Showing papers by "Congrong He published in 2017"

Sources and dynamics of fluorescent particles in hospitals

Abstract: Fluorescent particles can be markers of bioaerosols and are therefore relevant to nosocomial infections. To date, little research has focused on fluorescent particles in occupied indoor environments, particularly hospitals. In this study, we aimed to determine the spatial and temporal variation of fluorescent particles in two large hospitals in Brisbane, Australia (one for adults and one for children). We used an Ultraviolet Aerodynamic Particle Sizer (UVAPS) to identify fluorescent particle sources, as well as their contribution to total particle concentrations. We found that the average concentrations of both fluorescent and non-fluorescent particles were higher in the adults' hospital (0.06×106 and 1.20×106 particles/m3, respectively) than in the children's hospital (0.03×106 and 0.33×106 particles/m3, respectively) (P<.01). However, the proportion of fluorescent particles was higher in the children's hospital. Based on the concentration results and using activity diaries, we were able to identify sources of particle production within the two hospitals. We demonstrated that particles can be easily generated by a variety of everyday activities, which are potential sources of exposure to pathogens. Future studies to further investigate their role in nosocomial infection are warranted.

Observations of particles at their formation sizes in Beijing, China

Abstract: . New particle formation (NPF) has been observed in many highly polluted environments of South East Asia, including Beijing, where the extent of its contribution to intense haze events is still an open question. Estimated characteristics of NPF events, such as their starting times and formation and growth rates of particles, are more accurate when the detection range of particles extends to smaller sizes. In order to understand the very first steps of particle formation, we used a neutral cluster and air ion spectrometer (NAIS) to investigate particle characteristics at sizes exactly at which atmospheric nucleation and cluster activity occurs. Observations over a continuous 3-month period in Beijing showed 26 NPF events. These events generally coincided with periods with relatively clean air when the wind direction was from the less industrialised north. No NPF events were observed when the daily mean PM2. 5 concentration exceeded 43 µg m−3, which was the upper threshold for particle formation in Beijing. The fraction of particles that are charged in the size range 2–42 nm was normally about 15 %. However, this fraction increased to 20–30 % during haze events and decreased to below 10 % during NPF events. With the NAIS, we very precisely determined the starting times of NPF to a greater accuracy than has been possible in Beijing before and provided a temporal distribution of NPF events with a maximum at about 08:30 LT. Particle formation rates varied between 12 and 38 cm−3 s−1. Particle growth rates were estimated to be in the range of 0.5–9.0 nm h−1. These results are more reliable than previous studies in Beijing as the measurements were conducted for the first time at the exact sizes at which clusters form into particles and provide useful insight into the formation of haze events.

A pilot study of traditional indoor biomass cooking and heating in rural Bhutan: gas and particle concentrations and emission rates.

Abstract: Free to read on publisher website Although many studies have reported the health effects of biomass fuels in developing countries, relatively few have quantitatively characterized emissions from biomass stoves during cooking and heating. The aim of this pilot study was to characterize the emission characteristics of different biomass stoves in four rural houses in Bhutan during heating (metal chimney stove), rice cooking (traditional mud stove), fodder preparation (stone tripod stove) and liquor distillation (traditional mud stove). Three stage measurements (before, during and after the activity had ceased) were conducted for PM2.5, particle number (PN), CO and CO2. When stoves were operated, the pollutant concentrations were significantly elevated above background levels, by an average of 40 and 18 times for PM2.5 and CO, respectively. Emission rates (mg/min) ranged from 1.07×102 (PM2.5) and 3.50×102 (CO) for the stone tripod stove during fodder preparation to 6.20×102 (PM2.5) and 2.22×103 (CO) for the traditional mud stove during liquor distillation. Usable PN data was only available for one house, during heating using a metal chimney stove, which presented an emission rate of 3.24×1013 particles/min. Interventions to control household air pollution in Bhutan, in order to reduce the health risks associated with cooking and heating are recommended.

An investigation on particle emission from a new laser printer using an environmental chamber

Abstract: In this study, emissions of ultrafine particles from a new laser printer were evaluated as a function of toner coverage, number of pages printed, fuser temperature and cartridge rotation during different printing orders. Eight combinations of printing jobs were specifically designed to represent eight printing orders. The toner coverage was found to be an important factor affecting particle emissions from the printer. The printing job without toner coverage (0%) acted as a cleaning process, which would tentatively reduce particle emissions in the next job. Particles generated in printing job with toner coverage (5%) could superimpose onto those emitted from the next job, leading to higher particle number emission in the next job than the previous one. Apart from toner coverage, cartridge rotation was an important factor enhancing particle emissions. Cartridge in rotation mode with/without toner coverage could both cause particle emissions and high fuser temperature. The relationship between the particle e...

What are the driving factors influencing the size distribution of airborne synthetic clay particles emitted from a jet milling process

Abstract: In the field of workplace air quality, measuring and analyzing the size distribution of airborne particles to identify their sources and apportion their contribution has become widely accepted, however, the driving factors that influence this parameter, particularly for nanoparticles (< 100 nm), have not been thoroughly determined. Identification of driving factors, and in turn, general trends in size distribution of emitted particles would facilitate the prediction of nanoparticles’ emission behavior and significantly contribute to their exposure assessment. In this study, a comprehensive analysis of the particle number size distribution data, with a particular focus on the ultrafine size range of synthetic clay particles emitted from a jet milling machine was conducted using the multi-lognormal fitting method. The results showed relatively high contribution of nanoparticles to the emissions in many of the tested cases, and also, that both surface treatment and feed rate of the machine are significant factors influencing the size distribution of the emitted particles of this size. In particular, applying surface treatments and increasing the machine feed rate have the similar effect of reducing the size of the particles, however, no general trend was found in variations of size distribution across different surface treatments and feed rates. The findings of our study demonstrate that for this process and other activities, where no general trend is found in the size distribution of the emitted airborne particles due to dissimilar effects of the driving factors, each case must be treated separately in terms of workplace exposure assessment and regulations.