58 research outputs found
New Symmetries in Crystals and Handed Structures
For over a century, the structure of materials has been described by a
combination of rotations, rotation-inversions and translational symmetries. By
recognizing the reversal of static structural rotations between clockwise and
counterclockwise directions as a distinct symmetry operation, here we show that
there are many more structural symmetries than are currently recognized in
right- or left-handed handed helices, spirals, and in antidistorted structures
composed equally of rotations of both handedness. For example, though a helix
or spiral cannot possess conventional mirror or inversion symmetries, they can
possess them in combination with the rotation reversal symmetry. Similarly, we
show that many antidistorted perovskites possess twice the number of symmetry
elements as conventionally identified. These new symmetries predict new forms
for "roto" properties that relate to static rotations, such as rotoelectricity,
piezorotation, and rotomagnetism. They also enable symmetry-based search for
new phenomena, such as multiferroicity involving a coupling of spins, electric
polarization and static rotations. This work is relevant to structure-property
relationships in all material structures with static rotations such as
minerals, polymers, proteins, and engineered structures.Comment: 15 Pages, 4 figures, 3 Tables; Fig. 2b has error
Phytoremediation of heavy metal-contaminated sites: Eco-environmental concerns, field studies, sustainability issues and future prospects
Environmental contamination due to heavy metals (HMs) is of serious ecotoxicological concern worldwide because of their increasing use at industries. Due to non-biodegradable and persistent nature, HMs cause serious soil/water pollution and severe health hazards in living beings upon exposure. HMs can be genotoxic, carcinogenic, mutagenic, and teratogenic in nature even at low concentration. They may also act as endocrine disruptors and induce developmental as well as neurological disorders and thus, their removal from our natural environment is crucial for the rehabilitation of contaminated sites. To cope with HM pollution, phytoremediation has emerged as a low-cost and eco-sustainable solution to conventional physico-chemical cleanup methods that require high capital investment and labor alter soil properties and disturb soil microflora. Phytoremediation is a green technology wherein plants and associated microbes are used to remediate HM-contaminated sites to safeguard the environment and protect public health. Hence, in view of the above, the present paper aims to examine the feasibility of phytoremediation as a sustainable remediation technology for the management of metals-contaminated sites. Therefore, this paper provides an in-depth review on both the conventional and novel phytoremediation approaches, evaluate their efficacy to remove toxic metals from our natural environment, explore current scientific progresses, field experiences and sustainability issues and revise world over trends in phytoremediation research for its wider recognition and public acceptance as a sustainable remediation technology for the management of contaminated sites in 21st century
Transport and accumulation of heavy metals in undisturbed soil columns
The podzolic soils of the Kola Peninsula, Russia, have in localised areas been highly contaminated with copper and nickel from smelting activities. Migration and retention of these metals were investigated in undisturbed soil columns irrigated with simulated background and polluted precipitation in order to study the temporal processes of retention and release within the soil. The mineral layers were strongly acidified by the contaminated precipitation. Forest floor layers demonstrated a high capacity to retain input Ni and Cu under all conditions. Mineral layers accumulated some Cu, but released Ni. In general, Ni leached through the soil faster than Cu. Since metals are strongly retained in the forest floor layer, even after reduction or cessation of inputs there may be a significant longâterm risk of their leaching to deeper soil
and groundwater. This risk cannot be ameliorated without remediative intervention
Sulphur behaviour in forest soils near the largest SO2 emitter in northern Europe
The impact of 60 a of SO2 emissions from a Ni-Cu plant in the Kola Peninsula (Russia) on soil S contents was assessed in podzols under pine forests. Sulphate desorption and the possible delay of acidification reversal was investigated, because the plant will be reconstructed in 2006 with an expected emission reduction of 90%. Sites were sampled along a pollution gradient in the prevailing wind direction from 1 to 66 km. The investigated podzols stored S mostly in the organic form. The concentrations of total and organic S in soil organic horizons tended to be higher near the smelter but were only weakly correlated with S deposition. No relationship between distance to smelter and S contents was found for the mineral horizons. Sulphate content and desorption behavior were highly variable due to natural variations of texture and extractable Al and Fe contents of the soils. The lack of a clear strong trend with distance from the smelter except in the organic layer indicated that long range transport and diffuse input of SO4 played a major role rather than point source impact. It was concluded that biological turnover is most likely the regulating process in these soils and thus low to medium release of SO4 is expected under decreasing deposition scenarios because organic S was the dominant fraction of total S in all soils. (c) 2007 Elsevier Ltd. All rights reserved
RESTORATION OF VEGETATION ON MINE LANDS NEAR MONCHEGORSK (MURMANSK REGION, RUSSIA)
Background. The increasing technogenic pollution actualizes the restoration of vegetation cover in
many industrial regions of the planet, including the vicinity of non-ferrous metallurgy enterprises in the Kola Subarctic.
The barrens podzols and abrazemes are unfavorable for plant development. The study is aimed at assessing
the restoration of vegetation as a result of the mine lands remediation near the Severonickel industrial complex.
Materials and methods. Remediation was carried out in 2003â2008 by two methods: chemophytostabilisation
(without pretreatment of the soil) and overlapping of contaminated soils with organic matterârich cover materials
followed by liming, fertilization, seedlings planting and grass mixture sowing. The species composition and the
projective cover of the vegetation, the vital status of the undergrowth, the aboveground phytomass of the
ground cover and the thickness of the upper soil layer were evaluated at 11 monitoring sites taking into account
spatial variation. Areas of barren lands were considered as control. For the evaluation and graphical display of the
characteristic features of the vegetation variability, the principal component analysis (PCA) was used. Results.
According to the state of the vegetation, the chemophytostabilisation sites only slightly differ from the control
barrens sites due to adverse edaphic conditions. Planted trees and shrubs have a strongly depressed appearance
and a low projective cover, and the ground cover is not restored. On remediation sites with organic matterârich
fertile layer, sparse deciduous young stands are formed with a predominance of goat willow and / or fluffy birch,
with a higher level of tree vitality and species diversity, grass cover with the participation of grass and / or horsetail.
The PCA revealed an objective fractioning of sites according to the vegetation condition depending on the
remediation technology. Conclusions. Successful restoration of vegetation in mine lands in conditions of emissions
reduction depends on the state of the soil and the technology used. Environmentally friendly and cost-effective
chemophytostabilisation gives only a short-term effect that needs continuous maintenance. A more promising but
expensive way to quickly restore the barren lands is to apply a constructed fertile layer to the surface of polluted
soils in combination with the planting of deciduous trees and the sowing of perennial grasses
- âŚ