A survey of California plant species with a portable VOC analyzer for biogenic emission inventory development

An accurate estimate of the magnitude of biogenic volatile organic compound (BVOC) emissions in California's airsheds is critical for formulating effective strategies to reduce concentrations of fine particles, ozone, and other secondary air pollutants which affect human health and reduce yields of agricultural crops. However, California's natural and urban landscapes contain more than 6000 species, and the BVOC emissions from only a small fraction of these species have been characterized by quantitative measurements. A taxonomic method has been proposed to assign BVOC emission rate measurements to unmeasured species, but data are needed for additional plant families and genera to further develop and test this taxonomic approach. In the present study, BVOC emissions from more than 250 plant species were measured through a semi-quantitative method employing calibrated portable analyzers with photoionization detectors (PID). Replicate samples of live foliage were placed in plastic bags, in both light and darkened conditions, and the BVOC emissions categorized as low, medium or high. To validate our approach, for 63 plant species we compared our PID-measured BVOC emissions with published values, based on gas chromatography (GC) or GC–mass spectrometry, and found them to be well correlated. The method employed was more suited for detecting compounds with relatively higher emission rates, such as isoprene, than compounds with low emission rates, which could include monoterpenes and oxygenated compounds. For approximately 200 plant species not previously measured, the results provide further evidence that plant taxonomy can serve as a useful guide for generalizing the emissions behavior of many, but not all, plant families and genera.