Atmospheric visibility can directly reflect the air quality.In this study,we measured watersoluble ions(WSIs),organic and element carbon(OC and EC)in PM 2.5 from September 2017 to August 2018 in Urumqi,NW China.The re...Atmospheric visibility can directly reflect the air quality.In this study,we measured watersoluble ions(WSIs),organic and element carbon(OC and EC)in PM 2.5 from September 2017 to August 2018 in Urumqi,NW China.The results show that SO4^2-,NO 3^(-)and NH4^(+)were the major WSIs,together accounting for 7.32%-84.12%of PM 2.5 mass.Total carbon(TC=OC+EC)accounted for 12.12%of PM 2.5 mass on average.And OC/EC>2 indicated the formation of secondary organic carbon(SOC).The levels of SO4^2-,NO3^(-)and NH4^(+)in low visibility days were much higher than those in high visibility days.Relative humidity(RH)played a key role in affecting visibility.The extinction coefficient(b ext)that estimated via Koschmieder formula with visibility was the highest in winter(1441.05±739.95 Mm-1),and the lowest in summer(128.58±58.00 Mm^(-)1).The b ext that estimated via IMPROVE formula with PM 2.5 chemical component was mainly contributed by(NH 4)2 SO4 and NH4 NO3.The b ext values calculated by both approaches presented a good correlation with each other(R^2=0.87).Multiple linear regression(MLR)method was further employed to reconstruct the empirical regression model of visibility as a function of PM 2.5 chemical components,NO_(2) and RH.The results of source apportionment by Positive Matrix Factorization(PMF)model showed that residential coal combustion and vehicle emissions were the major sources of b ext.展开更多
Defect-rich hierarchical sponge-like TiO2 nanoparticles were successfully synthesized via the combined one-step hydrothermal method and chemical reduction approach.SEM and TEM images showed their porous structure dens...Defect-rich hierarchical sponge-like TiO2 nanoparticles were successfully synthesized via the combined one-step hydrothermal method and chemical reduction approach.SEM and TEM images showed their porous structure densely packed with even smaller TiO2 particles,while photocatalytic results manifested their superior photocatalytic performance and high stability.The RhB solution(10 ppm)could be absolutely degraded in 60 min,and the degradation rate was twice that of the sample without the treatment by NaBH4.Besides,the TC solution(10 ppm)could be removed by 74.3%in 20 min.PEC measurements also displayed that the photoelectrode based on such defectrich TiO2 nanoparticles had small resistance and improved charge transfer rate.The improved performance can be assigned to rich defects and phase junctions,which was supported by characterization results.The presence of rich defects and phase junctions could not only promote the separation of photogenerated charge carriers,but also accelerate the electron transfer,beneficial for both the photocatalytic and the PEC performance.It is expected that the obtained hierarchical sponge-like TiO2 nanoparticles with rich defects have great potential for photocatalytic applications.展开更多
基金the National Natural Science Foundation of China(No.41967050/41722305)the State Key Laboratory of Organic Geochemistry,GIGCAS(No.SKLOG201915)+1 种基金the Guangdong Foundation for Program of Science and Technology Research(No.2019B121205006)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01Z134)。
文摘Atmospheric visibility can directly reflect the air quality.In this study,we measured watersoluble ions(WSIs),organic and element carbon(OC and EC)in PM 2.5 from September 2017 to August 2018 in Urumqi,NW China.The results show that SO4^2-,NO 3^(-)and NH4^(+)were the major WSIs,together accounting for 7.32%-84.12%of PM 2.5 mass.Total carbon(TC=OC+EC)accounted for 12.12%of PM 2.5 mass on average.And OC/EC>2 indicated the formation of secondary organic carbon(SOC).The levels of SO4^2-,NO3^(-)and NH4^(+)in low visibility days were much higher than those in high visibility days.Relative humidity(RH)played a key role in affecting visibility.The extinction coefficient(b ext)that estimated via Koschmieder formula with visibility was the highest in winter(1441.05±739.95 Mm-1),and the lowest in summer(128.58±58.00 Mm^(-)1).The b ext that estimated via IMPROVE formula with PM 2.5 chemical component was mainly contributed by(NH 4)2 SO4 and NH4 NO3.The b ext values calculated by both approaches presented a good correlation with each other(R^2=0.87).Multiple linear regression(MLR)method was further employed to reconstruct the empirical regression model of visibility as a function of PM 2.5 chemical components,NO_(2) and RH.The results of source apportionment by Positive Matrix Factorization(PMF)model showed that residential coal combustion and vehicle emissions were the major sources of b ext.
基金This work was financially supported by the National Natural Science Foundation of China (Grant No. 21405105)the Shanghai Natural Science Foundation (14ZR1429300)the State Key Laboratory of Green Catalysis of Sichuan Institutes of Higher Education (LZJ1703).
文摘Defect-rich hierarchical sponge-like TiO2 nanoparticles were successfully synthesized via the combined one-step hydrothermal method and chemical reduction approach.SEM and TEM images showed their porous structure densely packed with even smaller TiO2 particles,while photocatalytic results manifested their superior photocatalytic performance and high stability.The RhB solution(10 ppm)could be absolutely degraded in 60 min,and the degradation rate was twice that of the sample without the treatment by NaBH4.Besides,the TC solution(10 ppm)could be removed by 74.3%in 20 min.PEC measurements also displayed that the photoelectrode based on such defectrich TiO2 nanoparticles had small resistance and improved charge transfer rate.The improved performance can be assigned to rich defects and phase junctions,which was supported by characterization results.The presence of rich defects and phase junctions could not only promote the separation of photogenerated charge carriers,but also accelerate the electron transfer,beneficial for both the photocatalytic and the PEC performance.It is expected that the obtained hierarchical sponge-like TiO2 nanoparticles with rich defects have great potential for photocatalytic applications.
