Mobility Of Metals In Soils Research Articles

Effectiveness of constructed wetland technology-treated industrial wastewater on the spinach (Spinacia oleracea) health risks and biochar efficiency.

In peri-urban areas, use of industrial wastewater for irrigation is a common practice. Industrial wastewater contains cadmium, chromium, lead, nickel, and other elements that deteriorate food quality and affect human health. Biochar has been proven to remediate heavy metal contaminated soil by reducing their mobility and bioavailability. A pot experiment was conducted to evaluate the efficiency of different levels of biochar on spinach growth with low heavy metal concentration and to minimize associated health issues. The experiment lasted two months and the treatments: Control (tap water), untreated and treated industrial wastewater and both in combination with biochar (0.5% and 1%) were applied in completely randomized design. Findings suggested that treated industrial wastewater with 1% biochar resulted in maximum plant height, shoot weight, chlorophyll contents (SPAD value), photosynthetic and transpiration rate. Biochar significantly reduced heavy metal mobility in soil due to its porous structure, high pH, higher CEC, and variety of surface functional groups. The cumulative hazard index (HI), hazard quotient, cancer risk, and total cancer risk (TCR) were calculated using method provided by US-EPA for each metal. All treatments had HI values of < 1, however applying 1% biochar significantly reduced the HI values to 2.00E-01 and 2.88E-01 in adults and children, respectively. TCR for all treatments was < 1, while treated industrial wastewater and biochar (1%) has significantly reduced to 1.55E-02 and 1.91E-03 for adults and children, respectively. Thus, it was determined that irrigation with industrial effluents caused toxicity in vegetables, which had a negative impact on human health. Biochar effectively mitigated metal toxicity in both soil and spinach plants that resulted in reduced health/cancer risk.

Photoaged tire wear particles hinder the transport of Pb(II) in urban soils under acid rain: Experimental and numerical investigations

Rapid urbanization brought lots of serious environmental contamination, including the accumulation of heavy metals, acid rain, and the emission of tire wear particles (TWPs), with detrimental effects for terrestrial ecosystems. Nevertheless, how naturally aged TWPs affect the mobilization of heavy metals in soils under acid rain is still unclear. Here, we investigate the adsorption and transport mechanisms of Pb(II) co-existing with acid rainwater in soil-TWP mixtures via batch experiments, column experiments and modeling. Results showed that photoaged TWP significantly prolonged the Pb(II) adsorption equilibrium time (1 to 16 h) and enhanced the Pb(II) adsorption capacity of soils. Soil column profiles confirmed that TWP effectively boosted the initial accumulation of lead in the topsoil and thus impeded the downward transport of lead. The retardation factor (R) estimated by the linear two-site sorption model (TSM) fitting the Pb(II) breakthrough curves gradually increased from 1.098 to 16.38 in soils with TWP (0–10 %). Comparative results of linear or nonlinear TSM suggested nonlinear sorption replacing linear sorption as the main Pb(II) sorption mechanism under 1 % and 10 % TWP. This research provides significant insights into the implications of TWP on the Pb(II) retention behaviors and highlights the severer potential remobilization risks of Pb(II) in urban soils under different acid rain environments.

Geochemical Signature and Risk Assessment of Potential Toxic Elements in Intensively Cultivated Soils of South-West Punjab, India

Soil contamination with potentially toxic elements (PTEs) in the Malwa region belt of Punjab, India, can be a serious concern as a result of intensive agricultural practices and overuse of agrochemicals. The main objectives of the present study were to evaluate the spatial distribution, geochemical signature, and contamination level/health risk of PTEs in 76 soil samples (0–10 cm) collected from the three districts viz. Muktar, Faridkot, and Moga of Punjab, India. The result shows that PTEs concentrations vary widely in the region, with Fe and Mn distribution patterns being mostly coherent with each other. When compared to the Indian natural soil background values, the average concentration of Pb and Zn were higher than the limit, only Pb exceeded the average values of the world background and upper continental crust (UCC). Spatial autocorrelation plotted with a local indicator of spatial association (LISA) in GeoDa software version 1.18 was used to identify hotspots. A positive spatial autocorrelation (&gt;0.2) was indicated with Moran’s I values for Pb, V, Mn, Cu, and Cr, being highest for Pb. A principal component analysis (PCA) identified the major geo-chemical patterns of Fe-Al-V-Cr and TOC-Mn-Zn-HCO3−, which were positively loaded on PC1. This indicates that Fe/Al-oxyhydroxides and organic matter play a dominant role in controlling metal mobility in soils. This can be further substantiated with the Spearman’s rank correlation values. The contamination factor (CF) indicates that only Pb and Zn (15.7% and 3.9% samples, respectively) were under high risk. This could be due to the excessive application of chemical fertilizers. The large range of degree of contamination (Cdeg) values suggests that there are variations in the degree of soil pollution due to PTEs. A little over 3.9% of samples had significant contamination, compared to 72.3% of samples with low contamination and 23.6% of samples with moderate contamination. Human non-carcinogenic and carcinogenic risk levels were investigated. The hazard index (HI) values for adult ranged from 0.00 to 0.2, and values for children ranged from 0.009 to 1.2. These findings suggest that both children and adults are not at potential risk, except in a few locations. Overall, the results of this study provide the current baseline status of toxic elements in agricultural soil. This would be helpful for developing strategies for sustainable management of the soil resources in the region, as well as for future monitoring programs of the soil quality in the Malwa region as a whole, to track any changes in the contamination levels over time.

Application of microbially induced calcium carbonate precipitation (MICP) process in concrete self-healing and environmental restoration to facilitate carbon neutrality: a critical review.

Soil contamination, land desertification and concrete cracking can have significant adverse impacts on sustainable human economic and societal development. Cost-effective and environmentally friendly approaches are recommended to resolve these issues. Microbially induced carbonate precipitation (MICP) is an innovative, attractive and cost-effective in situ biotechnology with high potential for remediation of polluted or desertified soils/lands and cracked concrete and has attracted widespread attention in recent years. Accordingly, the principles of MICP technology and its applications in the remediation of heavy metal-contaminated and desertified soils and self-healing of concrete were reviewed in this study. The production of carbonate mineral precipitates during the MICP process can effectively reduce the mobility of heavy metals in soils, improve the cohesion of dispersed sands and realize self-healing of cracks in concrete. Moreover, CO2 can be fixed during MICP, which can facilitate carbon neutrality and contribute to global warming mitigation. Overall, MICP technology exhibits great promise in environmental restoration and construction engineering applications, despite some challenges remaining in its large-scale implementation, such as the substantial impacts of fluctuating environmental factors on microbial activity and MICP efficacy. Several methods, such as the use of natural materials or wastes as nutrient and calcium sources and isolation of bacterial strains with strong resistance to harsh environmental conditions, are employed to improve the remediation performance of MICP. However, more studies on the efficiency enhancement, mechanism exploration and field-scale applications of MICP are needed.

Temporal changes in the mobility of As, Pb, Zn, and Cu due to differences in biochar stability caused by lignin content

Understanding biochar aging is a critical factor in predicting its long-term effects when added to soil. This study explores the complex links between lignin content in biochar feedstock and biochar stability during accelerated aging, including its influence on heavy metal mobility in soil. In this study, nine types of biochar based on fir (F), pine (P), and oak (O) sawdust were produced at 400 °C, and lignin was extracted from them using ammonia after 0, 3, and 7 days (named as 0FB, 3FB, 7FB, 0PB, 3PB, 7PB, 0OB, 3OB, and 7OB). Subsequently, each biochar was subjected to 25 cycles of wet-dry (WD) and freeze–thaw (FT) aging. The aged low-lignin biochars (7FB, 7 PB, and 7OB) released more dissolved organic matter (DOM) and contained more oxygen-containing surface groups on their surfaces than the high-lignin biochars (0FB, 0PB, and 0OB). The low-lignin biochars with high DOM leaching released 37–85 % more anionic arsenic (As) from biochar-amended soil after 25 cycles of aging than the high-lignin biochars. The stabilities of lead (Pb), zinc (Zn), and copper (Cu) were increased due to strong binding to surface functional groups on the low-lignin biochar. The acid-soluble fractions of Pb, Zn, and Cu were converted to organic-bound fractions as biochar aging progressed, with the degree of transformation being inversely proportional to the lignin content of biochar. This research highlights the crucial role of lignin in shaping biochar stability, and reveals how biochar stability impacts soil heavy metals speciation, opening new avenues for effective biochar-based environmental solutions and the promotion of soil health.

Impact of thermal soil treatment on heavy metal mobility in the context of waste management.

Thermal soil treatment is a well-established remediation method to remove organic contaminants from soils in waste management. The co-contamination with heavy metals raises the question if thermal soil treatment affects heavy metal mobility in soils. In this study, four contaminated soils and a reference sample were subjected to thermal treatment at 105°C, 300°C and 500°C for 7 day. Thermogravimetry and differential scanning calorimetry were used to understand the reactions, and resulting gases were identified by Fourier-transformed infrared spectroscopy. Treated and untreated samples were characterised by X-ray diffraction (XRD) and electron microprobe analysis and subjected to pH-dependent leaching tests, untreated samples additionally by X-ray-fluorescence (XRF) and inductively coupled plasma mass spectroscopy (ICP-MS). Leachates were analysed using ICP-MS and ion chromatography. Maximum available concentrations were used for hydrogeochemical modelling using LeachXS/Orchestra to predict leaching control mechanisms. Leaching experiments show that thermal treatment tends to decrease the mobility at alkaline pH of Pb, Zn, Cd, As and Cu, but to increase the mobility of Cr. In the acidic to neutral pH range, no clear trend is visible. Hydrogeochemical modelling suggests that adsorption processes play a key role in controlling leaching. It is suggested that the formation of minerals with a more negatively charged surface during thermal treatment are one reason why cations such as Pb2+, Zn2+, Cd2+ and Cu2+ are less mobile after treatment. Future research should focus on a more comprehensive mineralogical investigation of a larger number of samples, using higher resolution techniques such as nanoscale secondary ion mass spectrometry to identify surface phases formed during thermal treatment and/or leaching.

Effect of multiwall carbon nanotubes and surfactants characteristics on immobilization of heavy metals in contaminated soils

Soil is a vital resource to humans and soil health is a concern of modern societies. One of the problems is the existence of heavy metals (HMs) pollution, which can affect food, water sources and biodiversity. This experimental work studies the effect of multiwall carbon nanotubes (MWCNTs) and surfactants characteristics on HMs immobilization in a contaminated soil. The testing program comprises the characterization of the MWCNTs and surfactants, followed by two distinct adsorption tests: suspension tests designed to supply preliminary information regarding the adsorption capacity of soil particles towards the different HMs, and percolation tests to evaluate the HMs immobilization in conditions mimicking a real in-situ scenario. The different HMs exhibit different affinities order to the soil studied: Pb > Cu > Ni > Zn. Results indicated that the inherent soil particles can immobilize significant quantities of HMs (especially Pb and Cu) due to their fine size and the existence of a substantial amount of organic matter content in the soil matrix. Molecular weight and charge density of the surfactant are characteristics with an impact on the MWCNTs dispersion and also on the adsorption capacity of the different HMs, namely in the case of Ni2+ and even in the case of Zn2+ possessing lower electronegativity and higher mobility. The findings of the study allow concluding that MWCNTs possess the potential to reduce the mobility of heavy metals in soil, even when employed at very low concentration (0.01% w/w), which is an important feature considering their cost.

Evaluation of Total Concentrations and Extractable Fractionations of Cd, Co and Ni in Soils from Dumpsites across Rivers State, Nigeria

The mobility of trace metals in soils strongly depends on the forms in which the metals are bound to major soil components. This study aims to determine the total concentrations and extractable fractionations of Cd, Co and Ni in soil samples collected from dumpsites across Rivers State, Nigeria. Solar Thermo Elemental Atomic Absorption Spectrometer model (SG 71906) was used after mixed acid digestion (HCl: HNO3 in a ratio of 3:1 v/v) and modified BCR sequential extraction procedure. The concentration levels of Cd, Co and Ni in all the samples varied, with mean values of 13.48 11.85, 25.29 17.62 and 20.52 15.66 mg/kg, respectively. Using the Community Bureau of Reference (BCR) sequential extraction procedure, the elements recoveries were within the acceptable range varying between 92.10% and 98.33% for Co and Cd, respectively. Data from the BCR extraction procedure revealed that the majority of Cd fraction was associated with residual fraction, Co fraction bound to the exchangeable fraction, while Ni was found to be associated with oxidisable fraction. These results suggest that the trace elements in the soil were highly mobile and bioavailable for plant uptake. Results from the findings particularly correlation analysis is indicative of the fact that some of the contaminants may have anthropogenic and natural origin. Hence, these contaminants could pose significant threat to human health and the environment.

Application of Diffusive Gradients in Thin-films (DGT) for assessing the heavy metals mobility in soil and prediction of their transfer to Russula virescens

Although edible mushrooms are considered a source of many beneficial nutrients for human, they can also represent a risk to health due to their capacity to accumulate heavy metals. In this study, the total dissolved in soil solution and labile concentrations of heavy metals (Cd, Pb, Cu, Zn, Co, Cr, Mn, Ni, and Fe) in soil were measured and correlated with their concentrations accumulated in Russula virescens wild mushrooms. The diffusive gradient in thin films (DGT) technique was used to measure the labile metals content in the soil (CDGT), and corroborated with the metals concentrations in soil solution (Csoln) was used to calculate an R-value, which can estimate the metals resupply from soil solid phase when they are uptake by mushroom. The DGT-labile metal concentrations decreased in the order Mn > Fe > Zn > Cu > Co > Ni > Cd ≅ Pb > Cr. The R-values, calculated as the ratio between CDGT and Csoln decreased in the order: Cd (0.50) > Zn (0.37) > Pb (0.33) > Cu (0.24) ≅ Ni (0.24) ≅ Co (0.23) > Mn (0.16) > Fe (0.12) > Cr (0.04). For the first time, we compared the R-values with the bioaccumulation factors (BAFs) in mushrooms, and it was observed that, a similar increasing trend of BAFs with the R-values exists, thus the capacity of the soil solid phase to fast re-supply metals to soil solution increases BAFs. Although the soil samples were not contaminated with heavy metals above the legislative limits, the concentrations of heavy metals accumulated in mushrooms were high enough to pose risks for humans, mainly for children, due to their Cu content.

High-resolution imaging of O2 dynamics and metal solubilization in the rhizosphere of the hyperaccumulator Leersia hexandra Swartz

The mobilization of trace metals in the rhizosphere can be affected by the redox potential, which is closely related to the O2 dynamics. This study examined the distributions of O2 and trace metals in the rhizosphere of the subaquatic hyperaccumulator Leersia hexandra Swartz under chromium (Cr) stress using planar optodes and the diffusive gradients in thin films technique coupled with laser ablation inductively coupled plasma mass spectrometry. The O2 concentrations and oxidized areas in the rhizosphere significantly increased with increases in the light intensity, air humidity, and atmospheric CO2 concentrations (p < 0.05). The O2 concentration first increased with increasing ambient temperatures, then decreased when the temperature increased from 25 to 32 ℃. The O2 concentration in the rhizosphere was significantly decreased under Cr stress (p < 0.05), with a prolonged response time to the altered ambient temperature. Cr stress led to decreased mobilities of As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sb, V, W, and Zn in the rhizosphere, which were negatively correlated with the concentrations of O2. These results provide new insights into the role of changes in the O2 concentration induced by the roots of hyperaccumulator plants in controlling the mobility of trace metals in soils.

Is the co-application of self-produced compost and natural zeolite interesting to reduce environmental and toxicological availability in metal-contaminated kitchen garden soils?

Composting can turn organic waste into a valuable soil amendment that can improve physical, chemical, and biological soil quality. Compost amendments can also contribute to the remediation of areas anthropogenically degraded by metals. However, it is well known that compost, particularly self-produced compost, can show enrichment in metals. An experimental study was conducted to examine the short- and long-term distribution and the mobility of metals in soils amended with a self-produced compost when it was added alone or in combination with different doses of a natural zeolite to soil. The aim was also to study the interest of managing moderately metal-contaminated kitchen garden soils by assessing the chemical extractability, phytoavailability, and oral bioaccessibility of metals. When zeolite was added to compost alone, it had the tendency to better reduce extractability of Cd and Zn at 25%, and those of Pb at 15%. When the self-produced compost alone or in co-application with zeolite at these doses was applied to soils, the results showed (1) a decrease of NH4NO3-extractable Zn; (2) a reduction of Pb environmental availability, but not Pb bioaccessibility, and (3) an increase of ryegrass biomass. Nevertheless, the risk posed by the self-produced compost was minimal when applied at the proper rate (0.6%w/w). In the selected experimental conditions, the study recommends that self-produced compost be mixed with 15% zeolite to maximize vegetal biomass and minimize environmental risk. The question of sustainability of the results with repeated compost addition is also raised.

Metal Fractionation and Leaching in Soils from a Gold Mining Area in the Equatorial Rainforest Zone

In this article, a modified BCR procedure and a column leaching test were used to examine the bioavailability and mobility of heavy metals in soils collected from a gold mining area in Ghana. The results for the fractionation of Cd, Cr, Fe, and Mn indicated that high percentages of metals were found in the residual fraction. This implies that the concentrations of metals in the soil are stable under normal environmental conditions. The bioavailability of metals in the soils declined in the following order: Mn (92.4%) &gt; Cd (64.6%) &gt; Cr (46.4%) &gt; Fe (39%). However, the concentrations of labile metals may pose no risk to the environment. In the column test, different rainwater conditions (i.e., natural rainwater and acidified rainwater) were used to imitate the leaching potential of the metals in the actual field. The pH of the soil primarily controlled metal migration into deeper layers. Cumulative metal concentrations in the leachates showed that Fe, Mn, and Cd were high in the tested soils but present at low concentrations, except for Cd. Cadmium showed a higher concentration than the WHO guideline for drinking water, and its seepage into deeper layers may affect the quality of groundwater.

Comprehensive study of electrokinetic-assisted phytoextraction of metals from mine tailings by applying direct and alternate current

Electrokinetic-assisted phytoextraction (EKPH) involves the use of electric current to improve the mobilization of metals in soils and, therefore, their removal efficiency. It emerges as an interesting sustainable technology for the rehabilitation of abandoned mining areas. The goal of this research was to conduct a comprehensive study of this technique applied to real mine tailings from an abandoned Pb/Zn mine by using ryegrass as plant species and two types of electric current: direct with polarity reversal (DC-PR) and alternate (AC). The EKPH tests were conducted in specially designed plastic containers that allowed recording the main parameters of the electrokinetic process and sampling the different matrices studied, i.e. water, soil and plants. This intensive sampling program allowed detailed monitoring of the metal mobilization processes for the different treatments applied. The changes caused in metal mobility and physicochemical parameters of the tailings due to the application of electric current were reflected to a greater extent in the water samples than in solid ones. Accumulation of Pb, Zn, Cd and Cu in ryegrass tissues increased significantly by 41%, 17%, 34% and 32% when applying 1 V cm−1 of AC current, with respect to the results of phytoextraction without electric current. The application of DC-PR current did not lead, in general, to statistically significant increases in the plant metal uptake. These findings were adequately correlated with the changes found in the metal concentrations of soil pore water and, to a lesser extent, with those observed from the BCR sequential extraction applied to tailings samples.

Composted sewage sludge utilization in phytostabilization of heavy metals contaminated soils

In phytostabilization, heavy metal-tolerant plants (e.g.,grasses) can be used to reduce the mobility of heavy metals in soils. The most important step in phytostabilization is the selection of the suitable plant species, in which growth and development can be supported by soil amendments. Sewage sludge compost could be a suitable additive, which provides nutrients for the plant species used for phytostabilization and contributes to an alternative solution for sewage sludge utilization. The aim of the study was to examine the potential of sewage sludge compost in phytostabilization for heavy metal contaminated matrices: identify the optimal ratio of sewage sludge compost to decrease phytotoxicity of the matrices, and assessment of feasible plant species for phytostabilization based on its bioaccumulation properties. In this research, perennial ryegrass (Lolium perenne), broad-leaved sorrel sorrel (Rumex acetosa), lettuce (Lactuca sativa) and cabbage (Brassica oleracea var. capitata) were used for phytotoxicity experiments as well as for testing sewage sludge compost amended phytostabilization of polluted flotation sludge and mine tailings. Sewage sludge compost increased the pH and electric conductivity of the matrices. High salt content and low acidity, altogether with heavy metals caused harmful physiological effects on plant species grown without any compost addition. In the root development test, as in the germination test, the application of 5% sewage sludge compost proved to be optimal. The lower translocation factors of broad-leaved sorrel and perennial ryegrass showed a higher rate of heavy metal accumulation in the roots. Perennial ryegrass, cabbage, and lettuce plant species reached their maximum biomass by adding 5% of sewage sludge compost. Based on the bioaccumulation, translocation and biomass properties, application of perennial ryegrass is recommended for phytostabilization of heavy metal contaminated sites. Furthermore, composted sewage sludge also had a significant effect on the reduction of heavy metal uptake by cabbage and lettuce, which highlights their role as indicator plants in ecotoxicological measurements.

Heavy Metal Migration in Soil-Plant System in Conditions of Urban Environmental Pollution

This study is devoted to heavy metal soil migration to coltsfoot in urban pollution of Tyumen city. Soil and plant samples were collected in the summer of 2017 to 2020 at the control site, highway, engine-building, oil refinery, battery manufacturing, and metallurgical plants. Heavy metals (Cu, Zn, Fe, Mn, Pb, Cd, Ni, Co, and Cr) mobile and acid-soluble forms in soils, and metals concentration in plants were analyzed by atomic absorption and atomic emission spectroscopy. Metals concentration in soils of urban area exceeded the control by 1.1 to 20 times. Relative accumulation of metals decreased in the order: Pb &gt; Cu &gt; Zn &gt; Ni &gt; Cr &gt; Fe &gt; Co &gt; Mn &gt; Cd. Heavy metals mobility in soils decreased in the order: Cd &gt; Mn &gt; Pb &gt; Zn &gt; Ni = Cu &gt; Co &gt; Cr &gt; Fe. Coltsfoot metal accumulation changed in the order: Fe &gt; Zn = Mn &gt; Pb &gt; Cu &gt; Cr &gt; Co &gt; Ni &gt; Cd. The highest contamination for most of the metals was at the metallurgical plant, while Ni and Co concentrations were maximum at the oil refinery. Content of Cu, Zn, Fe, Cd, Ni, and Co in coltsfoot correlated with a concentration in soils. Bioconcentration factor showed the following metal bioavailability: Cu &gt; Zn &gt; Cd &gt; Pb &gt; Ni &gt; Mn &gt; Cr &gt; Co &gt; Fe. Heavy metal accumulation in coltsfoot should be taken into account during sanitary control of herb drugs based on this plant.

ИСПОЛЬЗОВАНИЕ ТОРФА В КАЧЕСТВЕ СОРБЕНТА ТЯЖЕЛЫХ МЕТАЛЛОВ

Territories of accumulated environmental damage have a negative impact on all components of the environment, lead to deterioration of the sanitary and epidemiological state in the regions. One of the main pollutants of the ecosystem are heavy metals, the sources of which are industrial enterprises. Currently, technologies aimed at limiting the mobility of heavy metals in soils and technogenic soils are being developed and implemented. The sorbent-oriented method is the most promising. It involves the use of natural materials to solve environmental problems. The use of local types of minerals for land reclamation is a priority in the Russian Federation. Peat is a universal natural material that is used in many sectors of the national economy. It can be used as a sorbent-meliorant for the adsorption of heavy metal ions during reclamation work on disturbed lands and as an organic fertilizer to improve physico-chemical properties and increase soil fertility. The article presents the results of studies of sorption of a number of heavy metals (Cu2+, Cd2+, Pb2+, Cr3+, Cr6+) by modified peat. Studies have shown that peat-based sorbent meliorant can be used in the process of developing environmental measures in terms of ecological rehabilitation of disturbed native ecosystems.

Process, influencing factors, and simulation of the lateral transport of heavy metals in surface runoff in a mining area driven by rainfall: A review.

The lateral transport of heavy metals can expand the scope of original contamination, and an accurate prediction of heavy metal migration is necessary to control heavy metal transport. However, previous studies have mainly focused on the migration of soil pollutants in the runoff-soil-groundwater system, whereas research on the lateral migration of heavy metals in surface soil driven by rainfall is relatively scarce. Therefore, in this study we analyzed the horizontal migration of water-soluble heavy metals with surface runoff and non-water-soluble heavy metals with sediment particles, investigated the main factors affecting the processes of runoff and sediment transport and the main factors affecting the mobility of heavy metals in soils, summarized the existing methods for the simulation of heavy metal transportation. The construction of a lateral migration model based on the migration mechanism of soil heavy metals, the hydrological model, and the application of the lateral migration model should be the focus of future research. This study provides a theoretical basis for establishing a model of the lateral migration of soil heavy metals and is of great significance for the prevention and control of the risks related to the lateral migration of soil heavy metals.

Salinization and heavy metal cadmium impair growth but have contrasting effects on defensive colony formation of Scenedesmus obliquus

Driven by anthropogenic activities, freshwater salinization has become an emerging global environmental issue. Recent studies indicate that salinization increases the mobility of heavy metals in soil and causes higher flux into surface waterbodies. The present study assessed the combined effects of salinization (0, 3, 6 PSU) and the heavy metal Cd2+ (0, 0.2, 0.4 mg L−1) on the anti-grazing colony formation and population growth of Scenedesmus obliquus, a common freshwater alga. The results showed that the increase in salinity promoted colony formation of S. obliquus with or without the presence of grazing cues and, in contrast, Cd2+ contamination depressed the defensive colony formation of S. obliquus to Daphnia filtrate. The increase in both salinity and Cd2+ concentration depressed the population growth of S. obliquus, including impaired photosynthesis and a decreased population growth rate. Salinization moderated the negative effects of Cd2+ on defensive colony formation of S. obliquus, suggesting increased absorption of Cd2+ ions by a thicker outer layer of the algal cell wall under saltier conditions. As a result, larger defensive colonies of S. obliquus under freshwater salinization may cause higher bioaccumulation of heavy metals by algal cells and heavier influence on zooplankton. This study provides evidence that freshwater salinization could interfere with plankton interactions by affecting algal defense and growth, which may lead to bottom-up cascading effects on freshwater food webs.

Influence of Anthropogenic Pollution on Mobility of Heavy Metals in Soils of Low-Industrial Cities in the Amur Region

Influence of Anthropogenic Pollution on Mobility of Heavy Metals in Soils of Low-Industrial Cities in the Amur Region

Risk Analysis of Heavy Metals Migration from Sewage Sludge of Wastewater Treatment Plants.

More and more attention in sewage sludge management is being devoted to its environmental utilization. This approach is justified both from economic and environmental points of view. However, as with any method, there are certain possibilities and limitations. The goal of the natural utilization of sewage sludge is to recover the valuable agronomic properties and fertilizing potential of the sludge. The main aspect limiting the possibility of using sludge as a fertilizer is the heavy metal content. In this paper, an analysis of the risk of environmental contamination in the case of application of sewage sludge with different forms of sludge treatment was carried out. Risk indices such as Igeo and PERI, based on the comparison of total metal content in sludge and soil, as well as RAC and ERD indices, which take into account the mobility of metals in soil, were calculated. It was shown that high levels of potential risk and geoaccumulation indicators do not necessarily disqualify the use of sewage sludge, the key aspect is the form of mobility in which the heavy metals are found in the sludge, and this should be the only aspect taken into account for the possibility of their environmental use.