Maximum Dust Load Research Articles

Long-lifetime water-washable ceramic catalyst filter for air purification

Particulate matter (PM) and volatile organic compounds (VOCs) are recognised as hazardous air pollutants threatening human health. Disposable filters are generally used for air purification despite frequent replacement and waste generation problems. However, the development of a novel regenerable and robust filter for long-term use is a huge challenge. Here, we report on a new class of facile water-washing regenerable ceramic catalyst filters (CCFs), developed to simultaneously remove PM (>95%) and VOCs (>82%) in single-pass and maximized space efficiency by coating the inner and outer filter channels with an inorganic membrane and a Cu2O/TiO2 photocatalyst, respectively. The CCFs reveal four-fold increase in the maximum dust loading capacity (approximately 20 g/L) in relation to conventional filters (5 g/L), and can be reused after ten regeneration capability with simple water washing retaining initial PM and VOC removal performances. Thus, the CCFs can be well-suited for indoor and outdoor air purification for 20 years, which shows a huge increase in lifetime compared to the 6-month lifespan of conventional filters. Finally, we believe that the development and implementation of CCFs for air purification can open new avenues for sustainable technology through renewability and zero-waste generation.

Simulation of Martian Dust Effects on Polar CO2 Ice Caps and Atmospheric Circulation Using the MarsWRF Model

AbstractMartian dust plays an important role in modulating climate. However, the effects of dust on polar CO2 ice caps, atmospheric circulation processes and the relationship between them are not yet clear. In this study, a Mars general circulation model (MarsWRF) was applied to investigate the impacts of the magnitude and timing of Martian dust storms on the spatiotemporal characteristics of polar CO2 ice caps and atmospheric circulation. The results show that dust can inhibit the sublimation of southern CO2 ice through the radiation effect. Under the “High Dust” scenario, the ice edge can extend up to 5° more equatorward than that under the “Standard” scenario around Ls = 220°. The extent of northern CO2 ice cap is hardly affected by dust because the impacts induced by dust mainly appear north of 80°N. By shifting the timing of maximum dust loading during the dust season, the "Early Dust" scenario inhibits the sublimation of the southern ice cap, while the "Late Dust" scenario accelerates the sublimation process. In addition, the variations in dust loading strength can lead to changes in three near‐surface wind belts, which are related to intensified Hardly circulation. The appearance of the warming vortex under the "Early Dust" scenario is delayed, and its intensity is 60 K lower than that observed in the "High Dust" and "Late Dust" scenarios. When dust loading increases, the northern CO2 condensation process in the Western Hemisphere accelerates, which is due to the increased pole‐to‐equator temperature gradient and the increased meridional wind speed.

Spatiotemporal regionalization of atmospheric dust based on multivariate analysis of MACC model over Iran

Extraordinary dry conditions on the desert and arid areas in Iran, along with strong influences from surrounding dust sources in the Middle East and Arabia, have exposed the country to substantial amounts of dust aerosols with serious impacts on environment, health and socio-economic aspects. Considering this threat, daily aerosol optical depth (AOD) data over Iran obtained from the Monitoring Atmospheric Composition and Climate (MACC) reanalysis during 2003–2012 were used to analyze the spatial and temporal patterns of total AOD (TAOD) and dust AOD (DAOD). This study identifies the areas mostly affected by TAOD and DAOD in terms of daily average values and the areas associated with distinct temporal patterns, utilizing S-mode and T-mode principal component analysis (PCA). The analysis reveals six distinct sub-regions in southeast, west-northwest, northeast, east, central and southwest of Iran, which are among the major centers influenced by TAOD and DAOD extremes. The main findings of the T-mode results, consistent with TAOD and DAOD S-mode patterns, are (i) the maximum dust loading over the eastern, southeastern and southwestern subregions in March and May, (ii) dust loading with peaks in November over the eastern and northeastern sub-regions; (iii) maximum number of dusty days in July and August over southwest, (iv) maximum dust in July over southeastern and Central Iran, (v) a dust pattern with identical extent over the west and northwest sub-region in March and October and, (vi) a prevailing dust loading over the dry areas (Lut desert, Sistan plain and southwest edge of the territory) in October. The spatiotemporal evolution of dust is a function of the growth and expansion of dust extremes originated from various sources in Iran and the Middle East. The PCA methodology, through simplification of aerosol distribution to simpler structures, was also incorporated to provide a geographical interpretation of the highly sensitive territory of Iran.

Atmospheric Investigation of Frontal Dust Storms in Southwest Asia

In this paper, an atmospheric investigation of frontal dust storms in southwest Asia is presented. Atmospheric analysis is done on six severe frontal dust storms which occurred on the Tigris and Euphrates alluvial plain dust sources in non-summer seasons during the last two decades. NCEP-NCAR Reanalysis Data were used for synoptic analysis, and the Aerosol Optical Depth (AOD) data were used to identify the dusty days, dust plumes, and estimation of the dust load over the area. Atmospheric analysis results demonstrated that in non-summer seasons, the high pressure system over the southeastern Arabian Peninsula and neighboring areas with the low pressure system over the east of the Mediterranean Sea and neighboring areas are responsible for noticeable frontal dust storms over the Tigris and Euphrates rivers valley dust sources. These circulation systems provide a favorable condition for southeastward, northeastward, and eastward transport of the dust plumes. An investigation on the affected area by the dust plumes demonstrated that southern Iraq, Kuwait and the Khuzestan province in Iran have the highest AODs and dust load during the investigated dust events. Central Iraq, western and southwestern Iran, and northeastern Saudi Arabia are the regions which were affected by frontal dust storms dust plumes more than the other areas in the Middle East. Studies have shown that the most severe frontal dust storms occurred during March and April and the analysis of the MODIS (Moderate Resolution Imaging Spectroradiometer) AODs data demonstrated that the maximum dust load over the area exceeded 5 g m−2.

Estimation of Aerosol Characteristics and Radiative Forcing during Dust Events over Dehradun

Dust storm, a natural hazard, has a direct impact on daily life for a short period. Dust storms are periodic events over India, especially in northern regions. This study has been carried out to investigate the dust impacts on the aerosol characteristics over Dehradun (DDN) during pre-monsoon (March–June), 2012 using ground measurements, satellite observations and model simulations. The measurements illustrate the distinct monthly impact on the aerosol properties with maximum dust loading during May (aerosol optical depth at 500 nm (AOD500) = 0.72 ± 0.18) over DDN, which is confirmed with the Terra-MODIS (AOD550 = 0.70 ± 0.19) measurements. The major dust loading was recorded in aerosol measurements during May at the station, which permitting to examine the influence of dust transports on the aerosol characteristics. Spectral variation of AOD and Angstrom exponent (α) values displayed day to day variation of aerosol during dust episodes. Analysis of aerosol types and seven-day back-trajectories reveal the transportation of desert dust during May over DDN. The Optical Properties of Aerosols and Clouds (OPAC) model was used to compute the aerosol optical properties (e.g., Single scattering albedo (SSA) and asymmetry parameter (g)) and size distribution. The high values of SSA and g are indicating the dust loading in the atmosphere during May. Aerosol volume concentration at the coarse mode (geometric mean radii (RV) = 2.89 ± 0.027 µm) is found to be increased in the May, whereas decrement has been observed in the finer mode (RV = 0.16 ± 0.006 µm). The aerosol direct radiative forcing (ARF) was computed using Santa Barbara Discrete Ordinate Atmospheric Radiative Transfer (SBDART) model in the shortwave (SW) region (0.25–4.00 µm). The mean top of the atmosphere (TOA) and surface forcing come out to be –14.49 W m–2 and –53.29 W m–2 respectively in May. The mean net atmospheric radiative forcing (38.79 W m–2 maximum during May) corresponds to heating rate of ~1.06° K d–1 in the atmosphere.

The seasonal vertical distribution of the Saharan Air Layer and its modulation by the wind

Abstract. The Saharan Air Layer (SAL) influences large-scale environment from western Africa to eastern tropical Americas, by carrying large amounts of dust aerosols. However, the vertical distribution of the SAL is not well established due to a lack of systematic measurements away from the continents. This can be overcome by using the observations of the spaceborne lidar CALIOP onboard the satellite CALIPSO. By taking advantage of CALIOP's capability to distinguish dust aerosols from other types of aerosols through depolarization, the seasonal vertical distribution of the SAL is analyzed at 1° horizontal resolution over a period of 5 yr (June 2006–May 2011). This study shows that SAL can be identified all year round displaying a clear seasonal cycle. It occurs higher in altitude and more northern in latitude during summer than during winter, but with similar latitudinal extent near Africa for the four seasons. The south border of the SAL is determined by the Intertropical Convergence Zone (ITCZ), which either prohibits dust layers from penetrating it or reduces significantly the number of dust layers seen within or south of it, as over the eastern tropical Atlantic. Spatially, near Africa, it is found between 5° S and 15° N in winter and 5–30° N in summer. Towards the Americas (50° W), SAL is observed between 5° S and 10° N in winter and 10–25° N in summer. During spring and fall, SAL is found between the position of winter and summer not only spatially but also vertically. In winter, SAL occurs in the altitude range 0–3 km off western Africa, decreasing to 0–2 km close to South America. During summer, SAL is found to be thicker and higher near Africa at 1–5 km, reducing to 0–2 km in the Gulf of Mexico, farther west than during the other seasons. SAL is confined to one layer, of which the mean altitude decreases with westward transport by 13 m deg−1 during winter and 28 m deg−1, after 30° W, during summer. Its mean geometrical thickness decreases by 25 m deg−1 in winter and 9 m deg−1 in summer. Spring and fall present similar characteristics for both mean altitude and geometrical thickness. Wind plays a major role not only for the transport of dust within the SAL but also by sculpting it. During winter, the trade winds transport SAL towards South America, while in spring and summer they bring dust-free maritime air masses mainly from the North Atlantic up to about 50° W below the SAL. The North Atlantic westerlies, with their southern border occurring between 15 and 30° N (depending on the season, the longitude and the altitude), prevent the SAL from developing further northward. In addition, their southward shift with altitude gives SAL its characteristic oval shape in the northern part. The effective dry deposition velocity of dust particles is estimated to be 0.07 cm s−1 in winter, 0.14 cm s−1 in spring, 0.2 cm s−1 in summer and 0.11 cm s−1 in fall. Finally, the African Easterly Jet (AEJ) is observed to collocate with the maximum dust load of the SAL, and this might promote the differential advection for SAL parts, especially during summer.

Effect of dust load on the leaf attributes of the tree species growing along the roadside

Dust is considered as one of the most widespread air pollutants. The objective of the study was to analyse the effect of dust load (DL) on the leaf attributes of the four tree species planted along the roadside at a low pollution Banaras Hindu University (BHU) campus and a highly polluted industrial area (Chunar, Mirzapur) of India. The studied leaf attributes were: leaf area, specific leaf area (SLA), relative water content (RWC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), chlorophyll content (Chl), maximum stomatal conductance (Gs(max)), maximum photosynthetic rate (A (max)) and intrinsic water-use efficiency (WUEi). Results showed significant effect of sites and species for DL and the leaf attributes. Average DL across the four tree species was greater at Chunar, whereas, the average values of leaf attributes were greater at the BHU campus. Maximum DL was observed for Tectona grandis at Chunar site and minimum for Syzygium cumini at BHU campus. Across the two sites, maximum value of SLA, Chl and Gs(max) were exhibited by S. cumini, whereas, the greatest value of RWC, LNC, LPC, A (max) and WUEi were observed in Anthocephalus cadamba. A. cadamba and S. cumini exhibited 28 and 27 times more dust accumulation, respectively, at the most polluted Chunar site as compared to the BHU campus. They also exhibited less reduction in A (max) due to dust deposition as compared to the other two species. Therefore, both these species may be promoted for plantation along the roadside of the sites having greater dust deposition.

Retrieval of dust aerosols during night: improved assessment of long wave dust radiative forcing over Afro-Asian regions

Abstract. Several investigators in the past have used the radiance depression (with respect to clear-sky infrared radiance), resulting from the presence of mineral dust aerosols in the atmosphere, as an index of dust aerosol load in the atmosphere during local noon. Here, we have used a modified approach to retrieve dust index during night since assessment of diurnal average infrared dust forcing essentially requires information on dust aerosols during night. For this purpose, we used infrared radiance (10.5–12.5 μm), acquired from the METEOSAT-5 satellite (~ 5 km resolution). We found that the "dust index" algorithm, valid for daytime, will no longer hold during the night because dust is then hotter than the theoretical dust-free reference. Hence we followed a "minimum reference" approach instead of a conventional "maximum reference" approach. A detailed analysis suggests that the maximum dust load occurs during the daytime. Over the desert regions of India and Africa, maximum change in dust load is as much as a factor of four between day and night and factor of two variations are commonly observed. By realizing the consequent impact on long wave dust forcing, sensitivity studies were carried out, which indicate that utilizing day time data for estimating the diurnally averaged long-wave dust radiative forcing results in significant errors (as much as 50 to 70%). Annually and regionally averaged long wave dust radiative forcing (which account for the diurnal variation of dust) at the top of the atmosphere over Afro-Asian region is 2.6 ± 1.8 W m−2, which is 30 to 50% lower than those reported earlier. Our studies indicate that neglecting diurnal variation of dust while assessing its radiative impact leads to an overestimation of dust radiative forcing, which in turn result in underestimation of the radiative impact of anthropogenic aerosols.

The synoptic and optical characteristics of the harmattan dust spells over Nigeria

The synoptic and optical characteristic of days during severe dust spells of December 1998, January 2000, February 2001, March 2003 and January 2005 at Ilorin (8°19′N, 4°20′E), Nigeria are investigated in this study. For example, during the severe dust storm of 5 January 2005 a strong synoptic-scale ridge developed which caused a shift in the position of the anticyclone over the desert region. These conditions led to a higher pressure gradient, and in turn resulted in the generation of dust at the 900 hPa level and wind speeds of up to ∼13 m/s over the source region between Bilma (18°12′N, 12°55′E), Faya Largeau (17°55′N, 19°07′E) and Maiduguri (11°50′N, 13°09′E) during the dust spells. Spectral aerosol optical depth τaλ, Angstrom parameters (α440-500 nm and β) derived from sunphotometer measurements and horizontal visibility (km) were used to study aerosol optical characteristics during and after the winter “harmattan” dust days. It was found that the daily mean τa500 nm during the dust episodes ranged between 0.31 and 3.28, with an average of 0.98 ± 0.50. τaλ showed a pronounced temporal trend, with maximum dust loading during intense dust haze as τa500 nm increased from a daily average value of 0.68 ± 0.48 to values >2.0 during severe dust spells. Daily mean spectral variations of the Angstrom exponent α show striking changes especially at high τaλ, when coarse mode aerosol dominate the accumulation mode aerosol. During the dust spells of 1998–2005 average horizontal visibility was reduced to as low as 1.66 ± 0.34 km at Ilorin with an increase in average τa500 nm and β to ∼2.06 ± 0.48 and 1.87 ± 0.49, respectively. However, for cases with strong biomass burning aerosol τa500 nm = 0.67 with α and β = 1.02 ± 0.08 and 0.31 ± 0.06, respectively. In some cases, smoke particles mix with desert dust to produce intermediate values of α. A trajectory analysis at three different levels (200, 500 and 1000 magl) during a severe dust and biomass burning episode were further used to explain the transport of aerosols to Ilorin, Nigeria.

A potential climatic index for total Saharan dust: the Sun insolation

It is shown that the daily course of the total amount of dust in the atmosphere, based on the TOMS aerosol index (AI), is highly correlated (0.98) with the integrated daily solar insolation over the Sahara region for spatially and temporally averaged data. Moreover, the annual maximum is even reached nearly at the same day, i.e., the 17th (18th) June for the surface (top of the atmosphere) solar insolation, as compared to 21st June for the date of maximum atmospheric dust loading. Other factors like cloudiness, rainfall soil moisture, and wind probably play a more dominant role in smaller areas. The fact that on a very large scale, like the whole of the Sahara, the solar insolation becomes the one single forcing directly correlated with the total amount of dust in the atmosphere is suggesting a simple climatic index for the total dust loading in the atmosphere. This index is shown for the Saharan region only, while more studies are needed for other regions. The 3–4 day time‐lag between the maximum insolation and the maximum dust loading in the atmosphere is compared to about a one‐month delay with the maximum ground or air temperatures and may serve as an estimate to the surface response to the major forcing of the Sun. The maximum ground temperature, delayed to the 17th July, can be explained by the delay in the lagged‐heating of the deeper soil layers. The 3–4 day delay only with the Sun insolation is probably linked to the period in which the dust is maintained in the atmosphere until it is deposited. One application to the present finding may be for climate models, since such a high correlation for spatially and temporarily averaged data may be used as an integrated index for the total amount of Saharan dust and for potentially validating the complex model parameterizations in climate models.

Variability of aerosol parameters over Kanpur, northern India

Aerosol optical properties and the spectral behavior of the aerosol optical depth (AOD) over Kanpur, an urban‐industrial city in the Ganga basin, have been presented for the first time. Measurements by the ground‐based Aerosol Robotic Network (AERONET) during January 2001 to December 2003 show pronounced seasonal influence, with maximum dust loading during the premonsoon season (April–May). The distribution of AOD is found to be large with a mean value of 0.6 at 500 nm wavelength. The frequency distribution of the Ångström parameter α reveals two modes (α < 1 dominant dusty condition and α > 1 urban aerosols). Diurnal variations of AOD, water vapor content (WVC), and Ångström parameter show strong seasonal influence. Maximum variation of AOD is found during the monsoon season (presence of mixed types of aerosols), maximum variation of WVC is observed during the winter season (frequent changes in humidity and air pressure), and α shows maximum variations during the premonsoon (dust dominating the atmospheric optical conditions) season. The aerosol volume size distributions show two distinct modes, fine (geometric mean radii of 0.17 μm and standard deviation of 0.03) and coarse (geometric mean radii of 3.37 μm and standard deviation of 0.1), but during May–August (period of dust loading), a third mode (around 1–2 μm) appears because of hygroscopic growth of finer aerosols. The single‐scattering albedo (SSA) is found to increase with wavelength in the presence of dust and shows a reverse trend in dust‐free conditions. Refractive indices show the presence of dust as the main component during the premonsoon season and dominance of anthropogenic urban‐industrial aerosols during the winter season, when the optical state of the atmosphere is more absorbing. The aerosol parameters show distinct interannual variations, with increasing aerosol burden over the region. Aerosol loading over Kanpur is found to be controlled by the regional climatology.

Aerosol optical depth during episodes of Asian dust storms and biomass burning at Kwangju, South Korea

Spectral daily aerosol optical depths (τ a λ ) estimated from a multi-filter radiometer over Kwangju were analyzed from January 1999 to August 2001 (total of 277 days). Optical depths obtained showed a pronounced temporal trend, with maximum dust loading observed during spring time and biomass burning aerosol in early summer and autumn of each year. Result indicates that τ a501 nm increased from spring average of 0.45±0.02 to values >0.7 on 7 April 2000, and 13 April 2001. Daily mean spectral variations in the Ångström exponents α were also computed for various episode periods under consideration. A dramatic change in α value is noted especially at high aerosol optical depth when coarse mode aerosol dominates over the influence of accumulation-mode aerosol. High values of τ a λ associated with high values of α in early June and October are characteristics of smoke aerosol predominantly from biomass burning aerosol. Also, volume size distribution is investigated for different pollution episodes with result indicating that the peak in the distribution of the coarse mode volume radius and fine mode particles of dust and biomass-burning aerosol respectively increases as aerosol optical depth increases at Kwangju. Air-mass trajectory were developed on 7–8 April and 19–20 October, 2000 to explain the transport of Asian dust particle and biomass burning to Kwangju.

Blowing model for turbulent boundary-layer dust ingestion

Abstract : The rate at which dust is ingested into a turbulent boundary layer is deduced for the case of a semi-infinite flat plate and for the boundary layer behind a moving shock wave. Conventional turbulent boundary-layer theory is used. It is assumed that the local dust-ingestion rate corresponds to the 'blowing' rate at which the local unblown surface shear C(f,0) is reduced to a value C(f,t) that is just sufficient to maintain surface particles in a mobile state. It is further assumed that the particle-velocity equilibration distance is small compared with the local boundary-layer thickness. It is found that erosion rate and boundary-layer thickness parameters are weakly (logarithmically) dependent on C(f,O)/C(f,t) and the maximum dust loading within the boundary layer is approximately equal to one. The theoretical predictions for local erosion rate, boundary thickness, and dust density are compared with the limited experimental results of Hartenbaum and Ausherman for the semi- infinite flat plate and moving-shock cases, respectively. Agreement within about a factor of two is obtained. Further comparison with experiment is recommended.

The effect of dust on photosynthesis and its significance for roadside plants

Dust scraped from a car exhaust and ground to a particle size range of 1–10 μm was applied at measured rates to leaves of Viburnum tinus. Its effects on photosynthesis and leaf diffusion resistance were measured over a range of light intensities. Photosynthesis was reduced and this appeared to be due to shading when the upper surfaces of leaves were dusted, and to impeded diffusion when lower surfaces were dusted. These effects were observed with 5 to 10 g dust per m 2 leaf surface. The maximum dust load found on the leaves of shrubs on the central reserves of motorways was about 2 g m −2. Unless this deposit included much material too fine to be observed by light microscopy (i.e. < ca 0·5 μm) its effects on photosynthesis, mediated either by shading or by interference with diffusion, are likely to be small.