Abstract
Abstract. Using OMI (Ozone Monitoring Instrument) tropospheric NO2 columns and a nested-grid 3-D global chemical transport model (GEOS-Chem), we investigated the growth in NOx emissions from coal-fired power plants and their contributions to the growth in NO2 columns in 2005–2007 in China. We first developed a unit-based power plant NOx emission inventory for 2005–2007 to support this investigation. The total capacities of coal-fired power generation have increased by 48.8% in 2005–2007, with 92.2% of the total capacity additions coming from generator units with size ≥300 MW. The annual NOx emissions from coal-fired power plants were estimated to be 8.11 Tg NO2 for 2005 and 9.58 Tg NO2 for 2007, respectively. The modeled summer average tropospheric NO2 columns were highly correlated (R2 = 0.79–0.82) with OMI measurements over grids dominated by power plant emissions, with only 7–14% low bias, lending support to the high accuracy of the unit-based power plant NOx emission inventory. The ratios of OMI-derived annual and summer average tropospheric NO2 columns between 2007 and 2005 indicated that most of the grids with significant NO2 increases were related to power plant construction activities. OMI had the capability to trace the changes of NOx emissions from individual large power plants in cases where there is less interference from other NOx sources. Scenario runs from GEOS-Chem model suggested that the new power plants contributed 18.5% and 10% to the annual average NO2 columns in 2007 in Inner Mongolia and North China, respectively. The massive new power plant NOx emissions significantly changed the local NO2 profiles, especially in less polluted areas. A sensitivity study found that changes of NO2 shape factors due to including new power plant emissions increased the summer average OMI tropospheric NO2 columns by 3.8–17.2% for six selected locations, indicating that the updated emission information could help to improve the satellite retrievals.
Highlights
Nitrogen oxides (NOx ≡NO + NO2) play an important role in the photochemical production of tropospheric ozone and are detrimental to human health and the ecosystem
To further investigate the impact of the uncertainties associated with other anthropogenic emissions on the evaluation of the power plant inventory, we compare the modeled and observed NO2 columns over three categories of grids in China as the following three cases: grids dominated by power plant NOx emissions (Case A), all grids with power plants (Case B), and all grids in China (Case C)
We have demonstrated the rapid growth of power plant NOx emissions in 2005–2007 and their contributions to the increasing NO2 columns in China, based on a unit-based power plant NOx emission inventory for mainland China, nested-grid Goddard Earth Observing System (GEOS)-Chem model, and Ozone Monitoring Instrument (OMI) observations
Summary
Nitrogen oxides (NOx ≡NO + NO2) play an important role in the photochemical production of tropospheric ozone and are detrimental to human health and the ecosystem. NOx is released to the troposphere as a result of anthropogenic Wang et al.: Growth in NOx emissions from power plants in China biomass burning) and natural (e.g., soil emissions, wildfires and lightning) phenomena. During the past two decades, anthropogenic NOx emissions from China have surged simultaneously with the rapid growth in China’s economy and attract the attention of scientists and policy makers. Coalfired power plants are the largest coal consumer in China and are believed to be the largest contributor to China’s NOx emissions (Hao et al, 2002; Zhang et al, 2007). The total capacity of coalfired power plants has increased by 49 %, from 328 GW in 2005 to 489 GW in 2007
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