Showing papers on "Particulates published in 1985"

Source terms and source strengths of the carbonaceous aerosol in the tropics

Abstract: Atmospheric aerosol samples were collected in the Ivory Coast, primarily at Lamto (6°N, 5°W) between 1979 and 1981. The samples were analysed for total particulate carbon concentration and isotopic composition (13C/12C) by mass spectrometry. Observed concentrations were found high compared to values reported for temperate regions. Fine particulate carbon in the submicrometersize range accounted for 50 to 80% of the reported concentrations. At Lamto, both particulate carbon concentrations and isotopic ratios exhibit a large temporal variability which is shown to reflect the diversity of sources and their seasonal evolution. Natural emissions from the equatorial forest during the wet season, and biomass burning during the dry season, appear to be the major sources. The latter, though active during only a third of the year, is, on an annual basis, the most important source. Based on the data obtained at Lamto, an attempt has been made to estimate the flux of fine particulate carbon emitted from the tropical regions into the global troposphere. This flux, which is of the order of 20×1012 g C/yr, appears to be equivalent to the flux of fine particulate carbon emitted from industrial sources. These results suggest that the tropospheric burden of fine particulate carbon in lowlatitude regions is dominated by the long-range transport of carbonaceous aerosols originating from the Tropics.

Catalyzed diesel exhaust particulate filter

Abstract: A self-cleaning diesel exhaust particulate filter is disclosed wherein burn-off of collected particulate matter is accomplished at certain exhaust gas temperatures, the filter being provided with a catalyst mixture consisting essentially of a platinum group metal and an alkaline earth metal oxide. The platinum group metal may be one or both of platinum and rhodium and the alkaline earth metal oxide may be magnesium oxide. The presence of the catalyst mixture serves to lower the temperature at which ignition of the collected particulates is initiated.

Magnetic differentiation of atmospheric dusts

Abstract: Although several magnetic separation methods have been used to provide some initial subdivision and characterization of the particulate emission products of fossil-fuel combustion1–5, only recently has there been any attempt to use magnetic properties to distinguish between different emission types6,7 and atmospheric particulate sources8. In the present study, we use several concentration-independent magnetic parameters and ratios to characterize dusts from different source types. Non-destructive measurements of saturation isothermal remanence, anhysteretic remanence and frequency-dependent susceptibility differentiate atmospheric dusts into groups characterized by distinctive magnetic mineral and grain size assemblages. These assemblages can be related to the source of the dusts as they reflect differences in the conditions under which the magnetic oxides developed. The magnetic parameters are sensitive to differences between dusts arising from fossil-fuel combustion and from other industrial processes, and those derived from soil erosion. Within the set of soil-derived dusts, the magnetic parameters distinguish between the weathering regimes operating in different source areas.

Trace element concentration as a function of particle size in fly ash from a pulverized coal utility boiler.

Abstract: Total and elemental mass size distributions from about 10 to 0.04 m were obtained for the fly ash aerosol at the outlet of a pulverised coal utility boiler and upstream of the particulate control device. Elemental data were obtained by instrumental neutron activation analysis and X-ray fluorescence analysis of cascade impactor samples. Submicrometer measurements were also made with an electrical aerosol analyser. INAA results showed that the fly ash between about 0.5 and 8 m was fairly uniform in composition and that the micrometer fume composition was quite different. The fume was highly enriched in volatile elements such as Ga, As, Sb and Se and depleted in refractory elements such as Al, Hf and Sc.

Boron in the troposphere: Distribution and fluxes

Abstract: Gaseous and particulate concentrations of atmospheric boron have been measured simultaneously for the first time at several marine and continental areas using an impregnated filter sampling technique. Rainwater boron concentrations were also determined. The data indicate that most of the atmospheric boron is present in the gas phase. Gaseous boron concentrations are higher over the ocean than over the continents. Particulate boron may have the opposite distribution. Gaseous boron concentrations are elevated in some urban continental areas, probably as a result of volatilization of boron during coal combustion. The concentration of boron in rain and on aerosol particles is similar at all locations, suggesting that scavenging of aerosol particle boron may control boron in rain even though a significant gas phase exists. Total gaseous boron emissions from all sources are estimated as 250–490×1010 g yr−1, and particulate boron emissions are estimated to be 32–88×1010 g yr−1. The major global sources of atmospheric boron appear to be volcanic emissions and sea salt aerosol production. The tropospheric residence time of gaseous and particulate boron is estimated to be 19–36 days and 2–6 days, respectively.

Seasonal variations in natural abundance of 15N in particles sinking to the deep Sargasso Sea

Abstract: Temporal variations in 15N natural abundance have been used to study both nitrogen cycling and particle dynamics in the ocean1. Changes in the δ15N (1,000×[(15N/14N)sample/(15N/14N)atmospheric N2−1]) of particulate matter are related, in part, to variations in the input of nitrogen to the euphotic zone that have been observed to regulate the downward transport of particles2. Here we report the first long-term data set for seasonal variations in the δ15 N of sinking particulate matter sampled using a sediment trap. These variations co-vary with the magnitude of the particle flux. We propose that the δ15N of sinking particles is a monitor for NO−3 flux into the euphotic zone during the formation of these particles on a timescale directly related to the magnitude of the particle flux.

Variations in the natural abundance of 15N in estuarine suspended particulate matter: A specific indicator of biological processing

Abstract: In this study, the 14N:15N ratio of suspended particulate material collected from the Tamar river estuary, south-west England, is described. Three populations of particles, distinguishable by their 15N content, were observed. This investigation has shown that populations of estuarine particles are generated by biological transformations in situ and that the 15N content of estuarine particles does not merely reflect hydrodynamic mixing of the freshwater and seawater source particulate material.

Determination of 23 polycyclic aromatic hydrocarbons in atmospheric particulate matter of the Paris area and photolysis by sunlight.

Abstract: Twenty-three polycyclic aromatic hydrocarbons (PAH) were determined in atmospheric particulate matter in 4 places of the Paris area at several times of the year. Fractionation was performed by reversed-phase high-pressure liquid chromatography. Determination was done by recording emission or excitation fluorescence spectra via a stopped-flow technique. Triphenylene was also extemporaneously determined by its phosphorescence spectrum at low temperature. Among the PAH determined dibenz(e, ghi)perylene has not been detected before in atmospheric particulate matter. The 10 more abundant PAH ranged from 0.1 to 40ng/m3 of filtered air. Concentrations in August are from 14 to 250 times less than in January depending on the PAH. The reasons for this difference of behaviour among the PAH were investigated with regard to their photochemical and non-photochemical reactivity.

Circulating solids fluidized bed reactor and method of operating same

Abstract: A fluidized bed reactor and a method of operating same in which three discrete chambers are formed in a housing and a main fluidized bed containing particulate fuel and adsorbent material is established in a first chamber. The fluidizing air in the first chamber entrains a portion of the particulate material as it passes through the bed and the first chamber. A portion of the particulate material that is entrained by the air is separated and introduced to additional grid means disposed in a second chamber to establish a bed of the separated particulate material. Air and a cooling fluid are passed through the bed of separated particulate material for cooling same. The cooled separated particulate material is passed to a third chamber for storage and the latter is connected to the main fluidized bed for selectively reinjecting the cooled separated particulate material back to the main fluidized bed. A portion of the separated particulate material may also be introduced to another fluidized bed operating under conditions to convert the calcium sulfide formed in the main bed to calcium sulfate.

Platinum/silver vanadate catalyzed diesel exhaust particulate filter

Abstract: A self-cleaning diesel exhaust particulate filter is disclosed wherein burn-off of collected particulate matter is accomplished at normal exhaust gas temperatures, the filter being provided with a catalyst mixture of a platinum group metal and silver vanadate, the presence of which lowers the temperature at which ignition of the particulate is initiated.

Studies of a mangrove basin, Tuff Crater, New Zealand: III. The flux of organic and inorganic particulate matter

Abstract: Water samples were collected at 15 min intervals over 11 tidal cycles from a tidal creek draining the mangrove-covered basin of Tuff Crater, Auckland, New Zealand. The samples were filtered and total suspended sediment (TSS), inorganic suspended sediment (ISS) and organic suspended sediment (OSS) were determined. Variation in TSS was high, the concentration varied over a tidal cycle and during over-bank flows concentrations were lowest at or near slack high water. Covariance between TSS concentrations and velocity and discharge meant that the calculation of particulate matter flux over tidal hemicycles was particularly dependent on the method of estimating tidal flux. The hypsometrically-based volumetric method was found to be inappropriate, predicting a positive budget (import) more often than observed. Instead particulate matter budgets were calculated by means of the velocity-area method and indicate a net export of TSS, ISS and OSS. Floating macrodetritus was observed on both the flood and ebb tides, but a net export was found on the two tides monitored. It is considered that on an annual basis floating macrodetritus export accounts for less than 2% of the detrital production in the basin, and organic suspended sediment export from the basin is less than 3 kg C ha −1 day −1 and is below the rate of detrital production. It is implied that a proportion of the organic detritus produced in this basin is degraded and recycled in situ .

Detailed distribution of dissolved and particulate organic matter in the Arctic Ocean and comparison with other oceanic regions

Abstract: Over 100 measurements of particulate organic carbon (POC), particulate nitrogen (PN) and dissolved organic carbon (DOC), based on bottle collections, were made through the ice in the Arctic Ocean as part of the Canadian CESAR expedition. Despite considerable scatter at all depths, the three variables show a general decrease with depth to the bottom (2100 m). The average PN concentrations are the lowest yet reported, as are the POC concentrations in the upper 500 m. DOC concentrations are similar to other oceanic regions. There is no relationship between any variable and water mass structure. The average C:N ratio (by weight) of particulate organic material is 11.5 in the surface layer and increases with depth. Compared to data collected from other oceans, the Arctic concentrations demonstrate similar depth gradients which are steepest for PN and least for DOC. There also is a broad scale relationship between surface primary production and POC and PN concentrations throughout the water column.

Apparatus for microaquaculture and pollution control

Abstract: Apparatus for producing and removing dissolved and particulate matter from natural bodies of water and wastewater in situ for the production of organic biomass such as feedstocks, for the removal of pollutants, nutrients, toxins and other substances, and for other purposes. A gas is introduced through a diffuser into a body of water to form bubbles. The bubbles rise within a lifting tube, gathering dissolved and particulate matter on their surfaces. The bubbles produce a foam at the surface of the body of water, the foam being collected in a reservoir, concentrated and drawn off.

Cadmium and nickel in mainstream particulates of cigarettes containing tobacco grown on a low-cadmium soil-sludge mixture

Abstract: Cigarettes were prepared from tobaccos grown in the greenhouse on a soil to which a low rate of a municipal sewage sludge was applied. The cigarettes were smoked by machine and the mainstream paniculate fraction was analyzed for total cadmium and nickel content. Sludge‐grown and control (soil‐grown) tobaccos contained, respectively, 5.33 and 1.87 ppm of cadmium and 1.15 and 0.64 ppm of nickel. The average quantities of cadmium and nickel (ng/cigarette) found in the mainstream paniculate fractions were, respectively, 220.5 and 78.5 for the sludge‐grown and 147.4 and 72.6 for the control treatments. The difference between treatments was highly significant (p < 0.001) for cadmium but not significant for nickel.

Impact of particulate traps on the hydrocarbon fraction of diesel particles

Abstract: Particulate traps reduce particle emissions through the physical filtration of solid, predominantly carbonaceous particles and decreasing particle-bound hydrocarbon emissions Catalyst coated and uncoated traps were examined for their ability to reduce particle-bound hydrocarbons At low exhaust temperatures some volatile hydrocarbons are particle-bound in the trap and are physically retained These components become gaseous and are purged from the trap with sharp exhaust temperature rises Oxidation catalysts considerably improve the ability of traps to decrease particle-bound hydrocarbon emissions, particularly PAH at low exhaust temperatures Precious metal coated traps generate sulfate particles so that especially at high exhaust temperatures the overall filter efficiency can be reduced

Characterizing and Discriminating Airborne Amphibole Cleavage Fragments and Amosite Fibers: Implications for the NIOSH Method

Abstract: The NIOSH method for determining asbestos exposure in the mining environment involves using phase contrast microscopy to examine mineral particulates collected on air monitor filters. Particles are classified as asbestiform or non-asbestiform based on their size and length-to-width (aspect) ratio. The procedure works well when only fibers are present. In most non-asbestos mining operations, however, cleavage fragments are the most abundant airborne particulates. In this research, discriminate function analysis was applied to morphological data for airborne amphibole particulates to show that dimensional criteria could distinguish between amphibole asbestos and amphibole -cleavage fragments. The particulates for this research were collected from industrial sites where amosite alone was in use and from mining sites where amphiboles are major rock-forming minerals. The results suggest that cleavage fragments can be differentiated from asbestos fibers based on dimensional criteria alone, but only if the curre...