Arsenic and manganese contamination of drinking water resources in Cambodia: coincidence of risk areas with low relief topography.
Arsenic contamination of groundwater has been identified in Cambodia, where some 100,000 family-based wells are used for drinking water needs. We conducted a comprehensive groundwater survey in the Mekong River floodplain, comprising an area of 3700 km(2) (131 samples, 30 parameters). Seasonal fluctuations were also studied. Arsenic ranged from 1 to 1340 microg L(-1) (average 163 microg L(-1)), with 48% exceeding 10 microg L(-1). Elevated manganese levels (57% >0.4 mg L(-1)) are posing an additional health threat to the 1.2 million people living in this area. With 350 people km(-2) potentially exposed to chronic arsenic poisoning, the magnitude is similar to that of Bangladesh (200 km(-2)). Elevated arsenic levels are sharply restricted to the Bassac and Mekong River banks and the alluvium braided by these rivers (Kandal Province). Arsenic in this province averaged 233 microg L(-1) (median 100 microg L(-1)), while concentrations to the west and east of the rivers were <10 microg L(-1). Arsenic release from Holocene sediments between the rivers is most likely caused by reductive dissolution of metal oxides. Regions exhibiting low and elevated arsenic levels are co-incident with the present low relief topography featuring gently increasing elevation to the west and east of a shallow valley-understood as a relict of pre-Holocene topography. The full georeferenced database of groundwater analysis is provided as Supporting Information.
Buschmann
Johanna
J
Swiss Federal Institute of Aquatic Science and Technology, Eawag, CH-8600 Dübendorf Switzerland, and Resource Development International-Cambodia, RDIC, P.O. Box 494, Phnom Penh, Cambodia.
Berg
Michael
M
Stengel
Caroline
C
Sampson
Mickey L
ML
D000704:Analysis of Variance; D001151:Arsenic / Q000032:analysis*; D002160:Cambodia; D004784:Environmental Monitoring / Q000706:statistics & numerical data*; D005618:Fresh Water / Q000737:chemistry*; D005843:Geography; D006801:Humans; D008345:Manganese / Q000032:analysis*; D013058:Mass Spectrometry; D018570:Risk Assessment; D012621:Seasons; D013050:Spectrometry, Fluorescence; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply / Q000032:analysis*
D014874:Water Pollutants, Chemical; D008345:Manganese; D001151:Arsenic