In this study, ozone (O3) sensitivity and linearity over East Asia (EA) and seven urban areas are examined with an integrated air quality modeling system under two categories of scenarios: (1) The effects of domestic emission are estimated under local emission reduction scenarios, as anthropogenic NO(x) and volatile organic compounds (VOC) emissions are reduced by 20%, 50%, and 100%, respectively and independently; and (2) the influence of intercontinental transport is evaluated under Task Force on Hemispheric Transport of Air Pollution (TF HTAP) emission reduction scenarios, as anthropogenic NO(x) emission is reduced by 20% in Europe (EU), North America (NA), and South Asia (SA), respectively. Simulations are conducted for January and July 2001 to examine seasonal variation. Through the domestic O3 sensitivity investigation, we find O3 sensitivity varies dynamically depending on both time and location: North EA is VOC limited in January and NO(x) limited in July, except for the urban areas Beijing, Shanghai, Tokyo, and Seoul, which are VOC limited in both months; south EA is NO(x) limited in both January and July, except for the urban areas Taipei, which is VOC-limited in both months, and Pearl River Delta, which is VOC limited in January. Surface O3 change is found to be affected more by NO(x) than by VOC over EA in both January and July. We also find different O3 linearity characteristics among urban areas in EA: O3 at Beijing, Tokyo, and Seoul shows a strong negative linear response to NO(x) emission in January; O3 at Shanghai, Pearl River Delta, and Taipei shows a strong positive response to VOC emission in both January and July. Through the long-range transport investigation, monthly O3 changes over EA resulting from different source regions indicate the largest source contribution comes from NA (0.23 ppb), followed by SA (0.11 ppb) and EU (0.10 ppb). All of the three regions show higher impacts in January than in July.
This study examine O3 sensitivities and linear response of NO(x) and VOC emission over EA and seven urban areas based on regional air quality modeling system MM5/CMAQ. We also quantify the intercontinental transport effect from EU, SA, and NA over EA. The result provide a theoretical basis for emission control strategy design in EA, and also reveal the O3 special nonlinearity features for further related studies that are applicable to other continents. The HTAP multimodel experiments need to examine the potential impacts on ground-level O3 of changes in meteorology and transport patterns expected as a result of the regional scale.
"As the major precursor for both NO 3 − and O 3 , a few studies already demonstrated that NOx emission change over YRD would lead to increase of O 3 especially in winter due to the local VOC-sensitive condition (Fu et al., 2012a; Dong et al., 2013). However, impact of NOx emission change on NO 3 − may retain many uncertainties due to the complicacy within the chemical processes discussed in last section. "
[Show abstract][Hide abstract] ABSTRACT: The new Chinese National Ambient Air Quality standards (CH-NAAQS) published on Feb. 29th, 2012 listed PM2.5 as criteria pollutant for the very first time. In order to probe into PM2.5 pollution over Yangtze River Delta, the integrated MM5/CMAQ modeling system is applied for a full year simulation to examine the PM2.5 concentration and seasonality, and also the inorganic aerosols responses to precursor emission changes. Total PM2.5 concentration over YRD was found to have strong seasonal variation with higher values in winter months (up to 89.9μg/m(3) in January) and lower values in summer months (down to 28.8μg/m(3) in July). Inorganic aerosols were found to have substantial contribution to PM2.5 over YRD, ranging from 37.1% in November to 52.8% in May. Nocturnal production of nitrate (NO3(-)) through heterogeneous hydrolysis of N2O5 was found significantly contribute to high NO3(-) concentration throughout the year. In winter, NO3(-) was found to increase under nitrogen oxides (NOx) emission reduction due to higher production of N2O5 from the excessive ozone (O3) introduced by attenuated titration, which further lead to increase of ammonium (NH4(+)) and sulfate (SO4(2-)), while other seasons showed decrease response of NO3(-). Sensitivity responses of NO3(-) under anthropogenic VOC emission reduction was examined and demonstrated that in urban areas over YRD, NO3(-) formation was actually more sensitive to VOC than NOx due to the O3-involved nighttime chemistry of N2O5, while a reduction of NOx emission may have counter-intuitive effect by increasing concentrations of inorganic aerosols.
Science of The Total Environment 03/2014; 481C(1):522-532. DOI:10.1016/j.scitotenv.2014.02.076 · 4.10 Impact Factor
"MM5 model performance was evaluated against surface dataset from the National Climatic Data Center (NCDC) following the evaluation protocol used in Fu et al. (2012). The four major meteorological variables evaluated included 2-m wind speed and wind direction, 2-m temperature, and 2-m relative humidity, which were the most important factors affecting air pollution. "
[Show abstract][Hide abstract] ABSTRACT: On February 29th 2012, China published its new National Ambient Air
Quality Standard (CH-NAAQS) aiming at revising the standards and
measurements for both gaseous pollutants including ozone
(O3), nitrogen dioxide (NO2), and sulfur dioxide
(SO2), and also particle pollutants including PM10
and PM2.5. In order to understand the air pollution status
regarding this new standard, the integrated MM5/CMAQ modeling system was
applied over Yangtze River Delta (YRD) within this study to examine the
criteria gaseous pollutants listed in the new CH-NAAQS. Sensitivity
simulations were also conducted to assess the responses of gaseous
pollutants under 8 different sector-dependent emission reduction
scenarios in order to evaluate the potential control strategies. 2006
was selected as the simulation year in order to review the air quality
condition at the beginning of China's 11th Five-Year-Plan (FYP, from
2006 to 2010), and also compared with air quality status in 2010 as the
end of 11th FYP to probe into the effectiveness of the national emission
control efforts. Base case simulation showed distinct seasonal variation
for gaseous pollutants: SO2, and NO2 were found to
have higher surface concentrations in winter while O3 was
found to have higher concentrations in spring and summer than other
seasons. According to the analyses focused on 3 megacities within YRD,
Shanghai, Nanjing, and Hangzhou, we found different air quality
conditions among the cities: NO2 was the primary pollutant
that having the largest number of days exceeding the CH-NAAQS daily
standard (80 μg m-3) in Shanghai (59 days)
and Nanjing (27 days); SO2 was the primary pollutant with
maximum number of days exceeding daily air quality standard
(150 μg m-3) in Hangzhou (28 days), while
O3 exceeding the daily maximum 8-h standard
(160 μg m-3) for relatively fewer days in
all the three cities (9 days in Shanghai, 14 days in Nanjing, and 11
days in Hangzhou). Simulation results from predefined potential
applicable emission control scenarios suggested significant air quality
improvements from emission reduction: 90% of SO2 emission
removed from power plant in YRD would be able to reduce more than 85% of
SO2 pollution, 85% NOx emission reduction from
power plant would reduce more than 60% of NO2 pollution, in
terms of reducing the number of days exceeding daily air quality
standard. NOx emission reduction from transportation and
industry were also found to effectively reduce NO2 pollution
but less efficient than emission control from power plants. We also
found that multi-pollutants emission control including both
NOx and VOC would be a better strategy than independent
NOx control over YRD which is China's 12th Five-Year-Plan
(from 2011 to 2015), because O3 pollution would be increased
as a side effect of NOx control and counteract NO2
pollution reduction benefit.
[Show abstract][Hide abstract] ABSTRACT: Dynamical downscaling was applied in this study to link the global climate-chemistry model Community Atmosphere Model (CAM-Chem) with the regional models Weather Research and Forecasting (WRF) Model and Community Multi-scale Air Quality (CMAQ). Two representative concentration pathway (RCP) scenarios (RCP 4.5 and RCP 8.5) were used to evaluate the climate impact on ozone concentrations in the 2050s.
From the CAM-Chem global simulation results, ozone concentrations in the lower to mid-troposphere (surface to ∼300 hPa), from mid-to high latitudes in the Northern Hemisphere, decreases by the end of the 2050s (2057-2059) in RCP 4.5 compared to present (2001-2004), with the largest decrease of 4-10 ppbv occurring in the summer and the fall; and an increase as high as 10 ppbv in RCP 8.5 resulting from the increased methane emissions.
From the regional model CMAQ simulation results, under the RCP 4.5 scenario (2057-2059), in the summer when photochemical reactions are the most active, the large ozone precursor emissions reduction leads to the greatest decrease of downscaled surface ozone concentrations compared to present (2001-2004), ranging from 6 to 10 ppbv. However, a few major cities show ozone increases of 3 to 7 ppbv due to weakened NO titration. Under the RCP 8.5 scenario, in winter, downscaled ozone concentrations increase across nearly the entire continental US in winter, ranging from 3 to 10 ppbv due to increased methane emissions. More intense heat waves are projected to occur by the end of the 2050s in RCP 8.5, leading to a 0.3 ppbv to 2.0 ppbv increase (statistically significant except in the Southeast) of the mean maximum daily 8 h daily average (MDA8) ozone in nine climate regions in the US. Moreover, the upper 95% limit of MDA8 increase reaches 0.4 ppbv to 1.5 ppbv in RCP 4.5 and 0.6 ppbv to 3.2 ppbv in RCP 8.5. The magnitude differences of increase between RCP 4.5 and 8.5 also reflect that the increase of methane emissions may favor or strengthen the effect of heat waves.
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