Release Of Heavy Metals Research Articles

UV–vis spectroscopic method for detection and removal of heavy metal ions in water using Ag doped ZnO nanoparticles

The primary source of heavy metal discharge into the water is human activity and urbanization near water bodies. Contamination of drinking water sources with heavy metals has a harmful impact on the environment and human health. The most commonly used heavy metals are Zinc (Zn), Copper (Cu), Nickel (Ni), Lead (Pb), Cadmium (Cd), Chromium (Cr), Arsenic (As), Mercury (Hg), etc. The heavy metal ions are easily absorbed by living things via water and spread throughout the food chain, posing a threat to humans, plants, and animals (Zhang et al., 2018; Lu et al., 2019; Ma et al., 2020; Gao et al., 2018; Wen et al., 2018; Saranya et al., 2021). Colorimetric sensing is a simple and cost-effective method for the detection of heavy metal ions. Moreover, the results can be analysed with naked eye. In this work, Ag doped ZnO nanoparticles synthesized via co-precipitation method are used for the colorimetric detection of heavy metal ions. The nanoparticles are characterized for their morphology, structural, and chemical analysis using XRD, SEM, EDS, and XPS techniques. The synthesized nanoparticles are used for the colorimetric detection of heavy metal ions. The heavy metal ions such as Ni2+, Cu2+, Cr3+, Cr6+, Fe2+, and Fe3+ are successfully detected and the color change is visible from the naked eye. The minimum concentration detected is found to be 100 μM. The results are analysed via UV–vis spectroscopy. In addition to detection, the nanoparticles are further used as catalyst during the degradation of above detected heavy metal ions using NaBH4. All the heavy metal ions are degraded with in the duration of 30 min. Thus, the Ag doped ZnO nanoparticles successfully detected the heavy metal ions in aqueous solution and also acted as a catalyst during their degradation.

The behavior of heavy metal release from sulfide waste rock under microbial action and different environmental factors.

The dissolution of heavy metals from the waste rock is controlled by many factors. Herein, we investigated the release behavior of iron (Fe), chromium (Cr), copper (Cu), and zinc (Zn) from sulfide waste rock under the actions of microorganisms and different environmental factors (solution pH value, particle size of waste rock, temperature, Fe3+ concentration). The release quantity of heavy metals was negatively correlated with pH and particle size and positively correlated with ambient temperature and Fe3+ concentration. Under the experimental conditions of pH value of 3.0, temperature of 35°C, and waste stone particle size of less than 0.075 mm,, the release quantity of Fe, Cr, Cu, and Zn reached 3680, 18.32, 132.20, 26.60 mg·kg-1 after 20 days of leaching, respectively. Rising the temperature to 45 °C, Fe, Cr, Cu, and Zn release quantities increased to 89.30, 5.81, 105.08, and 28.00 mg·kg-1. Six hundred milligrams per liter Fe3+ increased the release of heavy metals considerably (2.63-65.48 folds). The presence of microorganisms can significantly facilitate the release of heavy metals. Compared to the control group, the release quantities of Fe, Cr, Cu, and Zn increased 4.29, 3.17, 1.54, and 2.39 times, respectively. In addition, the waste rock under microbial action was more seriously corroded than that under chemical factors. The release behavior of these four heavy metals was consistent with the interfacial chemical reaction control model, indicating that the reactions mainly occurred on the surface of the waste rock. This study provides an essential reference for the study of heavy metal leaching behavior.

Characteristics of heavy metal migration in farmland

Compared with water and air pollution, soil pollution is highly concealed, has poor self-purification ability, and poses high risks associated with accumulation. Characteristics of heavy metal migration directly affect the quality of the environment, and comparative studies utilizing column leaching and natural leaching experiments have rarely been performed. In this study, we used farmland soil samples from Xiba Town of the Wutongqiao District to determine the differences in leaching characteristics between column leaching and natural leaching tests. The results indicated that the heavy metals were released in two stages, a rapid release followed by a slow release stage. The cumulative amount released during the second stage exhibited regular fluctuations, while the heavy metal release rate was consistent with the heavy metal adsorption properties of the soil. In addition, the release and accumulation of heavy metals in the soil were influenced by many factors that may interact with each other, which could lead to low correlations between the cumulative heavy metals released during the column leaching and natural leaching tests. Simulating natural heavy metal migration trends using the column leaching test was effective to some extent, but there were significant differences between the accumulation sites and accumulated amounts. This study provides a theoretical basis for improving the remediation of soils contaminated by heavy metals.

Potential removal capacity and secondary pollution risk evaluation of heavy metals in Gracilaria lemaneiformis from a typical seaweed farming base

Seaweeds are significant primary producers in marine ecosystems and accumulate heavy metals from the environment during growth. However, seaweed litter is produced during the growth and harvest process and has become an important bottleneck that restricts the sustainable development of the seaweed cultivation industry. In this study, we investigated the risk assessment and potential removal of heavy metals in the Gracilaria lemaneiformis cultivation zone in a typical seaweed farming base and evaluated the secondary pollution risk of heavy metals in G. lemaneiformis litter. The results indicated that G. lemaneiformis was a good candidate for the removal and active absorption of heavy metals. A total of 60 thousand tons of harvestable G. lemaneiformis was estimated to remove 242.5 kg copper, 34.5 kg cadmium, 74 kg lead, and 2134.5 kg zinc from a typical seaweed farming base in 2018. Furthermore, the G. lemaneiformis did not pose a health risk to consumers. Variations in the heavy metal accumulation index between dead and fresh G. lemaneiformis litter differed significantly and provided evidence that metals could be either imported or exported from litter to the environment. It is suggested that G. lemaneiformis litter had a potential function in simultaneous heavy metal accumulation and release, and the function of metal accumulation was more effective during growth and decay. The results of this study contribute to the knowledge of heavy metal pollution status and risk assessment in the environment and in G. lemaneiformis, underscoring the strong capacity of heavy metal accumulation in G. lemaneiformis from the environment and the potential heavy metal removal by G. lemaneiformis cultivation and its utilization in a typical seaweed farming base.

Risk Assessment of Heavy Metal in Soil Content and Portable Water: A Review of the Literature

Extant studies have revealed that water and soil pollution are among the major global challenges that society must address in the 21st century aiming to improve water quality and reduce human and ecosystem health impacts. Industrialization, climate change, and expansion of urban areas produce a variety of water and soil contamination. In this study, the authors discussed some of the relevant findings in extant literature related to the release of heavy metals into water and soil content, that is affecting agricultural practices, and hence, serve as possible risks for human health. Thus, the aim of this study is to review previous research work done by other authors on heavy metals in water and soils, detection, poisoning, damages to human health and treatments of agricultural soils as noted in some studies. The study adopts an extensive review of literature such as conference papers, journal articles, internet sources, books to find out concentration of heavy metals in agricultural soils and water. After analysis and review of such secondary articles, the current studies found that heavy metal in portable water and soil is a source of major concern and should be regularly checked and monitored by appropriate regulatory agencies. In addition, some previous researchers found that anthropogenic activities are identified as the main source of the increasing amounts of heavy metals found in water and soil. Some of the health hazards derived from repeated exposure to traces of heavy metals, including lead, cadmium, nickel, and zinc, were also reported in this study. The authors also stated the methods in which this contamination occurs and ways to prevent future contamination as discussed by various authors. This study concluded that heavy metals are the main cause of water pollution and impact human health worldwide. Keywords: Heavy Metal: Water: Contamination: Pollution: Human Health: Anthropogenic Factors: Nigeria.

Stabilization of heavy metals from lead-zinc ore tailings with sodium diethyl dithiocarbamate functionalized montmorillonite (DDTC-Mt): Leaching characteristics and remediating mechanism

The mining and processing of lead-zinc ores produce many lead-zinc ore tailings, which can cause harm by releasing toxic metal ions to the environment. Therefore, the leaching characteristics, acid generation capacity, and fractions of released heavy metals from two Pb-Zn tailings, one from Guangxi designated as F and another from Inner Mongolia designated as YD, have been investigated in this work. Here, sodium diethyl dithiocarbamate functionalized montmorillonite (DDTC-Mt) was synthesized to remediate both F and YD tailings. It was found that YD tailings have a stronger acid generation potential than F tailings, and both of them could be further oxidized and release acid. Moreover, YD showed a certain buffering capacity to acid rain due to its higher calcite content, while the leaching amounts of heavy metals from F was larger than YD resulting from the former’s higher weathering degree. DDTC-Mt resulted in a superior stabilization performance to Zn, Mn and Pb from both tailings with optimal stabilization ratios, which are all above 94%. The remediating effect of DDTC-Mt on F was better than that of YD, which could be ascribed to the fact that F contained lower amount of carbonate minerals because of a higher degree of weathering in the latter. The leaching amounts and stabilization ratios of the four elements increased with increasing time and dose of DDTC-Mt, however, temperature and pH showed little or no effect. Mineralogical analysis showed minerals in F and YD before and after leaching were mainly quartz, while the contents of sphalerite and pyrite in F-DDTC-Mt and YD-DDTC-Mt decreased although they were more than those in F and YD without DDTC-Mt after leaching for 72 h. DDTC-Mt could inhibit the release of heavy metals to a certain extent by covering the surface of tailings via complexation and precipitation. Furthermore, DDTC-Mt coating can prevent the oxidation of tailings.

Integration of Heavy Metal Pollution Indices and Health Risk Assessment of Groundwater in Semi-arid Coastal Aquifers, South Africa

The heavy metal contaminated groundwater results in serious health issues and hence this study attempts to address its sources of contamination using integrated techniques including indexed and statistical methods and its related health hazards. Groundwater pH varied from 5.3 to 8.3 indicating acidic to alkaline in nature. The heavy metal pollution index shows that the groundwater samples vary from low to high pollution class and 21% of the samples exceed the critical limit of 100 implying that they are highly polluted with respect to heavy metals and are unfit for human consumption. The heavy metal evaluation index reveals that all the groundwater samples fall under low pollution. The synthetic pollution index reveals that 2%, 74% and 24% of the samples are suitable, slightly and moderately polluted, respectively, with heavy metals. The water quality index reveals that 19% and 2% of the groundwater samples belong to the poor and very poor water quality category and are spatially situated on the central, northern and southern parts of the study region. Correlation matrix and principal component analysis revealed that weathering of aquifer matrix and anthropogenic activities are accountable for the release of heavy metals into groundwater. Furthermore, R-mode and Q-mode cluster analysis revealed two clusters that are linked to mixed sources including weathering and anthropogenic activities. Based on the hazard quotient, the order of heavy metal impact is Co>Pb>Cd>Zn>As>Mn>Cu>Cr>Fe>Ni for both children and adults. The hazard index values varied from 0.06 to 8.16 for children and from 0.02 to 2.14 for adults. In this study, it is discovered that 43% and 26% of groundwater samples pose a non-carcinogenic health risk in children and adults, respectively. This study highly recommends treatment of contaminated groundwater before consumption in order to protect and maintain public health. The results from this study can be useful for the local municipalities and the policy makers while considering management and mitigation plan to maintain the water quality and to control its adverse effect on human health.

Development of Ceramic Tiles from Philippine Nickel Laterite Mine Waste by Ceramic Casting Method

Siltation is the biggest environmental challenge associated with nickel laterite mining in the Philippines. The amount of silt generated is huge and one mitigation strategy currently employed by the mining companies is the construction of siltation ponds where the bulk of the clayey- and silt-sized surface runoffs is collected. However, this poses several serious environmental hazards such as landslides due to heavy rainfall and the potential release of hazardous heavy metals. A promising approach to reduce the risks associated with long-term storage of nickel mine waste (NMW) is to employ circular economy by repurposing it for ceramic applications. While generating useful materials with economic value out of a mine waste, it will result in a reduction in volume of waste for disposal. In this study, the method employed to produce NMW-based ceramic wall and floor tiles is slip casting as it is the most appropriate method in forming tiles with complex surface features. Five formulations of NMW-based slips were made for the casting of ceramic tiles and each slip was characterized for its suitability as raw material. The results of NMW characterization show that NMW could be utilized as raw materials for both ceramic wall and floor tiles and the addition of feldspar can enhance casting and physical properties.

The mechanistic investigation of geochemical fractionation, bioavailability and release kinetic of heavy metals in contaminated soil of a typical copper-smelter

Identifying the bioavailability and release-desorption mechanism of heavy metals (HMs) in soil is critical to understand the release risk of HMs. Simultaneously, the mechanistic investigation of affecting the bioavailability of HMs in soil is necessary, such as the grain-size distribution and soil mineralogy. Herein, the bioavailability of HMs (Cu, Cd, Ni, Pb, and Zn) in different area soils near a typical copper-smelter was evaluated by the sequential extraction technique (BCR), diffusive gradients in thin-films (DGT), and DGT-induced fluxes in sediments (DIFS) model. Results showed that the HMs proportion of the residual fraction in all soils was the highest. The average bioavailability concentration (CDGT) of Cu and Cd in industrial soil was the highest, with 45.12 μg· L−1 and 9.06 μg· L−1. The result of DIFS model revealed that the decreased order of the mean value of desorption rate constant (K-1) was Cd > Zn > Ni > Cu > Pb, 5.91 × 10−5, 4.96 × 10−5, 2.89 × 10−5, 9.64 × 10−6, and 8.69 × 10−6, respectively. According to the spatial distribution of release potential (R-value), the release potential of labile-Cu in agricultural soil was the highest, which was mainly attributed to fertilizer application in farmland. Simultaneously, the reduced hydroxyl was also related to the agricultural activities, resulting in the weakened adsorption capacity of HMs by soil. Redundancy analysis (RDA) results showed that the bioavailability of Cd, Ni, and Zn was mainly driven by soil pH, while the bioavailability of Cu and Pb was primarily driven by dissolved organic carbon (DOC). Meanwhile, carbonate minerals had a positive correlation with the bioavailability of Cd, Ni, and Zn, which could promote the release of HMs in mining soil as chemical weathering progresses. In conclusion, this study provides a structured method which can be used as a standard approach for similar scenarios to determine the geochemical fractionation, bioavailability, and release kinetics of heavy metals in soils.

Risk of low stability Saccharomyces cerevisiae ATCC 9763-heavy metals complex in gastrointestinal simulated conditions

The biosorption of heavy metals by microorganisms has attracted the interest of food researchers as the last approach to reduce the risk of their absorption in the human body. But the stability of yeast-metal complexes under simulated gastrointestinal conditions has not been investigated. In this study stability of complex as well as isotherm and kinetic models of biosorption have been studied. Also, the impact of some pretreatment on yeast biosorption was studied to check the possible impact of different environmental conditions in food processing. Data showed a risk of heavy metal release in simulated gastrointestinal conditions. The best biosorption of metals from aqueous solutions by Saccharomyces (S.) cerevisiae may be achieved after NaOH pretreatment for Mercury (Hg) 92.7%. While biosorption of Lead (Pb) 37.48%, Arsenic (As) 19.44%, and Cadmium (Cd) 39.9% by untreated yeast were better. In gastrointestinal conditions, Hg and Cd-yeast complexes were more stable and biosorption of Cd and Pb increased. Bonds of As and Hg-yeast complexes in digestion conditions were reversible. The metals biosorption by untreated yeast followed the pseudo-second-order kinetic and the Langmuir isotherm model for Hg, Pb, and Cd and Freundlich for As. Results showed that biosorption of heavy metals by S. cerevisiae, although may decrease metal bioavailability in fermented foods, the complex is not enough stable in gastrointestinal conditions.

Evaluating the Performance of Lateritic Soil Stabilized with Cement and Biomass Bottom Ash for Use as Pavement Materials

From the perspective of sustainable waste management and its environmental impact, waste biomass bottom ash (BA) remains problematic and challenging to use as a recycling material for civil engineering infrastructures. This study evaluated the performance of lateritic soil (LS), stabilized with cement and biomass BA, as a subbase material. BA has been considered a replacement material in LS prior to the introduction of hydraulic cement stabilization means. The geotechnical engineering tests comprised the modified Proctor test, the California Bearing Ratio (CBR) test, and the unconfined compression test. X-ray fluorescence (XRF) and X-ray diffraction (XRD) tests were conducted to investigate the mineralogical properties of the stabilized soil samples. The leachate test was performed with a permeability mold to measure the release of heavy metals. Finally, the benefits of using the stabilized subbase material were assessed using the mechanistic–empirical (M–E) pavement design approach. Based on the results obtained, the strength and stiffness characteristics of the stabilized soils indicate that the efficiency of the mix satisfied the Thailand highway specification. The admixture of 80% BA and 5% cement is suggested for use as a soil–cement subbase material for flexible pavements, due to its good engineering and environmental properties. The results of the M–E design demonstrate the effectiveness of the stabilized soil presented herein. The study’s outcomes are predicted to promote the utilization of waste BA as a promising pavement material.

Image analysis reveals cellular fragmentation of Spirulina platensis upon treatment with heavy metal ions

Bioremediation is a promising technique that can be used to decrease the environmental discharge of Heavy Metal (HM) such as copper, and zinc. Although studies have addressed the cytotoxic effects of HMs, however, the effect of HMs on the geometry of bacterial species such as Spirulina platensis (S. platensis) remains unknown. Quantitative analysis of parameters such as cell perimeter, cell count, and cell distribution shall greatly improve the efficiency of environmental monitoring. Therefore, this study demonstrates the use of an open-source image analysis tool (ImageJ/Fiji) to quantify the aforementioned parameters to analyze the extent of damage caused by lethal concentration of > 2 mg/L of Cu2+ and > 6 mg/L of Zn2+ which disintegrates S. platensis cells into smaller fragments and subsequently affects their structural parameters in perimeter and cell distribution. In summary, this article demonstrates the use of an image analysis platform to quantify the geometric parameters of microbes for environmental monitoring.

Hydrogel-Based Adsorbent Material for the Effective Removal of Heavy Metals from Wastewater: A Comprehensive Review.

Water is a vital resource that is required for social and economic development. A rapid increase in industrialization and numerous anthropogenic activities have resulted in severe water contamination. In particular, the contamination caused by heavy metal discharge has a negative impact on human health and the aquatic environment due to the non-biodegradability, toxicity, and carcinogenic effects of heavy metals. Thus, there is an immediate need to recycle wastewater before releasing heavy metals into water bodies. Hydrogels, as potent adsorbent materials, are a good contenders for treating toxic heavy metals in wastewater. Hydrogels are a soft matter formed via the cross-linking of natural or synthetic polymers to develop a three-dimensional mesh structure. The inherent properties of hydrogels, such as biodegradability, swell-ability, and functionalization, have made them superior applications for heavy metal removal. In this review, we have emphasized the recent development in the synthesis of hydrogel-based adsorbent materials. The review starts with a discussion on the methods used for recycling wastewater. The discussion then shifts to properties, classification based on various criteria, and surface functionality. In addition, the synthesis and adsorption mechanisms are explained in detail with the understanding of the regeneration, recovery, and reuse of hydrogel-based adsorbent materials. Therefore, the cost-effective, facile, easy to modify and biodegradable hydrogel may provide a long-term solution for heavy metal removal.

Feasibility of Remediation of Heavy-Metal-Contaminated Marine Dredged Sediments by Active Capping with Enteromorpha Biochar

Enteromorpha biochar (BC) has been proposed as a potential absorbent in the marine environments. This study attempts to understand the process of active capping using Enteromorpha BC to prevent the release of heavy metals (Pb and Cd) from contaminated marine dredged sediments. The capping efficiency was assessed with a series of lab-scale column experiments. Results showed that the Enteromorpha BC exhibits rough pore structure and higher specific surface area, as well as more surface organic functional groups, which is favorable for its adsorption capacity and selectivity towards heavy metals. The capping thickness of 2 cm for Enteromorpha BC was sufficient to prevent the release of heavy metals from sediments, with the capping efficiency of 47% for Pb and 62% for Cd. Kinetic studies showed that heavy metals released into the overlying water can be described by a three-parameter sigmoidal kinetic model. Importantly, the fractions of heavy metals in the dredged sediments below the capping layer were analyzed to reveal the capping remediation mechanism. The outcomes of the present study indicate that capping with Enteromorpha BC is a promising method to regulate the water environment by preventing the release of heavy metals from the contaminated dredged sediments.

Species-specific bioaccumulation and health risk assessment of heavy metal in seaweeds in tropic coasts of South China Sea

Seaweeds are widely known superfood in coasts where most anthropogenic heavy metal discharges are inputted and stored. The present study analyzed 11 seaweed species and 13 heavy metals to test the hypothesis that the species-specific capacity of heavy metal bioaccumulation had great significance to health risk of human. The seaweeds were collected from tropic coasts of Hainan Island. We comparatively determined the bioaccumulation level of metals in different species. The results revealed that the red algae mainly concentrated V, Se, Mn, Ni, and Ag. The brown algae mainly concentrated Cr, Co, Cu, Cd, As and Fe, while the green algae mainly concentrated Zn and Pb. The cluster analysis, principal component analysis and metal pollution index indicated that Padina crassa, Sargassum thunbergii, Caulerpa racemosa and Asparagopsis taxiformis showed similar metal bioaccumulation behavior. The health risk assessment revealed that the overall hazard index (HI) of seaweeds consumption to adults was less than 1, while the HI of Sargassum oligocystum, Turbinaria ornate, Sargassum polycystum and Sargassum thunbergii consumption to children was greater than 1, suggesting a moderate or high risk to children. Moreover, the exposure amount and the carcinogenic risk parameter indicated that As and Cr were the limiting factor for seaweeds consumption. Overall, our findings here largely supported our hypothesis that the heavy metal bioaccumulation behavior and health risk was highly variable and complex among different species. We thus suggested that the species-specific health risk of heavy metals in seaweeds should be cautiously evaluated in natural environments.

ADSORPTION OF LEAD FROM CONTAMINATED WATER USING BIOSORBENT

For the past few years, environmental degradation caused by the discharge of heavy metals and organic contaminants has been a major source of worry. Using a natural adsorbent to tackle wastewater problems has recently been viewed as an environmentally friendly move that promotes sustainable development. Heavy metals have indeed been reduced in aqueous solutions using a variety of methods, include adsorption to the surfaces of agricultural residues. Lead is among the most toxic and common heavy metals found in industrial wastewater. In this research, adsorbents selected are moringa leaves, rice husk and coconut fibers, which are very low-cost materials, employed for the lead exclusion from industrial wastes. Thus, our study aims to investigate the ability of natural bio-sorbents to remove very toxic Pb2+ ions from aqueous solutions. Contact time, concentration, adsorbent-based dosage and pH were all evaluated as important factors in the adsorption mechanism. The adsorption efficiency was discovered to be pH dependent, rising as the solution pH was increased in the ranges of 2.5 to 6.5. After 120 min, the equilibrium state was reached, and the optimum removal rate was obtained with a 1.5 g adsorbent loaded weight. The adsorption equilibrium capability of the lead-adsorbing materials was evaluated and estimated utilizing linear Freundlich and Langmuir isotherms, with the experimental results fitting the Freundlich isotherm models.

Heavy metal residues, releases and food health risks between the two main crayfish culturing models: Rice-crayfish coculture system versus crayfish intensive culture system

High-density culturing with excessive feeding of commercial feed has caused heavy metals pollution to agricultural production system. In this study, the dynamic changes and transfer of heavy metals in rice-crayfish coculture system (RCCS) and crayfish intensive culture system (CICS) within a completed culture cycle were systematically quantified. Our results showed that Cd in feed represented more than 50% of the total Cd input, and the inputs of As and Cr were mainly from irrigation. The residues of As and Pb in RCCS were slightly higher than those in CICS, while the residues of Cd and Cr in RCCS were far fewer than those in CICS. Moreover, the metal pollution index in CICS was 0.781, while it was 0.543 in the RCCS. Furthermore, a large proportion of the Cd and Pb in CICS was released into the external environment through drainage. Notably, the absorption and solidification of heavy metals by straw did not increase the residues of As and Pb in the major components of RCCS in the second year. Compared to CICS, RCCS did not produce many heavy metal residues or cause heavy metal discharge pressure on the external environment, and its food product had a low risk of heavy metal contamination.

Effects of organic acids on heavy metal release or immobilization in contaminated soil

In order to explicit the environmental activity of heavy metals affected by different organic acids in soil, a batch incubation experiment was explored to investigate the influence of high relative molecular mass organic acid (HMWOA) (humic acid and fulvic acid) and low relative molecular mass organic acid (LMWOA) (threonic acid and oxalic acid) on the release or immobilization of Pb, Cu and Cd in soils. Results showed that LMWOA, especially threonic acid, had a good performance in the release of Pb, Cu and Cd from soils, and decrease in the fractions of HOAc-extractable, reducible and oxidable Pb, Cu and Cd. Conversely, HMWOA, especially humic acid, decreased the release of Pb, Cu and Cd, while it increased the fractions of HOAc-extractable, reducible and oxidable Pb, Cu and Cd, indicating that HMWOA can immobilize heavy metals. The release of Pb, Cu and Cd caused by LMWOA was attributed to the dissociation of soil organic matter and amorphous iron oxides since the total organic carbon and the water-soluble iron increased. The immobilization of Pb, Cu and Cd by HMWOA was attributed to the adsorption onto HMWOA followed by amorphous iron since HMWOA resulted in a significant decrease of zeta potential and an increase of amorphous iron oxide. It can be concluded that LMWOA has a potential application in soil washing remediation, while HMWOA can be used in the immobilization remediation for heavy metals contaminated soils.

ELECTRIC CURRENT INDUCED MITIGATION OF LEAD CONTAMINATION IN VETIVERIA ZIZANIOIDES

Rapidly expanding industrial areas ensues a negative impact on the soil chemistry, it delivers certain stubborn heavy metals in the soil. Inefficient emission management and pollution alleviation contributes discharge of heavy metals in the surroundings causing a threat to mankind. To subside the effect of heavy metal; most effective, cost free, solardriven, green technology phytoremediation has been adopted which indulges exploitation of hyper-accumulator plants. Heavy metal toxicity leads to production of reactive oxygen species causing oxidative stress to the plant cell. To mitigate the oxidative stress plant cell initiates production of antioxidative enzymes. The present experiment was setup for analysis and assessment of comparative study of physical (electrokinetic remediation) and chemical (chelators) amendments in enhancing antioxidative enzymes in response to the metal phytoxicity in Vetiveria zizanioides.

A typical case study from smelter-contaminated soil: new insights into the environmental availability of heavy metals using an integrated mineralogy characterization.

Mineralogy was an important driver for the environmental release of heavy metals. Therefore, the present work was conducted by coupling mineral liberation analyzer (MLA) with complementary geochemical tests to evaluate the geochemical behaviors and their potential environmental risks of heavy metals in the smeltercontaminated soil. MLA analysis showed that the soil contained 34.0% of quartz, 17.15% of biotite, 1.36% of metal sulfides, 19.48% of metal oxides, and 0.04% of gypsum. Moreover, As, Pb, and Zn were primarily hosted by arsenopyrite (29.29%), galena (88.41%), and limonite (24.15%), respectively. The integrated geochemical results indicated that among the studied metals, Cd, Cu, Mn, Pb, and Zn were found to bemore bioavailable, bioaccessible, and mobile. Based on the combined mineralogical and geochemical results, the environmental release of smelter-driven elements such as Cd, Cu, Mn, Pb, and Zn were mainly controlled by the acidic dissolution of minerals with neutralizing potential, the reductive dissolution of Fe/Mn oxides, and the partial oxidation of metal sulfide minerals. The present study results have confirmed the great importance of mineralogy analysis and geochemical approaches to explain the contribution of smelting activities to soil pollution risks.