May 27, 2020

Map Highlights Arsenic in Groundwater Contamination

A new map has highlighted possible hot spots of arsenic contamination in groundwater.

arsenic contamination

As many as 220 million people around the world may be at risk of drinking groundwater contaminated with arsenic, according to a new study published by researchers.

By combining climate, environmental and geologic data with machine learning, the researchers made a global map. The map predicts where groundwater arsenic concentrations are likely to exceed 10 micrograms per liter, which is the safe drinking water limit set by the World Health Organization (WHO).

Previously, a plethora of hot spots of arsenic contamination in groundwater have been identified, including in regions of Bangladesh, Argentina and Vietnam. Nevertheless, data on groundwater arsenic are lacking for many other regions, reported Science News.

To bridge this gap, scientist Joel Podgorski and hydrologist Michael Berg of the Swiss Federal Institute of Aquatic Science and Technology in Dübendorf teamed up to create a high-resolution global risk map based on dozens of different environmental factors, such as temperature, precipitation, soil age and pH.

Podgorski and Berg compiled data from almost 80 studies and then used a machine learning technique called the “random forest” method to create predictions of arsenic risk, according to Science News. The risk is calculated at a resolution of one square kilometer, based on different subsets of the data. The results of about 10,000 different predictions were then averaged together to create the final map, according to Science News.

The map the duo created shows many expected hot spots for arsenic contamination, such as in Asia and South America. It also shows elevated risk in less well-studied regions including: central Asian countries, such as Kazakhstan and Mongolia; countries around the Sahara; as well as in the Arctic.

In the United States, more than a million rural residents may be unknowingly exposed to arsenic contamination in their drinking water wells, according to the researchers. The map created by Podgorski and Berg is not able to predict individual well water arsenic concentrations, however. 

According to Podgorski, the map should be used as a guide to more testing.

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