Measurement of Volatile Organic Compounds

To answer critical questions regarding the interactions between green plants and air quality, two three-year projects are underway to investigate emission of volatile organic compounds (VOC) from selected plant species. These biogenic VOC (BVOC) and oxides of nitrogen (NOx) can react in the lower atmosphere in the presence of sunlight to form ozone and secondary particulate matter, the principal air pollutants in California airsheds. This work will provide a better understanding of the role that citrus and other crops play in ozone destruction via surface deposition, stomatal uptake, and reactions in the crop canopy. Results will improve biogenic emission inventories and increase understanding of regional VOC levels, and therefore aid the California Air Research Board in improving air quality attainment strategies. For example, results may affect regulatory emphasis on other VOC sources (e.g. cars, trucks, pesticides) and NOx controls (e.g. emission controls on engines). Other possible implications regard chemical signaling between insects and plants. This work includes laboratory investigations at UC Berkeley and field studies in Tulare County. The Slosson endowment provided seed money for these projects. 1.0 EXECUTIVE SUMMARY The Issue: Green plants in gardens and landscapes play important direct roles in improving air quality through sequestration of carbon dioxide, emission of oxygen, and providing surfaces for deposition of airborne particles and gases. Plants also play significant indirect roles in reducing air pollution through providing shade and lowering air temperatures, thus reducing the need for energy consumption for cooling. Plants also play important roles in air quality through emission of volatile organic compounds (VOC), which may react with oxides of nitrogen (NOx) to produce ozone, which in the lower atmosphere is a pollutant affecting human health and reducing crop yields. Conversely, ozone may be destroyed by plants through stomatal uptake, surface deposition, and within-canopy chemical loss processes. What has ANR done? To answer critical questions regarding the interactions between green plants and air quality, two three-year projects are underway to investigate emission of VOC from selected plant species. We identified and quantified VOC produced (emitted and stored) by leaves of 22 woody and herbaceous plants found in California. We also measured ozone deposition rates to selected plant species. The Payoff • BVOC emission shows a typical daily pattern with maximum emissions around noon. • Navel orange is the highest BVOC emitter of citrus measured in this study (0.45 μgC g(DW) h). However, that emission rate is much lower than emission rates measured for many plant species found in natural plant communities and urban