Biogenic volatile organic compound emissions from desert vegetation of the southwestern US

Abstract

Thirteen common plant species in the Mojave and Sonoran Desert regions of the western US were tested for emissions of biogenic non-methane volatile organic compounds (BVOCs). Only two of the species examined emitted isoprene at rates of 10 mg C g À1 h À1 or greater. These species accounted for o10% of the estimated vegetative biomass in these arid regions of low biomass density, indicating that these ecosystems are not likely a strong source of isoprene. However, isoprene emissions from these species continued to increase at much higher leaf temperatures than is observed from species in other ecosystems. Five species, including members of the Ambrosia genus, emitted monoterpenes at rates exceeding 2 mg C g À1 h À1 . Emissions of oxygenated compounds, such as methanol, ethanol, acetone/propanal, and hexanol, from cut branches of several species exceeded 10 mg C g À1 h À1 , warranting further investigation in these ecosystems. Model extrapolation of isoprene emission measurements verifies recently published observations that desert vegetation is a small source of isoprene relative to forests. Annual and daily total model isoprene emission estimates from an eastern US mixed forest landscape were 10-30 times greater than isoprene emissions estimated from the Mojave site. Monoterpene (and possibly oxygenated terpene and sesquiterpene) emissions may be more comparable, as annual forest terpene emission model estimates were 3-8 times greater than those from the Mojave Desert, and were within a factor of 2 for peak summertime fluxes. Primary productivity and leaf biomass of desert ecosystems are very dependent on annual precipitation, and our model results indicate that there can be at least a three-fold difference in total annual BVOC emissions between dry and wet years. We recommend additional studies of desert plant BVOC emissions, especially those that focus on sesquiterpenes, oxygenated compounds, and the effects of soil moisture, temperature, humidity, and seasonality. Landscape flux studies are needed to test BVOC model estimates and to verify BVOC influences on regional atmospheric chemistry. Published by Elsevier Ltd.

Estimations of isoprenoid emission capacity from enclosure studies: measurements, data processing, quality and standardized measurement protocols

“…Although the adsorption and desorption characteristics of polymers used most frequently in emission studies have not been studied quantitatively for key volatiles emitted from plants, studies on organic vapors of environmental concern have suggested that polymers such as neoprene and low-density polyethylene, used by default in commercial systems, have potentially significant adsorption/desorption problems for VOC studies (Allaire et al, 2003;Avison et al, 2001;Hartman, 1999;Hodgson et al, 1998;Manura, 1999). Apart from adsorption on polymers, in commercial gas-exchange systems, traces of silicone oil are present in O-ring seals, and in CO 2 cartridges, and in the match valve of Li-Cor 6400 system, introducing additional memory effects and contamination problems due to solubilization and evaporation of anthropogenic and biogenic VOCs in oil (Geron et al, 2006a).…”

“…Brilli et al, 2009;Calfapietra et al, 2008;Ekberg et al, 2009;Geron et al, 2001Geron et al, , 2006aLavoir et al, 2009;Okumura et al, 2008;Peñuelas et al, 2009). The smaller well-mixed chambers generally reach steady-state more quickly, within seconds to minutes, than larger chambers.…”

First space-based derivation of the global atmospheric methanol emission fluxes

“…The model underestimation points to the existence of a larger-than-modelled biogenic methanol source in such ecosystems. Geron et al (2006) investigated biogenic VOC emissions from common desert plants in the southwestern US. The study was focused on terpenoid emissions but some cut branches were analysed with a PTR-MS system so that emissions of methanol and other compounds could be investigated.…”

The impacts of reactive terpene emissions from plants on air quality in Las Vegas, Nevada

“…Two species in this study, creosote bush and saltbush, were also measured by Geron et al (2006) at a location approximately 100 km northwest of Las Vegas. Our current study and Geron et al both found no significant isoprene emissions from these two species.…”

“…b Acacia stenophylla (shoestring acacia) BVOC emissions were used to represent all species of acacia in metropolitan area. c Emission factors from Geron et al (2006) were used to represent Ambrosia dumosa (white bursage).…”