Abstract
In this study, a regional dynamical model (WRF) is used to drive biogenic emission models to calculate high resolution (10x10 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 changes in central eastern China, which could have a very important impact on ozone formation in this region. However, these estimates are highly uncertain and are presented as a potential scenario to show the importance of possible changes of biogenic emissions in China.
Highlights
China is undergoing major economic changes, leading to heightened energy usage and a significant increase in pollutant emissions
The biogenic emissions of nitric oxide (NO) are high during summer, and low during winter, with a smaller seasonal variation compared to the emissions of isoprene and monoterpenes
The biogenic emissions of NO are largely co-located with the anthropogenic emissions of NO in China, while the biogenic emissions of isoprenoids are not overlapped with the anthropogenic emissions of VOCs
Summary
China is undergoing major economic changes, leading to heightened energy usage and a significant increase in pollutant emissions. To fully understand the chemistry in China and to model the distributions of air pollutants, the biogenic emissions of VOCs and NO need to be estimated. VOCs play a variety of important roles in the chemistry of the atmosphere, including enhancement in the production of peroxy (HO2 and RO2) radicals and organic aerosols. To better understand air pollutants in China, a biogenic emission inventory with high spatial resolution is needed. Because isoprenoids (isoprene and monterpenes) are major contributors to total biogenic VOC emissions (Guenther et al, 2000), and have important impacts on atmospheric oxidants and aerosols (Lack et al, 2003; Wiedinmyer et al, 2006), isoprenoid emissions are considered as biogenic VOC emissions in this study. The paper is organized as follows: In Section 2, we will briefly describe the tools, including the dynamical WRF-Weather Forecast Model (WRF) and the biogenic models; in Section 3, the biogenic emissions are analyzed for China
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