From 2011 to 2015, California experienced its worst drought on record, with a parching combination of high temperatures and low precipitation. Drought conditions can have complicated effects on ozone air quality, so to better understand the process, researchers have analyzed data from two ozone-polluted cities before, during and after the California drought. They report their results in ACS’ journal Environmental Science & Technology.
Although ozone in the stratosphere protects the earth from ultraviolet radiation, at ground level the molecule is a harmful air pollutant to humans, animals and plants. Ground-level ozone forms when nitrogen oxide compounds, primarily from motor vehicle emissions, react with volatile organic compounds (VOCs) from natural and anthropomorphic sources. Isoprene, a VOC emitted by plants, is a significant contributor to ozone production during summer months in many locations around the world. However, plants also decrease air ozone levels by taking the gas up through pores in their leaves. Because drought conditions affect both of these plant-related processes, Angelique Demetillo, Sally Pusede and colleagues wanted to examine air concentrations of isoprene and ozone — as well as leaf area index, nitrogen dioxide and meteorology — before, during and after the California drought.