Winter Episode Research Articles

Six-year source apportionment of submicron organic aerosols from near-continuous highly time-resolved measurements at SIRTA (Paris area, France)

Abstract. Organic aerosol (OA) particles are recognized as key factors influencing air quality and climate change. However, highly time-resolved long-term characterizations of their composition and sources in ambient air are still very limited due to challenging continuous observations. Here, we present an analysis of long-term variability of submicron OA using the combination of an aerosol chemical speciation monitor (ACSM) and a multiwavelength Aethalometer from November 2011 to March 2018 at a peri-urban background site of the Paris region (France). Source apportionment of OA was achieved via partially constrained positive matrix factorization (PMF) using the multilinear engine (ME-2). Two primary OA (POA) and two oxygenated OA (OOA) factors were identified and quantified over the entire studied period. POA factors were designated as hydrocarbon-like OA (HOA) and biomass burning OA (BBOA). The latter factor presented a significant seasonality with higher concentrations in winter with significant monthly contributions to OA (18 %–33 %) due to enhanced residential wood burning emissions. HOA mainly originated from traffic emissions but was also influenced by biomass burning in cold periods. OOA factors were distinguished between their less- and more-oxidized fractions (LO-OOA and MO-OOA, respectively). These factors presented distinct seasonal patterns, associated with different atmospheric formation pathways. A pronounced increase in LO-OOA concentrations and contributions (50 %–66 %) was observed in summer, which may be mainly explained by secondary OA (SOA) formation processes involving biogenic gaseous precursors. Conversely, high concentrations and OA contributions (32 %–62 %) of MO-OOA during winter and spring seasons were partly associated with anthropogenic emissions and/or long-range transport from northeastern Europe. The contribution of the different OA factors as a function of OA mass loading highlighted the dominant roles of POA during pollution episodes in fall and winter and of SOA for highest springtime and summertime OA concentrations. Finally, long-term trend analyses indicated a decreasing feature (of about −175 ng m−3 yr−1) for MO-OOA, very limited or insignificant decreasing trends for primary anthropogenic carbonaceous aerosols (BBOA and HOA, along with the fossil-fuel and biomass-burning black carbon components) and no statistically significant trend for LO-OOA over the 6-year investigated period.

SUB-ALTITUDE THERMO HYGHROMETRIC COMPARISON IN URBAN AND RURAL AREA IN HIGH-ALTITUDE TROPICAL CLIMATE BY RPA/DRONE

It is known that different types of land use and occupation (urban, industrial, rural, forest) alter the balance of energy between the surface and the atmosphere. The comparison between surface and sub-altitude climatology data in urban and rural areas has still been few studied. In this way, the proposed study aims to analyze and compare the values of temperature and relative humidity of the air near the surface (1.5m high) and at different heights (50m and 190m of the surface) in urban and rural areas in Sao Carlos (SP), during nighttime in winter episodes, by means of termo-hygrometer coupled in a quadricopter (four propellers) Remotely-Piloted Aircraft (RPA/Drone). The flight in the urban area was carried out on 07/13/2018 and in the rural area on 07/26/2018 between 19:30 and 20:30. The results showed that in the urban area at night time the temperature and relative humidity of the air are higher near the surface in relation to the sub-altitude data. In the rural area at night time the air temperature is lower and the relative air humidity is higher to the surface compared to the sub-altitude data.

Can Data Assimilation of Surface PM2.5 and Satellite AOD Improve WRF-Chem Forecasting? A Case Study for Two Scenarios of Particulate Air Pollution Episodes in Poland

Based on the Weather Research and Forecasting model with Chemistry (WRF-Chem) model and Gridpoint Statistical Interpolation (GSI) assimilation tool, a forecasting system was used for two selected episodes (winter and summer) over Eastern Europe. During the winter episode, very high particular matter (PM2.5, diameter less than 2.5 µm) concentrations, related to low air temperatures and increased emission from residential heating, were measured at many stations in Poland. During the summer episode, elevated aerosol optical depth (AOD), likely related to the transport of pollution from biomass fires, was observed in Southern Poland. Our aim is to verify if there is a relevant positive impact of surface and satellite data assimilation (DA) on modeled PM2.5 concentrations, and to assess whether there are significant differences in the DA’s impact on concentrations between the two seasons. The results show a significant difference in the impact of surface and satellite DA on the model results between the summer and winter episode, which to a large degree is related to the availability of the satellite data. For example, the application of satellite DA raises the factor of two statistic from 0.18 to 0.78 for the summer episode, whereas this statistic remains unchanged (0.71) for the winter. The study suggests that severe winter air pollution episodes in Poland and Eastern Europe in general, often related to the dense cover of low clouds, will benefit from the assimilation of surface observations rather than satellite data, which can be very sparse in such meteorological situations. In contrast, the assimilation of satellite data can have a greater positive impact on the model results during summer than the assimilation of surface data for the same period.

Mode-Decomposed Equation Diagnosis for Atmospheric Blocking Development

AbstractThis paper proposes a new method to identify atmospheric blocking development without the time filtering used in previous studies. A mode-decomposed vorticity equation is formulated from the principal components (PCs) of 500-hPa geopotential height by applying a new idea; the orthonormality of PCs allows any variable to be decomposed into a projection corresponding to the PCs. To test this, sectorial blocking episodes in Northern Hemisphere winter were identified by Barriopedro’s method. A blocking index was defined for each longitudinal range as the linear combination of the 10 largest PCs by means of the composite for the blocking episodes. Blocking development was diagnosed, in terms of the low modes of PC1–PC10 and the high modes of PC11–PC50. The results suggest that the intensification of blocking over the North Pacific and Eurasia is associated with nonlinear interaction among high modes, whereas the intensification (decay) of North Atlantic blocks is related mainly to enhanced nonlinear interaction among low-frequency (high-frequency) eddies. This main result is insensitive to the choice of definition for blocks and the choice of the mode separation boundary.

Organic Aerosol Processing During Winter Severe Haze Episodes in Beijing

AbstractOrganic aerosol (OA) constituted a large fraction of aerosol particles during severe haze episodes in winter in northern China, yet our understanding of its physical and chemical processing was limited. Here we investigate the sources and processes of OA during four haze episodes in winter in 2016 using high‐resolution aerosol mass spectrometer. The PM2.5 reached 400 μg/m3 during the severest episode (Ep1) when Beijing issued a red alert and implemented strict emission controls. Our results showed that secondary OA (SOA) dominated OA during haze episodes on average accounting for 46–66% of OA and was comparable to secondary inorganic aerosol (SIA) with the SOA/SIA ratios being 0.51–0.72. Primary OA from fossil‐fuel combustion, biomass burning, and cooking presented very strong diurnal variations during haze episodes and contributed up to 60% in OA at night. Comparatively, the changes in semivolatile and low‐volatility SOA were relatively small except a substantial increase in aqueous phase‐related oxidized OA (aq‐OOA) during Ep1 with high relative humidity and aerosol water content. aq‐OOA fell well into a small region in the middle of the triangle plot of f44 versus f43 (fraction of m/z 44 and 43 in OA, respectively), which can be used as a diagnostic for the presence of aqueous phase processing of SOA. In addition, the increases of SO2+/SO3+ as a function of relative humidity, the triangle plot of versus , and high nitrogen‐to‐carbon ratio in aq‐OOA suggest the potential formation of sulfur‐ and nitrogen‐containing organic compounds through aqueous phase processing.

Concentration Characteristics of PM2.5 and the Causes of Heavy Air Pollution Events in Beijing During Autumn and Winter

To study the changing of characteristics and formation mechanisms of PM2.5 in Beijing during the last two years, particulate matter concentrations, weather conditions, and air-mass trajectories were analyzed during severe pollution episodes in fall and winter 2016-2017 using routine observations and the TrajStat model. Results showed that 13 heavy pollution events, each lasting at least two days, occurred in Beijing. Of these, approximately 61.5% occurred in winter, characterized by heavier pollution concentrations and longer durations than those occurring in autumn. A low-pressure gradient, high humidity, low surface wind speed, low boundary layer, and particular terrain (i. e., being surrounded by mountains on three sides) all contributed to the high occurrence frequency of severe pollution episodes in autumn and winter. During the pollution episodes, the average ratio of PM2.5 to PM10 reached 0.86. The air-masses during the accumulation stage were mainly transported from the northwest, west, southwest, and southeast of Beijing. The southwestern and southeastern transmission paths accounted for 21.6% of the total pollution load. In addition, the WRF-CAMx model was used to quantitatively analyze the contributions of local and external sources to the concentrations of PM2.5 in Beijing during 16-22 December 2016. Based on this analysis, PM2.5 contributions notably varied with different air-masses; in the case of southern air-masses, external sources dominated the PM2.5 concentrations in Beijing and local contributions decreased rapidly; in contrast, in the case of northwestern air-masses, the opposite pattern occurred. Overall, the contribution of local sources to PM2.5 concentrations in Beijing varied from 16.5% to 69.3% during the monitored pollution episodes.

Impact of planetary boundary layer structure on the formation and evolution of air-pollution episodes in Shenyang, Northeast China

The impact of the planetary boundary layer (PBL) structure on air pollution in Northeast China, where frequently experiences air pollution episodes in autumn and winter, is not well understood due to a lack of observations. In this study, four pollution episodes during autumn and winter of 2016 at Shenyang, a provincial capital city in Northeast China, were examined to investigate the linkage between the PBL structure and air pollution using meteorological sounding data and LiDAR-retrieved profiles of aerosol extinction coefficients. We also conducted a tracer simulation using the Weather Research and Forecasting model with Chemistry (WRF-Chem) to demonstrate the transport and vertical mixing of air pollutants in the PBL. The results indicated that a stable, moist and shallow surface layer (<400 m) formed and remained at night due to strong surface radiative cooling after a steep decline of temperature during the first air-pollution episode (EP1, from 12:00 Local Time (LT) on November 26 to 07:00 LT on November 27). Stable stratification and stagnant winds contributed to the increase of surface pollutant concentrations in EP1. Strong surface potential temperature inversion and enhanced local emissions during evening rush hour resulted in the formation of EP2 (13:00–23:00 LT on December 2). Observations and modelling results revealed that large amount of pollutants were transported by the southerly nocturnal low-level jets from the North China Plain to Shenyang after EP2. These pollutants were trapped in the residue layer at night and then mixed to the surface after sunrise due to convective turbulence, leading to the formation of EP3 (06:00–23:00 LT on December 3). EP4 (03:00–14:00 LT on December 4) occurred in the convergence zone ahead of an approaching trough. Low wind speed (<6 m s−1) and high relative humidity (>80%) in the PBL enhanced the deterioration of air quality near the surface.

Variations in submicron aerosol liquid water content and the contribution of chemical components during heavy aerosol pollution episodes in winter in Beijing.

The aerosol liquid water content (ALWC) of submicron particles (PM1) was calculated in this work by three methods based on the aerosol physical and chemical properties measurement campaigns in winter in Beijing, including (a) the PM1 volume difference between the ambient and dry states by applying the particle number size distribution and particle hygroscopicity measurement; (b) the thermodynamic equilibrium model (ISORROPIA II) based on the chemical composition; and (c) the κ-Köhler theory of chemical composition with a volume mixing scheme. The three methods agreed well with reasonable uncertainties. The ALWC showed an exponential trend depending on the relative humidity (RH), and an abundant ALWC was also favored by the high PM1 mass loading. The contribution of different chemical component to the ALWC was evaluated by the κ-Köhler method, which revealed that during the measurement, the inorganics and organics could contribute to ~80% and ~20%, respectively, under ambient RH conditions, with the largest contributor of ammonium nitrate. When the RH was above 85%, the mass concentration of ALWC was comparable to, or even larger than, that of the dry PM1.

Contrasting Aerosol Optical Characteristics and Source Regions During Summer and Winter Pollution Episodes in Nanjing, China

Two episodes with heavy air pollution in Nanjing, China, one in the summer and another one in the winter of 2017, were selected to study aerosol properties using sun photometer and ground-based measurements, together with source region analysis. The aerosol properties, the meteorological conditions, and the source regions during these two episodes were very different. The episodes were selected based on the air quality index (AQI), which reached a maximum value of 193 during the summer episode (26 May–3 June) and 304 during the winter episode (21–31 December). The particulate matter (PM) concentrations during the winter episode reached maximum values for PM2.5/10 of 254 g m−3 and 345 g m−3, much higher than those during the summer (73 and 185 g m−3). In contrast, the value of aerosol optical depth (AOD) at 500 nm was higher during the summer episode (2.52 0.19) than during that in the winter (1.38 0.18). A high AOD value does not necessarily correspond to a high PM concentration but is also affected by factors, such as wind, Planetary Boundary Layer Height (PBLH), and relative humidity. The mean value of the Ångström Exponent (AE) varied from 0.91–1.42, suggesting that the aerosol is a mixture of invaded dust and black carbon. The absorption was stronger during the summer than during the winter, with a minimum value of the single scattering albedo (SSA) at 440 nm of 0.86 on 28 May. Low values of asymmetry factor (ASY) (0.65 at 440 nm and 0.58 at 1020 nm) suggest a large number of anthropogenic aerosols, which are absorbing fine-mode particles. The Imaginary part of the Refractive Index (IRI) was higher during the summer than during the winter, indicating there was absorbing aerosol during the summer. These differences in aerosol properties during the summer and winter episodes are discussed in terms of meteorological conditions and transport. The extreme values of PM and AOD were reached during both episodes in conditions with stable atmospheric stratification and low surface wind speed, which are conducive for the accumulation of pollutants. Potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analysis show that fine mode absorbing aerosols dominate during the summer season, mainly due to emissions of local and near-by sources. In the winter, part of the air masses was arriving from arid/semi-arid regions (Shaanxi, Ningxia, Gansu, and Inner Mongolia provinces) covering long distances and transporting coarse particles to the study area, which increased the scattering characteristics of aerosols.

Nitrate dominates the chemical composition of PM2.5 during haze event in Beijing, China

Water-soluble inorganic ions (WSI), a major component of PM2.5, often increased rapidly during the haze event in Beijing. Sulfate (SO42−), Nitrate (NO3−), and Ammonium (NH4+) are three main components of WSI. Since year 2015, sulfate concentrations in PM2.5 has gradually decreased owing to the effective control of SO2 emissions. However, the contribution of nitrate to PM2.5 has significantly increased during haze events in Beijing at the same time. In this study, a highly time-resolved online analyzer (Monitor for Aerosols and Gases, MARGA) was employed to measure the WSI in PM2.5 in Beijing from 5 February to 15 November 2017. Three typical haze events during this sampling period were investigated. During heavy pollution episodes in winter, nitrate concentrations increased from 7.5 μg/m3 to 45.6 μg/m3 (45.0% of WSI), while sulfate increased from 4.2 μg/m3 to 20.1 μg/m3 (19.8% of WSI). This indicated that nitrate is more important than sulfate as a driver for the growth of PM2.5 during the period of heavy air pollution in winter. Nitrate also dominates the increase of WSI in the pollution episodes in autumn, with an average concentration of 52.5 μg/m3, and contributed up to 67% of WSI. The average concentration ratio of NH4+ to SO42− was higher in autumn (1.02) than that in summer (0.74) and close to that in winter (1.00). This is mainly because the emission control of coal combustion in Beijing and surrounding areas results in an NH3-rich and SO2-lean atmosphere, which promoted the formation of ammonium nitrate. Our study indicates that nitrate has become the most important component of WSI in PM2.5 and is driving the rapid growth of PM2.5 concentrations during heavy pollution episodes in Beijing. Therefore, more efforts shall be made to reduce the nitrogen oxide and ammonia emissions in Beijing and surrounding areas.

Pollution Characteristics and Sources of Fine Particles During a Heavy Haze Episode in Winter: A Case Study of Weinan City

Single Particle Aerosol Mass Spectrometry (SPAMS) is used to investigated a heavy haze process in Weinan,2017. Firstly, the fine particles (PM2.5) using ART-2a was analysed and clustered into 8 classes: organic carbon (OC), organics and elemental carbon combined particles (ECOC), elemental carbon (EC), heavy metal (HM), high molecular organic carbon (HOC), K-rich, levoglucosan (Lev) and dust. Secondly, positive matrix factorization (PMF) was used to identify the sources of PM2.5. Results from PMF showed that the main six sources of PM2.5 were coal-fired (38.48%), secondary (19.19%), biomass burning (15.04%), industry (9.28%), traffic (5.02%), and dust (5.00%). And it is obvious that the major cause of the atmospheric heavy haze is an unfavorable meteorological conditions such as high humidity and low wind speed, as well as coal-fired pollution and secondary pollution caused by heating and industrial production.

Characteristics and secondary formation of water-soluble organic acids in PM1, PM2.5 and PM10 in Beijing during haze episodes

Water-soluble organic acids are widely involved in various atmospheric physicochemical processes and appear as an important fraction of atmospheric aerosols. Nineteen water-soluble organic acids in 12-h PM1, PM2.5 and PM10 samples collected in urban Beijing during haze episodes in winter and spring of 2017 were identified to investigate their characteristics and secondary formation mechanism. The molecular distributions of water-soluble organic acids as well as the high ratio of phthalic acid (Ph)/azelaic acid (C9) indicated severe aromatic secondary organic aerosol pollution during the haze episodes, especially in winter. The diurnal patterns, size distributions, and concentration ratios of specific organic acids were investigated to reveal the pollution characteristics and possible sources of major organic acids in particulate matter in Beijing during haze events. Multiple linear regression was used to tentatively quantify the relative contributions of photochemical oxidation and aqueous-phase oxidation to the formation of total water-soluble organic acids in PM1, PM2.5 and PM10 during haze episodes. The formation mechanism of sulfate and nitrate was also investigated for comparison. Different from the secondary formation of sulfate, the secondary formation of water-soluble organic acids showed enhanced contribution of gas-phase photochemical oxidation though the aqueous-phase oxidation was the dominant process. CapsuleMolecular analyses of organic acids in PM1, PM2.5 and PM10 in Beijing during haze periods revealed their pollution characteristics, possible sources and formation mechanism.

Seasonal and multi-annual trends of bivalve toxicity by PSTs in Portuguese marine waters

Temporal and spatial trends of paralytic shellfish toxins (PSTs) in bivalves from Portuguese estuarine and coastal waters, and connectivity of bivalve toxicity among the harvest areas, were examined using long-term data from the national biotoxin monitoring programme. Data from 1994 to 2017 were chosen for commercial bivalve species sensitive to PSTs, and for production areas exhibiting recurrent episodes of bivalve toxicity. Mussels (Mytilus spp.) and cockles (Cerastoderma edule) from the Ria de Aveiro, Mondego estuary, Óbidos lagoon and Ria Formosa, and wedge clams (Donax trunculus) and surf clams (Spisula solida) from the coastal areas Aguda and Olhão were selected. Bivalve toxicity data point to higher incidents of PST episodes in autumn and winter, although in 2008 the toxicity of mussels and cockles in the three estuarine areas was registered in summer. Most likely, favourable oceanographic conditions triggered the bloom formation of Gymnodinium catenatum, which is the species responsible for paralytic shellfish poisoning in Portuguese waters. Episodes in the southern coast of Portugal were less recurrent, although values above the PST regulatory limit displayed also a seasonal signal with a peak between autumn and early winter. On the basis of the number of weeks per month that bivalves showed elevated toxicity values, a connectivity index was defined for the surveyed areas. High connectivity was obtained among Aveiro, Mondego and Óbidos, which are 180 km apart, suggesting that G. catenatum cells are imported from blooms formed or reaching the coastal waters adjacent to these systems. During episodes of elevated toxicity, toxin profiles in contaminated mussels and cockles were dominated by N-sulfocarbamoyl compounds, which are the major toxins produced by the toxic dinoflagellate G. catenatum. The identification of coupled systems relatively to bivalve toxicity has an impact on monitoring programmes and allows improved decision-making on closures of bivalve harvest areas affected by toxic algae.

The significant contribution of HONO to secondary pollutants during a severe winter pollution event in southern China

Abstract. Nitrous acid (HONO) can strongly affect atmospheric photochemistry in polluted regions through the production of hydroxyl radicals (OHs). In January 2017, a severe pollution episode occurred in the Pearl River Delta (PRD) of China, with maximum hourly PM2.5, ozone, and HONO levels reaching 400 µg m−3, 150 ppb, and 8 ppb, respectively, at a suburban site. The present study investigated the sources and processes generating such high HONO concentrations and the role of HONO chemistry in this severe winter episode. Four recently reported HONO sources were added to the Community Multiscale Air Quality (CMAQ) model, including RH-dependent (relative humidity) and light-enhancing effects on heterogeneous reactions, photolysis of particulate nitrate in the atmosphere, and photolysis of HNO3 and nitrate on surfaces. The revised model reproduced the observed HONO and significantly improved its performance for O3 and PM2.5. The model simulations showed that the heterogeneous generation on surfaces (with RH and light effects) was the largest contributor (72 %) to the predicted HONO concentrations, with the RH-enhancing effects more significant at nighttime and the light-enhancing effects more important in the daytime. The photolysis of total nitrate in the atmosphere and deposited on surfaces was the dominant HONO source during noon and afternoon, contributing above 50 % of the simulated HONO. The HONO photolysis was the dominant contributor to HOx production in this episode. With all HONO sources, the daytime average O3 at the Heshan site was increased by 24 ppb (or 70 %), compared to the simulation results without any HONO sources. Moreover, the simulated mean concentrations of TNO3 (HNO3+ fine particle NO3-) at the Heshan site, which was the key species for this haze formation, increased by about 17 µg m−3 (67 %) due to the HONO chemistry, and the peak enhancement reached 55 µg m−3. This study highlights the key role of HONO chemistry in the formation of winter haze in a subtropical environment.

Characteristics, Formation Mechanisms and Potential Transport Pathways of PM2.5 at a Rural Background Site in Chongqing, Southwest China

ABSTRACT Daily PM2.5 samples were collected at a rural background station (JinYun) located in Chongqing across four consecutive seasons from October 2014 to July 2015. The major water-soluble inorganic ions (WSIIs), organic carbon (OC) and elemental carbon (EC) were analyzed, and their chemical characteristics, transport pathways and potential source regions were investigated. The average annual PM2.5 concentration was 56.2 ± 31.0 µg m–3, of which secondary inorganic aerosol (SNA) and carbonaceous aerosols composed 41.0% and 29.4%, respectively. Higher concentrations of and contributions from SO42–, which were likely caused by the secondary transformation of SO2 into SO42–, were observed in summer than in autumn and spring. Additionally, transportation from the urban area of Chongqing (Yubei) played an important role in elevating the SO42– during this season. Although the accumulation of PM2.5 during pollution episodes in winter was also due to aqueous-phase reactions, based on the entire year, NO3– formation may have been primarily driven by homogeneous gas-phase reactions. Furthermore, the aerosol environment was ammonium-rich, and NH4+ formation promoted the production of NO3– at lower temperatures. The carbonaceous component, which consisted of 81.0–84.6% OC, exhibited higher concentrations in winter than in the other seasons; 50.0–77.2% of the total OC, in turn, was contributed by primary organic carbon (POC). Potential source contribution function (PSCF) analysis suggests that the site was mainly affected by regional pollution originating in the southwestern and northern areas of Chongqing.

An overview of some challenges in the studies in the emission of particulate matter

Studies of particulate matter (PM) emission from solid fuel combustion are important due to the fact that PM has a negative impact on the environment and on human health. The combustion of solid fuels such as coal and biomass for the generation of heat and electricity is one of the principal contributors to PM emission. Coal fired boilers are widely used in power plants due to their low cost despite the fact that coal combustion produces significant amounts of pollutants. A large fraction of the emission of anthropogenic PM and black carbon comes from the household coal combustion for heating and cooking. Residential coal combustion has significantly high emission factors of PM, elemental carbon, and organic carbon, due to incomplete combustion and the lack of an installation of an air pollution control. During high PM pollutant episodes in winter, coal combustion is considered the largest anthropogenic source, especially for organic aerosols. This work supports the synthesis of recent studies on organic pollutants emitted during combustion processes. The paper presents the forms of organics in solid phase, as condensed on the surface of the PM.

Variability of depolarization of aerosol particles in the megacity of Beijing: implications for the interaction between anthropogenic pollutants and mineral dust particles

Abstract. East Asia is suffering from severe air pollution problems due to intensive anthropogenic emissions and natural mineral dust aerosols. During transport, the aerosol particles undergo complex mixing processes, resulting in great impacts on regional air quality, human health and climate. In this study, we conducted a long-term observation using an optical particle counter equipped with a polarization detection module (POPC) at an urban site in Beijing. Mass concentrations of both PM2.5 and PM10 estimated from POPC compared well with ground-based measurements. The results revealed that the observed depolarization ratio (δ, termed as the ratio of the intensity of the s-polarized signal to the intensity of the 120∘ backward scattering signal [s/(s+p)]) for aerosol particles in the fine mode was generally much lower in summer than that in spring as a result of predominance of different aerosol types. Mineral dust particles in the coarse mode normally had a large δ value (0.3±0.05) owing to their nonspherical shape; however, particles in the fine mode mostly had water-soluble compositions, which led to an apparent decrease of their δ values in particular high relative humidity (RH) conditions. Because the observation site was subject to the impact of frequent dust events in spring, the δ value of particle at 1 µm was almost twice as high as that (0.07±0.01) in summer. Based on size-resolved δ values, anthropogenic pollutants, mineral dust and polluted mineral dust particles and their contribution to local air quality could be well distinguished. About 26.7 % of substandard days (daily averaged PM2.5 concentration larger than 75 µg m−3) in Beijing featured high atmospheric loading of coarse-mode particles in winter and springtime. In particular, during severe pollution episodes in winter, the δ values of coarse-mode particles decreased by 13 %, which implies a high possibility of dust-related heterogeneous processes in pollution formation. During dust events, δ values of particles with optical size (Dp) of 5 µm evidently decreased, with an increase of the PM2.5 ∕ PM10 ratio as well as RH, indicating the morphological changes of mineral dust. This study confirmed that high RH tends to promote water absorption processes on the dust surface as well as the coating of soluble compounds, and suggested that remote sensing techniques for aerosols may underestimate the impact of dust particles due to the complex mixing of dust and anthropogenic particles in urban areas, and the interaction between dust particles and pollutants should be considered well by the optical model.

The Cost of Acute Respiratory Infections With Cough Among Urban Aboriginal and Torres Strait Islander Children.

Introduction: Acute respiratory infections with cough (ARIwC) contribute considerably to childhood morbidity, yet few studies have examined the cost of these illnesses among Australian children. Moreover, of the few studies that have, none are inclusive of Aboriginal and/or Torres Strait Islander children, despite this population experiencing a greater burden of respiratory illnesses. This study aimed to determine the costs of ARIwC among urban Aboriginal and/or Torres Strait Islander children from the perspective of caretakers, the public healthcare system, and employers.Methods: This cost of illness study used data collected from Aboriginal and/or Torres Strait Islander children aged <5 years enrolled in a 12 month prospective cohort study conducted through an urban primary healthcare clinic in Queensland, Australia. Illness-related resource use was collected for each episode of ARIwC reported, and costed at market rates. Linear regression was used to (a) examine cost per episode by season of illness onset and cough duration and (b) examine cost per month of observation by baseline child and family characteristics.Results: During the study period, a total of 264 episodes of ARIwC were reported among 138 children. The total mean cost was estimated to be $AU252 per non-hospitalized episode (95%CI 169–334). Caretakers, the public healthcare system and employers incurred 44, 39, and 17% of costs per episode, respectively. After accounting for months of completed follow-ups, the total mean cost per child per year was estimated to be $991 (95%CI 514–1468). Winter episodes and episodes resulting in chronic cough were associated with significantly higher costs per episode. A prior history of wheezing, connections to traditional lands and parent/guardian belief that antibiotics should be given until symptoms resolved were associated with significantly higher cost per child month of observation.Conclusion: The cost of ARIwC in this predominantly disadvantaged population is substantial, particularly for caretakers and this needs to be considered in both clinical management and public health initiatives. The importance of cultural factors on health and burden of illness should not be overlooked. Further research into the prevention of chronic cough may play an important role in reducing the economic burden of pediatric respiratory infections.

The contribution of the Beijing, Tianjin and Hebei region's iron and steel industry to local air pollution in winter

The Beijing, Tianjin and Hebei region (BTH) in China is a highly populated area that has recently experienced frequent haze episodes in winter. With high production capacities, the iron and steel industry (ISI) has long been a key source of air pollutants in BTH and is thus considered responsible for the degradation of local air quality. Here, we conducted a cross-disciplinary research combining the Weather Research and Forecasting with Chemistry (WRF/Chem) model, the multiregional input-output model (MRIO) and the health assessment model to explore the impacts of the ISI on air pollution in the BTH region in January 2012. Our results show large increases in air pollution due to direct ISI emissions, with up to a 90 μg/m3 monthly average of fine particulate matter (PM2.5) and sulfur dioxide (SO2) in eastern Tangshan and western Handan. In addition to direct emissions, the ISI has induced large quantities of indirect emissions from upstream sectors (e.g., the electricity and transportation sectors), leading to PM2.5, SO2 and NOx increases of 2–10 μg/m3 in BTH. Considering the direct and indirect emissions, we estimated that 275 (233–313) PM2.5-related mortalities occurred in January, and approximately 42% of these premature deaths occurred in Tangshan. A high rate of premature deaths also occurred in urban Beijing due to its high population density. Revealing the great health burden caused by the ISI, our results underscore the necessity for the Chinese government to reduce air pollutant emissions from the ISI and its upstream industries in BTH.

Implementing prevention of seasonal affective disorder from patients\u2019 and physicians\u2019 perspectives \u2013 a qualitative study

BackgroundSeasonal affective disorder (SAD) is a seasonally recurrent type of major depression that has detrimental effects on patients’ lives during winter. Little is known about how it affects patients during summer and about patients’ and physicians’ perspectives on preventive SAD treatment. The aim of our study was to explore how SAD patients experience summers, what type of preventive treatment patients implement, which preventive treatment methods, if any, physicians recommend, and what factors facilitate or hinder implementation/recommendation of SAD prevention.MethodsWe conducted 15 semi-structured interviews, ten with adult patients with a history of SAD and five with physicians. Transcripts were analyzed by two researchers using an inductive thematic analysis approach.ResultsOne group of patients was able to enjoy summer and ignore thoughts of the upcoming winter. The other group feared the impending depressive episode in winter, and this fear negatively impacted these patients’ well-being during the summer. Preventive treatment was a relevant issue for all patients, and all but one person implemented SAD prevention during summer. We identified six factors that influenced patient use of preventive treatment of SAD. Four factors occur on an individual level (knowledge about disease and preventive treatment options, experience with treatment in acute phase, acceptability of intervention, willingness to take responsibility for oneself), one on an interpersonal level (social and work environment), and one on a structural level (healthcare system). All psychiatrists recommended some kind of preventive intervention, most commonly, lifestyle changes. Four factors influenced psychiatrists in recommending prevention of SAD (patient expectations, disease history and stability, risk/benefit ratio, lack of evidence).ConclusionsSuccess in the implementation of SAD prevention does not solely depend on the willingness of the patients, but is also influenced by external factors. Raising awareness of SAD among general practitioners and low-level access to mental-health support could help patients find appropriate help sooner. To better guide the optimal treatment choice, comparative effectiveness research on treatments to prevent a new onset in patients with a history of SAD and clinical practice guidelines on SAD are needed.