Blue Sky Olympics: Satellite Observations of Air Quality During the 2008 Beijing Olympics

China has imposed short-term emission control regulations on industry and transportation to quickly improve air quality during certain events, including the 2008 Summer Olympic Games. Previous research noted reductions in NO2 vertical column density, CO emissions, CO2 emissions, and Aerosol Optical Depth (AOD). NO2 and SO2 decreased in neighboring provinces, during this time period. Using MODIS level-2 atmospheric aerosol product (MYD04_L2) data, processed by the dark target algorithm, this study observes trends in regional AOD and temporal change in AOD during the Olympic emissions reduction program. 2008 observations are referenced against AOD observations from 2003 to 2013, within 9-day intervals from June 23rd to October 24th and 40 km bands extending up to 240 km from the Beijing municipal limits. During the Olympics, median AOD values were below median AOD values from the reference period. AOD levels returned to above reference period levels in the September 12th to September 20th period, before the end of the Special Olympics in Beijing. During the Olympic period, reductions in AOD values, compared to the reference period were observed in regions within 80 km of Beijing, while an increase in AOD values was present in regions 120 km to 240 km from Beijing

Hazard posed by metals and As in PM2.5 in air of five megacities in the Beijing-Tianjin-Hebei region of China during APEC

Airborne fine particulate matter (PM2.5) from five megacities including Beijing, Tianjin, Shijiazhuang, Baoding, and Jinan were collected during November 2014 and compared with similar periods in 2012 and 2013. The November 2014 period coincided with the Asia Pacific Economic Cooperation (APEC) Leaders Meeting during which measures to control pollution of the air were introduced. Concentrations of 11 elements in PM2.5 were quantified by inductively coupled plasma–mass spectrometry (ICP-MS) after microwave-assisted digestion. Potential effects of five toxic trace metals including Mn, Ni, Cu, Zn, Pb, and the metalloid As on health were assessed. In 2014, concentrations of PM2.5 were significantly less than during the same period in 2012 and 2013. Mean concentrations of six elements ranked in decreasing order, Zn > Pb > Cu ≈ Mn > As > Ni, and spatial concentrations ranked in decreasing order, Shijiazhuang > Baoding > Tianjin > Jinan > Beijing. Risks of the five metals and the metalloid As to health of humans were small, except for Mn in Shijiazhuang. Risks to health posed by other elements were less during the period of study. Risks posed by the five metals and As in Beijing were greater to varying degrees after the APEC meeting. Risks to health of humans during the APEC were overall lesser than the same period in 2012 and 2013, mostly due to lesser emissions due to the short-term control measures

Characterization and source identification of fine particulate matter in urban Beijing during the 2015 Spring Festival

The Spring Festival (SF) is the most important holiday in China for family reunion and tourism. During the 2015 SF an intensive observation campaign of air quality was conducted to study the impact of the anthropogenic activities and the dynamic characteristics of the sources. During the study period, pollution episodes frequently occurred with 12 days exceeding the Chinese Ambient Air Quality Standards for 24-h average PM2.5 (75 μg/m3), even 8 days with exceeding 150 μg/m3. The daily maximum PM2.5 concentration reached 350 μg/m3 while the hourly minimum visibility was <0.8 km. Three pollution episodes were selected for detailed analysis including chemical characterization and diurnal variation of the PM2.5 and its chemical composition, and sources were identified using the Positive Matrix Factorization model. The first episode occurring before the SF was characterized by more formation of SO42− and NO3− and high crustal enrichment factors for Ag, As, Cd, Cu, Hg, Pb, Se and Zn and seven categories of pollution sources were identified, whereby vehicle emission contributed 38% to the PM2.5. The second episode occurring during the SF was affected heavily by large-scale firework emissions, which led to a significant increase in SO42−, Cl−, OC, K and Ba; these emissions were the largest contributor to the PM2.5 accounting for 36%. During the third episode occurring after the SF, SO42−, NO3−, NH4+ and OC were the major constituents of the PM2.5 and the secondary source was the dominant source with a contribution of 46%. The results provide a detailed understanding on the variation in occurrence, chemical composition and sources of the PM2.5 as well as of the gaseous pollutants affected by the change in anthropogenic activities in Beijing throughout the SF. They highlight the need for limiting the firework emissions during China's most important traditional festival

Mitigation and control of urban air pollution in Beijing

Outdoor air pollution kills more than 4 million people around the world per year and heavy pollution episodes continue to occur especially around large urban centres. In addition to long-term mitigation strategies, short-term emission controls are needed to prevent heavy pollution episodes in megacities such as Beijing. Such controls have been implemented with reasonable success in the past, notably during mega-events, but need to be carefully evaluated to develop a robust mitigation strategy for future. In this work, the 10-day long controls implemented before the APEC summit in Beijing during November 2014 were evaluated for their eectiveness using an online atmospheric chemical transport model WRF-Chem. The controls were found to be only partly responsible for the improvement in air quality during the summit period, while the rest of the improvement was due to favourable meteorology which reduced pollutant levels signicantly as compared to the levels before the control period. The controls were found to be insucient in meeting national air quality standards if applied during periods with more stagnant conditions. Sensitivity studies were performed to identify temporally-resolved source contributions from various sectors and regions. It was found that controls on local emissions benet air quality on the same day, controls on regional emissions show peak benets a day or two after the start of controls and controls on distant emissions show peak benets three to four days later. Local and regional residential and industry sectors were found to dominate contributions to PM2.5 levels in Beijing. A Gaussian statistical technique was used to replace the model behaviour over Beijing with a fast emulator to generate concentration response surfaces for emission reductions across various sectors and regions. These results were utilized to develop an optimal policy for short-term emission controls in Beijing and were implemented in an automatic air quality forecasting and emission prescription system which runs the model successively with reduced emissions to meet daily air quality targets and outputs the magnitude and timing of controls needed across various sectors and regions to prevent heavy pollution episodes in Beijing. This is a novel application of the popular method called Model Predictive Control often used in the petrochemical industry, to air quality modelling. The framework developed here is for Beijing but can be readily adopted for any other polluted region of the world

Significant wintertime PM_(2.5) mitigation in the Yangtze River Delta, China, from 2016 to 2019: observational constraints on anthropogenic emission controls

Ambient fine particulate matter (PM_(2.5)) mitigation relies strongly on anthropogenic emission control measures, the actual effectiveness of which is challenging to pinpoint owing to the complex synergies between anthropogenic emissions and meteorology. Here, observational constraints on model simulations allow us to derive not only reliable PM_(2.5) evolution but also accurate meteorological fields. On this basis, we isolate meteorological factors to achieve reliable estimates of surface PM_(2.5) responses to both long-term and emergency emission control measures from 2016 to 2019 over the Yangtze River Delta (YRD), China. The results show that long-term emission control strategies play a crucial role in curbing PM_(2.5) levels, especially in the megacities and other areas with abundant anthropogenic emissions. The G20 summit hosted in Hangzhou in 2016 provides a unique and ideal opportunity involving the most stringent, even unsustainable, emergency emission control measures. These emergency measures lead to the largest decrease (∼ 35 µg m⁻³, ∼ 59 %) in PM_(2.5) concentrations in Hangzhou. The hotspots also emerge in megacities, especially in Shanghai (32 µg m⁻³, 51 %), Nanjing (27 µg m⁻³, 55 %), and Hefei (24 µg m⁻³, 44 %) because of the emergency measures. Compared to the long-term policies from 2016 to 2019, the emergency emission control measures implemented during the G20 Summit achieve more significant decreases in PM_(2.5) concentrations (17 µg m⁻³ and 41 %) over most of the whole domain, especially in Hangzhou (24 µg m⁻³, 48 %) and Shanghai (21 µg m⁻³, 45 %). By extrapolation, we derive insight into the magnitude and spatial distribution of PM_(2.5) mitigation potential across the YRD, revealing significantly additional room for curbing PM_(2.5) levels