Details

Autor(en) / Beteiligte

• Al-Shiyab, Safwan Mahmoud Ahmad

Titel

Bioavailability of mercury in soil and solution culture and its effect on plant physiological status during phytoremediation

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2007

Link zum Volltext

• ProQuest

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• There is much concern about the clean up of toxic pollutants in the environment. Mercury (Hg) is one of the most significant environmental contaminants and health concerns. Phytoremediation is a process of using environmentally-friendly and cost-effective technology, to clean up heavy metals and other toxic compounds from contaminated environments. Mercury contamination is ubiquitous in the Y-12 watershed of Oak Ridge, (Tennessee), and has been identified as a key contaminant in soil, sediment, surface water, and ground water. The objectives of this study were to apply the technique of phytoremediation to remediate mercury-contaminated soil and to study the phytoremediation process, including metal uptake, complexation, and translocation by microscopy, chemical analysis, and spectral reflectance. Two types of Indian mustard (Brassica Junicces L.), 'Florida Broadleaf' and 'Long Standing' and 'Chinese Brake Fern' (Pteris Vittata) were tested by applying phytoremediate soils contaminated with various forms of mercury (mercury chloride, mercury nitrate, and mercury sulfide). Indian mustard had a higher capacity to uptake and translocation of Hg from contaminated soils than did 'Chinese Brake Fern'. Results of this study indicate that Hg at a higher concentration has a profound impact on physiology and internal structure of plants, which in turn affect the spectral reflectance. Mercury from initial HgCl2-contaminated soils was more phytotoxic than Hg(NO3)2 and HgS-contaminated soils due to fast uptake and increased accumulation in plant tissues. Mercury accumulation was greater in roots than shoots; this discovery indicates that Hg is not easily transferred into shoots from roots. High concentrations of mercury in plants can interfere with physiologically important functions, cause an imbalance of nutrients, and have detrimental effects on the synthesis and functioning of biologically important compounds, such as enzymes. The total activity of catalase, superoxide, peroxidase, and lipid peroxidation increased in shoots after Hg treatments. H2O 2 content decreased in mercury-stressed plants compared to the control. Physiological changes in these plants caused by uptake and accumulation of Hg were investigated. At high concentrations (HgCl2-1000 ppm), plants showed a reduction in the number of palisade and spongy parenchyma cells and in cell size of leaves. The soil moisture regime strongly affects mercury redistribution. Compared with air-dry regimes, soils at the saturated paste and field capacity regimes had higher mercury, resulting in the more complete movement of mercury toward stable fractions. Key words. Phytoremediation, mercury, microscopy, spectral reflectance, antioxidant enzymes, H2O2, lipid peroxidation, 'Indian mustard' and 'Brake fern', soil fractions.