Ozone uptake and BVOC emission from the major citrus crops in California measured via an enclosure system

Tropospheric ozone affects human health, plant health, regional air quality and Earth's climate. To understand regional ozone concentrations, sources of ozone precursors, atmospheric chemistry, meteorological transport and mechanical loss process including vegetation uptake have to be considered. In this study, we focus on ozone uptake and biogenic volatile organic carbon (BVOC) emissions that play a role in regional photochemical production of ozone and aerosols, by five varieties of citrus trees which are widely cultivated, including in California's Central Valley, where regional ground-level ozone concentrations frequently violate National Ambient Air Quality Standard during the summer. To measure ozone uptake and BVOC emissions, we performed branch enclosure tests in a greenhouse of the University of California at Berkeley. Fluxes of CO2 and H2O (LiCor-6262), O3 (Dasibi 1008), , and VOCs (GC-FID, GC-MS and PTR-MS) were determined by measuring concentrations in air entering and leaving the chamber. Temperature, humidity, PAR (Photosynthetically Active Radiation), leaf mass, and leaf area, were also recorded. . Greenhouse light and temperature conditions were maintained at levels similar to those found in summer in the Central Valley. The study objective is to improve BVOC emission inventories for California and O3 uptake rates for each of these citrus species, to improve understanding of plant-atmosphere interaction processes, and for modeling regional air quality.