Heavy Dust Loading Research Articles

Investigation on the role of aerosols on precipitation enhancement over Kerala during August 2018

Previous studies based on satellite data and model analysis have shown that the dust over Arabian Sea correlates positively with the Indian summer monsoon. During August 2018, over a period of a few days from August 13, the state of Kerala experienced anomalous rainfall, which was followed by heavy floods. In the present study, the meteorological factors and the aerosol conditions during this event are investigated. MERRA 2 reanalysis data suggests that the dust loading over the Arabian Sea during the month of August, during which the anomalous event of rainfall took place, is the highest in the last decade. Using CALIPSO aerosol vertical profiles, OMI Absorbing Aerosol Index and the HYSPLIT back trajectory analysis, higher altitude dust transport from the arid gulf region towards the Arabian sea and near to Kerala coast is confirmed during the heavy precipitation days and even prior to that. Changes in cloud properties like Cloud Fraction (CF), Cloud Top Temperature (CTT), Cloud Water Liquid Water Path (CWLWP) and Cloud Condensation Nuclei (CCN) with AOD variations during the period clearly indicate that there is a close relation between the aerosols and the cloud properties over the region. Observed CWLWP in the study on August 14 and 15, 2018 was 80% higher than the monthly average value. CCN concentration was increased by 23 percent during the severe rainy days of August when the CTT was about 16 K lower than the monthly mean value. Dust aerosols at altitudes of 2–4 km and further higher at 10–15 km, along with the deep convective clouds, point to the possibility of aerosol-cloud-precipitation interaction under conducive meteorological conditions. INSAT- 3D temperature profiles show an interesting enhancement of temperature (∼1 K) at altitudes ∼ 3 km, where elevated dust layers are noticed. This elevated heating could pave the way for moisture convergence and it is further confirmed from the INSAT derived Relative Humidity profiles. Investigation of vertical winds shows strong updrafts over the region during the period of heavy precipitation, indicative of the coexistence of moisture and CCN at higher altitudes. The study infers that the moisture built up over the region was excessive, enough to overwhelm the commonly observed semi direct effect caused by aerosols, and in contradiction, the aerosols amplify the cloud cover and precipitation over the Kerala region during the period of study. Thus the heavy dust loading over the South Eastern Arabian Sea region, near the west coast of Kerala, together with the conducive meteorological conditions and orography of the region led to intensified precipitation over Kerala during the mid of August 2018.

Black carbon-climate interactions regulate dust burdens over India revealed during COVID-19

India as a hotspot for air pollution has heavy black carbon (BC) and dust (DU) loadings. BC has been identified to significantly impact the Indian climate. However, whether BC-climate interactions regulate Indian DU during the premonsoon season is unclear. Here, using long-term Reanalysis data, we show that Indian DU is positively correlated to northern Indian BC while negatively correlated to southern Indian BC. We further identify the mechanism of BC-dust-climate interactions revealed during COVID-19. BC reduction in northern India due to lockdown decreases solar heating in the atmosphere and increases surface albedo of the Tibetan Plateau (TP), inducing a descending atmospheric motion. Colder air from the TP together with warmer southern Indian air heated by biomass burning BC results in easterly wind anomalies, which reduces dust transport from the Middle East and Sahara and local dust emissions. The premonsoon aerosol-climate interactions delay the outbreak of the subsequent Indian summer monsoon.

Influence of Dust on the Initiation of Neoproterozoic Snowball Earth Events

AbstractIt has been demonstrated previously that atmospheric dust loading during the Precambrian could have been an order of magnitude higher than in the present day and could have cooled the global climate by more than 10 °C. Here, using the fully coupled atmosphere-ocean general circulation model CESM1.2.2, we determine whether such dust loading could have facilitated the formation of Neoproterozoic snowball Earth events. Our results indicate global dust emission decreases as atmospheric CO2 concentration (pCO2) decreases due to increasing snow coverage, but atmospheric dust loading does not change or even increases due to decreasing precipitation and strengthening June-July-August (JJA) Hadley circulation. The latter lifts more dust particles to high altitude and thus increases the lifetime of these particles. As the climate becomes colder and the surface albedo higher, the cooling effect of dust becomes weaker; when the global mean surface temperature is approximately -13 °C, dust has negligible cooling effect. The threshold pCO2 at which Earth enters a snowball state is between 280 to 140 ppmv when there is no dust, and is similar when there is relatively light dust loading (~4.4 times present-day value). However, the threshold pCO2 decreases dramatically to between 70 to 35 ppmv when there is heavy dust loading (~33 times present-day value), due to the decrease in planetary albedo which increases the energy input into the climate system. Therefore, dust makes it more difficult for Earth to enter a snowball state.

Particulate fouling assessment in membrane based air-to-air energy exchangers

The impact of air-side particulate fouling on the performance of membrane-based, fixed-plate energy recovery ventilators (ERVs) is investigated for both fine and coarse (0.3–10μm) as well as ultrafine (∼0.1μm) aerosols. Two residential size cross-flow ERV exchanger cores were fouled with ISO A3 medium test dust. It was found that coarse dust loading, equivalent to that of a few years of exposure in a heavily polluted environment, has minimal impact on the performance of ERV exchanger cores. In both cases, the sensible and latent effectiveness were actually slightly enhanced due to boundary layer thinning and additional turbulence potentially caused by the dust layer. Heavy dust loadings, in the absence of appropriate filtration upstream, may result in a fan energy penalty (∼50%) due to the added pressure drop across the exchanger cores.Samples of three different membrane transport media, extracted from commercial HVAC ERV exchanger cores, were loaded with graphite and NaCl aerosol nanoparticles. Accelerated loading experiments were conducted in a laboratory apparatus to simulate several years of fouling in the field. Initial and post-loading water vapor permeance through the membrane samples were experimentally determined for each loading to quantify the effects of fouling. The impact of relative humidity on the performance of loaded membranes was also studied by exposing membranes loaded with particles in dry air to an elevated RH of 75%, leading to surface condensation. The experiments show that the deposition of particles in dry air can only affect the membrane when the fouling is severe enough to form a cake layer on the membrane surface comparable to the thickness of the membrane. In the case of membranes loaded with hygroscopic salt particles, surface condensation at high RH values can lead to vapor permeance reductions of up to 15% well before the cake layer formation phase of fouling, whilst no permeance reduction was observed for membranes loaded with non-hygroscopic graphite particles. This indicates a net porosity reduction in the microporous substrate layer of exposed salt-loaded samples. A pore-narrowing process of the substrate layer, due to the mobilization of salt particles in aqueous form, is a potential explanation for these observations.

Aerosol climatology at Delhi in the western Indo‐Gangetic Plain: Microphysics, long‐term trends, and source strengths

AbstractWe present the climatology of aerosol microphysics, its trends, and impact of potential sources based on the long term measurements (for a period of 11.5 years from December 2001 to May 2012) of aerosol optical depths (AOD) in the spectral range 340–1020 nm from an urban center Delhi (28.6°N, 77.3°E, 238 m mean sea level) in the western Indo‐Gangetic Plain (IGP). The study is the first ever long‐term characterization of aerosols over the western IGP from the ground‐based measurements. AODs are known to affect the air quality, visibility, radiative balance, and cloud microphysics of the region and IGP is one of the highest populated and polluted regions of the world. Our measurements show consistently high AOD during the entire period of observation. The seasonal variations of spectral AODs and Angstrom parameters are generally consistent every year. The AODs show a weak but statistically significant (in 95% confidence level) decreasing trend approximately −0.02/year at 500 nm, possibly, modulated by the pre‐monsoon heavy dust loading during the first half of the observation period. The climatological monthly mean AOD at shorter wavelengths peaks twice, during June and November, while at longer wavelengths it shows only one peak in June. The annual variations of Angstrom exponent, α and its derivative, α′ suggest the prevalence of multi‐modal aerosol size distributions at Delhi. The coarse‐mode aerosols dominate during summer (March–June) and monsoon (July–September) seasons, whereas fine/accumulation mode enhances during post‐monsoon (October–November) and winter (December–February) seasons. Potential advection pathways have been identified using concentration weighted trajectory (CWT) analysis of the 5 day isentropic air mass back trajectories at the observation site and their seasonal variations are discussed.

The effect and correction of aerosol forward scattering on retrieval of aerosol optical depth from Sun photometer measurements

The Sun photometer is widely used to retrieve aerosol optical depth (AOD). In this study, the effect of atmospheric forward scattering on the measurement of direct solar irradiance is analyzed. In most cases, this effect can be safely neglected. However, in the case of heavy dust loading, errors in AOD derived from Sun photometer measurements can be significant which warrants a correction of the forward scattering to derive accurate values of AOD. An algorithm is presented for such a correction.

Utilization of rice-husk packed beds as fine dust collectors at heavy dust loadings

Typical rice mills generally generate tonnes of biomass which is rice husks and a significant quantity of coarse and fine dusts from the paddy, resulting in public health concern. Instead of normal air cyclones which are not efficient for collecting fine soft-hair (detached pubescence) particles smaller than a few microns, a new system using packed beds of rice husks was developed for collection fine dusts. It was found that the rice-husk packed beds could exhibit an effective performance in capturing fine dusts at various dust loadings with collection efficiency higher than 85% by mass. The filtrating phenomenon could be observed as an integrated effect of cake and deep-bed filtrations due to the heavy dust loads, agglomeration of dusts, and cohesion between the dusts and bed of irregularly shaped rice husks. Both the pressure drop across the bed and the overall filtration efficiency remarkably increased at the initial clean stage, then increased more slowly due to the recurrent fracture of the dust cake layer.

Separated status of the natural dust plume and polluted air masses in an Asian dust storm event at coastal areas of China

Asian dust particles usually refer to mineral particles which originate from arid and semiarid areas in the Asian continent and disperse eastward in a wide range in the atmosphere. Their appearances in the downstream marine areas are always accompanied by high concentrations of sulfate and nitrate, suggesting their significance as a medium for pollutant conversion and transportation. However, analysis of particles collected at a coastal site in east China before and after the cold front arrival of a heavy dust–loading low‐pressure system in this study revealed that air masses polluted by anthropogenic emissions from local or regional areas and the natural Asian dust plume from northwest China were in different air parcels. Anthropogenic pollutants were in the prefrontal air while the so‐called Asian dust particles were in the postfrontal air. There was a large amount of anthropogenic mineral particles in the polluted air masses, and the particles were abundant in sulfur, sodium, and calcium, while the so‐called Asian dust particles were very “clean” (meaning lack of anthropogenic pollution). Continuous records of PM10, SO2, and O3 concentrations indicated that the cold front was the boundary layer between the polluted air masses and the clean dust plume. Hence, at the coastal areas the Asian dust plume and polluted air masses did not mix with each other and were separated in two consecutive air parcels by the cold front although they were in the same low‐pressure system. In addition, the analysis also revealed that calcium was not a good indicator for Asian dust from natural sources because the anthropogenic mineral particles contained significant calcium.

Impacts of dust on regional tropospheric chemistry during the ACE‐Asia experiment: A model study with observations

A comprehensive regional‐scale chemical transport model, Sulfur Transport and Emissions Model 2001 (STEM‐2K1), is employed to study dust outflows and their influence on regional chemistry in the high‐dust Asian Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) period, from 4–14 April 2001. In this period, dust storms are initialized in the Taklamagan and Gobi deserts because of cold air outbreaks, are transported eastward, and are often intensified by dust emitted from exposed soils as the front moves off the continent. Simulated dust agrees well with surface weather observations, satellite images, and the measurements of the C‐130 aircraft. The C‐130 aircraft observations of chemical constituents of the aerosol are analyzed for dust‐rich and low‐dust periods. In the submicron aerosol, dust‐rich air masses have elevated ratios of ΔCa/ΔMg, ΔNH4+/ΔSO42−, and ΔNO3−/ΔCO (Δ represents the difference between observed and background concentrations). The impacts of heterogeneous reactions on dust involving O3, NO2, SO2, and HNO3 are studied by incorporating these reactions into the analysis. These reactions have significant influence on regional chemistry. For example, the low O3 concentrations in C‐130 flight 6 can be explained only by the influence of heterogeneous reactions. In the near‐surface layer, the modeled heterogeneous reactions indicated that O3, SO2, NO2, and HNO3 are decreased by up to 20%, 55%, 20%, and 95%, respectively, when averaged over this period. In addition, NO, HONO, and daytime OH can increase by 20%, 30%, and 4%, respectively, over polluted regions. When dust encounters fresh pollutants, these heterogeneous reactions can lead to a series of complex responses of the photochemical system. In addition, these reactions can alter the chemical‐size distribution of the aerosol. Under heavy dust loadings, these reactions can lead to >20% of the sulfate and >70% of the nitrate being associated with the coarse fraction. The radiative influence of dust can also affect the photochemical system. For example, OH levels can decrease by 20% near surface. The dust radiative influence is shown to be weaker than the heterogeneous influence for most species.

Mineral aerosol contamination of TIROS Operational Vertical Sounder (TOVS) temperature and moisture retrievals

Since mineral aerosols absorb significant amounts of infrared radiation, they may contribute to errors in the retrievals of atmospheric and surface parameters from the TIROS Operational Vertical Sounder (TOVS) High‐Resolution Infrared Radiation Sounder (HIRS) if the atmosphere is assumed clear. TOVS is an operational sounder on NOAA polar satellites. To see if observed brightness temperatures are reduced by mineral aerosol, we analyzed results from the Data Assimilation Office (DAO) Finite Volume Data Assimilation System (fvDAS). Every 6 hours the assimilated temperature and moisture profiles are used as a first guess in the DAO interactive cloud‐clearing TOVS retrieval system. The observed minus the forecast (O–F) brightness temperature, which is a measure of the accuracy of the first guess and radiative transfer parameters, becomes more negative with increasing dust concentrations. Dust concentrations are from the Goddard Ozone Chemistry Aerosol Radiation Transport (GOCART) model. Since there was no account of dust during this fvDAS run, the dependence of O–F on the estimated atmospheric dust concentrations from GOCART indicates that the dust is affecting the TOVS brightness temperatures. HIRS channels that are sensitive to the surface temperature, lower tropospheric temperature, and moisture are subject to a 0.5 K or more reduction in the brightness temperature during heavy dust loading conditions. The radiative transfer module used in the TOVS retrieval system was modified to account for dust assuming a composition of illite, and the fvDAS run was repeated. Accounting for dust absorption in the retrieval system yields warmer surface temperatures (0.4 K) and warmer lower tropospheric temperatures in regions of moderate dust loading over the tropical Atlantic.

Distribution of airborne particles from multi-emission source.

The purpose of this work was to study the distribution of airborne particles in the surroundings of an iron and steel factory in southern Finland. Several sources of particulate emissions are lying side by side, causing heavy dust loading to the environment. This complicated multi-pollutant situation was studied mainly by SEM/EDX methodology. Particles accumulated on Scots pine bark were identified and quantitatively measured according to their element content, size and shape. As a result, distribution maps of particulate elements were drawn and the amount of different particle types along the study lines was plotted. Particulate emissions from the industrial or energy production processes were not the main dust source. Most emissions were produced from the clinker crusher. Numerous stockpiles of the industrial wastes and raw materials also gave rise to particulate emissions as a result of wind erosion. It was concluded that SEM/EDX methodology is a useful tool for studying the distribution of particulate pollutants.

Remote sensing aerosols using satellite infrared observations

Aerosol detection techniques using infrared wavelengths have a distinct advantage over visible techniques by providing coverage over bright surfaces and during the night. This study investigates detection of volcanic and soil‐derived aerosols, two important aerosols in studies of the earth's climate, using infrared observations at the following approximate wavelengths 8.5, 11, and 12 μm. Detection is based on brightness temperature differences among the three channels BT11‐BT12 and BT8‐BT11. It is demonstrated that these three infrared channels are useful for detecting stratospheric volcanic aerosols over oceans. Theoretical simulations agree with observations from current satellite instruments. Detection of the stratospheric aerosol over land is complicated by spectral variation of surface emissivity. Retrieving aerosol optical depth over land requires defining the surface spectral emittance. Detecting the presence of soil‐derived aerosols can also be aided with infrared observations. Increasing the dust optical depth increases BT11‐BT12 and BT8‐BT11. The effect is opposite to that of an H2SO4 stratospheric aerosol and differs from an increase in atmospheric precipitable water, though addition of ice clouds moves the differences in the same direction. Retrievals of aerosol optical depth over the desert must account for surface emissivity and the vertical distribution of the dust. Negative differences in BT11‐BT12 are observed to occur for dust storms over the Arabian Peninsula, Africa, and the southwest United States and is useful for remote sensing source regions of dust outbreaks. These negative differences can be simulated using the theoretical model but requires a specific dust aerosol model. There are inconsistencies between theoretical simulations of the infrared properties of heavy dust loadings and the satellite observations. Negative differences in BT11‐BT12 are useful for detecting and tacking dust storms.

16.P.15 Dust particle collection efficiency of cold precharger and pulse energized electrostatic precipitator under heavy dust loadings

16.P.15 Dust particle collection efficiency of cold precharger and pulse energized electrostatic precipitator under heavy dust loadings

Dust Overloading of Lungs: Investigations of Various Materials, Species Differences, and Irreversibility of Effects

ABSTRACT In separate inhalation investigations, rodents (Wistar rats, Fischer-344 rats, Syrian golden hamsters, NMRI and C57BL mice) were exposed to various dusts such as test toner (polymer pigmented with carbon black), polyvinyl chloride, carbon black, diesel exhaust and two crystalline forms of titanium dioxide (anatase and rutile). The animals inhaled various concentrations (0.8 to 64 mg/m3) of these particles for up to 2 years. Alveolar clearance retardation was detectable above a retained pulmonary burden of 0.5 mg per rat lung, and a substantial decrease in the clearance rate (about a factor of 6) was observed following heavy dust loading, exceeding 10 mg dust per rat lung. Above a threshold lung burden, signs of lung overloading persisted 15 months after cessation of exposure in F-344 rats. Retardation of alveolar clearance was also observed in hamsters, commencing at higher lung burdens (normalized to lung weight) than in rats. At high dust exposure levels, persistent pulmonary inflammation was p...

Cleaning of HGMF matrices

The successful application of high-gradient magnetic filtration to the processing of steelmaking waste gases will require an effective method of cleaning the matrix after use. Three cleaning methods have been tested on a laboratory scale, viz. mechanical rapping, blowing with compressed air jet and infrasonic cleaning. Dry basic oxygen furnace dust was used in the tests. All three methods were effective, with 95% removal or greater attainable. Sonic cleaning removed 93% within 20 seconds. In contrast, the air jet removed less than 90% in three minutes, although subsequent flow reversal improved the removal rate, suggesting the superiority of oscillatory flow. Rapping produced good removal provided that it was vigorous, removal being initially rapid when the matrix was fully loaded. As expected, infrasonic cleaning became increasingly effective as the peak velocity was increased. The peak oscillatory velocity attained was 7.9 m/s, which corresponded to a sound pressure level measurement of 125 dB. Even at such high levels, no silencing was necessary because of the sub-sonic frequency of 12 Hz. Infrasound permits in-situ cleaning with remote apparatus, requires minimal purge flow and can copy with heavy dust loadings.