Dust-laden Air Research Articles

Research dedusting efficiency of the inertial hub with adjustable parameters

Production of construction materials every year production increases, thus increasing emissions pollutants into the atmosphere subjected to cleaning. At the enterprises of building materials production equipment becoming outdated both morally and physically exhausted their useful life. Technological design standards in the operation of purification equipment has undergone a number of changes. There are a large number of works devoted to the theory of cyclone separation. They examined calculation method and to determine the minimum size of particles is separated completely from the air stream in a cyclone. In theory, the high efficiency cyclones are relatively small separation of particles from the air stream. The experiments show that certain fractions of full capture occurs from the cyclones and out relatively large particles. Designed dust device hubs. They capture dust particles with low specific density and smaller than 5–10 microns. Rational use of hubs is achieved in the aspiration systems high performance. They are placed in front of or between the filter and the cyclone filter. Hub much reduces the amount of dust-laden air directed onto a thin cleaning. This reduces energy consumption for manufacturing as a whole, as well as, due to a possible decrease in performance fine filters, reducing their initial cost, metal consumption, maintenance costs and reduce the area occupied by them.

Vertical Variation of Optical Properties of Mixed Asian Dust/Pollution Plumes According to Pathway of Airmass Transport Over East Asia

We use five years (2009 – 2013) of multiwavelength Raman lidar measurements at Gwangju, Korea (35.10° N, 126.53° E) for the identification of changes of optical properties of East Asian dust in dependence of its transport path over China. Profiles of backscatter and extinction coefficients, lidar ratios, and backscatter-related Angstrom exponents (wavelength pair 355/532nm) were measured at Gwangju. Linear particle depolarization ratios were used to identify East Asian dust layers. We used backward trajectory modelling to identify the pathway and the vertical position of dust-laden air masses over China during long-range transport. Most cases of Asian dust events can be described by the emission of dust in desert areas and subsequent transport over highly polluted regions of China. The Asian dust plumes could be categorized into two classes according to the height above ground in which these plumes were transported: (I) the dust layers passed over China at high altitude levels until arrival over Gwangju, and (II) the Asian dust layers were transported near the surface and the lower troposphere over industrialized areas before they arrived over Gwangju. We find that the optical characteristics of these mixed Asian dust layers over Gwangju differ in dependence of their vertical position above ground over China and the change of height above ground during transport. The mean linear particle depolarization ratio was 0.21±0.06 (at 532 nm), the mean lidar ratios were 52±7 sr at 355 nm and 53±8 sr at 532 nm, and the mean Angstrom exponent was 0.74±0.31 in case I. In contrast, plumes transported at lower altitudes (case II) showed low depolarization ratios, and higher lidar ratio and Angstrom exponents. The mean linear particle depolarization ratio was 0.13 ± 0.04, the mean lidar ratios were 63±9 sr at 355 nm and 62±8 sr at 532 nm, respectively, and the mean Angstrom exponent was 0.98±0.51. These numbers show that the optical characteristics of mixed Asian plumes are more similar to optical characteristics of urban pollution.

Vertical variation of optical properties of mixed Asian dust/pollution plumes according to pathway of air mass transport over East Asia

Abstract. We use five years (2009–2013) of multiwavelength Raman lidar measurements at Gwangju, South Korea (35.10° N, 126.53° E) for the identification of changes of optical properties of East Asian dust depending on its transport path over China. Profiles of backscatter and extinction coefficients, lidar ratios, and backscatter-related Ångström exponents (wavelength pair 355/532 nm) were measured at Gwangju. Linear particle depolarization ratios were used to identify East Asian dust layers. We used backward trajectory modeling to identify the pathway and the vertical position of dust-laden air masses over China during long-range transport. Most cases of Asian dust events can be described by the emission of dust in desert areas and subsequent transport over highly polluted regions of China. The Asian dust plumes could be categorized into two classes according to the height above ground at which these plumes were transported: (case I) the dust layers passed over China at high altitude levels (> 3 km) until arrival over Gwangju, and (case II) the Asian dust layers were transported near the surface and within the lower troposphere (< 3 km) over industrialized areas before they arrived over Gwangju. We find that the optical characteristics of these mixed Asian dust layers over Gwangju differ depending on their vertical position above ground over China and the change of height above ground during transport. The mean linear particle depolarization ratio was 0.21 ± 0.06 (at 532 nm), the mean lidar ratios were 52 ± 7 sr at 355 nm and 53 ± 8 sr at 532 nm, and the mean Ångström exponent was 0.74 ± 0.31 for case I. In contrast, plumes transported at lower altitudes (case II) showed low depolarization ratios (0.13 ± 0.04 at 532 nm), and higher lidar ratio (63 ± 9 sr at 355 nm and 62 ± 8 sr at 532 nm) and Ångström exponents (0.98 ± 0.51). These numbers show that the optical characteristics of mixed Asian plumes are more similar to optical characteristics of urban pollution. We find a decrease of the linear depolarization ratio of the mixed dust/pollution plume depending on transport time if the pollution layer traveled over China at low heights, i.e., below approximately 3 km above ground. In contrast, we do not find such a trend if the dust plumes traveled at heights above 3 km over China. We need a longer time series of lidar measurements in order to determine in a quantitative way the change of optical properties of dust with transport time.

Dust plume formation in the free troposphere and aerosol size distribution during the Saharan Mineral Dust Experiment in North Africa

Dust particles mixed in the free troposphere have longer lifetimes than airborne particles near the surface. Their cumulative radiative impact on earth's meteorological processes and climate might be significant despite their relatively small contribution to total dust abundance. One example is the elevated dust-laden Saharan Air Layer (SAL) over the tropical and subtropical North Atlantic, which cools the sea surface. To understand the formation mechanisms of a dust layer in the free troposphere, this study combines model simulations and dust observations collected during the first stage of the Saharan Mineral Dust Experiment (SAMUM-I), which sampled dust events that extended from Morocco to Portugal, and investigated the spatial distribution and the microphysical, optical, chemical, and radiative properties of Saharan mineral dust. The Weather Research Forecast model coupled with the Chemistry/Aerosol module (WRF-Chem) is employed to reproduce the meteorological environment and spatial and size distributions of dust. The model domain covers northwest Africa and adjacent water with 5 km horizontal grid spacing and 51 vertical layers. The experiments were run from 20 May to 9 June 2006, covering the period of the most intensive dust outbreaks. Comparisons of model results with available airborne and ground-based observations show that WRF-Chem reproduces observed meteorological fields as well as aerosol distribution across the entire region and along the airplane's tracks. Several mechanisms that cause aerosol entrainment into the free troposphere are evaluated and it is found that orographic lifting, and interaction of sea breeze with the continental outflow are key mechanisms that form a surface-detached aerosol plume over the ocean. The model dust emission scheme is tuned to simultaneously fit the observed total optical depth and the ratio of aerosol optical depths generated by fine and coarse dust modes. Comparisons of simulated dust size distributions with airplane and ground-based observations are good for optically important 0.4–0.7 µm particles, but suggest that more detailed treatment of microphysics in the model is required to capture the full-scale effect of large and very small aerosol particles beyond the above range.

Aerosol deposition in nasal passages of burrowing and ground rodents when breathing dust-laden air

The adaptation of subterranean rodents, which dig passages with their front teeth, to underground life presumes the formation of protection mechanisms against inhaling dust particles of different size when digging. One such mechanism can be a specific pattern of air-flow organization in the nasal cavity. To verify this assumption, we conducted a comparative study of the geometry and aerodynamics of nasal passages of a typical representative of subterranean rodents, the mole vole, and a representative of ground rodents, the house mouse. Numerical modeling of air flows and the deposition of micro- and nanoparticle aerosols indicate that sedimentation of model particles over the whole surface of the nasal cavity is higher in the mole vole than in the house mouse, while, on the contrary, particle deposition on the surface of the olfactory epithelium is much less in the burrowing rodent as compared to the ground rodent. The adaptive significance of the latter was substantiated by an experimental study on the inflow of hydrated manganese oxide MnO · (H2O)x and Mn ion nanoparticles from the nasal cavity into brain. It has been shown with use of magnetic resonance tomography (MRT) that there is no difference between the studied species with respect to the inflow of particles or ions by the olfactory bulb when they are introduced intranasally. Meanwhile, when inhaling a nanoparticle aerosol of MnCl2, the Mn deposition in the house mouse’s olfactory bulbs significantly exceeds that in the mole vole’s bulbs. Thus, the morphology of nasal passages as a factor determining the aerodynamics of upper respiratory tract ensures more efficient protection of both the lungs and brain against inhaled aerosols for burrowing rodents than for ground ones.

Downstream particle puffs emitted during pulse-jet cleaning of a baghouse wood dust collector: Influence of operating conditions and filter surface treatment

Baghouse dust collectors are widely used to remove wood particles from dust-laden air before it is expelled from or recycled into workplaces. Despite the growing use of filter media with supplementary surface treatment, conventional open-faced filter media or other common media are still widely used in the woodworking industry. More efficient filter media may help to reduce downstream particle emission. This article describes the emission performances of two polyester fiber filter media: one with a smooth anti-adhesive thermo-bonded surface, and the second covered with a microporous polymeric membrane. For the two media, 250 filtration cycles were performed on a 24-bag pulse-jet cleaned pilot dust collector loaded with coarse wood dust from a joinery workshop. Emitted particle concentrations and downstream particle size distributions were measured for various operating conditions. The data presented focus on particle puffs emitted during pulse-jet cleaning as this is known to be the most problematic stage.For both media, our results confirm the prevailing opinion that higher pulse-jet cleaning intensities increase particle emission, however this also reduces regeneration frequency. Increasing the maximum pressure drop across the filter bags before regeneration leads to higher average downstream mass concentrations during pulse-jet cleaning. The wood particles emitted during puffs are predominantly sub-micronic.For all operating conditions, the medium with a polymeric membrane was associated with lower particle emissions than the more commonly used thermo-bonded medium. However, during pulse-jet cleaning, neither of the media tested provided a mass concentration below 0.2mg·m−3, the recommended concentration value for air recycling in France.

Development of an Integrated Dust Collector and Local Exhaust Ventilation System for Controlling Industrial Mine Dust

Dust control in an enclosed mine environment is a fundamental key to personnel safety for boosting personnel productivity and enhancing successful operation, hence the need to design a dust control equipment to meet this crucial requirement. A laboratory-scale local exhaust ventilating system for the control of airborne dust in an enclosed mine environment was designed and fabricated. The design was carried out by considering various design criteria required for a well-ventilated enclosed mine environment. Material selection of the components was done by taking into cognisance the physical characteristics of the targeted dust. The system designed was fabricated and then test-ran with dry dust laden air stream in order to determine its cleaning efficiency with respect to variation in fan speed and dust grain size. It was observed that the cleaning efficiency of the machine was high at a higher fan speed and low grain sizes. The cleaning efficiency ranged from (63.9-44.0)% for dust particle sizes ranging from (62.5-125) to (1000-2000) μm with a mean fan suction of 0.958Pa. Thus, with this system, improved cleaning of dry dust-laden enclosed mine workplace could be achieved with increased rate of suction of smaller particle-sized dust.

Study on Contraction of Dust Control System in Continuous Coal Mining

Most of the dust control models indicate the line-curtain air reaching the face is limited and does not extend. Lower air quantity at the face helps in containing and concentrating the dust close to the face where no occupations are present. Hence, effective use of hydraulic sprays and directing the face dust-laden air into the scrubber may improve dust control. In this paper, we put forward a field testing of the modified scrubber-modified continuous miner demonstrated significant improvements in visibility and dust and quartz reduction, as compared to what was achieved with the current scrubber-current continuous miner dust control system. This is unfavorable from methane dilution point of view but can be used to advantage for improved dust control.

Evaluating the performance of a turbulent wet scrubber for scrubbing particulate matter

A turbulent wet scrubber was designed and developed to scrub particulate matter (PM) at micrometer and submicrometer levels from the effluent gas stream of an industrial coal furnace. Experiments were conducted to estimate the particle removal efficiency of the turbulent scrubber with different gas flow rates and liquid heads above the nozzle. Particles larger than 1 µm were removed very efficiently, at nearly 100%, depending upon the flow rate, the concentration of the dust-laden air stream, and the water level in the reservoir. Particles smaller than 1 µm were also removed to a greater extent at higher gas flow rates and for greater liquid heads. Pressure-drop studies were also carried out to estimate the energy consumed by the scrubber for the entire range of particle sizes distributed in the carrier gas. A maximum pressure drop of 217 mm H2O was observed for a liquid head of 36 cm and a gas flow rate of 7 m3/min. The number of transfer units (NTU) analysis for the efficiencies achieved by the turbulent scrubber over the range of particles also reveals that the contacting power achieved by the scrubber is better except for smaller particles. The turbulent scrubber is more competent for scrubbing particulate matter, in particular PM2.5, than other higher energy or conventional scrubbers, and is comparable to other wet scrubbers of its kind for the amount of energy spent. Implications: The evaluation of the turbulent scrubber is done to add a novel scrubber in the list of wet scrubbers for industrial applications, yet simple in design, easy to operate, with better compactness, and with high efficiencies at lower energy consumption. Hence the turbulent scrubber can be used to combat particulate from industrial gaseous effluents and also has a scope to absorb gaseous pollutants if the gases are soluble in the medium used for particles capture.

African dust source regions for observed dust outbreaks over the Subtropical Eastern North Atlantic region, above 25°N

High mineral dust-laden air mass potential source regions affecting the Marine Boundary Layer (MBL) of the Subtropical Eastern North Atlantic Region above 25°N (SENAR), directly or by means of gravitational settlement, were objectively identified. We introduced a new hybrid Lagrangian-Eulerian receptor model, in which air mass residence time probability maps in the geographical domain latitude = [5°N, 60°N], longitude = [70°W, 30°E] were combined with TOMS-AI data (TAPI Index), and with simulated Total Suspended Particles (TSP) with the BSC/DREAM model (SDPI Index). Both approaches show a good agreement. For dust gravitational settlement episodes within the MBL, the dust sources are located in southernmost latitudes compared to those associated with lower air mass transport. A seasonal variability in potential dust sources is found with both approaches, TAPI and SDPI. In winter, most dust sources are located within the Sahara in an area bounded by latitude = [18°N, 35°N], longitude = [15°W, 15°E]. In summer, a high dust-laden air mass reservoir above the Atlantic Ocean has been found during episodes for low altitudes, and dust source regions in the Sahara have been identified for middle and upper altitudes. The Bodelé depression was found to have a minor impact on dust outbreaks affecting the SENAR.

Atmospheric acidification of mineral aerosols: a source of bioavailable phosphorus for the oceans

Abstract. Primary productivity of continental and marine ecosystems is often limited or co-limited by phosphorus. Deposition of atmospheric aerosols provides the major external source of phosphorus to marine surface waters. However, only a fraction of deposited aerosol phosphorus is water soluble and available for uptake by phytoplankton. We propose that atmospheric acidification of aerosols is a prime mechanism producing soluble phosphorus from soil-derived minerals. Acid mobilization is expected to be pronounced where polluted and dust-laden air masses mix. Our hypothesis is supported by the soluble compositions and reconstructed pH values for atmospheric particulate matter samples collected over a 5-yr period at Finokalia, Crete. In addition, at least tenfold increase in soluble phosphorus was observed when Saharan soil and dust were acidified in laboratory experiments which simulate atmospheric conditions. Aerosol acidification links bioavailable phosphorus supply to anthropogenic and natural acidic gas emissions, and may be a key regulator of ocean biogeochemistry.

Laboratory Evaluation to Reduce Respirable Crystalline Silica Dust When Cutting Concrete Roofing Tiles Using a Masonry Saw

Respirable crystalline silica dust exposure in residential roofers is a recognized hazard resulting from cutting concrete roofing tiles. Roofers cutting tiles using masonry saws can be exposed to high concentrations of respirable dust. Silica exposures remain a serious threat for nearly two million U.S. construction workers. Although it is well established that respiratory diseases associated with exposure to silica dust are preventable, they continue to occur and cause disability or death. The effectiveness of both a commercially available local exhaust ventilation (LEV) system and a water suppression system in reducing silica dust was evaluated separately. The LEV system exhausted 0.24, 0.13, or 0.12 m 3 /sec of dust laden air, while the water suppression system supplied 0.13, 0.06, 0.03, or 0.02 L/sec of water to the saw blade. Using a randomized block design, implemented under laboratory conditions, the aforementioned conditions were evaluated independently on two types of concrete roofing tiles (s-shape and flat) using the same saw and blade. Each engineering control (LEV or water suppression) was replicated eight times, or four times for each type of tile. Analysis of variance was performed by comparing the mean airborne respirable dust concentrations generated during each run and engineering control treatment. The use of water controls and ventilation controls compared with the “no control” treatment resulted in a statistically significant (p < 0.05) reduction of mean respirable dust concentrations generated per tile cut. The percent reduction for respirable dust concentrations was 99% for the water control and 91% for the LEV. Results suggest that water is an effective method for reducing crystalline silica exposures. However, water damage potential, surface discolorations, cleanup, slip hazards, and other requirements may make the use of water problematic in many situations. Concerns with implementing an LEV system to control silica dust exposures include sufficient capture velocity, additional weight of the saw with the LEV system, electricity connections, and cost of air handling unit.

Response to “Aerosol iron deposition to the surface ocean — Modes of iron supply and biological responses” by P.W. Boyd, D.S. Mackie, and K.A. Hunter

Boyd et al. (in press) propose a relatively simple tool that observationalists can use to constrain the extent to which biological events, such as observed episodic phytoplankton blooms, are driven by dust supply to the ocean environment. In their paper, they use this tool to examine four case studies from the literature, one of whichwas authored by Lenes et al. (2001). Boyd et al. (in press) definitively conclude that the 100-fold Trichodesmium biomass increase on the West Florida shelf (WFS) that occurred by July 1999 could not be attributed to the alleviation of iron (Fe) limitation by deposition of Saharan dust. Their calculations of iron deposition incorporate multiple assumptions related to atmospheric dust concentration, solubility, wet deposition, and air column height. In all iron deposition studies, large uncertainties are associatedwith each of these variables. For example, as acknowledged in their work, iron solubility can range over 5 orders of magnitude with changes in medium, pH, and particle size. While dissolution rates for soil dust are low (b1–2%; Jickells and Spokes, 2001), solubility can be substantially increased by organic complexation, and the proximity of the WFS region to industrial centers can greatly enhance the acidity of mineral aerosols due to mixing with SO2 and NOx (Jickells et al., 2005). Boyd et al. (in press) calculated that 600 μmol Fe m−2 was available for wet deposition in one day during the 27 June–4 July dust event. Given a 5-m surface mixed layer (SML) and a 2% dissolution rate, a net concentration increase of 2.4 nmol L−1 would result in the SML. This is similar to the ~3 nmol L−1 mean offshore iron concentration reported on 5–7 July (Lenes et al., 2001). In addition, this estimate does not account for increased SML iron concentrations from a prior dust event on 15–17 June. Similarly, Boyd et al. (in press) misunderstand the properties of the Saharan Air Layer (SAL). The SAL is an elevated layer of hot, dry, dust-laden air that originates over the Sahara (Prospero and Carlson, 1972). Over the Caribbean and southern Florida the layer is typically 2 km thick and extends to an altitude of 3–4 km, sometimes higher (Gatz and Prospero, 1996; Reid et al., 2003). Furthermore, Boyd et al. (in press) assume that the measured surface dust concentration is applicable to the SAL; in reality, dust concentrations in the layer are on average about three times higher than concentrations at the surface (Prospero and Carlson, 1972; Reid et al., 2003). Considering these

The ventilation of an underground crushing plant

The use of compressive crushing plant such as gyratory crushers within minerals processing operations can generate large quantities of dust as large volumes of ore are tipped into the crusher feed bins. Methods to reduce these dust emissions include the retrofitting of shrouds, enclosures, local exhaust ventilation (LEV) systems and water suppression systems. The operation of these ancillary systems should be optimised to offer maximum performance. It is desirable that the future planning of such facilities include sufficient dust suppression and/or removal systems to ensure that material delivery rates are maintained and the welfare of the workforce is protected. This paper presents the results of an investigation of the tipping process through the application of computational fluid dynamic (CFD) methods and validation using data obtained from scale experiment. A 3-D computational model has been constructed using the Fluent™ <www. fluent. co. uk> modelling software to represent the ventilation regimen within an underground crushing installation. The falling ore has been represented as a granular fluid continuum falling under gravity from the bed of the dump truck. Transient streamlines are used to represent the dispersion of dust due to the updraft airflow generated by the tipping process. A parametric analysis has been performed on a model of the tipping process to investigate the influence on dust dispersion of; the orientation of the dump truck, the surrounding ventilation characteristics and the material tipping rate and volume. The CFD models predict a strong shear-induced flow in the region of the crusher during tipping and a high sensitivity to the surrounding ventilation regimen. These results indicate the need for further experimental studies to characterise the entrainment and transport of dust-laden air into the induced shear flow. An experimental rig has been designed and evaluated for the purposes of conducting validation studies and gaining further insight into this phenomenon. Results of these investigations are presented.

Aerosol particle chemical characteristics measured from aircraft in the lower troposphere during ACE-2

During the Aerosol Characterization Experiment (ACE-2), filter samples were collected aboard the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Pelican aircraft near Tenerife in June and July of 1997. The flights included constant altitude measurements in the boundary layer as well as profiles up to 3800 m providing detailed chemical information about the composition of the aerosol distribution in the lower troposphere. Three cases with different air mass origins—clean marine air, anthropogenically-influenced air from the European continent, and dust-laden air from the Sahara—were identified. The samples were analyzed by ion chromatography (IC) for ionic species, by combined thermal and optical analysis (TOA) for organic carbon, and by total reflection X-ray fluorescence (TXRF) for elemental composition. Particle composition and size distributions for the range of air masses encountered illustrate links in the chemical and microphysical characteristics of aerosol from different sources. Clean marine air masses were characterized by low particle number and mass concentrations with no detectable metals, while anthropogenically-influenced and dust-laden air had high number, mass, and trace metal concentrations. Anthropogenic sources were characterized by high concentrations of submicron particles and some Fe and Cu, whereas dust particle loadings included a significant mass of micron-sized particles and significant loadings of Fe, in addition to small amounts of Mn, Cu, and Ni. These results showed similar tracers for air mass origin as those found in other measurements of oceanic and continental air masses. Aerosol optical properties were estimated with a simplified model of the aerosol based on the measured compositions. The real and imaginary refractive indices and single scattering albedos differed significantly among the three types of aerosol measured, with clean marine aerosol properties showing the least absorption and dust-containing aerosols showing the most. There were only small differences in optical properties for the two different cases of clean marine aerosol, but some significant differences between the two dust cases. Since measurement uncertainties affect these calculations, we studied the type of mixing and the fraction of absorbing species and found the calculation was sensitive to these variations only for the dust-containing aerosol case, probably due to the small amount of water present. While the optical properties varied little with composition for clean marine and anthropogenically-influenced cases, they showed a strong dependence on variations in particle composition and mixing state for the dust-containing cases.

Influence of gas velocity on cake formation and detachment

This work presents an experimental study of the influence of gas velocity during filtration on cake formation and its removal. The experimental data were obtained using a polyester felt of squared section, with an area of 0.0225 m 2, through which the dust laden air was driven. The behaviour of the filter during filtration and cleaning was studied using four filtration velocities (0.048; 0.067; 0.074 and 0.089 m s −1). For each filtration velocity, four cakes with different thicknesses were tested. For each cake formed, the cleaning of the fabric was performed using the reverse flow technique, and the cake/fabric adhesion force was estimated. The results showed that the cake porosity decreased and the cake specific resistance increased with increase in the superficial velocity of filtration. Also, for the same powder (dust) being fed, the mean particle size of the material forming the cake increased with increasing filtration velocity, probably due to particle settling before reaching the filter. The cake/fabric adhesion force was estimated as well as the effective distance between the particle surfaces. The calculated values of both were well within the range reported in the literature. The former increased and the latter decreased with increase in the superficial velocity of filtration.

Dust collection efficiency of a straight-through cyclone — effects of duct length, guide vanes and nozzle angle for secondary rotational air flow

This paper is concerned with an experimental investigation of the dust collection efficiency of a straight-through cyclone. The suction of dust-laden air into the cyclone is induced by a secondary rotational air flow from eight nozzles which are set on the duct wall. This study is an extension of the previous study, and deals with greater variations in duct size, nozzle angle, and the position of guide vanes. Studies were made also on cut size, critical particle diameter, particle size distribution and fractional efficiency.

Choosing respiration with allowance for the disperse composition and concentration of dust-laden air

Choosing respiration with allowance for the disperse composition and concentration of dust-laden air

Storm water pollution modelling: buildup of dust and dirt on surfaces subject to runoff

Many runoff models are currently in use to predict both the quantity and quality of storm water runoff. In most models, the quality algorithms need further development to gain the confidence of model users. The writers have attempted to disaggregate the accumulation process and to develop improved algorithms for pollutant buildup. The factors and processes that affect buildup include atmospheric dustfall due to plumes of dust-laden air, wind effects, vehicles, intentional removals (e.g., street cleaning), special activities (such as construction and demolition), biological decomposition, and population-related activities (e.g., vegetation density, insecticides, herbicides, fertilizers, and lawn cutting). Mathematical expressions for each of these mechanisms are presented and utilized to develop algorithms in the RUNOFF module of the SWMM3 package.A separate multiregression model is used to generate atmospheric dustfall from meteorological information; this is input to the new program (NEWBLD) to calculate pollutant accumulation on individual subcatchments. NEWBLD is interfaced with the RUNOFF block of SWMM3. A sensitivity analysis is carried out using data for the Chedoke Creek catchment in Hamilton, Ontario. The modified version of the SWMM3 RUNOFF block developed herein by incorporating the new water quality algorithms is called CHGQUAL. It is applied to an urban catchment in Hamilton, Ontario. Key words: storm water models, dust and dirt buildup, storm water pollution, urban hydrology, air pollution.

Charged Fog Technology Part II: Prototype Tests of a New Charged Fog Generator for Fugitive Emission Control

The prototype charged fog generator described in a preceding paper1 was field tested on a fugitive emission source at a bentonite ore processing plant in Worland, Wyoming, during 1981. Participate matter samples were collected as fine and coarse fractions under three different test scenarios: with no control, with partial control (uncharged fog), and with full control (charged fog). Measured particulate matter sample concentrations were normalized for each test day with respect to the background values so that particle control efficiency of the device could be evaluated without any bias during the entire test program. These tests have shown that mean value of the inhalable particle control efficiency of charged fog measured under all instrument settings and field conditions is increased by 78% when compared with uncharged fog. In particular, fine particle control efficiencies of over 90% were recorded under optimum instrument settings and ideal field conditions. The bentonite particles seemed to carry a net positive charge. The optimum instrument settings were found to be: 60 L/h water flow rate, an applied voltage of 10-15 kV and a spray pattern which covers maximum volume of dust-laden air. Ideal field conditions are high relative humidity and calm or low winds. Charged fog technology appears to be an effective and economically feasible method to control sources of fugitive particle emission in the inhalable size range. Further research is needed to evaluate the inhalable particle control efficiency of the device for emissions of various chemical compositions.