Abstract
Abstract. The uncertainties of a national, bottom-up inventory of Chinese emissions of anthropogenic SO2, NOx, and particulate matter (PM) of different size classes and carbonaceous species are comprehensively quantified, for the first time, using Monte Carlo simulation. The inventory is structured by seven dominant sectors: coal-fired electric power, cement, iron and steel, other industry (boiler combustion), other industry (non-combustion processes), transportation, and residential. For each parameter related to emission factors or activity-level calculations, the uncertainties, represented as probability distributions, are either statistically fitted using results of domestic field tests or, when these are lacking, estimated based on foreign or other domestic data. The uncertainties (i.e., 95% confidence intervals around the central estimates) of Chinese emissions of SO2, NOx, total PM, PM10, PM2.5, black carbon (BC), and organic carbon (OC) in 2005 are estimated to be −14%~13%, −13%~37%, −11%~38%, −14%~45%, −17%~54%, −25%~136%, and −40%~121%, respectively. Variations at activity levels (e.g., energy consumption or industrial production) are not the main source of emission uncertainties. Due to narrow classification of source types, large sample sizes, and relatively high data quality, the coal-fired power sector is estimated to have the smallest emission uncertainties for all species except BC and OC. Due to poorer source classifications and a wider range of estimated emission factors, considerable uncertainties of NOx and PM emissions from cement production and boiler combustion in other industries are found. The probability distributions of emission factors for biomass burning, the largest source of BC and OC, are fitted based on very limited domestic field measurements, and special caution should thus be taken interpreting these emission uncertainties. Although Monte Carlo simulation yields narrowed estimates of uncertainties compared to previous bottom-up emission studies, the results are not always consistent with those derived from satellite observations. The results thus represent an incremental research advance; while the analysis provides current estimates of uncertainty to researchers investigating Chinese and global atmospheric transport and chemistry, it also identifies specific needs in data collection and analysis to improve on them. Strengthened quantification of emissions of the included species and other, closely associated ones – notably CO2, generated largely by the same processes and thus subject to many of the same parameter uncertainties – is essential not only for science but for the design of policies to redress critical atmospheric environmental hazards at local, regional, and global scales.
Highlights
A series of studies have been conducted using bottom-up methods to explore Chinese emissions of anthropogenic atmospheric pollutants (Streets et al, 2001, 2003; Hao et al, 2002; Cao et al, 2006; Ohara et al, 2007; Zhang et al, 2009d; Klimont et al, 2009; Lei et al, 2011a)
The NOx emission factor for grate stokers is estimated to be 4.2 kg per metric ton of coal burned, and the probability is fitted to a lognormal distribution with geometric standard deviation (GSD) of 1.8 kg t−1 based on 93 data points ranging 1.1–24.5 kg t−1 in tests by SEPA (1996)
Besides electrostatic precipitators (ESP), a few tests have been conducted in China on other dust collectors including fabric filter systems (FF), WET scrubbers (WET), and cyclones (CYC) (Yi et al, 2008; Wang et al, 2009; Li et al, 2009a; Zhao et al, 2010), but the sampling data are insufficient for probability fitting
Summary
A series of studies have been conducted using bottom-up methods to explore Chinese emissions of anthropogenic atmospheric pollutants (Streets et al, 2001, 2003; Hao et al, 2002; Cao et al, 2006; Ohara et al, 2007; Zhang et al, 2009d; Klimont et al, 2009; Lei et al, 2011a). To better understand the uncertainties of atmospheric pollutant emissions, Frey and Zheng (2002) developed a bootstrap simulation method and analyzed the uncertainties of NOxemission factors and emissions of coal-fired power plants of different technology types This method was applied to other species and sectors (Frey and Li, 2003; Frey and Zhao, 2004). Based on bootstrap and Monte Carlo simulations, an emission factor database for Chinese coal-fired power plants has been established with detailed categories of combustion technologies and fuel qualities (Zhao et al, 2010) Such methods have proven difficult to apply to even one region of China due to lack of supporting data (Zheng et al, 2009), and they have never been previously used to evaluate the uncertainties of an integrated emission inventory for the entire country.
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