Rapid growth in nitrogen dioxide pollution over Western China, 2005–2013

Abstract

Abstract. Western China has experienced rapid industrialization and urbanization since the implementation of the National Western Development Strategies (the "Go West" movement) in 1999. This transition has affected the spatial and temporal characteristics of nitrogen dioxide (NO2) pollution. In this study, we analyze the trends and variability of tropospheric NO2 vertical column densities (VCDs) from 2005 to 2013 over Western China, based on a wavelet analysis on monthly mean NO2 data derived from the Ozone Monitoring Instrument (OMI) measurements. We focus on the anthropogenic NO2 by subtracting region-specific "background" values dominated by natural sources. After removing the background influences, we find significant anthropogenic NO2 growth over Western China between 2005 and 2013 (8.6 ± 0.9 % yr−1 on average, relative to 2005), with the largest increments (15 % yr−1 or more) over parts of several city clusters. The NO2 pollution in most provincial-level regions rose rapidly from 2005 to 2011 but stabilized or declined afterwards. The NO2 trends were driven mainly by changes in anthropogenic emissions, as confirmed by a nested GEOS-Chem model simulation and a comparison with Chinese official emission statistics. The rate of NO2 growth during 2005–2013 reaches 11.3 ± 1.0 % yr−1 over Northwestern China, exceeding the rates over Southwestern China (5.9 ± 0.6 % yr−1) and the three well-known polluted regions in the east (5.3 ± 0.8 % yr−1 over Beijing-Tianjin-Hebei, 4.0 ± 0.6 % yr−1 over the Yangtze River Delta, and −3.3 ± 0.3 % yr−1 over the Pearl River Delta). Subsequent socioeconomic analyses suggest that the rapid NO2 growth over Northwestern China is likely related to the fast developing resource- and pollution-intensive industries along with the "Go West" movement as well as relatively weak emission controls. Further efforts should be made to alleviate NOx pollution to achieve sustainable development in Western China.

Monthly top‐down NOx emissions for China (2005–2012): A hybrid inversion method and trend analysis

“…We also find an increase of emissions from 2011 to 2012 in Xinjiang and Yunnan, supporting the implication in Cui et al [] of an underestimate in the official emission inventory. The year‐to‐year variations (e.g., decrease of emissions in 2008 over China and Beijing) are more clear in our posterior than in Cui et al [], since we present variations on annual time scales. When compared to top‐down emissions from Mijling et al [] using GOME‐2 observations and the Daily Emission estimates Constrained by Satellite Observations (DECSO) algorithm (cyan line in the first panel of Figure ), our posterior NO x emissions are 10% to 19% larger from 2007 to 2009, almost the same in 2010, and 8% smaller in 2011.…”

“…We find a generally increasing trend of NO x emissions in western China, which is consistent with Cui et al [] in terms of contributions of anthropogenic emissions to observed NO 2 column trends, even though we are using different retrieval products which have different trends as shown in Figure and described in section 4.2. The anthropogenic contributions they reported are less influenced by meteorology and are more directly comparable to our posterior emissions.…”

“…The anthropogenic contributions they reported are less influenced by meteorology and are more directly comparable to our posterior emissions. We also find an increase of emissions from 2011 to 2012 in Xinjiang and Yunnan, supporting the implication in Cui et al [] of an underestimate in the official emission inventory. The year‐to‐year variations (e.g., decrease of emissions in 2008 over China and Beijing) are more clear in our posterior than in Cui et al [], since we present variations on annual time scales.…”

OMI-measured increasing SO<sub>2</sub> emissions due to energy industry expansion and relocation in northwestern China

“…in China (55 630 MW) during the 11th 5-year plan period (2006)(2007)(2008)(2009)(2010) (Cui et al, 2016). As shown in Table 1, the SO 2 emission reduction plans virtually specified the zero percentage of SO 2 emission reductions in Qinghai, Gansu, and Xinjiang and lower reduction percentage in the emission reduction in Ningxia and Inner Mongolia as compared to eastern and southern China during the 11th (2006)(2007)(2008)(2009)(2010) and 12th (2011-2015) 5-year plans.…”

Satellite NO2 retrievals suggest China has exceeded its NOx reduction goals from the twelfth Five-Year Plan

“…Over China, in addition to the studies cited above, NO 2 retrievals from the Global Ozone Monitoring Experiment-2 (GOME-2) were reconciled with OMI retrievals and were used to estimate seasonal and weekday variations23. Recent work found rapid growth over western China continuing through 20131724 whereas reductions have been observed since 2011 in the main Chinese cities as well as in the North China Plain2526. Changes in NO 2 are leading to shifts in the ozone chemical regime and to changes in formaldehyde levels depending on the regional conditions in China27.…”