Biomass burning (BB) is a significant air pollution source, with global, regional and local impacts on air quality, public health and climate. Worldwide an extensive range of studies has been ...conducted on almost all the aspects of BB, including its specific types, on quantification of emissions and on assessing its various impacts. China is one of the countries where the significance of BB has been recognized, and a lot of research efforts devoted to investigate it, however, so far no systematic reviews were conducted to synthesize the information which has been emerging. Therefore the aim of this work was to comprehensively review most of the studies published on this topic in China, including literature concerning field measurements, laboratory studies and the impacts of BB indoors and outdoors in China. In addition, this review provides insights into the role of wildfire and anthropogenic BB on air quality and health globally. Further, we attempted to provide a basis for formulation of policies and regulations by policy makers in China.
Open field biomass burning causes severe air pollution, public health risk and potential climate impact. a) Photo taken in Changzhou rural area on June 10, 2015; b) Photo taken in Hebei rural area on October 23, 2013; c) A traditional indoor burner in rural area in China; d) Tar ball emitted from biomass burning. Display omitted
•This review discusses wildfire and anthropogenic emission from biomass burning in China.•Field observations and laboratory studies on public health and climate impacts of biomass burning•Atmospheric process of biomass burning plumes and their transport•Proposed research priorities and insights about biomass burning in China
In modern society, printers are widely used in the office environment. This study investigated particle number and PM2.5 emissions from printers using the TSI SMPS, TSI CPC 3022, and 3025A TSI P-Trak ...and DustTrak. The monitoring of particle characteristics in a large open-plan office showed that particles generated by printers can significantly (p = 0.01) affect the submicrometer particle number concentration levels in the office. An investigation of the submicrometer particle emissions produced by each of the 62 printers used in the office building was also conducted and based on the particle concentrations in the immediate vicinity of the printers, after a short printing job, the printers were divided into four classes: non-emitters, and low, medium, and high emitters. It was found that approximately 60% of the investigated printers did not emit submicrometer particles and of the 40% that did emit particles, 27% were high particle emitters. Particle emission characteristics from three different laser printers were also studied in an experimental chamber, which showed that particle emission rates are printer-type specific and are affected by toner coverage and cartridge age. While a more comprehensive study is still required, to provide a better database of printer emission rates, as well as their chemical characteristics, the results from this study imply that submicrometer particle concentration levels in an office can be reduced by a proper choice of the printers.
This study aimed to quantify the efficiency of deep bag and electrostatic filters, and assess the influence of ventilation systems using these filters on indoor fine (<2.5 μm) and ultrafine particle ...concentrations in commercial office buildings. Measurements and modelling were conducted for different indoor and outdoor particle source scenarios at three office buildings in Brisbane, Australia. Overall, the in-situ efficiency, measured for particles in size ranges 6–3000 nm, of the deep bag filters ranged from 26.3 to 46.9% for the three buildings, while the in-situ efficiency of the electrostatic filter in one building was 60.2%. The highest PN and PM2.5 concentrations in one of the office buildings (up to 131% and 31% higher than the other two buildings, respectively) were due to the proximity of the building's HVAC air intakes to a nearby bus-only roadway, as well as its higher outdoor ventilation rate. The lowest PN and PM2.5 concentrations (up to 57% and 24% lower than the other two buildings, respectively) were measured in a building that utilised both outdoor and mixing air filters in its HVAC system. Indoor PN concentrations were strongly influenced by outdoor levels and were significantly higher during rush-hours (up to 41%) and nucleation events (up to 57%), compared to working-hours, for all three buildings. This is the first time that the influence of new particle formation on indoor particle concentrations has been identified and quantified. A dynamic model for indoor PN concentration, which performed adequately in this study also revealed that using mixing/outdoor air filters can significantly reduce indoor particle concentration in buildings where indoor air was strongly influenced by outdoor particle levels. This work provides a scientific basis for the selection and location of appropriate filters and outdoor air intakes, during the design of new, or upgrade of existing, building HVAC systems. The results also serve to provide a better understanding of indoor particle dynamics and behaviours under different ventilation and particle source scenarios, and highlight effective methods to reduce exposure to particles in commercial office buildings.
•Investigated the efficiency of different filters in commercial ventilation systems.•Mixing/outdoor air filters significantly reduced indoor particle concentration.•Results provide a better understanding of indoor particle dynamics and behaviour.•Reveals the impact of different ventilation and particle source scenarios.
The aim of this work was to investigate ultrafine particles (<0.1 μm) in primary school classrooms, in relation to the classroom activities. The investigations were conducted in three classrooms ...during two measuring campaigns, which together encompassed a period of 60 days. Initial investigations showed that under the normal operating conditions of the school there were many occasions in all three classrooms where indoor particle concentrations increased significantly compared to outdoor levels. By far the highest increases in the classroom resulted from art activities (painting, gluing, and drawing), at times reaching over 1.4 × 105 particle cm−3. The indoor particle concentrations exceeded outdoor concentrations by approximately 1 order of magnitude, with a count median diameter ranging from 20 to 50 nm. Significant increases also occurred during cleaning activities, when detergents were used. GC-MS analysis conducted on 4 samples randomly selected from about 30 different paints and glues, as well as the detergent used in the school, showed that d-limonene was one of the main organic compounds of the detergent, however, it was not detected in the samples of the paints and the glue. Controlled experiments showed that this monoterpene, emitted from the detergent, reacted with O3 (at outdoor ambient concentrations ranging from 0.06 to 0.08 ppm) and formed secondary organic aerosols. Further investigations to identify other liquids that may be potential sources of the precursors of secondary organic aerosols were outside the scope of this project, however, it is expected that the problem identified by this study could be more widely spread, since most primary schools use liquid materials for art classes, and all schools use detergents for cleaning. Further studies are therefore recommended to better understand this phenomenon and also to minimize exposure of school children to ultrafine particles from these indoor sources.
An increasing number of researchers have hypothesized that ozone may be involved in the particle formation processes that occur during printing, however no studies have investigated this further. In ...the current study, this hypothesis was tested in a chamber study by adding supplemental ozone to the chamber after a print job without measurable ozone emissions. Subsequent particle number concentration and size distribution measurements showed that new particles were formed minutes after the addition of ozone. The results demonstrated that ozone did react with printer-generated volatile organic compounds (VOCs) to form secondary organic aerosols (SOAs). The hypothesis was further confirmed by the observation of correlations among VOCs, ozone, and particles concentrations during a print job with measurable ozone emissions. The potential particle precursors were identified by a number of furnace tests, which suggested that squalene and styrene were the most likely SOA precursors with respect to ozone. Overall, this study significantly improved scientific understanding of the formation mechanisms of printer-generated particles, and highlighted the possible SOA formation potential of unsaturated nonterpene organic compounds by ozone-initiated reactions in the indoor environment.
It has now been recognized that some hardcopy devices emit ultrafine particles (d p < 100 nm) during their operation. As a consequence, the time-dependent characterization of particle release from ...laser printers is of high interest in order to evaluate the exposure of office workers to such emissions. The emission profiles of different printers can be compared in test chambers using a standardized test protocol and measuring devices with high time resolution. The extraction of meaningful and comparable data from the obtained data set is a complex procedure due to the different emission behavior patterns of the printers. The calculation of the unit specific emission rate (SERu) is of limited use because the emission profiles during the printing process ranged between short-term bursts and constant particle release. Therefore, other parameters such as the particle loss-rate coefficient, β, which provides information about the testing conditions, and the area below the time vs concentration curve, F, which characterizes the particle release, allow for a comparison of the different printer tests. Variations in the emission behavior could not be associated with specific manufacturers or product lines. In addition, when performing several print jobs on the same device, with only short pauses between jobs, the emission rate was reduced in some cases. This further complicates the ability to determine the influence of printer construction and consumables, such as toner and paper, on the concentration of particles emitted.
Vacuuming can be a source of indoor exposure to biological and nonbiological aerosols, although there are few data that describe the magnitude of emissions from the vacuum cleaner itself. We ...therefore sought to quantify emission rates of particles and bacteria from a large group of vacuum cleaners and investigate their potential determinants, including temperature, dust bags, exhaust filters, price, and age. Emissions of particles between 0.009 and 20 μm and bacteria were measured from 21 vacuums. Ultrafine (<100 nm) particle emission rates ranged from 4.0 × 106 to 1.1 × 1011 particles min–1. Emission of 0.54–20 μm particles ranged from 4.0 × 104 to 1.2 × 109 particles min–1. PM2.5 emissions were between 2.4 × 10–1 and 5.4 × 103 μg min–1. Bacteria emissions ranged from 0 to 7.4 × 105 bacteria min–1 and were poorly correlated with dust bag bacteria content and particle emissions. Large variability in emission of all parameters was observed across the 21 vacuums, which was largely not attributable to the range of determinant factors we assessed. Vacuum cleaner emissions contribute to indoor exposure to nonbiological and biological aerosols when vacuuming, and this may vary markedly depending on the vacuum used.
While recent research has provided valuable information as to the composition of laser printer particles, their formation mechanisms, and explained why some printers are emitters while others are low ...emitters, questions relating to the potential exposure of office workers remained unanswered. In particular, (i) what impact does the operation of laser printers have on the background particle number concentration (PNC) of an office environment over the duration of a typical working day? (ii) What is the airborne particle exposure to office workers in the vicinity of laser printers? (iii) What influence does the office ventilation have upon the transport and concentration of particles? (iv) Is there a need to control the generation of, and/or transport of particles arising from the operation of laser printers within an office environment? (v) What instrumentation and methodology is relevant for characterizing such particles within an office location? We present experimental evidence on printer temporal and spatial PNC during the operation of 107 laser printers within open plan offices of five buildings. The 8 h time-weighted average printer particle exposure is significantly less than the 8 h time-weighted local background particle exposure, but that peak printer particle exposure can be greater than 2 orders of magnitude higher than local background particle exposure. The particle size range is predominantly ultrafine (<100 nm diameter). In addition we have established that office workers are constantly exposed to nonprinter derived particle concentrations, with up to an order of magnitude difference in such exposure among offices, and propose that such exposure be controlled along with exposure to printer derived particles. We also propose, for the first time, that peak particle reference values be calculated for each office area analogous to the criteria used in Australia and elsewhere for evaluating exposure excursion above occupational hazardous chemical exposure standards. A universal peak particle reference value of 2.0 × 104 particles cm–3 has been proposed.
While current research has demonstrated that the operation of some laser printers results in emission of high concentrations of ultrafine particles, fundamental gaps in knowledge in relation to the ...emissions still remain. In particular, there have been no answers provided to questions such as the following: (1) What is the composition of the particles? (2) What are their formation mechanisms? (3) Why are some printers high emitters, while others are low? Considering the widespread use of printers and human exposure to these particles, understanding the process of particle formation is of critical importance. This study, using state-of-the-art instrumental methods, has addressed these three points. We present experimental evidence that indicates that intense bursts of particles are associated with temperature fluctuations and suggest that the difference between high and low emitters lies in the speed and sophistication of the temperature control. We have also shown, for the first time, that the particles are volatile and are of secondary nature, being formed in the air from VOC originating from both the paper and hot toner. Some of the toner is initially deposited on the fuser roller, after which the organic compounds evaporate and then form particles, through one of two main reaction pathways: homogeneous nucleation or secondary particle formation involving ozone.
Background, Aim and Scope The impact of air pollution on school children's health is currently one of the key foci of international and national agencies. Of particular concern are ultrafine ...particles which are emitted in large quantities, contain large concentrations of toxins and are deposited deeply in the respiratory tract. Materials and methods In this study, an intensive sampling campaign of indoor and outdoor airborne particulate matter was carried out in a primary school in February 2006 to investigate indoor and outdoor particle number (PN) and mass concentrations (PM₂.₅), and particle size distribution, and to evaluate the influence of outdoor air pollution on the indoor air. Results For outdoor PN and PM₂.₅, early morning and late afternoon peaks were observed on weekdays, which are consistent with traffic rush hours, indicating the predominant effect of vehicular emissions. However, the temporal variations of outdoor PM₂.₅ and PN concentrations occasionally showed extremely high peaks, mainly due to human activities such as cigarette smoking and the operation of mower near the sampling site. The indoor PM₂.₅ level was mainly affected by the outdoor PM₂.₅ (r = 0.68, p < 0.01), whereas the indoor PN concentration had some association with outdoor PN values (r = 0.66, p < 0.01) even though the indoor PN concentration was occasionally influenced by indoor sources, such as cooking, cleaning and floor polishing activities. Correlation analysis indicated that the outdoor PM₂.₅ was inversely correlated with the indoor to outdoor PM₂.₅ ratio (I/O ratio; r = −0.49, p < 0.01), while the indoor PN had a weak correlation with the I/O ratio for PN (r = 0.34, p < 0.01). Discussion and conclusions The results showed that occupancy did not cause any major changes to the modal structure of particle number and size distribution, even though the I/O ratio was different for different size classes. The I/O curves had a maximum value for particles with diameters of 100-400 nm under both occupied and unoccupied scenarios, whereas no significant difference in I/O ratio for PM₂.₅ was observed between occupied and unoccupied conditions. Inspection of the size-resolved I/O ratios in the preschool centre and the classroom suggested that the I/O ratio in the preschool centre was the highest for accumulation mode particles at 600 nm after school hours, whereas the average I/O ratios of both nucleation mode and accumulation mode particles in the classroom were much lower than those of Aitken mode particles. Recommendations and perspectives The findings obtained in this study are useful for epidemiological studies to estimate the total personal exposure of children, and to develop appropriate control strategies for minimising the adverse health effects on school children.
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