Halocarbon emissions from China are of great interest to both policy makers and academia. To estimate halocarbon emissions with interspecies correlation methods, previous studies adopted CO, HCFC-22 or other species as reference tracers. However, few of these studies compared the results using different reference tracers. In this study, chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) and carbon monoxide (CO) concentrations were measured at a monitoring site in northern China in 2009/2010, and halocarbon emissions were estimated using an interspecies correlation method. A comparison was performed of the correlations between estimated halocarbon emissions and two reference tracers, CO and HCFC-22. The results show that both species are significantly correlated with most of the target species (P < 0.01), whereas HCFC-22 shows better correlations than does CO. Our estimated halocarbon emissions for 2009 agree within uncertainties with results obtained with other approaches, including inverse modeling and interspecies correlation methods. The emissions for 2001–2009 estimated in different studies (all using top–down approaches) show a clear decrease in the emissions of CFC-11 and CFC-12 and an increase in the emissions of HCFC-22, HCFC-141b and HCFC-142b in China. Moreover, the combined Ozone Depletion Potential weighted emissions of CFCs are much greater than the reported consumption, whereas the emissions of HCFC counterparts are not more than one-half of the reported consumption. This result suggests that HCFCs are being accumulated in banks and that these banks will sustain elevated in China.
Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 +/- 0.13 g cm(-3) and 1.62 +/- 0.38 g cm(-3) for PM1.8 and 1.73 +/- 0.14 g cm(-3) and 1.67 +/- 0.37 g cm(-3) for PM10. Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm(-3) at the size of 0.1 mu m to above 2.0 g cm(-3) in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 mu m during clean episodes. Dynamic Shape Factors varied within the range of 0.95-1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles.
Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 +/- 0.13 g cm(-3) and 1.62 +/- 0.38 g cm(-3) for PM1.8 and 1.73 +/- 0.14 g cm(-3) and 1.67 +/- 0.37 g cm(-3) for PM10. Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm(-3) at the size of 0.1 mu m to above 2.0 g cm(-3) in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 mu m during clean episodes. Dynamic Shape Factors varied within the range of 0.95-1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles.
Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 +/- 0.13 g cm(-3) and 1.62 +/- 0.38 g cm(-3) for PM1.8 and 1.73 +/- 0.14 g cm(-3) and 1.67 +/- 0.37 g cm(-3) for PM10. Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm(-3) at the size of 0.1 mu m to above 2.0 g cm(-3) in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 mu m during clean episodes. Dynamic Shape Factors varied within the range of 0.95-1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles.
Liu J, Liu C, Cole M, Belkin NJ, Zhang X. Exploring and predicting search task difficulty, in Proceedings of the 21st ACM international conference on Information and knowledge management.; 2012:1313–1322.
We performed measurements of nitrous acid (HONO) during the PRIDE-PRD2006 campaign in the Pearl River Delta region 60 km north of Guangzhou, China, for 4 weeks in June 2006. HONO was measured by a LOPAP in-situ instrument which was setup in one of the campaign supersites along with a variety of instruments measuring hydroxyl radicals, trace gases, aerosols, and meteorological parameters. Maximum diurnal HONO mixing ratios of 1-5 ppb were observed during the nights. We found that the nighttime build-up of HONO can be attributed to the heterogeneous NO2 to HONO conversion on ground surfaces and the OH + NO reaction. In addition to elevated nighttime mixing ratios, measured noontime values of approximate to 200 ppt indicate the existence of a daytime source higher than the OH + NO -> HONO reaction. Using the simultaneously recorded OH, NO, and HONO photolysis frequency, a daytime additional source strength of HONO (P-M) was calculated to be 0.77 ppb h(-1) on average. This value compares well to previous measurements in other environments. Our analysis of P-M provides evidence that the photolysis of HNO3 adsorbed on ground surfaces contributes to the HONO formation.
We performed measurements of nitrous acid (HONO) during the PRIDE-PRD2006 campaign in the Pearl River Delta region 60 km north of Guangzhou, China, for 4 weeks in June 2006. HONO was measured by a LOPAP in-situ instrument which was setup in one of the campaign supersites along with a variety of instruments measuring hydroxyl radicals, trace gases, aerosols, and meteorological parameters. Maximum diurnal HONO mixing ratios of 1–5 ppb were observed during the nights. We found that the nighttime build-up of HONO can be attributed to the heterogeneous NO2 to HONO conversion on ground surfaces and the OH + NO reaction. In addition to elevated nighttime mixing ratios, measured noontime values of ≈200 ppt indicate the existence of a daytime source higher than the OH + NO→HONO reaction. Using the simultaneously recorded OH, NO, and HONO photolysis frequency, a daytime additional source strength of HONO (PM) was calculated to be 0.77 ppb h−1 on average. This value compares well to previous measurements in other environments. Our analysis of PM provides evidence that the photolysis of HNO3 adsorbed on ground surfaces contributes to the HONO formation.