Size Distribution Of Sulfate Research Articles

Loadings, Size Distributions, and Sources of Compound Classes in Los Angeles Aerosol

AbstractA low-pressure impactor, equipped with ZnSe impaction substrates, was used to sample ambient Los Angeles aerosol. This new approach to aerosol characterization provides size-resolved data on the loadings of organic and inorganic compound classes. The loadings and size distributions of sulfate, nitrate, aliphatic carbon, carbonyl, and organonitrate groups were determined and were used to investigate the sources of these aerosol components. The source resolution studies revealed that secondary aerosol formation processes contribute significantly to the loadings of several aerosol compound classes.

05 O 04 Spatial variation and size distribution of sulfate and strong aerosol acidity in a large metropolitan area

05 O 04 Spatial variation and size distribution of sulfate and strong aerosol acidity in a large metropolitan area

Particle size distributions in Arctic polar stratospheric clouds, growth and freezing of sulfuric acid droplets, and implications for cloud formation

Particle size and volume measurements obtained with the forward scattering spectrometer probe (FSSP), model 300 during January and February 1989 in the Airborne Arctic Stratospheric Experiment are presented and used to study processes important in the formation and growth of polar stratospheric cloud (PSC) particles. Comparisons of the observations with expected sulfuric acid droplet deliquescence suggest that in the Arctic a major fraction of the sulfuric acid droplets remain liquid until temperatures at least as low as 193 K. Arguments are presented to suggest that homogeneous freezing of the sulfuric acid droplets might occur near 190 K and might play a role in the formation of PSCs. The first suggestion of nitric acid trihydrate (NAT) particles appears near saturation ratios of HNO3 with respect to NAT of 1 (about 195 K) as an enhancement, of the large particles on the tail of the sulfuric acid droplet size distribution. The major increases in number and volume indicative of the main body of the NAT cloud are not seen in these Arctic investigations until 191 to 192 K, which corresponds to an apparent saturation ratio of HNO3 with respect to NAT of about 10, unlike the Antarctic where clouds were encountered at saturation ratios near 1. A decrease in the number of particles was observed in regions in which the airmass was denitrified, i.e. NOy, the sum of all reactive nitrogen species, was reduced. This was especially true for the larger particles on the upper tail of the sulfate size distribution. The loss of these largest particles supports the idea that denitrification may be the result of the preferential nucleation and growth of NAT on only the largest sulfate particles, which then sediment out of the airmass.

Particulate Characteristics and Visual Effects of the Atmosphere at Research Triangle Park

During a 38-day period in the fall of 1987 a wide range in the visual quality of the atmosphere at Research Triangle Park, North Carolina was observed. Throughout the period, the light scalier coefficient; SO2, NO2, and O3 concentrations; temperature; relative humidity; and radiation Intensity of the atmosphere were continuously monitored. Additionally, 60 filter samples were intermittently collected with two dichotomous (coarse and fine particle) size-selective samplers. The dichotomous samplers were operated concurrently to obtain samples on Teflon and quartz filters for different analyses. Also collected were six impactor samples for sulfate size distribution analysis. At selected times during the study, long-path measurements were made of the atmospheric extinction coefficient and the extinction of contrast by the atmosphere. The primary results were as follows: (1) The average light scatter coefficient to fine particle mass ratio was 4.55 m2/g, and this ratio varied from a Eow of around 3 ma/g when t...

Regional size distributions of sulfate and nitrate in the tokyo metropolitan area in summer

Atmospheric sulfate and nitrate were characterized through the measurement of their size distributions by an Andersen sampler. The experiments were performed in the Tokyo metropolitan area in the summer. The sulfate was found to be distributed in a bimodal form with a small peak in the coarse particle range and a dominant peak in the fine particle range. The peak in the coarse particle range decreased with the distance inland and was considered to be derived from seasalt and road dust. The peak in the fine panicle range did not change so markedly with respect to the distance from the coast and was considered to be derived from the slow gas-to-particle conversion of SO 2. On the other hand, nitrate showed a size distribution with a dominant peak in the coarse particle range and a small peak in the fine particle range. The peak in the coarse particle range again decreased with the distance from the coast and was shown to consist of nonvolatile NaNO 3 which was derived from seasalt and NO 2 HNO 3 . The peak in the fine particle range was shown to be NH 4NO 3, and its level was very low because of its volatility at ambient temperatures during the summer sampling period.

The physical characteristics of sulfur aerosols

A review of the physical characteristics of sulfur-containing aerosols, with respect to size distribution of the physical distributions, sulfur distributions, distribution modal characteristics, nuclei formation rates, aerosol growth characteristics, and in situ measurement, has been made. Physical size distributions can be characterized well by a trimodal model consisting of three additive lognormal distributions. When atmospheric physical aerosol size distributions are characterized by the trimodal model, the following typical modal parameters are observed: 1. 1. Nuclei mode — geometric mean size by volume, DGV a from 0.015 to 0.04 μm, σ gn , = 1.6, nuclei mode volumes from 0.0005 over the remote oceans to 9μm 3 cm −3 on an urban freeway. 2. 2. Accumulation mode — geometric mean size by volume, DGV a, from 0.15 to 0.5μm, σ gn = 1.6–2.2 and mode volume concentrations from 1 for very clean marine or continental backgrounds to as high as 300μm 3cm −3 under very polluted conditions in urban areas. 3. 3. Coarse panicle mode — geometric mean size by volume, DGV a, from 5 to 30 μm, σ gn , = 2–3. and mode volume concentrations from 2 to 1000 μm 3 cm −3. It has also been concluded that the fine particles ( D p < 2 μm) are essentially independent in formation, transformation and removal from the coarse particles ( D p > 2 μm). Modal characterization of impactor-measured sulfate size distributions from the literature shows that the sulfate is nearly all in the accumulation mode and has the same size distribution as the physical accumulation mode distribution. Average sulfate aerodynamic geometric mean dia. was found to be 0.48 ± 0.1 μm (0.37 ± 0.1 μm vol. dia). and ν = 2.00 ± 0.29. Concentrations range from a low of about 0.04 μg m −3 over the remote oceans to over 80μm −3 under polluted conditions over the continents. Review of the data on nucleation in smog chambers and in the atmosphere suggests that when SO 2 is present, SO 2-to-aerosol conversion dominates the Aitken nuclei count and, indirectly, through coagulation and condensation, the accumulation mode size and concentration. There are indications that nucleation is ubiquitous in the atmosphere, ranging from values as low as 2 cm −3 h −1' over the clean remote oceans to a high of 6 × 10 6 cm −3 h −1 ' in a power plant plume under sunny conditions. There is considerable theoretical and experimental evidence that even if most of the mass for the condensational growth of the accumulation mode comes from hydrocarbon conversion, sulfur conversion provides most of the nuclei.

Nitrate formation in atmospheric aerosols

Equilibrium nitrate levels in aqueous solution in the presence of sodium chloride, nitric oxide, nitrogen dioxide, sulfur dioxide, carbon dioxide, ammonia, and sulfuric acid are calculated. Nitrate levels in solution are of the order of those observed in the atmosphere when the gaseous concentrations are at typical urban levels. Sulfate levels in such solutions are predicted to be relatively low in the absence of oxidation catalysts. When sulfate formation is assumed to occur by gas-phase oxidation of sulfur dioxide to sulfuric acid followed by absorption of the sulfuric acid in aerosols, predicted nitrate and sulfate size distributions are in qualitative agreement with those observed in the atmosphere.

Concentration and particle size distribution of particulate emissions in automobile exhaust

Particulate components in hot, concentrated automobile exhaust and in cooled, diluted exhaust were fractionated and collected with cascade impactors; analyses were made for sulfate, nitrate, chloride, and water-soluble and water-insoluble lead. All components analyzed were contained in particles predominantly submicron in diameter. About 95 per cent of total lead was associated with particles having aerodynamic diameters below 0.5 μm. The particle size distributions of sulfate and nitrate were dependent on engine operating conditions, the particle size decreasing with increasing road speed and exhaust temperature. Photoirradiation produced an increase in the concentrations of water-soluble lead, sulfate, nitrate, and chloride particulate but a decrease in the average particle size of sulfate, nitrate, and chloride. After photoirradiation nearly all chloride was in the particle size range below 1 μm dia. Two mechanisms, both based on photochemical transformations of lead compounds, are suggested as explanations for a relatively lower accumulation of lead in the bones of mice exposed to irradiated, as compared to nonirradiated, exhaust.

Influence of some atmospheric variables on the concentration and particle size distribution of sulfate in urban air

Variations in the particle size distribution and concentration of atmospheric sulfate during a week in each of four cities were assessed with regard to the influence of such factors as location, humidity, sulfur dioxide level and time of day. Average sulfate mass median equivalent diameters (MMD) in Cincinnati, Chicago and Fairfax (Ohio) were nearly the same (0.42 μ) despite large differences in sulfate concentration and heterodispersity. A higher MMD (0.66 μ) in downtown Philadelphia was at least partly attributable to the presence of dust generated by road construction near the sampling site. Sulfate MMD generally increased with increasing relative humidity, whereas sulfate concentration was more closely correlated with absolute humidity except when SO 2 levels exceeded 3 pphm. Periodic variations in the sulfate parameters at the different locations were characterized by the lack of a consistent pattern and could not be explained on the basis of humidity changes alone.