Tuesday March 31, 2020
Home Uncategorized Mystery of ar...

Mystery of arsenic release into groundwater solved


New York: Stanford scientists have solved an important mystery about where the microbes responsible for releasing dangerous arsenic into groundwater in Southeast Asia get their food.

Groundwater in many countries, including India, China, Bangladesh, Myanmar and Vietnam, contains concentrations of arsenic 20 to 100 times greater than the World Health Organisation’s (WHO) recommended limit.

Arsenic is bound to iron oxide compounds in rocks from the Himalayas and gets washed down the major rivers and deposited in the lowland basins and deltas.

Scientists know that in the absence of oxygen, some bacteria living in those deposited sediments can use arsenic and iron oxide particles as an alternative means of respiration.

When they do this, however, the microbes separate the arsenic and iron oxides and transfer the toxin into underlying groundwater.

The mystery in this system, though, is an obvious source of energy that the microbes can tap to fuel the separation process.

“The question that really limits our ability to come up with predictive models of groundwater arsenic concentrations is how and why does the food they use vary across the landscape and with sediment depth,” said professor Scott Fendorf from Stanford.

In their study, Fendorf and his team found that mixing sediments collected from different depths in vials with artificial groundwater revealed that the oxygen-deprived bacteria living in the upper few feet of permanent wetlands were releasing arsenic.

However, water mixed with sediments gathered from the same shallow layers of seasonal wetlands was arsenic free.

The Stanford scientists hypothesized that bacteria residing in the shallow layers of seasonal wetlands were eating all of the digestible plant material during dry periods when sediments are exposed to air and the microbes have access to oxygen.

As a result, no food is left for the microbes when the floods returned, rendering them unable to cleave arsenic particles from iron oxides.

“The arsenic-releasing bacteria living in the shallow regions of seasonal wetlands are ‘reactive’ carbon limited – that is, they don’t release arsenic into the water because there isn’t enough carbon available in a form they can use,” Fendorf explained.

The findings have large-scale implications for projecting changes in arsenic concentrations with land development in South and Southeast Asia and for the terrestrial carbon cycle.

“If you change the hydrology of a region by building dams or levies that change the course of the water, or if you change agricultural practices and introduce oxygen or nitrate into sediments where they didn’t exist before, that will alter the release of arsenic,” Fendorf said.

The findings were published in the journal Nature Geosciences.


Next Story

Ways to Safeguard Yourself From Tuberculosis

World TB Day: Safeguard yourself with preventive tips

Tuberculosis, commonly abbreviated to TB, is a highly infectious disease that primarily affects the lungs. Pixabay


Tuberculosis, commonly abbreviated to TB, is a highly infectious disease that primarily affects the lungs. As per World Health Organization (WHO), TB is one of the top 10 causes of deaths across the globe. Based on its latest report announced in 2019 , 10 million people across the world were infected by TB, out of which 26.90 lakh people had TB in India.

The report further stated that India had maximum number of Drug Resistant TB which is 27 percent of the total 1.30 lakh Drug-Resistant cases!

As per Dr Prashant Chhajed, HOD-Respiratory Medicine, Hiranandani Hospital, Vashi and Fortis Hospital, Mulund, Tuberculosis can affect several organs of the body, such as lungs, gastrointestinal system, brain, bones, pericardium (covering the heart), pleura (covering the lung) and lymph nodes – neck, chest and abdomen.

Pulmonary Tuberculosis is infectious and spreads via airborne transmission. The standard tests to diagnose Tuberculosis are on smear and culture. Smear tests are available quickly and the culture reports can take up to six weeks to detect tuberculosis.

Once Pulmonary Tuberculosis is diagnosed it is recommended to have a good ventilation system at your home. Wikimedia Commons

In recent years, newer molecular tests, such as the CBNAAT/ TB GeneXpert have become available which enable rapid diagnosis even when the smears are negative and one is waiting for the culture reports to come. Furthermore, these molecular tests also enable the rapid diagnosis of Drug Resistant Tuberculosis, the expert said.

Keeping in mind the growing burden of TB in the country and across the globe, the theme of this year’s World Tuberculosis Day which is observed on March 24 is – �It’s Time’. It focuses on building awareness about TB through prevention and cure with an extended aim to make the world TB Free.

“TB is an airborne infection and when someone infected with TB coughs or sneezes, the bacteria is released into the air, thus infecting the environment. When people get sick with Pulmonary Tuberculosis, then the disease can be transmitted to others. Symptoms may occur within the first few weeks or months or years later, some of which include: A persistent cough that lasts three or more weeks, coughing up blood, chest pain, or difficulty while breathing or coughing, rapid weight loss, fatigue, fever, night sweats, and loss of appetite,” Dr Prashant said.

If you witness the above symptoms, you should visit your doctor to get tested and seek requisite treatment.

When people get sick with Pulmonary Tuberculosis, then the disease can be transmitted to others. Wikimedia Commons

Here are the top preventive measures one should observe:

1. Restrict the transmission of the disease from an infected person to a non-infected person – Identify TB patients, avoid close contact with the person; if you do not know if a person has TB but is coughing rapidly, cover your nose and mouth and step away. If similar symptoms arise in yourself, visit your doctor for primary treatment.

2. Once Pulmonary Tuberculosis is diagnosed it is recommended to have a good ventilation system at your home, as TB can remain suspended in the air for several hours by doing so, one can limit the transmission of the airborne disease.

3. Follow good hygiene practices: Cover your mouth with your elbow while coughing or sneezing. Wash your hands frequently with soap and water.

TB can be contracted by anybody, however, those who are at a higher risk include,

Also Read- Find Out How to Wash Your Hands Properly

  • People with a weaker immune system
  • People diagnosed with chronic diseases like Diabetes
  • Those with HIV/ AIDS
  • Persons from lower socio-economic groups driven by factors such as poverty,
  • malnutrition, poor sanitation, etc.
  • Healthcare personnel coming in contact with infected persons (IANS)