Metal Uptake Potential Research Articles

Carbonic anhydrase-mediated phosphogypsum degradation and enhanced CO2 sequestration: a promising sustainable strategy for biological resource utilization of phosphogypsum.

This study continues our previous investigation of the intrinsic degradation of phosphogypsum (PG) by indigenous microorganisms on amending adequate nutrients. We aim to unravel the intricate mechanisms involved in PG biotransformation by a bacterial consortium. We isolated and characterized seven multi-metal-resistant bacterial strains from a nutrient-amended PG-contaminated microcosm and identified them through 16S rRNA gene sequencing. Primarily aerobic, Gram-positive chemolithotrophs, these strains demonstrated significant heavy metal uptake and PG degradation potential. Further analysis revealed that all strains produced carbonic anhydrase (CA), while six also produced urease, which may facilitate microbial-induced carbonate precipitation. Microstructural and elemental analysis using scanning electron microscopy-energy-dispersive X-ray and X-Ray Diffraction (XRD) confirmed the PG bio-transformation, indicating substantial increases in carbonate concentrations and reductions in sulfate levels. The consortium, composed of seven urease- and CA-producing bacterial strains, effectively degraded PG, transforming it from an acidic to an alkaline state and significantly enhancing CO2 sequestration.

Microwave Irradiation vs. Structural, Physicochemical, and Biological Features of Porous Environmentally Active Silver–Silica Nanocomposites

Heavy metals and other organic pollutants burden the environment, and their removal or neutralization is still inadequate. The great potential for development in this area includes porous, spherical silica nanostructures with a well-developed active surface and open porosity. In this context, we modified the surface of silica spheres using a microwave field (variable power and exposure time) to increase the metal uptake potential and build stable bioactive Ag2O/Ag2CO3 heterojunctions. The results showed that the power of the microwave field (P = 150 or 700 W) had a more negligible effect on carrier modification than time (t = 60 or 150 s). The surface-activated and silver-loaded silica carrier features like morphology, structure, and chemical composition correlate with microbial and antioxidant enzyme activity. We demonstrated that the increased sphericity of silver nanoparticles enormously increased toxicity against E. coli, B. cereus, and S. epidermidis. Furthermore, such structures negatively affected the antioxidant defense system of E. coli, B. cereus, and S. epidermidis through the induction of oxidative stress, leading to cell death. The most robust effects were found for nanocomposites in which the carrier was treated for an extended period in a microwave field.

Uptake of Cu2+ by unicellular microalga Chlorella vulgaris from synthetic wastewaters is attenuated by polystyrene microspheres

Aquatic and terrestrial ecosystems are receiving micro- and macro-plastic pollutants alarmingly from various anthropogenic activities. The complications caused by microplastics are largely unexplored and need substantial studies. In the current study, we investigated the repressive effects of negatively and positively charged polystyrene microspheres of two variable sizes (0.05 and 0.5 μm) on functioning of unicellular green microalgae. For the purpose, a pollution-resistant microalgal species was isolated and identified by 18 S rRNA gene sequencing as Chlorella vulgaris. The functioning of the pure-cultured microalgal cells was then assessed in terms of their better metal (Cu2+) uptake potential with and without the provision of PS microspheres. The algal cells up took Cu2+ significantly (90% at 75 mg/L) after 15 days of aerobic incubation. However, positively charged polystyrene microspheres remarkably affected the uptake of Cu2+ and it was comparatively reduced to almost 50%, while negatively charged microspheres couldn't influence the Cu2+ uptake potential of C. vulgaris. In addition, size of the microspheres insignificantly affected the metal uptake potential of the microalgae. Unveiled facts of this investigation will be helpful for designing economical and efficient remedial systems based on the in-situ implication of microalgae.

A field study reveals links between hyperaccumulating Sedum plants-associated bacterial communities and Cd/Zn uptake and translocation

Hyperaccumulating ecotypes of Sedum plants are promising Cd/Zn phytoextractors, with potential for leveraging its rhizospheric or endophytic microbiomes to improve phytoremediation efficiency. However, research of bacteria associated with Sedum at field scale is still lacking. Here, we presented a detailed investigation of the bacterial microbiome of hyperaccumulating Sedum ecotypes (S. alfredii and S. plumbizincicola) and a non-hyperaccumulating S. alfredii ecotype, which grow at different soil environments. Moreover, we evaluated the heavy metal uptake and translocation potential of Sedum plants at different locations. The results showed that both HE ecotypes, contrary to the NHE, were efficient for phytoremediation in mine areas and farmlands. For NHE plants, rhizosphere co-occurrence networks were more complex than the networks of other compartments, while networks of HE plants were more complex in bulk soil and roots. The proportion of positive correlations within co-occurrence networks was higher for the HE plants, suggesting a greater potential for mutualistic interactions. Plant compartment and location predominantly shaped the microbiome assembly, and Proteobacteria, Actinobacteria and Acidobacteria dominated the bacterial communities of Sedum plants. Keystone taxa related to Zn hyperaccumulation are similar to those related to Cd hyperaccumulation, and nine bacterial genera had significantly positive correlation with Cd/Zn hyperaccumulation. Taxa, linked to phytoremediation in both mine and farmland (i.e. Actinospica and Streptomyces from Actinobacteria), could be targets for further investigation of their ability to promote metal phytoremediation of Sedum species.

Exploration of heavy metal uptake potential of three algal strains/consortia in suspended and attached growth systems

Three different algal strains/consortia; Chlorella pyrenoidosa (CP), consortium of Chlorella pyrenoidosa and Phormidium (PA6) and consortium from Hauz Khas lake (HL), were studied for their potential in heavy metals' bioremediation. Batch experiments (HRT-6 days) were performed in two different modes of algae cultivation systems; suspension and attached biofilms. The study aimed to highlight the suitability of an algal strain/consortium to different cultivation systems for metal removal and biomass production. The six commonly found heavy metals in wastewater; Cd, Cr, Pb, Cu, Ni and Zn, were used for the study. The selected algae were tested for its performance on individual and multiple metals contaminants. In individual metal spiked cultures (suspension), the common heavy metals that were uptaken efficiently by the three algal strains/consortia were Zn, Pb, Cu and Cd (>55%). Zn was uptaken >80% in all these test cultures. In mixed metal spiked suspension systems, all the metals were uptaken >60% by PA6 only. In mixed metal spiked attached systems, except for Cr, all other metals were uptaken efficiently by PA6 in the order Zn > Ni > Cd > Pb > Cu in the range of 78–98%. HL and CP performed best in suspension systems with individual metal spiking. PA6 performed better than HL and CP in mixed metal spiked media, especially in attached systems. The uptake of multiple metals from a variety of effluents can be done using PA6-like consortium (preferably in attached systems), whereas in effluents where only a single metal is present, CP/HL-like consortium can be used in suspended cultures.

Arsenic and mercury uptake and accumulation in oilseed sunflower accessions selected to mitigate co-contaminated soil coupled with oil and bioenergy production

Thirty-seven accessions of oilseed sunflower were evaluated under natural field conditions for growth performance, ligno-cellulosic mass production of bioenergy, and metal uptake potential during the remediation of arsenic and mercury-contaminated soil. Significant variations were observed in the ligno-cellulosic components of plant stems at maturity, decreasing the following order: total sugars > cellulose > hemicellulose > lignin > ash. A significant difference was also noted in metal uptake among the different accessions. The highest concentrations in the above-ground parts were 14.08 and 0.40 mg/kg, respectively for As and Hg. In rhizosphere soil concentrations of inorganic As species (arsenate: 69.73 mg/kg, arsenite: 4.41 mg/kg) were higher, as compared organic As (dimethyl arsenic: 0.22 mg/kg); mono-methyl arsenic: 0.02 mg/kg). Arsenate concentration (3.72 mg/kg) was higher in root, whereas arsenite concentration (0.47 mg/kg) was higher in the shoots. Many accessions showed good oil production (26–45.6%), with the highest percentage of oleic (75%) and linoleic acids (37.6%). These results suggest that some oilseed sunflower cultivars could be adopted as crop plants for effective remediation of lightly to moderately As-/Hg-contaminated soils, coupled with agro-production.

Differential Growth and Metal Accumulation Response of Brachiaria Mutica and Leptochloa Fusca on Cadmium and Lead Contaminated Soil

ABSTRACT This work aims to assess growth, physiology, and metal uptake response of Brachiaria mutica and Leptochloa fusca under different contamination levels of Cd (10 and 50 mg kg−1) and Pb (50 and 250 mg kg−1) stress. Results of pot trial showed increasing metal concentration affected B. mutica more as compared to L. fusca. In B. mutica metal stress substantially reduced shoot dry biomass, root dry biomass, total chlorophylls, and carotenoids contents by 89%, 85%, 65%, and 61%, respectively, while enhanced the SOD activity up to 62 U min−1 g−1 FW. L. fusca showed better growth, chlorophylls and carotenoid contents, SOD activity (up to 79 U min−1 g−1 FW), shoot metal uptake potential (Cd 110 µg pot−1, Pb 91.57 µg pot−1), and root metal concentration (Cd 126 mg kg−1 dm, Pb 117 mg kg−1 dm) compared to B. mutica under Pb and Cd stress. While both grass species showed metal translocation factor less than unity under all levels of metal stress. Keeping in view the above results, it is concluded that L. fusca having better growth and physiology with TF < 1 could be used for phytostabilization of Pb and Cd to reclaim the soil having moderate to lower levels of contamination.

Heavy metal accumulation and phytoremediation potential by transplants of the seagrass Zostera marina in the polluted bay systems.

Although seagrasses can incorporate heavy metals from the marine environment, few studies have been conducted on heavy metal uptake and phytoremediation potential by seagrass transplants in the heavy metal contaminated sediments. Zostera marina shoots were transplanted in two polluted bay systems on Korean coasts to evaluate the heavy metal contaminations in sediments and the possibility of using Z. marina transplants as a bioindicator and phytoremediation agent. The major concentrated metals in sediments were As, Cu, Fe, and Pb in Jaran Bay, and Cd, Co, Zn, and Hg in Onsan Bay. The Co, Zn, Pb, and Hg concentrations in Z. marina tissues reflected the sediment heavy metal concentrations, and thus the tissue heavy metal concentrations may be used as bio-indicators of the metal contaminations. Since Z. marina transplants accumulated a great amount of heavy metals in their tissues, they may have the phytoremediation potential for the heavy metal contaminated sediments.

EDTA-Assisted Metal Uptake in Raphanus sativus L. and Brassica oleracea L.: Assessment of Toxicity and Food Safety.

A study was conducted to determine the effect of ethylenediaminetetraacetic acid (EDTA) on phytoextraction potential of radish and cabbage. Plant biomass, photosynthetic pigments, proline and phenolics were significantly affected by the accumulation of heavy metals (HM). The metal uptake potential was increased significantly by the application of EDTA. Target hazard quotient (THQ) associated with exposure of these contaminants to food chain was calculated. Agronomic interventions to increase mineral levels in crops often increases the leaf concentrations only, the mineral concentration in edible portions are not increased at desired level due to low mobility of Zn in phloem. Since the leaves of both these crops are edible and a component of staple vegetarian diet, biofortification through Zn present in soil and its solubilization and mobilization through chelators can be implemented. However in no such instance these crops should be consumed when grown on Pb contaminated soil due to associated hazards.

Screening of most potential candidate among different lemongrass varieties for phytoremediation of tannery sludge contaminated sites

One of the most sustainable approaches for reclamation of heavy metal contaminated sites is by phytoremediation. Cultivation of aromatic plants in such areas has been proposed by a number of researchers as it fulfills the purpose of phytoremediation alongside monetary benefits. A pot experiment was conducted to screen out most potential candidate among different lemongrass varieties which can be recommended to be grown in tannery effluent contaminated sites. Four consecutive harvests of nine varieties of lemongrass were tested. Translocation factor (TF) < 1 for chromium and cadmium whereas >1 for nickel and lead was observed in all varieties. Bioconcentration factor (BF) > 1 was observed for chromium in Suwarna variety. Photosynthetic pigments, growth parameters, antioxidants, oil content, and yield were highly correlated. Neighbor joining (NJ) cluster analysis was performed to predict the relationship between varieties according to their chromium uptake potential. Endurance of varieties towards metal stress was assessed using chlorophyll a fluorescence kinetics. Maximum reduction potential of chromium (70.07%), lead (85.29%), and cadmium (77.36%) was observed in Suwarna variety. Our study indicated that lemongrass acts as potential phytoextractor for nickel and lead. Suwarna variety appeared to be the best candidate among all the varieties tested owing to its higher biomass and metal uptake potential.

Bio-composites for the sorption of copper from aqueous solution: A comparative study

Metal cleaning and plating baths, pulp, paper board mills, printed circuit board and wood pulp production, fertilizer industry etc. are releasing copper into the environment and seriously affecting the quality of drinking water. Even minute quantity of copper (1.3 ppm) in water is detrimental to biota. Therefore, abundantly available poultry and agricultural wastes are tested as adsorbents for the removal of copper leading to sustainable management of wastes and improving the quality of water. Sorption capacities of chitosan-Gallus domesticus eggshell, chitosan-Dromaius novaehollandiae eggshell (CH-GDES, CH-DNES) and chitosan-Dromaius novaehollandiae feather (CH-DNF) composites were first evaluated for copper removal from aqueous solution by ‘one variable at a time’ method, and further experiments were carried out by a three level full factorial design of Response Surface Methodology (RSM). The percent removal of copper by the composites increased with the increase in contact time and the kinetics best fitted to the pseudo - second order model. The optimum pH of the aqueous solution was found to be 6 for the removal of copper for all the three composites. The experimental data of initial metal ion concentration was fitted using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich adsorption isotherm models, and the better suited is Langmuir's isotherm model. Chitosan-Gallus domesticus eggshell composite showed the highest metal uptake potential of copper (qmax 56.49 mg/g). Thermodynamically, copper adsorption onto the bio-composites is inferred as spontaneous, irreversible and endothermic in nature. Characterization of the adsorbents by SEM-EDS, FTIR, XRD and BET, before and after adsorption of copper, revealed that the sorption is due to the mechanisms of chemisorption, ion exchange and/or complexation. The adsorbent pads/filters made of natural renewable biopolymer composites like CH-GDES/CH-DNES/CH-DNF, can be placed at the source to prevent bulk water pollution with copper and maintain the concentration well below the permissible limits in the ground water.

Metal uptake potential of four methylotrophic bacterial strains from coal mine spoil, exploring a new possible agent for bioremediation

Abstract The abundance of total metal tolerant culturable bacteria and methylotrophic bacteria was numerated in the barren mine spoil. Metal resistant methylotrophic bacteria were isolated and identified through biochemical testing and 16SrRNA gene sequence analysis. The metal uptake potential of the isolates was determined. The size of the methylotrophic bacteria was significantly low (104) compared to total bacterial population (108). The methylotrophic population was less tolerant to the tested metals viz., Cd, Cu, Cr, Ni and Zn. The metal resistant isolates showed close similarity with Pseudomonas, Methylophilus and Methylobacterium sp. Lower concentration (5–10 μ M) of al the tested metals was growth stimulatory. MIC values were lowest for Cd and highest for Zn. At the same time, MIC value was highest for Pseudomonas strain and lowest for Methylobacterium. Highest metal uptake was observed for Cd and lowest for Cr. Metal uptake potential varied with strain as well as metal species. There was no relation between the intracellular metal accumulation and metal adsorbed to the bacterial cell wall. Lowest adsorption capacity was exhibited by the Pseudomonas strain. Highest adsorption was for Cu and lowest for Ni. Metal uptake was rapid during first 4 h, and then after rate of uptake declined. It suggests that methylotrophic bacteria can be used as potential accumulator of Cd.

Differential distribution of metals in tree tissues growing on reclaimed coal mine overburden dumps, Jharia coal field (India).

Opencast bituminous coal mining invariably generates huge amount of metal-polluted waste rocks (stored as overburden (OB) dumps) and reclaimed by planting fast growing hardy tree species which accumulate metals in their tissues. In the present study, reclaimed OB dumps located in Jharia coal field (Jharkhand, India) were selected to assess the accumulation of selected metals (Pb, Zn, Mn, Cu and Co) in tissues (leaf, stem bark, stem wood, root bark and root wood) of two commonly planted tree species (Acacia auriculiformis A.Cunn. ex Benth. and Melia azedarach L.). In reclaimed mine soil (RMS), the concentrations of pseudo-total and available metals (DTPA-extractable) were found 182-498 and 196-1877% higher, respectively, than control soil (CS). The positive Spearman's correlation coefficients between pseudo-total concentration of Pb and Cu (r = 0.717; p < 0.05), Pb and Co (r = 0.650; p < 0.05), Zn and Mn (0.359), Cu and Co (r = 0.896; p < 0.01) suggested similar sources for Pb-Cu-Co and Mn-Zn. Among the five tree tissues considered, Pb selectively accumulated in root bark, stem bark and leaves; Zn and Mn in leaves; and Cu in root wood and stem wood. These results suggested metal accumulation to be "tissue-specific". The biological indices (BCF, TFleaf, TFstem bark and TFstem wood) indicated variation in metal uptake potential of different tree tissues. The study indicated that A. auriculiformis could be employed for Mn phytoextraction (BCF, TFleaf, TFstem bark and TFstem wood > 1). The applicability of both the trees in Cu phytostabilization (BCF > 1; TFleaf, TFstem bark and TFstem wood < 1) was suggested. The study enhanced knowledge about the selection of tree species for the phytoremediation of coal mine OB dumps and specific tree tissues for monitoring metal pollution.

Biodiversity variability and metal accumulation strategies in plants spontaneously inhibiting fly ash lagoon, India.

Out of 29 plant species taken into consideration for biodiversity investigations, the present study screened out Cyperus rotundus L., Calotropis procera (Aiton) W.T. Aiton, Croton bonplandianus Baill., Eclipta prostrata (L.) L., and Vernonia cinerea (L.) Less. as the most suitable metal-tolerant plant species (high relative density and frequency) which can grow on metal-laden fly ash (FA) lagoon. Total (aqua-regia), residual (HNO3) and plant available (CaCl2) metal concentrations were assessed for the clean-up of metal-contaminated FA disposal site using naturally colonized plants. The total metal concentration (in mg kg-1) in FA followed an order of Mn (229.8)>Ni (228.4)>Zn (89.4)>Cr (61.2)>Pb (56.6)>Cu (51.5)>Co (41.9)>Cd (9.7). The HNO3- and CaCl2-extracted metals were 0.57-15.68% and 0.03-7.82% of the total metal concentration, respectively. The concentration of Ni and Cr in FA in the present study was highest among the previously studied Indian and average world power plants and Cd, Ni, and Cr were above soil toxicity limit. The variation in total, residual, and plant-available metal (single extraction) concentration indicated the presence of different proportions of metals in FA lagoon which affects the metal uptake potential of the vegetation growing on it. It has been reported that plant-available metal extractant (CaCl2) is the most suitable extractant for assessment of metal transfer from soil to plant. However in the present study, Spearman's correlation showed best significant correlation between total metal concentration in FA and shoot metal concentration (r=0.840; p<0.01) which suggest aqua-regia as the best extractant for understanding the bioavailability and transfer of metal, and in calculation of BCF for moderately contaminated site. It can be stated that plant-available extractant is not always suitable for understanding the availability of metal, but total metal concentration can provide a better insight especially for moderate or low metal-contaminated sites. Principle component analysis revealed that all the plants showed positive correlation with Co and Cd which suggest its subsequent uptake in root and shoot. The biological indices (BCF, BAF, and TF) revealed that E. prostrata (10mg Cd kg-1) and C. procera (3.5mg Cd kg-1) can be utilized efficiently for the phytoextraction of Cd and phytostabilization of other potentially toxic metals (Pb, Cr, and Co) from FA lagoon. All the plants were tolerant to Pb pollution (TF>1, BAF>1, and BCF>1); hence, there was a negligible translocation of Pb to the aerial tissues of these plants which shows their suitability in phytostabilization. In addition, V. cinerea accumulated elevated concentration of potentially toxic Cr (50mg Cr kg-1) and Ni (67mg Ni kg-1) which could also help in the phytoremediation of FA lagoon.

Heavy Metal Uptake Potential of Aquatic Plants through Phytoremediation Technique - A Review

Bioremediation means using biological agents to clean environment. Heavy metal pollution being the core all over the word needs immediate attention so that our degrading environments will be remediated. Phytoremediation is an ecofriendly that has shown promising results for the contaminants like heavy metals. The basic fundamental elements in phytoremediation are plants whether terrestrial or aquatic which play key role for remediation of heavy metal affected environments. Phytoremediation has also been a solution for various emerging problems.

Metal phytoremediation potential of naturally growing plants on fly ash dumpsite of Patratu thermal power station, Jharkhand, India

ABSTRACTThree naturally growing plants Ipomoea carnea, Lantana camara, and Solanum surattense were found in fly ash dumpsite of Patratu thermal power station, Jharkhand, India. They were assessed for their metal uptake potential. The fly ash was slightly alkaline with very less nitrogen and organic carbon but enriched with phosphorus and heavy metals. Lantana camara and Ipomoea carnea showed good translocation from root to shoot for most of the metals except Mn and Pb. The order of metal accumulation in stem of both the plants were Fe(205mg/kg)>Mn(65mg/kg)>Cu(22.35mg/kg)>Pb(6.6mg/kg)>Cr(3.05mg/kg)>Ni(1 mg/kg)>Cd(0.5 mg/kg) and Fe(741 mg/kg)>Mn(154.05 mg/kg)>Cu(20.75 mg/kg)>Pb(6.75 mg/kg)>Ni(4.0 mg/kg)>Cr(3.3mg/kg)>Cd(0.05mg/kg), respectively. But Solanum surattense accumulated most of the metals in roots. The order was in the following order, Mn (382.2mg/kg) >Fe (264.1mg/kg) > Cu (25.35mg/kg) >Pb (5.95 mg/kg) > Ni (1.9 mg/kg) > Cr (1.8mg/kg) > Cd (0.55 mg/kg). The order of Bioconcentration factor (BCF) in root and shoot followed almost the same order as, Mn>Fe>Ni>Pb>Cu>Cr≈ Cd in all the three species. ANOVA showed significant variation in metal accumulation by root and stem between the species. Finally, it can be concluded that Solanum surattense can be used as phytostabilizer and other two species as phytoextractor of metal for fly ash dumpsite reclamation.

Metal uptake, antioxidant status and membrane potential in maize roots exposed to cadmium and nickel

Root growth of the seedlings of maize cultivars Premia and Blitz exposed to 2 μM cadmium (Cd), nickel (Ni) or both metals acting simultaneously (Cd + Ni) for 72 h was significantly reduced but not ceased. The effect was more pronounced in the seedlings of the cv. Blitz. The heavy metals (HMs) contents increased significantly in the roots. Simultaneous application of metals had an antagonistic effect on either Cd or Ni uptake in Premia but not in Blitz. In control roots the contents of ascorbic acid (AsA) and dehydroascorbic acid (DHA) were lower and gluthatione (GSH) content was higher in Premia than in Blitz. A decrease of AsA content was induced by all metal treatments in Premia but only by Cd + Ni in Blitz while an increase was induced by single metals in this cultivar. All metal treatments increased DHA contents in both cultivars. GSH content decreased significantly in Premia treated with Cd or Cd + Ni, and in Blitz treated with Ni. Unlike the contents of AsA, DHA and GSH, the increased metal concentrations in root cells did not affect the membrane potential (E M). The changes in antioxidant contents depended on both, maize genotypes and HMs treatments. Nevertheless, the results indicated a role of antioxidative system in minimizing the effects of oxidative stress and protecting cell membranes in both maize cultivars.

Uptake of certain heavy metals from contaminated soil by mushroom—Galerina vittiformis

Remediation of soil contaminated with heavy metals has received considerable attention in recent years. In this study, the heavy metal uptake potential of the mushroom, Galerina vittiformis, was studied in soil artificially contaminated with Cu (II), Cd (II), Cr (VI), Pb (II) and Zn (II) at concentrations of 50 and 100mg/kg. G. vittiformis was found to be effective in removing the metals from soil within 30 days. The bioaccumulation factor (BAF) for both mycelia and fruiting bodies with respect to these heavy metals at 50mg/kg concentrations were found to be greater than one, indicating hyper accumulating nature by the mushroom. The metal removal rates by G. vittiformis was analyzed using different kinetic rate constants and found to follow the second order kinetic rate equation except for Cd (II), which followed the first order rate kinetics.

Sustainable Sources of Biomass for Bioremediation of Heavy Metals in Waste Water Derived from Coal-Fired Power Generation

Biosorption of heavy metals using dried algal biomass has been extensively described but rarely implemented. We contend this is because available algal biomass is a valuable product with a ready market. Therefore, we considered an alternative and practical approach to algal bioremediation in which algae were cultured directly in the waste water stream. We cultured three species of algae with and without nutrient addition in water that was contaminated with heavy metals from an Ash Dam associated with coal-fired power generation and tested metal uptake and bioremediation potential. All species achieved high concentrations of heavy metals (to 8% dry mass). Two key elements, V and As, reached concentrations in the biomass of 1543 mg.kg−1 DW and 137 mg.kg−1 DW. Growth rates were reduced by more than half in neat Ash Dam water than when nutrients were supplied in excess. Growth rate and bioconcentration were positively correlated for most elements, but some elements (e.g. Cd, Zn) were concentrated more when growth rates were lower, indicating the potential to tailor bioremediation depending on the pollutant. The cosmopolitan nature of the macroalgae studied, and their ability to grow and concentrate a suite of heavy metals from industrial wastes, highlights a clear benefit in the practical application of waste water bioremediation.

Organic and metallic pollutants in water treatment and natural wetlands: a review

A literature review shows that more than 500 compounds occur in wetlands, and also that wetlands are suitable for removing these compounds. There are, however, obvious pitfalls for treatment wetlands, the most important being the maintenance of the hydraulic capacity and the detention time. Treatment wetlands should have an adapted design to target specific compounds. Aquatic plants and soils are suitable for wastewater treatment with a high capacity of removing nutrients and other substances through uptake, sorption and microbiological degradation. The heavy metals Cd, Cu, Fe, Ni and Pb were found to exceed limit values. The studies revealed high values of phenol and SO(4). No samples showed concentrations in sediments exceeding limit values, but fish samples showed concentrations of Hg exceeding the limit for fish sold in the European Union (EU). The main route of metal uptake in aquatic plants was through the roots in emergent and surface floating plants, whereas in submerged plants roots and leaves take part in removing heavy metals and nutrients. Submerged rooted plants have metal uptake potential from water as well as sediments, whereas rootless plants extracted metals rapidly only from water. Caution is needed about the use of SSF CWs (subsurface flow constructed wetlands) for the treatment of metal-contaminated industrial wastewater as metals are shifted to another environmental compartment, and stable redox conditions are required to ensure long-term efficiency. Mercury is one of the most toxic heavy metals and wetlands have been shown to be a source of methylmercury. Methyl Hg concentrations are typically approximately 15% of Hgt (total mercury). In wetlands polycyclic aromatic hydrocarbons (PAH), bisphenol A, BTEX, hydrocarbons including diesel range organics, glycol, dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCB), cyanide, benzene, chlorophenols and formaldehyde were found to exceed limit values. In sediments only PAH and PCB were found exceeding limit values. The pesticides found above limit values were atrazine, simazine, terbutylazine, metolachlor, mecoprop, endosulfan, chlorfenvinphos and diuron. There are few water quality limit values of these compounds, except for some well-known endocrine disrupters such as nonylphenol, phtalates, etc.