有机物及重金属植物修复研究进展

植物修复技术是近年来发展起来的一种非常有前途的生物治理技术 ,也是当前学术界研究的热点领域 .本文对植物修复的类型 ,植物修复土壤、水体有机污染物、重金属和某些放射性核素的过程、机理及可能影响因子作了概括和详尽讨论 ,并就国内外近年来植物修复技术在污染环境中的应用和研究成果进行了综述     

PHYLOGENETIC VARIATION IN THE TOLERANCE AND UPTAKE OF ORGANIC CONTAMINANTS

An investigation into the phylogenetic variation of plant tolerance and the root and shoot uptake of organic contaminants was undertaken. The aim was to determine if particular families or genera were tolerant of, or accumulated organic pollutants. Data were collected from sixty-nine studies. The variation between experiments was accounted for using a residual maximum likelihood analysis to approximate means for individual taxa. A nested ANOVA was subsequently used to determine differences at a number of differing phylogenetic levels. Significant differences were observed at a number of phylogenetic levels for the tolerance to TPH, the root concentration factor and the shoot concentration factor. There was no correlation between the uptake of organic pollutants and that of heavy metals. The data indicate that plant phylogeny is an important influence on both the plant tolerance and uptake of organic pollutants. If this study can be expanded, such information can be used when designing plantings for phytoremediation or risk reduction during the restoration of contaminated sites.     

VETIVER GRASS,VETIVERIA ZIZANIOIDES: A CHOICE PLANT FOR PHYTOREMEDIATION OF HEAVY METALS AND ORGANIC WASTES

Glasshouse and field studies showed that Vetiver grass can produce high biomass (>100t/tha^?1 year^?1) and highly tolerate extreme climatic variation such as prolonged drought, flood, submergence and temperatures (?15°–55°C), soils high in acidity and alkalinity (pH 3.3–9.5), high levels of Al (85% saturation percentage), Mn (578 mg kg^?1), soil salinity (ECse 47.5 dS m^?1), sodicity (ESP 48%), and a wide range of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Se, and Zn). Vetiver can accumulate heavy metals, particularly lead (shoot 0.4% and root 1%) and zinc (shoot and root 1%). The majority of heavy metals are accumulated in roots thus suitable for phytostabilization, and for phytoextraction with addition of chelating agents. Vetiver can also absorb and promote biodegradation of organic wastes (2,4,6-trinitroluene, phenol, ethidium bromide, benzo[a]pyrene, atrazine). Although Vetiver is not as effective as some other species in heavy metal accumulation, very few plants in the literature have a wide range of tolerance to extremely adverse conditions of climate and growing medium (soil, sand, and tailings) combined into one plant as vetiver. All these special characteristics make vetiver a choice plant for phytoremediation of heavy metals and organic wastes.     

Phytoremediation of Metal-Polluted Ecosystems: Hype for Commercialization

Air, water, and soil are polluted by a variety of metals due to anthropogenic activities, which alter the normal biogeochemical cycling. Biodiversity has been employed widely by both developed and developing nations for environmental decontamination of metals. These technologies have gained considerable momentum in the recent times with a hype for commercialization. The United States Environmental Protection Agency's remediation program included phytoremediation of metals and radionuclides as a thrust area to an extent of 30% during the year 2000. Plants, that hyperaccumulate metals, are the ideal model organisms and attracted attention of scientists all over the world for their application in phytoremediation technology. Metal hyperaccumulators have the ability to overcome major physiological bottlenecks. The potential of hyperaccumulators for phytoremediation application relies upon their growth rates (i.e., biomass production) and metal accumulation rate (g metal per kg of plant tissue). The two primary reasons, that are limiting global application of this technology, are the slow growth rates exhibited by most naturally occurring metal hyperaccumulators and the limited solubility of metals in soils (i.e., the high affinity of metal ions for soil particles). Phytoremediation applications, relevance of transgenic plants for metal decontamination, chelate enhanced phytoremediation, chemical transformation, molecular physiology and genetic basis of metal hyperaccumulation by plants, commercialization hype for the phytoremediation technology are reviewed.     

GENETIC VARIATION AND COVARIATION FOR CHARACTERISTICS ASSOCIATED WITH CADMIUM TOLERANCE IN NATURAL POPULATIONS OF THE SPRINGTAIL ORCHESELLA CINCTA (L.)

Heavy metals can be strong and stable directional selective agents for metal-exposed populations. Genetic variation for the metal-tolerance characteristic “cadmium excretion efficiency” was studied in populations of the collembolan Orchesella cincta from a reference- and a metal-contaminated forest soil. Previously it has been shown that “excretion efficiency” influences tolerance through midgut-mediated immobilization and excretion of toxic metal ions, and that an increased mean excretion efficiency is present in animals inhabiting metal-contaminated litter. In the present research, offspring-parent regressions showed that additive genetic variation for cadmium excretion efficiency was present in the population from the reference site. The heritability estimate was 0.33. In the natural population exposed to heavy metals from an industrial source, additive genetic variation was not significantly different from zero. Differences in the heritability between the reference and the exposed population were not significant. Genetic variation for cadmium excretion efficiency allows for a response to selection in the reference population. Such a response has probably occurred in the metal-exposed population. Half-sib analysis with animals from the reference population was used to estimate genetic variation and maternal effects for excretion efficiency, relative growth rate and molting frequency, and to determine genetic correlations between these characteristics. Additive genetic variation was demonstrated for all three characteristics, heritability estimates were 0.48, 0.75 and 0.46, respectively. Maternal effects were low for excretion efficiency and molting frequency, but may be present for relative growth rate. Phenotypic and genetic correlations among these characteristics were positive. The environmental correlation between relative growth rate and molting frequency was positive, others were negative. Direct selection for any of the characteristics, or genetic correlations between tolerance characteristics and growth characteristics, or both may have caused the responses previously observed in field populations.