bangladesh arsenic contamination

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bangladesh arsenic contamination

Arsenic Contaminated Water in Bangladesh

The Region

Location, Climate, and TopographyBangladesh is a low-lying tropical country in South Asia that shares borders with India and Myanmar. The Ganges, Brahmaputra, and Meghna are three major rivers that converge in Bangladesh, forming a large, fertile river delta that drains into the Bay of Bengal. The climate is influenced by a tropical monsoon season that brings approximately 80% of the country's annual precipitation between the months of June and October. Because of an unpredictable monsoon season and large rivers fed by Himilayan snowmelt, Bangladesh has a complex hydrologic flow regime that is susceptible to heavy flooding. Flood susceptibility is compounded by the fact that 90% of Bangladesh is less than 10 meters above sea level.

Welcome to Bangladesh

The Arsenic Problem

Where Arsenic is Coming From

• ~ 5 cm in diameter• Generally never exceed 200 meters in depth • Steel or iron hand pump at the top/surface of the tube• Problem: Lack of proper water quality tests when building the tube

Why Did Tube Wells Originate?Dating back before tube wells existed, the natural water resources in Bangladesh were infected and polluted with disease causing microorganisms, which posed many healththreats to those drinking the water. Ingesting these microorganisms often caused disease and/or mortality. Therefore, in the 1940s, tube-wells were built to provide clean and safe drinking water to the villages in Bangladesh. This system of obtaining water is supplied by underground aquifers. It wasn’t until the early 90’s, as tube-wells became increasingly abundant, that the arsenic contamination in the water supply became extremely dangerous and prevalent. Now with over millions of tube-wells existing Bangladesh, about 20% of them have arsenic levels in the groundwater exceeded standard World Health Organization limits (>50 microg/L)

How do Most Bangladeshis Obtain Water?

*the arsenic in the water from these towns is 1000x more concentrated than the World Health Organization's acceptable arsenic concentration, which is less than 10 micrograms.

A History of Water Collection

Tube Well Characteristics

o The rocks in the Bangladeshi region contain a higher than average concentration of arsenic in their composition o Over-pumping of aquifers during dry seasons results in the formation of oxygen layers in sediments as water tables lowero Oxygen layers promote the oxidation of pyrite (FeS) and arsenopyrite (FeAsS) found in rocks. Once oxidized, these compounds readily break down into inorganic arsenic.o Erosion of sediments in the Bengal Basin mobilizes these high levels of arsenic and the periodic monsoon season / snowpack-fed river flooding distributes the arsenic widely across the area.o Improper waste disposal and high rates of fertilizer / pesticide runoff further contribute to the arsenic contamination on a local scale

How Arsenic Affects People

*Custom figure created from Flanagan et al. data on a cohort of 115,903 Bangladeshis. It is important to note that this is correlative data; other factors may play an influential role in increased death rates.

Arsenic Contamination in a Global Context

By: Julie Mao & Mark Baumgarten

Arsenic Mitigation

Works Cited

Abstract

*See Attachment


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