PM2.5 pollution in sive attention in recent years, Beijing has attracted extensive attention in recent years, but research on the detailed spatiotemporal characteristics of PM2.5 is critically lacking for effective po...PM2.5 pollution in sive attention in recent years, Beijing has attracted extensive attention in recent years, but research on the detailed spatiotemporal characteristics of PM2.5 is critically lacking for effective pollution control. In our study, hourly PM2.5 concentration data of 35 fixed monitoring sites in Beijing were collected continuously from October 2012 to September 2013, for exploring the diurnal and seasonal characteristics of PM2.5 at traffic, urban, and background environments. Spatial trend and regional contribution of PM2.5 under different pollution levels were also investigated. Results show that the average PM2.5 concentration of all the 35 sites （including 5 traffic sites） was 88.6 μg/m^3. Although PM2.5 varied largely with the site location and seasons, a clear spatial trend could be observed with the PM2.5 concentration decreasing linearly from south to north, with a gradient of -0.46 μg/m^3/km for average days, -0.83 μg/m^3/km for heavily-severely polluted days, -0.52μg/m^3/km at lightly-moderately polluted days, and -0.26 μg/m^3/km for excellent-good days. PM2.5 at traffic sites was varied, but was generally over 10 % higher than at the nearby urban assessment sites.展开更多
The paper presents a simple model for outdoor air contaminant transmission into occupied rooms. In the model, several factors such as filtration, ventilation, deposition, re-emission, outdoor concentration and indoor ...The paper presents a simple model for outdoor air contaminant transmission into occupied rooms. In the model, several factors such as filtration, ventilation, deposition, re-emission, outdoor concentration and indoor sources are included. The model results show that the air exchange rate plays an important role in the transmission of outdoor contaminants into the indoor environment. The model shows that increasing the value of the filtration efficiency decreases the mass concentration of indoor particles. In addition, if outdoor aerosol particles have a periodic behaviour, indoor aerosol particles also behave periodically but smoother. Indoor sources are found to be able to increase indoor concentrations greatly and continuously.展开更多
In light of concerns over climate change and increasing levels of CO2 in the atmosphere,it is of importance to investigate soil organic matter in Mediterranean forests at a profile scale.In-depth studies of the organi...In light of concerns over climate change and increasing levels of CO2 in the atmosphere,it is of importance to investigate soil organic matter in Mediterranean forests at a profile scale.In-depth studies of the organic fraction are also of interest to improve understanding of carbon balance and to facilitate modelling of carbon fixation in forest soils.This research evaluates the relationships between diverse parameters such as colour,content,and form of soil organic matter(SOM).Two Quercus pyrenica ecosystems with soils classified as inceptisols with a xeric or dry moisture regime,and developed under a Mediterranean climate in Spain,were used to characterize SOM through the complete sequence of layers of the soil profile.The differentiating factor between the two ecosystems was slope gradient.Characterization was done using characteristics of humic substances(HS)as indicators of SOM turnover in inceptisols.Infrared analysis was used to further characterize the humic acids.As soil colour measurements are a tool for soil type classification and soil organic carbon prediction,the relation between HS colour measured by reflection and by transmission was determined in order to establish a relationship between measurement techniques.Infrared analysis and colour provided evidence of a different level of stabilization of HS from both soils,and between the different horizons.Oxidation of humic acids was found to be greater in deeper horizons than in the surface layers.An inverse relationship between HS colour measured by reflection and by transmission was revealed.Both soils showed a clear trend in which horizons presenting lower absorbance numbers showed higher figures of hue and value.A more marked accumulation of humified compounds was found in pedons,(the smallest unit or volume of soil that contains all the soil types),in the less steep slope.This might be explained in terms of the physiographic position affecting infiltration behavior and exposure to runoff.展开更多
Photosynthesis is related to dry matter accumulation in aboveground part of rice plant,which is the direct factor of production.This study carried out research on physiological indicators and the relationship between ...Photosynthesis is related to dry matter accumulation in aboveground part of rice plant,which is the direct factor of production.This study carried out research on physiological indicators and the relationship between photosynthesis and dry matter accumulation under different water management in paddy field.In general,the photosynthetic and physiological indicators showed the trend of increasing and then decreasing with the growth stage of rice.Experimental results showed that,chlorophyll content and leaf area index of rice leaves showed a quadratic curve positive correlation.Canopy light transmission reached the maximum at heading-flowering stage,and it had quadratic relationship with leaf area index,while it showed extremely positive correlation under rain-water storage irrigation mode.Photosynthetic rate(Pn)and transpiration rate(Tr)had quadratic curve positive correlation with chlorophyll content.The water condition under rain-water storage was favorable for dry matter accumulation in panicle.After multiple regression and main factor analysis,canopy light transmission,light transmission coefficient and Pn were main factors related to dry matter accumulation.The conclusions in this article were helpful for promoting rice yield in practice.展开更多
基金supported by the Key Research Program of Chinese Academy of Sciences (KZZDEW-13)the Gong-Yi Program of Chinese Ministry of Environmental Protection (200909016, 201209008)+1 种基金the National Natural Science Foundation of China (21377127, 41201038)the President Fund of University of Chinese Academy of Sciences (UCAS)
文摘PM2.5 pollution in sive attention in recent years, Beijing has attracted extensive attention in recent years, but research on the detailed spatiotemporal characteristics of PM2.5 is critically lacking for effective pollution control. In our study, hourly PM2.5 concentration data of 35 fixed monitoring sites in Beijing were collected continuously from October 2012 to September 2013, for exploring the diurnal and seasonal characteristics of PM2.5 at traffic, urban, and background environments. Spatial trend and regional contribution of PM2.5 under different pollution levels were also investigated. Results show that the average PM2.5 concentration of all the 35 sites （including 5 traffic sites） was 88.6 μg/m^3. Although PM2.5 varied largely with the site location and seasons, a clear spatial trend could be observed with the PM2.5 concentration decreasing linearly from south to north, with a gradient of -0.46 μg/m^3/km for average days, -0.83 μg/m^3/km for heavily-severely polluted days, -0.52μg/m^3/km at lightly-moderately polluted days, and -0.26 μg/m^3/km for excellent-good days. PM2.5 at traffic sites was varied, but was generally over 10 % higher than at the nearby urban assessment sites.
基金Funded by Beijing Higher Education Young Elite Teacher Project(No.YETP0371)National Key Technologies R&D Program of China(No.2012BAJ02B02)
文摘The paper presents a simple model for outdoor air contaminant transmission into occupied rooms. In the model, several factors such as filtration, ventilation, deposition, re-emission, outdoor concentration and indoor sources are included. The model results show that the air exchange rate plays an important role in the transmission of outdoor contaminants into the indoor environment. The model shows that increasing the value of the filtration efficiency decreases the mass concentration of indoor particles. In addition, if outdoor aerosol particles have a periodic behaviour, indoor aerosol particles also behave periodically but smoother. Indoor sources are found to be able to increase indoor concentrations greatly and continuously.
文摘In light of concerns over climate change and increasing levels of CO2 in the atmosphere,it is of importance to investigate soil organic matter in Mediterranean forests at a profile scale.In-depth studies of the organic fraction are also of interest to improve understanding of carbon balance and to facilitate modelling of carbon fixation in forest soils.This research evaluates the relationships between diverse parameters such as colour,content,and form of soil organic matter(SOM).Two Quercus pyrenica ecosystems with soils classified as inceptisols with a xeric or dry moisture regime,and developed under a Mediterranean climate in Spain,were used to characterize SOM through the complete sequence of layers of the soil profile.The differentiating factor between the two ecosystems was slope gradient.Characterization was done using characteristics of humic substances(HS)as indicators of SOM turnover in inceptisols.Infrared analysis was used to further characterize the humic acids.As soil colour measurements are a tool for soil type classification and soil organic carbon prediction,the relation between HS colour measured by reflection and by transmission was determined in order to establish a relationship between measurement techniques.Infrared analysis and colour provided evidence of a different level of stabilization of HS from both soils,and between the different horizons.Oxidation of humic acids was found to be greater in deeper horizons than in the surface layers.An inverse relationship between HS colour measured by reflection and by transmission was revealed.Both soils showed a clear trend in which horizons presenting lower absorbance numbers showed higher figures of hue and value.A more marked accumulation of humified compounds was found in pedons,(the smallest unit or volume of soil that contains all the soil types),in the less steep slope.This might be explained in terms of the physiographic position affecting infiltration behavior and exposure to runoff.
基金This research was financially supported in part by the National Natural Science Foundation of China(Grant No.52009044,51779093)partly by the High-level Talent Research Project of North China University of Water Resources and Electric Power(Grant No.201705017)+1 种基金partly by the National Key Research and Development Program(Grant No.2019YFC0408803)partly by Key Laboratory of Efficient Irrigation-Drainage and Agricultural Soil-Water Environment in Southern China(Hohai University),Ministry of Education(Grant No.2017B20414-2)
文摘Photosynthesis is related to dry matter accumulation in aboveground part of rice plant,which is the direct factor of production.This study carried out research on physiological indicators and the relationship between photosynthesis and dry matter accumulation under different water management in paddy field.In general,the photosynthetic and physiological indicators showed the trend of increasing and then decreasing with the growth stage of rice.Experimental results showed that,chlorophyll content and leaf area index of rice leaves showed a quadratic curve positive correlation.Canopy light transmission reached the maximum at heading-flowering stage,and it had quadratic relationship with leaf area index,while it showed extremely positive correlation under rain-water storage irrigation mode.Photosynthetic rate(Pn)and transpiration rate(Tr)had quadratic curve positive correlation with chlorophyll content.The water condition under rain-water storage was favorable for dry matter accumulation in panicle.After multiple regression and main factor analysis,canopy light transmission,light transmission coefficient and Pn were main factors related to dry matter accumulation.The conclusions in this article were helpful for promoting rice yield in practice.
