在干旱地区,降水中的氢氧稳定同位素组成常受到雨滴云下二次蒸发作用的影响而发生改变。基于全球降水同位素网(GNIP)在我国西北东部站点的数据并结合气象数据,分析雨滴二次蒸发作用发生的条件、季节特征、影响因素以及对降水氢氧稳定同...在干旱地区,降水中的氢氧稳定同位素组成常受到雨滴云下二次蒸发作用的影响而发生改变。基于全球降水同位素网(GNIP)在我国西北东部站点的数据并结合气象数据,分析雨滴二次蒸发作用发生的条件、季节特征、影响因素以及对降水氢氧稳定同位素组成的影响规律。研究表明:在我国西北东部,当近地表水汽压差(VPD)等于0.52 k Pa时,降水中氢氧稳定同位素组成规律发生显著改变。当VPD>0.52 k Pa时,地区降水线(LMWL)的斜率和截距与全球降水线(GMWL)无显著差别,且氘剩余(d-excess)也与VPD不存在显著相关关系。然而,当VPD>0.52 k Pa时,LMWL的斜率和截距显著地小于GMWL,d-excess与VPD存在显著的负相关关系。表明当VPD<0.52 k Pa时,保留了云层中热力学平衡分馏特征,而当VPD>0.52 k Pa时,降水氢氧稳定同位素经历了动力学非平衡分馏过程——云下雨滴在降落过程中二次蒸发作用。根据Tetens公式,当气温(t)<7.0℃时,空气饱和水汽压不可能超过0.52 k Pa,所以,当t<7.0℃时不可能发生雨滴二次蒸发过程。这样,在温带干旱地区,在t较低的冬半年降水中的δ18O只存在显著的温度效应,而在t较高的夏半年降水中的δ18O同时存在温度和降水效应。展开更多
Low molecular weight (LMW) organic acids are important and ubiquitous chemical constituents in the atmosphere.A comprehensive study of the chemical composition of precipitation was carried out from June 2007 to June 2...Low molecular weight (LMW) organic acids are important and ubiquitous chemical constituents in the atmosphere.A comprehensive study of the chemical composition of precipitation was carried out from June 2007 to June 2008 at a rural site in Anshun,in the west of Guizhou Province,China.During this period,118 rainwater samples were collected and the main LMW carboxylic acids were determined using ion chromatography.The average pH of rainwater was 4.89 which is a typical acidic value.The most abundant carboxylic acids were formic acid (volume weight mean concentration:8.77 μmol L-1) and acetic acid (6.90 μmol L-1),followed by oxalic acid (2.05 μmol L-1).The seasonal variation of concentrations and wet deposition fluxes of organic acids indicated that direct vegetation emissions were the main sources of the organic acids.Highest concentrations were observed in winter and were ascribed to the low winter rainfall and the contribution of other air pollution sources northeast of the study area.The ratio of formic and acetic acids in the precipitation ([F/A] T) was proposed as an indicator of pollution source.This suggested that the pollution resulted from direct emissions from natural or anthropogenic sources.Comparison with acid precipitation in other urban and rural areas in Guizhou showed that there was a decreasing contribution of LMW organic acids to free acidity and all anions in rainwater from urban to remote rural areas.Consequently,it is necessary to control emissions of organic acids to reduce the frequency of acid rain,especially in rural and remote areas.展开更多
The acid rain observation network of China Meteorological Administration was established in 1989 with 22 stations.From 1993 to 2005,more than 80 stations were included and maintained in the network.In 2006-2007,the nu...The acid rain observation network of China Meteorological Administration was established in 1989 with 22 stations.From 1993 to 2005,more than 80 stations were included and maintained in the network.In 2006-2007,the number of stations in the network went up to 294.In consideration of the data continuity,data used in this paper are the 14-yr observations of the 80 stations from 1993 to 2006.Based on the 14-yr observation of acid rain,analysis shows that the acid rain in China dominates in the vast regions south of the Yangtze River.Limited presence of acid rain is observed in the northern part of China.The 14-yr acid rain data reveal an expanding tendency for acid rain area,with the north of China being a growing zone,and the South China remaining virtually unchanged.The most severely polluted zone of acid rain gradually moves from Southwest China to Central China and the middle part of South China.With regard to the acid intensity of rain,the period of 1993-1998 bears the highest acid intensity;the period of 1999-2002 shows a bit weakening intensity;and in the period of 2003-2006,the acid intensity of rain increases again,basically up to the average acidity of the period of 1993-1998 by the end of 2006.In addition,rain acidity in the north of China increases markedly.As to the causes of the acid rain situation in China,this paper examined the sulfur dioxide emissions as well as the rainwater chemicals monitoring data.展开更多
The isotope-equipped GCMs （general circulation models） are useful tools to investigate the isoscape in precipitation and water vapor, especially for the regions without enough in-situ observations. To study the spat...The isotope-equipped GCMs （general circulation models） are useful tools to investigate the isoscape in precipitation and water vapor, especially for the regions without enough in-situ observations. To study the spatial distribution and seasonal variation of precipitation isotopic composition in arid central Asia, several isotope-equipped GCMs are applied, and the long-term observations in two stations are used to verify the GCM-simulated results. Generally, seasonality of isotopic composition can be well simulated in each GCM, and the values of 6180 in precipitation are larger in summer months （from April to October） and lower in winter months （from November to March）. Higher latitude usually shows lower values of 6180 in precipitation, and lower latitude has higher values. The values of 5180 are relatively low in the eastern section, and higher in the western section. Among these simulations, ECHAM is good at describing the isotopic composition in the study region, which can be seen from the mean absolute error （MAE） and root-mean-square error （RMSE）. The ECHAM-derived values of 5180 in precipitation positively correlate with the observed series, and the correlation coefficient based on ECHAM is the largest among these GCMs.展开更多
This paper reports the analysis results (including pH,conductivity and ion concentrations) of the precipitation samples collected at the Chinese Great Wall Station,Antarctica (62°13′S, 58°58′W,ASL10.0 m) i...This paper reports the analysis results (including pH,conductivity and ion concentrations) of the precipitation samples collected at the Chinese Great Wall Station,Antarctica (62°13′S, 58°58′W,ASL10.0 m) in 1998.The average pH value and conductivity were 5.62 and 85.16 μS/cm,respectively.The pH value and conductivity of precipitation were higher during autumn, but lower during other seasons.The major ions in the precipitation were C1- and Na+,followed by SO_4^(2-),Mg^(2+),Ca^(2+),K^+,NO_3^-,NH_4^+ with the lower concentrations in order.The positive correlation significantly existing between the major ions,except NO_3^- and NH_4^+,indicated that those major ions might come from same sources.The fact that the relative abundances of ions in precipitation were very close to that of seawater of Antarctic Ocean indicated that marine aerosol was the dominant source of the ions of precipitation.However,there were yet other sources which may contribute to Ca^(2+) ion in the precipitation.The precipitation at the area was characterized by marine type chemically.展开更多
文摘在干旱地区,降水中的氢氧稳定同位素组成常受到雨滴云下二次蒸发作用的影响而发生改变。基于全球降水同位素网(GNIP)在我国西北东部站点的数据并结合气象数据,分析雨滴二次蒸发作用发生的条件、季节特征、影响因素以及对降水氢氧稳定同位素组成的影响规律。研究表明:在我国西北东部,当近地表水汽压差(VPD)等于0.52 k Pa时,降水中氢氧稳定同位素组成规律发生显著改变。当VPD>0.52 k Pa时,地区降水线(LMWL)的斜率和截距与全球降水线(GMWL)无显著差别,且氘剩余(d-excess)也与VPD不存在显著相关关系。然而,当VPD>0.52 k Pa时,LMWL的斜率和截距显著地小于GMWL,d-excess与VPD存在显著的负相关关系。表明当VPD<0.52 k Pa时,保留了云层中热力学平衡分馏特征,而当VPD>0.52 k Pa时,降水氢氧稳定同位素经历了动力学非平衡分馏过程——云下雨滴在降落过程中二次蒸发作用。根据Tetens公式,当气温(t)<7.0℃时,空气饱和水汽压不可能超过0.52 k Pa,所以,当t<7.0℃时不可能发生雨滴二次蒸发过程。这样,在温带干旱地区,在t较低的冬半年降水中的δ18O只存在显著的温度效应,而在t较高的夏半年降水中的δ18O同时存在温度和降水效应。
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(KZCX2-YW-306-3)the National Natural Science Foundation of China(40721002,40573048 and 40872212)
文摘Low molecular weight (LMW) organic acids are important and ubiquitous chemical constituents in the atmosphere.A comprehensive study of the chemical composition of precipitation was carried out from June 2007 to June 2008 at a rural site in Anshun,in the west of Guizhou Province,China.During this period,118 rainwater samples were collected and the main LMW carboxylic acids were determined using ion chromatography.The average pH of rainwater was 4.89 which is a typical acidic value.The most abundant carboxylic acids were formic acid (volume weight mean concentration:8.77 μmol L-1) and acetic acid (6.90 μmol L-1),followed by oxalic acid (2.05 μmol L-1).The seasonal variation of concentrations and wet deposition fluxes of organic acids indicated that direct vegetation emissions were the main sources of the organic acids.Highest concentrations were observed in winter and were ascribed to the low winter rainfall and the contribution of other air pollution sources northeast of the study area.The ratio of formic and acetic acids in the precipitation ([F/A] T) was proposed as an indicator of pollution source.This suggested that the pollution resulted from direct emissions from natural or anthropogenic sources.Comparison with acid precipitation in other urban and rural areas in Guizhou showed that there was a decreasing contribution of LMW organic acids to free acidity and all anions in rainwater from urban to remote rural areas.Consequently,it is necessary to control emissions of organic acids to reduce the frequency of acid rain,especially in rural and remote areas.
基金Supported by the National Natural Science Foundation of China under Grant No. 40575058
文摘The acid rain observation network of China Meteorological Administration was established in 1989 with 22 stations.From 1993 to 2005,more than 80 stations were included and maintained in the network.In 2006-2007,the number of stations in the network went up to 294.In consideration of the data continuity,data used in this paper are the 14-yr observations of the 80 stations from 1993 to 2006.Based on the 14-yr observation of acid rain,analysis shows that the acid rain in China dominates in the vast regions south of the Yangtze River.Limited presence of acid rain is observed in the northern part of China.The 14-yr acid rain data reveal an expanding tendency for acid rain area,with the north of China being a growing zone,and the South China remaining virtually unchanged.The most severely polluted zone of acid rain gradually moves from Southwest China to Central China and the middle part of South China.With regard to the acid intensity of rain,the period of 1993-1998 bears the highest acid intensity;the period of 1999-2002 shows a bit weakening intensity;and in the period of 2003-2006,the acid intensity of rain increases again,basically up to the average acidity of the period of 1993-1998 by the end of 2006.In addition,rain acidity in the north of China increases markedly.As to the causes of the acid rain situation in China,this paper examined the sulfur dioxide emissions as well as the rainwater chemicals monitoring data.
基金National Natural Science Foundation of China,No.41161012,No.41461003National Basic Research Program of China,No.2013CBA01801
文摘The isotope-equipped GCMs （general circulation models） are useful tools to investigate the isoscape in precipitation and water vapor, especially for the regions without enough in-situ observations. To study the spatial distribution and seasonal variation of precipitation isotopic composition in arid central Asia, several isotope-equipped GCMs are applied, and the long-term observations in two stations are used to verify the GCM-simulated results. Generally, seasonality of isotopic composition can be well simulated in each GCM, and the values of 6180 in precipitation are larger in summer months （from April to October） and lower in winter months （from November to March）. Higher latitude usually shows lower values of 6180 in precipitation, and lower latitude has higher values. The values of 5180 are relatively low in the eastern section, and higher in the western section. Among these simulations, ECHAM is good at describing the isotopic composition in the study region, which can be seen from the mean absolute error （MAE） and root-mean-square error （RMSE）. The ECHAM-derived values of 5180 in precipitation positively correlate with the observed series, and the correlation coefficient based on ECHAM is the largest among these GCMs.
基金Sponsored by the Youth Meteorological Science Fund in the Ninth Five-Year Plan from China Meteorological Administration
文摘This paper reports the analysis results (including pH,conductivity and ion concentrations) of the precipitation samples collected at the Chinese Great Wall Station,Antarctica (62°13′S, 58°58′W,ASL10.0 m) in 1998.The average pH value and conductivity were 5.62 and 85.16 μS/cm,respectively.The pH value and conductivity of precipitation were higher during autumn, but lower during other seasons.The major ions in the precipitation were C1- and Na+,followed by SO_4^(2-),Mg^(2+),Ca^(2+),K^+,NO_3^-,NH_4^+ with the lower concentrations in order.The positive correlation significantly existing between the major ions,except NO_3^- and NH_4^+,indicated that those major ions might come from same sources.The fact that the relative abundances of ions in precipitation were very close to that of seawater of Antarctic Ocean indicated that marine aerosol was the dominant source of the ions of precipitation.However,there were yet other sources which may contribute to Ca^(2+) ion in the precipitation.The precipitation at the area was characterized by marine type chemically.
