex processes governing heavy metal dynamics in wetland environments and provides valuable insights for effective environmental management and protection.

The change of coordination environments induced by vacancy defects in hematite leads to a contrasting difference between cation Pb(II) and oxyanion As(V) immobilization

Hematite is an iron oxide commonly found in terrestrial environments and plays an essential role in controlling the migration of heavy metal(loid)s in groundwater and sediments. Although defects were shown to exist both in naturally occurring and laboratory-synthesized hematite, their influences on the immobilization of heavy metal(loid)s remain poorly understood. In this study, hematite samples with tunable vacancy defect concentrations were synthesized to evaluate their adsorption capacities for the cation Pb(II) and for the oxyanion As(V). The defects in hematite were characterized using XRD, TEM-EDS mapping, position annihilation lifetime spectroscopy, and XAS. The surface charge characteristics in defective hematite were investigated using zeta potential measurements. We found that Fe vacancies were the primary defect type in the hematite structure. Batch experiments confirmed that Fe vacancies in hematite promoted As(V) adsorption, while they decreased Pb(II) adsorption. The reason for the opposite effects of Fe vacancies on Pb(II) and As(V) immobilization was investigated using DFT calculations and EXAFS analysis. The results revealed that Fe vacancies altered As–Fe coordination from a monodentate to a bidentate complex and increased the length of the Pb–Fe bond on the hematite surface, thereby leading to an increase in As(V) bonding strength, while decreasing Pb(II) adsorption affinity. In addition, the zeta potential analysis demonstrated that the presence of Fe vacancies led to an increase in the isoelectric point (IEP) of hematite samples, which therefore decreased the attraction for the cation Pb(II) and increased the attraction for the oxyanion As(V). The combination of these two effects caused by defects contributed to the contrasting difference between cation Pb(II) and oxyanion As(V) immobilization by defective hematite. Our study therefore provides new insights into the migration and fate of toxic heavy metal(loid)s controlled by iron minerals.

Spatial Distribution and Migration of Heavy Metals in Dry and Windy Area Polluted by Their Production in the North China

We explored the migration and distribution of heavy metal pollution in a dry and windy area in northern China. We collected soil, atmospheric deposition, and water samples, and measured heavy metal concentrations. Cu, Zn, As, and Pb in the 0–10 cm soil layer had a fan-shaped distribution, consistent with their atmospheric deposition fluxes. This indicates that the distribution of these heavy metals was driven by strong winds. The concentration of Cd in the river increased from 0.257 mg/L upstream to 0.460 mg/L downstream, resulting in the same distribution trends as soil near the river. Surface runoff may therefore drive Cd migration. The concentration of Pb in the river exceeded the pollution threshold, resulting in accumulation in the 5–10 cm soil layer. Atmospheric deposition fluxes were consistent with the soil distribution results, and principal component analysis showed that the contribution of surface runoff was high. This suggests that the migration of Pb and Cr is driven by both wind and surface runoff. Six heavy metals showed different migration behaviors, suggesting specific control strategies should be implemented for individual heavy metals.

In situ, high-resolution evidence for the release of heavy metals from lake sediments during ice-covered and free periods

Heavy metal dynamics at the sediment-water interface (SWI) has attracted plenty of attention due to their meticulous depiction for metal sorption-release processes. However, little is known about their concentration, migration and release characteristics underneath the ice, especially at the millimeter scale. Here we investigated dynamics of labile As, Cd, Cu, Mn, Pb and Zn by the diffusive gradients in thin-films (DGT) technique during ice-covered and ice-free periods in the Lake Xingkai basin. The concentrations of metals were relatively high at the SWI and ranged for As: 0.001~13.42 μg L−1, Cd: 0.01~0.45 μg L−1, Cu: 0.001~2.75 μg L−1, Mn: 5.31~2958.29 μg L−1, Pb: 0.06~1.43 μg L−1, and Zn: 2.92~112.96 μg L−1. Particularly, concentration of Mn was extremely higher than other studies, possibly due to diagenetic process. Labile concentrations of heavy metals in January were significantly lower than those in May, suggesting that elevated temperatures lead to the release of heavy metals from the sediment to the overlying water. Based on the Fick’s first law, the diffusive fluxes as a source of Mn (413.82-1163.25 mg·m-2·d-1) and As (3.53 -8.12 mg·m-2·d-1) indicated that heavy metals were released from sediments to the overlying water. While the diffusive fluxes as a sink of Zn (-1.80-(-2.36) mg·m-2·d-1) and Pb (-0.02-(-0.46) mg·m-2·d-1) to sediments. Redundancy Analysis (RDA) revealed that the main factors influencing the heavy metal migration were dissolved oxygen (45.6% of total explanation, P=0.01) in January, and water temperature (52.9%, P=0.006) in May. This study extends theoretical scope for understanding metal migration and release process, and provides valuable suggestions for lake management during the freezing period.

Migration of total petroleum hydrocarbon and heavy metal contaminants in the soil-groundwater interface of a petrochemical site using machine learning: impacts of convection and diffusion.

Convection and diffusion are key pathways for the migration of total petroleum hydrocarbons (TPH) and heavy metals (HMs) from soil to groundwater. However, the extent of their influence on pollutant migration, as well as the nonlinear relationships between these processes and pollutants, remains unclear. This study investigates the spatial distribution of TPH and HMs at a petrochemical site with complex hydrogeological conditions in southwestern China. In addition, machine learning (ML) was used to assess the effects of convection and diffusion on pollutant migration at the soil-groundwater interface. The analysis identifies and reveals TPH, Co, and Ni as the primary pollutants, with soil concentrations reaching 47.427, 7.024, and 4.766 times their respective screening values. Among various ML models, Random Forest (RF) was identified as the most effective, based on R 2, and RMSE performance metrics. The RF model demonstrates that the concentrations of TPH and As are closely related to soil depth. Furthermore, importance indices calculated by RF indicate that the significance of convection and diffusion varies across different soil-groundwater systems. Specifically, at the soil-perched water interface, convection plays a more significant role than diffusion in influencing the migration of TPH and As. However, at the soil-pore water interface, diffusion more significantly influences the migration of all pollutants compared to convection. Additionally, a threshold or saturation effect was observed for the impact of the convection factor on pollutant concentrations in groundwater. These findings highlight the distinct roles of convection and diffusion across various water interfaces, providing new insights into the mechanisms governing contaminant migration and fate.

Research Results of Municipal Sewage Sludge Applied for Building Material Production

The study presents the experimental results on the use of ash obtained as a result of incineration of municipal sewage sludge from the water utility of Izhevsk, Udmurt Republic, for construction material production. Research methods are given and the results of strength tests of building material samples are given. The impact of the manufactured samples of construction materials on the ecology of the surrounding space and human health is assessed. To achieve the set objectives of the research laboratory experiment and determination of indicators of investigated values of sludge, ash and water extracts with the use of devices and measuring instruments are used. On the basis of the research laboratories of Kalashnikov Izhevsk State Technical University and MUE “IzhVodokanal” of the Udmurt Republic experimental studies on incineration of sewage sludge and the use of the resulting ash as a substituting or modifying component of the construction mixture in the manufacture of experimental samples of ceramics, cement-sand mortar and concrete were carried out. Methodology of manufacturing and algorithm of ceramic (fired) and cement-based (nonfired) testing specimens are presented. Measuring means for determination of gamma-radiation intensity indices of ash, cement and their influence on human health are used. The algorithm of experimental research, applied energy-efficient techniques used in the experiment and analysis of the obtained experimental results are presented. The analysis of experimental research results of ceramic and cement-based products, as well as the analysis of radiation safety, migration of heavy metals is presented. The energy-efficient methodology of sewage sludge utilization and further ways of applying ash as an environmental and resource-saving component used in manufacturing of experimental building materials are considered.