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Phytofiltration of arsenic and cadmium from the water environment using Micranthemum umbrosum

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Title: Phytofiltration of arsenic and cadmium from the water environment using Micranthemum umbrosum
Other Titles: Micranthemum umbrosumを用いた水圏環境よりのヒ素及びカドミウムの浄化
Authors: Islam, Md. Shariful Browse this author
Issue Date: 25-Sep-2014
Abstract: Heavy metal pollution in aquatic environment due to natural sources and anthropogenicactivities, is posing a dreadful threat to the human health. Among different heavy metals,arsenic (As) and cadmium (Cd) are the two most toxic and carcinogenic agent that extensivelycontaminates the water bodies. There are some physical and chemical remediation methodsthat have some limitations like high production technology, costly, destruction of native microflora and fauna, and creation of secondary pollutions. In contrast, phytofiltration is a novel,cost effective, environmental friendly, aesthetic and solar-driven technology, using aquaticplants to remove As and Cd from contaminated water without causing any or little secondarypollution. A small number of aquatic plants were identified to uptake contaminants fromaquatic environment. Among them very few could accumulate more than one pollutant intheir bodies. Micranthemum umbrosum (J.F. Gmel) S.F. Blake, commonly known as Waterfern, Baby’s tears, or Pearl grass, belongs to the family Linderniaceae, is one of them, thatsignificantly absorbs both As and Cd from contaminated water.After culturing M. umbrosum for 7 days in a hydroponic experiment, the accumulation ofabout 1220 μg As g-1 and 800 μg Cd g-1 were observed in the leaves, from 1000 μg As L-1 and1000 μg Cd L-1 of water, respectively and it can removed 79.3–89.5% As and 60–73.1% Cdfrom 200 to 1000 μg As L-1 and 300 to 3000 μg Cd L-1 solutions, respectively. Plant andwater samples were analyzed for assessing the As and Cd accumulations, translocations,phytotoxic effects, uptake mechanisms and kinetics, and for evaluating the potential of M.umbrosum as As and Cd phytofiltrator.For As treatment, root to stem and stem to leaf translocation factors greater than 1.0 indicatedthat accumulation of As in leaves was large compared to that in stem and roots but there arelittle differences in accumulation of Cd in roots, leaves and stem. It is easy to clean up aquaticenvironment rather than soil due to most of the soil phytoremediators accumulatedcontaminants in their root parts which is sometimes very difficult to harvest and removal fromthe contaminated soil environment. However, the absorption pattern of As and Cd within M.umbrosum was leaf > stem > root. Bio-concentration factors (2350 for As and 3027 for Cd)for M. umbrosum were higher than for other As and Cd phytoremediators, indicates itshyperaccumulation of As and Cd from contaminated water environment. The analysis of different photosynthetic pigments and macro micro-nutrient concentration within plant bodyindicated that the plant showed more resistance to internal and external As concentrationsthan to that of Cd.Absorption uptake kinetics within M. umbrosum was studied by using Michaelis Mentenequation from different As species like arsenite, monomethylarsinic acid (MMAA),dimethylarsinic acid (DMAA) and Cd. The uptake of inorganic As species was much greaterthan that of organic As and was found at above the substrate concentration. Concentrationdependent arsenite and Cd uptake influx were linear up to 500 μg L-1 and after that decreased,probably due to the toxicological inhibition. However, Cd showed similar uptake pattern tothat of inorganic As species, and the data was better fitted to a non-linear than a linear model.Higher Vmax and lower Km value indicated that this plant has high affinity to uptake inorganicarsenite than Cd, organic MMAA and DMAA; and the uptake order was inorganic arsenite >Cd > MMAA > DMAA.As and Cd uptake mechanism within M. umbrosum was investigated by using Gelchromatography column made from Sephadex G-50 (fractionation range is about 1500-30000MW) and Sephadex G-15 (fractionation range is about 700-1500 MW) beads. After analysisof As, Cd, protein and thiol contents in each 2 mL fractionation collected from gel filtrationcolumn, we concluded that As within plants appeared to involve an induction of thiolsynthesis or binding with low molecular weight substances that have thiol group(s) whereasCd showed a different mechanism to that of As. Amino acid profile studied also showed thatCd uptaking mechanism and binding substances in M. umbrosum is different from algae andother plants which is not phytochelatin or thiol complex formation.M. umbrosum showed good As phytofiltration capabilities without any phytotoxic effects, butit was found to be a moderate accumulator of Cd with some phytotoxic effect and it can lowerthe As toxicity to a level (about 25 μg As L-1) close to the limit recommended by the WorldHealth Organization (10 μg As L-1) but below the limit recommended by Bangladesh andChina Government (50 μg As L-1). So M. umbrosum has the high As and Cd phytofiltrationpotency at low level (500 μg L-1) As and Cd contaminated water and it can be used asornamentation for room in addition to As and Cd accumulation from water, as it is popular as a green aquarium plant, from the aesthetic point of view of phytoremediation.
Conffering University: 北海道大学
Degree Report Number: 甲第11530号
Degree Level: 博士
Degree Discipline: 環境科学
Examination Committee Members: (主査) 教授 田中 俊逸, 教授 古月 文志, 教授 露崎 史朗, 教授 齋藤 健 (大学院保健科学研究院), 助教 藏﨑 正明
Degree Affiliation: 環境科学院(環境起学専攻)
Type: theses (doctoral)
Appears in Collections:学位論文 (Theses) > 博士 (環境科学)
課程博士 (Doctorate by way of Advanced Course) > 環境科学院(Graduate School of Environmental Science)

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