Coal-fired Power Plant Plume Research Articles

Using drone soundings to study the impacts and compositions of plumes from a gigantic coal-fired power plant

The immense impacts of coal-fired power plant plumes on the atmospheric environment have caused great concern linked to climate and health issues. However, studies on the field observations of aerial plumes are relatively limited, mainly due to the lack of suitable plume observation tools and techniques. In this study, we use a multicopter unmanned aerial vehicle (UAV) sounding technique to study the influences of the aerial plumes of the world's fourth-largest coal-fired power plant on the atmospheric physical/chemical conditions and air quality. A set of species, including 106 volatile organic compounds (VOCs), CO, CO2, CH4, PM2.5, and O3, and meteorological variables of temperature (T), specific humidity (SH), and wind data, are collected by the UAV sounding technique. The results reveal that the large-scale plumes of the coal-fired power plant cause local temperature inversion and humidity changes, and even affect the dispersion of pollutants below. The chemical compositions of coal-fired power plant plumes are significantly different from those of another ubiquitous vehicular source. High fractions of ethane, ethene, and benzene and low fractions of n-butane and isopentane found in plumes could serve as the key features to help distinguish the influences of coal-fired power plant plumes from other pollution sources in a particular area. By taking the ratios of pollutants (e.g., PM2.5, CO, CH4, and VOCs) to CO2 in plumes and the CO2 emission amounts of the power plant into calculation, we enable the easy quantification of the specific pollutant emissions released from power plant plumes to the atmosphere. In summary, observation by using drone soundings dissecting the aerial plumes provides a new methodology that allows aerial plumes to be readily detected and characterized. Furthermore, the influences of the plumes on the atmospheric physical/chemical conditions and air quality can be assessed rather straightforwardly, which was not easily achievable in the past.

Limited impact of sulfate-driven chemistry on black carbon aerosol aging in power plant plumes

The aging of refractory black carbon (rBC) aerosol by sulfate-driven chemistry has been constrained in coal-fired power-plant plumes using the NOAA WP-3D research aircraft during the Southern Nexus (SENEX) study, which took place in the Southeastern US in June and July of 2013. A Single Particle Soot Photometer (SP2) determined the microphysical properties of rBC-containing particles including single-particle rBC mass and the presence and amount of internally-mixed non-rBC material, hereafter referred to as “coatings”. Most power-plant influenced air was associated with very slightly increased amounts of non-refractory material, likely sulfate internally mixed with the rBC, however this increase was statistically insignificant even after semi-Lagrangian exposure for up to 5 h. On average, the increase in coating thickness was 2 ± 4 nm for particles containing 3–5 fg rBC. Similarly, the number fraction of rBC-containing particles that could be identified as internally mixed was increased by plume chemistry by only 1.3 ± 1.3%. These direct measurements of microphysical aging of rBC-containing aerosol by power plant emissions constrain the enhancement of sulfate chemistry on both rBC’s column-integrated absorption optical depth, and rBC-containing aerosol’s ability to act as cloud condensation nuclei. Appling Mie and k -Kohler theories to the SP2 observations, permits the resulting effect on rBC ambient light-absorption to be capped at the 2–6% level.

A model-based analysis of SO2 and NO2 dynamics from coal-fired power plants under representative synoptic circulation types over the Iberian Peninsula

Emissions of SO2 and NO2 from coal-fired power plants are a significant source of air pollution. In order to typify the power plants' plumes dynamics and quantify their contribution to air quality, a comprehensive characterisation of seven coal-fired power plant plumes has been performed under six representative circulation types (CTs) identified by means of a synoptic classification over the Iberian Peninsula. The emission and the transport of SO2 and NO2 have been simulated with the CALIOPE air quality forecasting system that couples the HERMES emission model for Spain and WRF and CMAQ models. For the facilities located in continental and Atlantic areas (As Pontes, Aboño, and Compostilla) the synoptic advection controls pollutant transport, however for power plants located along the Mediterranean or over complex-terrains (Guardo, Andorra, Carboneras, and Los Barrios), plume dynamics are driven by a combination of synoptic and mesoscale mountain–valley and sea–land breezes. The contribution of power plants to surface concentration occurs mainly close to the source (<20km) related to a fumigation process when the emission injection takes place within the planetary boundary layer reaching up to 55μg SO2m−3 and 32μgNO2m−3. However, the SO2 and NO2 plumes can reach long distances (>250km from the sources) especially for CTs characterised by Atlantic advection.

Mercury speciation in a coal‐fired power plant plume: An aircraft‐based study of emissions from the 3640 MW Nanticoke Generating Station, Ontario, Canada

AbstractCoal‐fired power plants are one of the principal sources of mercury to the atmosphere. The form this mercury takes is the predominant factor determining its fate after emission. Recent ground‐level field and modeling studies suggest that oxidized mercury in stack emissions is converted into elemental mercury in the plume. We present here aircraft‐based plume mercury measurements taken by Environment Canada in 2000 at the Nanticoke Generating Station as part of the Health Canada Toxic Substances Research Initiative Metals in the Environment Research Network. Although the average mercury speciation observed in the Nanticoke plume (82% Hg0, 13% Hg(II)(g), 5% Hg(P), by mass) appears to be distinct from the average mercury speciation in the Nanticoke stacks (53% Hg0, 43% Hg(II)(g), 4% Hg(P)), we find that the in‐plume elemental mercury concentrations as a whole can be explained by plume dilution after emission. The discrepancy between in‐stack and in‐plume Hg(II) concentrations is statistically significant, yet is not associated with a transformation of Hg(II) to Hg0. Sampling biases associated with the differing techniques used to measure Hg(II) in‐stack and in‐plume may reconcile the concentration discrepancy without invoking novel chemical reactions or physical processes. Although the mercury speciation of the Nanticoke plume influences local mercury deposition, the majority of the mercury emitted is transported out of the surrounding area.

The effect of coal-fired power-plant SO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; and NO&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt; control technologies on aerosol nucleation in the source plumes

Abstract. Nucleation in coal-fired power-plant plumes can greatly contribute to particle number concentrations near source regions. The changing emissions rates of SO2 and NOx due to pollution-control technologies over recent decades may have had a significant effect on aerosol formation and growth in the plumes with ultimate implications for climate and human health. We use the System for Atmospheric Modeling (SAM) large-eddy simulation model with the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm to model the nucleation in plumes of coal-fired plants. We test a range of cases with varying emissions to simulate the implementation of emissions-control technologies between 1997 and 2010. We start by simulating the W. A. Parish power plant (near Houston, TX) during this time period, when NOx emissions were reduced by ~90% and SO2 emissions decreased by ~30%. Increases in plume OH (due to the reduced NOx) produced enhanced SO2 oxidation and an order-of-magnitude increase in particle nucleation in the plume despite the reduction in SO2 emissions. These results suggest that NOx emissions could strongly regulate particle nucleation and growth in power-plant plumes. Next, we test a range of cases with varying emissions to simulate the implementation of SO2 and NOx emissions-control technologies. Particle formation generally increases with SO2 emission, while NOx shows two different regimes: increasing particle formation with increasing NOx under low-NOx emissions and decreasing particle formation with increasing NOx under high-NOx emissions. Next, we compare model results with airborne measurements made in the W. A. Parish power-plant plume in 2000 and 2006, confirming the importance of NOx emissions on new particle formation and highlighting the substantial effect of background aerosol loadings on this process (the more polluted background of the 2006 case caused more than an order-of-magnitude reduction in particle formation in the plume compared to the cleaner test day in 2000). Finally, we calculate particle-formation statistics of 330 coal-fired power plants in the US in 1997 and 2010, and the model results show a median decrease of 19% in particle formation rates from 1997 to 2010 (whereas the W. A. Parish case study showed an increase). Thus, the US power plants, on average, show a different result than was found for the W. A. Parish plant specifically, and it shows that the strong NOx controls (90% reduction) implemented at the W. A. Parish plant (with relatively weak SO2 emissions reductions, 30%) are not representative of most power plants in the US during the past 15 yr. These results suggest that there may be important climate implications of power-plant controls due to changes in plume chemistry and microphysics, but the magnitude and sign of the aerosol changes depend greatly on the relative reductions in NOx and SO2 emissions in each plant. More extensive plume measurements for a range of emissions of SO2 and NOx and in varying background aerosol conditions are needed, however, to better quantify these effects.

Nucleation and growth of sulfate aerosol in coal-fired power plant plumes: sensitivity to background aerosol and meteorology

Abstract. New-particle formation in the plumes of coal-fired power plants and other anthropogenic sulfur sources may be an important source of particles in the atmosphere. It remains unclear, however, how best to reproduce this formation in global and regional aerosol models with grid-box lengths that are 10s of kilometers and larger. The predictive power of these models is thus limited by the resultant uncertainties in aerosol size distributions. In this paper, we focus on sub-grid sulfate aerosol processes within coal-fired power plant plumes: the sub-grid oxidation of SO2 with condensation of H2SO4 onto newly-formed and pre-existing particles. We have developed a modeling framework with aerosol microphysics in the System for Atmospheric Modelling (SAM), a Large-Eddy Simulation/Cloud-Resolving Model (LES/CRM). The model is evaluated against aircraft observations of new-particle formation in two different power-plant plumes and reproduces the major features of the observations. We show how the downwind plume aerosols can be greatly modified by both meteorological and background aerosol conditions. In general, new-particle formation and growth is greatly reduced during polluted conditions due to the large pre-existing aerosol surface area for H2SO4 condensation and particle coagulation. The new-particle formation and growth rates are also a strong function of the amount of sunlight and NOx since both control OH concentrations. The results of this study highlight the importance for improved sub-grid particle formation schemes in regional and global aerosol models.

Assessment of the UV camera sulfur dioxide retrieval for point source plumes

Digital cameras, sensitive to specific regions of the ultra-violet (UV) spectrum, have been employed for quantifying sulfur dioxide (SO 2) emissions in recent years. The instruments make use of the selective absorption of UV light by SO 2 molecules to determine pathlength concentration. Many monitoring advantages are gained by using this technique, but the accuracy and limitations have not been thoroughly investigated. The effect of some user-controlled parameters, including image exposure duration, the diameter of the lens aperture, the frequency of calibration cell imaging, and the use of the single or paired bandpass filters, have not yet been addressed. In order to clarify methodological consequences and quantify accuracy, laboratory and field experiments were conducted. Images were collected of calibration cells under varying observational conditions, and our conclusions provide guidance for enhanced image collection. Results indicate that the calibration cell response is reliably linear below 1500 ppm m, but that the response is significantly affected by changing light conditions. Exposure durations that produced maximum image digital numbers above 32 500 counts can reduce noise in plume images. Sulfur dioxide retrieval results from a coal-fired power plant plume were compared to direct sampling measurements and the results indicate that the accuracy of the UV camera retrieval method is within the range of current spectrometric methods.

Mercury Speciation in Coal-fired Power Plant Plumes Observed at Three Surface Sites in the Southeastern U.S.

Elemental Hg (Hg0), reactive gaseous Hg (RGM) and fine particulate Hg (Hgp) were measured intermittently at three sites in the southeastern U.S. from June 2001 through November 2004. Simultaneous measurements of SO2 and NOy were used to identify plumes from coal fired power plants (CFPPs). Emission signatures and back trajectories were used to identity specific CFPPs, and to compare observed (i.e., at the site) versus expected (i.e., at the stack) Hg speciation. Results for 41 precipitation-free plume events show that observed RGM:SO2 is substantially lower (by a factor of 2-4) than expected RGM:SO2. Hgp represented 2%, or less, of total-Hg in CFPP plumes, in general agreement with emission estimates. Results for 21 events, where both RGM and Hg0 could be estimated, show that total-Hg (i.e., RGM + Hg0) was essentially conserved from the point of emission to the site, and that Hg0 was the dominant form (average 84%). Emission estimates, based on coal analyses and the EPRI-ICR Hg speciation model, indicate that Hg0 should represent about 42% of Hg in the observed plumes. Possible explanations for these differences include, but are not limited to, in-plume reduction of RGM to Hg0, measurement error, errors in emission estimates, and depositional losses. Further work is needed to confirm these results and to determine if they apply to CFPPs in general, or the limited set of observed CFPPs.

Modeling Mercury in Power Plant Plumes

Measurements of speciated mercury (Hg) downwind of coal-fired power plants suggest that the Hg(II)/(Hg0 + HgII) ratio (where HgII is divalent gaseous Hg and Hg0 is elemental Hg) decreases significantly between the point of emission and the downwind ground-level measurement site, but that the SO2/(Hg0 + HgII) ratio is conserved. We simulated nine power plant plume events with the Reactive & Optics Model of Emissions (ROME), a reactive plume model that includes a comprehensive treatment of plume dispersion, transformation, and deposition. The model simulations fail to reproduce such a depletion in HgII. A sensitivity study of the impact of the HgII dry deposition velocity shows that a difference in dry deposition alone cannot explain the disparity. Similarly, a sensitivity study of the impact of cloud chemistry on results shows that the effect of clouds on Hg chemistry has only minimal impact. Possible explanations include HgII reduction to Hg0 in the plume, rapid reduction of HgII to Hg0 on ground surfaces, and/or an overestimation of the HgII fraction in the power plant emissions. We propose that a chemical reaction not included in current models of atmospheric mercury reduces HgII to Hg0 in coal-fired power plant plumes. The incorporation of two possible reduction pathways for HgII (pseudo-first-order decay and reaction with SO2) shows better agreement between the model simulations and the ambient measurements. These potential HgII to Hg0 reactions need to be studied in the laboratory to investigate this hypothesis. Because the speciation of Hg has a significant effect on Hg deposition, models of the fate and transport of atmospheric Hg may need to be modified to account for the reduction of HgII in coal-fired power plant plumes if such a reaction is confirmed in further experimental investigations.

Electrochemical detection of mercury adsorbed from flowing gas samples on porous carbon electrodes

AbstractThe adsorption of mercury from flowing gas streams onto reticulated vitreous carbon (RVC) is combined with postadsorption stripping voltammetric determination. This novel analytical method achieves gas stream detection limits of 1.1 μg/m3 for unmodified RVC electrodes at 52°C and 1.8 μg/m3 for modified RVC electrodes at 25°C. Due to the unique features of this detection technique, it is possible and feasible that it could be applied for mercury analysis in coal fired power plant plumes and waste incinerator stacks.

Airborne streaker sampling for PIXE analysis

Ground based aerosol sampling has inherent limitations for understanding atmospheric transport and dynamics. Sampling from aircraft platforms has limitations on the sampling time and quantity of aerosol mass that can be collected, especially if multiple samples per flight are required to allow for vertical or horizontal resolution. A modification of Florida State University circular streaker sampler has been made to enable aerosol samples to be collected isokinetically from a Lear jet. The samples are matched for analysis by PIXE or scanning electron microprobe. Features of the sampler include: a two stage isokinetic inlet matched to aircraft speeds of 550 km/h; remote computer control of the wing tip mounted sampler; up to twenty samples per flight on a single circular disk. Preliminary tests with the sampler are described, involving sampling of a coal fired power plant plume, and calibration of PIXE elemental concentrations against particle number density measured simultaneously with a forward scattering probe.

Development and Testing of Short Response Time SO2, NOXand O3Analyzers

As part of research carried out on the transformations of pollutants In coal-fired power plant plumes, we have developed and tested SO2, NO X , and O3 analyzers with a short response time of about 4 seconds. These analyzers, tested In the laboratory and on board an aircraft In plumes, exhibit good linearity of response as well as acceptable background noise. The background noise can be further reduced by appropriate signal processing. These short response time analyzers provide a valuable tool for plume studies, allowing a precise mapping of polluted areas and of the corresponding sources

Infrared optical properties of a coal-fired power plant plume

Infrared measurements in the 8–14-μm spectral region were made of two coal-fired power plant plumes and area haze in the Four Corners region of New Mexico from 1 to 7 Nov. 1980. The layer transmittance, optical depth, and volume extinction coefficient derived from measurements on four nonconsecutive days show the effects of the plumes on the IR optical properties of the atmosphere. The average contribution of the plume alone to the IR extinction coefficient was 74% at the Four Corners plant; the background haze contributed 7–11%. More efficient particulate emission control at the San Juan power plant reduced the average contribution of its plume to 57% of the extinction coefficient. The haze contributed an average of 16%. The results show an increase with time of the haze bulk extinction coefficient during a persistent anticyclonic synoptic situation. Extinction coefficients of the haze showed a linearity with particulate loading, which led to estimates of IR volume extinctions of the free troposphere from aerosol measurements.

Sulfate aerosol production in coal-fired power plant plumes

As part of the Winter Study of Power Plant Effects (WISPE), air chemistry measurements were made in the plumes of the coal-burning Bowen Electric Generating Plant in northwest Georgia. Ten flights were made using the instrumented Pennsylvania State University research aircraft. Measurements included condensation nuclei concentration, aerosol size distribution and sulfur dioxide concentration. Quantitative chemical analysis of impactor-collected sulfate particles, together with these measurements, allowed for calculation of SO 2-sulfate conversion rates. In addition, nuclei concentrations were analyzed as a function of plume age and position in the plume. SO 2 conversion rates and nuclei production were examined for dependence on various meteorological parameters in order to better understand the mechanisms of sulfate aerosol production. A comparison was made with the findings of a similar study conducted at the Keystone Power Plant in southwestern Pennsylvania. The conversion rates of SO 2 to SO 4 2− were under 0.2 % h −1 with the exception of one flight for which a rate of 2.3% h −1 was calculated. Nuclei production was found to be dependent on both solar flux and plume dilution. Evidence of enhanced nuclei production at plume borders was also found. This implies that entrainment of photochemically produced species from the surrounding air mass is responsible for gas-phase oxidation which results in nuclei production.

The Nanticoke shoreline diffusion experiment, June 1978—IV. A. Oxidation of sulphur dioxide in a power plant plume. B. Ambient concentrations and transport of sulphur dioxide, particulate sulphate and nitrate, and ozone

The oxidation rate of sulphur dioxide to sulphate in the Nanticoke coal-fired power plant plume was measured at distances of 3–43 km during fumigation conditions in June 1978; the average rate was 4 % h −1. Airborne measurement of SO 2, O 3, b scat , paniculate sulphate and paniculate nitrate were made over Lake Erie during the same period. These were compared to 4-day back-trajectories: south to south-westerly trajectories associated with the western or back side of high pressure systems led to high concentrations and the north to north-westerly trajectories associated with the eastern or front side of high pressure systems correlated with low pollutant concentrations.

Elemental composition of size-fractionated aerosols associated with a coal-fired power plant plume and background

Elemental composition of size-fractionated aerosols associated with a coal-fired power plant plume and background

Gas-to-particle conversion of sulfur in power plant plumes—I. Parametrization of the conversion rate for dry, moderately polluted ambient conditions

Our previous work has shown that, under relatively dry summertime conditions (r.h. < 75 %), the conversion rate k 1 (%h −1) of SO 2 to aerosol sulfates in the coal-fired Labadie power plant plume near St. Louis is largely governed by photochemically driven gas-phase reactions involving primary SO 2 and NO x and reactive species entrained from the background. Sunlight, plume dilution and background reactivity are then the principal factors influencing sulfate as well as ozone formation in the plume. In this paper, the aircraft data of five days of Labadie plume transport (Project MISTT 1976) and five days of transport of TVA's coal-fired Cumberland and Johnsonville power plants (Project STATE/Tennessee Plume Study 1978) are analyzed to formulate and test a new parametrization of the conversion rate of sulfur under “dry” summertime conditions (r.h. < 75 %). The parametrization, given by k t = (0.03 ± 0.01) ( RΔz p O 3), is found to provide a good match to the previously published observed conversion rates on both 9 and 18 July, 1976, for daytime Labadie plume transport up to 200km ( R = solar radiation, Δz p = vertical spread of plume, O 3 = background ozone; hourly-averaged data of St. Louis RAPS). A test of this parametrization against the observed rates in the ten days of MISTT and STATE data of all three plumes yielded very satisfying verification for all data collected under “dry”, cloud-free conditions. Under such conditions, 90 % or more of the conversion is believed to occur by the gas-phase mechanism. The parametrization does not apply to liquid phase and heterogeneous conversions in more humid conditions. Also, it does not have the spatial resolution to distinguish between plume core rates and the much enhanced rates in plume edges. Examples of local conversion rates up to 10 % h −1 with liquid phase reactions and 7.5 % h −1 in plume edges are also presented. Otherwise, the conversion rates are generally under 3% h −1. The new parametrization is consistent with our present understanding of the pertinent physics and chemistry of gas-phase oxidation of SO 2 under moderately polluted conditions. It is simple and requires input data which are relatively routinely monitored. This chemical submodule is suitable for use in long range transport-transformation models. Diurnal and seasonal patterns of the parametrized conversion rate for the St. Louis region are given as examples. Further testing of this parametrization against power plant plume data collected at locations other than in the U.S. Midwest and during seasons other than summer, is recommended. The validity of the parametrization for oil-fired power plant plumes and for smelter plumes also remains to be tested.

Sulfate formation in point source plumes: A review of recent field studies

Data in twelve power plant and smelter plumes reported by eight different organizations have been reviewed in an attempt to establish the existence of recognizable patterns concerning the extent and rates of sulfate formation. The data reviewed here were collected in Australia, Canada and the U.S., during warm as well as cold seasons, and during day and night. The primary variables examined and compared are S p / S T , the paniculate fraction of excess sulfur sampled in the plume, and the corresponding plume age. The variation of the extent of sulfate formation ( S p / S T ) is also examined in terms of plume exposure to solar radiation dose during transport. In spite of wide geographical, seasonal, background and source variations, a distinct difference is observed in day and night sulfate formation. During the daytime, there exists a substantial variability in sulfate formation rates (typically 0–5% h −1) and extent (typically up to 25%) for any given physical plume age. This variability is significantly less for plumes with similar exposure to sunlight dose, showing that environmental factors linked to solar radiation strongly influence the rate and extent of sulfate formation in point-source plumes. The diurnal and seasonal co-variance of all insolation-related factors makes it difficult to distinguish the roles of specific environmental factors or conversion mechanisms. Night-time data show that S p / S T seldom exceeds 3% even after 5–10 h of plume transport. A surprising result is observed related to geographical variability of the conversion rate. Except in the case of the data of the Navajo coal-fired power plant plume collected as part of the VISTTA study, all other data fall within an identifiable envelope ranging over 15–30% sulfate formation ( S p / S T ) corresponding to solar dose equivalent to one July day in St. Louis. The Navajo data yield about an order of magnitude lower conversion. Evidently, factors other than those related to insolation are also important.

The chemistry, aerosol physics, and optical properties of a western coal-fired power plant plume

Data obtained from the airborne measurements in the plume of the Navajo Generating Station (NGS) in June–July and December 1979 as part of the EPA project VISTTA are reported. Source test and airborne data for the ratios SO 2/NO x, particulates/SO 2 and the size distribution of the primary particles agreed to within the variability of the emissions. NO 2 concentrations in the plume were in agreement with the photostationary steady state relations; there was no evidence for additional oxidant formation at distances up to 115 km. The formation of sulfate and nitric acid was strongly suppressed in the concentrated plume, where ozone is depleted. Sulfate conversions of less than 0.1 % were typically observed for plume ages of 2 to 3 h in the morning sunlight. The highest SO 2 oxidation rates observed in the dilute plume were 0.8%h in the summer between 59 and 89 km in the late morning and 0.2 %/h in the winter between 93 and 108 km in the afternoon. Nitric acid was always observed in the plume and the rate of conversion of NO x to nitric acid was 3 to 10 times the rate of conversion of SO 2 to sulfate. Ammonia concentrations were adequate to neutralize the secondary sulfate, but not to saturate the plume with ammonium nitrate. Particulate nitrates were not observed. New aerosol was reliably detected only in the 0.01 to 0.1 μm size range, which is ineffective at scattering light. Growth of particles larger than 0.1 μm was hard to detect in the presence of the variations in the background aerosol concentration. The emissions which affect the plume visibility are NO x and fly ash, which was predominantly in the 2–7 μm size range. Secondary aerosol formation in the NGS plume can be neglected in visibility models for distances up to 100km, but significant amounts of NO x were removed by oxidation. On the average, extinction due to fly ash and NO 2 were equal for blue light for 7% conversion of NO x to NO 2, and for green light at 26 % conversion. Fly ash always dominated extinction in the red. Telephotometer sight path flight data were obtained for plume visibility model validation.

Formation of Sulfate Particles in the Plume of the Four Corners Power Plant

Abstract On 6 June 1978, the Four Corners coal-fired power plant plume near Farmington, New Mexico, was sampled with an instrumented twin-engine Aero-commander 680E, up to 90 km downwind from the source. Measurements consisted of aerosol size distribution, condensation nuclei, various gases, individual particle chemistry using electron microscopy techniques and meteorological parameters. A substantial formation of condensation nuclei took place downwind of the plant at a rate of 1.3 × 1016 s−1 in the first 0.3 h, 3.3 × 1017 s−1 up to 2.5 h, and 8 × 1017 s−1 in the 2.5–12.5 h plume travel time. The corresponding conversion rates were 0.15, 0.5 and 0.3% h−1, respectively. The conversion rate due to oxidation of SO2 on surfaces of fly ash particles was negligible. Dry removal of particles was very high and reached an estimated maximum of 36% during the first 2.5 h probably due to partial impingements of the plume to the ground. Analysis of individual particles collected on nuclepore filters using a scanning ...