High Concentrations Of Heavy Metals Research Articles

Accumulation of heavy metals and human health risk assessment of vegetable consumption from a farm within the Korle lagoon catchment

The Korle lagoon is known to have high concentration of heavy metals. The use of land for agriculture and water for irrigation within the Korle Lagoon's catchment constitutes a potential health risk. Due to this, the study assessed the concentration of heavy metals in some vegetables (Amaranth, Spinach, Eggplant, Lettuce, Cauliflower, and Onion) and their corresponding soil from a farm within the Korle Lagoon's catchment. The estimated daily intake (EDI), hazard quotient (HQ), and lifetime cancer risk (LCR) was used to assess their health risks. Among the vegetables tested, heavy metals in lettuce exceeded their recommended guideline level. Additionally, the concentrations of Fe (265.94–3599.60 mg/kg) and Zn (76.77–294.70 mg/kg) in all vegetables were above the recommended guideline level. Also, Zn (227.30–534.57 mg/kg) and Pb (101.53–407.58 mg/kg), in soil were above the recommended guideline level for soil. The results also showed not only the severity of heavy metal pollution of soil in the study area, but also risks that were deemed carcinogenic and noncarcinogenic to both adults and children as a result of consumption of vegetables from the study area. The hazard index for adults (0.46–41.156) and children (3.880–384.122), were high for all vegetables tested and are associated with cancer risk due to high Cr and Pb levels. The risk assessment showed that children may suffer more carcinogenic and noncarcinogenic health risk than adults. The study concluded that vegetables grown within the Korle lagoon's catchment is not suitable for consumption due to the associated adverse health effect.

Recent developments in ultrafiltration membrane technology for the removal of potentially toxic elements, and enhanced antifouling performance: A review

The presence of high concentrations of heavy metals (potentially toxic elements) in water bodies generates serious environmental issues and health problems that led to a dramatic increase in wastewater treatment costs. Therefore, it is imperative to develop low-cost and efficient technologies for removing these contaminants from wastewater. Membrane processes are advanced techniques for water treatment and ultrafiltration membrane (UF) has some advantages over other membranes as it requires low pressure to perform However, the UF membrane separates contaminants mainly by size exclusion mechanism, resulting in poor decontamination performance for potentially toxic elements and high susceptibility to membrane fouling. The performance of the UF membrane is often affected by organic and biofouling. Hence, researchers are still looking forward to developing new types of UF membranes that will make them more effective for potentially toxic elements removal and overcome the obstacle of fouling. This review aims to provide an overview of the application of UF membranes in potentially toxic element removal through bibliometric analysis and literature review. The incorporation of various organic, inorganic, carbon-based, and composite-based nano-materials into polymers such as zeolites, metal–organic frameworks (MOFs), and graphene oxide (GO) gave encouraging results for the removal of potentially toxic elements from water. Moreover, this review discusses the mechanisms of fouling in UF membranes and how different techniques can be used to control it. In the end, all the materials are evaluated and compared based on their efficiency, toxicity, simplicity in preparation, popularity, and cost efficiency to provide an overall critical view of the work done in this area. Also, the major challenges and limitations of the use of UF membranes are provided which will help to set the direction of future research.

Identifikasi Bakteri Pereduksi Logam Pb dalam Bioremediasi Sampel Air Sungai Citarum Menggunakan Analisis Gen 16s rRNA

The bioremediation technique is an effort to remove the heavy metal Pb in samples of Citarum river water. High concentrations of heavy metals harm the environment, so Pb metal-reducing bacteria are needed as a pollution solution. Bioremediation uses bacteria. Bacteria are identified by molecular methods, namely sequencing analysis techniques, because they are more accurate. To determine the nucleotide sequence of Pb metal-reducing bacteria isolates and which bacterial species can reduce Pb metal. The methodology used is primary data collection, namely conducting research directly, namely the stages of bacterial purification through gram staining techniques, pure colonies, then proceeding to the DNA isolation stage. The isolated DNA is then electrophoresed. The electrophoresis results are then purified and proceed to the sequencing stage. The feasibility test results were to obtain pure DNA from the reducing bacteria. The next step was PCR amplification of the 16S rRNA gene of Pb-reducing bacteria. The research results started at the DNA isolation stage and obtained a purity of 1.80. The PCR results were in the form of amplification of the 16S rRNA gene of Pb-reducing bacteria. Electrophoresis obtained the results of DNA bands measuring ± 1400 bp—phylogenetic tree analysis with 99.60% relatedness to Bacillus cereus, which can reduce Pb. Bacillus cereus species can carry out detoxification mechanisms against the toxic effects of Pb metals, such as—biosorption, bioaccumulation, reduction, solubilization, precipitation (formation of extracellular complexes), and methylation.

Diversity of DNA Sequences from Pathogenic and Potentially Pathogenic Eukaryotic Microorganisms in Protected Granite Mountain Rocks

Rain-fed mountain granite rock basins are temporary habitats conditioned by a fluctuating environment and the unpredictability of precipitation or flooding rates. These small highland freshwater habitats remain largely unexplored at the microbial level. The aim of this work is to report the presence in these habitats of genetic sequences of microbial eukaryotes that are pathogens and potential pathogens of humans, wildlife, cattle, crops as well as of other microorganisms. We sequenced the hypervariable region v4 of the 18S rDNA gene from environmental DNA of sediments taken from 21 rock basins in a National Park in Spain. More than a fifth (21%) of the eukaryotic Operational Taxonomic Units (OTUs) found are ascribed to pathogenic (within 11 Phyla) and potential pathogenic (within 1 phylum, the Chytridiomycota) microorganisms. Some OTUs retrieved are of agro-economic and public health importance (e.g., Pythium spp., Lagenidium spp., Candida spp. and Vermamoeba vermiformis). In 86% of the basins, the most abundant OTUs were affiliated to Chytridiomycota, a broad fungal group including saprozoic and parasitic taxa. Two OTUs affiliated to chytrids were significantly correlated with high concentrations of heavy metals. The high proportion of chytrid-like microbial sequences found emphasises the role of these freshwater habitats for adding knowledge regarding the ecological trade-offs of the still rather unknown Chytridiomycota. Our results show that rain-fed rock basins may be model habitats for the study and surveillance of microbial community dynamics and genetics of (mainly opportunistic) microbial pathogens.

Controlling heavy metals pollution is vital for the restoration of carbon and nitrogen transformation function of mangrove ecosystems in the Greater Bay Area, China

Pollutants, especially for heavy metals (HMs), discharged from anthropogenic activities are the potential risks to newly planted mangrove forests in the restoration process. Thus, it is crucial to investigate how HMs affect the biological processes that take place in these mangrove habitats, e.g., the transformation of carbon and nitrogen. In this study, correlations between HMs pollution, carbon storage, and nitrogen biotransformation in the Great Bay Area (GBA) were examined at five typical sites with different mangrove restoration ages. The results indicated that there were distinct differences in the concentration distribution of HMs (ranges: 0.2–369.7 mg/kg) at five sample sites, with Cd (0.2–1.6 mg/kg) being the heavily polluted element in sediments. The fluctuation of SOC (16.0–25.7 mg/kg), δ13C (−27.5 to −20.2), and NO3−-N (1.2–3.3 mg/kg) was positively correlated with the content of HMs in sediments, indicating that these components in mangrove ecosystems might have similar emission source and pose a potential threat to mangrove carbon storage. Notably, sediments with high HMs concentration decelerated carbon decomposition rate of mangrove ecosystems, especially for sites with newly planted mangrove forest. Moreover, a large abundance of Euryarchaeota was found in the HO site, suggesting that HMs may promote the conversion of carbon to CH4. The inflow of contaminants also induced the significant increasing proportion of microorganisms related to nitrogen fixing, denitrification, and dissimilarity nitrogen reduction processes, resulting a decline in the stability of co-occurrence network of nitrogen transformation. Fortunately, mangrove site with the establishment of natural reserves and controlling pollutant discharge could contribute to the rapid restoration of its ecological function, e.g., nutrient cycling and co-occurrence stability, in SZ site. Therefore, future management should focus on the decrease of pollutants discharge and pay more attention to the ecological function restoration of mangrove wetlands in the GBA.

Does biochar in combination with compost effectively promote phytostabilization of heavy metals in soil under different temperature regimes?

The article presents the effect of a combined amendment, i.e., biochar+compost (BC), on the process of Cd, Cu, Ni, Pb and Zn immobilization in soil cultivated with L. perenne under freezing and thawing conditions (FTC). In particular, the speciation analysis of the examined elements in phytostabilized soils based on their response using the sequential extraction, and the variability of the soil microbiome using 16S rRNA gene amplicon sequencing were systematically assessed. Metal stability in soils was evaluated by the reduced distribution index (Ir). Plants were grown in pots for 52 days under greenhouse conditions. After termination, phytostabilization was continued in a temperature chamber for 64 days to provide FTC. As a result, it was noted that biomass yield of L. perenne was promoted by BC (39 % higher than in the control pots) and reduced by FTC (45 % lower than in the BC-enriched soil not exposed to FTC). An efficacious level of phytostabilization, i.e., higher content of heavy metals in plant roots, was found in the BC-enriched soil, regardless of the changes in soil temperature conditions. BC improved soil pH before applying FTC more than after applying FTC. BC had the greatest impact on increasing Cu stability by redistributing it from the F1 and F2 fractions to the F3 and F4 fractions. For most metals, phytostabilization under FTC resulted in an increase in the proportion of the F1 fraction and a decrease in its stability. Only for Pb and Zn, FTC had greater impact on their stability than BC addition. In all soil samples, the core genera with about 2–3 % abundances were Sphingomonas sp. and Mycobacterium sp. FTC favored the growth of Bacteroidetes and Proteobacteria in soil. Microbial taxa that coped well with FTC but only in the absence of BC were Rhodococcus, Alkanindiges sp., Flavobacterium sp., Williamsia sp. Thermomonas sp.

Imaging the distribution of nutrient elements and the uptake of toxic metals in industrial hemp and white mustard with laser-induced breakdown spectroscopy

Considering the quickly growing cannabis farming industry worldwide, it is important to do research on the ability of hemp to grow in heavy metal-contaminated soil. Hemp is a hyperaccumulator of heavy metals such as Cadmium (Cd) and Lead (Pb) and it can grow in soils with high concentrations of heavy metals. To gain more insight into the uptake and translocation of Cd and Pb in Cannabis sativa L., we exposed three-day old seedlings to solutions of varying concentrations of Cd and Pb for three days. Subsequently, we performed toxicology studies and analysed the localization and total uptake of heavy metals as well as essential and trace elements using Laser-Induced Breakdown Spectroscopy (LIBS) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). We subsequently conducted a toxicity test and LIBS bioimaging on the reference plant Sinapis alba L. A low concentration of 20 μM of CdCl2 and PbCl2 was toxic for S. alba, while for C. sativa a concentration of 500 μM of CdCl2 and 50 μM of PbCl2 decreased the growth of the plants. According to the 2D bioimaging LIBS maps, heavy metals in all concentrations accumulated mostly in roots, translocation to stem and leaves was not observed. These results were confirmed by ICP-OES. Additionally, we were able to do bioimaging of important elements (e.g., Ca, Cu, Mg and Sr) in the plants. Based on the data from LIBS and ICP-OES, we were able to create a calibration curve for Pb. There, the Pb intensities distributed over a number of pixels in LIBS maps were correlated to concentration values from the ICP-OES.

Investigating heavy-metal soil contamination state on the rate of stomach cancer using remote sensing spectral features

Heavy metal (HM) contamination in agricultural soils has been a serious environmental and health problem in the past decades. High concentration of HM threatens human health and can be a risk factor for many diseases such as stomach cancer. In order to investigate the relationship between HM content and stomach cancer, the under-study area should be adequately large so that the possible relationship between soil contamination and the patients' distribution can be studied. Examining soil content in a vast area with traditional techniques like field sampling is neither practical nor possible. However, integrating remote sensing imagery and spectrometry can provide an unexpensive and effective substitute for detecting HM in soil. To estimate the concentration of arsenic (As), chrome (Cr), lead (Pb), nickel (Ni), and iron (Fe) in agricultural soil in parts of Golestan province with Hyperion image and soil samples, spectral transformations were used to preprocess and highlight spectral features, and Spearman's correlation was calculated to select the best features for detecting each metal. The generalized regression neural network (GRNN) was trained with the chosen spectral features and metal containment, and the trained GRNN generated the pollution maps from the Hyperion image. Mean concentration of Cr, As, Fe, Ni, and Pb was estimated at 40.22, 11.8, 21,530.565, 39.86, and 0.5mg/kg, respectively. Concentrations of As and Fe were near the standard limit and overlying the pollution maps, and patients' distribution showed high concentrations of these metals can be considered as stomach cancer risk factors.

Geochemical Response of Surface Environment to Mining of Sn-Pb-Zn Sulfide Deposits: A Case Study of Dachang Tin Polymetallic Deposit in Guangxi

The rational development of mineral resources provides necessary materials for economic development, but environmental pollution caused by mining activities is an inevitable consequence. Here, we present a case study of Chehe Town in Guangxi, an area with integrated metals mining and smelting. The geochemical distribution, migration, and transformation behaviors of Cd and other heavy metals were studied in detail by systematically collecting surface media such as atmospheric dust, surface water and stream sediments, ores, tailings, mine drainage, soil, and crops in and around the mining area. We used these data to explore the geochemical response of the surface environment to mining and smelting of metal sulfide deposits. The annual flux of Cd and other heavy metals near the mining and smelting sites was high. Due to the topography, heavy metals in the atmosphere are mainly transported via vertical deposition, influencing areas downwind for 25 km. The mine drainage exceeded As and Zn standards but had little impact on the surface water. The surface water quality was good, without acidification. Risks due to ore were much higher than that for tailings. Heavy metals buffered by surrounding carbonate rocks and secondary minerals mainly migrated as solid particles, resulting in the contamination of stream sediment by heavy metals. In mountainous areas, rivers are mainly affected by topography, flowing fast and dominated by downcutting, which caused heavy metal pollution in the sediment have a limited effect on the soil near the river. Heavy metal concentrations in the cultivated soil were greatly influenced by external input such as substantial atmospheric dust. However, only Cd accumulated in the crops, with very high concentrations in rice, but safe and edible levels in corn. Thus, in the mining area, the most sensitive to heavy metals was the atmospheric environment. High concentrations of heavy metals beyond the ore district are mainly concentrated in the sediment, with distant impacts. Therefore, it is necessary to monitor and control risks associated with sediment transport, conduct treatment, and adjust crop planting. The soil, river, and agriculture respond differently to mining activities, but the risk is low and can be managed as needed.

A halophilic Chromohalobacter species from estuarine coastal waters as a detoxifier of manganese, as well as a novel bio-catalyst for synthesis of n-butyl acetate.

Anthropogenic pollution due to ferro-manganese ore transport by barges through the Mandovi estuary in Goa, India is a major environmental concern. In this study a manganese (Mn) tolerant, moderately halophilic Chromohalobacter sp. belonging to the family Halomonadaceae was isolated from the sediments of a solar saltern adjacent to this Mandovi estuary. Using techniques of Atomic absorption spectroscopy, Scanning electron microscopy-Energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy and Atomic Force Microscopy, the Chromohalobacter sp. was explored for its ability to tolerate and immobilize Mn in amended and unamended media with 20% natural salt concentration (w/v). In aqueous media supplemented with 0.1 mM Mn, the Chromohalobacter sp. was capable of sequestering up to 76% Mn with an average immobilization rate of 8 mg Mn /g /day. Growth rate kinetic analysis using Gompertz mathematical functions was found to model the experimental data well. The model inferred that the maximum growth rate of Chromohalobacter sp. was at 10% natural salt concentration (w/v). The Chromohalobacter sp. was further found to be multimetal tolerant showing high tolerance to Iron (Fe), Nickel (Ni) and Cobalt (Co), (each at 4 mM), and tolerated Manganese (Mn) up to 6 mM. Morphologically, the Chromohalobacter sp. was a non-spore forming, Gram negative motile rod (0.726 μ× 1.33 μ). The adaptative mechanism of Chromohalobacter sp. to elevated Mn concentrations (1 mM) resulted in the reduction of its cell size to 0.339 μ× 0.997 μ and the synthesis of an extracellular slime, immobilizing Mn from the liquid phase forming Manganese oxide, as confirmed by Scanning Electron Microscopy. The expression of Mnx genes for manganese oxidation further substantiated the finding. This bacterial synthesized manganese oxide also displayed catalytic activity (∼50% conversion) for the esterification of butan-1-ol with CH3COOH to yield n-butyl acetate. This Chromohalobacter sp. being indigenous to marine salterns, has adapted to high concentrations of heavy metals and high salinities and can withstand this extremely stressed environment, and thus holds a tremendous potential as an environmentally friendly "green bioremediator" of Mn from euryhaline environments. The study also adds to the limited knowledge about metal-microbe interactions in extreme environments. Further, since Chromohalobacter sp. exhibits commendable catalytic activity for the synthesis of n-butyl acetate, it would have several potential industrial applications.

The influence of diverse fertilizer regimes on the phytoremediation potential of Pteris vittata in an abandoned nonferrous metallic mining site

Organic waste comprises a large amount of hydrocarbon containing organic substances, which is regarded as a potential resource rather than simply a waste. A field experiment was conducted in a poly-metallic mining area to investigate the potential of organic waste to facilitate the soil remediation process. Different organic wastes and a commonly used commercial fertilizer were added to heavy metal contaminated soil, which was under phytoremediation using the As hyperaccumulator Pteris vittata. The influence of diverse fertilizer regimes on the biomass of P. vittata and heavy metal removal by P. vittata, was investigated. The soil properties were analyzed after the application of phytoremediation with or without the addition of organic wastes. Results indicated that sewage sludge compost is an appropriate amendment to improve the phytoremediation efficiency. Compared to the control, the application of sewage sludge compost significantly reduced the extractability of As in soil by 26.8 %, and increased the removal of As and Pb by 26.9 % and 186.5 %, respectively. The highest removal of As and Pb reached 33 and 34 kg/ha, respectively. The sewage sludge compost-strengthened phytoremediation improved soil quality. And the diversity and richness of the bacterial community were improved, as represented by the increase in Shannon and Chao index. With improved efficiency and acceptable cost, the organic waste-strengthened phytoremediation can be used to control the risks posed by high concentrations of heavy metals in mining areas.

Heavy metal transportation from polluted water into human through fodder plants and farmed animals

Abstract Herein we have determined the heavy metals concentrations (Pb, Cd, and Ni) estimated in River Swat water, irregated soils samples, fodder plant’s parts, farmed animal milk/meat samples and human blood from two location Mingora and Barikot in District Swat, Pakistan, using atomic absorption spectrophotometer. Heavy metals such as Cd, Pb, and Ni were found 0.016 ± 0.008, 0.50 ± 0.03, and 0.022 ± 0.004 mg/L in Mingora drain water, respectively, while in the Barikot sample the aforementioned metal were in the range of 0.014 ± 0.01, 0.29 ± 0.02, and 0.108 ± 0.08 mg/L. In the field water samples of Mingora the Cd, Pb and Ni were detected in the range of 0.008 ± 0.001, 0.65 ± 0.05 and 0.032 ± 0.006 mg/L, respectively, while in the field water samples of Barikot contained Cd = 0.016 ± 0.007 mg/L, Pb = 0.48 ± 0.04 mg/L and Ni = 0.043 ± 0.003 mg/L. Drain soil of Mingora contained the highest concentrations of heavy metals, with Cd = 3.9 ± 0.62 mg/kg, Pb = 45.5 ± 3.2 mg/kg, and Ni = 19.95 ± 2.1 mg/kg, whereas field soil contained Cd = 1.6 ± 0.44 mg/kg, Pb = 54.5 ± 2.26 mg/kg, and Ni = 34.75 ± 3.2 mg/kg. Cd in the Barikot drain soil was 3.95 ± 0.71 mg/kg, while it was 0.8 ± 0.06 mg/kg in the field soil. Lead in the same drain sample was 33 ± 3.23 mg/kg, while it was 72 ± 4.15 mg/kg in the field sample. Ni concentrations in Barikot drain soil samples was 13.85 ± 1.1 mg/kg, while 6.9 ± 0.8 mg/kg was detected in field samples. From the results it can be concluded that appreciable concentrations of heavy metals are present in milk and meat samples of farmed animals whereas significant quantities are also there in human blood samples indicating the transport of the selected metals from water through fodder plants into human. However, it may not be the sole reason heavy metal contaminations in human blood other factors like inhalation etc. may also be equally responsible.

Heavy metal effects on multitrophic level microbial communities and insights for ecological restoration of an abandoned electroplating factory site

The response of soil microbes to heavy metal pollution provides a metric to evaluate the soil health and ecological risks associated with heavy metal contamination. However, a multitrophic level perspective of how soil microbial communities and their functions respond to long-term exposure of multiple heavy metals remains unclear. Herein, we examined variations in soil microbial (including protists and bacteria) diversity, functional guilds and interactions along a pronounced metal pollution gradient in a field surrounding an abandoned electroplating factory. Given the stressful soil environment resulting from extremely high heavy metal concentrations and low nutrients, beta diversity of protist increased, but that of bacteria decreased, at high versus low pollution sites. Additionally, the bacteria community showed low functional diversity and redundancy at the highly polluted sites. We further identified indicative genus and “generalists” in response to heavy metal pollution. Predatory protists in Cercozoa were the most sensitive protist taxa with respect to heavy metal pollution, whereas photosynthetic protists showed a tolerance for metal pollution and nutrient deficiency. The complexity of ecological networks increased, but the communication among the modules disappeared with increasing metal pollution levels. Subnetworks of tolerant bacteria displaying functional versatility (Blastococcus, Agromyces and Opitutus) and photosynthetic protists (microalgae) became more complex with increasing metal pollution levels, indicating their potential for use in bioremediation and restoration of abandoned industrial sites contaminated by heavy metals.

Energy-related wastewater contamination alters microbial communities of sediment, water, and amphibian skin

To inform responsible energy development, it is important to understand the ecological effects of contamination events. Wastewaters, a common byproduct of oil and gas extraction, often contain high concentrations of sodium chloride (NaCl) and heavy metals (e.g., strontium and vanadium). These constituents can negatively affect aquatic organisms, but there is scarce information for how wastewaters influence potentially distinct microbiomes in wetland ecosystems. Additionally, few studies have concomitantly investigated effects of wastewaters on the habitat (water and sediment) and skin microbiomes of amphibians or relationships among these microbial communities. We sampled microbiomes of water, sediment, and skin of four larval amphibian species across a gradient of chloride contamination (0.04–17,500 mg/L Cl) in the Prairie Pothole Region of North America. We detected 3129 genetic phylotypes and 68 % of those phylotypes were shared among the three sample types. The most common shared phylotypes were Proteobacteria, Firmicutes, and Bacteroidetes. Salinity of wastewaters increased dissimilarity within all three microbial communities, but not the diversity or richness of water and skin microbial communities. Strontium was associated with lower diversity and richness of sediment microbial communities, but not those of water or amphibian skin, likely because metal deposition occurs in sediment when wetlands dry. Based on Bray Curtis distance matrices, sediment microbiomes were similar to those of water, but neither had substantial overlap with amphibian microbiomes. Species identity was the strongest predictor of amphibian microbiomes; frog microbiomes were similar but differed from that of the salamander, whose microbiome had the lowest richness and diversity. Understanding how effects of wastewaters on the dissimilarity, richness, and diversity of microbial communities also influence the ecosystem function of communities will be an important next step. However, our study provides novel insight into the characteristics of, and associations among, different wetland microbial communities and effects of wastewaters from energy production.

Progress and Challenges of Biological Leaching of Heavy Metal in Coal Ash from a Power Plant

Bioleaching is a technique for reducing the heavy metal content of coal ash by using bacteria, fungi, or yeast. Previous studies in heavy metal bioleaching of coal ash discussed the factors affecting the process, but as yet there is little information on the challenges of using microorganisms. Therefore, this study aimed to obtain comprehensive information regarding the use of microorganisms in heavy metal bioleaching. Heavy metal concentrations in coal ash are low, and the metals are diverse. The components of coal ash are complexes that cannot leach certain heavy metals according to previous studies. These low concentrations and complex components make it difficult to investigate the bioleaching mechanism. The combination of biological and chemical interactions involves various components in this system. The high concentration of iron and heavy metal leached could be toxic for microorganisms. The process is influenced by several factors, such as particle size, pH, and pulp density. Most heavy metal bioleaching studies on coal ash have been conducted on a small scale to control conditions affecting the process. Bioleaching kinetics in coal is a liquid-solid reaction that can be represented by the shrinking core model, which was mainly used in this study.

Effectiveness of bio- phytoremediation on heavy metal contaminated soils: A review

The need to restore the environment contaminated with heavy metals to its original ornear original status has become necessary due to the harm high concentration of heavy metals cause to the environment and the food chain. In this review, different remediation approach was considered, their merits and short coming. Focus was more on bio-phytoremediation: use of some selected plants and micro-organisms to decontaminate heavy metals from contaminated sites. . Differentplant species especially hyper accumulative plants were used to decontaminate heavy metals from contaminated site. Vetiver grass (Vetiveriazizanioides) was more effective among all the plant species used. It is environmentally friendly and cost effective. Its ability to accumulate and uptake heavy metals from the soil and translocate same to the shoot was high. Combination of both plants and micro-organisms proved to be more effective with a faster result in remediating a heavy metal polluted soil. Amendment of the soil with organic manures significantly increased the percentage of heavy metals removed from the soil and reduced the uptake of contaminants (heavy metals) from the plant tissues.

Investigations Concerning Heavy Metals Dynamics in Reynoutria japonica Houtt.-Soil Interactions.

Reynoutria japonica Houtt (RJ) is an extremely invasive plant species, found nowadays in a wide range of habitats, including those polluted with heavy metals (HM). The aim of this study was to investigate HM dynamics in RJ-soil interactions in five habitats historically polluted with HM located in Baia Mare city, Romania. The concentrations of major metal elements (Cd, Cu, Pb, Zn) in plant tissues (roots, stems, leaves) and soil samples collected from the study sites were analyzed via portable ED-XRF spectroscopy (converted), and the translocation factor (TF) and bioconcentration factor (BCF) were calculated. The mean values of HM in soil samples collected from the study sites exceeded the threshold limit values established by Romanian legislation. Generally, the highest concentration of Cd was recorded in the above-ground part of the plant (stem and leaves), while for Cu, Pb and Zn, the highest values (with few exceptions) were recorded in the root. The metal transfer was highly effective from soil to RJ, such that all four of the HM studied exceeded the normal range of metals in a plant. Analysis of metal concentrations in plant tissues showed an efficient movement of Cd and Zn to the above-ground parts of the plant, a tendency particularly pronounced in the case of Cd (TF and BCF > 1), while Pb was the least bioaccumulated HM. It may be concluded that RJ is able to tolerate high concentrations of HM, being a good phytoextractor for Cd and Zn.

Extraction of Humic Acids from Lignite and Its Use as a Biochar Activator.

Current research focuses on extracting humic acid (HA) compounds from low-rank coals to obtain high value-added products. In this study, HAs with high purity and low heavy metal content were obtained from lignite by combining acid pretreatment with hydrothermal treatment. Scanning electron microscopy, elemental analysis (EA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, and inductively coupled plasma optical emission spectrometry (ICP-OES) were used to analyze raw lignite and HAs. The effects of acid and hydrothermal treatments on the inorganic elements, functional groups, and yield of HAs were examined. The results showed that acid treatment reduced the ash content of lignite from 20 to 9%, and hydrothermal treatment increased the yield of HAs from 36 to 68%. The chemical properties of HAs exhibited an increase in molecular weight and improved aromaticity after acid and hydrothermal treatments. The results of ICP-OES analysis suggested that the combined method of acid and hydrothermal treatments resulted in a significant reduction of heavy metal elements in HAs. FTIR analysis confirmed the results and demonstrated that the extracted HA from nitric acid pretreated and hydrothermal generation of lignite PHA was rich in carboxyl and phenolic functional groups. PHA was applied to biochar as an activator for the adsorption of heavy metal ions. The experimental results showed that PHA was successfully loaded onto biochar and introduced a large number of functional groups, and the adsorption capacity of the modified biochar for Pb2+ was effectively improved.

Enhanced electrokinetic remediation by magnetic induction for the treatment of co-contaminated soil

The electroplating industry site is an important reservoir of per- and poly-fluoroalkyl substances (PFASs) and heavy metals. In this work, a novel electrokinetic in-situ chemical oxidation system was established to restore an actual soil co-contaminated with high concentrations of heavy metals (Cr, Cu, Zn and Ni) and PFASs. Potassium persulfate (PS, K2S2O8) and industrial waste steel slag were used as the oxidant and activator, respectively. The steel slag was evenly added in the soil, while PS was dosed in the cathode chamber. Citric acid fermentation broth produced by Aspergillus niger was added in the anode chamber to act as the metal chelator. A periodic alternating magnetic field was employed to enhance the catalytic performance of steel slag for PS. After 15-day treatment, 86.7% of PFASs and 87.2% of heavy metals were removed without PFASs accumulation in the electrolyte, with a defluorination percentage of 79.2%. The remediated soil had no phytotoxicity for wheat seed growth based on 7-day cultivation results. The quality of remediated soil could reach the national Class II criteria for residential use. Electron paramagnetic resonance spectroscopy analysis demonstrated that SO4•– and •OH were the major oxidative radicals responsible for PFASs degradation. Adding steel slag in the soil performed better than that in the cathode chamber based on pollutant removal and alleviating soil acidification. Magnetic induction could enhance PS activation by promote the corrosion of steel slag and thermal activation, thus increasing electrical current and electroosmotic flow, enhancing the transport of citric acid and PS, significantly improving the removal efficiency of heavy metals and PFASs.

Physicochemical Technique in Municipal Solid Waste (MSW) Landfill Leachate Remediation: A Review

Leachate generation is among the main challenging issues that landfill operators must handle. Leachate is created when decomposed materials and rainwater pass through the waste. Leachate carries many harmful pollutants, with high concentrations of BOD, COD, colour, heavy metals, ammoniacal nitrogen (NH3-N), and other organic and inorganic pollutants. Among them, COD, colour, and NH3-N are difficult to be completely eliminated, especially with a single treatment. They should be handled by appropriate treatment facilities before being safely released into the environment. Leachate remediation varies based on its properties, the costs of operation and capital expenditures, as well as the rules and regulations. Up until now, much scientific and engineering attention was given to the development of comprehensive solutions to leachate-related issues. The solutions normally demand a multi-stage treatment, commonly in the form of biological, chemical, and physical sequences. This review paper discussed the use of contemporary techniques to remediate landfill leachate with an emphasis on concentrated COD, colour, and NH3-N levels with low biodegradability that is normally present in old landfill or dumping grounds in developing countries. A semi-aerobic type of landfill design was also discussed, as this concept is potentially sustainable compared to others. Some of the challenges and future prospects were also recommended, especially for the case of Malaysia. This may represent landfills or dumpsites in other developing countries with the same characteristics.