Anthropogenic Nitrogen oxides(NO_(x)=NO_(2)+NO)emissions are highly concentrated in urban area,and the weekly cycles,seasonal patterns and long-term trends of tropospheric NO_(2) columns over cities differ from region...Anthropogenic Nitrogen oxides(NO_(x)=NO_(2)+NO)emissions are highly concentrated in urban area,and the weekly cycles,seasonal patterns and long-term trends of tropospheric NO_(2) columns over cities differ from region to region due to different emission sectoral compositions and human activities.In this study,we used satellite observed tropospheric NO_(2) column data to compare the longand short-term NO_(2) column density time series over cities in the United Sates(the U.S.),western Europe and China.The results showed that in all the targeted cities,the outbreak of the Corona Virus Disease in 2019(COVID-19)moved the December peak of the city-level NO_(2)columns forward to November and October or even earlier in 2020 and 2021.On weekly level,cities in the U.S.show the lowest NO_(2) columns ratio on weekend/work day,then come the western European cities,and a weak weekly pattern is seen in Chinese cities.For all the cites,we find a higher weekend/work day NO_(2) ratio in cold seasons than in warm seasons,indicating a higher contribution from NOx emission sectors of residential,industry and power plants in the warm seasons.In the long-term,NO_(2) columns over the U.S.and western European cities declined by a fraction twice that of the regional mean level from 2004 to 2021.In China,NO_(2) columns started to decrease since 2012,at a similar rate between the city and regional level.This work confirms the importance to quantify and control NOx emissions from cities.展开更多
Comprehensive Air Quality Model with extensions(CAMx)-Decoupled Direct Method(DDM)simulations of first-order ozone(O_(3))sensitivity to nitrogen oxides(NO_(x))and volatile organic compounds(VOCs)emissions were perform...Comprehensive Air Quality Model with extensions(CAMx)-Decoupled Direct Method(DDM)simulations of first-order ozone(O_(3))sensitivity to nitrogen oxides(NO_(x))and volatile organic compounds(VOCs)emissions were performed and combined with modelled P_(H_(2)O_(2))/P_(HNO_(3))ratios to obtain a range of thresholds for determining O_(3)-sensitivity regimes for different areas of China.Utilising the new threshold ranges for photochemical indicators,the method for determining O_(3)formation in the Ozone Source Apportionment Technology(OSAT)module within CAMx was improved by a dynamically varied threshold of P_(H_(2)O_(2))/P_(HNO_(3))ratio.The O_(3)concentration contributions in the newly added transition regime were apportioned to NO_(x)and VOCs emissions in proportion to the relationship between the P_(H_(2)O_(2))/P_(HNO_(3))ratio and first-order O_(3)sensitivity.The source contributions of O_(3)concentrations from different emission sectors from June to September 2019 were compared using the original and improved CAMx-OSAT.The results showed that the O_(3)concentration contributions changed significantly in the NO_(x)-limited regime,with a maximum decrease of 21.89%,while the contributions increased by up to 7.57%in the VOC-limited regime,and were within 15μg/m^(3)in the transition regime.The modified OSAT module enabled a more sophisticated attribution of O_(3)to precursor emissions and may have far-reaching implications for informing O_(3)pollution control policy.展开更多
基金Under the auspices of the National Natural Science Foundation of China(No.42375106,41805098)the National Key R&D Program of China(No.2023YFB3907500)。
文摘Anthropogenic Nitrogen oxides(NO_(x)=NO_(2)+NO)emissions are highly concentrated in urban area,and the weekly cycles,seasonal patterns and long-term trends of tropospheric NO_(2) columns over cities differ from region to region due to different emission sectoral compositions and human activities.In this study,we used satellite observed tropospheric NO_(2) column data to compare the longand short-term NO_(2) column density time series over cities in the United Sates(the U.S.),western Europe and China.The results showed that in all the targeted cities,the outbreak of the Corona Virus Disease in 2019(COVID-19)moved the December peak of the city-level NO_(2)columns forward to November and October or even earlier in 2020 and 2021.On weekly level,cities in the U.S.show the lowest NO_(2) columns ratio on weekend/work day,then come the western European cities,and a weak weekly pattern is seen in Chinese cities.For all the cites,we find a higher weekend/work day NO_(2) ratio in cold seasons than in warm seasons,indicating a higher contribution from NOx emission sectors of residential,industry and power plants in the warm seasons.In the long-term,NO_(2) columns over the U.S.and western European cities declined by a fraction twice that of the regional mean level from 2004 to 2021.In China,NO_(2) columns started to decrease since 2012,at a similar rate between the city and regional level.This work confirms the importance to quantify and control NOx emissions from cities.
基金supported by the the National Key Research and Development Project(Nos.2022YFC3701105,2018YFC0213504,2017YFC0213003)the National Natural Science Foundation of China(No.42005112)。
文摘Comprehensive Air Quality Model with extensions(CAMx)-Decoupled Direct Method(DDM)simulations of first-order ozone(O_(3))sensitivity to nitrogen oxides(NO_(x))and volatile organic compounds(VOCs)emissions were performed and combined with modelled P_(H_(2)O_(2))/P_(HNO_(3))ratios to obtain a range of thresholds for determining O_(3)-sensitivity regimes for different areas of China.Utilising the new threshold ranges for photochemical indicators,the method for determining O_(3)formation in the Ozone Source Apportionment Technology(OSAT)module within CAMx was improved by a dynamically varied threshold of P_(H_(2)O_(2))/P_(HNO_(3))ratio.The O_(3)concentration contributions in the newly added transition regime were apportioned to NO_(x)and VOCs emissions in proportion to the relationship between the P_(H_(2)O_(2))/P_(HNO_(3))ratio and first-order O_(3)sensitivity.The source contributions of O_(3)concentrations from different emission sectors from June to September 2019 were compared using the original and improved CAMx-OSAT.The results showed that the O_(3)concentration contributions changed significantly in the NO_(x)-limited regime,with a maximum decrease of 21.89%,while the contributions increased by up to 7.57%in the VOC-limited regime,and were within 15μg/m^(3)in the transition regime.The modified OSAT module enabled a more sophisticated attribution of O_(3)to precursor emissions and may have far-reaching implications for informing O_(3)pollution control policy.
基金国家自然科学基金项目 ( 4 9975 0 2 640 3 180 0 1) +1 种基金Research Grant Council of HongKong (PolyU 5 0 61/99E)The Hong Kong Polytechnic Uni versity (G YW 5 8)共同资助
