The phytoremediation, with industrial hemp (Cannabis sativa), of a Hawaiian silty clay soil contaminated with two polycyclic aromatic hydrocarbons (PAHs), chrysene and benzo[a]pyrene, was studied. Hemp showed a very high tolerance to the contaminants. The growth rates of hemp, compared with control, in soils fortified with chrysene and benzo[a]pyrene at concentrations of each varying from 25 to 200 micrograms/g were consistently above 100%. The plants grew from seed for 45 days in soil fortified with PAHs at concentrations of 25, 50, and 75 micrograms/g. Controls were pots with contaminated soil but no plant. PAHs levels were significantly reduced in all pots (control and seeded pots), expect for one set at a high concentration of chrysene, which may be due to uneven spiking. A time course study over 28 days was done to monitor changes of microbial count and levels of chrysene. Little changes were observed for the total microbial count in the soil, and the concentration of chrysene in the soil decreased slightly in the pots containing plants. However, the chrysene levels in those pots were consistently lower than those in the pots without plants.
Elevated levels of polycyclic aromatic hydrocarbons (PAHs) were found in dredged marine sediment from Pearl Harbor. The degradation of PAHs was investigated with soil-sediment systems (washed and unwashed) and 20 plant species. Marine sediment was diluted with native soil in the first experiment. Sediment was washed with gypsum solution and water in the second and third experiments, respectively, prior to soil dilution. Soil dilution ratios were 0, 6, 16, and 37% by weight in the first experiment, 0, 37, 64, and 100% in the second and 0, 18, 64, and 100% in the third. Seven tree, nine shrub, and four grass species were grown for 12 weeks in a glasshouse. A "no plant" control was used in all the experiments. Several plant species yielded up to 90% PAH degradation in the first experiment when compared with no plant control. In the second planting, dwarf hau (Hibiscus tiliaceus) and vetiver (Vetiver zizanoides) appeared to cause the greatest PAH reduction, while paspalum (Paspalum vaginatum) and naupaka (Scaevola sericea) did not. The greatest difference between control and planted soil for both benzo[a]pyrene and total PAH occurred at the highest sediment ratios.
Phytoremediation is an emerging remediation technology that utilizes plants and microbes INTRODUCTIONPhytoremediation is an emerging multidisciplinary field of science and technology. It uses plants and associated microbes to cleanse chemically contaminated air, soil, and water. Research activities to advance the science and technology have been carried out in the past decade. Several of its applications are phytoaccumulation, phytovolatilization, phytotransformation, rhizosphere filtration, and phytostabilization.The technology is a permanent treatment option, has low capital and energy costs, and is aesthetically pleasing (U.S. Environmental Protection Agency [USEPA], 2000). It is, however, often incapable of dealing with high chemical concentrations, and is slower than and requires greater land area than alternative treatment methods. A generally accepted hypothesis is that phytoremediation is suitable in warm climates.This encourages research, demonstration, and application of phytoremediation in tropical and subtropical areas.The use of native plants for phytoremediation in Hawaii has a particular appeal, as they are compatible with the island ecosystems.Their use is feasible and alleviates concerns due to a possible introduction of invasive species into fragile ecosystems.In general, advances of phytoremediation were reviewed recently with an emphasis on various aspects. (2003) and Pulford and Watson (2003) reviewed recent progress of heavy metal remediation, the latter specifically addressing the use of trees. Susarla et al. (2002) appraised the treatability of organic contaminants using phytoremediation. Glass (1999) estimated that the U.S. phytoremediation market for 1999 would be between $30-$49 million. Estimated 1999 world phytoremediation markets were $34-$58 million.The focus of this article is recent progresses and advances of phytoremediation in Hawaii, particularly those conducted at the University of Hawaii.The data summarized can serve as a useful database for future investigations on phytoremediation.There are many unseen risks in the Hawaiian Islands. Heavily contaminated areas include several notable Superfund sites such as Pearl Harbor. Further, many thousands of hectares of agricultural land have received large numbers of pesticide applications. A former pesticide mixing and loading site on Oahu contains dioxins (CERCLIS HISFN0905536). A historical military use of the islands has resulted in live-fire areas with explosive residues. Everyday activities also result in pollution, which may be ameliorated through phytoremediation.Wastewaters from various sources often prove to be a challenge to individuals, industries, and municipalities.Trade winds, Hawaii's natural "air conditioner," can scour landscapes, preventing revegetation on previously cleared lands, and the volcanic soils of the islands historically have metal concentrations that often exceed regulated maximum contamination levels.Bench-, pilot-, and field-scale phytoremediation studies have been conducted for several sites and cont...
Peroxidases and other lignin-degrading enzymes and chemicals can potentially degrade persistent pollutants. Fifty vascular plant species were hydroponically tested for the capability of decolorization of Poly R-478, a lignolytic indicator dye. The top six species that had less than 50 percent of control color at the end of the experiments were Pennisetum purpureum, Rumex crispus, Fimbristylis cymosa, Eleocharis calva, Hibiscus furcellatus, and Cyperus javanicus, in an order from high to low decolorization activity. F. cymosa, E. calva, and C. javanicus are in the Cyperaceae family. Extracellular peroxidase activity was found in vascular plants and correlated to decolorization of polymeric dyes. The plant R. crispus provided the highest guaiacol peroxidase enzyme activity among four of the top six plant species. The Poly R-478 decolorization could be used as a fast screening technique for vascular plants that may have phytoremediation capability.
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