The yellowed-leaf rate is one of the important variables in simulation models for thegrowth of spring wheat. Based on the field experiments (1985-1988), the evolution of yellowed-leafrate of spring wheat is analyzed. ...The yellowed-leaf rate is one of the important variables in simulation models for thegrowth of spring wheat. Based on the field experiments (1985-1988), the evolution of yellowed-leafrate of spring wheat is analyzed. The functional relationship between the yellowing process of greenleaves and the development stages of spring wheat is established. Based on modelling and correctingfor the yellowing proass of green leaves affected by temperature and moisture, the synthetic modelfor simulating the dynaniical evolution of yellowed-leaf rate is constructed. The numerical experi-inents show that the result of the modelling is satisfactory.展开更多
PM_(2.5)and O_(3) are two major issues hindering air quality improvement in China.However,the response of these two pollutants to anthropogenic emission variations in the real atmosphere was not yet well understood.He...PM_(2.5)and O_(3) are two major issues hindering air quality improvement in China.However,the response of these two pollutants to anthropogenic emission variations in the real atmosphere was not yet well understood.Here,we selected the short-term epidemic lockdown in Wuhu in 2022 as a case study and evaluated the impacts of meteorology and anthropogenic emission on PM_(2.5)and O_(3) using field observations combined with machine learning algorithms.The results showed that NO_(2) observed during the lockdown was 32.2±8.1μg/m^(3),10.1%lower than before the lockdown,and that NO_(2) continued to decrease by 19.2%after the lockdown.Notably,both PM_(2.5)and O_(3) concentrations were higher during the lockdown than before and after the lockdown.Random forest model revealed that meteorological conditions during the lockdown increased PM_(2.5)and O_(3) by 8.7%and 24.2%,respectively,but decreased NO_(2) by 6.4%.Atmospheric pressure and relative humidity were the main meteorological variables influencing PM_(2.5)and O_(3) variations,respectively.Scenario simulation analysis uncovered that anthropogenic emission reduction caused by the lockdown reduced NO_(2) by 19.7%,but increased PM_(2.5)and O_(3) by 6.3%and 26.8%,respectively.This was mainly due to the weakening titration effect of nitrogen oxides and enhanced atmospheric oxidation capacity,further increasing O_(3) and secondary PM_(2.5)production.Our results revealed that NO_(2) in Wuhu decreased significantly due to short-term epidemic lockdown,but PM_(2.5)and O_(3) pollution were not effectively reduced.To continuously improve future urban air quality,joint reductions in emissions from multiple anthropogenic sources and multiple pollutants are required.展开更多
Air pollution is among the most serious environmental and public health problems worldwide,especially in low and middle-income countries like Rwanda.This study explores the spatial and temporal variations of criteria ...Air pollution is among the most serious environmental and public health problems worldwide,especially in low and middle-income countries like Rwanda.This study explores the spatial and temporal variations of criteria air pollutants across Rwanda from 2019 to 2023,utilizing data from 18 national air quality monitoring stations and 16 weather stations.Results reveal that PM2.5 and PM10 concentrations exceeded WHO guidelines,with the mean reaching 90μg/m3(PM2.5)and 127μg/m3(PM10),predominantly in Kigali City,Northern,and Western provinces.CO concentration peaked in the Eastern province and Kigali.In contrast,NO_(2) and O3 were highest in the Central and Northern provinces.Over five years,NO_(2) showed a slight increase trend,while CO,O3,and SO_(2) displayed minor declines and remained in line with WHO guidelines.Diurnal variations highlighted morning(06:00-07:00 am)and evening(06:00-09:00 pm)pollutant peaks,driven by morning rush hour traffic,domestic stoves,and industrial activities.Border stations like Bugeshi-Rubavu recorded elevated pollutant levels due to cross-border emissions from the bordering countries.Seasonal analysis revealed higher pollutant levels during dry seasons,influenced by reduced rainfall and increased anthropogenic activities.CO concentration was positively correlated with temperature during MAM(r=0.69)due to increased biomass burning and agricultural emissions.Wind speed is negatively correlated with PM2.5 and PM10 in JJA,aiding pollutant dispersion,while PM2.5 is positively correlated with humidity in MAM(r=0.7),linked to secondary aerosol formation.These findings underscore the urgent need to improve air quality,particularly in urban and border regions,and address Rwanda’s transboundary pollution concerns.展开更多
In this study,we conducted an observation experiment from May 1 to June 30,2018 in Zhengzhou,a major city in central China,where ground ozone(O3)pollution has become serious in recent years.The concentrations of O3 an...In this study,we conducted an observation experiment from May 1 to June 30,2018 in Zhengzhou,a major city in central China,where ground ozone(O3)pollution has become serious in recent years.The concentrations of O3 and its precursors,as well as H2O_(2) and meteorological data were obtained from the urban site(Yanchang,YC),suburban(Zhengzhou University,ZZU)and background sites(Ganglishuiku,GLSK).Result showed that the rates of O3 concentration exceeded Chinese National Air Quality Standard GradeⅡ(93.3 ppbv)were 59.0%,52.5%,and 55.7%at the above three sites with good consistency,respectively,indicating that O3 pollution is a regional problem in Zhengzhou.The daily peak O3 appeared at 15:00-16:00,which was opposite to VOCs,NOx,and CO and consistent with H2O_(2).The exhaustive statistical analysis of meteorological factors and chemical effects on O3 formation at YC was advanced.The high concentration of precursors,high temperature,low relative humidity,and moderately high wind speed together with the wind direction dominated by south and southeast wind contribute to urban O3 episodes in Zhengzhou.O3 formation analysis showed that reactive alkenes such as isoprene and cis-2-butene contributed most to O3 formation.The VOCs/NOx ratio and smog production model were used to determine O3-VOC-NOx sensitivity.The O3 formation in Zhengzhou during early summer was mainly under VOC-limited and transition regions alternately,which implies that the simultaneous emission reduction of alkenes and NOx is effective in reducing O3 pollution in Zhengzhou.展开更多
The regional air quality modeling system RAMS-CMAQ was applied to simulate the aerosol concentration for the period 2045-2050 over China based on the downscaled meteorological field of three RCP scenarios from CESM(N...The regional air quality modeling system RAMS-CMAQ was applied to simulate the aerosol concentration for the period 2045-2050 over China based on the downscaled meteorological field of three RCP scenarios from CESM(NCAR’s Community Earth System Model)in CMIP5.The downscaling simulation of the meteorological field of the three RCP scenarios showed that,compared with that under RCP2.6,the difference in near-surface temperature between North and South China is weakened and the wind speed increases over North and South China and decreases over central China under RCP4.5 and RCP8.5.Under RCP2.6,from 2045 to 2050,the modeled average PM2.5 concentration is highest,with a value of 40-50μg m^(-3),over the North China Plain,part of the Yangtze River Delta,and the Sichuan Basin.Meanwhile,it is 30-40μg m^(-3)over central China and part of the Pearl River Delta.Compared with RCP2.6,PM2.5 increases by 4-12μg m^(-3)under both RCP4.5 and RCP8.5,of which the SO_(4)^(2-)and NH_(4)^+concentration increases under both RCP4.5 and RCP8.5;the NO^(3-)concentration decreases under RCP4.5 and increases under RCP8.5;and the black carbon concentration changes very slightly,and organic carbon concentration decreases,under RCP4.5 and RCP8.5,with some increase over part of Southwest and Southeast China under RCP8.5.The difference between RCP4.5 and RCP2.6 and the difference between RCP8.5 and RCP2.6 have similar annual variation for different aerosol species,indicating that the impact of climate change on different species tends to be consistent.展开更多
文摘The yellowed-leaf rate is one of the important variables in simulation models for thegrowth of spring wheat. Based on the field experiments (1985-1988), the evolution of yellowed-leafrate of spring wheat is analyzed. The functional relationship between the yellowing process of greenleaves and the development stages of spring wheat is established. Based on modelling and correctingfor the yellowing proass of green leaves affected by temperature and moisture, the synthetic modelfor simulating the dynaniical evolution of yellowed-leaf rate is constructed. The numerical experi-inents show that the result of the modelling is satisfactory.
基金supported by the National Natural Science Foundation of China(No.42207128)the Key Research Projects of Natural Science in Colleges and Universities of Anhui Province(No.KJ2021A0091)the Natural Science Foundation of Anhui Province(No.2008085MD111)。
文摘PM_(2.5)and O_(3) are two major issues hindering air quality improvement in China.However,the response of these two pollutants to anthropogenic emission variations in the real atmosphere was not yet well understood.Here,we selected the short-term epidemic lockdown in Wuhu in 2022 as a case study and evaluated the impacts of meteorology and anthropogenic emission on PM_(2.5)and O_(3) using field observations combined with machine learning algorithms.The results showed that NO_(2) observed during the lockdown was 32.2±8.1μg/m^(3),10.1%lower than before the lockdown,and that NO_(2) continued to decrease by 19.2%after the lockdown.Notably,both PM_(2.5)and O_(3) concentrations were higher during the lockdown than before and after the lockdown.Random forest model revealed that meteorological conditions during the lockdown increased PM_(2.5)and O_(3) by 8.7%and 24.2%,respectively,but decreased NO_(2) by 6.4%.Atmospheric pressure and relative humidity were the main meteorological variables influencing PM_(2.5)and O_(3) variations,respectively.Scenario simulation analysis uncovered that anthropogenic emission reduction caused by the lockdown reduced NO_(2) by 19.7%,but increased PM_(2.5)and O_(3) by 6.3%and 26.8%,respectively.This was mainly due to the weakening titration effect of nitrogen oxides and enhanced atmospheric oxidation capacity,further increasing O_(3) and secondary PM_(2.5)production.Our results revealed that NO_(2) in Wuhu decreased significantly due to short-term epidemic lockdown,but PM_(2.5)and O_(3) pollution were not effectively reduced.To continuously improve future urban air quality,joint reductions in emissions from multiple anthropogenic sources and multiple pollutants are required.
文摘Air pollution is among the most serious environmental and public health problems worldwide,especially in low and middle-income countries like Rwanda.This study explores the spatial and temporal variations of criteria air pollutants across Rwanda from 2019 to 2023,utilizing data from 18 national air quality monitoring stations and 16 weather stations.Results reveal that PM2.5 and PM10 concentrations exceeded WHO guidelines,with the mean reaching 90μg/m3(PM2.5)and 127μg/m3(PM10),predominantly in Kigali City,Northern,and Western provinces.CO concentration peaked in the Eastern province and Kigali.In contrast,NO_(2) and O3 were highest in the Central and Northern provinces.Over five years,NO_(2) showed a slight increase trend,while CO,O3,and SO_(2) displayed minor declines and remained in line with WHO guidelines.Diurnal variations highlighted morning(06:00-07:00 am)and evening(06:00-09:00 pm)pollutant peaks,driven by morning rush hour traffic,domestic stoves,and industrial activities.Border stations like Bugeshi-Rubavu recorded elevated pollutant levels due to cross-border emissions from the bordering countries.Seasonal analysis revealed higher pollutant levels during dry seasons,influenced by reduced rainfall and increased anthropogenic activities.CO concentration was positively correlated with temperature during MAM(r=0.69)due to increased biomass burning and agricultural emissions.Wind speed is negatively correlated with PM2.5 and PM10 in JJA,aiding pollutant dispersion,while PM2.5 is positively correlated with humidity in MAM(r=0.7),linked to secondary aerosol formation.These findings underscore the urgent need to improve air quality,particularly in urban and border regions,and address Rwanda’s transboundary pollution concerns.
基金the National Key Research and Development Program of China(No.2017YFC0212403)。
文摘In this study,we conducted an observation experiment from May 1 to June 30,2018 in Zhengzhou,a major city in central China,where ground ozone(O3)pollution has become serious in recent years.The concentrations of O3 and its precursors,as well as H2O_(2) and meteorological data were obtained from the urban site(Yanchang,YC),suburban(Zhengzhou University,ZZU)and background sites(Ganglishuiku,GLSK).Result showed that the rates of O3 concentration exceeded Chinese National Air Quality Standard GradeⅡ(93.3 ppbv)were 59.0%,52.5%,and 55.7%at the above three sites with good consistency,respectively,indicating that O3 pollution is a regional problem in Zhengzhou.The daily peak O3 appeared at 15:00-16:00,which was opposite to VOCs,NOx,and CO and consistent with H2O_(2).The exhaustive statistical analysis of meteorological factors and chemical effects on O3 formation at YC was advanced.The high concentration of precursors,high temperature,low relative humidity,and moderately high wind speed together with the wind direction dominated by south and southeast wind contribute to urban O3 episodes in Zhengzhou.O3 formation analysis showed that reactive alkenes such as isoprene and cis-2-butene contributed most to O3 formation.The VOCs/NOx ratio and smog production model were used to determine O3-VOC-NOx sensitivity.The O3 formation in Zhengzhou during early summer was mainly under VOC-limited and transition regions alternately,which implies that the simultaneous emission reduction of alkenes and NOx is effective in reducing O3 pollution in Zhengzhou.
基金supported by the Strategic Priority Research Program(A)of the Chinese Academy of Sciences grant number XDA19040204the National Natural Science Foundation of China grant number41830966the Major Scientific and Technological Innovation Projects of Shandong Province grant number 2018YFJH0901。
文摘The regional air quality modeling system RAMS-CMAQ was applied to simulate the aerosol concentration for the period 2045-2050 over China based on the downscaled meteorological field of three RCP scenarios from CESM(NCAR’s Community Earth System Model)in CMIP5.The downscaling simulation of the meteorological field of the three RCP scenarios showed that,compared with that under RCP2.6,the difference in near-surface temperature between North and South China is weakened and the wind speed increases over North and South China and decreases over central China under RCP4.5 and RCP8.5.Under RCP2.6,from 2045 to 2050,the modeled average PM2.5 concentration is highest,with a value of 40-50μg m^(-3),over the North China Plain,part of the Yangtze River Delta,and the Sichuan Basin.Meanwhile,it is 30-40μg m^(-3)over central China and part of the Pearl River Delta.Compared with RCP2.6,PM2.5 increases by 4-12μg m^(-3)under both RCP4.5 and RCP8.5,of which the SO_(4)^(2-)and NH_(4)^+concentration increases under both RCP4.5 and RCP8.5;the NO^(3-)concentration decreases under RCP4.5 and increases under RCP8.5;and the black carbon concentration changes very slightly,and organic carbon concentration decreases,under RCP4.5 and RCP8.5,with some increase over part of Southwest and Southeast China under RCP8.5.The difference between RCP4.5 and RCP2.6 and the difference between RCP8.5 and RCP2.6 have similar annual variation for different aerosol species,indicating that the impact of climate change on different species tends to be consistent.
