Beyond Carbon Dioxide

Plants Absorb More Pollutants Than Thought

Plants soak more atmospheric pollutants than thought. A study by US scientists shows that apart from carbon dioxide, plants rid the air of volatile organic compounds, or VOCs, the most abundant class of carbon based chemicals in the atmosphere.

Automobile exhaust, coal burning and industry are some of the major sources of VOCs that cause respiratory diseases. 'In the atmosphere they combine with nitrogen oxides to form organic nitrates, a particulate matter responsible for the haze during air pollution, " said Thomas Karl, scientist at the National Center for Atmospheric Research in USA, who led the study.

VOCs also combine with oxygen to form tiny airborne particles called oxygenated VOCs, which insulate the atmosphere and lead to warming.

Scientists had long suspected that plants absorb small amounts of VOCs from atmosphere because they release the compounds while decaying. To estimate how efficient this absorption is, Karl and his team measured the level of VOCs in the atmosphere at six different places across South and North America representing different ecosystems. Three of them represented rain forests and others were temperate deciduous forest, mixed temperate forests and semiarid shrub lands.

With the help of computer modeling and laboratory experiments, the scientists analysed the field data and found, on an average 36 % more VOCs than thought.

The process occurs at an optimum rate in thick tropical forests and is the lowest in semiarid shrub. The finding provides a platform for better climate models, Karl said.

Anjali Srivastava, a researcher at the National Environmental Engineering Research Institute, calls the work significant and pioneering. Srivastava works on identifying plants that can help reduce the level of VOCs in indoor environment, for example deodorants and paints.

"Initial findings show basil and money plant can significantly reduce VOCs indoors, " she said.