Mayank Varun

Accumulation of uranium by aquatic plants in field conditions: Prospects for phytoremediation

A study was undertaken to determine Uranium concentrations in water and aquatic plants in the uraniferous region of Beiras, Central Portugal. Samples were collected from running water (n=200) at places where aquatic species were observed. Plant samples were collected from 28 species of submerged, free-floating and rooted emergent plants including 2 bryophytes and 1 pteridophyte. Uranium concentrations in surface waters ranged from 0.23 to 1,217 μg L(-1). The aquatic plant species studied, including several previously untested species, exhibited the ability to accumulate U in concentrations many times that of the ambient water. In general submerged plants exhibited higher U content followed by rooted emergent and free floating species. The highest U concentrations were observed in the bryophyte Fontinalis antipyretica (up to 4,979 mg kg(-1)) followed by Callitriche stagnalis (1963mgkg(-1)), Callitriche hamulata (379 mg kg(-1)), Ranunculus peltatus subsp. saniculifolius (243 mg kg(-1)), Callitriche lusitanica (218 mg kg(-1)), and Ranunculus trichophyllus (65.8 mg kg(-1)). In two out of three rooted emergent species U seemed to be preferentially partitioned in rhizome/roots with highest rhizome U content recorded in Typha latifolia (380 mg kg(-1)). Among the free-floating species, the highest U content (42.5 mg kg(-1)) was seen in Lemna minor. The bryophyte F. antipyretica and Callitrichaceae members seem to be promising candidates for the development of phytofiltration methodologies based on U accumulation, abundance and biomass production.

Phytoremedial assessment of flora tolerant to heavy metals in the contaminated soils of an abandoned Pb mine in Central Portugal.

Significant accumulation of heavy metals in soils and flora exists around the abandoned Barbadalhos Pb mine in Central Portugal. Soil and plant samples [49 species] were collected from two line transects, LT 1 and LT 2, in the mineralized and non-mineralized area, respectively to gain a comprehensive picture of heavy metals in soils and flora to assess its potential for phytoremediation. Phytosociological inventories of the vegetation were made using the Braun-Blanquet cover-abundance scale. Metal concentrations in soil ranged from (in mg kg(-1)): 98-9330 [Pb], 110-517 [Zn], 7.1-50 [Co], 69-123 [Cr], 31-193 [Cu], 33400-98500 [Fe], 7.7-51 [Ni], 0.95-13 [Ag], 2.8-208 [As], and 71-2220 [Mn] along LT 1; and 24-93 [Pb], 30-162 [Zn], 3.7-34 [Co], 61-196 [Cr], 21-46 [Cu], 24100-59400 [Fe], 17-87 [Ni], 0.71-1.9 [Ag], 4.3-12 [As], and 44-1800 [Mn] along LT 2. Plant metal content ranged from (in mg kg(-1)): 1.11-548 [Pb], 7.06-1020 [Zn], 0.08-2.09 [Co], 0.09-2.03 [Cr], 2.63-38.5 [Cu], 10.4-4450 [Fe], 0.38-8.9 [Ni], and 0.03-1.9 [Ag] along LT 1; and 0.94-11.58 [Pb], 2.83-96.5 [Zn], 0.12-1.44 [Co], 0.21-1.49 [Cr], 1.61-22.7 [Cu], 4.6-2050 [Fe], 0.51-4.81 [Ni], and 0.02-0.31 [Ag] along LT 2. Plants with highest uptake of metals were: Cistus salvifolius (548 mg Pb kg(-1)), Digitalis purpurea (1017 mg Zn kg(-1) and 4450 mg Fe kg(-1)). Mentha suavolens and Ruscus ulmifolius were seen to hyperaccumulate Ag (1.9 and 1 mg Ag kg(-1), respectively). More metals and higher concentrations were traced in plants from LT 1, especially for Pb and Zn.

Metal contamination of soils and plants associated with the glass industry in North Central India: prospects of phytoremediation

IntroductionThe effect of the glass industry on urban soil metal characterization was assessed in the area of Firozabad, India. A comprehensive profile of metal contamination was obtained in five zones each containing five specific sites.FindingsZn, Cd, and As showed a greater accumulation, whereas accumulation of Ni and Cu was high in limited samples. Positive correlation was found for the metal pairs Cu-Zn, Cu-Co, and Cu-Cr at P < 0.01. Moderate positive correlation was also observed between Zn-Co, Mn-Cd, Mn-As, Pb-As, and Ni-Cu at P < 0.05. Integrated contamination indices indicate that 60% of the sites were heavily contaminated while 28% were moderately contaminated. Phytoremedial potential of native flora (twenty herbs, three shrubs, and two grasses) was also assessed by analyzing their metal uptake. Individual elements displayed remarkably different patterns of accumulation in soils as well as in plants. Mn, Zn, Cu, and As were predominantly partitioned in shoots, Co and Cd in roots while Pb, Cr, and Ni almost equally between shoots and roots. Most plants exhibited capabilities in mobilizing Co, Pb, Cr, and Ni in the root zone.ConclusionPotential phytoextractors include Datura stramonium and Chenopodium murale while phytostabilizers include Calotropis procera and Gnaphalium luteo-album. Poa annua showed potential in both categories. None of the species showed phytoremedial potential for Co and Ni.

Identification of Calotropis procera L. as a potential phytoaccumulator of heavy metals from contaminated soils in Urban North Central India.

Lead and cadmium levels were monitored in soil at fifteen urban (riverbank, roadside, industrial and residential) sites in the north central part of India. Calotropis procera, a hardy xerophytic plant was identified and selected for remedial potential as it was seen growing well at all sites. Root and leaf samples were collected simultaneously with soil samples to assess the characteristics of accumulation and tolerance of Pb and Cd in C. procera. Chlorophyll and phenological studies were undertaken to investigate the health of plants. The overall trend of Pb and Cd content in soil and plant samples was in the order Industrial>Roadside>Riverbank>Residential. The highest uptake of both the metals was observed in plants from industrial sites. Sites with more anthropogenic disturbance like vehicular and machinery exhausts exhibited reduced chlorophyll levels, stunted growth as well as a delayed, shortened reproductive phase. The ratios of Pb in leaves to Pb in soil were in the range of 0.60-1.37; while similar ratios of Cd were in the range of 1.25-1.83. Highly significant correlation coefficients were determined between concentrations of Pb and Cd in the samples with R(2) values 0.839 for soil, 0.802 for leaf and 0.819 for root samples. The strong correlation between the degree of contamination and concentrations of Pb and Cd in plant samples identifies C. procera as an effective heavy metal remediator of contaminated lands coupled with environmental stress.

Phytoremediation of Soils Contaminated with Metals and Metalloids at Mining Areas: Potential of Native Flora

Contaminated soils and residues can be remediated by various methods, such as: removal, isolation, incineration, solidification/stabilization, vitrification, thermal treatment, solvent extraction, chemical oxidation, etc. These methods have the disadvantage of being very expensive and in some cases, they involve the movement of contaminated materials to treatment sites thus, adding risks of secondary contamination [1-3]. Therefore, currently preference is being given to in situ methods that are less environmentally disruptive and more economical. In this context, biotechnology offers phytoremediation techniques as a suitable alternative.

Spatial Distribution of Heavy Metals in Soil and Flora Associated with the Glass Industry in North Central India: Implications for Phytoremediation

The effect of the glass industry on soil metal characterization was assessed at five test sites at five successive distances in a semi-arid area. A comprehensive profile of Zn, Cd, Pb, Ni, Cu, and As levels in soils was obtained. The spatial distribution patterns of integrated contamination indices for these metals show a similar decreasing trend in distribution as we move further from the industrial cluster. There was significant correlation among individual heavy metal concentrations in the soil samples. Integrated contamination indices indicate that 64% of the sites were in the high contamination range and 28% were in the moderate contamination range. A statistically significant difference (P ≤ 0.001) was obtained for each metal on comparing mean metal content among soil samples. Phytoremedial potential of 12 native plant species was also evaluated. Individual elements displayed remarkably different patterns of accumulation in soils as well as plants. Plants established limited capabilities in mobilizing Zn, Pb, Ni, and Cu in the root zone. While Cd, Cu, As, Zn and Pb were predominantly partitioned in shoots, Ni was equally partitioned between shoots and roots. Interestingly, some plants showed a different partitioning trend at higher concentrations of different metals compared to lower concentrations. Potential species for phytoremediation include Calotropis procera (Milk weed), Chenopodium murale (Goosefoot),Poa annua (Annual bluegrass) and Datura stramonium (Thorn apple). None of the species showed phytoremedial potential for Ni and Cu.

Phytoextraction Potential of Prosopis juliflora (Sw.) DC. with Specific Reference to Lead and Cadmium

Root and shoot samples of Prosopis juliflora were assessed for their heavy metal content to evaluate the species as a green solution to decontaminate soils contaminated with lead and cadmium. The highest uptake of both the metals was observed in plants from industrial sites. Sites with more anthropogenic disturbance exhibited reduced chlorophyll levels, stunted growth, delayed and shortened reproductive phase. The ratios of lead and cadmium in leaves to lead and cadmium in soil were in the range of 0.62–1.46 and 0.55–1.71, respectively. Strong correlation between the degree of contamination and concentrations of lead and cadmium in plant samples identifies P. juliflora as an effective heavy metal remediator coupled with environmental stress.

The effect of Plant growth promoting rhizobacteria on the growth, physiology, and Cd uptake of Arundo donax L.

ABSTRACT In this study, plant growth-promoting potential isolates from rhizosphere of 10 weed species grown in heavy metal-contaminated areas were identified and their effect on growth, antioxidant enzymes, and cadmium (Cd) uptake in Arundo donax L. was explored. Plant growth-promoting traits of isolates were also analyzed. These isolates were found to produce siderophores and enzymes such as 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and aid in solubilization of mineral nutrients and modulate plant growth and development. Based on the presence of multiple plant growth-promoting traits, isolates were selected for molecular characterization and inoculation studies. Altogether, 58 isolates were obtained and 20% of them were able to tolerate Cd up to 400 ppm. The sequence analysis of the 16S rRNA genes indicates that the isolates belong to the phylum Firmicutes. Bacillus sp. along with mycorrhizae inoculation significantly improves the growth, the activity of antioxidants enzymes, and the Cd uptake in A. donax than Bacillus alone. Highly significant correlations were observed between Cd uptake, enzymatic activities, and plant growth characteristics at 1% level of significance. The synergistic interaction effect between these organisms helps to alleviate Cd effects on soil. Heavy metal-tolerant isolate along with arbuscular mycorrhizae (AM) could be used to improve the phytoremedial potential of plants.

Utilization and Supplementation of Phytoextraction Potential of Some Terrestrial Plants in Metal-Contaminated Soils

Urban soils are increasingly acting as a sink for a wide range of contaminants including heavy metals due to the rapid pace of development. Zn, Co, Cd, Pb, Cr, Ni, Cu, and As content of soils was quantified in a semiarid urban industrial zone in India. Metal accumulation in flora on site was also evaluated for prospects of phytoremediation. Accumulation of individual metals in soils as well as their uptake and translocation in plants differed. Calotropis procera, Chenopodium murale, and Poa annua were selected to validate their phytoremedial potential at different concentrations of Pb, Cd, and Cu. Possible enhancement of phytoextraction/phytostabilization through soil amendments was also explored. P. annua (for Pb and Cu) and C. murale (for Cd) were categorized as phytoextractors, while C. procera was categorized as a phytostabilizer of Cd. Manure, EDTA, and mycorrhizae were used as amendments, and metal accumulation trends were plant/metal specific in response to all amendments except EDTA, which enhanced metal uptake in all test species.

PAH Contamination of Urban Soils and Phytoremediation

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants, and some are known to be carcinogenic. PAH content of soils from three test sites including a refinery, a dismantled oil depot and a petrol filling station was analysed. Except dibenz(a,h)anthracene, 15 other PAHs were detected. Total PAH concentrations were in the order refinery > petrol filling station > oil depot. PAH levels were higher in the upper layer of soils at all sites. Three-ring and four-ring PAHs were found to be dominant at both depths. In greenhouse study, Cymbopogon jwarancusa and Helianthus annuus were screened for their ability to phytoremediate PAHs. Soil amendments to enhance their potential were also evaluated. Many C. jwarancusa treatments succumbed. In all vegetated treatments, the decline in TPAH levels was not only higher but also more rapid than the unplanted control. Total PAH degradation ranged from 95 to 99 % in C. jwarancusa at 240 DAT (days after treatment) and 75–84 % in H. annuus at 120 DAT. The final reduction of total PAHs in the unplanted control T0 was about 73 %. Rhizodegradation seemed to be the main mechanism of phytoremediation involved. Individual PAH degradation trends differed as did the efficacy of different amendments. Physiological parameters stabilised within 30–60 days of study.