Nitrogen oxides(NO_(x))are crucial in tropospheric photochemical ozone(O_(3))production and oxidation capacity.Currently,the widely used NO_(x)measurement technique is chemiluminescence(CL)(CL-NO_(x)),which tends to o...Nitrogen oxides(NO_(x))are crucial in tropospheric photochemical ozone(O_(3))production and oxidation capacity.Currently,the widely used NO_(x)measurement technique is chemiluminescence(CL)(CL-NO_(x)),which tends to overestimate NO_(2)due to atmospheric oxidation products of NO_(x)(i.e.,NO_(z)).We developed and characterized a NO_(x)measurement system using the cavity attenuated phase shift(CAPS)technique(CAPS-NO_(x)),which is free from interferences with nitrogen-containing species.The NO_(x)measured by the CAPS-NO_(x)and CL-NO_(x)analyzers were compared.Results show that both analyzers showed consistent measurement results for NO,but the NO_(2)measured by the CAPS-NO_(x)analyzer(NO_(2)_CAPS)was mostly lower than that measured by the CL-NO_(x)analyzer(NO_(2)_CL),which led to the deviations in O_(3)formation sensitivity regime and O_(x)(=O_(3)+NO_(2))sources(i.e.,regional background and photochemically produced O_(x))determined by the ozone production efficiencies(OPE)calculated from NO_(2)_CL and NO_(2)_CAPS.Overall,OPE_CL exceeded OPE_CAPS by 18.9%,which shifted 3 out of 13 observation days from the VOCs-limited to the transition regime when judging using OPE_CL,as compared to calculations using OPE_CAPS.During the observation period,days dominated by regional background O_(x)accounted for 46%and 62%when determined using NO_(2)_CL and NO_(2)_CAPS,respectively.These findings suggest that the use of the CL-NO_(x)analyzer tends to underestimate both the VOCs-limited regime and the regional background O_(x)dominated days.The newly built CAPS-NO_(x)analyzer here can promote the accurate measurement of NO_(2),which is meaningful for diagnosing O_(3)formation regimes and O_(x)sources.展开更多
A new instrument for measuring atmospheric nitrous acid（HONO） was developed,consisting of a double-wall glass stripping coil sampler coupled with ion chromatography（SC-IC）.SC-IC is featured by small size（50 ×...A new instrument for measuring atmospheric nitrous acid（HONO） was developed,consisting of a double-wall glass stripping coil sampler coupled with ion chromatography（SC-IC）.SC-IC is featured by small size（50 × 35 × 25 cm） and modular construction,including three independent parts：the sampling unit,the transfer and supporting unit,and the detection unit.High collection efficiency（〉 99%） was achieved with 25 μmol/L Na2CO3 as absorption solution even in the presence of highly acidic compounds.This instrument has a detection limit of 8 pptv at 15 min time resolution,with a measurement uncertainty of 7%.Potential interferences from NOx,NO2＋SO2,NO2＋VOCs,HONO＋O3,HNO3,peroxyacetyl nitrite（PAN） and particle nitrite were quantified in laboratory studies and were found to be insignificant under typical atmospheric conditions.Within the framework of the 3C-STAR project,inter-comparison between the SC-IC and LOPAP（long path liquid absorption photometer） was conducted at a rural site in the Pearl River Delta.Good agreement was achieved between the two instruments over three weeks.Both instruments determined a clear diurnal profile of ambient HONO concentrations from 0.1 to 2.5 ppbv.However,deviations were found for low ambient HONO concentrations（i.e.〈 0.3 ppbv）,which cannot be explained by previous investigated interference species.To accurately determine the HONO budget under illuminated conditions,more intercomparison of HONO measurement techniques is still needed in future studies,especially at low HONO concentrations.展开更多
Abundances of a range of air pollutants can be inferred from satellite UV-Vis spectroscopy measurements by using the unique absorption signatures of gas species.Here,we implemented several spectral fitting methods to ...Abundances of a range of air pollutants can be inferred from satellite UV-Vis spectroscopy measurements by using the unique absorption signatures of gas species.Here,we implemented several spectral fitting methods to retrieve tropospheric NO_(2),SO_(2),and HCHO from the ozone monitoring instrument(OMI),with radiative simulations providing necessary information on the interactions of scattered solar light within the atmosphere.We analyzed the spatial distribution and temporal trends of satellite-observed air pollutants over eastern China during 2005-2017,especially in heavily polluted regions.We found significant decreasing trends in NO_(2) and SO_(2) since 2011 over most regions,despite varying temporal features and turning points.In contrast,an overall increasing trend was identified for tropospheric HCHO over these regions in recent years.Furthermore,generalized additive models were implemented to understand the driving forces of air quality trends in China and assess the effectiveness of emission controls.Our results indicated that although meteorological parameters,such as wind,water vapor,solar radiation and temperature,mainly dominated the day-to-day and seasonal fluctuations in air pollutants,anthropogenic emissions played a unique role in the long-term variation in the ambient concentrations of NO_(2),SO_(2),and HCHO in the past 13 years.Generally,recent declines in NO_(2) and SO_(2) could be attributed to emission reductions due to effective air quality policies,and the opposite trends in HCHO may urge the need to control anthropogenic volatile organic compound(VOC)emissions.展开更多
The biology and ecology of biological soil crusts,a soil surface community of mosses,lichens,cyanobacteria,green algae,fungi,and bacteria,have only recently been a topic of research.Most efforts began in the western U...The biology and ecology of biological soil crusts,a soil surface community of mosses,lichens,cyanobacteria,green algae,fungi,and bacteria,have only recently been a topic of research.Most efforts began in the western U.S.(Cameron,Harper,Rushforth,and St.Clair),Australia(Rogers),and Israel(Friedmann,Evenari,and Lange)in the late 1960s and 1970s(e.g.,Friedmann et al.1967;Evenari 1985,reviewed in Harper and Marble 1988).However,these groups worked independently of each other and,in fact,were often not aware of each other’s work.In addition,biological soil crust communities were seen as more a novelty than a critical component of dryland ecosystems.Since then,researchers have investigated many different aspects of these communities and have shown that although small to microscopic,biological soil crusts are critical in many ecological processes of deserts.They often cover most of desert soil surfaces and substantially mediate inputs and outputs from desert soils(Belnap et al.2003).They can be a large source of biodiversity for deserts,as they can contain more species than the surrounding vascular plant community(Rosentreter 1986).These communities are important in reducing soil erosion and increasing soil fertility through the capture of dust and the fixation of atmospheric nitrogen and carbon into forms available to other life forms(Elbert et al.2012).展开更多
基金supported by the Natural Science Foundation of Guangdong Province(No.2020A1515110526)the Key-Area Research and Development Programof Guangdong Province(No.2020B1111360003)the National Natural Science Foundation of China(No.42305096).
文摘Nitrogen oxides(NO_(x))are crucial in tropospheric photochemical ozone(O_(3))production and oxidation capacity.Currently,the widely used NO_(x)measurement technique is chemiluminescence(CL)(CL-NO_(x)),which tends to overestimate NO_(2)due to atmospheric oxidation products of NO_(x)(i.e.,NO_(z)).We developed and characterized a NO_(x)measurement system using the cavity attenuated phase shift(CAPS)technique(CAPS-NO_(x)),which is free from interferences with nitrogen-containing species.The NO_(x)measured by the CAPS-NO_(x)and CL-NO_(x)analyzers were compared.Results show that both analyzers showed consistent measurement results for NO,but the NO_(2)measured by the CAPS-NO_(x)analyzer(NO_(2)_CAPS)was mostly lower than that measured by the CL-NO_(x)analyzer(NO_(2)_CL),which led to the deviations in O_(3)formation sensitivity regime and O_(x)(=O_(3)+NO_(2))sources(i.e.,regional background and photochemically produced O_(x))determined by the ozone production efficiencies(OPE)calculated from NO_(2)_CL and NO_(2)_CAPS.Overall,OPE_CL exceeded OPE_CAPS by 18.9%,which shifted 3 out of 13 observation days from the VOCs-limited to the transition regime when judging using OPE_CL,as compared to calculations using OPE_CAPS.During the observation period,days dominated by regional background O_(x)accounted for 46%and 62%when determined using NO_(2)_CL and NO_(2)_CAPS,respectively.These findings suggest that the use of the CL-NO_(x)analyzer tends to underestimate both the VOCs-limited regime and the regional background O_(x)dominated days.The newly built CAPS-NO_(x)analyzer here can promote the accurate measurement of NO_(2),which is meaningful for diagnosing O_(3)formation regimes and O_(x)sources.
基金supported by the National Natural Science Foundation of China (Major Program:No.21190052,40675072,and Innovative Research Group:No.41121004)this study was also supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB05010500)
文摘A new instrument for measuring atmospheric nitrous acid（HONO） was developed,consisting of a double-wall glass stripping coil sampler coupled with ion chromatography（SC-IC）.SC-IC is featured by small size（50 × 35 × 25 cm） and modular construction,including three independent parts：the sampling unit,the transfer and supporting unit,and the detection unit.High collection efficiency（〉 99%） was achieved with 25 μmol/L Na2CO3 as absorption solution even in the presence of highly acidic compounds.This instrument has a detection limit of 8 pptv at 15 min time resolution,with a measurement uncertainty of 7%.Potential interferences from NOx,NO2＋SO2,NO2＋VOCs,HONO＋O3,HNO3,peroxyacetyl nitrite（PAN） and particle nitrite were quantified in laboratory studies and were found to be insignificant under typical atmospheric conditions.Within the framework of the 3C-STAR project,inter-comparison between the SC-IC and LOPAP（long path liquid absorption photometer） was conducted at a rural site in the Pearl River Delta.Good agreement was achieved between the two instruments over three weeks.Both instruments determined a clear diurnal profile of ambient HONO concentrations from 0.1 to 2.5 ppbv.However,deviations were found for low ambient HONO concentrations（i.e.〈 0.3 ppbv）,which cannot be explained by previous investigated interference species.To accurately determine the HONO budget under illuminated conditions,more intercomparison of HONO measurement techniques is still needed in future studies,especially at low HONO concentrations.
基金supported by grants from the National Natural Science Foundation of China(Nos.41722501,91544212,51778596,41575021,41875043,and 41977184)the National Key Research and Development Program of China(Nos.2018YFC0213104,2017YFC0210002,and 2016YFC0203302)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23020301)the National Key Project for Causes and Control of Heavy Air Pollution(Nos.DQGG0102 and DQGG0205)the Major Projects of High Resolution Earth Observation Systems of National Science and Technology(05-Y30B01-9001-19/20-1).
文摘Abundances of a range of air pollutants can be inferred from satellite UV-Vis spectroscopy measurements by using the unique absorption signatures of gas species.Here,we implemented several spectral fitting methods to retrieve tropospheric NO_(2),SO_(2),and HCHO from the ozone monitoring instrument(OMI),with radiative simulations providing necessary information on the interactions of scattered solar light within the atmosphere.We analyzed the spatial distribution and temporal trends of satellite-observed air pollutants over eastern China during 2005-2017,especially in heavily polluted regions.We found significant decreasing trends in NO_(2) and SO_(2) since 2011 over most regions,despite varying temporal features and turning points.In contrast,an overall increasing trend was identified for tropospheric HCHO over these regions in recent years.Furthermore,generalized additive models were implemented to understand the driving forces of air quality trends in China and assess the effectiveness of emission controls.Our results indicated that although meteorological parameters,such as wind,water vapor,solar radiation and temperature,mainly dominated the day-to-day and seasonal fluctuations in air pollutants,anthropogenic emissions played a unique role in the long-term variation in the ambient concentrations of NO_(2),SO_(2),and HCHO in the past 13 years.Generally,recent declines in NO_(2) and SO_(2) could be attributed to emission reductions due to effective air quality policies,and the opposite trends in HCHO may urge the need to control anthropogenic volatile organic compound(VOC)emissions.
基金We thank Robert Losey for comments on an earlier version of this paper and are grateful to Ken Lertzman,Nancy Turner,and Douglas Deur for ongoing discussions about traditional resource management systems.Many thanks to Nicole Smith,Nathan Cardinal,Dale Croes,Amy Groesbeck,Robert Losey,and Alan Hobler for contributions of information and/or photographs.This research was funded in part by a SSHRC CGS Doctoral Scholarship(Caldwell).
文摘The biology and ecology of biological soil crusts,a soil surface community of mosses,lichens,cyanobacteria,green algae,fungi,and bacteria,have only recently been a topic of research.Most efforts began in the western U.S.(Cameron,Harper,Rushforth,and St.Clair),Australia(Rogers),and Israel(Friedmann,Evenari,and Lange)in the late 1960s and 1970s(e.g.,Friedmann et al.1967;Evenari 1985,reviewed in Harper and Marble 1988).However,these groups worked independently of each other and,in fact,were often not aware of each other’s work.In addition,biological soil crust communities were seen as more a novelty than a critical component of dryland ecosystems.Since then,researchers have investigated many different aspects of these communities and have shown that although small to microscopic,biological soil crusts are critical in many ecological processes of deserts.They often cover most of desert soil surfaces and substantially mediate inputs and outputs from desert soils(Belnap et al.2003).They can be a large source of biodiversity for deserts,as they can contain more species than the surrounding vascular plant community(Rosentreter 1986).These communities are important in reducing soil erosion and increasing soil fertility through the capture of dust and the fixation of atmospheric nitrogen and carbon into forms available to other life forms(Elbert et al.2012).
