Evaluation of lead and chromium tolerance and accumulation level in Gomphrena celosoides: a novel metal accumulator from lead acid battery waste contaminated site in Nigeria

Abstract

Biology, tolerance, and metal (Pb and Cr) accumulating ability of Gomphrena celosoides were studied under hydroponic conditions. The seedlings were raised in Hoagland’s solution containing different concentrations of Pb (0, 500, 1000, 1500, 2000, 3000, 4000, and 5000?mg l^?1) and Cr (0, 50, 100, 150, 200, 300, and 400?mg l^?1). Biomass and metal accumulation in different plant parts were determined at seven (7) and fourteen (14) days after stress. Antioxidant enzyme activities, protein, and proline contents were estimated in stressed and unstressed plants. Gomphrena celosoides was able to tolerate Pb and Cr concentrations up to 4000 and 100?mg l^?1, respectively in hydroponic solution. Metal accumulation was concentration and duration dependent with the highest Pb (21,127.90 and 117,985.29?mg kg^?1) and Cr (3130.85 and 2428.90?mg kg^?1) in shoot and root, respectively found in the plants exposed to 5000?mg l^?1 Pb and 400?mg l^?1 Cr for 14?days. Proline, antioxidant enzyme activities, and protein contents were the highest in plant exposed to higher Pb and Cr concentrations for 7 and 14?days. Gomphrena celosoides could be considered as Pb and Cr accumulator with proline and increase in antioxidant enzyme activities being the tolerance mechanisms.     

A Study on Selected Physiological Parameters of Plants Grown Under Lithium Supplementation

Exposure of sunflower and maize plants to increasing concentrations of lithium (0?C50?mg Li dm^?3) in a nutrient solution induced changes in biomass, leaf area and photosynthetic pigment accumulation, as well as levels of lipid peroxidation. The highest applied lithium dose (50?mg Li dm^?3) evoked a significant reduction in the shoot biomass for both examined species, as well as necrotic spots and a reduction of the leaf area in sunflower plants. An enrichment of a nutrient solution with 5?C50?mg Li dm^?3 did not significantly affect chlorophylls a and b and the carotenoid content in sunflower plants. However, in maize, a significant decrease in all pigment content under highest used lithium concentration was noted. The levels of lipid peroxidation of the cell membranes in leaves of sunflower plants and the roots of maize increased significantly in the presence of 50?mg Li dm^?3, which suggests disturbances of the membrane integrity and pro-oxidant properties of the excess lithium ions. Nonetheless, in maize, an increase of shoot biomass and leaf area in the presence of 5?mg Li dm^?3 was found. An analysis of the metal content indicated that lithium accumulated significantly in sunflower and maize shoots in a dose-dependent manner, but differences occurred between species. The sunflower plants accumulated considerably greater amounts of this metal than maize. The potassium content in shoots remained unchanged under lithium treatments, except for a significant increase in the potassium levels for sunflower plants grown in the presence of 50?mg Li dm^?3. These results suggest that lithium at 50?mg Li dm^?3 is toxic to both plant species, but the symptoms of toxicity are species-specific. Moreover, the lithium influence on plants is dose-dependent and its ions can exert toxicity at high concentrations (50?mg Li dm^?3) or stimulate growth at low concentrations (5?mg Li dm^?3).     

Responses of soil microbial community and enzymes during plant-assisted biodegradation of di-(2-ethylhexyl) phthalate and pyrene

Abstract

A pot experiment was conducted to explore the plant-assisted degradation efficiency of di-(2-ethylhexyl) phthalate (DEHP) and pyrene. Three plant species: Ceylon spinach, sunflower, and leaf mustard were cultivated in co-contaminated soils under three contamination levels: control (T0), 20?mg kg^?1 (T20), and 50?mg kg^?1 (T50). The results showed that a higher DEHP and pyrene degradation efficiency was observed evidently in planted cases, increasing from 42 to 53–59% (T0), 61 to 65–76% (T20) and 52 to 68–78% (T50) for DEHP, and from 22 to 30–49% (T0), 58 to 62–72% (T20), and 54 to 57–70% (T50) for pyrene. Under T20 contamination level, soil phospholipid fatty-acid analysis depicted the increased microbial biomass in rhizosphere, especially the arbuscular mycorrhizal fungus that is effective for the degradation of organic pollutants. The study also revealed that the activities of dehydrogenase, acid phosphomonoesterase, urease, and phenol oxidase negatively correlated with pollutant concentration. In general, the removal rate of DEHP and pyrene was highest in the soil planted with leaf mustard for each contamination level considered. For soils at T20 level, sunflower and leaf mustard appeared as interesting phytoremediation plants due to the improved removal rates of organic pollutants and the soil microbial activity.     

Changes in the speciation,partitioning and phytoavailability of chromium induced by organic soil amendments

Abstract

This study investigated the effect of two organic amendments (compost of cattle ruminai content and Sphagnum-moss peat) on the reduction of hexavalent chromium and the distribution of this metal among the main solid phases of a soil with low organic matter content treated with different levels of Cr(VI) (0–2000 mg Cr kg^?1 soil). At the same level of added organic carbon, the peat reduced Cr(VI) added to the soil from 250 to 2000 mg kg^?1, with 100% efficiency. The reduction efficiency of the compost, however, decreased with the increasing dose of Cr(VI) soil. The distribution of Cr between the different soil components was evaluated by a sequential chemical extraction procedure. The concentration of water-soluble and exchangeable Cr decreased with the addition of organic amendments to the soil, whereas Cr increased in the organic fraction. The effect of added organic material on the Cr absorption was examined with two ornamental plants (Melissa officinalis and Begonia semperflorens). The increased Cr(VI) in the soil increased the Cr concentration in plant tissues. The addition of organic matter produced a greater aerial biomass for each level of added Cr in comparison with unamended soil. Sphagnum moss peat was more effective than the compost to decrease the total Cr and the Cr(VI) concentration in the water-soluble and exchangeable fraction of soil, thereby reducing the Cr accumulation in plants tissues and phytotoxic symptoms.     

Simultaneous speciation of chromium by spectrophotometry and multicomponent analysis

Abstract

A simple, fast and sensitive spectrophotometric method for the simultaneous determination of Cr(III) and Cr(VI) in effluents and contaminated waters using a UV-visible spectrophotometer, which operates with an advanced software for multicomponent analysis, is proposed. The method consists in the complexation of Cr (III) with EDTA and reaction of Cr(VI) with diphenylcarbazide (DPC). Variables, such as pH and colour stability time, were studied. The effect of concomitant ions on the simultaneous Cr(III) and Cr(VI) determination was also investigated. The sums of the chromium species concentrations obtained by the proposed method were compared with the total chromium concentrations found by electrothermal atomic absorption spectrometry. Recoveries of the chromium species between 75 and 136% were obtained for spiked samples. The linear working range for Cr(III) was 0.5-30 mg L^?1, while for Cr(VI) was 0.005-0.30 mg L^?1. The detection limits were 0.3 mg L^?1 for Cr(III) and 0.003 mg L^?1 for Cr(VI) while the quantification limits were 1.0 mg L^?1 for Cr(III) and 0.01 mg L^?1 for Cr(VI).     

Salicylic acid induces amelioration of chromium toxicity and affects antioxidant enzyme activity in Sorghum bicolor L.

Aim: Chromium (Cr(VI)) would inflict serious morphological, metabolic, and physiological anomalies in plants ranging from chlorosis of shoot to lipid peroxidation and protein degradation. Cr(VI) toxicity is often associated with oxidative stress, caused by the excessive formation of reactive oxygen species (ROS). In response, plants are equipped with a repertoire of mechanisms to counteract heavy metal (HM) toxicity. Salicylic acid (SA) plays a key role in the signal transduction pathways of various stress responses, demonstrating the protective effect of SA against abiotic stress factors. So, the present investigation was carried out to study the amelioration of pernicious effects of different concentration of Cr(VI) (0.0, 2.0, and 4.0?mg Cr(VI) kg^?1 soil in the form of potassium dichromate) by treatments of salicylic acid solution viz. pretreatment and foliar spray via antioxidative enzymes and their metabolites.

Results: With different treatments of salicylic acid solution, the reinstatement from ill effects of Cr(VI) toxicity was contemplated but the most conspicuous effect was observed when salicylic acid solution was supplied through the foliar spray (0.50?mM). This was accompanied with an increase in ascorbate peroxidase activity and hydrogen peroxide content and decrease in peroxidase activity and ascorbic acid content.

Significance of the study: This study suggests that salicylic acid when applied through pre-treatment of seeds or through a foliar spray can be used to ameliorate the toxic effects of chromium (VI). Salicylic acid has the great potential for reducing the toxicity of heavy metals without negatively impacting the growth of the plants.     

A rapid and economical sample pretreatment method using molecularly imprinted polymers for bioavailable content analyses of oxytetracycline in soils

Abstract

In order to analyze the bioavailable oxytetracycline (OTC) contents of soils, a new high-efficiency and economical pretreatment method was established using a molecularly imprinted polymer (MIP) with high affinity and specific selectivity for OTC synthesized by bulk polymerization. For comparison, an Oasis HLB solid phase extraction (SPE) method was used to measure the total extractable OTC content of soils. The resulting OTC recoveries from the spiked soil solutions using the MIP method ranged from 80.78±.26% to 93.75?±?6.79%, with an average of 86.00?±?2.13%, and a relative standard deviation of 2.48% (n= 5), when OTC concentrations in spiked soil solutions varied from 0.5 to 100.0?μg L^?1. When OTC contents in spiked soils varied from 1.0 to 500.0?μg kg^?1 and soils were aged for three weeks, OTC recoveries from spiked soils with the Oasis HLB SPE method ranged from 78.16?±?3.72% to 96.67?±?1.62% (n= 3), while those with the MIP method ranged from 57.43?±?3.48% to 76.34?±?1.30% (n= 3). Analyses of OTC contents in five soil samples indicated that bioavailable OTC contents were only 1.35%–5.87% of the total soil OTC contents. Data from the new method were more valuable than the Oasis HLB SPE method on OTC pollution intensity assessment, potential ecological, and environmental risks evaluation.     

Protective effect exerted by soil phosphorus on soybean subjected to arsenic and fluoride

Objetive: Arsenic (As) and fluoride (F) are found in groundwater and soils around the world, causing different problems to crops. Because these elements compete against phosphorus (P) in soils and plants, their relationship is complex. The aim of this work was to study the oxidative stress of soybean plants subjected to different concentrations of As and F, and the effect of P.

Methods: The following 10 treatments were carried out in each of two soils with different P content: three As levels (low 10?mg?As?kg^-1, medium 50?mg?As?kg^?1 and high 100?mg As kg^?1), three F levels (low 160?mg?F?kg^?1, medium 250?mg?F?kg^?1 and high 500?mg?F?kg^?1) and three As?+?F levels (same concentrations), and the control treatment (soil with the background As and F concentrations) Lipid peroxidation, chlorophyll, gluthatione contents and antioxidant enzymes activities were determination.

Results: Increased lipid peroxidation and alterations in glutathione content, catalase, superoxide dismutase and peroxidase activities as well as in chlorophyll content revealed that As causes higher oxidative stress in plants grown in soils with low P content.

Conclusion: Stress parameters in F treatments were less affected. Plants grown in soils enriched with P revealed a decrease in the toxic effects caused by As and F.     

Effect of bacterial inoculation of strains of pseudomonas aeruginosa,alcaligenes feacalis and bacillus subtilis on germination,growth and heavy metal (cd,cr, and ni) uptake of brassica juncea

Bacterial inoculation may influence Brassica juncea growth and heavy metal (Ni, Cr, and Cd) accumulation. Three metal tolerant bacterial isolates (BCr3, BCd33, and BNi11) recovered from mine tailings, identified as Pseudomonas aeruginosa KP717554, Alcaligenes feacalis KP717561, and Bacillus subtilis KP717559 were used. The isolates exhibited multiple plant growth beneficial characteristics including the production of indole-3-acetic acid, hydrogen cyanide, ammonia, insoluble phosphate solubilization together with the potential to protect plants against fungal pathogens. Bacterial inoculation improved seeds germination of B. juncea plant in the presence of 0.1 mM Cr, Cd, and Ni, as compared to the control treatment. Compared with control treatment, soil inoculation with bacterial isolates significantly increased the amount of soluble heavy metals in soil by 51% (Cr), 50% (Cd), and 44% (Ni) respectively. Pot experiment of B. juncea grown in soil spiked with 100 mg kg^?1 of NiCl₂, 100 mg kg^?1 of CdCl₂, and 150 mg kg^?1 of K₂Cr₂O₇, revealed that inoculation with metal tolerant bacteria not only protected plants against the toxic effects of heavy metals, but also increased growth and metal accumulation of plants significantly. These findings suggest that such metal tolerant, plant growth promoting bacteria are valuable tools which could be used to develop bio-inoculants for enhancing the efficiency of phytoextraction.     

Evaluation of chromium phyto-toxicity,phyto-tolerance,and phyto-accumulation using biofuel plants for effective phytoremediation

Contamination of chromium signifies one of the major threats to soil system. Phytoremediation is a promising technique to reclaim metal-contaminated soil using plants which are capable to tolerate and accumulate heavy metals within in their tissues. The experiment reported in this article was carried out with six biofuel plant species, Cyamopsis tetragonoloba, Glycine max, Avena sativa, Abelmoschus esculentus, Sesamum indicum and Guizotia abyssinica, were subjected to eight Cr concentrations (0.5, 2.5, 5, 10, 25, 50, 75 and 100?mg kg^?1 soil) to investigate Cr toxicity, tolerance and accumulation. After 12?weeks of experiment, Cr phytotoxicity on morphological and biochemical parameters were evaluated. For six plant species, seed germination and most of growth parameters were significantly (p?C. tetragonoloba?>?A. sativa?>?A. esculentus?>?S. indicum?>?G. max?>?G. abyssinica. Bioconcentration factor, bioaccumulation coefficient, translocation factor and phytoremdiation ratio suggested that C. tetragonoloba, A. sativa and A. esculentus being more tolerant; having higher Cr accumulation and could be a high efficient plants for reclamation of Cr-contaminated soils.     

Chelator-assisted phytoextraction of arsenic,cadmium and lead by Pteris vittata L. and soil microbial community structure response

Abstract

Using biodegradable chelators to assist in phytoextraction may be an effective approach to enhance the heavy-metal remediation efficiencies of plants. A pot experiment was conducted to investigate the effects of ethylenediamine disuccinic acid (EDDS), citric acid (CA), and oxalic acid (OA) on the growth of the arsenic (As) hyperaccumulator Pteris vittata L., its arsenic (As), cadmium (Cd), and lead (Pb) uptake and accumulation, and soil microbial responses in multi-metal(loid)-contaminated soil. The addition of 2.5-mmol kg^?1 OA (OA-2.5) produced 26.7 and 14.9% more rhizoid and shoot biomass, respectively compared with the control, while EDDS and CA treatments significantly inhibited plant growth. The As accumulation in plants after the OA-2.5 treatment increased by 44.2% and the Cd and Pb accumulation in plants after a 1-mmol kg^?1 EDDS treatment increased by 24.5 and 19.6%, respectively. Soil urease enzyme activities in OA-2.5 treatment were significantly greater than those in the control and other chelator treatments (p?<?0.05). A PCR–denatured gradient gel electrophoresis analysis revealed that with the addition of EDDS, CA and OA enhanced soil microbial diversity. It was concluded that the addition of OA-2.5 was suitable for facilitating phytoremediation of soil As and did not have negative effects on the microbial community.     

Effects of 5-aminolevulinic acid on nitrogen metabolism and ion distribution of watermelon seedlings under salt stress

The effects of foliar spray application of 5-aminolevulinic acid (ALA) on the growth, nitrogen metabolism, and ion distribution of salt-stressed watermelon (Citrullus lanatus (Thunb.) Matsum. and Nakai) seedlings were investigated. Supplementation of the nutrient solution with 100 mM NaCl significantly reduced leaf and root biomass of watermelon plants. Foliar application of 1.25 mM ALA significantly alleviated the inhibition of plant growth under salt stress. Salinity induced significant accumulation of nitrate, ammonium, and soluble protein and a significant decrease in the activities of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH) in watermelon plants. However, ALA significantly increased the activities of NR, GS, GOGAT, and GDH, but decreased the ammonium content and NiR activity. In addition, salt stress resulted in significant accumulation of Na⁺ and Cl^? in plants, but decreased the contents of K⁺ and Mg²⁺. Application of ALA alleviated the salt stress-induced ion toxicity, and increased the contents of K⁺ and Mg²⁺. ALA also increased soluble protein and proline contents in salt-stressed watermelon plants. These results indicated that application of ALA alleviated the accumulation of Na⁺ and Cl^? in salt-stressed watermelon plants, especially through regulating nitrogen metabolism and ion distribution, which were associated with an improvement in plant growth.     

Bacterial inoculation speeds zinc release from ground tire rubber used as Zn fertilizer for corn and sunflower in a calcareous soil

Background and Aims

We tested the utility of some biological treatments to hasten degradation of waste tire rubber in soil and thus the release of zinc and sulfur for plant uptake.

Methods

Three rates of ground tire rubber (0, 150, and 300?mg?kg^?1) were incorporated into a Zn-deficient calcareous soil. Before addition to the soil, ground rubber was given four microbial treatments including no inoculation, inoculation with Rhodococcus erythropolis, inoculation with R. erythropolis+Escherichia coli, and inoculation with R. erythropolis+E. coli+Acinobacter calcoaceticus. In the pot experiment, corn (Zea mays L. Hybrid Single Cross 500) and sunflower (Helianthus annuus L. cv. Record) plants were exposed to three rates of ground rubber (0, 150, and 300?mg?kg^?1) or 3?mg zinc kg^?1 as ZnSO₄. Before addition to the soil, ground rubber and ZnSO₄ were inoculated or non-inoculated with R. erythropolis+E. coli+A. calcoaceticus.

Results

Ground rubber and microbial inoculation treatments reduced soil pH and the magnitude of this reduction increased over time. Ground rubber in combination with microbial inoculation increased DTPA-extractable soil Zn and Fe. The amount of DTPA-extractable Zn and Fe of rubber-amended soils increased over time so that the highest concentration of available Zn and Fe was found at week 10. Application of microbial inoculated ground tire rubber significantly increased shoot Zn concentration of each plant species.

Conclusions

Bacterial inoculation of ground rubber was effective in hastening increase in DTPA-extractable Zn in the studied calcareous soil and in enhancing Zn uptake by plants.     

Cadmium uptake kinetics and plants factors of shoot Cd concentration

Background and aims

Accumulation of Cd in the shoots of plants grown on Cd contaminated soils shows considerable variation. A previous preliminary experiment established that one major reason for this variation was the rate of Cd influx into the roots (mol Cd cm^?2 root s^?1). However, this experiment did not distinguish between solubilization of soil Cd on the one hand and difference in Cd uptake kinetics on the other. The main objectives of the present study were thus to characterize Cd uptake kinetics of plants continuously exposed to Cd concentrations similar to those encountered in soils. Furthermore we determined the factors responsible for differences in shoot Cd concentration such as net Cd influx, root area-shoot dry weight ratio, shoot growth rate and proportion of Cd translocated to the shoot.

Materials and methods

Maize, sunflower, flax and spinach were grown in nutrient solution with five constant Cd concentrations varying from 0 to 1.0 μmol?L^?1. Root and shoot parameters as well as Cd uptake were determined at two harvest dates and from these data Cd net influx and shoot growth rates were calculated.

Results and conclusions

Cadmium uptake kinetics, i.e. the net Cd influx vs. Cd solution concentration followed a straight line. Its slope is the root absorbing power, α, $ \left( {\alpha ={{{\mathrm{Cd}\;\mathrm{net}\;\mathrm{influx}}} \left/ {{\mathrm{Cd}\;\mathrm{solution}\;\mathrm{concentration}}} \right.}} \right) $ . The α values of spinach and flax were about double that of maize and sunflower (5?×?10^?6?cm?s^?1 vs. 2.5?×?10^?6?cm?s^?1). Spinach and flax had a 3–5 times higher shoot Cd concentration than maize and sunflower. The difference in shoot Cd concentration was partly due to the higher Cd influx but also to a higher translocation of Cd from root to shoot and also to a slower shoot growth rate.     

Efficacy of soaking cotton seeds within salicylic acid and potassium silicate on reducing reniform nematode infection

ABSTARCT

The efficiency of soaking cotton cv. Giza 45 seeds in five concentrations of salicylic acid and potassium silicate (5, 10, 15, 20 and 25?mg?L^?1 against Rotylenchulus reniformis infection showed a significant (P?<?0.05) improvement in the tested plant parameters that was distinct in soaked seeds in salicylic acid for 24?hours compared with potassium silicate in greenhouse (28?±?5?°C). The application of concentration (20?mg?L^?1) stated the highest values of improvement of plant criteria, while high concentration (25?mg?L^?1) revealed the maximum reduction rates in the total nematode population for both potassium silicate and salicylic acid. Moreover, seed soaking in salicylic acid and potassium silicate achieved a considerable increment in nitrogen, phosphorus, potassium, phenol and chlorophyll contents in cotton leaves with changeable values.     

Electrokinetic-enhanced phytoremediation of uranium-contaminated soil using sunflower and Indian mustard

Abstract

Electrokinetic-enhanced phytoremediation is an effective technology to decontaminate heavy metal contaminated soil. In this study, we examined the effects of electrokinetic treatments on plant uptake and bioaccumulation of U from soils with various U sources. Redistribution of uranium in soils as affected by planting and electrokinetic treatments was investigated. The soil was spiked with 100?mg kg^–1 UO₂, UO₃, and UO₂(NO₃)₂. After sunflower and Indian mustard grew for 60 days, 1 voltage of direct-current was applied across the soils for 9 days. The results indicated that U uptake in both plants were significantly enhanced by electrokinetic treatments from soil with UO₃ and UO₂(NO₃)₂. U was more accumulated in roots than in shoots. Electrokinetic treatments were effective on lowering soil pH near the anode region. Overall, uranium (U) removal efficiency reached 3.4–4.3% from soils with UO₃ and uranyl with both plants while that from soil with UO₂ was 0.7–0.8%. Electrokinetic remediation treatment significantly enhanced the U removal efficiency (5–6%) from soils with UO₃ and uranyl but it was 0.8–1.3% from soil with UO₂, indicating significant effects of U species and electrokinetic enhancement on U bioaccumulation. This study implies the potential feasibility of electrokinetic-enhanced phytoremediation of U soils with sunflower and Indian mustard.     

The Ameliorative Role of 5-Aminolevulinic Acid (ALA) Under Cr Stress in Two Maize Cultivars Showing Differential Sensitivity to Cr Stress Tolerance

Heavy metal (HM) contamination of the environment is a serious threat to sustainable crop production. Among the HMs, chromium (Cr) is one of the most toxic HMs that is known to negatively affect growth and metabolic activities of diverse crop plants. The present study was designed to investigate the ameliorative role of 5-aminolevulinic acid (ALA) under Cr stress in two maize (Zea mays L.) cultivars showing differential sensitivity to Cr tolerance. ALA is a biosynthesis precursor and it has a dominant regulatory effect related to physiological, respiratory, and photosynthesis processes in various plant species. Three concentrations of Cr (0, 5, and 10 mg kg⁻¹) were tested under the graded levels of ALA application (0, 12.5, and 25 mg L⁻¹). The results indicated that Cr stress differentially reduced plant growth attributes, gas exchange characteristics, photosynthetic pigments, and biomass in both the cultivars. Oxidative stress increased as evidenced in the form of electrolyte leakage, malondialdehyde, and hydrogen peroxide (H₂O₂) accumulation in plants. The anti-oxidative enzyme activities, that is, catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) both in the leaves and roots of maize cultivars decreased due to Cr stress. The concentration of Cr increased in roots and shoots of maize under Cr levels without ALA. Under Cr stress, ALA exogenous application markedly enhanced plant growth, photosynthetic pigments, gas exchange capacity, and biomass. Furthermore, ALA application decreased the Cr-induced oxidative stress in maize cultivars by improving the activities of CAT, POD, and SOD in plants. After ALA application, the Cr concentrations and total Cr uptake by plants differently decreased in both cultivars. The 6103 cultivar of maize was found to be a tolerant cultivar against Cr stress due to its strong defensive system with a higher rate of antioxidant enzyme activities. On the other hand, the other maize cultivar (9108) was found to be a sensitive cultivar against Cr stress due to its weak defense system with higher contents of reactive oxygen species. These findings suggest that ALA can play a regulatory role in maintaining optimum plant growth and efficient photosynthetic processes under Cr-challenged habitats in maize. Thus, ALA application may be used as a sustainable remedial strategy to alleviate Cr-induced stress in maize cultivars.

     

Impact of picolinic acid on the chromium accumulation in fodder radish and komatsuna

Effects of picolinic acid (2-pyridinecarboxylic acid) and chromium(III) picolinate was studied on the chromium (Cr) accumulation of fodder radish (Raphanus sativus L. convar. oleiformis Pers., cv. Leveles olajretek) and komatsuna (Brassica campestris L. subsp. napus f. et Thoms. var. komatsuna Makino, cv. Kuromaru ) grown in a pot experiment. Control cultures, grown in an uncontaminated soil (UCS; humous sand with pH_KCl 7.48, sand texture with 12.4% clay+silt content, organic carbon 0.56%, CaCO₃ 2.2%, CEC 6.2 cmol_c kg^–1, Cr 10.6 mg kg^–1), accumulated low amounts of chromium (less than 5.4 g g^–1) in their roots or shoots. When this UCS was artificially contaminated with 100 mg kg^–1 Cr (CrCl₃) later picolinic acid treatment promoted the translocation of chromium into the shoots of both species. In fodder radish shoots Cr concentration reached 30.4 g g^–1 and in komatsuna shoots 44.5 g g^–1. Application of ethylene diamine tetra-acetic acid (EDTA) to this Cr contaminated soil had similar effect to picolinic acid. When the UCS was amended with leather factory sewage sediment (which resulted in 853 mg kg^–1 Cr in soil), Cr mobilization was observed only after repeated soil picolinic acid applications. From a galvanic mud contaminated soil (brown forest soil with pH_KCl 6.77, loamy sand texture with 26.6% clay+silt content, organic carbon 1.23%, CaCO₃ 0.7%, CEC 24.5 cmol_c kg^–1, Cd 5.0 mg kg^–1, Cr 135 mg kg^–1, and Zn 360 mg kg^–1) the rate of Cr mobilization was negligible, only a slight increase was observed in Cr concentration of fodder radish shoots after repeated picolinic acid treatments of soil. Presumably picolinic acid forms a water soluble complex (chromium(III) picolinate) with Cr in the soil, which promotes translocation of this element (and also Cu) into the shoots of plants. The rate of complex formation may be related to the binding forms and/or concentration of Cr in soil and also to soil characteristics (i.e. pH, CEC), since the rate of Cr translocation was the following: artificially contaminated soil > leather factory sewage sediment amended soil > galvanic mud contaminated soil. Four times repeated 10 mg kg^–1 chromium(III) picolinate application to UCS multiplied the transport of chromium to shoots, as compared to single 10 mg kg^–1 CrCl₃ treatment. This also suggests that chromium(III) picolinate is forming in the picolinic acid treated Cr-contaminated soils, and plants more readily accumulates and translocates organically bound Cr than ionic Cr. Picolinic acid promotes Cr translocation in soil-plant system. This could be useful in phytoextraction (phytoremediation) of Cr contaminated soils or in the production of Cr enriched foodstuffs.     

Plant Uptake and Enhanced Dissipation of Di(2-Ethylhexyl) Phthalate (DEHP) in Spiked Soils by Different Plant Species

This study was conducted to investigate the uptake, accumulation and the enhanced dissipation of di(2-ethylhexyl) phthalate (DEHP) spiked in soil (with a concentration of 117.4 ± 5.2 mg kg^?1) by eleven plants including eight maize ( Zea mays) cultivars and three forage species (alfalfa, ryegrass and teosinte). The results showed that, after 40 days of treatment, the removal rates of DEHP ranged from 66.8% (for the control) to 87.5% (for the maize cultivar of Huanong-1). Higher removal rate was observed during the first 10 days than the following days. Plants enhanced significantly the dissipation of DEHP in soil. Enhanced dissipation amount in planted soil was 13.3–122 mg pot^?1 for DEHP, and a net removal of 2.2%–20.7% of the initial DEHP was obtained compared with non-plant soil. The contribution of plant uptake to the total enhanced dissipation was <0.3%, and the enhanced dissipation of soil DEHP might be derived from plant-promoted biodegradation and sorption stronger to the soil. Nevertheless, the capability in accumulation and enhanced dissipation of DEHP from spiked soils varied within different species and cultivars.     

X-ray Fluorescence (XRF) Analysis of Soil Heavy Metal Pollution from an Industrial Area in Kumasi,Ghana

Knowledge of soil heavy metal concentration is very important for assessing the purity and quality of the soil in an environment. The concentrations of nine heavy metals (NHM), Zn, Pb, Cr, Cu, Co, Ni, Cd, Hg, and As, from the near-surface soils (～ 0–15 cm) from an industrial cluster in Kumasi, Ghana, were qualitatively and quantitatively measured and analyzed using X-ray fluorescence (XRF) spectroscopy analysis. The sources of these NHM were mainly anthropogenic as a result of the indiscriminate industrial waste disposal. In all, a total of about 100 soil samples were taken from six sampling sites, four of which were industrial and the remaining two residential. Forty soil samples out of the total number were carefully selected for elemental analyses and the mean heavy metal concentrations were calculated using statistical methods. The results from locations of high industrial impact showed that the mean concentrations of the NHM present in the soil were in the order of Zn (189.2?908.6 mgkg^?1), Pb (133.7?571.3 mgkg^?1), Cr (91.3?545.8 mgkg^?1), Cu (62.9?334.6 mgkg^?1), Co (38.6?81.9 mgkg^?1), Ni (12.4?30.9 mgkg^?1), Cd (6.9?13.2 mgkg^?1), Hg (5.5?10.4 mg kg^?1), and As (2.3?18.6 mgkg^?1). Apart from Ni and As, all the heavy metals recorded concentrations that ranged from 10?900% higher than their respective threshold limit values (TLVs). Heavy metal concentrations from the residential sites were comparatively far lower with only Cr, Cd, and Hg registering concentrations between 65?250% above their TLVs. The cluster with its residential communities is at a serious risk of soil heavy metal toxicity and awareness to this needs to be created as such.