Characterization of cadmium (Cd) distribution and accumulation in Tagetes erecta L. seedlings: Effect of split-root and of remove-xylem/phloem

Tagetes erecta has a high potential for cadmium (Cd) phytoremediation. Through several hydroponic experiments, characteristics of ¹⁰⁸Cd distribution and accumulation were investigated in T. erecta with split -roots or removed xylem/phloem. The results showed that ¹⁰⁸Cd transport from roots to aboveground tissues showed the homolateral transport phenomenon in split-root seedlings. ¹⁰⁸Cd content of leaves on the +¹⁰⁸Cd side and the −¹⁰⁸Cd side was not significantly different, which implied that there was horizontal transport of ¹⁰⁸Cd from the +¹⁰⁸Cd side to the −¹⁰⁸Cd side in cut-root seedlings. Like ¹⁰⁸Cd transport, the transport of ⁷⁰Zn was homolateral. Reduction of water consumption in the removed xylem treatment significantly decreased ¹⁰⁸Cd accumulation; whereas, the removed phloem treatment had no significant effect on water consumption, but did decrease ¹⁰⁸Cd accumulation in leaves of the seedlings. The removal of phloem significantly reduced distal leaf ¹⁰⁸Cd content, which was significantly lower than that in the basal leaves in both the split-root and unsplit-root seedlings. Overall, the results presented in this study revealed that the root to aboveground cadmium translocation via phloem is as an important and common physiological process as xylem determination of the cadmium accumulation in stems and leaves of marigold seedlings.     

Effect of Cuscuta campestris parasitism on the physiological and anatomical changes in untreated and herbicide-treated sugar beet

The effects of field dodder on physiological and anatomical processes in untreated sugar beet plants and the effects of propyzamide on field dodder were examined under controlled conditions. The experiment included the following variants: N—noninfested sugar beet plants (control); I - infested sugar beet plants (untreated), and infested plants treated with propyzamide (1500 g a.i. ha^?1 (T₁) and 2000 g a.i. ha^?1(T₂)). The following parameters were checked: physiological—pigment contents (chlorophyll a, chlorophyll b, total carotenoids); anatomical -leaf parameters: thickness of epidermis, parenchyma and spongy tissue, mesophyll and underside leaf epidermis, and diameter of bundle sheath cells; petiole parameters: diameter of tracheid, petiole hydraulic conductance, xylem surface, phloem cell diameter and phloem area in sugar beet plants. A conventional paraffin wax method was used to prepare the samples for microscopy. Pigment contents were measured spectrophotometrically after methanol extraction. All parameters were measured: prior to herbicide application (0 assessment), then 7, 14, 21, 28 and 35 days after application (DAA). Field dodder was found to affect the pigment contents in untreated sugar beet plants, causing significant reductions. Conversely, reduction in the treated plants decreased 27% to 4% for chlorophyll a, from 21% to 5% for chlorophyll b, and from 28% to 5% for carotenoids (T₁). Also, in treatment T_2, reduction decreased in infested and treated plants from 19% to 2% for chlorophyll a, from 21% to 2% for chlorophyll b, from 23% to 3% for carotenoids and stimulation of 1% and 2% was observed 28 and 35 DAA, respectively. Plants infested (untreated) by field dodder had lower values of most anatomical parameters, compared to noninfested plants. The measured anatomical parameters of sugar beet leaves and petiole had significantly higher values in noninfested plants and plants treated with propyzamide than in untreated plants. Also, the results showed that propyzamide is an adequate herbicide for control of field dodder at the stage of early infestation.     

Temporal variations and bioaccumulation of heavy metals in different Suaeda salsa marshes of the Yellow River estuary,China

To understand the temporal variations and bioaccumulation of heavy metals in the coastal marshes, the concentrations of heavy metals (Cr, Ni, Pb, and Cu) in the two Suaeda salsa marshes [middle S. salsa marsh (MM) and low S. salsa marsh (LM)] of the Yellow River estuary were determined from May to November in 2008 by in situ sampling and inductively coupled plasma mass spectrometry (ICP-MS) analysis. Results showed that heavy metal concentrations in S. salsa of MM and LM were generally in the order of Cu?>?Cr?>?Pb?>?Ni, while those in sediments fell in the order of Cr?>?Ni?>?Cu?>?Pb. Heavy metal concentrations of S. salsa in MM and LM were different, and significant differences were observed in stems (F?=?4.797, p?=?0.046) and litters (F?=?6.799, p?=?0.026) for Ni. Litter was the main stock of heavy metals, and the allocations of Cr, Ni, and Pb reached 31.25–51.31, 28.49–42.58, and 29.55–66.79 % (in MM) and 36.73–48.60, 41.70–57.87, and 33.30–60.64 % (in LM), respectively. The ratios of roots/leaves (R/L) and roots/stems (R/S) for Cr and Ni in MM were mostly greater than 1, while those ratios in LM were mostly less than 1, indicating that Cr and Ni in S. salsa at LM had greater mobility compared with those at MM. Moreover, the [accumulation factor, AF]_plant of Cr, Ni, Cu, and Pb in LM, especially [AF]_root and [AF]_stem of Cr and [AF]_litter of Ni, was also higher than that in MM. These indicated that S. salsa grown in LM was more suitable for potential biomonitor or phytoremediation of Cr, Ni, Cu, and Pb if intertidal sediments were seriously contaminated with an increase of pollutant loading (especially heavy metals) in the Yellow River estuary. The use of biomonitor (S. salsa) living and growing in LM could yield valuable information not only on the presence of anthropogenic stressors, but, more importantly, on the adverse influence the stressors are having on the environment.     

Lead accumulation and association with Fe on Typha latifolia root from an urban brownfield site

Synchrotron X-ray microfluorescence and X-ray absorption near-edge microstructure spectroscopy techniques were applied to Typha latifolia (cattail) root sections and rhizosphere soils collected from a brownfield site in New Jersey to investigate lead (Pb) accumulation in T. latifolia roots and the role of iron (Fe) plaque in controlling Pb uptake. We found that Pb and Fe spatial distribution patterns in the root tissues are similar with both metals present at high concentrations mainly in the epidermis and at low concentrations in the vascular tissue (xylem and phloem), and the major Pb and Fe species in T. latifolia root are Pb(II) and Fe(III) regardless of concentration levels. The sequestration of Pb by T. latifolia roots suggests a potential low-cost remediation method (phytostabilization) to manage Pb-contaminated sediments for brownfield remediation while performing wetland rehabilitation.     

Accumulation of heavy metals and antioxidant responses in Vicia faba plants grown on monometallic contaminated soil

The purpose of this study was to explore the effects of soil contamination by selected metals (cadmium, copper, nickel, lead or zinc) on the antioxidant response of Vicia faba plants. The levels of the antioxidants: glutathione, proline, non-protein thiols, as well as guaiacol peroxidase and catalase activities were measured in the upperparts of plants. Additionally, the potential bioavailability of metals in the soil and their concentrations in V. faba plants were compared. Treatment with metal caused the problem of an elevation in its bioavailability in soil and its concentration in leaves and stems. The most serious problems seemed to be metal elevations in soil, especially Zn and Ni as well as in the aerial parts of V. faba plants. The antioxidant responses appeared to be metal specific. The elevation of guaiacol peroxidase activity in leaves and stems as well as the proline in leaves was the only more general reaction to metal exposure. Upon analysis of the effects of soil metal contamination on V. faba plants, we recommend the use of some measurements such as guaiacol peroxidase activity and proline level as useful tools in biological monitoring.     

The effect of mycorrhiza on the growth and elemental composition of Ni-hyperaccumulating plant Berkheya coddii Roessler

The effect of arbuscular mycorrhizal fungi (AMF) on growth and element uptake by Ni-hyperaccumulating plant, Berkheya coddii, was studied. Plants were grown under laboratory conditions on ultramafic soil without or with the AM fungi of different origin. The AM colonization, especially with the indigenous strain, significantly enhanced plants growth and their survival. AMF affected also the elemental concentrations that were studied with Particle-induced X-ray emission (PIXE). AMF (i) increased K and Fe in shoots, Zn and Mn in roots, P and Ca both, in roots and shoots; (ii) decreased Mn in shoots, Co and Ni both, in shoots and roots. Due to higher biomass of mycorrhizal plants, total Ni content was up to 20 times higher in mycorrhizal plants compared to the non-mycorrhizal ones. The AMF enhancement of Ni uptake may therefore provide an improvement of a presently used technique of nickel phytomining.     

Arsenic accumulation and resistance mechanism in Panax notoginseng, a traditional rare medicinal herb

Panax notoginseng, a traditional rare Chinese medicinal herb, was recently found to bring health risk to consumers, mainly because soil in its major plantation area was contaminated by arsenic (As). We investigated the effect of soil As pollution on the growth and As uptake of pot-cultured P. notoginseng, and the associated mechanisms of As stressed response. Results showed that, comparing with P. notoginseng growing in a low-As soil, the root, stem, and leaf biomasses of those growing in a high-As soil significantly reduced by 0.75, 0.09 and 0.21 g seedling⁻¹, respectively. Arsenic concentrations in roots, stems and leaves of the seedlings growing in high-As soil were 22, 15 and 3 times higher than those growing in low-As soil, respectively. Regardless of the soil As concentration, As existed in plants mainly as As(III), suggesting that the reduction of As(V) is a key step in As metabolism. Arsenic was distributed primarily in cell walls (51.7% for plants growing in the low-As soil, and 51.5% in the high-As soil), followed by cytoplasm supernatant, with cell organelles containing the least As. Compared with plants growing in the low-As soil, those in the high-As soil had increased superoxide dismutase and peroxidase activities in their roots, stems, and leaves, which would be associate with improving the resistance of P. notoginseng to As stress. The results suggest that there exists some special mechanisms of As-tolerance in P. notoginseng and the study is of significance in developing measures to reduce As in the herb.     

The impact of EDTA on lead distribution and speciation in the accumulator Sedum alfredii by synchrotron X-ray investigation

The in vivo localization and speciation of lead (Pb) in tissues of the accumulator Sedum alfredii grown in EDTA-Pb and Pb(NO₃)₂ was studied by synchrotron X-ray investigation. The presence of EDTA-Pb in solution resulted in a significant reduction of Pb accumulation in S. alfredii. Lead was preferentially localized in the vascular bundles regardless of treatments but the intensities of Pb were lower in the plants treated with EDTA. Lead was predominantly presented as a Pb-cell wall complex in the plants regardless of its supply form. However, a relatively high proportion of Pb was observed as Pb-EDTA complex when the plant was treated with EDTA-Pb, but as a mixture of Pb₃(PO₄)₂, Pb-malic, and Pb-GSH when cultured with ionic Pb. These results suggest that EDTA does not increase the internal mobility of Pb, although the soluble Pb-EDTA complex could be transported and accumulated within the plants of S. alfredii.     

Microwave irradiation and citric acid assisted seed germination and phytoextraction of nickel (Ni) by <Emphasis Type="Italic">Brassica napus</Emphasis> L.: morpho-physiological and biochemical alterations under Ni stress

The complex bio-geochemistry of soil allows pollutant to persist for a longer period of time which further decreased the fertility and natural composition of land. Nickel, an inorganic pollutant, coming from a wide range of industrial and manufacturing units possesses serious threat to soil degradation and crop productivity around the world. The present study was carried to evaluate the combined role of microwave irradiation (MR) and citric acid (CA) on the phytoextraction potential of Brassica napus L. under Ni stress. An initial seed germination test was conducted to select effective time scale of MR exposure. Highest seed germination was observed at exposure of 2.45 GHz frequency for 30 s. Healthy seeds of B. napus L. genotype Faisal Canola (RBN-03060) treated with MR at 2.45 GHz for 30 s were sown in plastic pots filled with 5 kg of soil. Nickel and CA applied exogenously in solution form with different combinations to both MR-treated and untreated B. napus plants. The MR-treated plants showed higher growth, biomass, photosynthetic pigments (Chl a, b, total, and carotenoids) and activities of antioxidant enzymes (SOD, POD, APX, CAT) as compared to untreated plants who showed higher reactive oxygen species (MDA, H₂O₂) and electrolyte leakage. Increasing Ni concentration significantly decreased the physiological and biochemical attributes of B. napus both in MR-treated and untreated plants. The addition of CA alleviated Ni-induced toxic effects in both MR-treated and untreated plants by improving antioxidant defense system. The degree of Ni stress mitigation was higher in MR-treated plants. The Ni concentration was higher in root, stem, and leaves of MR-treated plants under CA application as compared to untreated plants. The present study concluded that seeds treated with MR before sowing showed higher accumulation and concentration of Ni from soil, and this phenomenon boosted with the application of CA.     

Removal of Ni(II) and Cu(II) ions using native and acid treated Ni-hyperaccumulator plant Alyssum discolor from Turkish serpentine soil

Alyssum discolor biomass was collected from serpentine soil and was used for removal of metal ions. The plant species grown on serpentine soils are known to be rich with metals ions and thus have more capability for accumulating heavy metals. Native and acid-treated biomass of A. discolor (A. discolor) were utilized for the removal of Ni(II) and Cu(II) ions from aqueous solutions. The effects of contact time, initial concentration, and pH on the biosorption of Ni(II) and Cu(II) ions were investigated. Biosorption equilibrium was established in about 60 min. The surface properties of the biomass preparations were varied with pH, and the maximum amounts of Ni(II) and Cu(II) ions on both A. discolor biomass preparations were adsorbed at pH 5.0. The maximum biosorption capacities of the native, and acid-treated biomass preparations for Ni(II) were 13.1 and 34.7 mg g⁻¹ and for Cu(II) 6.15 and 17.8 mg g⁻¹ dry biomass, respectively. The biosorption of Ni(II) and Cu(II) ions from single and binary component systems can be successfully described by Langmuir and Freundlich isotherms. When the heavy metal ions were in competition, the amounts of biosorbed metal ions on the acid treated plant biomass were found to be 0.542 mmol g⁻¹ for Ni(II) and 0.162 mmol g⁻¹ for Cu(II), the A. discolor biomass was significantly selective for Ni(II) ions. The information gained from these studies was expected to indicate whether the native, and acid-treated forms can have the potential to be used for the removal and recovery of Ni(II) ions from wastewaters.     

Application of phosphate-solubilizing bacteria for enhancing bioavailability and phytoextraction of cadmium (Cd) from polluted soil

In this study, phosphate-solubilizing bacteria (PSB), Bacillus megaterium, were used to enhance Cd bioavailability and phytoextractability of Cd from contaminated soils. This strain showed a potential for directly solubilizing phosphorous from soils more than 10 folds greater than the control without inoculation. The results of pot experiments revealed that inoculation with B. megaterium significantly increased the extent of Cd accumulation in Brassica juncea and Abutilon theophrasti by two folds relative to the uninoculated control. The maximum Cd concentrations due to inoculation were 1.6 and 1.8 mg Cd g⁻¹ plant for B. juncea and A. theophrasti after 10 wk, respectively. The total biomass of A. theophrasti was not significantly promoted by the inoculation treatment, yet the total biomass of B. juncea increased from 0.087 to 0.448 g. It is also worth to mention that B. juncea predominantly accumulates Cd in its stems (39%) whereas A. theophrasti accumulates it in its leaves (68%) after 10 wk. The change of the Cd speciation indicated that inoculation of B. megaterium as PSB increased the bioavailabilty of Cd and consequently enhanced its uptake by plants. The present study may provide a new insight for improving phytoremediation using PSB in the Cd-contaminated soils.     

The presence of Bacillus thuringiensis (Bt) protein in earthworms Eisenia fetida has no deleterious effects on their growth and reproduction

Earthworms Eisenia fetida, bred in substances with stover of two genetically-engineered Bacillus thuringiensis (Bt) corns (5422Bt1 (Event Bt11) and 5422CBCL (MON810)) expressing Cry1Ab and their near-isogenic non-Bt corn (5422), were used to investigate the non-target effects of Bt corn on soil-dwelling organisms. Cry1Ab concentrations in substances, casts and guts of E. fetida were also investigated by Enzyme-linked immunosorbent assay (ELISA). More than 90% individuals of E. fetida survived over a period of 30 d, irrespective of whether they received Bt corn or non-Bt corn. Compared to 5422 treatments, significantly higher relative growth rate and more number of new offspring and cocoons of E. fetida were found in 5422Bt1 and 5422CBCL treatments. These results were unlikely to be directly caused by Cry1Ab released from Bt corns but rather by differences in other factors of plants such as plant components (soluble sugar, total organic carbon, total protein and available phosphorus of Bt corns were more than 5422). ELISA results indicated immunoreactive Cry1Ab was detectable in substances, and the casts, guts of E. fetida from Bt corns treatments, of which the highest levels were detected in substances under the corresponding experimental conditions. With the increase of treated time, a strong decline was observed in Cry1Ab from substances and casts of E. fetida, whereas Cry1Ab in guts of E. fetida from 5422Bt1 treatments gradually increased and that from 5422CBCL treatments increased between 14 and 30 d. Therefore, the presence of Cry1Ab in E. fetida had no deleterious effects on their growth and reproduction.     

Accumulation of heavy metals from contaminated soil to plants and evaluation of soil remediation by vermiculite

We evaluated the distribution of 15 metal ions, namely Al, Cd, Cu, Cr, Fe, La, Mn, Ni, Pb, Sc, Ti, V, Y, Zn and Zr, in the soil of a contaminated site in Piedmont (Italy). This area was found to be heavily contaminated with Cu, Cr and Ni. The availability of these metal ions was studied using Tessier’s sequential extraction procedure: the fraction of mobile species, which potentially is the most harmful for the environment, was much higher than that normally present in unpolluted soils. This soil was hence used to evaluate the effectiveness of treatment with vermiculite to reduce the availability of the pollutants to two plants, Lactuca sativa and Spinacia oleracea, by pot experiments. The results indicated that the addition of vermiculite significantly reduces the uptake of metal pollutants by plants, confirming the possibility of using this clay in amendment treatments of metal-contaminated soils. The effect of plant growth on metal fractionation in soils was investigated. Finally, the sum of the metal percentages extracted into the first two fractions of Tessier’s protocol was found to be suitable in predicting the phytoavailability of most of the pollutants present in the investigated soil.     

Trichoderma atroviride F6 improves phytoextraction efficiency of mustard (Brassica juncea (L.) Coss. var. foliosa Bailey) in Cd, Ni contaminated soils

Trichoderma atroviride F6, isolated from decaying feather and resistant to 100 mg l(-1) Cd2+ and 250 mg l(-1) Ni2+, was applied for rhizoremediation of Cd, Ni and Cd-Ni combination contaminated soils through association with Brassica juncea (L.) Coss. var. foliosa. The strain significantly alleviated the cellular toxicity of cadmium and nickel to plants. Inoculation of B. juncea (L.) Coss. var. foliosa with T. atroviride F6 resulted a 110%, 40% and 170% increase in fresh weight in Cd, Ni and Cd-Ni contaminated soils, respectively (P<0.05). The translocation factors and metal bioconcentration factors calculated for the inoculated plant were increased compared to the noninoculated plants. The results indicated that the efficiency of phytoextraction for B. juncea (L.) Coss. var. foliosa enhanced after inoculating with T. atroviride F6. The fungal treated plants grown in Cd-Ni combination contaminated soils showed higher phytoextraction efficiency than those in Cd or Ni contaminated soils. Thus, it is suggested that the fungus T. atroviride F6 endowed with organic-degrading capabilities could be exploited for fungi-assisted phytoremediation of mixed organic-metal contaminated soils.     

The functional and physiological status of Gammarus fossarum (Crustacea; Amphipoda) exposed to secondary treated wastewater

Climate change scenarios predict lower flow rates during summer that may lead to higher proportions of wastewater in small and medium sized streams. Moreover, micropollutants (e.g. pharmaceuticals and other contaminants) continuously enter aquatic environments via treated wastewater. However, there is a paucity of knowledge, whether extended exposure to secondary treated wastewater disrupts important ecosystem functions, e.g. leaf breakdown. Therefore, the amphipod shredder Gammarus fossarum was exposed to natural stream water (n = 34) and secondary treated wastewater (n = 32) for four weeks in a semi-static test system under laboratory conditions. G. fossarum exposed to wastewater showed significant reductions in feeding rate (25%), absolute consumption (35%), food assimilation (50%), dry weight (18%) and lipid content (22%). Thus, high proportions of wastewater in the stream flow may affect both the breakdown rates of leaf material and thus the availability of energy for the aquatic food web as well as the energy budget of G. fossarum.     

Heavy metal concentrations in plants and different harvestable parts: A soil-plant equilibrium model

A mathematical interaction model, validated by experimental results, was developed to modeling the metal uptake by plants and induced growth decrease, by knowing metal in soils. The model relates the dynamics of the uptake of metals from soil to plants. Also, two types of relationships are tested: total and available metal content. The model successfully fitted the experimental data and made it possible to predict the threshold values of total mortality with a satisfactory approach. Data are taken from soils treated with Cd and Ni for ryegrass (Lolium perenne, L.) and oats (Avena sativa L.), respectively. Concentrations are measured in the aboveground biomass of plants. In the latter case, the concentration of metals in different parts of the plants (tillering, shooting and earing) is also modeled. At low concentrations, the effects of metals are moderate, and the dynamics appear to be linear. However, increasing concentrations show nonlinear behaviors.     

Hormetic effect(s) of tetracyclines as environmental contaminant on Zea mays

Animal wastes from intensive pig farming as fertilizers may expose crops to antimicrobials. Zea mays cultivations were carried out on a virgin field, subjected to dressing with pig slurries contaminated at 15 mg L⁻¹ of Oxy- and 5 mg L⁻¹ of Chlor-tetracycline, and at 8 mg L⁻¹ of Oxy and 3 mg L⁻¹ of Chlor, respectively. Pot cultivation was performed outdoor (Oxy in the range 62.5-1000 ng g⁻¹ dry soil) and plants harvested after 45 days. Tetracyclines analyses on soils and on field plants (roots, stalks, and leaves) did not determine the appreciable presence of tetracyclines. Residues were found in the 45-day pot corn only, in the range of 1-50 ng g⁻¹ for Oxy in roots, accounting for a 5% carry-over rate, on average. Although no detectable residues in plants from on land cultivations, both experimental batches showed the same biphasic growth form corresponding to a dose/response hormetic curve.     

Food-chain transfer of zinc from contaminated Urtica dioica and Acer pseudoplatanus L. to the aphids Microlophium carnosum and Drepanosiphum platanoidis Schrank

This study examines the food-chain transfer of Zn from two plant species, Urtica dioica (stinging nettle) and Acer pseudoplatanus (sycamore maple), into their corresponding aphid species, Microlophium carnosum and Drepanosiphum platanoidis. The plants were grown in a hydroponic system using solutions with increasing concentrations of Zn from 0.02 to 41.9 mg Zn/l. Above-ground tissue concentrations in U. dioica and M. carnosum increased with increasing Zn exposure (p < 0.001). Zn concentrations in A. pseudoplatanus also increased with solution concentration from the control to the 9.8 mg Zn/l solution, above which concentrations remained constant. Zn concentrations in both D. platanoidis and the phloem tissue of A. pseudoplatanus were not affected by the Zn concentration in the watering solution. It appears that A. pseudoplatanus was able to limit Zn transport in the phloem, resulting in constant Zn exposure to the aphids. Zn concentrations in D. platanoidis were around three times those in M. carnosum.     

Distribution of PAHs and trace metals in urban stormwater sediments: combination of density fractionation,mineralogy and microanalysis

Sediment management from stormwater infiltration basins represents a real environmental and economic issue for stakeholders due to the pollution load and important tonnages of these by-products. To reduce the sediment volumes to treat, organic and metal micropollutant-bearing phases should be identified. A combination of density fractionation procedure and microanalysis techniques was used to evaluate the distribution of polycyclic aromatic hydrocarbons (PAHs) and trace metals (Cd, Cr, Cu, Ni, Pb, and Zn) within variable density fractions for three urban stormwater basin sediments. The results confirm that PAHs are found in the lightest fractions (d?d??3) whereas trace metals are equally distributed within the light, intermediary, and highest fractions (d?d?d?d?>?2.8 g cm^?3) and are mostly in the 2.3?d??3 fraction. The characterization of the five fractions by global analyses and microanalysis techniques (XRD and MEB-EDX) allowed us to identify pollutant-bearing phases. PAHs are bound to the organic matter (OM) and trace metals to OM, clays, carbonates and dense particles. Moreover, the microanalysis study underlines that OM is the main constituent responsible for the aggregation, particularly for microaggregation. In terms of sediment management, it was shown that density fractionation is not suitable for trace metals but could be adapted to separate PAH-enriched phases.