Characteristics Of Fine Particulate Matter Research Articles

Ratios of organic mass to organic carbon in fine particulate matter at urban sites in China and Korea during winter and summer.

This study evaluates the composition and seasonal characteristics of fine particulate matter (PM2.5) during winter and summer through simultaneous measurements conducted at the Gwangju Institute of Science and Technology in South Korea and the Changping campus of Peking University in China. PM2.5 samples were concurrently collected at both sites, and chemical analyses were conducted to quantify various components, including carbonaceous materials, ionic species, and metals. Although the average PM2.5 concentrations were comparable between the two sites, there were distinct differences in the concentrations of major components. Organic indicator compounds were analyzed to discern the contributions of primary and secondary pollution sources. Changping displayed a mix of primary and secondary pollution, characterized by higher concentrations of primary organic carbon (POC) such as polycyclic aromatic hydrocarbons and hopanes, compared to Gwangju. In contrast, Gwangju demonstrated a higher prevalence of secondary organic carbon (SOC), particularly water-soluble organic carbon not related to biomass burning (WSOCnbb) and various polar organic compounds. The organic mass to organic carbon (OM/OC) ratios estimated using the mass balance method revealed significant differences, with Gwangju showing a higher ratio of 2.3 compared to 1.9 at Changping, indicating a greater influence of secondary pollutants at Gwangju. Additionally, both Changping and Gwangju exhibited higher OM/OC ratios in summer (Changping: 2.0, Gwangju: 2.5) compared to winter (Changping: 1.8, Gwangju: 2.2), indicating seasonal differences in organic mass contributions to PM2.5. These findings underscore the importance of accounting for spatial and seasonal variations in air pollution studies and suggest that updating commonly used OM/OC ratios could enhance the reliability of research outcomes.

Investigation of nonlinear dynamics and stochastic characteristics of fine particulate matter in urban environments

Investigation of nonlinear dynamics and stochastic characteristics of fine particulate matter in urban environments

Insights into atmospheric trace gases, aerosols, and transport processes at a high-altitude station (2623 m a.s.l.) in Northeast Asia

As part of the efforts to understand long-range air pollution transport in Northeast Asia, a comprehensive field measurement campaign was conducted at the top of Changbai Mountain (2623 m a.s.l.) from 25th July to 21st August in 2021. The ambient concentrations of trace gases and chemical characteristics of fine particulate matter (PM2.5) were comparable to those at background or free tropospheric locations in China, but exceeded levels at corresponding sites in Europe and the United States. Well-defined diurnal variations were evident in most air pollutants, including carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen oxide (NOx), reflecting the influence of boundary layer development and local anthropogenic activities. Ozone (O3) exhibited a unique diurnal distribution, with lower concentrations during the daytime and higher levels at nighttime, indicating a pronounced impact of downward transport of O3-rich air from the upper troposphere during the nighttime. During the campaign, organic carbon (OC) constituted the predominant component of PM2.5, comprising 43% of the total, while sulfate (SO42−) was the most abundant secondary inorganic component in PM2.5, accounting for 26%. Combining the analysis of air mass backward trajectories, we found that Changbai Mountain is primarily influenced by air masses originating from North Korea and the Sea of Japan, constituting 62% of the total, and local vegetation biological emissions and anthropogenic emissions in North Korea notably affect the observation site. Conversely, the secondary aerosol components were most abundant in marine air mass originating from the marginal seas of China and the strait between the Korean peninsula and southern Japan. Utilizing the Lagrangian photochemical trajectory model (LPTM), a significant increase in particulate SO42− concentrations was observed when air mass passed through the marginal seas of China, primarily due to SO2 oxidation reaction. This study contributes to an improved understanding of the atmospheric chemistry in the high-altitude regions of Northeast Asia and underscores the substantial role of secondary inorganic aerosol formation during the transport of marine air masses.

Variations in optical properties of water- and methanol-soluble organic carbon in PM2.5 in Tianjin and Handan over the Wintertime of 2018–2020

The impact of the Three-year Action Plan for winning the “blue sky defense battle” on the pollution levels and chemical characteristics of fine particulate matter has been intensively studied over the past few years. However, the effect of air pollution control on light absorption of brown carbon remains unclear. In this study, the light absorption and fluorescence properties of water- and methanol-soluble organic carbon (WSOC and MSOC) in PM2.5 in Tianjin and Handan in North China Plain were measured and evaluated for three consecutive winters during the Three-year Blue-Sky Action (2018–2020). Overall, the WSOC and MSOC mass concentrations and light absorption coefficients of WSOC and MSOC at 365 nm generally decreased from 2018 to 2020, indicating that the emission of solvent-soluble organic carbon has been effectively controlled with the implementation of pollution abatement measures, such as the enforcement of clean energy policies. The light absorption coefficient and mass absorption efficiency at 365 nm of MSOC were 1.41–3.82 and 1.13–1.72 times higher than that of WSOC, respectively. Fluorescent spectra coupled with parallel factor analysis indicated that less‑/highly‑oxygenated humic-like (LO-/HO-HULIS) and non-N aromatic species (non-Nas) were the major fluorophores in both WSOC and MSOC in the two cities, with LO-HULIS and HO-HULIS as two major contributors to WSOC light absorption, while both HULIS and non-Nas fluorophores had a strong correlation with MSOC light absorption. Correlation analysis with source tracers and fluorescent indices indicated that the influence of combustion emissions remains significant, and secondary formation made a non-negligible contribution to the light absorption and fluorescent components of WSOC and MSOC in both cities. This work will contribute to a better understanding of the evolution of concentration levels and optical properties of WSOC and MSOC during pollution abatement and will inform the subsequent development of measures to achieve a win-win situation for both air quality and climate change.

Characteristics of fine particulate matter in Linyi during the 24th Olympic winter Games: An insight into the components, sources, transport pathways, and source distribution

To maintain air quality and mitigate pollution during the 24th Olympic Winter Games, strict control measures were implemented in Beijing and surrounding areas, including Linyi. Fine particulate matter (PM2.5) sampling was conducted in the urban area of Linyi between November 10th, 2021, and February 20th, 2022. This sampling period was divided into a no-control period (NCP) and a control period (CP). The PM2.5 concentration decreased by 25.0% during the CP, whereas the atmospheric oxidation increased. This led to the formation of secondary components of PM2.5. Although the conversion rate of the precursors into secondary components was increased during the CP, the nitrate (NO3−) and ammonium (NH4+) concentrations were reduced due to emission reduction. Elemental carbon (EC) and primary organic carbon concentrations were also decreased, whereas the organic carbon (OC)/EC ratio and proportion of secondary organic carbon in PM2.5 increased. Total detected inorganic element concentrations decreased by 23.6% during the CP. The results of source apportionment revealed that secondary sources were the leading PM2.5 contributors during both periods. Vehicle pollution prevention and control should be strengthened as no restrictions on private-car travel during the CP. Controlling combustion and industrial sources had a significant impact on air quality during the CP. Biomass burning and industrial emissions declined from 20.7% to 16.1% (NCP) to 2.0% and 9.1% (CP), respectively. Backward trajectories revealed that air masses largely originated from local regions during both periods, with the highest PM2.5 concentrations found in air masses from the north (NCP) and east (CP) of Linyi. Potential source regions were also identified. The location of these regions showed that local and regional collaborative control of PM2.5 is urgently needed, particularly in northern and southern Linyi (NCP) and eastern Linyi (CP).

Numerical study on filtration characteristics of high-temperature particulate matter in a three-dimensional randomly arranged multi-granularity particle bed filter

The transformation of internal filter granules into a heterogeneous size distribution through abrasion alters filtration properties. This research constructs an abraded multi-granularity particle bed filter via unidirectional coupling of the discrete element method and computational fluid dynamics. The study examined the filtration characteristics of fine particulate matter at high temperatures. The findings indicate that the abraded multi-granularity beds were higher than the uniform size granular beds in both pressure drop and filtration efficiency. The abraded multi-granularity bed enhances filtration efficiency with a proportionally minor increase in pressure drop relative to the uniform size granular bed. In comparison to a stratified bed structure, the mixed configuration of the multi-granularity bed yields greater filtration efficiencies with less escalation in pressure drop. To maintain filtration efficiency beyond 90%, higher temperatures necessitate an augmented inlet flow rate, requiring an increase by a factor of 2.23 at 1000 K relative to 300 K.

A baseline characterization of fine particulate matter (PM2.5) concentration and releases in Nova Scotia, Canada

Three industrial facilities (a kraft pulp mill, a tire manufacturing, and a coal-fired power generation plant), have operated in Pictou County, Nova Scotia, Canada for more than 50 years. The local population, including an Indigenous community, has raised concerns for several decades about the environmental and human health impacts of local air and effluent pollution. Numerous studies have reported negative air, water, sediment, and ecological and human health impacts in the region. However, previous studies mainly focused on wastewater effluent discharge from the kraft pulp mill, with only a few studies focused on air pollution. These limited air pollution studies pointed out the pulp mill as the primarily responsible for local emissions of fine particulate matter (PM2.5), but with high levels of uncertainty. This study analyzed hourly and daily PM2.5 concentrations measured at an air quality monitoring station in Pictou (part of the National Air Pollution Surveillance [NAPS] network) between 2004 and 2021. For events of high PM2.5 concentrations (which occurred predominantly in April and May in 2014 and 2015), air masses were tracked using the HYSPLIT model to evaluate if long-range transboundary pollution could have contributed to PM2.5 concentration. Results suggest that the pulp mill was likely the primary source of high PM2.5 concentrations recorded at the Pictou NAPS station. Measured PM2.5 concentrations only met the desirable air quality management concentrations after the pulp mill installed a recovery boiler electrostatic precipitator in October 2015 to reduce PM2.5 emissions.

Seasonal and Spatial Variations of the Oxidative Properties of Ambient PM2.5 in the Po Valley, Italy, before and during COVID-19 Lockdown Restrictions.

This study describes the chemical and toxicological characteristics of fine particulate matter (PM2.5) in the Po Valley, one of the largest and most polluted areas in Europe. The investigated samples were collected in the metropolitan area of Milan during the epidemic lockdown and their toxicity was evaluated by the oxidative potential (OP), measured using ascorbic acid (OPAA) and dithiothreitol (OPDTT) acellular assays. The study was also extended to PM2.5 samples collected at different sites in the Po Valley in 2019, to represent the baseline conditions in the area. Univariate correlations were applied to the whole dataset to link the OP responses with the concentrations of the major chemical markers of vehicular and biomass burning emissions. Of the two assays, OPAA was found mainly sensitive towards transition metals released from vehicular traffic, while OPDTT towards the PM carbonaceous components. The impact of the controlling lockdown restrictions on PM2.5 oxidative properties was estimated by comparing the OP values in corresponding time spans in 2020 and 2019. We found that during the full lockdown the OPAA values decreased to 80-86% with respect to the OP data in other urban sites in the area, while the OPDTT values remained nearly constant.

Composition of inorganic elements in fine particulate matter emitted during surface fire in relation to moisture content of forest floor combustibles

The moisture content of combustible material on the forest floor is constantly changing due to environmental factors, which have a direct impact on the composition and emission intensity of particulate matter released during fire. In this study, an indoor biomass combustion analysis device was used to analyze the emission characteristics of fine particulate matter (PM2.5) from combustion of herbaceous combustible materials with different moisture contents (0%, 15%, and 30%). The composition of inorganic elements in PM2.5 (Zn, K, Mg, Ca, and other 13 measurable elements) were determined by inductively coupled plasma-mass spectrometer (ICP-MS). The results showed that the PM2.5 emission factor increased significantly with the increase of moisture content of combustible materials in the range of 11.63 ± 0.55 for dry samples to 36.71 ± 1.21 g/kg for samples with 30% moisture content. The main elemental components of PM2.5 were K, Zn, Ca, Mg, and Na and K, Ca, Mg, and Na emission factors increased with the increase of moisture content of combustibles. The proportion of macronutrients in PM2.5 released by combustion of each herb increased as the moisture content increased, but the proportion of trace elements gradually decreased. There was a good correlation between elemental composition of PM2.5 and that of herbaceous combustibles. The results provide evidence that the moisture content of combustible materials has a significant effect on the emission of inorganic elements in particulate matter, and hence cautions should be exercised during fuel reduction treatments, such as early prescribed fire.

Characterization of fine particulate matter from indoor cooking with solid biomass fuels.

Household burning of solid biomass fuels emits pollution particles that are a huge health risk factor, especially in low-income countries (LICs) such as those in Sub-Saharan Africa. In epidemiological studies, indoor exposure is often more challenging to assess than outdoor exposure. Laboratory studies of solid biomass fuels, performed under real-life conditions, are an important path toward improved exposure assessments. Using on- and offline measurement techniques, particulate matter (PM) from the most commonly used solid biomass fuels (charcoal, wood, dung, and crops residue) was characterized in laboratory settings using a way of burning the fuels and an air exchange rate that is representative of real-world settings in low-income countries. All the fuels generated emissions that resulted in concentrations which by far exceed both the annual and the 24-hour-average WHO guidelines for healthy air. Fuels with lower energy density, such as dung, emitted orders of magnitude more than, for example, charcoal. The vast majority of the emitted particles were smaller than 300 nm, indicating high deposition in the alveoli tract. The chemical composition of the indoor pollution changes over time, with organic particle emissions often peaking early in the stove operation. The chemical composition of the emitted PM is different for different biomass fuels, which is important to consider both in toxicological studies and in source apportionment efforts. For example, dung and wood yield higher organic aerosol emissions, and for dung, nitrogen content in the organic PM fraction is higher than for the other fuels. We show that aerosol mass spectrometry can be used to differentiate stove-related emissions from fuel, accelerant, and incense. We argue that further emission studies, targeting, for example, vehicles relevant for LICs and trash burning, coupled with field observations of chemical composition, would advance our understanding of air pollution in LIC. We believe this to be a necessary step for improved air quality policy.

Chemical components of PM2.5 in different seasons in Harbin, China

The seasonal characteristics of fine particulate matter (PM2.5) were investigated from October 2020 to April 2021 (spreading fall, winter and spring) in Harbin, a city located in northeast China. The mass concentrations of PM2.5 in winter were significantly higher than those in fall and spring. Moreover, our results indicated that various aerosol species had obvious seasonality. The proportions of secondary components were higher in winter than other two seasons. In contrast, the ratios of nitrate to sulfate (NO3−/SO42−) showed lower levels in winter, which was because both the ratios of nitrogen dioxide to sulfur dioxide (NO2/SO2) and the ratios of nitrogen oxidation ratio to sulfur oxidation ratio (NOR/SOR) exhibited lower values in winter than in fall and spring. With PM2.5 increased, the NO3−/SO42− ratios showed increasing trends in all three seasons, which was mainly attributed to the increase of NOR/SOR ratios in fall and spring, and the increase of both NO2/SO2 and NOR/SOR ratios in winter. This result highlighted that nitrate was more important than sulfate as a driver for the growth of PM2.5 during the period of heavy air pollution. Additionally, the sources of organic aerosol (OA) in different seasons were also distinctly different. Overall, the sum of biomass burning OA (BBOA) and secondary OA (SOA) contributed >70% of OA in three seasons. The fractional contributions of BBOA to total OA, notably, exhibited higher levels in fall and spring, because of intensive open agricultural fires. The SOA fractions in OA were larger in winter, likely due to higher relative humidity which facilitated the secondary formation. A large increase in the proportions of BBOA was observed during polluted days in fall and spring compared to clean days. In comparison, during heavily-polluted periods, secondary formation made a dominant contribution to organic matter in winter.

Chemical characterization of PM2.5 in heavy polluted industrial zones in the Guanzhong Plain, northwest China: Determination of fingerprint source profiles

Industrial emission has been proved to be an important source of atmospheric PM2.5, which causes serious air pollution and health impacts. The air quality of the industrial zones, which are the intermediate stationary areas between the direct emissions and diffusion to the atmosphere, is always overlooked. In this study, the PM2.5 filter samples were collected in the six representative types of industrial zones in four cities of the Guanzhong Plain in 2020. The chemical characteristics of fine particulate matter (PM2.5) in the zones were investigated. The mass concentrations of 13 elements and 39 polycyclic aromatic hydrocarbons (PAHs) in PM2.5 were quantified. Cement and concrete (CC) and brick production (BP) exhibited a similar chemical composition profile characterized by high proportions of calcium (Ca), aluminum (Al), benzo[k]fluoranthene (BkF), 1-nitronaphthalene (1N-NAP), and 3-nitrofluoranthene (3N-FLA). Glassware and ceramics (GC) showed a distinguishable profile with a relatively low ratio of copper/cadmium (Cu/Cd) and lead (Pb)/Cd. The profile for metal forging (MF) was abundant in vanadium (V), Pb, indeno[1,2,3-cd]pyrene (IcdP) and also recognized by particular diagnostic ratios of nitrated-PAHs (n-PAHs). The highest proportions of several metals such as chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), zinc (Zn), Cd, and fluoranthene (FLA) were found in the thermoelectric industry (TI) due to a large amount of coal consumption in the manufacture processing. Chemical production (CP) was the only industrial type using natural gas as the main fuel in this study, which shows the distinguishing feature of relatively high proportions of low molecular weight parent-PAHs (p-PAHs) and 2-ring oxygenated-PAHs (o-PAHs). This study not only attains the detailed chemical fingerprints, but also the potential tracers and ratios, which are of great significance for refining source apportionment and relieving PM2.5 pollution contributed by the industrial sources.

Spatial characteristics of fine particulate matter in subway stations: Source apportionment and health risks

Air in subway stations is typically more polluted than ambient air, and particulate matter concentrations and compositions can vary greatly by location, even within a subway station. However, it is not known how the sources of particulate matter vary between different areas within subway stations, and source-specific health risks in subway stations are unclear. We analyzed the spatial characteristics of particulate matter by source and calculated source-specific health risks on subway platforms and concourses and in station offices by integrating source apportionment with health risk assessments. A total of 182 samples were collected in three areas in six subway stations in Nanjing, China. Enrichment factors and the positive matrix factorization receptor model were used to identify major sources. The carcinogenic and non-carcinogenic health risks to subway workers and passengers were evaluated to determine control priorities. Seven sources of particulate matter were identified in each area, with a total of four subway sources and six outdoor sources over all the areas. The source contributions to total element mass differed significantly from the source contributions to human health risks. Overall, subway sources contributed 48% of total element mass in the station office and 75% and 60% on the concourse and platform, respectively. Subway-derived sources accounted for 54%, 81%, and 71% of non-carcinogenic health risks on station platforms, concourses, and office areas, respectively. The corresponding values for carcinogenic risks were 51%, 86%, and 86%. Among the elements, cobalt had the largest contributions to carcinogenic and non-carcinogenic risks, followed by manganese for non-carcinogenic risks and hexavalent chromium for carcinogenic risks. Reducing emissions from subway sources could effectively protect the health of subway workers and passengers.

Identification for discharged characteristics of fine particulate matter from coke chemical industry in northern China

Identification for discharged characteristics of fine particulate matter from coke chemical industry in northern China

Characteristics of fine particulate matter (PM2.5) at Jinsha Site Museum, Chengdu, China.

Air pollution is a serious threat to ancient sites and cultural relicts. In this study, we collected indoor and outdoor PM2.5 samples and individual particles at the Exhibition Hall of Jinsha Site Museum in June 2020, and then the chemical components, sources, morphology, and mixing state of the fine particulate matter were analyzed. Our results show that the indoor and outdoor PM2.5 concentrations at the Exhibition Hall were 33.3±6.6 and 39.4±11.4 μg m−3, respectively. Although the indoor and outdoor concentrations of OC and EC were close, the proportion of secondary organic carbon in OC outdoor (33%) was higher than that indoor (27%). The PM2.5 was alkaline both indoors and outdoors, and the outdoor alkalinity was stronger than the indoor alkalinity. SNA (SO42−, NO3−, and NH4+) was the dominant component in the water-soluble inorganic ions; Na+, Mg2+, and Ca2+ were well correlated (R2> 0.9), and Cl− and K+ were also highly correlated (R2> 0.8). Enrichment factor analysis showed that Cu (indoor) and Cd were the main anthropogenic elements and that Cd was heavily enriched. Principal components analysis showed that the main sources of PM2.5 at Jinsha Site Museum were motor vehicles, dust, secondary sources, and combustion sources. The individual particles were classified as organic matter, S-rich, soot, mineral, and fly ash/metal particles, and most of these particles were internally mixed with each other. At last, we proposed pollution control measures to improve the air quality of museums and the preservation of cultural relicts.

Distribution and transport characteristics of fine particulate matter in beijing with mobile lidar measurements from 2015 to 2018

Accurately quantifying the concentration and transport flux of atmospheric fine particulate matter (PM2.5) is vital when attempting to thoroughly identify the pollution formation mechanism. In this study, the mobile lidar measurements in Beijing on heavily polluted days in December from 2015 to 2018 are presented. The lidar was mounted on a vehicle, which could perform measurements along designated routes. On the basis of mobile lidar measurements along closed circuits of the 6th Ring Road around Beijing, the spatial distribution and transport flux of PM2.5 in Beijing were determined with information of wind field. In the spatial distribution, both the concentration and transport of PM2.5 were revealed to be more significant in the southern section of Beijing. The regional transport layer at heights < 1.3 km plays an important role in pollution formation. The maximum transport flux reached 1600 μg/(m2*sec) on 11 December 2016. With the aerosol boundary layer height determined from the image edge detection (IED) method, the inter-annual variations of the aerosol boundary layer height (ABLH) were also analysed. The ABLH decreased from 0.73 to 0.46 km during the same heavy pollution period from 2015 to 2018. Increasingly adverse aerosol boundary layer (ABL) meteorological factors, including lower ABLH, light winds, temperature inversions, and accumulated moisture, have become necessary for pollution formation in Beijing.

Real-time quantification and source apportionment of fine particulate matter including organics and elements in Delhi during summertime

Delhi is one of the most polluted cities globally, with frequent severe air pollution episodes and haze events occurring in recent years, thereby compelling us to understand the sources to develop effective mitigation plans. Complete chemical characterization of fine particulate matter (PM2.5) components (non-refractory, refractory and elements) with high time resolution has been done during the summer season (June–July 2019). The total PM equivalent (PM2.5(eq)) was 28.7 ± 13.2 μg m−3 of which elements dominated the PM2.5(eq) with 34% contribution followed by organics (28%), black carbon (BC) (17%), SO42− (10%), Cl− (5%) NH4+ (3.5%) and NO3− (2.5%). The contributions from organic aerosols (OA) and SO42− were observed to be more than Cl− and NO3−. The total elemental mass concentration (PMEl) was mostly contributed (~96%) by Si, S, Cl, Ca, K, Fe and Al with Si and S alone contributing around 50% of PMEl. Crustal elements (Al, Fe, Ca and Si) were highly enhanced in summer than elements emitted from anthropogenic emissions (Cl, S, K, Pb and Zn). Source apportionment (SA) of PM was performed using positive matrix factorization (PMF) together with ME-2 (multilinear engine) for OA and elements, separately. PMF on both datasets helped resolve sources such as combustion, industrial, dust-related, incineration and traffic. OA PMF identified three factors related to primary emissions: hydrocarbon-like OA (HOA, 12.3%), solid fuel combustion (SFC, 16.2%) and cooking OA (COA, 7.3%) and two oxygenated OA (OOA): semi-volatile OOA (SVOOA, 15.2%) and low-volatile OOA (LVOOA, 49.1%). The elemental PMF resolved 8 factors: dust (52.5%), S-rich (16.2%), Cl-rich (10.7%), 2 SFC factors (10.5%), non-exhaust (7.2%), Cu-rich (1.5%) and industrial (1.4%). The contribution of BC to total PM mass is shown to increase in the summer compared to previous studies reported for the winter season. The secondary oxidized sources dominated both the OA and elements SA during the summer with 64.3% and 27% (dust not considered) contribution, respectively. The domination of secondary sources implies that it is crucial to control the secondary aerosols' precursors in Delhi for developing pollution control strategies. The ME-2 resolved factors, coupled with concentration weighted trajectory (CWT) showed the probable major elemental source regions of local origin (Delhi- National Capital Region (Delhi-NCR)) as well as regional (from Punjab, Haryana, Uttar Pradesh and Pakistan). The local sources included Cu-rich (Haryana) and SFC-II (Delhi and Uttar Pradesh), while the regional sources were dust (south-west (SW)), industrial, Cl-rich (north-west (NW)), SFC-I (east and south-east (SE)) and S-rich (SE).

Variation characteristics of fine particulate matter and its components in diesel vehicle emission plumes

A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air. Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near the exhaust nozzle. The variation characteristics of fine particle matter (PM2.5) and its components in diesel vehicle exhaust plumes were analyzed. The PM2.5 emissions gradually increased with increasing distance from the nozzle in the plume. Elemental carbon emissions remained basically unchanged, organic carbon and total carbon (TC) increased with increasing distance. The concentrations of SO42−, NO3− and NH4+ (SNA) directly emitted by the vehicles were very low but increased rapidly in the exhaust plume. The selective catalytic reduction (SCR) reduced 42.7% TC, 40% NO3− emissions, but increased 104% SO42− and 36% NH4+ emissions, respectively. In summary, the SCR reduced 29% primary PM2.5 emissions for the tested diesel vehicles. The NH4NO3 particle formation maybe more important in the plume, and there maybe other forms of formation of NH4+ (eg. NH4Cl). The generation of secondary organic carbon (SOC) plays a leading role in the generation of secondary PM2.5. The SCR enhanced the formation of SOC and SNA in the plume, but comprehensive analysis shows that the SCR more enhanced the SNA formation in the plume, which is mainly new particles formation process. The inconsistency between secondary organic aerosol (SOA) and primary organic aerosol definitions is one of the important reasons for the difference between SOA simulation and observation.

Characterization of fine particulate matter generated in a large woody biomass-firing circulating fluid bed boiler

The formation and emission of ash particles in biomass combustion is one of the most intractable challenges in the biomass-firing utility boilers. In present study, field measurements of PM10 at the inlets and outlets of the baghouse equipped on a 50 MW biomass-firing CFB boiler were carried out. The results showed that PM10 generated from the combustion of the biomass fuels in the CFB boiler exhibited a uni-modal size distribution. The sole modal peak (appeared at 5 μm) in the PSD curve was located in the size range >1 μm, while there was no visible peak in the size range <1 μm. The coarse PM mainly exhibited rough and angular surfaces with elements Ca, Si and Al as the principal constituents. The mass concentrations of PM1, PM2.5 and PM10 after the bagshouse were reduced to 0.95, 5.58 and 25.70 mg/Nm3 respectively, corresponding to the capture efficiencies of 97.80%, 98.52% and 98.64%. Moreover, the PM capture efficiency was observed to decrease with decreasing particle size in PM0.2. More Cl migrated into the fine PM when passing through the baghouse. Further comparisons revealed that the mass ratios of PM1 in PM10 in the flyash generated in the CFB boilers were <10%, which was much lower than that in the grate boilers firing biomass (40–80%), which is beneficial to PM removal in the dust removers and reduce the final PM emission during biomass combustion.

Gridded bias correction of modeled PM2.5 for exposure assessment, and estimation of background concentrations over a coastal valley region of northwestern British Columbia, Canada

ABSTRACT Chemical transport models (CTM) can have large biases and errors when simulating pollutant concentrations. To improve the characterization of fine particulate matter (PM2.5) over complex terrain for exposure assessments, three mathematical formulae that utilized the relationship between modeled and observed quantile concentrations at a monitor location were developed. These were then applied to 1 year of CMAQ model output of PM2.5 over the Terrace–Kitimat Valley of northwestern British Columbia, Canada. The final products enhanced the representation of ambient levels at existing monitoring stations when evaluated with conventional statistical measures. Better agreement of corrected outputs with observed compliance metrics was also found. On average, the absolute errors of amended outputs were 11% and 10% for the annual mean PM2.5 and 98th percentiles of daily concentrations, respectively, compared to 45% and 61%, respectively, in the original outputs. These improvements provided greater confidence to use the amended outputs to estimate concentrations at locations without monitors. The predominance of pristine conditions in the modeling domain was exploited to derive annual background PM2.5 concentrations over the valley, which was estimated to be 2.0–2.3 μg m−3. To our knowledge, this is the first study to calculate background PM2.5 concentrations over northern BC coastlands using bias-corrected outputs from an air quality model. Implications: Bias correction of CMAQ model output was necessary for assessing regulatory compliance for ambient PM2.5. The implications are notable. First, for low to moderate spatial heterogeneity in monitoring data, the use of regression equations that relates quantile mean concentrations of model outputs to those of observational data enhances the estimation of PM2.5 at unmonitored locations. Second, by providing spatial pollutant distribution ahead of planned industrial development in Terrace–Kitimat Valley (TKV), corrected model output offers a baseline for tracking progress in airshed management. Third, correction improved pollutant exposure classification, for which the risk was predominantly low. Finally, 2.0–2.3 μg m−3 should be considered as PM2.5 concentrations that are irreducible when setting voluntary targets for ambient levels in the area.