This study presents the observations of PM10 and PM2.5 concentrations at an agricultural site from April to October 2012 in Dehui city,China.Ambient air was sampled by filter-based samplers and online PM monitors.The ...This study presents the observations of PM10 and PM2.5 concentrations at an agricultural site from April to October 2012 in Dehui city,China.Ambient air was sampled by filter-based samplers and online PM monitors.The filter samples were analyzed to determine the abundance of ionic/inorganic elements,organic carbon（OC） and elemental carbon（EC）.The daily PM10 concentrations varied significantly over the monitoring period,with an average of168 ± 63（in the range of 52-277） μg/m^3 during the land preparation/planting period（26 April-15 June）,85 ± 65（36-228） μg/m^3 during the growing season（16 June-25 September）,and 207 ±88（103-310） μg/m^3 during the harvest period（26 September-31 October）.PM2.5 accounted for44%,56%and 66%of atmospheric PM10 during these periods,respectively.The PM10 diurnal variation showed a distinct peak from 16：00 to 21：00（LST） during the growing and harvesting seasons,while a gradual increase throughout the daytime until 17：00 was observed during tilling season.Mineral dust elements（Al,Ca,Fe,and Mg） dominated the PM10 chemical composition during the tilling season;OC,NO3^-,SO4^（2-） and NH4~＋ during the growing season;and carbonaceous species（i.e.,OC and EC） during the harvesting season.Our results indicate that the soil particles emitted by farm tillage and organic matter released from straw burning are the two most significant sources of PM10 emissions contributing to the recurring high pollution events in this region.Therefore,development of agricultural PM inventories from soil tillage and straw burning is prioritized to support air quality modeling.展开更多
This study presents the mass concentrations of PM（2.5）,O3,SO2 and NOxat one urban,one suburban and two rural locations in the Changchun region from September 25 to October 272013. Major chemical components of PM（2....This study presents the mass concentrations of PM（2.5）,O3,SO2 and NOxat one urban,one suburban and two rural locations in the Changchun region from September 25 to October 272013. Major chemical components of PM（2.5）at the four sites were daily sampled and analyzed. Most of daily concentrations of SO2（7–82 μg/m^3）,O3（27–171 μg/m^3） and NOx（14–213 μg/m^3） were below the limits of the National Ambient Air Quality Standard（NAAQS）in China. However,PM（2.5）concentrations（143–168 μg/m^3） were 2-fold higher than NAAQS.Higher PM（2.5）concentrations（~ 150 μg/m^3） were measured during the pre-harvest and harvest at the urban site,while PM（2.5）concentrations significantly increased from 250 to400 μg m^（-3） at suburban and rural sites with widespread biomass burning. At all sites,PM（2.5）components were dominated by organic carbon（OC） and followed by soluble component sulfate（SO4^（2-））,ammonium（NH4~＋） and nitrate（NO3^-）. Compared with rural sites,urban site had a higher mineral contribution and lower potassium（K~＋and K） contribution to PM（2.5）.Severe atmospheric haze events that occurred from October 21 to 23 were attributed to strong source emissions（e.g.,biomass burning） and unfavorable air diffusion conditions.Furthermore,coal burning originating from winter heating supply beginning on October 18 increased the atmospheric pollutant emissions. For entire crop harvest period,the Positive Matrix Factorization（PMF） analysis indicated five important emission contributors in the Changchun region,as follows： secondary aerosol（39%）,biomass burning（20%）,supply heating（18%）,soil/road dust（14%） and traffic（9%）.展开更多
MoS2 is layered semiconductor with indirect band-gap of 1.2 eV[1]. Monolayer MoS2 is one layer of Mo atoms sandwiched between two layers of S atoms. The thickness of monolayer MoS2 is 0.65 nm. Monolayer MoS2 has direc...MoS2 is layered semiconductor with indirect band-gap of 1.2 eV[1]. Monolayer MoS2 is one layer of Mo atoms sandwiched between two layers of S atoms. The thickness of monolayer MoS2 is 0.65 nm. Monolayer MoS2 has direct band-gap (1.8 eV). Because of the unique electrical, optical, and mechanical properties, monolayer MoS2 has promising application prospects in nanoelectronic and optolelectronic devices. Considering the radiation environment which these devices work in, it is necessary to estimate the radiation resistance ability of MoS2.展开更多
Recently,the irradiation effects in nanomaterials have been a hot topic in nanoscience.Although irradiationinduced damages have been studying for a long time,very limited research has been performed on the damages ind...Recently,the irradiation effects in nanomaterials have been a hot topic in nanoscience.Although irradiationinduced damages have been studying for a long time,very limited research has been performed on the damages induced by MeV-energy heavy ions in gold nanowires(NWs).In this work,we report a study of the irradiation effects on single crystalline gold NWs,which are fabricated electrochemically in the etched ion track templates.The as-prepared gold NWs on the Au/Cu substrate were characterized by SEM after dissolving the polycarbonate(PC)template,as shown in Fig.1(a).Gold NWs with diameters from 20 to 90 nm were fabricated to study the size dependence of irradiation damage induced by the heavy ions.To guarantee that the different NWs could obtain the same irradiation fluence,the NWs with different diameters were mixed together and transferred to the TEM grid,as shown in Fig.1(b).展开更多
基金financially supported by the National Natural Science Foundation of China (Nos.41205106,41275158)
文摘This study presents the observations of PM10 and PM2.5 concentrations at an agricultural site from April to October 2012 in Dehui city,China.Ambient air was sampled by filter-based samplers and online PM monitors.The filter samples were analyzed to determine the abundance of ionic/inorganic elements,organic carbon（OC） and elemental carbon（EC）.The daily PM10 concentrations varied significantly over the monitoring period,with an average of168 ± 63（in the range of 52-277） μg/m^3 during the land preparation/planting period（26 April-15 June）,85 ± 65（36-228） μg/m^3 during the growing season（16 June-25 September）,and 207 ±88（103-310） μg/m^3 during the harvest period（26 September-31 October）.PM2.5 accounted for44%,56%and 66%of atmospheric PM10 during these periods,respectively.The PM10 diurnal variation showed a distinct peak from 16：00 to 21：00（LST） during the growing and harvesting seasons,while a gradual increase throughout the daytime until 17：00 was observed during tilling season.Mineral dust elements（Al,Ca,Fe,and Mg） dominated the PM10 chemical composition during the tilling season;OC,NO3^-,SO4^（2-） and NH4~＋ during the growing season;and carbonaceous species（i.e.,OC and EC） during the harvesting season.Our results indicate that the soil particles emitted by farm tillage and organic matter released from straw burning are the two most significant sources of PM10 emissions contributing to the recurring high pollution events in this region.Therefore,development of agricultural PM inventories from soil tillage and straw burning is prioritized to support air quality modeling.
基金financially supported by the National Natural Science Foundation of China(Nos.41205106,41275158)
文摘This study presents the mass concentrations of PM（2.5）,O3,SO2 and NOxat one urban,one suburban and two rural locations in the Changchun region from September 25 to October 272013. Major chemical components of PM（2.5）at the four sites were daily sampled and analyzed. Most of daily concentrations of SO2（7–82 μg/m^3）,O3（27–171 μg/m^3） and NOx（14–213 μg/m^3） were below the limits of the National Ambient Air Quality Standard（NAAQS）in China. However,PM（2.5）concentrations（143–168 μg/m^3） were 2-fold higher than NAAQS.Higher PM（2.5）concentrations（~ 150 μg/m^3） were measured during the pre-harvest and harvest at the urban site,while PM（2.5）concentrations significantly increased from 250 to400 μg m^（-3） at suburban and rural sites with widespread biomass burning. At all sites,PM（2.5）components were dominated by organic carbon（OC） and followed by soluble component sulfate（SO4^（2-））,ammonium（NH4~＋） and nitrate（NO3^-）. Compared with rural sites,urban site had a higher mineral contribution and lower potassium（K~＋and K） contribution to PM（2.5）.Severe atmospheric haze events that occurred from October 21 to 23 were attributed to strong source emissions（e.g.,biomass burning） and unfavorable air diffusion conditions.Furthermore,coal burning originating from winter heating supply beginning on October 18 increased the atmospheric pollutant emissions. For entire crop harvest period,the Positive Matrix Factorization（PMF） analysis indicated five important emission contributors in the Changchun region,as follows： secondary aerosol（39%）,biomass burning（20%）,supply heating（18%）,soil/road dust（14%） and traffic（9%）.
文摘MoS2 is layered semiconductor with indirect band-gap of 1.2 eV[1]. Monolayer MoS2 is one layer of Mo atoms sandwiched between two layers of S atoms. The thickness of monolayer MoS2 is 0.65 nm. Monolayer MoS2 has direct band-gap (1.8 eV). Because of the unique electrical, optical, and mechanical properties, monolayer MoS2 has promising application prospects in nanoelectronic and optolelectronic devices. Considering the radiation environment which these devices work in, it is necessary to estimate the radiation resistance ability of MoS2.
文摘Recently,the irradiation effects in nanomaterials have been a hot topic in nanoscience.Although irradiationinduced damages have been studying for a long time,very limited research has been performed on the damages induced by MeV-energy heavy ions in gold nanowires(NWs).In this work,we report a study of the irradiation effects on single crystalline gold NWs,which are fabricated electrochemically in the etched ion track templates.The as-prepared gold NWs on the Au/Cu substrate were characterized by SEM after dissolving the polycarbonate(PC)template,as shown in Fig.1(a).Gold NWs with diameters from 20 to 90 nm were fabricated to study the size dependence of irradiation damage induced by the heavy ions.To guarantee that the different NWs could obtain the same irradiation fluence,the NWs with different diameters were mixed together and transferred to the TEM grid,as shown in Fig.1(b).
