1 Microbial transformation of arsenic K. Fukushi 1 , T. Hashimoto 2 , S. M. A. Islam 3 , and K. M. Hassan 2 1 Integrated Research System for Sustainability Science (IR3S), The University of Tokyo 2 Department of Urban Engineering, The University of Tokyo 3 Department of Civil Engineering, Dhaka University of Engineering and Technology (DUET) Asian Science and Technology Seminar (ASTS) in Thailand, March 10-11, 2008
Background and Introduction 2 Arsenic contamination from natural aquifers Arsenic leaching problem from mine tailings
Arsenic contamination of soil 3 � Continued cropping with arsenic contaminated irrigation water increases the extent of contamination in agricultural land � A large amount of arsenic as high as 10 kg/ha per year is cycled through irrigated water in Bangladesh (DPHE/BGS 2000) � Some recent studies observed considerable arsenic concentration in rice and vegetables grown on arsenic
Bangladesh groundwater by electrical Irrigating As contaminated 2003 September, Photo taken by Ken Fukushi pump 4
Green: Not contam inated Red: Contam inated ( Bangladesh) 5
Arsenic Iron Removal Process (AIRP) 6 Bangladesh 2003 September, Photo taken by K. Fukushi
Relationship between arsenic concs. in soil and groundwater 7 90 Soil arsenic concentration 80 Huq et al [14] 70 Islam et al [18] 60 (mg/kg) 50 40 30 20 10 0 0 0.2 0.4 0.6 0.8 1 Water arsenic concentration( mg/kg)
Arsenic from mine tailing 8 Thailand 2000 October, Photo taken by Ken Fukushi
9 ヒ 素汚染地域遠景 ヒ 素汚染表層水 Polluted area Polluted surface water ヒ 素汚染表層水 ヒ 素汚染河川水 Polluted surface water Polluted surface water Thailand
Transformation of arsenic in natural environment 10 Air Arsenite Arsenite Methylarsine Methylarsine Trimethylarsine Dimethylarsine Dimethylarsine Arsine Arsine (TMA) (TMA) (DMA) (DMA) Rain Rain Trimethylarsine Trimethylarsine Water Arsenate Arsenate Arsenite MMA MMA oxide (TMAO) DMAA DMAA Bacteria CH CH3 CH3 CH Bacteria Bacteria OH OH Methylarsenic Methylarsenic Dimethylarsenic Dimethylarsenic Soil Arsenate Arsenate Arsenite Acid (DMAA) Acid (MMAA) Bacteria Bacteria Bacteria Bacteria Bacteria Sediment Sediment
Bio-Methylation-mechanism 11 Methyl Methyl Dimethyl Trimethyl Arsenate Arsenate arsonate arsonate arsinate arsine oxide reduction reduction reduction reduction methylation methylation methylation Dimethyl Methyl Methyl Trimethyl Arsenite Arsenite arsinite arsonite arsonite arsine Proposed for C. humicola
Bio-Methylation As(V)-As(III) reduction 12 R 1 = R 2 = OH, arsenate; R 1 = CH 3 , R 2 = OH, methylarsonate; R 1 = R 2 = CH 3 , dimethylarsinate methylation reduction Glutathione (GSH) provides the electrons for reduction and probably methylcobalamin is the methyl donor for anaerobic microorganisms
APPLICATION FOR CLEANUP 13 � High efficiency of methylation � Up to 100 times comparing over the natural condition by mixed culture � Up to 1000 times comparing over the natural condition by pure culture1313 � Application examples � Soil � Sludge from water treatment � Other solids containing arsenic 13
Arsenic Iron Removal Process (AIRP) 14 Bangladesh 2003 September, Photo taken by K. Fukushi
Arsenic removal technology 15 � Arsenic Iron Removal Plant: AIRP � Arsenic in groundwater is complexed with ferric hydroxide and removed with sand filter diagram As sludge Need proper disposal
16 ARSENIC VOLATILIZATION To be dispersed MMA DMA TMA As(V) As(III) B.P.: 2 ℃ B.P.: 36 ℃ B.P.: 52 ℃ Purification process LD 50 16 4.5 1000 1800 8000 (mg/ kg) Relative １ 3.6 0.016 0.009 0.002 Toxicity
dispersion Soil remediation Rain Rain 17 Volatilization Ocean Arsenic polluted soil As High toxicity Low toxicity Microbial transform As (solid/liquid) (gas) 17 As As As As As As
converted in gas % of total arsenic 2.0 1.6 1.2 0.8 0.4 0.0 Arsenic gasification rate in soil 140 augmentation 120 Cumulative time (Days) after 100 before augmentation 80 60 40 20 column 0 2.4 2.0 1.6 1.2 0.8 0.4 0.0 (µgAs/d) MMA production rate 18
NATURAL EMISSION OF GASEOUS ARSENIC 19 � In order to promote arsenic methylation technology for environmental clean-up, we need to know natural arsenic emission level from earth. � Natural emission of gaseous arsenic from earth is biologically conducted. � Fate of gasified As should be investigated 19
By K. Yoshimura 20
Arsenic cycle on earth (conceptual) 21 * * As III/As V Methylated arsine (TMA)
22 Biological liquefaction of arsenic
Conceptual Arsenic Leaching Mechanism in Groundwater in Response to Organic Matter Shallow Deep Tube W ell Tube W ell 23 As Contaminated Water As Free Water I ndustrial + Agriculture + Household W astew ater Anaerobic Aerobic Organic Biofilm Biofilm Contamination Solid Aqueous Solid Bound Bound As(V,III) Solid As(V) As(V) Bound Buried Organic Sediments As(V) As As As As As NOM NOM Fe( OH) 3 Fe( OH) 3 As As As As NOM As Solid Bound As(V)
Arsenic Leaching: AIRP Perspective Bioleaching of arsenic from the accumulated sludge in AIRP filter bed Instantaneous chemical leaching of arsenic: Competitive binary adsorption As As As As OM As As OM As As As As OM 24 OM As OM Fe( OH) 3 Fe( OH) 3 Fe( OH) 3 As OM Fe( OH) 3 As As As As As As As As As OM OM OM As OM OM As OM Aerobic Biofilm As Anaerobic Biofilm As As Treated Water Sand Filter Gravel Pea-Gravel Sand Gravel Sludge
Biotransformation of arsenic 25 � Gasification by arsenic methylating bacteira (AsMB) � Liquefaction by anoxic organisms � Other biological oxidation/deduction of arsenic � Understanding of natural system of the country/region � Strategy for the adaptation
26 Thanking you Ken Fukushi fukushi@ir3s.u-tokyo.ac.jp
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Bangladesh 28
Latest statistics on arsenic conc in groundwater of Bangladesh 29 Total area in Bangladesh (km 2 ) 147,570 Total population (million) 128 Total number of administrative districts 64 Total number of districts surveyed 60 Total number of districts where arsenic concentration exceeds 0.01 mg/l 52/60 Total number of districts where arsenic concentration exceeds 0.05 mg/l 41/60 Total area where arsenic concentration exceeds 0.05 mg/l (km 2 ) 89,186 (60%) Total population where arsenic concentration exceeds 0.05 mg/l (million) 85 (66%) Median value of arsenic concentration observed in tested samples (mg/l) 0.0108 Maximum arsenic concentration observed in tested samples (mg/l) 1.67
Arsenic concentration in agriculture soil in Bangladesh Sample Locations Location Arsenic 30 (1) Manikgonj concentration (2) Munshigonj (3) Comilla (mg/kg) India 9.8 ± 0.7 (3) 3.9 ± 0.4 (3) Bangladesh 40.4 ± 2.1 (3) Dhaka India (1) 7.0 ± 0.7 (2) India (2) 3.9 ± 0.5 (2) (3) 80.9 ± 4.2 (2) 46.5 ± 2.4 (1) 12.3 ± 1.1 (1) 55.6 ± 3.2 (1) Bay of Bengal 60.1 ± 3.7 (1) Myanmar * Depth of soil 0-50 cm
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