Combined application of arbuscular mycorrhizal fungi and steel slag improves plant growth and reduces Cd,Pb accumulation in Zea mays

Abstract

Little attention has been paid to the combined use of arbuscular mycorrhizal fungus (AMF) and steel slag (SS) for ameliorating heavy metal polluted soils. A greenhouse pot experiment was conducted to study the effects of SS and AMF?Funneliformis mosseae (Fm), Glomus versiforme (Gv) and Rhizophagus intraradices (Ri) on plant growth and Cd, Pb uptake by maize grown in soils added with 5?mg Cd kg^?1 and 300?mg Pb kg^?1 soil. The combined usage of AMF and SS (AMF?+?SS) promoted maize growth, and Gv?+?SS had the most obvious effect. Meanwhile, single SS addition and AMF?+?SS decreased Cd, Pb concentrations in maize, and the greater reductions were found in combined utilization, and the lowest Cd, Pb concentrations of maize appeared in Gv?+?SS. Single SS amendment and AMF?+?SS enhanced soil pH and decreased soil diethylenetriaminepentaacetic acid (DTPA)-extractable Cd, Pb concentrations. Furthermore, alone and combined usage of AMF and SS increased contents of soil total glomalin. Our research indicated a synergistic effect between AMF and SS on enhancing plant growth and reducing Cd, Pb accumulation in maize, and Gv?+?SS exerted the most pronounced effect. This work suggests that AMF inoculation in combination with SS addition may be a potential method for not only phytostabilization of Pb-Cd-contaminated soil but maize safety production.     

Effects of arbuscular mycorrhizal fungi on the growth and heavy metal accumulation of bermudagrass [Cynodon dactylon (L.) Pers.] grown in a lead–zinc mine wasteland

Abstract

A pot experiment was conducted to investigate the potential influence of arbuscular mycorrhizal fungi (AMF), Funneliformis mosseae and Diversispora spurcum, on the growth and nutrient (P and S) and heavy metal (HMs) (Pb, Zn, and Cd) content of bermudagrass [Cynodon dactylon (L.) Pers.] in a lead-zinc mine wasteland. The D. spurcum inoculation significantly increased the bermudagrass growth, whereas the F. mosseae inoculation did not. The AMF inoculation significantly increased the soil pH and uptake of P, S, and HMs by bermudagrass, decreased the contents of available Pb and Zn in soils and Pb in shoots, reduced the translocation factor (TF) and translocation capacity factor (TF') of Pb and Cd in bermudagrass and increased the TF and TF' of Zn in bermudagrass. A significant negative correlation was found between pH and available HMs in soil, whereas a significant positive correlation was noted between the HMs content and nutrient content in bermudagrass shoots. Experiment results provide evidence of the potential role of AMF in improving bermudagrass performance for the vegetation restoration of metalliferous mine wastelands.     

Accumulation of Trace Metals by Mangrove Plants in Indian Sundarban Wetland: Prospects for Phytoremediation

The work investigates on the potential of ten mangrove species for absorption, accumulation and partitioning of trace metal(loid)s in individual plant tissues (leaves, bark and root/pneumatophore) at two study sites of Indian Sundarban Wetland. The metal(loid) concentration in host sediments and their geochemical characteristics were also considered. Mangrove sediments showed unique potential in many- fold increase for most metal(loid)s than plant tissues due to their inherent physicochemical properties. The ranges of concentration of trace metal(loid)s for As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn in plant tissue were 0.006–0.31, 0.02–2.97, 0.10–4.80, 0.13–6.49, 4.46–48.30, 9.2–938.1, 0.02–0.13, 9.8–1726, 11–5.41, 0.04–7.64, 3.81–52.20 μg g ^?1respectively. The bio- concentration factor (BCF) showed its maximum value (15.5) in Excoecaria agallocha for Cd, suggesting that it can be considered as a high-efficient plant for heavy metal bioaccumulation. Among all metals, Cd and Zn were highly bioaccumulated in E. agallocha (2.97 and 52.2 μg g ^?1 respectively. Our findings suggest that the species may be classified as efficient metal trap for Cd in aerial parts, as indicated by higher metal accumulation in the leaves combined with BCF and translocation factor (TF) values.     

Biochemical and RAPD Analysis of Hibiscus rosa sinensis Induced by Heavy Metals

The present study was designed to assess the effects of three different metals (cadmium, lead, and zinc) at the same concentrations on Hibiscus rosa sinensis during metal uptake. The effects of different metals at the same concentrations were assessed on biomass, root-shoot length, and biochemical parameters like chlorophyll and antioxidant enzymes like SOD and CAT to establish the tolerance potential and toxic effects on plants in different metals. The accumulation of metals by plants was found to be in the following order: Zn > mixed metals > Cd > Pb, where Zn was accumulated approximately 79.6% in plant tissues. Plants removed from Cd showed more enzyme activities than the other two metals. DNA stability was investigated by a Random Amplified Polymorphic DNA (RAPD) technique, which demonstrated that the samples in Cd and mixed metal showed similar trends, whereas samples in Zn and Pb showed similar band intensity to the control. Results suggested that Cd and/or heavy metal stress influences antioxidant status and also induces DNA changes during remediation. Therefore, these studies could be a useful biomarker assay for better treatment for metals’ remediation from soil by means of phytoremediation.     

Jatropha curcas and assisted phytoremediation of a mine tailing with biochar and a mycorrhizal fungus

Soil pollution is an important ecological problem worldwide. Phytoremediation is an environmental-friendly option for reducing metal pollution. A greenhouse experiment was conducted to determine the growth and physiological response, metal uptake, and the phytostabilization potential of a nontoxic Jatropha curcas L. genotype when grown in multimetal-polluted conditions. Plants were established on a mine residue (MR) amended or not amended with corn biochar (B) and inoculated or not inoculated with the mycorrhizal fungus Acaulospora sp. (arbuscular mycorrhizal fungus, AMF). J. curcas was highly capable of growing in an MR and showed no phytotoxic symptoms. After J. curcas growth (105 days), B produced high desorption of Cd and Pb from the MR; however, no increases in metal shoot concentrations were observed. Therefore, Jatropha may be useful for phytostabilization of metals in mine tailings. The use of B is recommended because improved MR chemical properties conduced to plant growth (cation-exchange capacity, organic matter content, essential nutrients, electrical conductivity, water-holding capacity) and plant growth development (higher biomass, nutritional and physiological performance). Inoculation with an AMF did not improve any plant growth or physiological plant characteristic. Only higher Zn shoot concentration was observed, but it was not phytotoxic. Future studies of B use and its long-term effect on MR remediation should be conducted under field conditions.     

EFFECTS OF INOCULATION WITH ARBUSCULAR MYCORRHIZAL FUNGI ON MAIZE GROWN IN MULTI-METAL CONTAMINATED SOILS

Pot culture experiments were established to determine the effects of colonization by arbuscular mycorrhizal fungi (AMF) (Glomus mosseae and G. sp) on maize (Zea mays L.) grown in Pb, Zn, and Cd complex contaminated soils. AMF and non-AMF inoculated maize were grown in sterilized substrates and subjected to different soil heavy metal (Pb, Zn, Cd) concentrations. The root and shoot biomasses of inoculated maize were significantly higher than those of non-inoculated maize. Pb, Zn, and Cd concentrations in roots were significantly higher than those in shoots in both the inoculated and non-inoculated maize, indicating the heavy metals mostly accumulated in the roots of maize. The translocation rates of Pb, Zn, and Cd from roots to shoots were not significantly difference between inoculated and non-inoculated maize. However, at high soil heavy metal concentrations, Pb, Zn, and Cd in the shoots and Pb in the roots of inoculated maize were significantly reduced by about 50% compared to the non-inoculated maize. These results indicated that AMF could promote maize growth and decrease the uptake of these heavy metals at higher soil concentrations, thus protecting their hosts from the toxicity of heavy metals in Pb, Zn, and Cd complex contaminated soils.     

Effects of lead and cadmium on photosynthesis in Amaranthus spinosus and assessment of phytoremediation potential

Abstract

This study assessed the effects of Pb (0, 200, 500, 1000?mg kg^?1) and Cd (0, 5, 15, 30, 50?mg kg^?1) on photosynthesis in Amaranthus spinosus (A. spinosus), as well as the potential for phytoremediation by pot-culture experiment. Exposure to Pb/Cd produced a concentration-dependent decrease in biomass and all photosynthesis parameters, except for non-photochemical quenching, which increased with the metal concentration. The metals accumulated more in roots compared to shoots. The bioconcentration factor (BCF) of Pb was <1 in shoots at all Pb levels, whereas the BCF was <1 in roots at all but the lowest concentration of Pb. Roots extracted Cd from soil at all treatments. The translocation factor of Cd was larger than that of Pb suggesting that Cd is more mobile than Pb in A. spinosus. Amaranthus spinosus displays a high tolerance for both Pb and Cd with regards to growth and photochemical efficiency, but it is more sensitive to Cd than Pb. Amaranthus spinosus accumulates Pb and Cd primarily in the roots and Cd is more bioconcentrated and translocated in comparison to Pb. This investigation shows that A. spinosus has good potential for phytoremediation of soils contaminated by low levels of Cd and Pb.     

Sources and Ecological Risk Assessment of Heavy Metal(loid)s in Agricultural Soils of Huzhou,China

To identify sources of heavy metal(loid) (HM) contamination in agricultural soils of Huzhou, surface soil samples were sampled from 89 different agricultural regions in 2012. Concentrations of heavy metal(loid)s, along with pH, total phosphorus (TP), total nitrogen (TN), and soil organic matter (SOM), were determined. Ecological risk was then assessed using a modified Hakanson ecological risk index, and the sources of contamination were determined using principal component analysis (PCA). Mean concentrations of heavy metal(loid)s were 10.26, 23.21, 83.75, 22.81, 0.25, 61.86, 33.03, and 0.15 mg kg^?1 for As, Cu, Zn, Ni, Cd, Cr, Pb, and Hg, respectively. Cu, Zn, Ni, Cr, Cd, Hg, and Pb were correlated positively with TP and there were obvious positive correlations among Cu, Zn, Ni, Cr, and Cd. Risk index (RI) values varied from 39 to 1246 with a mean value of 137. Enrichment of Pb, Zn, Cu, and especially Cd can be attributed to excessive use of nitrogen and phosphorus fertilizers containing heavy metals, as well to surface irrigation and natural soil formation. While the ecological risk of most agricultural soils in Huzhou is low, it is recommended that the use of phosphate and nitrogen fertilizers be restricted and production technology be improved to reduce the heavy metal(loid) concentrations. Results suggest that the Chinese environmental quality standard for soil should be revised to better address heavy metal(loid) contamination.     

The metal distribution and the change of physiological and biochemical process in soybean and mung bean plants under heavy metal stress

Soybean [Glycine max (Linn.) Merrill] and mung bean [Vigna radiate (Linn.) Wilczek] plants were challenged with 5 kinds of heavy metals [cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and mercury (Hg)] in a hydroponic system. We applied 4 different metal treatments to study the effects of heavy metals on several physiological and biochemical parameters in these species, including root length, heavy metal concentrations and allocation in different organs, superoxide dismutase, catalase, and peroxidase activities, the content of malondialdehyde (MDA), protein and chlorophyll. The data showed that the growth of the roots of soybean and mung bean was equally sensitive to external Hg concentrations. Soybean was more sensitive to external Cd concentrations, and mung bean was more sensitive to external Cr, Cu and Pb concentrations. Normal concentrations of heavy metal would not cause visible toxic symptoms, and a low level of heavy metal even slightly stimulated the growth of plants. With the rise of heavy metal concentration, heavy metal stress induces an oxidative stress response in soybean and mung bean plants, characterized by an accumulation of MDA and the alternation pattern of antioxidative enzymes. Meanwhile, the growth of plants was suppressed, the content of chlorophyll decreased and leaves showed chlorosis symptoms at high metal concentrations.     

In vitro breeding of Brassica juncea L. to enhance metal accumulation and extraction properties

In vitro breeding and somaclonal variation were used as tools to improve the potential of Indian mustard (Brassica juncea L.) to extract and accumulate toxic metals. Calli from B. juncea were cultivated on a modified MS medium supplemented with 10–200 μM Cd or Pb. Afterwards, new B. juncea somaclones were regenerated from metal-tolerant callus cells. Three different phenotypes with improved tolerance of Cd, Zn and Pb were observed under hydroponic conditions: enhanced metal accumulation in both shoots and roots; limited metal translocation from roots to shoots; reduced accumulation in shoots and roots. Seven out of thirty individual variants showed a significantly higher metal extraction than the control plants. The improvement of metal shoot accumulation of the best regenerant (3× Cd, 1.6× Zn, 1.8× Pb) and metal extraction (6.2× Cd, 3.2× Zn, 3.8× Pb) indicated a successful breeding and selection of B. juncea, which could be used for phytoremediation purpose.     

Health risk perspectives of metal(loid) exposure via consumption of striped venus clam (Chamelea gallina Linnaeus, 1758)

The metal(loid)s are mainly transported to the Black Sea via rivers and affect the coastal area where fisheries are intensive. Chamelea gallina (striped venus clam) is the most abundant mollusk species in the Black Sea and used as a bioindicator for monitoring of metal(loid) pollution. In this respect, the concentrations of As, Cd, Cr, Cu, Pb, and Zn in C. gallina collected from 16 different locations along the Black Sea coast (Turkey, Bulgaria, and Russia) were determined and evaluated for the potential human health risk. The results obtained were found to be below the maximum permissible limits indicated in the food safety guidelines. Similarly, the analyzed metal(loid)s did not pose a potential hazard to humans for consumption of the C. gallina, regarding provisional tolerable weekly intake described by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Moreover, target hazard quotient and hazard index were found to be lower than 1 for not only average consumer but also the consumer who consumed a portion (160 g) once a week. In contrast, consumption of C. gallina could cause health risks for Cd and As in case of increasing portion sizes.     

盐角草在Cd、Pb、Li污染盐土修复中的应用潜力

滩涂和内陆盐碱地是重要的后备土地资源。近年来镉(Cd)、铅(Pb)等土壤重金属和锂(Li)污染对盐碱地开发利用和生产安全造成严重威胁。利用盐生植物修复污染盐土是最经济有效的方法。本研究以盐生植物盐角草SalicorniaeuropaeaL.为材料,采用盆栽方式,通过比较分析盐角草在不同浓度Cd(0-50mmol/L)、Pb(0-50 mmol/L)和Li(0-400 mmol/L)处理下的生长和生理生化指标及离子含量的变化,研究盐角草对3种金属污染物胁迫的耐性及积累特性,以期探讨盐角草在Cd、Pb、Li污染盐土修复中的应用潜力。结果显示,随着Cd、Pb处理浓度升高,盐角草的株高、鲜重和干重均显著下降。低浓度Li(≤20 mmol/L)处理促进盐角草的生长,而高浓度Li(≥20mmol/L)处理则抑制植物生长。盐角草对Cd、Pb、Li的耐受性顺序为Li>Pb>Cd。Cd、Pb、Li胁迫可能降低了盐角草对Na和K的吸收与转运而影响植株的生长。另一方面,盐角草抗氧化酶系统对Cd、Pb、Li胁迫表现出不同的响应机理,多种抗氧化物酶协同作用,抵制Cd、Pb、Li胁迫造成的氧化毒害。盐角草根和地上部分Cd、Pb、Li含量随着处理浓度的升高而增加,其中Cd和Pb的分布特征为根>地上部分,Li的分布特征为地上部分>根。研究结果表明盐角草对Cd、Pb、Li的胁迫均具有较强的耐受性与自我调节能力,且具有富锂特性,具备修复Cd、Pb、Li污染盐土的潜力。本研究为深入研究盐角草耐受Cd、Pb、Li胁迫的机制奠定了基础,揭示了利用盐角草修复高盐碱土壤中Cd、Pb、Li污染的应用潜力。     

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

Three 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.     

Accumulation of Cd and Pb in various body parts,organs and tissues of Lymantria dispar asiatica (Lepidoptera: Erebidae)

To investigate the accumulation patterns of Cd and/or Pb in various body parts, organs and tissues of the Asian gypsy moth (Lymantria dispar) larvae under Cd and/or Pb stress, Cd and Pb treated artificial diets were used to feed the larvae in the current study. These larval body parts/organs/tissues included the heads, integuments (body walls), alimentary canals, fat bodies and hemolymphs. Our results showed that under Cd and/or Pb stress, their accumulations in larval body parts/organs/tissues were significantly higher than those in the control, with the amounts of tested metals in the fat bodies and hemolymphs and alimentary canals being significantly higher than those in the heads and integuments. Under the single Cd (0, 7.5, 10.5 mg/kg) or Pb stress (0, 55, 90, 125 mg/kg), the accumulations of these heavy metals were positively correlated with their concentrations in diets. Under the combined stress (Cd × Pb), the Cd accumulation at the lower Pb concentrations was higher than that at higher Pb concentrations for the body parts/organs/tissues, similar effects of Cd concentrations on Pb accumulations were also recorded. These results clearly showed that Cd and/or Pb were accumulated in various body parts/organs/tissues at different levels under the heavy metal stress. And accumulations of Pb/Cd were positively correlated with their concentrations in the diets under the single stress. Under the combined stresses, Cd and Pb had synergistic effects at low concentrations whereas antagonistic effects at high concentrations. The accumulations of Cd and/or Pb in the gypsy moth larvae affects normal physiological and biochemical functions, and thus affects their growth and development.     

Effects of Municipal Sewage Sludge Doses on the Chlorophyll Contents and Heavy Metal Concentration of Sugar Beet (Beta vulgaris var. saccharifera)

The present study was conducted to assess the suitability of sewage sludge amendment (SSA) in soil for Beta vulgaris var. saccharifera (sugar beet) by evaluating the heavy metal accumulation and physiological responses of plants grown at a 10%, 25%, and 50% sewage sludge amendment rate. The sewage sludge amendment was modified by the physicochemical properties of soil, thus increasing the availability of heavy metals in the soil and consequently increasing accumulation in plant parts. Cd, Pb, Ni, and Cu concentrations in roots were significantly higher in plants grown at 25% as compared to 50% SSA; however, Cr and Zn concentration was higher at 50% than 25% SSA. The concentrations of heavy metal showed a trend of Zn > Ni > Cu > Cr > Pb > Cd in roots and Zn > Cu > Ni > Cr > Pb > Cd in leaves. The only instance in which the chlorophyll content did not increase after the sewage sludge treatments was 50%. There were approximately 1.12-fold differences between the control and 50% sewage sludge application for chlorophyll content. The sewage sludge amendment led to a significant increase in Pb, Cr, Cd, Cu, Zn, and Ni concentrations of the soil. The heavy metal accumulation in the soil after the treatments did not exceed the limits for the land application of sewage sludge recommended by the US Environmental Protection Agency (US EPA). The increased concentration of heavy metals in the soil due to the sewage sludge amendment led to increases in heavy metal uptake and the leaf and root concentrations of Ni, Zn, Cd, Cu, Cr, Pb, and Zn in plants as compared to those grown on unamended soil. More accumulation occurred in roots and leaves than in shoots for most of the heavy metals. The concentrations of Cd, Cr, and Pb were more than the permissible limits of national standards in the edible portion of sugar beet grown on different sewage sludge amendment ratios. The study concludes that the sewage sludge amendment in the soil for growing sugar beet may not be a good option due to risk of contamination of Cr, Pb, and Cd.     

Interaction of Heavy Metals in Multimetal Biosorption by Galerina vittiformis from Soil

ABSTRACT Soil heavy metal contamination, a major threat due to industrialization, can be tackled by an efficient and economical process called bioremediation. Mushrooms are employed to accumulate heavy metals from soil due to their high metal accumulation potential and better adaptability. The bioaccumulation potential of Galerina vittiformis was already reported for individual metals. At natural conditions, since soil consists of more than one polluting metal, more focus has to be given to multimetal systems. In this study, multimetal accumulation potential was analyzed using central composite design, and the responses obtained were analyzed using response surface methodology. Heavy metals such as Cu(II), Cd(II), Cr(VI), Pb(II), and Zn(II) were subjected to biosorption at 10–250 mg/kg concentrations along with pH 5–8. The results showed that the preference of the organism for the five metals under study was in the order Pb(II) > Zn(II) > Cd(II) > Cu(II) > Cr(VI) at pH 6.5 under multimetal condition. The study also indicates that the metal interaction pattern in multimetal interaction is a property of their ionic radii. The response surface methodology clearly explains the effect of interaction of heavy metals on the accumulation potential of the organism using three-dimensional response plots. The present work suggests that the fungus Galerina vittiformis could be employed as a low-cost metal removal agent from heavy metal–polluted soil.     

The Application of Fertilizer and AMF Promotes Growth and Reduces the Cadmium and Lead Contents of Ryegrass (<i>Lolium multiflorum</i> L.) in a Copper Mining Area

Heavy metal-polluted soil was collected from the Pulang copper mine in Shangri-La City, Yunnan Province, Southwest China. The effects of fertilizer (organic and inorganic) and arbuscular mycorrhizal fungi (AMF) on ryegrass (Lolium multiflorum L.) growth, root morphology, mineral nutrition and cadmium (Cd) and lead (Pb) contents were investigated by pot experiments. The results showed that both fertilizer and AMF significantly ameliorated the root morphology and mineral nutrition, reduced the Cd and Pb contents, and promoted the growth of ryegrass. Among all treatments, the combined application of organic–inorganic compound fertilizer with AMF had the highest effect, resulting in increases in root length, surface area and branch number by 2.3, 1.1, and 3.9 times, respectively; an 88% increase in plant biomass; a nitrogen content increase of 2.3 and 1.2 times, and phosphorus content increase of 62% and 68% in shoots and roots, respectively was also recorded as well as decreases in Cd content by 34% and 62% and Pb content by 47% and 34% in shoots and roots, respectively. Two-factor analysis showed that both fertilizer and AMF significantly promoted ryegrass growth (plant height, biomass, chlorophyll content, root length, nitrogen and phosphorus content) and reduced the Cd and Pb contents in roots, and there was a synergistic effect between them. Moreover, the nitrogen and phosphorus contents were very significantly positively correlated with the shoot and root biomasses but very significantly negatively correlated with the Cd and Pb contents of ryegrass. Thus, the application of fertilizer and AMF synergistically improved ryegrass growth on polluted soils in the copper mining area.     

Anthropogenic Influence on Selected Heavy Metal Contamination of Urban Soils of Akure City,Nigeria

Levels of Cd, Ni, and Pb in topsoil (0–5 cm) taken from seven different sites of the urban city of Akure, Nigeria, were determined using flame atomic absorption spectrophotometer after the wet digestion method. This was with a view to appraising the influence of various anthropogenic activities on heavy metal contamination of the urban soil. Results show that the range of Cd was 6.27–10.34 ppm, Ni 7.17–14.78 ppm, and Pb 9.22- 46.19 ppm. This analytical data indicated a significant accumulation of heavy metals above background levels, with highest concentrations found in mechanic/battery charger workshops. The level of accumulation was assessed using accumulation factor (AF), and the values obtained exceeded 4 in all sites. This implies that the heavy metals are not from the natural geochemistry of Akure but from human activities. The classes of contamination were differentiated using geoaccumulation index (I _geo). The I _geo performed revealed that Cd (2< I _geo<3: Class 3), Ni (2< I _geo<4: Class 3 and 4) and Pb (3< I _geo<5: Class 4 and 5) belong to different classes of geoaccumulation index, but the contamination patterns (moderately to strongly contaminated) are similar in all sites, except the mechanic battery/charger workshop (moderately to extremely contaminated). The differences observed in the metal concentrations among the sites are statistically significant (P < 0.05).     

Studies on lead and cadmium toxicity in Dianthus carthusianorum calamine ecotype cultivated in vitro

• Information on metallophytes during reclamation of land contaminated with heavy metals is sparse. We investigated the response of D. carthusianorum calamine ecotype to Pb and Cd stress. We focused on in vitro selection of tolerant plant material for direct use in chemically degraded areas.
• Shoot cultures were treated with various concentrations of Pb or Cd ions. Plantlet status was estimated as micropropagation efficiency, growth tolerance index (GTI) and through physiological analysis. Moreover, determination of plant Pb, Cd and other elements was performed.
• The application of Pb(NO₃)₂ resulted in stronger growth inhibition than application of CdCl₂. In the presence of Pb ions, a reduction was observed of both, the micropropagation coefficient to 1.1–1.8 and the GTI to 48%. In contrast, Cd ions had a positive influence on tested cultures, expressed as an increase of GTI up to 243% on medium enriched with 1.0 μm CdCl₂. Moreover, photosynthetic pigment content in shoots cultivated on media with CdCl₂ was higher than in control treatment. The adaptation to Cd was associated with decreased accumulation of phenols in the order: 0.0 μm  > 1.0 μm > 3.0 μm  > 5.5 μm CdCl₂. It seems that high tolerance to Cd is related to K uptake, which is involved in antioxidant defence.
• This work presents an innovative approach to the impact of Cd ions on plant growth and suggests a potential biological role of this metal in species from metalliferous areas.

     

Bio-remediation of Pb and Cd polluted soils by switchgrass: A case study in India

Introduction: In the present study bioremediation potential of a high biomass yielding grass, Panicum virgatum (switchgrass), along with plant associated microbes (AM fungi and Azospirillum), was tested against lead and cadmium in pot trials.

Methods: A pot trial was set up in order to evaluate bioremediation efficiency of P. virgatum in association with PAMs (Plant Associated Microbes). Growth parameters and bioremediation potential of endomycorrhizal fungi (AMF) and Azospirillum against different concentrations of Pb and Cd were compared.

Results: AM fungi and Azospirillum increased the root length, branches, surface area, and root and shoot biomass. The soil pH was found towards neutral with AMF and Azospirillum inoculations. The bioconcentration factor (BCF) for Pb (12 mg kg^?1) and Cd (10 mg kg^?1) were found to be 0.25 and 0.23 respectively and translocation index (Ti) was 17.8 and 16.7 respectively (approx 45% higher than control).

Conclusions: The lower values of BCF and Ti, even at highest concentration of Pb and Cd, revealed the capability of switchgrass of accumulating high concentration of Pb and Cd in the roots, while preventing the translocation of Pb and Cd to aerial biomass.