Summary for Friday February 19th

Today we continued with water quality with a look at the specifics of the hydrogeology behind the Bangladesh As issue and some of the important considerations that need to be addressed during the mitigation of this ongoing crisis. So, the Bangladesh water crisis:

Basic demographics: Bangladesh is a large country (7th most populous in the world) with a very high population density (the highest of the 'real' countries), a very low rate of adult literacy (47.5% = 164/177 world rank), a very low per capita GDP (~$1,500/cap/year), and one of the shortest average lifespans of countries outside of Africa (~62 years).

Water issue 1: Bangladesh still has very high rates of people dying from digestive diseases due largely to the consumption of water that is contaminated with sewer-related bacteria and roto-viruses. This crisis was addressed during the 1960s and 70s by the World Bank and UNICEF with a program that installed millions (8-10) of simply, often hand-pumped, shallow, 'tube' wells.

Water issue 2: The use of groundwater resulted in a 2-3-fold decrease in diarrheal diseases and has saved 10s of millions of lives; however, the uppermost layer of soils (the top 100m or so) in Bangladesh are naturally rich in As. As a result, 28-35 million (17-22%) Bangladeshis drink water that is above 50ppb (the national standard) and 46-57 million (29-37%) Bangladeshis drink water that is above 10ppb (the WHO standard) (numbers from the WHO). If we combine these numbers with our 'acceptable risk' numbers of 1/100 and 1/600, we can anticipate some pretty dire rates of cancer (30 million/100 = 300,000 deaths and 50 million/600 = 83,000 deaths!)

Water issue 2.5: Bangladesh has high rates of As in the soil and in the groundwater that percolates through these soils. The concentration of As in the water, however, is even greater that would be expected given the As content of the soils. This suggests that there are secondary factors that result in a high environmental availability of As (meaning that the water is really good and taking the As from the soil into solution and delivering it to consumers). A recent study out of MIT suggest that water that is artificially high in organic carbon (due to agricultural activities) increases the environmental availability of As. Recent work by the USGS shows that secondary factors such as pH, dissolved oxygen (DO), and time also play important roles in affecting As availability.

Water issue 2.75: Mitigation of As contamination of groundwater in Bangladesh requires inexpensive, low-tech, culturally-sensitive, approaches. We discussed a number of factors including: deeper wells, large-scale high-tech treatment plants vs. smaller scale, low-tech filtration mechanisms, education and communication, deeper wells, cultural and practical implications of sharing (gender issues, perceived insularity), and rice consumption. While I mentioned the importance of inexpensive filtration mechanisms, I forgot to mention the importance of inexpensive water quality testing mechanisms. Getting your water tested for As in NH is a mere (subsidized) $15- not so much of a bargain if you live in a country with a per capita that is 3% that of the USA.

One additional thing that I want to emphasize is that while it might be nice and convenient to group different water quality issues into categories (toxic metals, agricultural runoff, organic chemicals, et cetera), each individual incidence of compromised water quality has its own individual set of physical, chemical, and geological characteristics (its own personality, if you will.) Likewise, the mitigation strategy for each incidence of compromised water quality has its own unique requirements, limitations, and complexities. The better we understand the underlying physical (chemical, geologic, hydrologic, anthropogenic) problems and the economic, geographic, and cultural constrains of action, the better we will be at improving water quality for everyone.

The quiz questions were (as I recall from memory):

1. What is the dilemma Bangladesh has concerning H₂O?

Microbial surface water pollution and arsenic groundwater pollution

2. What is the amendment to the Superfund Act?

SARA (Superfund Amendments and Reauthorization Act of 1980)

3. What is the Chemical Symbol for Arsenic?

As

4. What is the percentage of people in the US who get water from private wells?

15%

5. What is the percentage of people in GEOL 150 who get water from private wells?

22%

Slides shown in lecture today have been posted as a .pdf to Sakai.

The my maps page has been updated with the locations mentioned in today's lecture.