Toxic water is poisoning the people of Bangladesh: can a student's science project help save their lives?
One third of Bangladesh's drinking wells are polluted with dangerously high levels of arsenic (see map, p. 20). This element, which occurs naturally in Earth's crust, leaches into groundwater from soil and rocks. Soils in some areas of the world contain more arsenic (As) than others, and Bangladesh is an arsenic hot spot. For people who drink the tainted water there, arsenic poisoning can spell sickness--and even death. Expensive chemical treatment processes can remove arsenic from water, says Charles Sorber, an environmental engineer at the University of Texas. But many poor countries, like Bangladesh, can't afford to properly treat drinking water.
After reading about Bangladesh's arsenic crisis in the August 2004 issue of Scientific American magazine, Katie VanderWeele, a teen from Oregon, decided she wanted to help. "The water these people are drinking has arsenic in it that will cause them to die of cancer," says Katie, who is now 16 years old. "They don't have clean water that they can drink. I wanted to do something that could have some use in the world." So the sophomore at Oregon Episcopal School in Portland, Oregon, designed a science experiment to find a cheap way to remove arsenic from drinking water.
She researched the issue and learned that some plants naturally absorb toxins. Scientists had tested the ability of various plants, including water hyacinths, to mop up arsenic from contarainated soil. But they had stopped short of trying to use plants to filter the element out of the water: So Katie decided to see if water hyacinths could decontaminate poisoned water:
Katie's science project won her a place as the U.S. representative to the 2005 Stockholm Junior Water Prize competition in Stockholm, Sweden. And her results may help doctors and scientists save the lives of the up to 50 million people affected worldwide by arsenic-contaminated drinking water.
WHAT'S THE PROBLEM?
Many people in Bangladesh lack running water in their homes. As a result, it was once common for them to drink water from lakes and streams. But this water contained unsafe levels of microbes, and bacterial infections were killing thousands of children.
In the 1970s--in an effort to lessen its country's water woes-Bangladesh's government joined forces with international aid agencies to install wells that collect water from aquifers, or natural stores of water below Earth's surface. But not long after people in Bangladesh began getting water from wells, some; Bangladeshis began to Complain of painful sores on their hands and feet.
It turned out that the painful lesions were caused by overexposure to arsenic. This toxic element builds in the body's tissues over time, leading to arsenicosis. The sickness can include difficulty swallowing, thirst, low blood pressure, convulsions, cancer, and eventually death.
Following the reports of arsenicosis, scientists went to work to find the arsenic source. They discovered high levels of the toxic element in Bangladesh's aquifers that are less than 75 meters (246 feet) deep (see Nuts & Bolts, right). As people were quenching their thirst, they also were sealing their fate.
Further investigation has revealed that about 30 percent of wells in Bangladesh contain arsenic levels of more than 50 micrograms per liter ([micro]g/L) of water, and 5 to 10 percent of the country's wells test at levels of more than 300 micrograms per liter. That's bad news, considering that the World Health Organization has determined that more than 10 micrograms of arsenic per liter of water is unsafe.
HERE'S A THOUGHT
Katie knew that for a water-treatment plan to be successful in Bangladesh, it would have to cheaply remove arsenic from well water: Scientists had already found that water hyacinths are hyperaccumulators. That means the plants suck up elements like arsenic from soft and store them in their tissues. Katie wondered: Could the plants remove arsenic from the water?
Water hyacinths grow like weeds in Bangladesh. "They completely cover the ponds," Katie says. "People could collect [the plants] from ponds or grow them themselves." But each plant eventually reaches a saturation point where it can't store any more arsenic. Katie set out to learn exactly how much arsenic a water hyacinth could absorb.
TIME TO EXPERIMENT
To find out what a hyacinth's limit for arsenic absorption is, Katie floated 14 plants in 20 liters (5 gallons) of water. Then, taking all necessary safety precautions, she added arsenic to the water until it equaled 300 micrograms per liter. She let the plants sit in the polluted water for 24 hours, and then she tested the arsenic level of the water. If the plants had absorbed any of the arsenic, she added more arsenic to the water to reach 300 micrograms per liter.
Katie continued that procedure until the tested arsenic level remained at or near 300 micrograms per liter for 24 horn's. She found that after five days, the plants became full and would not absorb any more arsenic. Now Katie is experimenting to find a low-cost way to get rid of the arsenic-filled plants. If the plants were left in the water, the arsenic would eventually kill the plants. Then, as they decomposed, the arsenic would re-enter the drinking water.
Engineer Charles Sorber has high hopes for Katie's research. A water-hyacinth filtering program will require more testing before it gets widely implemented. But he says that Katie has laid the groundwork for such a program. "If thousands of others were to pick up projects like [Katies], we'd live in a better world," Sorber says.
Nuts & Bolts
In Bangladesh, arsenic occurs in shallow clay deposits. There, it dissolves in underground water. When people tap into shallow aquifers, they pump up arsenic-laced water. Look at the diagram: Past what depth is the average arsenic concentration lowest?
Where Is The Arsenic?
At least 35 million people in Bangladesh are drinking water that contains potentially deadly levels of arsenic. Scientists believe that the arsenic accumulated in regions of Bangladesh where major rivers washed soil down from the mountains to the Bay of Bengal. Look at the map:
Where are arsenic levels highest?
EARTH DAY ACTION
Are there any water-quality concerns in or around your community? Research to learn more about them. Then try to come up with ideas for how you could solve the problem, or educate others in your community about the issues.
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|Title Annotation:||Katie VanderWeele does research for removing the arsenic naturally|
|Date:||Apr 17, 2006|
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