Source apportionment of anthropogenic and biogenic organic aerosol over the Tokyo metropolitan area from forward and receptor models.

Organic aerosol (OA) is a dominant component of PM2.5, and accurate knowledge of its sources is critical for identification of cost-effective measures to reduce PM2.5. For accurate source apportionment of OA, we conducted field measurements of organic tracers at three sites (one urban, one suburban, and one forest) in the Tokyo Metropolitan Area and numerical simulations of forward and receptor models. We estimated the source contributions of OA by calculating three receptor models (positive matrix factorization, chemical mass balance, and secondary organic aerosol (SOA)-tracer method) using the ambient concentrations, source profiles, and production yields of OA tracers. Sensitivity simulations of the forward model (chemical transport model) for precursor emissions and SOA formation pathways were conducted. Cross-validation between the receptor and forward models demonstrated that biogenic and anthropogenic SOA were better reproduced by the forward model with updated modules for emissions of biogenic volatile organic compounds (VOC) and for SOA formation from biogenic VOC and intermediate-volatility organic compounds than by the default setup. The source contributions estimated by the forward model generally agreed with those of the receptor models for the major OA sources: mobile sources, biomass combustion, biogenic SOA, and anthropogenic SOA. The contributions of anthropogenic SOA, which are the main focus of this study, were estimated by the forward and receptor models to have been between 9 % and 15 % in summer 2019. The observed percent modern carbon data indicate that the amounts of anthropogenic SOA produced during daytime have substantially declined from 2007 to 2019. This trend is consistent with the decreasing trend of anthropogenic VOC, suggesting that reduction of anthropogenic VOC has been effective in reducing anthropogenic SOA in the atmosphere.

Effectiveness of emission controls implemented since 2000 on ambient ozone concentrations in multiple timescales in Japan: An emission inventory development and simulation study.

It has been reported that ambient ozone concentrations in Japan have not been effectively suppressed by precursor emission controls. In this study, we developed an unprecedented long-term emission inventory of ozone precursors, including nitrogen oxide (NOX) and volatile organic compounds (VOCs), in Japan. The developed emission inventory, which explicitly represents changes in emissions caused by emission controls and variation in activities from 2000 to 2019, revealed that emission controls implemented for vehicles, large point sources, and fugitive VOC sources effectively reduced precursor emissions. The impact of emission changes on ozone concentrations at six different timescales was evaluated using air quality simulations. Three of them corresponded to annual mean values of daily ozone concentrations, and the others corresponded to annual high ozone concentrations. The simulations performed better at higher ozone concentrations. The simulation results suggested that emission controls have helped suppress annual high ozone concentrations, whereas the annual mean values of daily ozone concentrations may have increased in populated urban areas because reduced NOX emissions weakened the titration of ozone. Overall changes in the simulated ozone concentrations over different timescales were generally consistent with those in the observed ozone concentrations. These findings highlight the importance of evaluating the impact of emission controls on ozone concentrations over multiple timescales. The differences in the sensitivities of ozone concentrations to emission controls were clearly explained by the ozone sensitivity regimes implied by the ratios of formaldehyde to nitrogen dioxide. The outcomes of this study could assist countries beyond Japan in developing effective strategies to manage ozone pollution.

Consumption in the G20 nations causes particulate air pollution resulting in two million premature deaths annually.

Worldwide exposure to ambient PM2.5 causes over 4 million premature deaths annually. As most of these deaths are in developing countries, without internationally coordinated efforts this polarized situation will continue. As yet, however, no studies have quantified nation-to-nation consumer responsibility for global mortality due to both primary and secondary PM2.5 particles. Here we quantify the global footprint of PM2.5-driven premature deaths for the 19 G20 nations in a position to lead such efforts. G20 consumption in 2010 was responsible for 1.983 [95% Confidence Interval: 1.685-2.285] million premature deaths, at an average age of 67, including 78.6 [71.5-84.8] thousand infant deaths, implying that the G20 lifetime consumption of about 28 [24-33] people claims one life. Our results indicate that G20 nations should take responsibility for their footprint rather than focusing solely on transboundary air pollution, as this would expand opportunities for reducing PM2.5-driven premature mortality. Given the infant mortality footprint identified, it would moreover contribute to ensuring infant lives are not unfairly left behind in countries like South Africa, which have a weak relationship with G20 nations.

Affluent countries inflict inequitable mortality and economic loss on Asia via PM2.5 emissions.

This research sets out to quantify the mortality and economic loss in individual Asian countries caused by the PM2.5 emissions induced by the consumption of the world's five highest-consuming countries (US, China, Japan, Germany, UK). In 2010 alone, the economic impact of these five countries' consumption caused a loss of almost 45 billion US dollars due to the premature deaths of more than 1 million people in Asia, including 15 thousand children younger than 5 years old. The percentage ratio of economic loss to value-added driven by consumers via trade differed greatly among the impacted countries. For the US, the highest percentage loss was 4.1% in Laos, followed by 2.0% in Bangladesh, both markedly higher than the figures for the more developed countries, such as 0.21% for Japan and 0.18% for Korea. This reflects the inequitable value chain existing between consumer countries and impacted countries, and implies that developing countries are obtaining value-added in exchange for unintentionally increased health risks, delaying their development and potentially creating a vicious circle that hinders much-needed improvements in areas like poverty reduction and public health. This inequitable situation needs to be redressed through introduction of clean energy and other types of technological assistance to help achieve United Nations Sustainable Development Goals 7, 10 and 13. Such as move is essential if premature infant deaths are to be curtailed.

Contributions of Condensable Particulate Matter to Atmospheric Organic Aerosol over Japan.

Because emission rates of particulate matter (PM) from stationary combustion sources have been measured without dilution or cooling in Japan, condensable PM has not been included in Japanese emission inventories. In this study, we modified an emission inventory to include condensable PM from stationary combustion sources based on the recent emission surveys using a dilution method. As a result, emission rates of organic aerosol (OA) increased by a factor of 7 over Japan. Stationary combustion sources in the industrial and energy sectors became the largest contributors to OA emissions over Japan in the revised estimates (filterable-plus-condensable PM), while road transport and biomass burning were the dominant OA sources in the previous estimate (filterable PM). These results indicate that condensable PM from large combustion sources makes critical contributions to total PM2.5 emissions. Simulated contributions of condensable PM from combustion sources to atmospheric OA drastically increased around urban and industrial areas, including the Kanto region, where OA concentrations increased by factors of 2.5-6.1. Consideration of condensable PM from stationary combustion sources improved model estimates of OA in winter but caused overestimation of OA concentrations in summer. Contributions of primary and secondary OA should be further evaluated by comparing with organic tracer measurements.

Sensitivity analyses of factors influencing CMAQ performance for fine particulate nitrate.

UNLABELLED: Improvement of air quality models is required so that they can be utilized to design effective control strategies for fine particulate matter (PM2.5). The Community Multiscale Air Quality modeling system was applied to the Greater Tokyo Area of Japan in winter 2010 and summer 2011. The model results were compared with observed concentrations of PM2.5 sulfate (SO4(2-)), nitrate (NO3(-)) and ammonium, and gaseous nitric acid (HNO3) and ammonia (NH3). The model approximately reproduced PM2.5 SO4(2-) concentration, but clearly overestimated PM2.5 NO3(-) concentration, which was attributed to overestimation of production of ammonium nitrate (NH4NO3). This study conducted sensitivity analyses of factors associated with the model performance for PM2.5 NO3(-) concentration, including temperature and relative humidity, emission of nitrogen oxides, seasonal variation of NH3 emission, HNO3 and NH3 dry deposition velocities, and heterogeneous reaction probability of dinitrogen pentoxide. Change in NH3 emission directly affected NH3 concentration, and substantially affected NH4NO3 concentration. Higher dry deposition velocities of HNO3 and NH3 led to substantial reductions of concentrations of the gaseous species and NH4NO3. Because uncertainties in NH3 emission and dry deposition processes are probably large, these processes may be key factors for improvement of the model performance for PM2.5 NO3(-). IMPLICATIONS: The Community Multiscale Air Quality modeling system clearly overestimated the concentration of fine particulate nitrate in the Greater Tokyo Area of Japan, which was attributed to overestimation of production of ammonium nitrate. Sensitivity analyses were conducted for factors associated with the model performance for nitrate. Ammonia emission and dry deposition of nitric acid and ammonia may be key factors for improvement of the model performance.

Determination and potential importance of diterpene (kaur-16-ene) emitted from dominant coniferous trees in Japan.

Reactive volatile organic compounds (VOCs) are known to affect atmospheric chemistry. Biogenic VOCs (BVOCs) have a significant impact on regional air quality due to their large emission rates and high reactivities. Diterpenes (most particularly, kaur-16-ene) were detected in all of the 205 enclosure air samples collected over multiple seasons at two different sites from Cryptomeria japonica and Chamaecyparis obtusa trees, the dominant coniferous trees in Japan,. The emission rate of kaur-16-ene, was determined to be from 0.01 to 7.1 µg dwg(-1) h(-1) (average: 0.61 µg dwg(-1) h(-1)) employing branch enclosure measurements using adsorbent sampling followed by solid phase-liquid extraction techniques. The emission rate was comparable to that of monoterpenes, which is known major BVOC emissions, collected from the same branches. In addition, total emission of kaur-16-ene at 30°C was estimated to exceed that of total anthropogenic VOC emissions.

A modeling study of coarse particulate matter pollution in Beijing: regional source contributions and control implications for the 2008 Summer Olympics.

In the last 10 yr, Beijing has made a great effort to improve its air quality. However, it is still suffering from regional coarse particulate matter (PM10) pollution that could be a challenge to the promise of clean air during the 2008 Olympics. To provide scientific guidance on regional air pollution control, the Mesoscale Modeling System Generation 5 (MM5) and the Models-3/Community Multiscale Air Quality Model (CMAQ) air quality modeling system was used to investigate the contributions of emission sources outside the Beijing area to pollution levels in Beijing. The contributions to the PM10 concentrations in Beijing were assessed for the following sources: power plants, industry, domestic sources, transportation, agriculture, and biomass open burning. In January, it is estimated that on average 22% of the PM10 concentrations can be attributed to outside sources, of which domestic and industrial sources contributed 37 and 31%, respectively. In August, as much as 40% of the PM10 concentrations came from regional sources, of which approximately 41% came from industry and 31% from power plants. However, the synchronous analysis of the hourly concentrations, regional contributions, and wind vectors indicates that in the heaviest pollution periods the local emission sources play a more important role. The implications are that long-term control strategies should be based on regional-scale collaborations, and that emission abatement of local sources may be more effective in lowering the PM10 concentration levels on the heavy pollution days. Better air quality can be attained during the Olympics by placing effective emission controls on the local sources in Beijing and by controlling emissions from industry and power plants in the surrounding regions.