Biogenic emissions of isoprenoids and NO in China and comparison to anthropogenic emissions

Abstract

In this study, a regional dynamical model (WRF) is used to drive biogenic emission models to calculate high resolution (10 × 10 km) biogenic emissions of isoprene (C 5 H 8 ), monoterpenes (C 10 H 16 ), and nitric oxide (NO) in China. This high resolution biogenic inventory will be available for the community to study the effect of biogenic emissions on photochemical oxidants in China. The biogenic emissions are compared to anthropogenic emissions to gain insight on the potential impact of the biogenic emissions on tropospheric chemistry, especially ozone production in this region. The results show that the biogenic emissions in China exhibit strongly diurnal, seasonal, and spatial variations. The isoprenoid (including both isoprene and monoterpenes) emissions are closely correlated to tree density and strongly vary with season and local time. During winter (January), the biogenic isoprenoid emissions are the lowest, resulting from lower temperature and solar radiation, and highest in summer (July) due to higher temperature and solar radiation. The biogenic NO emissions are also higher during summer and lower during winter, but the magnitude of the seasonal variation is smaller than the emissions of isoprene and monoterpenes. The biogenic emissions of NO are widely spread out in the northern, eastern, and southern China regions, where high-density agricultural soil lands are located. Both biogenic NO and isoprenoid emissions are very small in western China. The calculated total biogenic emission budget is smaller than the total anthropogenic VOC emission budget in China. The biogenic isoprenoid and anthropogenic VOC emissions are 10.9 and 15.1 Tg year − 1 , respectively. The total biogenic and anthropogenic emissions of NO are 5.9 and 11.5 Tg(NO) year − 1 , respectively. The study shows that in central eastern China, the estimated biogenic emissions of isoprenoids are very small, and the anthropogenic emissions of VOCs are dominant in this region. However, in northeastern and southern China, there are relatively large biogenic emissions of isoprenoids, leading to an important impact on the ozone production in these regions. Furthermore, the emissions of isoprenoids are highest during summer and noontime, which correlates to the peak of ozone production period. For example, the ratio between summer and winter for the emissions of isoprenoids is about 15 in China. As a result, the biogenic emissions of isoprenoids are significantly larger than the anthropogenic emissions of VOCs in China during daytime in summer. Biogenic NO emissions are mostly produced by agricultural soils which co-exist with large populations and human activity. As a result, the biogenic emissions of NO are mostly overlapped with the anthropogenic emissions of NO, leading to the enhancement in NO concentrations in the high anthropogenic NO emission regions. Finally, the future emissions of isoprene and monoterpenes over China are estimated. The results show that the future biogenic emissions may increase significantly due to land cover ...

Global data set of biogenic VOC emissions calculated by the MEGAN model over the last 30 years

“…However, the link between isoprene emissions and increasing drought condition is more difficult to identify. Tingey et al (1981) and Pegoraro et al (2004b) found that for short-term soil moisture deficit lasting for a couple of days, the isoprene emission rate remains constant or even slightly increases in the initial stages of drought (Pegoraro et al, 2007). But as the soil moisture decreases below a certain level isoprene emission starts to decline as well.…”

“…A reduction of isoprene emission rate by 64 % after 12 days of severe drought was observed for live-oak plants (Quercus virginiana Mill.) by Pegoraro et al (2004b) as well as a decrease by 50 % after 5 days (Tingey et al, 1981). The experimental findings of Pegoraro et al (2004a) served as a base for the parameterization of the impact of soil moisture stress on isoprene emissions in the MEGAN model.…”

“…Several studies have investigated the impact of drought on various processes ongoing within plants (Tingey et al, 1981;Sharkey and Loreto, 1993;Pegoraro et al, 2004aPegoraro et al, , b, 2007Brilli et al, 2007) and have found a clear decline of photosynthetic rate, stomatal conductance and transpiration rate directly after the soil water content decrease. However, the link between isoprene emissions and increasing drought condition is more difficult to identify.…”

“…MEGAN-MACC isoprene emissions were compared to values estimated in regional studies in different parts of the world (Table 3). Emission estimates of Fu et al (2007) and Palmer et al (2003) were derived from GOME (Global Ozone Monitoring Experiment) formaldehyde observations. Barkley et al (2013) derived isoprene emissions using formaldehyde vertical column measurements from OMI (Ozone Monitoring Instrument) and SCIAMACHY (Scanning imaging absorption spectrometer for atmospheric chartography).…”

“…Chalita et al, 1996;Brasseur et al, 1998;Gauss et al, 2006). In addition to the significance in the gas-phase chemistry, oxidative products of some biogenic VOCs may undergo a phase transition and form secondary organic aerosol (SOA) (Hoffmann et al, 1997;Griffin et al, 1999;Limbeck et al, 2003;van Donkelaar et al, 2007) having important consequences in the Earth's radiation budget.…”