ARSENIC CONTAMINATION OF GROUNDWATER AND ITS

70 Pages·2009·1.54 MB·English

ARSENIC CONTAMINATION OF
GROUNDWATER AND ITS
CCOONNSSEEQQUUEENNCCEESS
Dr. S.M. Imamul Huq
Professor
Department of Soil, Water and Environment
&
Founder Director, Bangladesh-Australia
Centre for Environmental Research
E-mail:imamhuqq@@hotmail.com;; web:
www.imamulhuq.com
Backgground
(cid:137) Arsenic contamination of ground water was first reported
eeaarrllyy 11999900ss
As affected patient was thought to be having some kind of
(cid:137)
skin diseases.
DCH identified – Diseases caused byy As inggestion
(cid:137)
Problem of As is new, Although As has been present in GW
(cid:137)
ffoorr tthhoouussaanndd ooff yyeeaarrss
OOrriiggiinn ooff AAss iinn GGrroouunndd wwaatteerr
(cid:137)(cid:137) BBotthh AAntthhropogeniic andd GGeogeniic source
Source of As in Bangladesh soil - Alluvial in nature
(cid:137)
Contamination occurs in GW from Alluvial and Deltaic
(cid:137)
sediments
“Likely source of As in GW : Geogenic”
• Arsenic - Originates from the Greek word –
aarrsseenniiccoonn –ppootteenntt
• Known since 340 BC
•• UUsseess:: DDrruugg oorr ppooiissoonn –hhoommiicciiddaall mmuurrddeerrss;;
pigments, insecticides, herbicides, defoliants,
alloyy in metals,, chemical warfare aggents,, wood
preservatives etc.
• Occurrence:
• in air – 0.005 to 0.1 µg/m3
• in water less than 10 µg/l
• in soil less than 15 mg/kg
• in food less than 0.1 mg/kg
• 10-20 fold increases in As levels above this
bbackkgroundd concentratiion may resullt ffrom
industrial and agricultural inputs
• AAnntthhrrooppooggeenniicc ssoouurrcceess ooff eennvviirroonnmmeennttaall AAss
contamination – fossil-fuelled power plants;
smelting of lead, copper, zinc, and gold ores;
aaggrriiccuullttuurraall uussee ooff aarrsseenniiccaall hheerrbbiicciiddeess aanndd
pesticides
• Globally → 48,000 m t As/yr
• +5 or arsenate: AsO -3, HAsO -2, H AsO - → oxygen
4 4 2 4
rich acidic condition
• ++33 oorr aarrsseenniittee:: AAss((OOHH)) , AAss((OOHH)) -, AAss OO OOHH-2,
33 44 22 22
AsO -3 → moderately reducing anaerobic
3
environment like ground water
Guideline values for As in drinking water
Countryy/orgganization max. contaminant level((CML)) µµgg/L
Australia 7
Canada 25
USEPA 20 (50)
France 50
Germany 1
WHO 10
EEEECC 1100
India 50
China 50
TTaaiiwwaann 5500
Bangladesh 50
Food Crops – 50 ppb
• Toxicity: deopends on : i. Oxidation states
iiii.. CChheemmiiccaall ffoorrmm
iii. Solubility in the biological system
• arsine > inorganic As (III) > organic As (III) > inorganic As
(V) > organic As (V) > arsonium compounds and elemental
arsenic
• aarrsseenniittee iiss 6600 xx mmoorree ttooxxiicc tthhaann aarrsseennaattee wwhhiicchh iiss 7700 xx mmoorree
toxic than methylated species, monomethyl arsonic acid
(MMAA) and dimethyl arsinic acid
• Tolerable daily intake (TDI): amount of substance/kg body
wt. ingested daily over a life time without health risk –
estimated risk ((based on 60 kgg pperson drinkingg 2L/dayy,, for a
life of 70 years) →0.17 µg/L for practical purpose → 10 µg/L
• Global problem: Argentina, Alaska, Chile, China, Mongolia,
HHungary, IInddiia, MMexiico, TThhaiillandd, CCambboddiia, UUSSAA
IInnggeessttiioonn ooff aarrsseenniicc iiss mmaanniiffeesstteedd iinn tthhrreeee
manners in human beings:
• As in urine (recent exposure)
• As in blood (for instant exposure)
• As in skin, hair and finger nails (for chronic
expposure))

Possible pathways of As ingestion by human
Fish
INGESTION Eggs, Meat, Milk
Fish food
Plants Animals
Drinking water Soil water Soil Food chain
Gills
Cooking
Algae
As in tubewell Irrigation
RRuunn ooffff ttoo ffiisshh ppoonnddss
As in sediment
Erosion from Himalayas