Search

Abstract: On February 14, 2011 Stardust-NExT (SN) flew by Comet Tempel 1, the target of the Deep Impact (DI) mission in 2005, obtaining dust measurements and high-resolution images of areas surrounding the 2005 impact site, and extending image coverage to almost two thirds of the nucleus surface. The nucleus has an average radius of 2.83±0.1km and a uniform geometric albedo of about 6% at visible wavelengths. Local elevation differences on the nucleus reach up to 830m. At the time of encounter the spin rate was 213° per day (period=40.6h) and the comet was producing some 130kg of dust per second. Some 30% of the nucleus is covered by smooth flow-like deposits and related materials, restricted to gravitational lows. This distribution is consistent with the view that the smooth areas represent material erupted from the subsurface and date from a time after the nucleus achieved its current shape. It is possible that some of these eruptions occurred after 1609 when the comet’s perihelion distance decreased from 3.5AU to the current 1.5AU. Much of the surface displays evidence of layering: some related to the smooth flows and some possibly dating back to the accretion of the nucleus. Pitted terrain covers approximately half the nucleus surface. The pits range up to 850m in diameter. Due to their large number, they are unlikely to be impact scars: rather they probably result from volatile outbursts and sublimational erosion. The DI impact site shows a subdued depression some 50m in diameter implying surface properties similar to those of dry, loose snow. It is possible that the 50-m depression is all that remains of an initially larger crater. In the region of overlapping DI and SN coverage most of the surface remained unchanged between 2005 and 2011 in albedo, photometric properties and morphology. Significant changes took place only along the edges of a prominent smooth flow estimated to be 10–15m thick, the margins of which receded in places by up to 50m. Coma and jet activity were lower in 2011 than in 2005. Most of the jets observed during the SN flyby can be traced back to an apparently eroding terraced scarp. The dust instruments detected bursts of impacts consistent with a process by which larger aggregates of material emitted from the nucleus subsequently fragment into smaller particles within the coma. [Copyright &y& Elsevier]

P/2010 A2 is an object on an asteroidal orbit that was observed to have an extended tail or debris trail in January 2010. In this work, we fit the outburst of P/2010 A2 with a conical burst model, and verify previous suspicions that this was a one-time collisional event rather than a sustained cometary outburst, implying that P/2010 A2 is not a new main belt comet driven by ice sublimation. We find that the best-fit cone opening angle is ∼40° to ∼50°, in agreement with numerical and laboratory simulations of cratering events. Mapping debris orbits to sky positions suggests that the distinctive arc features in the debris correspond to the same debris cone inferred from the extended dust. From the velocity of the debris, and from the presence of a velocity maximum at around 15 cm s-1, we infer that the surface of A2 probably has a very low strength (≲1 kPa), comparable to lunar regolith. [ABSTRACT FROM AUTHOR]

In this work, a novel technique is used to estimate the aerosol complex index of refraction of in situ collected samples. Samples of atmospheric particulate matter were collected in El Arenosillo, southern Spain, on polycarbonate filters during summer 2004 as part of an aerosol characterization campaign. These samples were analyzed for the volumetric absorption coefficient in the 320–800 nm spectral region and an estimation of the effective imaginary refractive index was made. The values of the imaginary part of the complex refractive index ranged between 0.0009–0.0215 at 800 nm and 0.0015–0.0114 at 320 nm. Little dependence on the wavelength was observed. Several intense and long lasting desert outbreaks were registered during the campaign and the complex refractive index almost doubles its value during these dust events. Finally, we present a comparison of data obtained in situ with columnar data obtained from the AERONET network. A correlation factor of 0.64 was obtained between both data, which gives an idea of how accurately the in situ ground data represent the total column. [Copyright &y& Elsevier]

In this paper we describe a statistical analysis of the inter-laboratory data summarized in Rosati et al. () to assess the performance of an analytical method to detect the presence of dust from the collapse of the World Trade Center (WTC) on September 11, 2001. The focus of the inter-lab study was the measurement of the concentration of slag wool fibers in dust which was considered to be an indicator of WTC dust. Eight labs were provided with two blinded samples each of three batches of dust that varied in slag wool concentration. Analysis of the data revealed that three of labs, which did not meet measurement quality objectives set forth prior to the experimental work, were statistically distinguishable from the five labs that did meet the quality objectives. The five labs, as a group, demonstrated better measurement capability although their ability to distinguish between the batches was somewhat mixed. This work provides important insights for the planning and implementation of future studies involving examination of dust samples for physical contaminants. This work demonstrates (a) the importance of controlling the amount of dust analyzed, (b) the need to take additional replicates to improve count estimates, and (c) the need to address issues related to the execution of the analytical methodology to ensure all labs meet the measurement quality objectives. [ABSTRACT FROM AUTHOR]

Context. It is unknown how far dust growth can proceed by coagulation. Obstacles to collisional growth are the fragmentation and bouncing barriers. However, in all previous simulations of the dust-size evolution, only the mean collision velocity has been considered, neglecting that a small but possibly important fraction of the collisions will occur at both much lower and higher velocities. Aims. We study the effect of the probability distribution of impact velocities on the collisional dust growth barriers. Methods. We assume a Maxwellian velocity distribution for colliding particles to determine the fraction of sticking, bouncing, and fragmentation, and implement this in a dust-size evolution code. We also calculate the probability of growing through the barriers and the growth timescale in these regimes. Results. We find that the collisional growth barriers are not as sharp as previously thought. With the existence of low-velocity collisions, a small fraction of the particles manage to grow to masses orders of magnitude above the main population. Conclusions. A particle velocity distribution softens the fragmentation barrier and removes the bouncing barrier. It broadens the size distribution in a natural way, allowing the largest particles to become the first seeds that initiate sweep-up growth towards planetesimal sizes. [ABSTRACT FROM AUTHOR]

Airborne PM1, PM2.5, PM5 and PM10 generated during writing with three types of chalk sticks on a board and particle size distribution of chalk dust fall during writing and dusting of board were studied by portable aerosol spectrometer and particle size analyzer. ‘Local Gypsum’ chalk led to the highest increase in airborne particulate matter while ‘Clean-Write’ the least during writing. About 10% of particles in chalk dust fall during writing were finest from: ‘Clean Write’ (0.5 µm) followed by ‘Abroad Quality’ (0.67 µm) and ‘Local Gypsum’ (1.15 µm), while 50% was finest in abroad quality (5.12 µm) followed by ‘Clean Write’ (6.36 µm) and ‘Local Gypsum’ (77.65 µm). In dusting samples, 10%, 50% and 90% of particles were finest in ‘Clean Write’ followed by ‘Abroad Quality’ and ‘Local Gypsum’ chalks. ‘Clean Write’ chalk produced least total amount of PM1, PM2.4 and PM5 and PM10 per unit time in dust fall during writing. Although short-term exposure to airborne fine chalk particles may be low in classrooms, several years of exposure may be a matter of concern. Purpose of this work was to provide data that would lead to measures for minimization of health risk due to chalk dusts in classrooms. [ABSTRACT FROM AUTHOR]

In this article were performed simulations of the collecting efficiency and the migration speed of the dust particles from gas, depending on the dust particlesf diameter (by classes of diameters between 0.1 and 60 ƒÊm) for a 3-field ESP used at the thermo]electric power plants. The 3]field ESPfs are often used in this industrial branch. For simulations it was used a performance program (ESPVI 4.0.a) for the study of the industrial ESPfs with plates and there were performed simulations in pure DC conditions and classic supplies of the fields, with and without dust layer on the collecting surfaces, with and without fieldsf rapping. It was found that the dust particles with diameters up to 10 ƒÊm (especially the ones below 2 ƒÊm) are collected the most difficult. [ABSTRACT FROM AUTHOR]

Abstract: Measured extinction spectra of six different components of desert dust have been used as input for a mineral dust retrieval algorithm for the Infrared Atmospheric Sounding Interferometer IASI based on Singular Vector Decomposition. The use of measured dust component extinction spectra rather than dust sample-based optical properties widely used in thermal infrared applications improves retrieval results significantly. Correlation between IASI derived dust optical depth (at 0.5 μm) and AERONET sun-photometer observations from six months over Northern Africa, the Arabian Peninsula and Asia improved from formerly 0.623 to now 0.757 while the root-mean-square difference decreased from 0.322 to now 0.174 and the bias decreased (in terms of its absolute value) from −0.181 to 0.003. The dynamically adjusted e−1 envelope of the deviation histogram between AERONET and IASI dust AOD at 0.5 μm is at 0.160 while 80% of all IASI observations are within AOD0.5 μm ± 0.2 of respective AERONET values. Spatial patterns of dust observations with the retrieval based on dust components compare very well with known features in terms of monthly mean gridded Aerosol Optical Depth. Although originally being developed for Northern Africa, the Arabian Peninsula and adjacent Oceans, the retrieval method performs equally well in Asian dust source regions and downwind areas. As a further strength it provides observations at day and night overpasses of the Metop spacecraft, thus twice daily. [Copyright &y& Elsevier]

Abstract: Household, stairs and entryway dust samples were collected from 16 houses distributed across Greater Cairo by using vacuum cleaner and sweeping methods during summer season of 2009. Lead (Pb), nickel (Ni), cadmium (Cd), aluminum (Al), iron (Fe), zinc (Zn), cobalt (Co), chromium (Cr) and copper (Cu) were measured in different dust particle sizes: <38 μm, >38–45 μm and >45–63 μm. The highest average concentrations of Pb, Ni, Cd, Co, Cu, and Cr in different particle sizes were found in entryway followed by household and stairs. Al, Fe and Zn concentrations followed the pattern of entryway > stairs > household. Pb, Ni, Cd, Zn, Co and Cr were found in significantly (p < 0.01) higher concentrations in dust of the small particle size (<38 μm), whereas Al, Fe and Cu were detected in significantly (p < 0.01) higher concentrations in dust of the large particle size (>45–63 μm). The average concentrations of the individual metals in dust of the small particle size (<38 μm) were 268, 196.4 and 254.49 μg gm−1 for Pb, 49.6, 43.5 and 46.66 μg gm−1 for Ni, 2.86, 2.15 and 2.71 μg gm−1 for Cd, 4340, 3796 and 2602 μg gm−1 for Al, 2860, 2200 and 2004 μg gm−1 for Fe, 209.25, 152.3 and 103.26 μg gm−1 for Zn, 4.1, 2.88 and 1.96 μg gm−1 for Co, 85.99, 74.06 and 83.17 μg gm−1 for Cr and 168.2, 156.5 and 122.02 μg gm−1 for Cu in entryway, stairs and household, respectively. The mean concentrations of Cu and Pb in the entryway, stairs and household dust exceeded the maximum permissible limit 100 μg gm−1 for Cu and Pb in soil. The highest concentrations of Pb, Cd, Co and Ni were found in urban areas, Al and Fe in the residential areas, and Cu, Zn and Cr in the residential near to industrial area. Significant positive correlation (p < 0.001) were found between the metal concentrations in household and entryway dust, indicating that the metals in household dust may be derived from outdoor sources in addition to dust generated within the house itself. The contribution of anthropogenic sources, especially traffic emission, to metal levels in household, entryway and stairs dust was reflected by the high values of enrichment factors for Pb, Cd, Zn and Cu and Ni and Cr in fine dust particle compared to the average crustal composition. Insignificant positive correlation coefficients were found between the concentrations of Pb and other metals in household dust. However, the correlation coefficients between the concentrations of Cd, Ni, Cr, Cu, Zn and Fe were statistically significant. [Copyright &y& Elsevier]

Abstract: Polarization-sensitive Mie-scattering lidars were installed for dust storm monitoring at Sainshand and Zamyn-Uud in the Gobi Desert and at the Mongolian capital city of Ulaanbaatar in 2007. We studied the temporal and spatial distributions and transportation of dust, elevated dust, biomass burning smoke, and anthropogenic aerosol by using lidar measurements from the end of 2007 to the first half of 2010. The study results show that the maximum height of dust layers over the Gobi Desert of Mongolia during dust event periods varied from 0.5 to 5.5 km above the ground level (AGL). The 95th percentile level of dust vertical distribution was found at 4 and 4.5 km for Zamyn-Uud and Sainshand, respectively. The averaged maximum height of dust layers during dust events was 2.0–2.2 km AGL at those Gobi sites. The lidar measurements also revealed transport of dust layers elevated in the atmosphere. Base heights of elevated dust layers varied from 0.5 to 2.5 km AGL, while maximum heights from 2.5 to 4.5 km AGL. Backward air trajectory analyses suggested source areas of the elevated dust that transported from other source regions to southeastern Mongolia. A detail study was conducted of the dust event in 19–20 May 2008. Hourly maximum dust concentrations of PM10 (PM2.5) reached 1139–1409 (384–404) μg m−3 during the dust event episode. Dust concentration of PM10 had high correlations with visibilities. Threshold winds for dust emission were determined at Sainshand and Zamyn-Uud. The lidar measurements at the three sites detected vertical profiles of biomass burning smoke and anthropogenic aerosol with top heights of 3–4 km AGL. [Copyright &y& Elsevier]

Abstract: The paper presents the results of a field test carried out in Gdańsk region between 01-01-2010 and 31-12-2010 in order to demonstrate equivalence of the Eberline FH 62-1 sampler to the reference gravimetric method of suspended PM10 dust measurement. The differences in PM10 dust concentration provided by both methods have been discussed for different seasons of the year. A method of estimation of the correction factors/correction equations has been described based on the European Union guide “Demonstration of Equivalence of Ambient Air Monitoring Methods. EC Working Group on Guidance for the Demonstration of Equivalence”. The results obtained from Eberline sampler are equivalent to the ones from gravimetric method, but after application of data correction. The investigation revealed different correction factors/correction equations for winter and summer season. The winter season is characterized by higher PM10 concentration and bigger discrepancies between both methods. A lack of equivalence has been found for PM10 dust concentration higher than 30μgm−3. [Copyright &y& Elsevier]

Assessment of spatial variation of fugitive dust sources, particularly road dust track-out from industrial sites and its subsequent re-suspension is difficult with fixed air quality monitoring stations given their sparse distribution and the highly localized nature of road dust. Mobile monitoring was employed to measure levels of road dust in the industrial area of the City of Hamilton, Ontario, Canada. Results of this monitoring were used in a Fugitive Dust Control workshop held for local stakeholders, where fugitive dust control solutions were presented. After the workshop, the City of Hamilton and cooperative industrial groups executed enhanced street cleaning and individual industries and facilities performed on-site control activities. Post-workshop mobile air monitoring was performed for comparison to the initial values to determine effectiveness of these approaches. A regression model testing the difference pre- and post-workshop yielded a statistically significant difference in PM10 measurements demonstrating improvement. The average value of PM10 prior to the workshop was 114μg/m3. Post-workshop the average value dropped to 73μg/m3. [Copyright &y& Elsevier]

The elements Cd, Cr, Cu, Mn, Ni, Pb and Zn were determined in dust samples collected from air conditioner (AC) filters from 15 commercial sites of Lahore using flame atomic absorption spectroscopy (FAAS). The elements Cr, Mn and Zn were also determined using instrumental neutron activation analysis (INAA). The results obtained showed that higher amounts of these metals were measured in these dust samples than normally found in soil. This was especially true for Cd, Cu, Pb and Zn. Generally the amounts of Cd, Cr and Mn did not vary throughout the city of Lahore but the amounts of the traffic related Cu, Pb and Zn elements had the more variable ranges of 30-140, 30-230 and 74-2810 mg/kg respectively. The concentrations obtained for Cr, Mn and Zn by INAA were found to be higher than those obtained using FAAS. Analysis of the data obtained showed the digestion procedure employed to be the possible cause for this occurrence. It was also found that Mn was being over-estimated by INAA due to the interference from the Mg peak. [ABSTRACT FROM AUTHOR]

The article looks at a study measuring mineral dust aerosols on the cold, high-latitude island of Heimay, near Iceland, which found that dust storm emissions were higher in the spring months commonly associated with glacial melting and flooding events in Iceland. The six years of data suggests that increasing icemelt in Iceland due to climate change will lead to greater deposition of iron-rich aerosol dusts in the geographical region, which will in turn impact the climate by absorbing solar radiation. It is also likely that the frequency of dust storms in other high-latitude and glacierized areas of the world will be similarly impacted by the escalation of global warming.

Our objectives were to determine relative contributions of diet and dust exposure from multiple microenvironments to PentaBDE body burden, and to explore the role of handwipes as a measure of personal exposure to PentaBDE. We administered a food frequency questionnaire and collected serum, dust (office, main living area, bedroom, and vehicle), and handwipe samples from 31 participants. ΣPentaBDEs (sum of BDE 28/33, 47, 99, 100, and 153) in handwipes collected in the office environment were weakly correlated with dust collected from offices (r = 0.35, p = 0.06) and bedrooms (r = 0.39, p = 0.04), but not with dust from main living areas (r = -0.05, p = 0.77) or vehicles (r = 0.17, p = 0.47). ΣPentaBDEs in serum were correlated with dust from main living areas (r = 0.42, p = 0.02) and bedrooms (r = 0.49, p = 0.008), but not with dust from offices (r = 0.22, p = 0.25) or vehicles (r = 0.20, p = 0.41). Our final regression model included variables for main living area dust and handwipes, and predicted 55% of the variation in serum ΣPentaBDE concentrations (p = 0.0004). Diet variables were not significant predictors of ΣPentaBDEs in serum. Our research suggests that exposure to dust in the home environment may be the most important factor in predicting PentaBDE body burden in North Americans, and potential exposure pathways may involve PBDE residues on hands. [ABSTRACT FROM AUTHOR]

The article provides information about a study to evaluate the impact of air distribution on efficiency of dust capture from metal grinding. It informs that sulfur hexafluoride was selected as a tracer gas to evaluate the pollutants emission in the process of grinding metal products. The results of the study show that local exhaust ventilation should be supported by the general ventilation wherever dust is emitted.

Wind-blown mineral dust derived from the crustal surface is an important atmospheric component affecting the Earth's radiation budget. Deposition of dust particles was measured in snow on Glacier No. 72, Mount Tuomuer, in the western Tian Shan, China. The mean concentration of dust particles (measured as the number of particles) with 0.57 < d < 26 μm in the snow pack is 706 X 103 mL-1, with a mean mass concentration of 3806 μg kg-1. Dust number size distribution showed the dominant particles with d < 2 μm, while volume size distributión showed single-modal structures having volume median diameters from 3 to 25? μm. Results were compared with data from other sites in the Tian Shan and various Northern Hemisphere sites. A backward trajectory model was also employed to examine the transport process of dust particles in this region. Most of the air mass originated from southern China, e.g., the Taklimakan Deserts in springtime, during the Asian dust period. Transport of dust from southern Chinese deserts to adjacent mountains is in agreement with a growing body of evidence on the importance of dust inputs to alpine regions. [ABSTRACT FROM AUTHOR]

We report ground-based follow-up observations of the exceptional source, ID 141, one of the brightest sources detected so far in the Herschel Astrophysical Terahertz Large Area Survey cosmological survey. ID 141 was observed using the IRAM 30 m telescope and Plateau de Bure interferometer (PdBI), the Submillimeter Array, and the Atacama Pathfinder Experiment submillimeter telescope to measure the dust continuum and emission lines of the main isotope of carbon monoxide and carbon ([C I] and [C II]). The detection of strong CO emission lines with the PdBI confirms that ID 141 is at high redshift (ɀ = 4.243 ± 0.001). The strength of the continuum and emission lines suggests that ID 141 is gravitationally lensed. The width (ΔVFWHM ∼ 800 km s-1) and asymmetric profiles of the CO and carbon lines indicate orbital motion in a disk or a merger. The properties derived for ID 141 are compatible with an ultraluminous (LFIR ∼ (8.5 ± 0.3) x 1013 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. Lʘ, where μL is the amplification factor), dense (n ≈ 104 cm-3), and warm (Tkin ≈ as 40 K) starburst galaxy, with an estimated star formation rate of (0.7-1.7) x 104 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. Mʘ yr-1. The carbon emission lines indicate a dense (n ≈ 104 cm-3) photon-dominated region, illuminated by a far-UV radiation field a few thousand times more intense than that in our Galaxy. In conclusion, the physical properties of the high-ɀ galaxy ID 141 are remarkably similar to those of local ultraluminous infrared galaxies. [ABSTRACT FROM AUTHOR]

Road dust emissions are considered to be a major source of airborne particulate matter (PM). This is particularly true for industrial environments, where there are high resuspension rates of deposited dust. The calculation of roads as PM emission sources has mostly focused on the consequences of this emission, viz. the increase in PM concentrations. That approach addresses the atmospheric transport of the emitted dust, and not its primary origin. In contrast, this paper examines the causes of the emission. The study is based on mass conservation of the dust deposited on the road surface. On the basis of this premise, estimates of emission rates were calculated from experimental data obtained in a road in a ceramic industrial area. [Copyright &y& Elsevier]

The article presents a study on the significance of an erodible material's surface size distribution towards Dust Entrainment and Deposition scheme (DEAD) improvement. It mentions that the importance of its modification is showed through the realization of comparative and sensitivity analyses in zero dimensions (0-D) and three dimensions (3-D). It also notes its good representation of dust source emission and small variations in both dimensions.

Purpose: The urban sedimentary system is attracting increasing interest because of its role in influencing air and water quality. A large amount of road-deposited sediment (RDS) lies on the road network of Prince George, a city of about 80,000 people, in British Columbia, Canada. The objectives of this study were: (1) to determine the total mass of RDS within the city, and how this varied over time and space; and (2) to determine the temporal and spatial variations in the particle-size fractions of the RDS. Materials and methods: Samples of RDS were collected using a grid network during two different time periods in the snow-free season in 2009. Composite samples for each grid ( n = 46) were fractionated into five grain-size classes (>500, 250-500, 125-250, 63-125, <63 μm) using stainless steel sieves. Fractionated sediment samples were weighed to obtain a mass for each size class for each grid cell. Results and discussion: The total amount of RDS (all particle-size fractions) in the city of Prince George was estimated to be 746 × 10 and 204 × 10 kg for the summer and fall 2009 sampling periods, respectively. Based on a total road length of 1,030 km within the sampled area of the city, this equates to an average of 724 and 198 kg per km of road, for the summer and fall sampling periods, respectively. The RDS was dominated by the >500-μm fraction, and there was a trend of decreasing amounts (by mass) for the finer particle-size fractions. In terms of the most important particle-size fraction from an air and water quality perspective, the <63-μm particle-size fraction accounted for, on average, 6.5% and 4.8% of the total RDS mass for the summer and fall 2009 sampling periods, respectively; it is estimated that an additional approximately 2% was lost to the air during sample collection, and thus values may be closer to 9% and 7%, respectively. This equates to averages of between 47-61 and 10-13 kg per km of road for the summer and fall periods, respectively. Total amounts of RDS were greatest in the city centre, compared to the outlying areas, reflecting the greater density of roads in the former, although there were some hotspots which may reflect land use activities such as light-industry and pulp and paper mills. Conclusions: These findings have implications for air and water quality in the city and surrounding area, including the role of RDS in contributing to airborne fine particulates (i.e. PM and PM) and the fine-grained sediment (<63 μm) transported within storm sewers to receiving waterways, such as the Fraser and Nechako Rivers. [ABSTRACT FROM AUTHOR]

This paper gives a brief review of existing methods of measuring the resistivity of a layer of dust collected in electric filters and indicates their drawbacks. [ABSTRACT FROM AUTHOR]

Objective: Concentrations of polycyclic aromatic hydrocarbons (PAHs) in street dust in the Tamale metropolis, Ghana, have been measured in this study. Results: The concentrations of the various types of PAHs identified in street dust samples from high vehicular traffic density in the metropolis are as follows: naphthalene, 10,000 μg/kg; acenaphthylene, 13,000 μg/kg; acenaphthene, 76,000 μg/kg; fluorene, 18,900 μg/kg; phenanthrene, 40,000 μg/kg; anthracene, 21,000 μg/kg; fluoranthene, 35,200 μg/kg; pyrene, 119,000 μg/kg; benzo[a]anthracene, 17,700 μg/kg; chrysene, 10,600 μg/kg; benzo[k]fluoranthene, 18,700 μg/kg; benzo[a]pyrene, 10,900 μg/kg and benzo[g, h, i]perylene, 21,000 μg/kg. Calculation of the phenanthrene/anthracene ratio indicated that the PAHs identified in this study were from vehicular fallout as the ratio was less than 10. Conclusion: It is clear from the results of the study that road users in the Tamale metropolis, especially hawkers, are exposed to the harmful effects of PAHs, and this suggests the need for the establishment of mitigation measures by the regulatory agencies. [ABSTRACT FROM AUTHOR]

Abstract: Hourly mean time series of dust concentration (PM10) measured at 3m high and a sonic-anemometer measured momentum and kinematic heat fluxes at 8m high above the surface have been obtained from a 20-m monitoring tower located at Erdene in the Asian dust source region of Mongolia for years of 2009 and 2010. These time series were used to identify dust events and to develop optimal regression equations for the dust concentration of dust events with the friction velocity (u *) and the convective velocity scale (w *). In total, 68 dust events were identified in 2009 (except for November) and 43 dust events for the period from March to August in 2010. The duration of each dust event ranged from 3–29h in 2009 and 5–35h in 2010. The maximum hourly mean dust concentration of the dust event was found to be 4,107μg m−3 in May in 2009 and 4,708μg m−3 in March in 2010 while a minimum of 251μg m−3 in August in 2009 and 662μg m−3 in June in 2010. The optimal regression equation for the dust concentration (C) of dust events was found to have the form of log C=a+b(u* +cw*)n, where a, b, c and n are constants that vary month to month. The convective velocity scale (w*) that has not been taken into account in most dust modelings was found to enhance the dust concentration of dust events during the cold period from December to March when the soil temperature was below the freezing level for both the stable (w* <0) and unstable (w* >0) stratifications, whereas the convective velocity caused a reduction in the dust concentrations during the warm period from April to October, suggesting the importance of the convective velocity to estimate dust concentration of dust events. [Copyright &y& Elsevier]

Vacuum samples were collected from 1025 randomly selected urban Canadian homes to investigate bioaccessible Pb (PbS) concentrations in settled house dust. Results indicate a polymodal frequency distribution, consisting of three lognormally distributed subpopulations defined as "urban background" (geomean 58 μg g-1), "elevated" (geomean 447 μg g-1), and "anomalous" (geomean 1730 μg g-1). Dust PbS concentrations in 924 homes (90%) fall into the "urban background" category. The elevated and anomalous subpopulations predominantly consist of older homes located in central core areas of cities. The influence of house age is evidenced by a moderate correlation between house age and dust PbS content (R² = 0.34; n = 1025; p < 0.01), but it is notable that more than 10% of homes in the elevated/anomalous category were built after 1980. Conversely, the benefit of home remediation is evidenced by the large number of homes (33%) in the background category that were built before 1960. The dominant dust Pb species determined using X-ray Absorption Spectroscopy were as follows: Pb carbonate, Pb hydroxyl carbonate, Pb sulfate, Pb chromate, Pb oxide, Pb citrate, Pb metal, Pb adsorbed to Fe- and Al-oxyhydroxides, and Pb adsorbed to humate. Pb bioaccessibility estimated from solid phase speciation predicts Pb bioaccessibility measured using a simulated gastric extraction (R² = 0.85; n = 12; p < 0.0001). The trend toward increased Pb bioaccessibility in the elevated and anomalous subpopulations (75% ± 18% and 81% ± 8%, respectively) compared to background (63% ± 18%) is explained by the higher proportion of bioaccessible compounds used as pigments in older paints (Pb carbonate and Pb hydroxyl carbonate). This population-based study provides a nationally representative urban baseline for applications in human health risk assessment and risk management. [ABSTRACT FROM AUTHOR]

A qualitative understanding of the particles in dust and their sources helps to identify ways to reduce the accumulation of dust within historic houses. Knowing the possible sources of dust helps to suggest preventive steps. Simple low-technology methods enable rapid identification of dust deposits and require little specialist equipment. Dust samples can be collected on sticky surfaces for examination with a hand lens or microscope. The size of particles and fibres, and amount of surface coverage, can be estimated roughly using a graticule or coverage chart. An atlas of common dust components aids identification of soil dust, soot, insects, plant fragments, hair, skin, paint/plaster, clothing fibres, paper, food and mould. A mixture of fine dust is resolvable into a range of particle and fibre types. Long exposures of sticky samplers, with an estimate of the area covered by dust, indicate the rate of deposition and suggest the cleaning frequency necessary to prevent negative visitor reactions. The atlas lists suppliers and sources of information. [ABSTRACT FROM AUTHOR]

As a result of a tragic industrial accident, a highly alkaline red mud sludge inundated settlements and agricultural areas near Ajka, Hungary on October 4, 2010. One of the major concerns about the aftermaths of the accident is the potential health effects of vast amounts of fugitive dust from red mud sediment. Thus, we studied the chemical and physical properties of particles of red mud and its respirable fugitive dust, and performed toxicity measurements. Under unfavorable meteorological conditions dry red mud sediment could emit very high amounts of respirable alkaline particles into the air. The number size distribution of fugitive dust peaks above 1 μm aerodynamic diameter; therefore, its inhalation is unlikely to affect the deep regions of the lungs. No significant mineralogical or elemental fractionation was observed between the sediment and dust, with the major minerals being hematite, cancrinite, calcite, and hydrogarnet. Although the high resuspension potential and alkalinity might pose some problems such as the irritation of the upper respiratory tract and eyes, based on its size distribution and composition red mud dust appears to be less hazardous to human health than urban particulate matter. [ABSTRACT FROM AUTHOR]

The impact of dust emission on air quality is a significant health and environmental concern. Accurately determining the source (natural versus anthropogenic) and load of dust is an important component of any mitigation effort. We develop an approach to assess dust emission potential based on study of Nellis Dunes Recreation Area, a popular off-road vehicle area close to Las Vegas, Nevada. A mapping approach to assess dust emission potential is presented, which may serve as a template to assess other areas for this hazard. A 1:10,000 map delineating units based upon surficial characteristics affecting dust emission (e.g., soil texture, rock cover, surface crusts, and vegetation) was created. Seventeen surface units are grouped into four major classes (sand, silt and clay, rock covered, and active drainages). A >500 km network of trackways was digitized into a geographic information system (GIS) to determine the distribution of tracks across surface types to assess the density of disturbance. Wind-erosion measurements and off-road experiments using different vehicles (four-wheeler, motorcycle, and dune buggy) were performed on the various surface types to assess the amount of dust generated. Dust emission risk maps for Nellis Dunes Recreation Area are presented for two types of processes: off-road vehicular (ORV) activity and wind erosion. Highest dust emissions for ORV activity occur on map units composed of silt and clay, and on desert pavements. These areas can also produce large amounts of dust through natural wind erosion when disturbed. In contrast, the sandy units produce high emissions through natural wind erosion, and therefore limiting ORV use in those areas provides no benefit to air quality. [ABSTRACT FROM AUTHOR]

This study categorizes various dust weather types by means of satellite remote sensing over central Asia. Airborne dust particles can be identified by satellite remote sensing because of the different optical properties exhibited by coarse and fine particles (i.e. varying particle sizes). If a correlation can be established between the retrieved aerosol optical properties and surface visibility, the intensity of dust weather can be more effectively and consistently discerned using satellite rather than surface observations. In this article, datasets consisting of collocated products from Moderate Resolution Imaging Spectroradiometer Aqua and surface measurements are analysed. The results indicate an exponential relationship between the surface visibility and the satellite-retrieved aerosol optical depth, which is subsequently used to categorize the dust weather. The satellite-derived spatial frequency distributions in the dust weather types are consistent with China's weather station reports during 2003, indicating that dust weather classification using satellite data is highly feasible. Although the period during the springtime from 2004 to 2007 may be not sufficient for statistical significance, our results reveal an increasing tendency in both intensity and frequency of dust weather over central Asia during this time period. [ABSTRACT FROM AUTHOR]

Abstract: Perfluoroalkyl compounds (PFCs) were measured in dust from Australian, Canadian, French, German, Kazahkstani, Thai, UK, and US homes, and UK cars, classrooms, and offices. Most PFCs were significantly lower in Kazahkstan and Thailand than elsewhere; 2-(N-methylperfluoro-1-octanesulfonamido)-ethanol (MeFOSE) and 2-(N-ethylperfluoro-1-octanesulfonamido)-ethanol (EtFOSE) were significantly lower in Canada than in the UK and the US; perfluoro-1-hexanesulfonate (PFHxS) was significantly lower in Canada than in the UK, and N-ethylperfluoro-1-octanesulfonamide (EtFOSA) was significantly higher in Australia than in the UK. High EtFOSA concentrations in some samples may be consistent with its use as an insecticide. Perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), PFHxS, and MeFOSE were significantly higher in classrooms than in cars, homes, and offices; N-methylperfluoro-1-octanesulfonamide (MeFOSA) was significantly lower in classrooms than in homes and offices, and perfluoro-1-octanesulfonamide (FOSA) was significantly lower in classrooms than in cars, homes, and offices. While homes are usually the most important vector of dust exposure (typically >60%), offices and classrooms make important contributions. While diet is usually the main exposure pathway for UK adults and children (~1–6years) for PFOS, PFOA, and PFHxS; dust ingestion can be significant under high dust ingestion scenarios. Even under high-end exposure scenarios for dust and diet, PFOS and PFOA exposures are well within the European Food Safety Authority tolerable daily intakes. [ABSTRACT FROM AUTHOR]

African dust (AD) contributions to particulate matter (PM) levels may be reported by Member States to the European Commission during justification of exceedances of the daily limit value (DLV). However, the detection and subsequent quantification of the AD contribution to PM levels is complex, and only two measurement-based methods are available in the literature: the Spanish-Portuguese reference method (SPR), and the Tel Aviv University method (TAU). In the present study, both methods were assessed. The SPR method was more conservative in the detection of episodes (71 days identified as AD by SPR, vs 81 by TAU), as it is less affected by interferences with local dust sources. The mean annual contribution of AD was lower with the TAU method than with SPR (2.7 vs 3.5 ± 1.5 μg/m³). The SPR and TAU AD time series were correlated with daily aluminum levels (a known tracer of AD), as well as with an AD source identified by the Positive Matrix Factorization (PMF) receptor model. Higher r² values were obtained with the SPR method than with TAU in both cases (r² = 0.72 vs 0.56, y = 0.05x vs y = 0.06x with aluminum levels; r² = 0.79 vs 0.43, y = 0.8x vs y - 0.4x with the PMF source). We conclude that the SPR method is more adequate from an EU policy perspective (justification of DLV exceedances) due to the fact that it is more conservative than the TAU method. Based on our results, the TAU method requires adaptation of the thresholds in the algorithm to refine detection of low-impact episodes and avoid misclassification of local events as AD. [ABSTRACT FROM AUTHOR]

We used a single-particle soot photometer (SP2) to measure the mass of individual black carbon (BC) particles down to ∼ 0.5 fg by means of laser-induced incandescence with an intra-cavity, continuous-wave laser. The incandescence of nine different types of BC samples was investigated to provide a physical basis for choosing appropriate BC materials for SP2 calibration. We estimated the vaporization temperatures of these BC samples from the spectral dependence of incandescence at the limit of the small size parameter x, for which spectral dependence of emissivity is known a priori. The vaporization temperatures differed by less than 2.2% among the samples. For the x < 1 regime of particle size, the peak amplitude of the incandescence signal measured by the SP2 was linearly proportional to the particle mass. The slopes of such linear proportionality were positively correlated with | (m2-1)/(m2+2)|, where the m is the complex refractive index of the BC particle. For particles in which x > 1, the rate of increase in the peak amplitude of the incandescence signal with increasing particle mass was negatively correlated with the compactness of particle shape, consistent with the theoretical prediction of emissivity, which accounts for particle shape. The incandescence-BC mass relationships were similar between fullerene soot and ambient soot sampled in Tokyo, thus suggesting that fullerene soot is a suitable calibration standard for SP2 measurements of ambient soot. [ABSTRACT FROM AUTHOR]

Abstract: There has been a long-running debate over the position of the Pliocene-Pleistocene boundary, i.e. 1.8Ma versus 2.6Ma. This study presents litho- and pedo-stratigraphic characteristics, grain size, magnetic susceptibility, and dust sedimentation rates for ‘red clay’-loess sequences over northern China, in order to assess the drastic climatic event(s) recorded in the quasi-continuous eolian deposits, and to readdress the position of the Pliocene-Pleistocene boundary. In complete Chinese loess sequences, 33 soil-loess couplets have been identified and labeled with Si-Li system. Traditionally, the base of Chinese loess has been designated at the bottom of loess unit L33. However, a typical loess layer within the uppermost ‘red clay’ is identified and formally designated here as L34 and the soil unit between L33 and L34 as S33, which lowers the basal age of Chinese loess from 2.6Ma to ∼2.8Ma. Although the Neogene ‘red clay’ and the overlying Quaternary loess are both of windblown origin, they have quite different pedogenic characteristics. The loess consists of alternating reddish soil and yellowish loess layers, while the ‘red clay’ is composed of soils with much redder colour and carbonate nodule layers. In general, the “red clay” has been subjected to stronger pedogenic processes than the overlying loess, and can be regarded as an extremely thick soil complex. The alternation of loess and soils reflects large-scale oscillations between glacial and interglacial conditions, whereas the well-developed ‘red clay’ deposition indicates a relatively stable climate condition. At ∼2.8Ma, shortly before the Gauss/Matuyama boundary, the eolian sequences show a sedimentary transition from the well-weathered ‘red clay’ to the alternating loess and paleosol deposits, accompanied by coarser particle size, increased dust accumulation rates, and change of magnetic susceptibility signature. These indicate a large climatic shift from long-lasting warm-humid conditions to large-amplitude cold-dry and warm-humid fluctuations around 2.8Ma, and a dramatic increase in aridity over the dust source region. In contrast, such a drastic event is not identified around the top of the Olduvai event or at any other time of the past 7.7Ma. As the Gauss/Matuyama boundary offers a sound foundation for global time correlation and chronostratigraphic classification, these results still support the proposal of ICS and INQUA, that the conventional Pliocene-Pleistocene boundary should be lowered from 1.8Ma to 2.6Ma. [Copyright &y& Elsevier]

During late 2002 and early 2003, southern Australia was in the grip of drought and experienced one of its most active dust storm seasons in the last 40 years with large dust plumes frequently advected over the adjacent Southern Ocean. We use meteorological records of dust activity, satellite ocean color, and aerosol optical depth data and dust transport modeling to investigate the transport and deposition of mineral dust from Australia over adjacent ocean regions and to correlate it with biological response in phytoplankton standing stock as measured by chlorophyll a concentration in 5 degree latitude bands from 40° to 60°S. Seasonal maxima in mean surface chlorophyll a of -0.5 mg m3 were not achieved until late January 2003 or during February in the more southerly bands, which when compared with a 9 year satellite mean climatology suggests the phenology of the bloom in 2002-2003 was atypical. Contemporaneous field data on CO2 fugacity collected on transects between Tasmania and Antarctica show that significant atmospheric CO2 drawdown occurred as far south as 60°S during February 2003. Our results provide strong evidence for a large-scale natural dust fertilization event in the Australian sector of the Southern Ocean and highlight the importance of dust-derived nutrients in the marine carbon cycle of the Southern Ocean. [ABSTRACT FROM AUTHOR]

Soil dust deposition is recognized as a major source of iron to the open ocean at global and regional scales. However, the processes that control the speciation and cycle of iron in the surface ocean after dust deposition are poorly documented mainly due to the logistical difficulties to investigate in-situ, natural dust events. The development of clean mesocosms in the frame of the DUNE project (a DUst experiment in a low Nutrient low chlorophyll Ecosystem) was a unique opportunity to investigate these processes at the unexplored scale of one dust deposition event. During the DUNE1 mesocosm seeding experiment, iron stocks (dissolved and particulate concen trations in the water column) and fluxes (export of particulate iron in sediment traps) were followed during 8 days after an artificial dust seeding mimicking a wet deposition of 10 gm-2. The addition of dust at the surface of the mesocosms was immediately followed by a decrease of dissolved iron [dFe] concentration in the 0-10m water column. This decrease was likely due to dFe scavenging on settling dust particles and mineral organic aggregates. The scavenging ratio of dissolved iron on dust particles averaged 0.37±0.12 nmolmg-1. Batch dissolution experiments conducted in parallel to the mesocosm experiment showed a increase (up to 600%) in dust iron dissolution capacity in dust-fertilized waters compared to control conditions. This study gives evidences of complex and unexpected effects of dust deposition on surface ocean biogeo-chemistry: (1) large dust deposition events may be a sink for surface ocean dissolved iron and (2) successive dust deposition events may induce different biogeochemical responses in the surface ocean. [ABSTRACT FROM AUTHOR]

This study evaluated the relationship between the real-time concentration measurements of inhalable particles whose diameters were less than 10 μ m, from a light scattering monitor and a beta gauge monitor, at various instantaneous relative humidities. This work demonstrated that the mean inhalable particle concentrations as measured by the light scattering monitor were higher than those of the manual sampler, such that a factor of 0.74 was employed to adjust the light scattering monitor for inhalable particle concentration measurements. The mean inhalable particle concentrations determined by the beta gauge monitor at a low relative humidity setpoint correlated well with those obtained by the manual sampler. The real-time inhalable particle concentration of the adjusted light scattering monitor was further compared to those of the beta gauge monitor to investigate the effect of instantaneous relative humidity on the mass readings of the automatic monitors. The results demonstrated that the estimated concentration measurements by the adjusted light scattering monitor should be re-calibrated in real-time to improve the accuracy of the inhalable particle concentrations at various instantaneous relative humidities. [ABSTRACT FROM AUTHOR]

In the present work, we studied the dust deposition characteristics on suspended insulators under the simulated sandstorm conditions in a laboratory. Based on the simulation experiments, the basic dust deposition and distribution characteristics were studied, such as the difference of deposition among sheds at different locations, the difference of deposition between large and small sheds, the relationship between deposition quantity and flow speed of air and dust as well as the relationship between deposition quantity and experimental duration. Our study provides important insights for more advanced studies on this topic in the future. [ABSTRACT FROM AUTHOR]

Despite much speculation, the principal factors controlling concentrations of polycyclic aromatic hydrocarbons (PAH) in settled house dust (SHD) have not yet been identified. In response to recent reports that dust from pavement with coal-tar-based sealcoat contains extremely high concentrations of PAH, we measured PAH in SHD from 23 apartments and in dust from their associated parking lots, one-half of which had coal-tar-based sealcoat (CT). The median concentration of total PAH (T-PAH) in dust from CT parking lots (4760 μg/g, n = 11) was 530 times higher than that from parking lots with other pavement surface types (asphalt-based sealcoat, unsealed asphalt, concrete [median 9.0 μg/g, n = 12]). T-PAH in SHD from apartments with CT parking lots (median 129 μg/g) was 25 times higher than that in SHD from apartments with parking lots with other pavement surface types (median 5.1 μg/g). Presence or absence of CT on a parking lot explained 48% of the variance in log-transformed T-PAH in SHD. Urban land-use intensity near the residence also had a significant but weaker relation to T-PAH. No other variables tested, including carpeting, frequency of vacuuming, and indoor burning, were significant. [ABSTRACT FROM AUTHOR]

Aerosol levels at Mediterranean Basin are significantly affected by desert dust that is eroded in North Africa and is transported northwards. This study aims to assess the performance of the Dust REgional Atmospheric Model (BSC-DREAM8b) in the prediction of dust outbreaks near the surface in Eastern Mediterranean. For this purpose, model PM10 predictions covering a 7-year period and PM10 observations at five surface monitoring sites in Greece are used. A quantitative criterion is set to select the significant dust outbreaks defined as those when the predicted PM10 surface concentration exceeds 12 μg/m3. The analysis reveals that significant dust transport is usually observed for 1-3 consecutive days. Dust outbreak seasons are spring and summer, while some events are also forecasted in autumn. The seasonal variability of dust transport events is different at Finokalia, where the majority of events are observed in spring and winter. Dust contributes by 19-25% to the near surface observed PM10 levels, which can be increased to more than 50 μg/m3 during dust outbreaks, inducing violations of the air quality standards. Dust regional modeling can be regarded as a useful tool for air quality managers when assessing compliance with air quality limit values. [ABSTRACT FROM AUTHOR]

Abstract: The enzyme preparation industry has been developing rapidly in recent years whose products, such as food and detergents, benefit human life in many ways. However, enzyme particles emitted during feed-in processes at workplaces can impose great risks to the workers. Local exhausts are often used to improve the indoor air quality under such conditions. To design local exhausts efficiently, information about the movement and transport of enzyme particles in workplace is required. With Computational Fluid Dynamics (CFD), the workplace enzyme particle level can be predicted from given particle source emission factors. However, no research at present relates to the determination of this emission factor with respect to particle contaminant at micro-level. We used Elutriation Dust Column (EDC) experimental method to determine enzyme particle emission factors at workplace. The principle and operation of EDC were described in detail. By introducing the particle source emission factor obtained from EDC experiment into CFD calculation, enzyme concentration level was calculated for a workplace having one feed-in machine operated intermittently. Good agreements were observed between the calculated enzyme particle concentration distributions and onsite collected sample results. It concludes that EDC can be used to predict particle emission rate in the feed-in operation and may offer a way to predict enzyme particle emission rate in similar feed-in operation processes. [Copyright &y& Elsevier]

One of the most important factors that determine the transported dust effect on the atmosphere is its vertical distribution. In this study the vertical structure of North African dust and stratiform low clouds is analyzed over the Atlantic Ocean for the 2006-2007 boreal winter (December- February) and boreal summer of 2006 (June-August). By using the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) backscatter measurements over the dust routes, we describe the differences in dust transport between the seasons. We show a bi-modal distribution of the average dust plumes height in both seasons (it is less clear in the winter). The higher plume top height is 5.1±0.4 km, near the African coast line in the summer and 3.7±0.4 km in the winter. The lower plume merges with the marine boundary layer, in both seasons. Our study suggests that a significant part of the dust is transported near and within the marine boundary layer and interacts with low stratiform clouds. [ABSTRACT FROM AUTHOR]

The formation and release of polybrominated dibenzo-p- dioxins and dibenzofurans (PBDD/Fs) from the incineration of electronic wastes (e-waste) that contain brominated flame retardants (BFRs) are a concern. However, studies on the determination of PBDD/Fs in environmental samples collected from e-waste recycling facilities are scarce. In this study, 11 2,3,1,8-substituted PBDD/Fs and 10 polybrominated diphenyl ether (PBDE) congeners were determined in electronic shredder waste, workshop-floor dust, soil, and leaves (of plants on the grounds of the facility) from a large-scale e-waste recycling facility and in surface soil from a chemical-industrial complex (comprising a coke-oven plant ,a coal-fired power plant and a chlor-alkali plant) as well as agricultural areas in eastern China. Total PBDD/F concentrations in environmental samples were in the range of 113-818 pg/g dry wt (dw) for leaves, 392-18500 pg/g dw for electronic shredder residues, 716-800000 pg/g dw for soil samples, end 89600-143000 pg/g dw for workshop-floor dust from the e-waste recycling facility and in a range from nondetect (NO) to 427 pg/g dw in soil from the chemical-industrial complex. The highest mean concentrations of total PBDD/Fs were found in soil samples and workshop-floor dust from the e-waste recycling facility. The dioxin-like toxic equivalent (measured as TEQ) concentrations of PBDD/Fs were greater than the TEQs of polychlorinated dihenzo-p-dioxins and dibenzofurans (PCDD/ Fs) reported in our previous study for the same set of samples. The concentrations of PBDFs were several orders of magnitude higher than the concentrations of PBDDs in samples from the e-waste facility or from soil from the chemical-industrial complex. A significant correlation was found between the concentrations of ΣPBDD/Fs and ΣPBDEs (r = 0.769, p < 0.01) and between ΣPBDD/Fs and the previously reported ΣPCDD/F concentrations (r = 0.805, p < 0.01). The estimated daily human intakes of TEQs contributed by PBDD/Fs via soil/dust ingestion and dermal exposures in e-waste recycling facilities were higher than the intakes of TEQs contributed by PCDD/Fs, calculated in our previous study. [ABSTRACT FROM AUTHOR]

The contribution of animal activity to dust concentration in a pig barn, was evaluated through the continuous monitoring of animal activity. PM10 concentrations were measured during a three months observation period, from April to July, in a mechanically ventilated fattening room in Northern Italy. Pigs of 60kg and with a mean age of 150 days were fed with liquid feed and were lodged on concrete fully slatted floor. PM10 concentration was monitored continuously by a dust sampler. From April 12 at 13:42 until April 13 at 15:09, 33 pigs housed in two of the 16 pens of the barn were monitored using a video camera placed at the height of 5m above the pen floor. A comparison of data related to dust measurement and to activity index was performed on the hours of recorded images. PM10 concentration reached maximum values at feeding times, during feed release and with lights turned on. An increase in dust concentration took place within an hour after increased animal activity. PM10 concentration decreased until it reached the nocturnal mean concentration (316μgm−3) after 1h from feeding time. As expected, correlation analysis showed that particulate matter concentration was associated with ventilation rate (70%, P <0.001), with relative humidity (−93%, P <0.001), with inside and outside temperatures which determine ventilation rate a priori, and finally with animal activity (99%, P <0.001). These results confirmed the strong association that exists between animal activity and particulate matter concentration in animal houses. An increase in PM10 concentration from 316μgm−3 (the mean value of dust levels was observed at night when the recorded animal activity showed the lowest values) to 624μgm−3 corresponded to the dust raised by 343 animals (with an increase in animal activity of 0.018 units), in a mechanically ventilated barn with fattening pigs fed with liquid feed, and lodged on a fully slatted concrete floor. [Copyright &y& Elsevier]

Abstract: Galileo was the first artificial satellite to orbit Jupiter. During its late orbital mission the spacecraft made two passages through the giant planet’s gossamer ring system. The impact-ionization dust detector on board successfully recorded dust impacts during both ring passages and provided the first in-situ measurements from a dusty planetary ring. During the first passage—on 5 November 2002 while Galileo was approaching Jupiter—dust measurements were collected until a spacecraft anomaly at 2.33R J (Jupiter radii) just 16min after a close flyby of Amalthea put the spacecraft into a safing mode. The second ring passage on 21 September 2003 provided ring dust measurements down to about 2.5R J and the Galileo spacecraft was destroyed shortly thereafter in a planned impact with Jupiter. In all, a few thousand dust impacts were counted with the instrument accumulators during both ring passages, but only a total of 110 complete data sets of dust impacts were transmitted to Earth. Detected particle sizes range from about 0.2 to 5μm, extending the known size distribution by an order of magnitude towards smaller particles than previously derived from optical imaging [Showalter, M.R., de Pater, I., Verbanac, G., Hamilton, D.P., Burns, J.A., 2008. Icarus 195, 361–377; de Pater, I., Showalter, M.R., Macintosh, B., 2008. Icarus 195, 348–360]. The grain size distribution increases towards smaller particles and shows an excess of these tiny motes in the Amalthea gossamer ring compared to the Thebe ring. The size distribution for the Amalthea ring derived from our in-situ measurements for the small grains agrees very well with the one obtained from images for large grains. Our analysis shows that particles contributing most to the optical cross-section are about 5μm in radius, in agreement with imaging results. The measurements indicate a large drop in particle flux immediately interior to Thebe’s orbit and some detected particles seem to be on highly-tilted orbits with inclinations up to 20°. Finally, the faint Thebe ring extension was detected out to at least 5R J, indicating that grains attain higher eccentricities than previously thought. The drop interior to Thebe, the excess of submicron grains at Amalthea, and the faint ring extension indicate that grain dynamics is strongly influenced by electromagnetic forces. These findings can all be explained by a shadow resonance as detailed by Hamilton and Krüger [Hamilton, D.P., Krüger, H., 2008. Nature 453, 72–75]. [Copyright &y& Elsevier]

Calcium species in mineral aerosols collected simultaneously in Aksu (near the Taklimakan Desert), Qingdao (eastern China), and Tsukuba (Japan) during dust and nondust periods were determined using Ca K-edge X-ray absorption near-edge structure (XANES). From the fitting of XANES spectra, it was found that (i) calcite and gypsum were the main Ca species in the aerosol samples, and (ii) the gypsum fraction versus total Ca minerals [Gyp]/[Ca2+]t increased progressively in the order Aksu < Qingdao < Tsukuba. Surface-sensitive XANES in the conversion electron yield mode (CEY) showed that the gypsum is formed selectively at the surface of mineral aerosols for all the samples except for that taken in Aksu during the dust period. The decrease of the [Gyp]/[Ca2+]t ratio with an increase in particle size showed that the neutralization effect proceeds from the particle surface. For the Aksu sample in the dust period, however, (i) the [Gyp]/[Ca2+]t ratios obtained by XANES measured in the fluorescence (FL; regarded as bulk analysis) and CEY modes were similar and (ii) size dependence was not found, showing that neutralization is not important for the sample because of the large supply of mineral aerosol with little neutralization effect in Aksu. It was also found that the pH of the aerosol and the ratio of (NH4)2SO4 to gypsum were positively and negatively correlated with the Ca (or calcite) content, respectively. The speciation of Ca by XANES revealed the neutralization processes of acidic sulfur species by calcite during the long-range transport of mineral aerosols. [ABSTRACT FROM AUTHOR]

Abstract: Among other factors (eg, bedding material, roughage), feed has an important effect on the airborne particle concentration in the stable air, in particular directly in the breathing zone of the horse during feeding. Therefore, this study was designed to analyze and compare the generation of different airborne particle fractions of diverse feed types and feed processing techniques under standardized laboratory conditions. Oats and barley as well as two commercially formulated ready-prepared pellets and two different commercially formulated ready-prepared mixes were analyzed. Oats were subjected to four different forms of processing (whole uncleaned, whole cleaned, rolled uncleaned, rolled cleaned), barley was subjected to steam flaking in addition to the same forms of processing as oats. In total, 13 feeds were analyzed. Airborne particle concentrations were detected online with a gravimetrically measuring analyzer that was equipped successively with different inlets to measure the particle fractions PM 1, PM 2.5, PM 10, and PM 20. The measurements were carried out in a closed chamber (1×1 × 1.5m) including a bowl (diameter=0.5m), which simulated the trough. The sample inlet was situated at a height of 1.0m above the bowl. Rolling oats and barley led to a significantly increased generation of the PM 20 fraction and a significantly decreased generation of the PM 2.5 fraction. The mechanical cleaning of oat and barley brings a clear decrease in dust generation from straights whether they are left whole or are rolled after cleaning. A considerable reduction in dust generation can be achieved if steam-flaked barley or commercially prepared feeds are used. [Copyright &y& Elsevier]

The scattering from moisture rough surface with spheroidal dust particles having surface with spheroidal dust particles has recently received much attention. In part due to the recent prediction and observation of the spheroidal dust particles in rough surfaces under elastic wave by the Kirchhoff scattering model and scalar approximation with slope. Our analysis shows that the scattering depends on the moisture (2–4·5%) with spheroidal dust particles. At slightly moisture rough surface the dielectric properties increase with change in field amplitude in a rough surface with spheroidal dust particles. [ABSTRACT FROM AUTHOR]

Abstract: Dust emission from storage yards is a multivariable problem to be solved not only at any new installation in order to obtain the licenses from the involved authorities but also at existing yards to continue the operation. Engineers have a great variety of methodologies available at the market to estimate such emissions, but in general the process is divided into two independent stages: wind flow analysis and application of emission rates into such wind pattern. This paper summarizes the research developed by this group to link both steps: by using CFX version 10.0, a powerful computational fluid dynamics (CFD) software, the wind flow around the piles is predicted, or even through a complex yard, and at the same time by implementing new subroutines introduced into the standard software, the program is able to give a quantitative evaluation of the total fugitive dust. [Copyright &y& Elsevier]

Abstract: Field experiments were conducted in Nellis Dunes Recreational Area (Clark County, Nevada, USA) to investigate emission of dust produced by off-road driving. Experiments were carried out with three types of vehicles: 4-wheelers (quads), dirt bikes (motorcycles) and dune buggies, on 17 soil types characteristic for a desert environment. Tests were done at various driving speeds, and emissions were measured for a large number of grain size fractions. This paper reports the results for two size fractions of emissions: PM10 (particles <10 μm) and PM60 (particles <60 μm). The latter was considered in this study to be sufficiently representative of the total suspendable fraction (TSP). Off-road driving was found to be a significant source of dust. However, the amounts varied greatly with the type of soil and the characteristics of the top layer. Models predicting emission of dust by off-road driving should thus consider a number of soil parameters and not just one key parameter. Vehicle type and driving speed are additional parameters that affect emission. In general, 4-wheelers produce more dust than dune buggies, and dune buggies, more than dirt bikes. Higher speeds also result in higher emissions. Dust emitted by off-road driving is less coarse than the parent sediment on the road surface. Off-road driving thus results in a progressive coarsening of the top layer. Exceptions to this are silty surfaces with no, or almost no, vegetation. For such surfaces no substantial differences were observed between the grain size distribution of road dust and emitted dust. Typical emission values for off-road driving on dry desert soils are: for sandy areas, 30–40 g km−1 (PM10) and 150–250 g km−1 (TSP); for silty areas, 100–200 g km−1 (PM10) and 600–2000 g km−1 (TSP); for drainages, 30–40 g km−1 (PM10) and 100–400 g km−1 (TSP); and for mixed terrain, 60–100 g km−1 (PM10) and 300–800 g km−1 (TSP). These values are for the types of vehicles tested in this study and do not refer to cars or trucks, which produce significantly more dust. [Copyright &y& Elsevier]

Abstract: The frequency distributions and some statistical features of background aerosol concentrations were investigated at two remote China Atmosphere Watch Network (CAWNET) stations. The estimated elemental carbon (EC) background at Akdala (AKD) in the mid-latitudes of northwestern China (~0.15 μg m−3) was only half of that at Zhuzhang (ZUZ) in low-latitude southwestern China (~0.30 μg m−3). The contributions of EC to the aerosol mass also differed between sites: EC contributed 3.5% of the PM10 mass at AKD versus 5.1% at ZUZ. Large percentages of the total organic carbon (OC) apparently were secondary organic carbon (SOC); SOC/OC averaged 81% at ZUZ and 68% at AKD. The OC/EC ratios in PM10 (ZUZ: 11.9, AKD: 12.2) were comparable with other global background sites, and the OC/EC ratios were used to distinguish polluted periods from background conditions. The SO4 2 −, NH4 + and soil dust loadings at AKD were higher and more variable than at ZUZ, probably due to impacts of pollution from Russia and soil dust from the Gobi and adjacent deserts. In contrast to ZUZ, where the influences from pollution were weaker, the real-time PM10 mass concentrations at AKD were strongly skew right and the arithmetic mean concentrations of the aerosol populations were higher than their medians. Differences in the aerosol backgrounds between the sites need to be considered when evaluating the aerosol''s regional climate effects. [Copyright &y& Elsevier]