Arsenic Phytoextraction Research Articles

Hydroxyiminodisuccinic acid (HIDS): A novel biodegradable chelating ligand for the increase of iron bioavailability and arsenic phytoextraction

The influence of biodegradable chelating ligands on arsenic and iron uptake by hydroponically grown rice seedlings ( Oryza sativa L.) was investigated. Even though the growth solution contained sufficient Fe, the growth of rice seedlings gradually decreased up to 76% with the increase of pH of the solution from 7 to 11. Iron forms insoluble ferric hydroxide complexes at neutral or alkaline pH in oxic condition. Chelating ligands produce soluble ‘Fe–ligand complex’ which assist Fe uptake in plants. The biodegradable chelating ligand hydroxyiminodisuccinic acid (HIDS) was more efficient then those of ethylenediaminetetraacetic acid (EDTA), ethylenediaminedisuccinic acid (EDDS), and iminodisuccinic acid (IDS) in the increase of Fe uptake and growth of rice seedling. A total of 79 ± 20, 87 ± 6, 116 ± 15, and 63 ± 18 mg dry biomass of rice seedlings were produced with the addition of 0.5 mM of EDDS, EDTA, HIDS, and IDS in the nutrient solution, respectively. The Fe concentrations in rice tissues were 117 ± 15, 82 ± 8, 167 ± 25, and 118 ± 22 μmol g −1 dry weights when 0.25 mM of EDDS, EDTA, HIDS, and IDS were added to the nutrient solution, respectively. Most of the Fe accumulated in rice tissues was stored in roots after the addition of chelating ligands in the solution. The results indicate that the HIDS would be a potential alternative to environmentally persistent EDTA for the increase of Fe uptake and plant growth. The HIDS also increased As uptake in rice root though its translocation from root to shoot was not augmented. This study reports HIDS for the first time as a promising chelating ligand for the enhancement of Fe bioavailability and As phytoextraction.

Indigenous Plant Species with the Potential for the Phytoremediation of Arsenic and Metals Contaminated Soil

Here we present results of a survey conducted to identify and characterize spontaneously growing arsenic-tolerant plant species of the area around the old arsenic/gold mine in ZlotyStok (Poland), with respect of their potential use in phytoremediation. Plants and soil from their rhizosphere were sampled and analyzed for concentrations of As and accompanying Mn, Fe, Mg, Ca, Al, Cu, Zn, Ba, Pb, Ni, Cs, V, Cr, Sr, Rb, Bi, Mo and U. The soil contained primarily very high As, Pb and Al concentrations (up to 7,451, 1,058 and 31,272 mg/kg respectively). The ability of identified species to modify the amount of bioavailable arsenic in their rhizosphere was determined by single extractions of soil samples with the use of water, phosphate buffer, EDTA, and acetic acid. Although As-hyperaccumulators were not found, Calamagrostis arundinaca was identified as a new species which successfully carried out the natural phytoextraction of arsenic. This plant was able to increase substantially the arsenic availability in the soil, and likely due to efficient uptake decreased the total As concentration within the root zone by around 40% relative to the reference soil. Thus, it has high potential for phytoremediation. The lowest amount of available arsenic was found in the rhizosphere of Stachys sylvatica, the species with the lowest As shoot concentration (compared with other plant species). It was proposed as a good candidate for phytostabilization.

Timing of phosphate application affects arsenic phytoextraction by Pteris vittata L. of different ages

The effects of timing in phosphate application on plant growth and arsenic removal by arsenic hyperaccumulator Pteris vittata L. of different ages were evaluated. The hydroponic experiment consisted of three plant ages (A 45d, A 90d and A 180d) and three P feeding regimens (P 200+0, P 134+66 and P 66+134) growing for 45 d in 0.2-strength Hoagland–Arnon solution containing 145 μg L −1 As. While all plants received 200 μM P, P was added in two phases: during acclimation and after arsenic exposure. High initial P-supply (P 200+0) favored frond biomass production and plant P uptake, while split-P application (P 134+66 and P 66+134) favored plant root production. Single P addition favored arsenic accumulation in the roots while split-P addition increased frond arsenic accumulation. Young ferns (A 45d) in treatment P 134+66 were the most efficient in arsenic removal, reducing arsenic concentration to below 10 μg L −1 in 35 d. The results indicated that the use of young ferns, coupled with feeding of low initial P or split-P application, increased the efficiency of arsenic removal by P. vittata.

Effect of amendment on phytoextraction of arsenic by Vetiveria Zizanioides from soil

The present study was undertaken to evaluate the growth response of Vetiveria zizanioides amended with organic amendments to arsenic (As) in contaminated soils and its ability to sequester As. The test results indicate that the plants exhibited high tolerance to As in the soils and their normal growth continued even though As concentration reached 500 mg/kg. However, when As concentrations in soils were in the range of 1000~2000 mg/kg the plants could not survive no matter whether the soils were amended. The accumulation of As in roots (185.4 mg/kg) was higher than that in shoots (100.6 mg/kg). The As level in the contaminated soil was reduced from 500 mg/kg to 214 mg/kg after six months of As phytoextraction. Microbial population was not affected in the As contaminated soil amended with dairy sludge, mycorrhizae and Azotobacter.

Arsenic and Cadmium Phytoextraction Potential of Crambe Compared with Indian Mustard

ABSTRACT The ability to tolerate and accumulate arsenic (As) and cadmium (Cd) was compared between Brassica juncea (Indian mustard) and Crambe abyssinica (Hochst.) (Crambe or Abyssinian mustard). Plants were grown hydroponically and treated with 70 μM sodium arsenate or 50 μ M cadmium chloride for two weeks. When nutrients were omitted during the As treatment, leaves of C. abyssinica accumulated an average of 140 mg As kg−1, compared with 34 mg kg−1 for B. juncea. When quarter-strength Hoagland's nutrient solution was provided during As treatment, leaves of C. abyssinica accumulated an average of 270 mg As kg−1, compared with 13 mg kg−1 for B. juncea. Cadmium accumulation on a dry-weight basis was approximately two times greater in shoots of B. juncea. Shoot biomass production in the presence or absence of metals was greatest for C. abyssinica. Because of its larger biomass and more efficient accumulation of As, C. abyssinica should be considered for use in phytoremediation research.

Arsenic phytoextraction and hyperaccumulation by fern species

Arsenic (As) is an ubiquitous trace metalloid found in all environmental media. Its presence at elevated concentrations in soils derives from both anthropogenic and natural inputs. Arsenic is a toxic and carcinogenic element, which has caused severe environmental and health problem worldwide. Technologies currently available for the remediation of arsenic-contaminated sites are expensive, environmentally disruptive, and potentially hazardous to workers. Phytoextraction, a strategy of phytoremediation, uses plants to clean up contaminated soils and has been successfully applied to arsenic contaminated soils. It has the advantage of being cost-effective and environmentally friendly. A major step towards the development of phytoextraction of arsenic-impacted soils is the discovery of the arsenic hyper accumulation in ferns, first in Pteris vittata, which presented an extraordinary capacity to accumulate 2.3% arsenic in its biomass. Another fern, Pityrogramma calomelanos was found to exhibit the same hyperaccumulating characteristics. After that, screening experiments have revealed that the Pteris genus is really unique in that many species have the potential to be used in phytoextraction of arsenic. In general, these plants seem to have both constitutive and adaptive mechanisms for accumulating or tolerating high arsenic concentration. In the past few years, much work has been done to understand and improve the hyperaccumulating capability of these amazing plants. In particular, the field of molecular biology seems to hold the key for the future of the phytoremediation.

Arsenic Uptake by Native Fern Species in Thailand: Effect of Chelating Agents on Hyperaccumulation of Arsenic by Pityrogramma calomelanos

Nineteen native fern species collected from an area in Thailand with high arsenic concentration in soil and in ground water as a result of tin mining was screened for elevated arsenic concentration in fronds. Two species of fern were found to contain elevated arsenic in their fronds in nature: Pityrogramma calomelanos (108–1156 µg g−1 dried weight) and Pteris vittata (79 µg g−1 dried weight). Under hydroponic culture Pityrogramma calomelanos (a silver back fern) accumulated arsenic in its shoot at rate of 4616 µg g−1 (dried weight). The accumulation of arsenic in Pityrogramma calomelanos shoot doubled with the addition of an EDTA (Ethelenediamine tetraacetic acid) chelating agent. The highest accumulation occurred 6 weeks after exposure to 10 mg L−1 arsenic as disodium hydrogen arsenate. The addition of another chelating agent, DMSA (Dimercaptosuccinic acid), resulted in a 5-fold decrease in arsenic concentration in the Pityrogramma calomelanos shoot compared to control after 6 weeks of exposure to arsenic. The contrasting effect of the EDTA and DMSA chelating agent was attributed to the strong binding of the thiol group to arsenic ion. This study indicated that Pityrogramma calomelanos uptake and translocate arsenic in the form of arsenate and arsenite rather than the As–DMSA complex. Using phytoextraction efficiency calculations, it was determined that Pityrogramma calomelanos gave the highest arsenic phytoextraction efficiency at 6 weeks after exposure to arsenic in the EDTA treatment, with an efficiency of 77.8 mg As based on whole plant biomass.