Downwind Sites Research Articles

Measurement System Evaluation for Upwind/Downwind Sampling of Fugitive Dust Emissions

Eight different PM10 samplers with various size-selective inlets and sample flow rates were evaluated for upwind/ downwind assessment of fugitive dust emissions from two sand and gravel operations in southern California during September through October 2008. Continuous data were acquired at one-minute intervals for 24 hours each day. Integrated filters were acquired at five-hour intervals between 1100 and 1600 PDT on each day because winds were most consistent during this period. High-volume (hivol) size-selective inlet (SSI) PM10 Federal Reference Method (FRM) filter samplers were comparable to each other during side-by-side sampling, even under high dust loading conditions. Based on linear regression slope, the BGI low-volume (lovol) PQ200 FRM measured ~18% lower PM10 levels than a nearby hivol SSI in the source-dominated environment, even though tests in ambient environments show they are equivalent. Although the TSI DustTrak DRX PM10 concentrations did not equal those from the hivol SSI, both instruments were highly correlated (R = 0.9) at the two downwind sites. Multiple size ranges from the TSI DustTrak DRX and Grimm optical particle counters (OPC) allowed the identification of spatial non-uniformity for sources within and outside the facilities. Narrow dust plumes were only detected by some of the continuous instruments across the sampler array. Upwind PM10 concentrations at one of the locations were higher than the downwind concentrations owing to a high concentration of industrial and vehicular activities. The shorter-duration measurements and quantification of super-coarse (> 10 µm) particles with high deposition velocities available from optical particle counters is needed to evaluate the effects of local emissions on both upwind and downwind samples.

Polychlorinated biphenyls in two salt marsh sediments of the Venice Lagoon

Polychlorinated biphenyls (PCBs) were measured in two dated salt marsh cores of the Venice Lagoon to assess their input chronology and to evaluate the importance of atmospheric deposition as a source. Sampling sites were chosen in order to evidence the differences between areas located leeward and windward with respect to inputs originating in both the city of Venice and the industrial area. Concentrations of PCB indicators (0.13-15.6 ng g⁻¹) increased gradually from the 1930s, reached maxima from the 1950s to the late 1970s, and then decreased. PCB loadings to marshes are driven by both the atmospheric deposition and the resuspension of subtidal sediments, this latter being more important for heavier congeners. The downwind marsh recorded higher fluxes (0.06-9.72 ng cm⁻² year⁻¹) than the upwind one (0.01-0.53 ng cm⁻² year⁻¹). Recent fluxes are rather consistent with bulk deposition measurements. A higher contribution of CB-101 and CB-118 was detected in the intermediate layers of the downwind site, suggesting a different PCB source for the corresponding time interval. In the other marsh, PCBs showed a rather constant composition at all levels (mostly CB-153, CB-138 and CB-180), accounting for a regional influence. Deep layers showed an enrichment of higher chlorinated congeners at both sites, whereas recent samples conserve the patterns typical of surficial and subsurficial subtidal sediments. The scientific approach adopted in this research can be considered as a sort of methodological procedure for the determination of fluxes and pathways of PCBs through the study of marsh cores.

Contrasting Diurnal Variations in Fossil and Nonfossil Secondary Organic Aerosol in Urban Outflow, Japan

Diurnal variations of fossil secondary organic carbon (SOC) and nonfossil SOC were determined for the first time using a combination of several carbonaceous aerosol measurement techniques, including radiocarbon (¹⁴C) determinations by accelerator mass spectrometry, and a receptor model (chemical mass balance, CMB) at a site downwind of Tokyo during the summer of 2007. Fossil SOC showed distinct diurnal variation with a maximum during daytime, whereas diurnal variation of nonfossil SOC was relatively small. This behavior was reproduced by a chemical transport model (CTM). However, the CTM underestimated the concentration of anthropogenic secondary organic aerosol (ASOA) by a factor of 4-7, suggesting that ASOA enhancement during daytime is not explained by production from volatile organic compounds that are traditionally considered major ASOA precursors. This result suggests that unidentified semivolatile organic compounds or multiphase chemistry may contribute largely to ASOA production. As our knowledge of production pathways of secondary organic aerosol (SOA) is still limited, diurnal variations of fossil and nonfossil SOC in our estimate give an important experimental constraint for future development of SOA models.

Chemical Mass Balance Source Apportionment of Ambient Total Suspended Particulate Matters Near Jhuoshuei River in Central Taiwan

Based on an investigation of ambient total suspended particulate (TSP) matter concentrations, this study not only evaluates how the TSP levels deteriorate the air quality near Jhuoshuei River in central Taiwan, but also demonstrates that the monsoon season profoundly influences ambient TSP concentrations. Samples of ambient TSP obtained from representative areas in target areas during monsoon and other seasons in 2005–2006 were collected for use in receptor modeling. A chemical mass balance model version 8 (CMB8) developed by the United States Environmental Protection Agency, was implemented based on TSP emission information from version 5.1 of the Taiwan Emission Data System (TEDS5.1) and a source profile from SPECIATE3.2. CMB8 model estimates indicated that windblown soil coming from the Jhuoshuei riverbed largely contributed to the receptor site during the monsoon season. Statistical analysis revealed that metal species appearing during the monsoon season have a higher correlation with each other than during other seasons. The well-known fact that these elements are emitted from soil suggests that the soil source significantly contributes to TSP concentration at downwind sampling sites during the monsoon season. Moreover, the concentration of TSPs at downwind sites is significantly higher than that at upwind site during monsoons, posing a potential risk to human health in the downwind residential communities.

Air quality during the 2008 Beijing Olympics: secondary pollutants and regional impact

Abstract. This paper presents the first results of the measurements of trace gases and aerosols at three surface sites in and outside Beijing before and during the 2008 Olympics. The official air pollution index near the Olympic Stadium and the data from our nearby site revealed an obvious association between air quality and meteorology and different responses of secondary and primary pollutants to the control measures. Ambient concentrations of vehicle-related nitrogen oxides (NOx) and volatile organic compounds (VOCs) at an urban site dropped by 25% and 20–45% in the first two weeks after full control was put in place, but the levels of ozone, sulfate and nitrate in PM2.5 increased by 16%, 64%, 37%, respectively, compared to the period prior to the full control; wind data and back trajectories indicated the contribution of regional pollution from the North China Plain. Air quality (for both primary and secondary pollutants) improved significantly during the Games, which were also associated with the changes in weather conditions (prolonged rainfall, decreased temperature, and more frequent air masses from clean regions). A comparison of the ozone data at three sites on eight ozone-pollution days, when the air masses were from the southeast-south-southwest sector, showed that regional pollution sources contributed >34–88% to the peak ozone concentrations at the urban site in Beijing. Regional sources also contributed significantly to the CO concentrations in urban Beijing. Ozone production efficiencies at two sites were low (~3 ppbv/ppbv), indicating that ozone formation was being controlled by VOCs. Compared with data collected in 2005 at a downwind site, the concentrations of ozone, sulfur dioxide (SO2), total sulfur (SO2+PM2.5 sulfate), carbon monoxide (CO), reactive aromatics (toluene and xylenes) sharply decreased (by 8–64%) in 2008, but no significant changes were observed for the concentrations of PM2.5, fine sulfate, total odd reactive nitrogen (NOy), and longer lived alkanes and benzene. We suggest that these results indicate the success of the government's efforts in reducing emissions of SO2, CO, and VOCs in Beijing, but increased regional emissions during 2005–2008. More stringent control of regional emissions will be needed for significant reductions of ozone and fine particulate pollution in Beijing.

Emissions of polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) from both of point and area sources of an electric-arc furnace-dust treatment plant and their impacts to the vicinity environments

This study was set out to investigate emissions of polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) from both the stack (i.e., point source) and plant fugitives (i.e., area source) of an electric-arc furnace-dust treatment plant (EAFDTP) and their impact to the vicinity environments. The emission rate of the point source (2360 ng I-TEQ h −1) was determined directly by measuring PCDD/F concentrations of the stack flue gas. The emission rate of the area source (1080 ng I-TEQ m −2 h −1) was estimated by using the Industrial Sources Complex Short-Term (ISCST3) model based on concentrations measured at the downwind side of the plant. The mean emission factors of 785 and 893 ng I-TEQ ton −1 ZnO were found for the point and area source, respectively. The above results suggest that the area source accounted for more than 50% of total PCDD/F emissions for the selected EAFDTP. The contribution of the point source to the atmospheric PCDD/F concentrations of the upwind site and downwind site of the EAFDTP were 0 and 0.27 fg I-TEQ Nm −3, respectively. The contributions of the area source were 0.020 and 3.3 fg I-TEQ Nm −3, respectively. The total contribution of the selected EAFDTP (including both the point and area sources) to the concentrations in both upwind and downwind side vicinities were all less than 10%. Finally, the impact of PCDD/F emissions from the selected EAFDTP to the vicinity atmospheric environments was discussed in the present study.

Assessment of bioaerosols at a concentrated dairy operation

Increased bioaerosol loadings in downwind plumes from concentrated animal feeding operations (CAFOs) may increase the risk for allergy and infection in humans. In this study, we monitored airborne concentrations of culturable bacteria and fungi at upwind (background) and downwind sites at a 10,000 milking cow dairy over the course of a year. The average bacterial concentrations at the upwind site were 8.4 × 103 colony forming units (CFU) m−3 and increased to 9.9 × 105 CFU m−3 at the downwind edge of the cattle lots, decreasing to 6.3 × 104 CFU m−3 200 m farther downwind. At the same sites, the average fungal concentrations were 515, 945, and 1,010 CFU m−3, respectively. Significant correlations between the ambient weather conditions and airborne fungal and bacterial concentrations were identified. Sequence analysis of PCR-amplified DNA from bacterial clones and fungal isolates revealed genus and species level differences between upwind and downwind sites. Although we could not cultivate gram-negative bacteria, bacterial clones at downwind sites identified as being gram-negative matched with the following genera: Acinetobacter, Bradyrhizobium, Escherichia, Idiomarina, Methylobacterium, Ralstonia, and Novosphingobium. Fungal isolates from downwind matched with the following genera: Acremonium, Alternaria, Ascomycte, Aspergillus, Basidiomycete, Cladosporium, Davidiella, Doratomyces, Emericella, Lewia, Onygenales, Penicillium, Rhizopus, and Ulocladium. None of the bacterial and fungal sequence matches were affiliated with genera and species known to be pathogenic to humans. Overall, the data suggest that exposure to bioaerosols in the downwind environment decreases with increasing distance from the open-lot dairy.

The Windy Commons?

Wind power generation is growing rapidly in the United States, doubling nearly every three years since 1998. Yet, wind is an open access resource, and past experiences with open access resources suggest that tragedies of the commons may occur. While the engineering literature has focused on turbine siting within a wind farm to maximize profits and minimize interaction effects, the economics literature has overlooked interaction effects between windfarms. We provide a qualitative framework for measuring wake externalities and use simulation modeling to determine their magnitude. We find that: a) turbine wake externalities (and thus losses) to downwind sites increase with the square of wind velocity and can be substantial, b) decentralized ownership across wind farms leads to overcapitalization in upwind sites and undercapitalization in downwind sites relative to sole ownership, c) when multiple potential patches are considered, more land will be used upwind for wind power under decentralized ownership, and d) numerical simulations suggest that total rents are reduced under decentralized ownership by up to 12%, while total power produced increases by approximately 10%. Under our central parameters, decentralized ownership may be preferred to a sole owner, depending on the value society places on clean power relative to dirty power.

Spatial Patterns of Plastic Debris along Estuarine Shorelines

The human population generates vast quantities of waste material. Macro (>1 mm) and microscopic (<1 mm) fragments of plastic debris represent a substantial contamination problem. Here, we test hypotheses about the influence of wind and depositional regime on spatial patterns of micro- and macro-plastic debris within the Tamar Estuary, UK. Debris was identified to the type of polymer using Fourier-transform infrared spectroscopy (FT-IR) and categorized according to density. In terms of abundance, microplastic accounted for 65% of debris recorded and mainly comprised polyvinylchloride, polyester, and polyamide. Generally, there were greater quantities of plastic at downwind sites. For macroplastic, there were clear patterns of distribution for less dense items, while for microplastic debris, clear patterns were for denser material. Small particles of sediment and plastic are both likely to settle slowly from the water-column and are likely to be transported by the flow of water and be deposited in areas where the movements of water are slower. There was, however, no relationship between the abundance of microplastic and the proportion of clay in sediments from the strandline. These results illustrate how FT-IR spectroscopy can be used to identify the different types of plastic and in this case was used to indicate spatial patterns, demonstrating habitats that are downwind acting as potential sinks for the accumulation of debris.

Atmospheric Ammonia Mixing Ratios at an Open-Air Cattle Feeding Facility

Mixing ratios of total and gaseous ammonia were measured at an open-air cattle feeding facility in the Texas Panhandle in the summers of 2007 and 2008. Samples were collected at the nominally upwind and downwind edges of the facility. In 2008, a series of far-field samples was also collected 3.5 km north of the facility. Ammonium concentrations were determined by two complementary laboratory methods, a novel application of visible spectrophotometry and standard ion chromatography (IC). Results of the two techniques agreed very well, and spectrophotometry is faster, easier, and cheaper than chromatography. Ammonia mixing ratios measured at the immediate downwind site were drastically higher (∼2900 parts per billion by volume [ppbv]) than those measured at the upwind site (≤200 ppbv). In contrast, at 3.5 km away from the facility, ammonia mixing ratios were reduced to levels similar to the upwind site (≤200 ppbv). In addition, PM10 (particulate matter <10 μm in optical diameter) concentrations obtained at each sampling location using Grimm portable aerosol spectrometers are reported. Time-averaged (1-hr) volume concentrations of PM10 approached 5 × 1012 nm3 cm−3. Emitted ammonia remained largely in the gas phase at the down-wind and far-field locations. No clear correlation between concentrations of ammonia and particles was observed. Overall, this study provides a better understanding of ammonia emissions from open-air animal feeding operations, especially under the hot and dry conditions present during these measurements.

Variations of aerosol properties due to regional source contributions and impacts on ozone levels:a study in a south China city

Environmental context.Regional atmospheric contaminants from both anthropogenic and natural events (industrial activities, biomass burning, dust events) can have large impacts on the aerosol properties of distant downwind sites. Data showing the influence of regional sources on air quality in Hong Hong are presented. In particular, the changes in aerosol properties (e.g. mass concentration and particle size distribution), and their effects on photochemical ozone formation, is discussed. Abstract.Variations of PM10 concentration and particle size distribution owing to the influence of industrial activities in mainland China, biomass burning in South East Asia and dust storms in north-west China, as well as the aerosol impact on surface ozone concentration, have been studied by a combination of analysis of air mass origin (by back-trajectory calculation), remote sensing techniques, regional chemical transport and photochemical box models. The PM10 concentrations in Hong Kong were reduced by 24–57% owing to the industrial downtime during the Chinese New Year period. A photochemical box model coupled with a radiative transfer model has been employed to predict surface maximum ozone concentrations during high aerosol loading days. Increase of aerosol optical depth can lead to 7–32% reduction of surface maximum ozone concentration. Our results emphasise the need for regional cooperation in tackling the local air pollution of Hong Kong.

Year-long assessment of airborne endotoxin at a concentrated dairy operation

In this study, we monitored total airborne endotoxins at upwind and downwind sites at a large open-lot dairy each month for a year. At the upwind site, the average airborne concentration was 28.5 endotoxin units (EU) m−3, while at the downwind edge of the lot and 200 m from the lot edge, the average concentrations were 169 and 72 EU m−3, respectively. At the downwind edge of the lot, there was a significant correlation between the airborne endotoxin concentration and wind speed or air temperature. A comparison between total and inhalable airborne endotoxin concentrations, near the end of the study, revealed no significant differences between the two endotoxin collection methods. Our data suggest that endotoxin exposure can be reduced as one increases their distance from the open-lot dairy.

수도권 지역 PM10의 PAHs 농도 특성

The concentrations of PAHs in fine particles were determined at two sites, which were Jongno, one of the urban core sites of Seoul, and Yongin, a downwind site of Seoul. The average concentration of PAHs in was with the range of at Jongno site of Seoul from August 2006 to August 2007, and with the range of at Yongin site from September to November of 2006. In the results of monthly comparison, the concentration of PAHs in August was the lowest level of , but the highest level of in January. The seasonal comparison showed the concentration in winter was higher by the factor of 11.9 than in summer. The concentrations of PAHs during a warm period (NovemberMarch) increased as 5.1 times higher than those during a cold period (AprilOctober). The concentrations of PAHs were assumed to be largely attributed to the consumption of fossil fuels, temperature, mixing height, and photochemical reactions in Seoul metropolitan area.

REP-PCR tracking of the origin and spread of airborne Staphylococcus aureus in and around chicken house

Staphylococcus aureus was used as an indicator to study the origin and spread of microbial aerosol in and around chicken houses. Air samples indoor, upwind (10 and 50 m), and downwind (10, 50, 100, 200, and 400 m) of four chicken houses were collected using Andersen‐6 stages sampler. The concentrations of S. aureus were determined for every sample site. Isolation of S. aureus from chicken feces was performed according to the standard method. The genetic relationship among the isolates was determined by profiles of PCR‐amplified repetitive extragenic palindromic (REP‐PCR) elements. The results showed that the concentrations of S. aureus indoor of four chicken houses were higher than those upwind and downwind sites (P < 0.05 or P < 0.01), but there were no significant concentration differences among downwind sites (P > 0.05). The fingerprints and the phylogenetic tree indicated that a part of the S. aureus (55.6%, 10/18) isolates from indoor air had the same REP‐PCR fingerprints as feces isolates. Consequently, most isolates (57.1%, 20/35) from downwind 10, 50, 100, 200, even 400 m had the same REP‐PCR fingerprints as those from indoor or feces. These data indicated that some isolates from downwind and indoor originated from the chicken feces. However, those isolates from upwind had low similarity (similarity index 0.6–0.87) to those from indoor or feces. Therefore, the isolates upwind were not from the chicken feces or indoor. These results suggest that microbes in chicken feces can be aerosolized and spread indoor and outdoor, especially to downwind of the chicken houses. It should have an important epidemiological and public health significance.Practical ImplicationsThus, the use of S. aureus as an indicator to study the origin and spread of airborne pathogens from chicken houses is potentially useful for enhancing public health and understanding the airborne epidemiology of this pathogen. Meanwhile it can provide evidence for studying the spreading model of airborne pathogens.

Air pollutant concentrations near three Texas roadways, part II: Chemical characterization and transformation of pollutants

Spatial gradients of vehicular emitted air pollutants were measured in the vicinity of three roadways in the Austin, Texas area: (1) State Highway 71 (SH-71), a heavily traveled arterial highway dominated by passenger vehicles; (2) Interstate 35 (I-35), a limited access highway north of Austin in Georgetown; and (3) Farm to Market Road 973 (FM-973), a heavily traveled surface roadway with significant truck traffic. A mobile monitoring platform was used to characterize the gradients of CO and NO x concentrations with increased distance from each roadway, while concentrations of carbonyls in the gas-phase and fine particulate matter mass and composition were measured at stationary sites upwind and at one (I-35 and FM-973) or two (SH-71) downwind sites. Regardless of roadway type or wind direction, concentrations of carbon monoxide (CO), nitric oxide (NO), and oxides of nitrogen (NO x ) returned to background levels within a few hundred meters of the roadway. Under perpendicular wind conditions, CO, NO and NO x concentrations decreased exponentially with increasing distance perpendicular to the roadways. The decay rate for NO was more than a factor of two greater than for CO, and it comprised a larger fraction of NO x closer to the roadways than further downwind suggesting the potential significance of near roadway chemical processing as well as atmospheric dilution. Concentrations of most carbonyl species decreased with distance downwind of SH-71. However, concentrations of acetaldehyde and acrolein increased farther downwind of SH-71, suggesting chemical generation from the oxidation of primary vehicular emissions. The behavior of particle-bound organic species was complex and further investigation of the size-segregated chemical composition of particulate matter (PM) at increasing downwind distances from roadways is warranted. Fine particulate matter (PM 2.5) mass concentrations, polycyclic aromatic hydrocarbons (PAHs), hopanes, and elemental carbon (EC) concentrations generally exhibited concentrations that decreased with distance downwind of SH-71. Concentrations of organic carbon (OC) increased from upwind concentrations immediately downwind of SH-71 and continued to increase further downwind from the roadway. This behavior may have primarily resulted from condensation of semi-volatile organic species emitted from vehicle sources with transport downwind of the roadway.

Characteristics of malodor pollutants and aromatic VOCs around an urban valley in Korea

In this study, the environmental behavior of malodor pollutants (MPs) [including reduced sulfur compounds (RSCs)] and aromatic volatile organic compounds (AVOCs) were investigated around urban valley areas during several field campaigns (February through December 2006). The MPs measured in the study area include the RSCs (H(2)S, CH(3)SH, DMS, and DMDS), ammonia (NH(3)), and styrene (STY); the AVOCs include benzene (BEN), toluene (TOL), ethylbenzene (EB), m,p-xylene (MPX), and o-xylene (OX). The variation of most MP concentrations (except for DMDS) was found to be larger than that of AVOCs. It was found that STY (2,346 +/- 4,867 ppbv) was the most dominant MP followed by NH(3) (447 +/- 285), CH(3)SH (16 +/- 41), and the others (<8). The magnitude of AVOCs was found in the following descending order: TOL (1.4 +/- 2.2 ppbv), EB (1.0 +/- 2.1), MPX (0.9 +/- 2.0), and the others (<0.8). The concentration levels of most MPs on industrial (I) and downwind (D) sites were up to an order of magnitude higher than those at non-industrial (N) and upwind (U) sites. For most AVOCs, the former was ~3 times higher than the latter. For malodor intensity in RSCs, CH(3)SH was the dominant contributor. The concentration difference in target compounds between the sites/periods is likely to be caused by the combined effects such as emission sources, geographical features (e.g., semi-closed topography), and meteorological conditions (e.g., wind directions) in and outside the urban valley.

Size-Resolved Source Apportionment of Airborne Particle Mass in a Roadside Environment

Airborne particulate hopanes, steranes, and polycyclic aromatic hydrocarbons (PAHs) were measured in six size fractions < 1.8 microm particle diameter at one site upwind and two sites downwind of the Interstate 5 freeway in San Diego, CA. The smallest size fraction collected was exclusively in the ultrafine size range (D(p) < 0.1 microm; PM0.1). Size distributions of hopanes, steranes, and PAHs peaked between 0.10-0.18 microm particle aerodynamic diameter with a tail extending into the PM0.1 size range. This pattern is similar to previous dynamometer studies of hopane, sterane, and PAH size distributions emitted from gasoline- and diesel-powered vehicles. Size-resolved source profiles were combined to form an "on-road" profile for motor oil, diesel, and gasoline contributions to EC and OC. The resulting equations were used to predict source contributions to the size distributions of EC and OC in the roadside environment. The method successfully accounted for the majority of the carbonaceous material in particles with diameter < 0.18 microm, with significant residual material in larger size fractions. The peak in both the measured and predicted EC size distribution occurred between 0.1-0.18 microm particle aerodynamic diameter. The predicted OC size distribution peaked between 0.1-0.18 microm particle diameter, butthe measured OC size distribution peaked between 0.56-1.0 microm particle diameter, possibly because of secondary organic aerosol formation. Predicted OC concentrations in particles with diameter < 0.18 microm were greater than measured values 18 m downwind of the roadway but showed good agreement 37 m downwind. The largest source contributions to the PM0.1 and PM0.18 size fractions were different. PM0.18 was dominated by diesel fuel and motor oil combustion products while PM0.1 was dominated by diesel fuel and gasoline fuel combustion products. Total source contributions to ultrafine (PM0.1) EC concentrations 37 m downwind of the roadway were 44 +/- 6% diesel fuel, 21 +/- 1% gasoline, 5 +/- 6% motor oil, and 30% unknown. Total source contributions to ultrafine (PM0.1) OC concentrations 37 m downwind of the roadway were 46 +/- 5% diesel fuel, 44 +/- 5% gasoline, 20 +/- 15% motor oil with a slight overprediction (11%). Diesel fuel appears to make the single largest contribution to ultrafine (PM0.1) particle mass given the fleet distribution during the current experiment.

Photochemical evolution of submicron aerosol chemical composition in the Tokyo megacity region in summer

We investigate the chemical transformation of submicron aerosol in the Tokyo megacity region in summer. An Aerodyne quadrupole aerosol mass spectrometer (AMS) was deployed both at an urban site in Tokyo (35°39′N, 139°40′E) and a suburban site (downwind site) in Saitama (36°05′N, 139°33′E) in the summer of 2004. The temporal evolution of size‐resolved chemical compositions of submicron (PM1) aerosols during photochemical smog episodes are investigated using the photochemical age derived from the combination of alkyl nitrate‐to‐hydrocarbon ratio and NOz/NOy ratio (where NOz is defined as the total reactive nitrogen oxides (NOy) excluding nitrogen oxides (NOx)). The photochemical age observed at the downwind site was about 12 h in most aged air. Organic aerosols (OA) and sulfate (SO42−) were major constituents of PM1 aerosols (40–50% and 20–30%, respectively) at both sites during the observation period and their fractions showed no large variation with the NOz/NOy ratio. Mass ratios of OA and SO42− to black carbon (BC) largely increased with the NOz/NOy ratio (by factors of ∼3 and ∼2, respectively), indicating the significance of secondary formation of these compounds in controlling PM1 mass concentrations. We also investigate the photochemical evolution of OA mass spectra observed by the AMS. The mass‐to‐charge ratio (m/z) peaks of organic compounds relative to BC mass generally showed an increase with the NOz/NOy ratio. These increasing trends vary significantly for different m/z peaks, suggesting the complexity of the temporal evolution of organic functional groups. The m/z 44 and 45 peaks, which are good markers of carboxylic groups in organic particles, showed larger increases than any other m/z peaks, suggesting an efficient formation of carboxylic functional groups on a timescale of hours during the measurement period.

Characterization of PM2.5 and conversion rate of sulfur dioxide to sulfate in inland areas of Taiwan

The purpose of this study was to investigate the sulfur conversion rate and the characterization of PM2.5 particulate matter and acidic gases in inland Taiwan region. The measurements were taken at two different sites located near the fossil fuel power plant in central Taiwan. First site was Wufong and the other site was Nantou, which is located 15 km south from Wufong. PM2.5 and gaseous acids were measured by annular denuder system. PM2.5 ionic species including SO42–, NO3–, NH4+, Cl–, Ca2+, K+, Na+, and H+and gaseous HNO3 and HCl were analyzed. Results showed that the average ratio of PM2.5 and SO42– was higher during daytime, probably due to the anthropogenic activities. Wind field map also clearly displayed that Wufong was located upwind and Nantou was located downwind during daytime. Sulfur conversion ratio in the downwind site was higher than upwind site. Experimental data showed that sulfur conversion rate between these sites was 5%–9% h–1. The increased PM2.5 and SO2 concentrations recorded in the Nantou site were from the direction of Taichung city during daytime.

Acidic gases, ammonia and water-soluble ions in PM 2.5 at a coastal site in the Pearl River Delta, China

Real-time measurements of acidic trace gases (HCl, HNO 3, HONO, and SO 2), ammonia, and water-soluble ions in PM 2.5 were conducted at Xinken, a coastal site downwind of Guangzhou, from 4 October to 4 November 2004, as part of the Pearl River Delta (PRD) intensive field campaign. The average concentrations of HCl, HONO, HNO 3, SO 2, and NH 3 are 2.8, 2.9, 6.3, 55.4, and 7.3 μg m −3, respectively, and 2.4, 7.2, 24.1, and 9.2 μg m −3 for Cl −, NO 3 −, SO 4 2−, and NH 4 + in PM 2.5. The diurnal variations of both HCl and HNO 3 showed higher concentrations during daytime and lower concentrations at night, and aerosol Cl − and NO 3 − showed an opposite diurnal patterns to HCl and HNO 3. The diurnal variation of NH 3 showed the similar pattern to that of aerosol NH 4 + with lower concentration during daytime and higher concentration at night. The average concentration of SO 2 during daytime was higher than that at night. The transportation of urban plumes to the sampling site could explain the higher concentration of SO 2 during daytime. HONO showed a clear diurnal variation with lower concentration during daytime and higher concentration at night. The HONO concentrations were positively correlated with the particle surface area concentrations, suggesting the formation of HONO through the heterogeneous conversion on particle surfaces could be significant. The ionic charge balance analysis included the cations derived from filter measurements indicates that the contribution of the cations in fine particle (PM 1.8) to the charge balance is not pronounced. The theoretical equilibrium constant ( K e) of NH 4NO 3 is higher than the observed concentration product ( K m=[NH 3]×[HNO 3]) during daytime, and lower than K m at night. This indicates that the atmospheric conditions during the sampling period did not favor the formation of NH 4NO 3 during daytime.