Field intercomparison of filter pack and denuder sampling methods for reactive gaseous and particulate pollutants

Review of Filters for Air Sampling and Chemical Analysis in Mining Workplaces

This review considers the use of filters to sample air in mining workplace environments for dust concentration measurement and subsequent analysis of hazardous contaminants, especially respirable crystalline silica (RCS) on filters compatible with wearable personal dust monitors (PDM). The review summarizes filter vendors, sizes, costs, chemical and physical properties, and information available on filter modeling, laboratory testing, and field performance. Filter media testing and selection should consider the characteristics required for mass by gravimetry in addition to RCS quantification by Fourier-transform infrared (FTIR) or Raman spectroscopic analysis. For mass determination, the filters need to have high filtration efficiency (≥99% for the most penetrable particle sizes) and a reasonable pressure drop (up to 16.7 kPa) to accommodate high dust loading. Additional requirements include: negligible uptake of water vapor and gaseous volatile compounds; adequate particle adhesion as a function of particle loading; sufficient particle loading capacity to form a stable particle deposit layer during sampling in wet and dusty environments; mechanical strength to withstand vibrations and pressure drops across the filter; and appropriate filter mass compatible with the tapered element oscillating microbalance. FTIR and Raman measurements require filters to be free of spectral interference. Furthermore, because the irradiated area does not completely cover the sample deposit, particles should be uniformly deposited on the filter.

Simultaneous Determination of Gaseous Ammonia and Particulate Ammonium in Ambient Air Using a Cylindrical Wet Effluent Diffusion Denuder and a Continuous Aerosol Sampler

A sensitive and fast method for simultaneous determination of gaseous ammonia (NH₃) and particulate ammonium (NH₄⁺) in ambient air is presented. NH₃ is sampled in a cylindrical wet effluent diffusion denuder (CWEDD) and analyzed online by a continuous flow system with a fluorescence detector (FLD), while NH₄⁺ bound to aerosol particles is sampled in parallel by a condensation growth unit-the aerosol counterflow two-jet unit (CGU-ACTJU) sampler-and analyzed online with another FLD. The sensitive fluorescence detection of ammonium in concentrates of the CWEDD and the ACTJU is based on its reaction with ortho-phthaldialdehyde and sulfite to form isoindol-1-sulfonate. The calibration curve of ammonium is linear in the concentration range of 5 × 10^-9 to 2 × 10^-6 M. The limit of detection (LOD = 3 s/n) values of NH₃ and NH₄⁺ are 3.52 ng m^-3 (5.05 ppt) and 1.04 ng m^-3, respectively. The developed method enables online measuring of distribution of NH₃/NH₄⁺ in ambient air with a time resolution of 1 s. The optimized method was used for the determination of NH₃/NH₄⁺ in urban air in Brno in two campaigns during the winter and summer of 2018. The results obtained by the developed method were compared with a reference method based on the sampling on filters and "dry" diffusion denuders coated by phosphoric acid.

Comparative study on water-soluble inorganic ions in PM2.5 from two distinct climate regions and air quality

Recently, air quality has significantly improved in developed country, but that issue is of concern in emerging megacity in developing country. In this study, aerosols and their precursor gas were collected by NILU filter pack at two distinct urban sites during the winter and summer in Osaka, Japan and dry and rainy seasons in Ho Chi Minh City (HCMC), Vietnam. The aims are to investigate the contribution of water-soluble inorganic ions (WSIIs) to PM_2.5, thermodynamic characterization and possible formation pathway of secondary inorganic aerosol (SIA). The PM_2.5 concentration in Osaka (15.8 μg/m³) is lower than that in HCMC (23.0 μg/m³), but the concentration of WSIIs in Osaka (9.0 μg/m³) is two times higher than that in HCMC (4.1 μg/m³). Moreover, SIA including NH₄⁺, NO₃^- and SO₄^2- are major components in WSIIs accounting for 90% and 76% (in molar) in Osaka and HCMC, respectively. Thermodynamic models were used to understand the thermodynamic characterization of urban aerosols. Overall, statistical analysis results indicate that very good agreement (R² > 0.8) was found for all species, except for nitrate aerosol in HCMC. We found that when the crustal species present at high amount, those compositions should be included in model calculation (i.e. in the HCMC situation). Finally, we analyzed the characteristics of NH₄⁺- NO₃^-- SO₄^2- system. A possible pathway to produce fine nitrate aerosol in Osaka is via the homogeneous reaction between NH₃ and HNO₃, while non-volatile nitrate aerosols can be formed by the heterogeneous reactions in HCMC.

Aerosol sampler for analysis of fine and ultrafine aerosols

A new aerosol sampler based on the original version of Aerosol Counterflow Two-Jets Unit (ACTJU) is described. The ACTJU collector, connected with a water-based Condensation Growth Unit (CGU) placed upstream of the ACTJU, accomplished the quantitative collection of fine and ultrafine aerosol particles down to a few nanometers in diameter. Condensation of water vapor in the CGU enlarges nanometer sized particles to larger sizes in the supermicrometer range and the formed droplets are then collected into water in the ACTJU collector. The continuous collection of aerosols with the CGU-ACTJU sampler allows for the time-resolved measurement of changes in the concentration of particulate constituents. Coupling of the CGU-ACTJU sampler with on-line detection devices allows in-situ automated analysis of water-soluble aerosol components with high time resolution of 1 s (e.g., FIA detection for nitrite or nitrate) or 1 h (e.g., IC detection with preconcentration step for inorganic anions). Under the optimum conditions (the air flow rate of 10 L min^-1 and water flow rate of 1.5 mL min^-1), the limit of detection (IC including the preconcentration) for particulate fluoride, chloride, nitrite, nitrate, sulphate and phosphate is 2.53, 6.64, 24.2, 16.8, 0.12 and 5.03 ng m^-3, respectively. The apparatus is sufficiently robust for its application at routine monitoring of aerosol composition in real-time.

Water-soluble ionic species of coarse and fine particulate matter and gas precursor characteristics at urban and rural sites of central Taiwan

Coarse and fine particulate matter (PM) were taken by a dichotomous sampler, and gas precursors were determined by a denuder sampler at two stations in central Taiwan. Water-soluble ionic constituents of PM and their precursor gases were analyzed by ionic chromatograph. In summer, the daytime/nighttime PM10 concentrations were 37 ± 10/41 ± 18 μg m(-3) and 36 ± 14/34 ± 18 μg m(-3) for Xitun and Jhushan, respectively. Average PM10 concentration in winter was 1.55 and 1.76 times that of summer for Xitun and Jhushan, respectively. PM mass concentrations were similar for both stations, although one station is located in the downtown area of Taichung, and the other is in a rural area with no heavy pollution sources. Water-soluble ionic species content was 38-53 % of PM2.5 and 43-48 % of PM10 mass concentration. HNO3, HCl, and SO2 were high in the daytime; the daytime-to-nighttime concentration ratio was 3.75-6.88 for HNO3,1.7-7.8 for HCl, and 1.45-2.77 for SO2. High NH3 levels were determined in the area, especially in winter, which could be a precursor of NH4 (+) to form particulate matter. In Xitun, motor vehicles downtown and in the industrial district could be sources of air pollution. In contrast, there are few industrial sources at Jhushan; therefore, the transport of air pollutants from upwind of other regions and the accumulation of pollutants could be important PM sources at Jhushan.

Measurement of fine particulate matter water-soluble inorganic species and precursor gases in the Alberta Oil Sands Region using an improved semicontinuous monitor

The ambient ion monitor-ion chromatography (AIM-IC) system, which provides hourly measurements of the main chemical components of PM2.5 (particulate matter with an aerodynamic diameter<2.5 μm) and its precursor gases, was evaluated and deployed from May to July 2011 and April to December 2013 in the Athabasca Oil Sands Region (AOSR) of northeastern Alberta, Canada. The collection efficiencies for the gas-phase SO2 and HNO3 using the cellulose membrane were 96% and 100%, respectively, and the collection efficiency of NH3 using the nylon membrane was 100%. The AIM-IC was compared with a collocated annular denuder sampling system (ADSS) and a Federal Reference Method (FRM) Partisol PM2.5 sampler. The correlation coefficients of SO4(2-) concentrations between the AIM-IC and ADSS and between the AIM-IC and the Partisol PM2.5 sampler were 0.98 and 0.95, respectively. The comparisons also showed no statistically significant difference between the measurement sets, suggesting that the AIM-IC measurements of the PM2.5 chemical composition are comparable to the ADSS and Partisol PM2.5 methods. NH3 concentration in the summer (mean±standard deviation, 1.9±0.7 µg m(-3)) was higher than in the winter (1.3±0.9 µg m(-3)). HNO3 and NO3- concentrations were generally low in the AOSR, and especially in the winter months. NH4+ (0.94±0.96 µg m(-3)) and SO4(2-) (0.58±0.93 µg m(-3)) were the major ionic species of PM2.5. Direct SO2 emissions from oil sands processing operations influenced ambient particulate NH4+ and SO4(2-) values, with hourly concentrations of NH4+ and SO4(2-) measured downwind (~30 km away from the stack) at 10 and 28 µg m(-3). During the regional forest fire event in 2011, high concentrations of NO3-, NH4+, HNO3, NH3, and PM2.5 were observed and the corresponding maximum hourly concentrations were 31, 15, 9.6, 89, and >450 (the upper limit of PM2.5 measurement) µg m(-3), suggesting the formation of NH4NO3.

IMPLICATIONS

The AOSR in Canada is one of the most scrutinized industrial regions in the developed world due to the extent of oil extraction activities. Because of this, it is important to accurately assess the effect of these operations on regional air quality. In this study, we compare a new analytical approach, AIM-IC, with more standard analytical approaches to understand how local anthropogenic and nonanthropogenic sources (e.g., forest fires) impact regional air quality. With this approach, we also better characterize PM2.5 composition and its precursor gases to understand secondary aerosol formation mechanisms and to better identify possible control techniques if needed.

Transverse approach between tunnel environment and corrosion: particulate matter in the Grand Mare tunnel

A tunnel-type semi-enclosed atmosphere is characterized by a higher particulate pollution than urban zones and highlights the particulate species having an impact on material degradation. Therefore, a transverse approach between air composition and its consequences upon longevity of materials is necessary, requiring a better knowledge of tunnel atmosphere and a better understanding of material degradation inside a tunnel for operating administration. The characterization of particulate matter collected inside a road tunnel in Rouen (France) allows us to set up the features of the particle characteristics of the real conditions of field exposure. Two sampling campaigns include analyses of organic and water-soluble ionic fractions. The current work shows that organic species, grouped into two sets derived primarily from engine exhaust and debris with wear particles resuspended by the traffic, are divided into two groups: a majority comprising n-alkanes, alkanoic acids, phthalates, ketones, and benzothiazole and a minority one composed of BTEX (benzene, toluene, ethylbenzene, and xylenes), polycyclic aromatic hydrocarbons (PAHs), fatty acid methyl esters (FAMEs), furans, phenols, and alkenes. As regards the water-soluble ionic fraction, the ionic species such as Cl(-), SO4(2-), CH3COO(-), HCOO(-), NO3(-), NH4+, and Na+ are involved in the degradation process. The inorganic particles (insoluble and slightly soluble), debris and wear particles, organic acids, and relative humidity play a key role and are important factors to consider in the degradation process.

Size mass distribution of water-soluble ionic species and gas conversion to sulfate and nitrate in particulate matter in southern Taiwan

A Micro-Orifice Uniform Deposition Impactor (MOUDI) and a Nano-MOUDI were employed to determine the size-segregated mass distributions of ambient particulate matter (PM) and water-soluble ionic species for particulate constituents. In addition, gas precursors, including HCl, HONO, HNO3, SO2, and NH3 gases, were analyzed by an annular denuder system. PM size mass distribution, mass concentration, and ionic species concentration were measured during the day and at night during episode and non-episode periods in winter and summer. Average total suspended particle (TSP) concentrations during episode days in winter were as high as 153 ± 33 μg/m(3), and PM mass concentrations in summer were as low as one-third of that in winter. Generally, PM concentration at night was higher than that in the daytime in southern Taiwan during the sampling periods. In winter during the episode periods, the size-segregated mass distribution of PM mass concentration was mostly in the 0.32-3.2-μm range, and the PM concentration increased significantly in the range of 0.32-3.2 μm at night. Ammonium, nitrate, and sulfate were the dominant water-soluble ionic species in PM, contributing 34-48% of TSP mass. High concentrations of ammonia (12.9-49 μg/m(3)) and SO2 (2.6-27 μg/m(3)) were observed in the gas precursors. The conversion ratio was high in the PM size range of 0.18-3.2 μm both during the day and at night in winter, and the conversion ratio of episode days was 20% higher than that of non-episode days. The conversion factor was high for both nitrogen and sulfur species at nighttime, especially on episode days.

Ammonia in the environment: from ancient times to the present

Recent research on atmospheric ammonia has made good progress in quantifying sources/sinks and environmental impacts. This paper reviews the achievements and places them in their historical context. It considers the role of ammonia in the development of agricultural science and air chemistry, showing how these arose out of foundations in 18th century chemistry and medieval alchemy, and then identifies the original environmental sources from which the ancients obtained ammonia. Ammonia is revealed as a compound of key human interest through the centuries, with a central role played by sal ammoniac in alchemy and the emergence of modern science. The review highlights how recent environmental research has emphasized volatilization sources of ammonia. Conversely, the historical records emphasize the role of high-temperature sources, including dung burning, coal burning, naturally burning coal seams and volcanoes. Present estimates of ammonia emissions from these sources are based on few measurements, which should be a future priority.

Size distributions of fine and ultrafine particles in the city of Strasbourg: correlation between number of particles and concentrations of NO(x) and SO(2) gases and some soluble ions concentration determination

An Electrical Low Pressure Impactor (ELPI) was used during spring and autumn 2003 in the centre of Strasbourg for the measurement of atmospheric aerosols size distribution. The concentration of NO(x) and SO(2) in air was simultaneously measured with specific analysers. Samples were collected in the range 0.007-10 microm in equivalent aerodynamic diameter size. Number distributions are representative of a pollution originating from urban traffic with a particle size distribution exhibiting a nucleation mode below 29 nm and an accumulation mode around 80 nm in size. A mean particle density equal to 39000+/-35000 total particles per cm(3) with a size ranging from 7 to 10 microm was obtained after a sampling period of 2 weeks in spring. About 86.9% of the number of particles have an aerodynamic diameter below 0.1 microm and 13.1% between 0.1 and 1 microm. Correlation coefficients between the number of particles impacted on each ELPI plate and gas concentrations (SO(2) and NO(x)) showed that the numbers of particles with diameter between 0.10 and 0.62 microm are highly related to the NO(x) concentration. This result indicates that particles are traffic induced since NO(x) is mainly emitted by cars as shown by measurements on various sites. Particles are less clearly correlated to the SO(2) concentration. Particle analysis on different ELPI plates for a sampling period of 2 weeks in autumn showed high level of soluble NO(3)(-), SO(4)(2-) and NH(4)(+) ions. Indeed, up to 90% b.w. of these three species were found in the particle range 0.1-1 microm. The formation of particulate NH(4)NO(3) is favoured by high NO(x) concentration, which induces the formation of gaseous HNO(3).

Particulate sulphate and nitrate in Southern England and Northern Ireland during 2002/3 and its formation in a photochemical trajectory model

Daily measurements of sulphate and nitrate are reported from Harwell in southern England and Belfast in Northern Ireland for the period 2002/3. When the higher percentiles are compared with the mean concentration, nitrate reveals considerably greater episodicity than either sulphate or PM(10) (measured by TEOM). A photochemical trajectory model using the Master Chemical Mechanism scheme has been used to predict daily concentrations of both nitrate and sulphate aerosol over the period March to August 2002 at the Belfast and Harwell sites. This has been carried out for daily samples using 72, 96 and 120 h air mass back trajectories obtained from both the British Atmospheric Data Centre and the HYSPLIT on-line service. Additionally, model simulations have been conducted for 5 trajectories generated through clustering of the trajectories for individual days. This reveals an under-prediction of the model associated particularly with trajectories originating from the European mainland. In general, the model performs reasonably well in simulating concentrations of both nitrate and sulphate, which is surprising given that the model does not account for processes requiring the presence of liquid water. This suggests that aqueous phase oxidation processes may not make a major contribution to airborne sulphate concentrations in the U.K. in the spring and summer months. It appears that inclusion of explicit ammonium nitrate formation chemistry may be essential to reliable prediction of episodic nitrate peaks.

A long-term study of oxides of nitrogen, sulphur dioxide, and ammonia for a port and harbor region in India

A long-term study of oxides of nitrogen (NOx), sulphur dioxide (SO2), and ammonia (NH3) has been performed in a port and harbor region in India from January 1997 to December 2000. Meteorological data was also collected to establish the correlation with gaseous pollutants concentrations. Monthly mean concentrations of NOx were in the range of 19.5-59.0 microg/m3 and were observed to be highest during winter season. Monthly mean concentrations of SO2 were in the range of 8.6-51.3 microg/m3 and were observed to be highest during winter season. The concentrations of SO2 increased gradually from 18.8 microg/m3 in 1997 to 33.3 microg/m3 in 2000. This may be attributed to the increase in port activities and ship traffic, which had an annual growth of about 15%. Monthly mean concentrations of NH3 were in the range of 87.1-235.1 microg/m3 and the maximum concentration was observed during post-monsoon season. It may be concluded that NOx and SO2 have their maximum values during winter season while NH3 has a maximum value during post-monsoon season. Statistical analysis was carried out for air pollutant data for the period 1997-2000 and correlation between gaseous pollutants (NOx, SO2, NH3) and meteorological parameters (temperature and wind speed) was estimated. NH3 was found to be weakly correlated with NOx (0.46), strongly correlated with SO2 (0.75) and negatively correlated with wind speed (-0.60). The highest correlation (0.87) was observed between SO2 and NOx because of common sources. A strong negative correlation was found between wind speed and gaseous pollutants. The above finding is also supported by monitoring results that when the wind velocity doubled, the concentrations of pollutants decreased sharply to about a half. Regression analysis showed that relationship among NOx, SO2, wind speed, and temperature was moderate to strong while that among NH3, wind speed, and temperature was poor. Hence regression equations could be developed for predicting NOx and SO2 concentrations.

Physico-chemical characterization of atmospheric aerosols in a rural area affected by the Aznalcollar toxic spill, south-west Spain during the soil reclamation activities

High levels of atmospheric contamination due to the re-suspension of pyrite particles from the mining waste slurry were recorded in the Guadiamar valley (the Guadiamar is a tributary of the Guadalquivir river) after the toxic spill of Aznalcóllar, north of the Doñana Natural Park (SW Spain). Major high-particulate events occurred during the extraction of the pyrite-rich mud layer, which covered an extensive area of the valley downstream of the confluence of the Agrio and Guadiamar rivers. This study deals with the monitoring of the ambient air quality at two stations near the village of Aznalcázar in the central part of the flooded area. Although the Spanish legal limit for atmospheric particles and lead in environmental air were not exceeded, high daily levels of total suspended particles (TSP) and of some elements with an environmental significance (As, Cd, Cu, Mn, Ni, Pb, Sn, Tl and Zn) were recorded at Aznalcázar and in the Guadiamar valley during soil reclamation (July-August 1998). Despite a progressive decrease in TSP levels through September-October 1998, background was higher than the levels for the May-June period. Evolution of levels for most of the elements studied showed a similar trend. The exceptions were copper, which was partially increased by other emission sources such as fumigation activities, and sodium, which remained at relatively constant levels during the study period because of its marine origin. The physico-chemical characterisation of the atmospheric particulates allowed us to determine the major grain size modes of the pyrite related elements and the solubility of the potentially toxic elements, and to identify the major particulate types present in the atmosphere in the area. Secondary and tertiary aromatic amines (i.e. alkyldiphenylamines and phenylcarbazoles, respectively) were identified in the suspended particles and in the vapour phase collected at the same station as the TSP samples. As some of these aromatic amines had been previously identified in the pyrite sludge, it is assumed that fine sludge particles containing aromatic amines were re-suspended in the atmosphere. The highest concentrations of aromatic amines in the particulate phase were recorded in August 1998 during the pyrite slurry extraction in the proximity of the Aznalcázar sampling site. Despite a sharp drop in the suspended particles of the aromatic amine concentrations, a significant concentration was detected in the vapour phase (< 1.2 mm) during autumn, probably because of longer residence time in the atmosphere. Although health hazards associated with the presence of these aromatic amines are unknown, their acute toxicity exceeded that of urban aerosols.

Deposition of atmospheric ammonia to moorlands

Micrometeorological methods were applied to measure fluxes of atmospheric ammonia (NH3) to moorlands. Measurements were made in a wide variety of surface conditions and included both Calluna vulgaris (L.) Hull and Eriophorum vaginatum L. dominated sites. NH3 was found to deposit rapidly to all the sites investigated, providing large deposition velocities (Vd, typically 10-40 mm s(-1)) and usually minimal surface resistances (rc). A small number of measurements were made in frozen conditions and suggest a possible exception to this pattern with mean rc of 50-200 s m(-1). The effect of vegetation drying was also investigated and a possible increase in rc observed, though this was small (< 10 s m(-1)). The results are interpreted in terms of the processes controlling exchange; it is shown that NH3 deposition is predominantly to the leaf surfaces and that the net NH3 compensation point approaches zero. Annual estimates show that dry deposition of NH3 is a major source of atmospheric nitrogen to moorland ecosystems. For two typical UK sites subject to background air concentrations, NH3 dry deposition is of similar magnitude to equivalent NH4+ inputs in wet deposition. In the vicinity of emission sources, NH3 dry deposition is expected to dominate inputs of atmospheric nitrogen.