Showing papers on "Particulates published in 1993"

Sources of fine organic aerosol. 2. Noncatalyst and catalyst-equipped automobiles and heavy-duty diesel trucks

Abstract: Gasoline- and diesel-powered vehicles are known to contribute appreciable amounts of inhalable fine particulate matter to the atmosphere in urban areas. Internal combustion engines burning gasoline and diesel fuel contribute more than 21% of the primary fine particulate organic carbon emitted to the Los Angeles atmosphere. In the present study, particulate (d[sub p] [le] 2 [mu]m) exhaust emissions from six noncatalyst automobiles, seven catalyst-equipped automobiles, and two heavy-duty diesel trucks are examined by gas chromatography/mass spectrometry. The purposes of this study are as follows: (a) to search for conservative marker compounds suitable for tracing the presence of vehicular particulate exhaust emissions in the urban atmosphere, (b) to compile quantitative source profiles, and (c) to study the contributions of fine organic particulate vehicular exhaust to the Los Angeles atmosphere. More than 100 organic compounds are quantified, including n-alkanes, n-alkanoic acids, benzoic acids, benzaldehydes, PAH, oxy-PAH, steranes, pentacyclic triterpanes, azanaphthalenes, and others. Although fossil fuel markers such as steranes and pentacyclic triterpanes can be emitted from other sources, it can be shown that their ambient concentrations measured in the Los Angeles atmosphere are attributable mainly to vehicular exhaust emissions. 102 refs., 9 figs., 6 tabs.

Sources of fine organic aerosol. 3. road dust, tire debris, and organometallic brake lining dust: roads as sources and sinks

Abstract: Particulate matter emitted to the atmosphere due to motor vehicles arises from several sources in addition to tailpipe exhaust. In this study, the organic constituents present in fine particulate (d_p ≤ 2.0 µm) road dust, brake lining wear particles, and tire tread debris (not size segregated) are analyzed using gas chromatography/mass spectrometry. The objective is to characterize such traffic-related sources on an organic compound basis and to search for molecular markers that will assist the identification of traffic-associated dusts in the urban atmosphere. More than 100 organic compounds are quantified in these samples, including n-alkanes, n-alkanoic acids, n-alkenoic acids, n-alkanals, n-alkanols, benzoic acids, benzaldehydes, polyalkylene glycol ethers, PAH, oxy-PAH, steranes, hopanes, natural resins and other compound classes. Paved road dust acts as a repository for vehicle-related particles, which can then be resuspended by the passing traffic. To evaluate the contributions from major urban sources to the road dust complex, source profiles representing different types of vehicle exhaust, brake dust, tire debris, and vegetative detritus are compared, and their fractional contributions are estimated using several groups of organic tracer compounds. Likewise, the close relationship between airborne fine particulate organic constituents and road dust organic matter is discussed.

The stoichiometry of carbon, nitrogen, and phosphorus in particulate matter of lakes and oceans

Abstract: The mean carbon, nitrogen, and phosphorus contents of particulate material for 5 1 lakes or lake basins, extending from arctic to tropical climatic regions, including small lakes as well as the largest lakes in the world, indicate that Redfield ratios are the exception rather than the rule in freshwater. The C: P and N : P ratios are more variable for lake particles but generally higher than marine particles, and the mean molar C: N, C: P, and N : P ratios are substantially higher than the Redfield ratio of 106 : 16: 1. On average, lower C : N, C : P, and N : P ratios occur in subarctic lakes while higher ratios occur in the tropics and in temperate, oligotrophic lakes on the Canadian Shield. In shield lakes with long residence times (>6 months) the high ratios of C : N, C : P, and N : P do not originate from streamborne or atmospherically deposited particles but arise from in-lake processes. Regression analysis demonstrates that small lakes are generally more N and P deficient than large lakes. In freshwaters, particulate composition ratios imply that a wide variety of conditions exists in lakes, including N and P deficiency, as well as N and P sufficiency. In the Experimental Lakes Area of Canada, independent physiological nutrient status indicators generally agree with the status indicated by seston ratios. The relative uniformity of marine C : N : P composition (compared to lakes) at the Redfield ratio suggests that marine plankton cannot be as severely, or as frequently, limited by N and P as lake plankton. Consequently, the paradigm of N limitation in the oceans requires qualification. Based on particulate comDosition, it is more correct to say that ocean plankton is noi as N grid P deficient as lake-plankton. The composition of marine particulate matter is relatively uniform. Redfield (1934, 1958) noted the near constancy of the ratio of C : N : P in marine plankton and the similarity of the N : P ratio of plankton to the oceanic deepwater ratio of nitrate to phosphate. As early as 1940, the C : N : P molar composition ratio of marine plankton was accepted to be 106 : 16 : 1 (Redfield et al. 1963); this ratio is now referred to as the Redfield ratio. The ratio has withstood the test of time, and the ever-growing number of analyses of marine particles and nutrient regeneration profiles, with relatively

The distribution and biogeochemical cycling of mercury in the equatorial Pacific Ocean

Abstract: The ocean is an important part of the global mercury (Hg) cycle, both as a source and sink for atmospheric Hg. This investigation was initiated to study the speciation and distribution of Hg in the equatorial Pacific Ocean. Monomethylmercury (MMHg) and dimethylmercury (DMHg) were found principally in the low oxygen sub-thermocline region, while elemental Hg (Hg°) was found throughout the upper ocean. Flux calculations and modelling studies suggest that DMHg and MMHg are formed from reactive Hg (HgR) primarily in the low oxygen region. Particulate dissolution is the major source of Hg to the low oxygen zone. DMHg probably decomposes into MMHg, and MMHg is further demethylated to Hg°. In the mixed layer, Hg° is also formed via direct reduction of HgR. This investigation provides evidence that the rate of supply of HgR controls the rate of formation of methylated Hg species and Hg°, and that competition between these processes determines the speciation and distribution of Hg in the upper ocean of the equatorial Pacific.

C, N, P and S in Rivers: From Sources to Global Inputs

Abstract: Carbon, nitrogen, phosphorus and sulfur are essential elements found either as dissolved or particulate river-borne material. Their origins, their behaviours in aquatic systems, the occurrence of their specific forms, and the rates of transport by rivers are first considered in this paper. The anthropogenic influences on riverine C, N, P, and S are briefly presented. Finally the global fluvial budgets of the specific forms, including the anthropogenic loads are estimated.

Well treating methods using particulate blends

Abstract: Fracturing, frac-pack, and gravel packing procedures are provided which utilize a treating composition comprising a carrier fluid and a particulate blend. The particulate blend consists essentially of a large particulate material and a small particulate material. The large particulate material consists essentially of particles smaller than about 4 mesh but not smaller than about 40 mesh. The small particulate material consists essentially of particles smaller than about 16 mesh but not smaller than about 100 mesh. The small particulate material is present in the particulate blend in an amount in the range of from about 5% to about 60% by weight based on the amount of the large particulate material present in the particulate blend. A prepacked screening device including a large particulate/small particulate blend of the type just described is also provided.

Biochemical Composition and Nutritive Value of Suspended Particulate Matter Over a Tidal Flat of Southern Chile

Abstract: Seasonal fluctuations in the biochemical composition of the suspended particulate matter were followed during 2 years in a tidal flat of southern Chile. The suspended particulate matter load (seston) was highly dependent on tidal resuspension and primary productivity. Variations in carbohydrate, lipid and protein in the seston were primarily associated with the periods of high and low standing stocks observed in this environment. Their seasonal trends were very similar and highly correlated with those described for other components of the seston, such as organic matter, chlorophyll α and particulate organic carbon and nitrogen. The nutritional quality of the seston was expressed by a food index calculated on the base of the ratio of food material (lipid + carbohydrate + protein) to total seston. This index was negatively correlated with the inorganic fraction of the seston. Multiple regression analysis showed that the best model to explain the variation of the food index included the inorganic fraction of the seston and the particulate organic nitrogen, which together accounted for 85%. The results suggest that the gross analysis of the seston (organic and inorganic fractions) cannot describe fully its nutritive value and a detailed analysis of the biochemical composition is recommended to achieve a better understanding of the quality of the diet available to filter-feeders.

Airborne measurements of gases and particles from an Alaskan wildfire

Abstract: Airborne measurements of several gaseous and particulate chemical species were obtained in the emissions from a wildfire that burned in an old black spruce forest in Alaska during the summer of 1990. The relative proportions of most of the measured plume constituents are consistent with ground-based and airborne measurements in the plumes of several other biomass fires, and with laboratory measurements. Possible exceptions include the mean fine-particle emission factor, which was about 3 times larger than predicted from a regression relation based on measurements of the smoke from several prescribed biomass fires, and the mean CH4/CO molar emission ratio which was at the low end of a range of values measured for other biomass fires. Measurements of water-soluble particulate ions in the smoke plume from the Alaskan wildfire indicate that acids formed from the oxides of sulphur and nitrogen were partially neutralized inside cloud droplets by NH3 absorbed from the plume.

A particulate and exhaust gas emission control system

Abstract: A particulate and exhaust emission control system for a vehicle (10) having a diesel engine (12). The control system has a particulate trap (24) connected to the exhaust manifold (22) of the diesel engine, an additive tank (30) for storing a fuel additive decomposed by the engine's combustion process to form a reducible metal oxide capable of depressing the ignition temperature of the carbon particulates collected by the particulate trap (24) and a metering mechanism (34) responsive to the adding of diesel fuel to the vehicle's fuel tank (28) to add a quantity of the fuel additive to the diesel fuel in the fuel tank (28) to maintain a predetermined ratio of the fuel additive to the diesel fuel in the tank. The metal oxide depressing the ignition temperature of the carbon particulates collected by the particulate trap (24) to a temperature obtained by the particulate trap during selected operating parameters of the diesel engine (12). The particulate trap (24) includes a honeycomb ceramic filter element (38) having inlet channels (44) for collecting the carbon particulate and exit channels (46) coated with a catalyst to oxidize carbon monoxide and unburned hydrocarbons in the exhaust.

Distribution and composition of particulate organic matter in the Ross Sea (Antarctica)

Abstract: The biochemical composition and spatial distribution of particulate organic matter (POM) were studied in the Ross Sea (Antarctica) in summer 1989 to assess the quantitative role of organic carbon fractions in the cycling of organic matter in the water column. Large differences in chemical composition were observed between surface and deep layers. The results indicated that, despite large geographical differences, POM was quite homogeneous, of phytoplankton origin and mostly detrital. Different ratios were used to investigate the changes in biochemical composition of particulate organic matter in relation to the ice-melting: C∶N (organic carbon∶organic nitrogen ratio) and C-POM∶POC (sum of carbohydrate, protein and lipid carbon∶total organic carbon ratio) were used to analyse the percentage of refractory organic material. PPRT∶PCHO (protein∶carbohydrate ratio) were used to establish POM “age” and RNA∶DNA ratios as a relative measure of particulate activity; POC∶Chl a and N-PPRT∶Chl a ratios were used to estimate the autotrophic contribution to the suspended particulate organic matter. Despite its low caloric value (5.3 Kcal g POM−1), an high caloric content in the photic layer (1.6 Kcal m−3 of POM and 2.5 Kcal m−3 of POC) was found thus indicating that a large amount of food was available to higher trophic levels.

Process engineering and design for air pollution control

Abstract: 1. An Overview of the Air Pollution Problem. 2. Cost Estimation Methodology. 3. Incineration for Control of VOC Emissions. 4. Adsorption Devices. 5. Flue Gas Desulfurization. 6. Control of Nitrogen Oxides. 7. Fundamentals of Particulate Emissions Control. 8. Cyclonic Devices. 9. Electrostatic Precipitators. 10. Fabric Filters. Appendixes: Heat Capacity Equations Heating Values of Various Compounds Clean Air Act Ammendments of 1990 Gaussian Quadrature.

Suspended Matter and Sediment Transport

Abstract: In the aquatic environment contaminants are transported in solution and in particulate form. In the latter case they are present as colloids or adsorbed onto particles (trace metals, trace organic compounds) or as single particles (e.g., flyash, coal, cokes, colliery waste, organic waste). The contaminating particles range from very fine material with diameters in micron size to sand- and gravel-sized particles. For many contaminants transport in particulate form constitutes an important fraction (up to more than 70%) of the total transport.

Contaminated air purifying apparatus

Abstract: A contaminated air purifying apparatus (1, 101, 201, 301, 401, 501) capable of decreasing particles such as dust floating in air, soot produced by a combustion engine and the like and air pollutants such as nitrogen oxides (NOx) contained in exhaust gas. Particulates such as dust, soot and the like are electrostatically negatively charged in an electrifying mesh section (10, 104, 210, 310, 406, 506) and collected in a purifying filter section (20, 106, 220, 320, 407, 508) by coulombic force. NOx is converted into N₂ and CO₂ by an action of carbon fiber or carbon particles, resulting in decreased in concentration. The carbon fiber and carbon particles are preferably modified into an increased surface area of 200 to 2000 m²/g.

Carbon and the optical properties of atmospheric dust.

Abstract: Atmospheric particulate matter was examined to estimate the significance of free carbon as an absorber of near-ultraviolet, visible, and near-infrared radiation. Bulk and size-fractionated samples have been disassembled into acetone-soluble, water-soluble, and insoluble fractions. The absorption coefficients for these fractions, and for the insoluble material after removal of the free carbon by burning, have been measured. The results show that in the visible and near infrared, free carbon, although not a major component by mass, is by far the dominant absorbing material. These measurements in relation to other research suggest that geographic variations in and anthropogenic contributions to the free-carbon content cause much of the variation in the absorption coefficient of atmospheric particulate samples.

Particulate collection device with integral wet scrubber

Abstract: An integrated wet scrubber and particulate collection device for removing sulfur oxides and other contaminants from combustion flue gas and also for removing particulates from this gas, such operations occurring in a single, integrated unit or assembly. In some instances, this combination device may be located in the lower portion of a chimney or stack.

Determination of 206/207Pb isotope ratios by ICP-MS in particulate matter from the North Sea environment

Abstract: The determination of lead isotope ratios can be used for source and pathway characterization of lead in the environment. The suitability of inductively coupled mass spectrometry (ICP-MS) was evaluated for the measurement of 206/207Pb isotope ratios in several marine compartments as marine aerosols from different source regions and suspended particulate matter from the North Sea. Two different ICP-MS systems were used to carry out these investigations. First optimization studies have been performed to yield a sufficient precision (RSD <0.5%) in combination with a reasonable measuring time. This study has been carried out using the standard reference material NBS 981 with certified lead isotope ratios. Furthermore, it could be shown for marine environmental samples, that a precision of less than 0.5% RSD is attainable for counting rates of above approximately 50000 cps. As the following measurements of lead isotope ratios in marine aerosols from main source regions surrounding the North Sea demonstrated, this precision is sufficient to determine significant differences due to the origin of atmospheric lead. The analysis of aerosol samples revealed isotope ratios varying from as low as 1.10, which is close to that ratio for leaded gasoline in Europe to near background (modern lead) values of 1.20. The lead isotope ratios for the investigated suspended particulate matter ranges between 1.13 and 1.18. These values can be related to the solid discharge, the urban density and anthropogenic activity of the drainage basin.