Improved land cover and emission factors for modeling biogenic volatile organic compounds emissions from Hong Kong

Abstract

a b s t r a c tThis paper describes a study of local biogenic volatile organic compounds (BVOC) emissions from the Hong Kong Special Administrative Region (HKSAR). An improved land cover and emission factor database was developed to estimate Hong Kong emissions using MEGAN, a BVOC emission model developed by Guenther et al. (2006). Field surveys of plant species composition and laboratory measurements of emission factors were combined with other data to improve existing land cover and emission factor data. The BVOC emissions from Hong Kong were calculated for 12 consecutive years from 1995 to 2006. For the year 2006, the total annual BVOC emissions were determined to be 12,400 metric tons or 9.82 Â 10 9 g C (BVOC carbon). Isoprene emission accounts for 72%, monoterpene emissions account for 8%, and other VOCs emissions account for the remaining 20%. As expected, seasonal variation results in a higher emission in the summer and a lower emission in the winter, with emission predominantly in day time. A high emission of isoprene occurs for regions, such as Lowest Forest-NT North, dominated by broadleaf trees. The spatial variation of total BVOC is similar to the isoprene spatial variation due to its high contribution. The year to year variability in emissions due to weather was small over the twelve-year period (À1. 4%, 2006 to 1995 trendline), but an increasing trend in the annual variation due to an increase in forest land cover can be observed (þ7%, 2006 to 1995 trendline). The results of this study demonstrate the importance of accurate land cover inputs for biogenic emission models and indicate that land cover change should be considered for these models.

Sensitivity of biogenic volatile organic compound emissions to leaf area index and land cover in Beijing

“…That terpenoid emission estimate is similar to the 10.9 Tg estimated by Tie et al (2006). Since subtropical regions in China have severe ozone pollution and abundant forests, multiple studies have focused on local biogenic emissions and their potential effects on urban air quality Leung et al, 2010). As a typical city in northern China, Beijing faces severe ozone pollution in summer (Wang et al, 2006;Safieddine et al, 2016;Zhao et al, 2010).…”

“…The differences among the inputs do not have a significant effect on the temporal variability in the BVOC emissions estimated by the MEGAN model. Moreover, the ratio of BVOC emissions between the summer and winter seasons is 185-295, compared with a ratio of 9.77 in the Pearl River Delta region and 4.9 in Hong Kong (Leung et al, 2010). In temperate regions like Beijing, BVOC emissions display a very strong annual cycle, as there are almost no BVOC emissions in winter owing to the low winter biomass of temperate deciduous trees as well as low temperatures in winter.…”

“…The leaf-scale emission factor, leaf mass per area (LMA, g m −2 ) and the standard environmental factor were used to convert the leaf-scale emission factors to canopy-scale emission factors (Leung et al, 2010;Guenther et al, 2006). In MEGAN, the ε can be described by either the specific tree species map or the plant functional type (PFT) map .…”

Impacts of decadal variations in natural emissions due to land-cover changes on ozone production in southern China

“…For example, in the present study the average isoprene emission flux in PRD was 0.35 Mg C km (2 in July, slightly higher than the summertime average of 0.31 Mg C km (2 reported by Wang et al (2011). Our total isoprene emission estimate in Hong Kong (0.35 Tg C) was also close to the given value of 0.39 Tg C by Tsui et al (2009), but both estimates were lower than the value reported by Leung et al (2010) (1.0 Tg C) by 60Á70%, due to the large differences in input data used (Table 3). Plotted against weather conditions, modelled biogenic emissions display a bell-shaped diurnal cycle, peaking at approximately 13:00 LST and nearly ceasing overnight (particularly for isoprene), with decreasing temperature and solar radiation (Supplementary Fig.…”

“…In this study, PFT-specific emission factors of BVOCs for the four aggregated PFTs (i.e., broadleaf forest, coniferous forest, shrub, and cropland/grassland) were determined by local field observations in the literature Sakulyanontvittaya et al, 2008;Tsui et al, 2009;Leung et al, 2010;Wang et al, 2011). NO emission factors from soil were developed through measurements with static or dynamic chambers (Williams et al, 1992;Guenther et al, 2000).…”