Cobalt ferrite nanoparticles (NPs) have received increasing attention due to their widespread therapeutic and agricultural applicability. In the environmental field, dry powder- and ...ferrofluid-suspended cobalt ferrite NPs were found to be useful for removing heavy metals and metalloids from water, while diluted suspensions of cobalt ferrite NP have been promisingly applied in medicine. However, the potential toxicological implications of widespread exposure are still unknown. Since cobalt ferrite NPs are considered residual wastes of environmental or medical applications, plants may serve as a point-of-entry for engineered nanomaterials as a result of consumption of these plants. Thus, the aim of this study was to assess the effects of dry powder and fresh cobalt ferrite NP on wheat plants. Seven-day assays were conducted, using quartz sand as the plant growth substrate. The toxicity end points measured were seed germination, root and shoot lengths, total cobalt (Co) and iron (Fe) accumulation, photosynthetic pigment production, protein (PRT) production, and activities of catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX). Increasing total Co and Fe in plant tissues indicated that wheat plants were exposed to cobalt ferrite NP. Seed germination and shoot length were not sufficiently sensitive toxicity end points. The effective concentration (EC
50
) that diminished root length of plants by 50% was 1963 mg/kg for fresh ferrite NPs and 5023 mg/kg for powder ferrite NP. Hence, fresh ferrite NPs were more toxic than powder NP. Plant stress was indicated by a significant decrease in photosynthetic pigments. CAT, APX, and GPX antioxidant enzymatic activity suggested the generation of reactive oxygen species and oxidative damage induced by cobalt ferrite NP. More studies are thus necessary to determine whether the benefits of using these NPs outweigh the risks.
The aim of this work was to assess the uptake of citrate-coated magnetite nanoparticles (NPs) by wheat plants and its effect on the bioaccumulation and toxicity of individual and joint Cd2+ and Cr6+ ...levels. Seven-day assays were conducted using quartz sand as the plant growth substrate. The endpoints measured were seed germination, root and shoot lengths, and heavy metal accumulation. Magnetite exhibited very low toxicity, regardless of the wheat seedling NP uptake and distribution into roots and shoots. The seed germination and shoot length were not sensitive enough, while the root length was a more sensitive toxicity endpoint. The root length of wheat seedlings exposed to individual metals decreased by 50% at 2.67mgCd2+kg−1 and 5.53mgCr6+kg−1. However, when magnetite NPs (1000mgkg−1) were added, the root length of the plants increased by 25 and 50%. Cd2+ and Cr6+ showed similar and noninteractive joint action, but strongly impaired the wheat seedlings. In contrast, an interactive infra-additive or antagonistic effect was observed upon adding magnetite NPs. Thus, cadmium and chromium accumulation in vegetable tissues was considerately diminished and the toxicity alleviated.
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•We assessed the effect of nanomagnetite on heavy metal toxicity in wheat plants.•Citrate-coated magnetite nanoparticles (NPs) exerted very low toxicity to plants.•Cadmium was more toxic than chromium and toxicity was mitigated by magnetite NPs.•Cadmium and chromium had a similar and noninteractive joint action on plants.•Metals showed an interactive infra-additive joint effect by adding magnetite NPs.
Naturally occurring soil organic compounds stabilize potentially toxic elements (PTEs) such as Cu, Cd, Pb, and Mn. The hypothesis of this work was that an insoluble glycoprotein, glomalin, produced ...in copious amounts on hyphae of arbuscular mycorrhizal fungi (AMF) sequesters PTEs. Glomalin can be extracted from laboratory cultures of AMF and from soils. Three different experiments were conducted. Experiment 1 showed that glomalin extracted from two polluted soils contained 1.6-4.3 mg Cu, 0.02-0.08 mg Cd, and 0.62-1.12 mg Pb/g glomalin. Experiment 2 showed that glomalin from hyphae of an isolate of Gigaspora rosea sequestered up to 28 mg Cu/g in vitro. Experiment 3 tested in vivo differences in Cu sequestration by Cu-tolerant and non-tolerant isolates of Glomus mosseae colonizing sorghum. Plants were fed with nutrient solution containing 0.5, 10 or 20 μM of Cu. Although no differences between isolates were detected, mean values for the 20 μM Cu level were 1.6, 0.4, and 0.3 mg Cu/g for glomalin extracted from hyphae, from sand after removal of hyphae and from hyphae attached to roots, respectively. Glomalin should be considered for biostabilization leading to remediation of polluted soils.
A field study of the natural attenuation occurring in a slag heap contaminated with high available cadmium was carried out. The aims of this research were: to determine plants colonizing this slag ...heap; to analyze colonization and morphological biodiversity of spores of arbuscular mycorrhizal fungi (AMF); to determine spore distribution in undisturbed samples; to know mycelium and glomalin abundance in the rhizosphere of these plants, and to investigate glomalin participation in Cd-stabilization. Forming vegetal islands, 22 different pioneering plant species from 11 families were colonizing the slag heap. The most common plants were species of Fabaceae, Asteraceae and Poaceae. Almost all plants were hosting AMF in their roots, and spores belonging to
Gigaspora,
Glomus,
Scutellospora and
Acaulospora species were observed. Micromorphological analysis showed that spores were related to decomposing vegetal residues and excrements, which means that mesofauna is contributing to their dispersion in the groundmass. Mycelium mass ranged from 0.11 to 26.3
mg/g, which contained between 13 and 75
mg of glomalin/g. Slag-extracted total glomalin was between 0.36 and 4.74
mg/g. Cadmium sequestered by glomalin extracted from either slag or mycelium was 0.028
mg/g. The ecological implication of these results is that organisms occupying vegetal patches are modifying mine residues, which contribute to soil formation.
Mining Ag, Cu, Pb, and Zn sulfides by flotation produces great volume of residues, which oxidized through time and release acid solutions. Leachates from tailing heaps are a concern due to the risk ...of surface water pollution. Hydroxyapatite nanoparticles may remove trace elements from acid leachate collected from an oxidized tailing heap (pH ranged 1.69 ± 0.3 to 2.23 ± 0.16; SO
4
2−
= 58 ± 0.67 to 60.69 ± 0.39 mmol). Based on the batch experiments under standard conditions, the average removal efficiency was 96%, 92%, 86%, and 67% for Cd, Pb, Zn, and Cu, respectively. The Zn adsorption was modeled by the Freundlich equation, but Cd, Cu, and Pb isotherms do not fit to Freundlich nor Lagmuir equations. Adsorption and other mechanisms occur during trace elements removal by hydroxyapatite. In the polymetallic system, trace elements saturate the specific surface of hydroxyapatite in the following order Zn, Cd, Cu, and Pb. The pH values must be higher than 7.5 to adsorb trace elements. The dose of 3.8% of hydroxyapatite to acid mine drainage removed efficiently > 80% of the soluble Fe, Cu, Mn, Zn, Cd, Ni, and Pb: 4020.0, 37.3, 34.8, 432.0, 4.4, 0.7, and 0.11 mg L
−1
from leachate A and 3357.1, 46.6, 27.8, 569.0, 4.7, 0.6, and 1.7 from leachate B, respectively. The application of 0.7% of hydroxyapatite decreased the extractable Pb in unoxidized tailing heaps from 272 to 100 mg kg
−1
. It is likely to use hydroxyapatite to control trace element mobility from mine residues to surrounding soils and surface water.
This work assessed the effect of soil amended with tannery sludge (0, 500, 1000, 2000, 4000 and 8000
mg
Cr
kg
−1
soil), Cr
3+ as CrCl
3·6H
2O (0, 100, 250, 500, 1000 and 2000
mg
Cr
kg
−1
soil), and ...Cr
6+ as K
2Cr
2O
7 (0, 25, 50, 100, 200 and 500
mg
Cr
kg
−1
soil) on wheat, oat and sorghum plants.
Seed germination, seedling growth (root and shoot) and Cr accumulation in dry tissue were measured. Toxicological parameters; medium effective concentration, no observed adverse effect concentration and low observed adverse effect concentration were determined. Root growth was the most sensitive assessment of Cr toxicity (
P
<
0.05). There was a significant correlation (
P
<
0.0001) between Cr accumulation in dry tissue and toxic effects on seedling growth. The three Cr sources had different accumulation and mobility patterns; tannery sludge was less toxic for all three plant species, followed by CrCl
3·6H
2O and K
2Cr
2O
7.
Four sites were selected for collection of plants growing on polluted soil developed on tailings from Ag, Au, and Zn mines at the Zacatecas state in Mexico. Trace element concentrations varied ...between sites, the most polluted area was at El Bote mine near to Zacatecas city. The ranges of total concentration in soil were as follows: Cd 11–47, Ni 19–26, Pb 232–695, Mn 1132–2400, Cu 134–186 and Zn 116–827mg kg−1 air-dried soil weight. All soil samples had concentrations above typical values for non-polluted soils from the same soil types (Cd 0.6±0.3, Ni 52±4, Pb 41±3mg kg−1). However, for the majority of samples the DTPA-extractable element concentrations were less than 10% of the total. Some of the wild plants are potentially metal tolerant, because they were able to grow in highly polluted substrates. Plant metal analysis revealed that most species did not translocate metals to their aerial parts, therefore they behave as excluder plants. Polygonum aviculare accumulated Zn (9236mg kg−1) at concentrations near to the criteria for hyperaccumulator plants. Jatropha dioica also accumulated high Zn (6249mg kg−1) concentrations.
Polygonum aviculare and Jatropha dioica accumulated Zn at concentrations near to the criteria for hyperaccumulator plants.
Phytoremediation is a technology for extracting or inactivating pollutants.
Echinochloa polystachya (H.B.K.) Hitchcock (Poaceae) is a fast-growing perennial grass that is common in tropical areas and ...is often found in oil-polluted soils that contain high concentrations of heavy metals. However, its tolerance to heavy metals, and its ability to accumulate them, has yet to be investigated. Here we test the hypothesis that
E. polystachya is able to accumulate high concentrations of cadmium (Cd). Plants were grown hydroponically with different levels of Cd
2+ (0, 0.25, 1, 2, 10, 50, and 100
mg
L
−1), and were found to be tolerant to Cd
2+ at all levels. No metal-toxicity symptoms were observed at any Cd
2+ level. Root and leaves Cd concentrations were 299
±
13.93 and 233
±
8.77
mg
kg
−1 (on a dry weight basis), respectively. Scanning electron microscopy showed the inclusion of Cd within the xylem; this result was confirmed by energy dispersive X-ray spectrometry. Leaf tissues also accumulated Cd, especially within the bulliform cells of the epidermis. We conclude that
E. polystachya is a hyperaccumulator of Cd. While data for other metals are not yet available,
E. polystachya shows promise in the phytoextraction of Cd from polluted tropical sites.
Mine tailings are a source of contamination to soil, air, and water. Plant leaf surfaces may retain potentially toxic elements and deplete their dispersion. This study aimed to evaluate the potential ...of wild plant species as phytobarriers of areas affected by the dispersion of mine residues. Soil and plant samples were collected from 51 sites. The pseudo-total and DTPA-extractable Cd, Pb, Cu, Zn, and Mn concentrations were measured in soil. Washed and unwashed plant samples were analyzed to calculate the phytobarrier index. High pseudo-total and extractable concentrations of Pb, Zn, and Cd were found in the whole area, and strong influence by mine residues was observed. Twenty-two plant species were able to adsorb dust on leaves.
P
.
lanceolata
,
Cucurbita
spp.,
Medicago sativa
had 5.5, 3.5, and 3.2 times more Pb on the surface than inside the plant. The plants capture particles in different degree. The highest phytobarriers index and widespread sites distribution were observed in S
anvitalia procumbens
(37–48),
Dichondra argentea
(40–62),
Dyssodia pinnata
(34–62),
Aster gymnocephalu
s (32–51),
Flaveria trinervia
(39–47),
Jatropha dioica
(32–48), and
Brickellia veronicifolia
(32–70). The plant species have different abilities to catch particles according to the specific site conditions where they were growing. Probably, native plant species may serve for air phytoremediation near the mine tailings at arid and semiarid areas.
