Characteristics of atmospheric VOCs(volatile organic compounds) have been extensively studied in megacities in China, however, they are scarcely investigated in medium/smallsized cities in North China Plain(NCP).A com...Characteristics of atmospheric VOCs(volatile organic compounds) have been extensively studied in megacities in China, however, they are scarcely investigated in medium/smallsized cities in North China Plain(NCP).A comprehensive research on possible sources of VOCs was conducted in a medium-sized city of NCP, from May to September 2019.A total of 143 canister samples of 8 sites in Xuchang city were collected, and 57 VOC species were detected.The average VOC concentrations were 42.6 ± 31.6 μg/m3, with 53.7 ± 31.0 μg/m3 and 32.1 ± 27.8 μg/m^(3), in the morning and afternoon, respectively.Alkenes and aromatics contributed 80% of the total ozone formation potential(OFP).Aromatics accounted for more than 95% of secondary organic aerosol potential(SOAP).VOCs were dominated by the local emission with significant transport from the southeast direction.PMF analysis extracted 6 sources, which were combustion(33.1%), LPG usage(19.3%), vehicular exhaust & fuel evaporation(15.8%), solvent usage(15.2%), industrial(9.11%) and biogenic(7.51%), respectively and they contributed 33.4%, 17.6%, 12.9%, 18.6%, 9.28% and 8.22% to the OFP, respectively.Combustion and LPG usage were the dominant VOC sources;and combustion, solvent usage and LPG usage were the main sources of OFP in Xuchang city, which were different to megacities in China with a high contribution from vehicular exhaust, solvent usage and industry,suggesting specific control strategies on VOCs need to be implemented in medium-sized city such as Xuchang city.展开更多
Using daily precipitation data from 110 stations in Southeast China from 1960 to 2012,the extreme precipitation(EP)events associated with monsoon and tropical cyclones were examined using the Objective Synoptic Analys...Using daily precipitation data from 110 stations in Southeast China from 1960 to 2012,the extreme precipitation(EP)events associated with monsoon and tropical cyclones were examined using the Objective Synoptic Analysis Technique.In Southeast China,the extreme precipitation associated with tropical cyclones(TEP),which mainly occur in the summer(July–September),accounted for 27.9%of the total extreme precipitation amount,with 40–50%in the coastal regions.While the regional mean TEP amount showed an inconspicuous trend,total EP and monsoon EP(MEP)both showed an increasing trend,with the MEP trend being statistically significant.Although there was little change in the frequency of tropical cyclones affecting Southeast China,the TEP contribution to frequency increased with increasing EP threshold and the frequency of TEP with daily precipitation of more than 300 mm showed an increasing trend in the background of global climate change.The upward trend in the highest-threshold TEP events presents a challenge for mitigation of the damage associated with tropical cyclones.展开更多
基金supported by the National Natural Science Foundation of China (Nos.41675127, 41475116)。
文摘Characteristics of atmospheric VOCs(volatile organic compounds) have been extensively studied in megacities in China, however, they are scarcely investigated in medium/smallsized cities in North China Plain(NCP).A comprehensive research on possible sources of VOCs was conducted in a medium-sized city of NCP, from May to September 2019.A total of 143 canister samples of 8 sites in Xuchang city were collected, and 57 VOC species were detected.The average VOC concentrations were 42.6 ± 31.6 μg/m3, with 53.7 ± 31.0 μg/m3 and 32.1 ± 27.8 μg/m^(3), in the morning and afternoon, respectively.Alkenes and aromatics contributed 80% of the total ozone formation potential(OFP).Aromatics accounted for more than 95% of secondary organic aerosol potential(SOAP).VOCs were dominated by the local emission with significant transport from the southeast direction.PMF analysis extracted 6 sources, which were combustion(33.1%), LPG usage(19.3%), vehicular exhaust & fuel evaporation(15.8%), solvent usage(15.2%), industrial(9.11%) and biogenic(7.51%), respectively and they contributed 33.4%, 17.6%, 12.9%, 18.6%, 9.28% and 8.22% to the OFP, respectively.Combustion and LPG usage were the dominant VOC sources;and combustion, solvent usage and LPG usage were the main sources of OFP in Xuchang city, which were different to megacities in China with a high contribution from vehicular exhaust, solvent usage and industry,suggesting specific control strategies on VOCs need to be implemented in medium-sized city such as Xuchang city.
基金supported by the National Natural Science Foundation of China (Grant No.41375056 and 91224004)the Meteorological Specialty Foundation of China (Grant No.GYHY201206013)
文摘Using daily precipitation data from 110 stations in Southeast China from 1960 to 2012,the extreme precipitation(EP)events associated with monsoon and tropical cyclones were examined using the Objective Synoptic Analysis Technique.In Southeast China,the extreme precipitation associated with tropical cyclones(TEP),which mainly occur in the summer(July–September),accounted for 27.9%of the total extreme precipitation amount,with 40–50%in the coastal regions.While the regional mean TEP amount showed an inconspicuous trend,total EP and monsoon EP(MEP)both showed an increasing trend,with the MEP trend being statistically significant.Although there was little change in the frequency of tropical cyclones affecting Southeast China,the TEP contribution to frequency increased with increasing EP threshold and the frequency of TEP with daily precipitation of more than 300 mm showed an increasing trend in the background of global climate change.The upward trend in the highest-threshold TEP events presents a challenge for mitigation of the damage associated with tropical cyclones.
