Toxic Chromium Research Articles

Heavy Metal Contamination of Soil and Health Hazards Among the Residents of Tannery Industrial Area

Background: Heavy metals like chromium compounds can be carcinogenic usually used in the tanning process during leather production. Chromium is an important health risk factor for the tannery workers which may enter the body by inhalation, ingestion and by direct cutaneous contact and cause several health problems of skin and respiratory tract. With the increase of unplanned industries, Bangladesh poses a new challenge to combat health hazards associated with heavy metal toxicity in soil.Objective: The present study was designed to find out possible toxic effects of heavy metals in soil and health hazards among the people residing at tannery industries area.Materials and Methods: This is a descriptive cross-sectional study and was carried out in two phases during the period of 1st November 2009 to 30 June 2010. In first phase the soil samples were taken from lagoons of Hazaribagh Thana of Dhaka city for laboratory test of heavy metals. In second phase, a total 190 respondents were interviewed using a semi-structured questionnaire to ascertain the common health problem around the tannery industries.Results: All the eight soil samples contained Cr, Mn, Ni, Fe, Pb, Cu, where as Cd was nil. Mean distributor of Cr, Mn, Ni, Fe, Pb and Cu was 43.1325, 354.2217, 28.6633, 22420.1867, 97.5833 and 53.4633 ppm respectively. 75.26% respondents stayed in the study area for six to ten years. Most of the respondents (75) were tannery workers. Total 52.85% households had toxicity related sickness in last six months. Among tannery workers most prevalent sickness were conjunctivitis (7.7%) and Dermatitis (6.7%). Regarding occurrence of clinical manifestations similar to Chromium toxicity in relation to staying in the study area, most of the households complained about allergy (39.2%) and abdominal discomfort (24.4%).Conclusion: Elevated levels of urinary and blood Chromium is associated with high morbidity among the tannery workers. Therefore bio-monitoring of the heavy metals in the exposed workers is considered as a useful tool.Anwer Khan Modern Medical College Journal Vol. 9, No. 1: Jan 2018, P 39-43

Ploidy level of citrus rootstocks affects the carbon and nitrogen metabolism in the leaves of Chromium-stressed Kinnow mandarin plants

This study compared the effects of chromium toxicity on the carbon and nitrogen metabolism in Kinnow mandarin (Citrus nobilis Lour x Citrus deliciosa Ten) plants grafted on the diploid (2x) and tetraploid (4x) of Poncirus trifoliata [L.], Citrus reshni, and Citrus limonia Osbeck. Plants were grown under controlled conditions and fertigated with complete nutrient solution supplemented with chromium (0.75 mM). After 120-d of growth under chromium (Cr) stress, carbon (C) and nitrogen (N) metabolism in leaves were studied. In the C metabolism study sucrose, glucose, fructose, starch contents, and the enzymatic activities of acid invertase (AI), neutral invertase (NI), sucrose synthetase (SS), sucrose phosphatesynthetase (SPS), fructokinase (FK), hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK) were investigated. Nitrogen metabolism study was comprised of determination of nitrate, nitrite and ammonium content and the nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthetase (GOGAT), and glutamate dehydrogenase (GDH) activities. Basically, in the C metabolism study the Cr enhanced the enzymatic activities and sugar contents, and decreased starch. Chromium stress caused a decrease in nitrate and nitrite, and an increase in ammonia; it also inhibited all measured enzymatic activities except GDH which was increased. The responses of Kinnow mandarin plants grafted on 2x or 4x for any rootstock followed a similar pattern, although the effects of Cr toxicity were more drastic in 2x grafted plants. Glycolysis was the only metabolic process which had a different behavior between 2x and 4x grafted plants under Cr stress: FK and HK activities under Cr stress were significantly increased in 4x grafted plants than in 2x grafted plants. These data suggest that in Kinnow mandarin plants grafted on 4x rootstocks the C metabolism is modified thereby strengthening the plants to adapt Cr stress, but N metabolism was inhibited by Cr toxicity.

Chromium(VI) Toxicity in Legume Plants: Modulation Effects of Rhizobial Symbiosis.

Most legume species have the ability to establish a symbiotic relationship with soil nitrogen-fixing rhizobacteria that promote plant growth and productivity. There is an increasing evidence of reactive oxygen species (ROS) important role in formation of legume-rhizobium symbiosis and nodule functioning. Environmental pollutants such as chromium compounds can cause damage to rhizobia, legumes, and their symbiosis. In plants, toxic effects of chromium(VI) compounds are associated with the increased production of ROS and oxidative stress development as well as with inhibition of pigment synthesis and modification of virtually all cellular components. These metabolic changes result in inhibition of seed germination and seedling development as well as reduction of plant biomass and crop yield. However, if plants establish symbiosis with rhizobia, heavy metals are accumulated preferentially in nodules decreasing the toxicity of metals to the host plant. This review summarizes data on toxic effects of chromium on legume plants and legume-rhizobium symbiosis. In addition, we discussed the role of oxidative stress in both chromium toxicity and formation of rhizobial symbiosis and use of nodule bacteria for minimizing toxic effects of chromium on plants.

Further Insight into the Formation and Oxidation of CaCr2O4 during Solid Fuel Combustion.

The control of toxic chromate (Cr6+) formation is still a significant challenge in solid fuel combustion. In particular, the mechanism of chromium transformation from Cr3+ to chromate or other unoxidized forms remains unclear. The present study confirms the formation of a significant unoxidized Cr-containing compound CaCr2O4(Cr3+) during solid fuel combustion. Experiments were conducted, for the first time, to clarify the mechanism of CaCr2O4 oxidation, which is quite different from Cr2O3 oxidation. The findings demonstrate that CaCr2O4 was formed at temperatures above 1200 K, through rapid decomposition of CaCrO4 or slow and direct interaction between CaO and Cr2O3. Compared to Cr2O3, CaCr2O4 could be oxidized at lower temperatures under the influence of free CaO. In the absence of free CaO, the oxidation of CaCr2O4 was minimal; however, in the presence of CaSO4, calcium in the form of CaCr2O4 participated in the oxidation of CaCr2O4. Thus, chromium in the form of CaCr2O4 was more likely to be oxidized when CaCr2O4-containing fly ash was reheated. Fortunately, CaCr2O4 showed slight basicity on the surface, allowing it to react with acidic gases. Accordingly, measures were proposed to suppress the oxidation of CaCr2O4 by stimulating the reactions between CaCr2O4 and acidic substances, like SO2 and Si/Al-compounds. These compounds competed with chromium at high temperatures to react with calcium in the fly ash and in CaCr2O4. As a result, the unoxidized chromium was transformed into highly stable Cr2O3 or Ca3Cr2 (SiO4)3.

Bioactive profiling and therapeutic potential of mushroom (Pleurotus tuberregium) extract on Wistar albino rats (Ratus norvegicus) exposed to arsenic and chromium toxicity.

Mushroom species are valued in gourmet traditions around the world for their unique taste, aroma, nutritional value and medicinal potentials. The bioactive profiling of P. tuberregium mushroom was evaluated to determine it therapeutic effect on Wistar albino rats exposed to arsenic (As) and chromium (Cr) toxicity. Proximate analysis of P. tuberregium showed high composition of carbohydrate (80.24) followed by moisture (21.16), protein (11.46), ash (3.03) and fibre (0.25) content. Phytochemical analysis revealed the presence of polyphenols (2.58), alkaloid (2.46), oxalate (4.25), flavonoid (1.68), tannin (0.38) and Saponin (trace) in trace amount. Mineral analysis yielded variable amounts of Na, Mg, K and Ca. Therapeutics assessment of P. tuberregium to Wistar albino rats exposed to As-Cr toxicity showed improved feed and water intake during the exposure duration. Haematological indices revealed significant increase in platelet (PLT), granulocytes and monocytes while lymphocyte (LY) and red cell distribution width (RDW) were low. Biochemical and redox marker of liver and kidney profiles showed decrease in alkaline phosphatase (ALP), alanine transaminase (ALT) and aspartate transaminase (AST) in the liver. Creatinine and urea in the kidney also decrease while total protein increased significantly. Malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), glutathione S-transferase (GST) decrease in the liver and kidney of the therapeutic group when compared with As-Cr treated rats. The presence of alkaloids and flavonoids in significant amount may have contributed in the therapeutic changes observed in all the parameters. Therefore, our findings conclude that P. tuberregium possessed remarkable effect against As-Cr induced toxicity in albino rats and may be useful in metal toxicity treatment in man and may be concluded that they are therapeutically effective.

Structure-enhanced removal of Cr(vi) in aqueous solutions using MoS2 ultrathin nanosheets

Molybdenum disulfide (MoS2) ultrathin nanosheets with enlarged interlayer spacing and defects enables the structure-enhanced removal of Cr(vi), in which the synergistic effects of adsorption and reduction not only captured Cr(vi) from aqueous solutions, but also alleviated the toxicity of chromium to some degree.

Protective role of selenium against chromium stress involving metabolites and essential elements in Brassica juncea L. seedlings.

The present study aimed at the potential role of selenium in providing protection to plants subjected to chromium toxicity. The study was carried out on 15-day-old seedlings of Brassica juncea raised in the solutions of Cr (300µM) and Se (2, 4 and 6µM), both alone and in combinations under controlled laboratory environment. The effects were studied on growth, plant metabolites (involved in osmotic homeostasis and stress protection), and essential elements. The results showed that the exposure of B. juncea seedlings to 300µM Cr led to an increase in the contents of total sugars, reducing sugars, non-reducing sugars, total phenols and flavonoids. However, a significant decline in growth characteristics, the contents of proteins and free amino acids was observed. The essential elements (Na, K, Ca, Mg, C, H, N) also decreased in response to Cr. Se application in binary combinations, on the other hand, aided in improving seed germination (19%), root (88.3%) and shoot (18.2%) lengths. It also helped to increase the contents of sugars [total (16.3%), reducing (21.6%) and non-reducing (15.2%)], phenols (36.7%) and flavonoids (27.4%), thereby aiding in alleviating the phytotoxicity of Cr. The profiling of polyphenols and amino acids, and histological study of phenols supported the above results. The contents of essential elements also showed a significant increase, while Cr uptake was observed to decline by Se supplementation. The observations from the present study indicate that Se has the ability to influence primary and secondary metabolism, improve mineral nutrition and reduce Cr uptake in B. juncea seedlings to combat the Cr phytotoxicity and enhance the tolerance against stress.

A comprehensive review on chromium induced alterations in fresh water fishes.

Chromium is considered as one of the most common ubiquitous pollutants in the aquatic environment, but the pure metallic form is absent naturally. There are three oxidation states in case of Chromium viz., Cr (II), Cr (III), Cr (VI). Among which Cr (II) is most unstable. Cr (III) and Cr (VI) are the stable oxidation state of Chromium in the environment. Being one of the commonly used metals Chromium and its particulates enter the aquatic medium through effluents discharged from different industries like textiles, tanneries, electroplating workshops, ore mining, dyeing, printing-photographic and medical industries. Among these, hexavalent chromium is considered as the most toxic form because it readily passes cellular membranes and then reduced to trivalent form. This trivalent chromium combines with several macromolecules including genetic material inside the cytosol, and is ultimately exposes the toxic and mutagenic alterations due of chromium toxicity. Chromium is taken up either through gastrointestinal tract or respiratory tract. The amount varies depending upon the medium and the form of chromium. In this review, an attempt has been made to accumulate the mammoth available data regarding impact of chromium on fresh water fishes into a systematic representation. The main objective of the review is to provide a future guideline for the scientific community and public officials involved in health risk assessment and management ensuring a better environmental condition for human health.

Hexavalent chromium induces testicular dysfunction in small Indian mongoose (Herpestes javanicus) inhabiting tanneries area of Kasur District, Pakistan

Hexavalent chromium (Cr-VI) is widely used in tanning industries, however, being highly toxic metal, its accumulation in the animal body can adversely affect reproductive functioning. If directly discharged untreated into the environment (adjoining nullahs and soil), it can contaminate the environment. Resultantly, along with human, inhabiting wildlife species get exposed to chromium toxicity, which may enter into the animal body through drinking water and food chain. The current study investigated toxic effects of Cr (VI) on testicular functioning of adult male small Indian mongooses inhabiting the tannery area of Kasur district, Pakistan. Soil, water and animal specimens were sampled from study area on monthly basis from February 2015 to January 2016. The captured mongooses were sacrificed to collect blood and body tissues (liver, kidneys and testes) samples. The concentrations of chromium in the samples were quantified using atomic absorption spectrophotometry. Hormonal concentrations were estimated using ELISA kits. The cellular changes occurring in the testicular tissues were studied through light microscopy. Average Cr-concentrations were found significantly higher in experimental area soil and water samples, and in the blood and body tissues of the mongooses compared to control, while body and testicular weights of experimental animals were found reduced. Serum testosterone (p = 0.037) and luteinizing hormone (p = 0.000) levels were found significantly lowered while follicle stimulating hormone (p = 0.000) levels significantly increased in experimental animals. Histological analysis revealed disorganization of seminiferous tubules, and apparently decreased numbers of Sertoli and the Leydig cells. Spermatozoa and seminiferous tubular counts were also found significantly (p = 0.000) reduced compared to control. Interstitial spaces were found widened. The study concludes that Cr from tanneries environment is up taken by mongooses leading to testicular tissue damage and potential impairment of reproductive functioning of the species.

Modulation of hexavalent chromium toxicity on Οriganum vulgare in an acidic soil amended with peat, lime, and zeolite

Dynamics of chromate (Cr(VI)) in contaminated soils may be modulated by decreasing its phytoavailability via the addition of organic matter-rich amendments, which might accelerate Cr(VI) reduction to inert chromite (Cr(III)) or high-cation exchange capacity amendments. We studied Cr(VI) phytoavailability of oregano in a Cr(VI)-spiked acidic soil non-treated (S) and treated with peat (SP), lime (SL), and zeolite (SZ). The addition of Cr(VI) increased the concentrations of Cr(VI) and Cr(III) in soils and plants, especially in the lime-amended soil. The plant biomass decreased in the lime-amended soil compared to the un-spiked soil (control) due to decreased plant phosphorus concentrations and high Cr(VI) concentrations in root at that treatment. Oregano in the peat-amended soil exhibited significantly less toxic effects, due to the role of organic matter in reducing toxic Cr(VI) to Cr(III) and boosted plant vigour in this treatment. In the lime-amended soil, the parameters of soil Cr(VI), soil Cr(III), and root Cr(III) increased significantly compared to the non-amended soil, indicating that Cr(VI) reduction to Cr(III) was accelerated at high pH. Added zeolite failed to decreased Cr(VI) level to soil and plant. Oregano achieved a total uptake of Cr(III) and Cr(VI) of 0.275 mg in plant kg−1 soil in a pot in the non-amended soil. We conclude that peat as soil amendment might be considered as a suitable option for decreasing Cr(VI) toxicity in soil and plant, and that oregano as tolerant plant species has a certain potential to be used as a Cr accumulator.

Impact of plant-associated bacteria biosensors on plant growth in the presence of hexavalent chromium.

Cr(VI) is a highly toxic metal produced by anthropogenic activity which may impact the environment, affecting plants and animals. In plants, chromium both as Cr(III) or Cr(VI) can be absorbed by roots, is poorly translocated and affects negatively plant growth. Plants used in phytoremediation need to cope with chromium toxicity. This work aimed to evaluate strains of Ochrobactrum tritici and Nitrospirillum amazonense, resistant and modified in order to become chromate whole-cell biosensors, as plant-protectors enabling plants to withstand contaminated soils. In vitro tests were performed in three rice varieties and one maize variety. Initial evaluations of Cr(VI) toxicity to plants showed that plants had different sensitivities and BRS 6 CHUÍ rice variety was the most resistant. The metal affected plant growth and development, essentially in roots which were totally inhibited in rice varieties at 500μM. This effect was plant-dependent. Modified N. amazonense proved to protect maize plants independently of the inoculation dose but O. tritici showed plant specificity and some toxicity when inoculated at high numbers, inhibiting rice development but not maize. Inoculants were directly responsible for growth improvements of specific plant varieties at 1.25ppm Cr(VI), a concentration which corresponds to a weak soil contamination. Improvements were observed relatively to the Cr(VI)-treated controls, but also relative to the untreated controls, i.e., the benefits went beyond a simple neutralization of inhibition brought by Cr(VI) toxicity.

Impact of chromium toxicity on water, plankton and bed sediments of River Ravi, Pakistan

Impact of chromium toxicity on water, plankton and bed sediments of River Ravi, Pakistan

The MOF+ Technique: A Significant Synergic Effect Enables High Performance Chromate Removal

AbstractA significant synergic effect between a metal–organic framework (MOF) and Fe2SO4, the so‐called MOF+ technique, is exploited for the first time to remove toxic chromate from aqueous solutions. The results show that relative to the pristine MOF samples (no detectable chromate removal), the MOF+ method enables super performance, giving a 796 Cr mg g−1 adsorption capacity. The value is almost eight‐fold higher than the best value of established MOF adsorbents, and the highest value of all reported porous adsorbents for such use. The adsorption mechanism, unlike the anion‐exchange process that dominates chromate removal in all other MOF adsorbents, as unveiled by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), is due to the surface formation of Fe0.75Cr0.25(OH)3 nanospheres on the MOF samples.

The MOF+ Technique: A Significant Synergic Effect Enables High Performance Chromate Removal.

A significant synergic effect between a metal-organic framework (MOF) and Fe2 SO4 , the so-called MOF+ technique, is exploited for the first time to remove toxic chromate from aqueous solutions. The results show that relative to the pristine MOF samples (no detectable chromate removal), the MOF+ method enables super performance, giving a 796 Cr mg g-1 adsorption capacity. The value is almost eight-fold higher than the best value of established MOF adsorbents, and the highest value of all reported porous adsorbents for such use. The adsorption mechanism, unlike the anion-exchange process that dominates chromate removal in all other MOF adsorbents, as unveiled by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), is due to the surface formation of Fe0.75 Cr0.25 (OH)3 nanospheres on the MOF samples.

An in situ study of growth of Lemongrass Cymbopogon flexuosus (Nees ex Steud.) W. Watson on varying concentration of Chromium (Cr+6) on soil and its bioaccumulation: Perspectives on phytoremediation potential and phytostabilisation of chromium toxicity

Chromium (Cr) contamination in soil is a growing concern in sustainable agricultural production and food safety. Remediation of Cr from contaminated soils is a challenging task which may not only help in sustaining agriculture but also in minimizing adverse environmental impacts. Pot culture experiments were performed with the application of varied concentration of Cr+6 to assess the Chromium accumulation potential of Lemongrass and to study the impact of toxic concentration of Cr+6 on morphological, physiological and biochemical parameters of the plant. The results showed an increasing accumulation trend of Chromium with increasing Chromium concentrations in both root and shoot of 60 days old Lemongrass plants, while the protein and chlorophyll contents decreased. Similarly, accumulation of Cr increased the levels of proline and antioxidant enzymes indicating the enhanced damage control activity. The potentiality of the plant with the capacity to accumulate and stabilize Cr compound in Cr contaminated soil by phytoremediation process has been explored in the present investigation.

Identification of genome-wide single-nucleotide polymorphisms (SNPs) associated with tolerance to chromium toxicity in spring wheat (Triticum aestivum L.)

Chromium (Cr) toxicity is a rapidly increasing environmental concern and poses a major threat to plant growth as well as food chain. This study was carried out to screen spring wheat diversity panel against Cr toxicity to assess yield reduction, grain contamination extents and genomic regions associated with tolerance to Cr toxicity. The diversity panel was planted in control and Cr stress (26 mg Cr/kg soil) in paved plots, and several morphological and physiological traits were recorded. Wheat 90 K Infinium iSelect SNP array was used to identify genomic regions underpinning tolerance to Cr toxicity. Some wheat cultivars (Khosar-95, Miraj-08, Millet-11, Sarsabaz and NARC-11) had Cr concentration within international edible threshold limit (1 ppm), but showed greater reduction to grain yield (63–95%) due to higher leaf Cr concentrations (2.35–8.95 ppm). Contrastingly, wheat cultivars Auqab-00 and Pakistan-13 had lower yield reduction up to 9% and 39%, respectively but had higher concentration of Cr in seeds (2.1 and 3.5 ppm, respectively). Genome-wide association studies identified 71 loci linked with yield related traits under Cr stress and 48 loci for differences between control and Cr stress treatments. Further, gene ontology of trait-associated SNPs revealed proteins with significant importance in plant development and tolerance against heavy metal stress. To our knowledge, this is the first study for identification of genomic regions linked to Cr stress, suggesting that this could be useful to identify complex architecture of genetic factors as well as molecular breeding opportunities for tolerance to Cr stress.

Integrated tannery wastewater treatment for effluent reuse for irrigation: Encouraging water efficiency and sustainable development in developing countries

Due to the high conductivity and chromium toxicity of tannery effluents, wastewater reuse can be possible only by implementing integrated process of sustainable wastewater treatments. The objective of the present study was to evaluate the suitability of treated tannery effluent for vegetable growth. An integrated treatment technology [hydrolysis-anaerobic-Sequence Batch Reactor (SBR) integrated with a constructed wetland] was used to treat tannery wastewater. Randomized block design for field and pot experiment was used for vegetable growth. Treated effluent, soil and vegetable samples were analyzed for nutrient, physicochemical, Cr and microbial parameters using standard methods (APHA). The removal efficiency of the innovative integrated treatment system ranges from 82 to 99.9%. The treated effluent concentrations for BOD, COD, TN, NO3–N, and NH3–N were 56 ± 18, 170 ± 26, 50 ± 13, 22.75 ± 20 and 7.1 ± 6 mg/L, respectively. Similarly, the concentration of EC, S2−, SO42− and Cl− were 2.23 ± 0.17 mS/cm, 0.4 ± 0.4, 88 ± 42 and 450 ± 150 mg/L, respectively; with a 99.9% TCF removal. The effluent meets the permissible discharge limits; possibly reuse for irrigation. Cr was found to accumulate the most in all vegetable samples and significantly higher in the field than pot treatments. Cr, Cd, Pb and Ni concentrations in all the pot experiment were found below the FAO/WHO guidelines. The target hazard quotients (THQs) estimation suggests that Cr concentration in all the pot treatment vegetable has no potential health risk.

Uniform Pt@Pd nanocrystals supported on N-doped reduced graphene oxide as catalysts for effective reduction of highly toxic chromium(VI)

In this work, we developed a facile one-pot co-reduction method for fabrication of spherical porous Pt@ultra-thin Pd skin core-shell nanocrystals supported on N-doped reduced graphene oxide (Pt@Pd NCs/N-rGO). Trajenta (Tra), a kind of dipeptidyl peptidase-4 inhibitors for treatment of diabetes, served as a new structure-directing agent for Pt@Pd NCs and N-doping resource for rGO via π-π stacking interactions. The product was mainly characterized by microscopic analysis, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetry (TGA), Raman and Fourier transform infrared (FT-IR) spectroscopy, and the formation mechanism was discussed in some detail. By taking formic acid as the reductant, the Pt@Pd NCs/N-rGO nanocomposite showed significantly enhanced catalytic ability and improved repeatability for the reduction of highly toxic hexavalent chromium (Cr(VI)) compared with commercial Pt/C (20 wt%) and Pd/C (20 wt%).

Adsorption of hexavalent chromium from aqueous solutions using Canadian peat and coconut fiber

Chromium compounds widely used in chemical processes are one of the biggest hazardous pollutants in industry effluents. The aim of the research is to investigate the role of the organic matter - Canadian Peat and coconut fiber in the removal processes of toxic chromium compounds from aqueous solutions. Characterization of organic matter has been carried out using scanning electron microscope with EDS, X-ray diffraction, Fourier transform infrared spectroscopy and BET measurements in order to analyze the surface and the porosity of the materials. In the study different concentrations of Cr have been investigated on the adsorption process and it has been found that maximum removal approximately 94% for coconut fiber and 91% for Canadian peat can be achieved in the lowest concentration equal to 25mg/dm3 after 72h. Langmuir, Freundlich and Temkin adsorption isotherm models have been used in order to describe the sorption parameters using the experimental data. Pseudo first, second order and Webber-Morris kinetics models have been verified to check the nature (chemical, physical) of Cr(VI) sorption on the materials. It has been found that pseudo-second order is the best fit for the adsorption what suggest that the process is of chemical nature. Regeneration of organic matter has been carried out by washing it with different eluents. Sodium citrate has the highest degree of chromium ions elution (53–65%). The removal efficiency was maintained for both materials after the elution process. Obtained results show that both organic materials can be effectively used for the removal of toxic chromium compounds from the aqueous solutions.

Analysis of chromium status in the revegetated flora of a tannery waste site and microcosm studies using earthworm E. fetida.

Chromium from tannery waste dump site causes significant environmental pollution affecting surrounding flora and fauna. The primary aims of this study were to survey vegetation, investigate the degree of soil pollution occurring near tannery waste dump site and make a systematic evaluation of soil contamination based on the chromium levels found in plants and earthworms from the impacted areas. This paper presents the pollution load of toxic heavy metals, and especially chromium, in 10 soil samples and 12 species of plants. Soil samples were analysed for heavy metals by using ICP-MS/ICP-OES method. Results indicated that Cr in soils exceeded soil quality guideline limits (SQGL). The total chromium present in the above ground parts of plants ranged from 1.7mgkg-1 in Casuarina sp.to 1007mgkg-1 in Sonchus asper. The Cr bioaccumulation in Eisenia fetida from tannery waste soil ranged from 5 to 194mgkg-1. The high enrichment factor of Cr in S. asper and bioaccumulation factor in earthworms indicate that there is a steady increase of toxic chromium risk in this area, which could be correlated with the past dumping activity. Emphasis needs to be put on control measures of pollution and remediation techniques in such areas to achieve an ecologically sustainable industrialisation.