Showing papers on "Particulates published in 1992"

Trace elements - emissions from coal combustion and gasification

Abstract: This report reviews the origin of trace elements in coal and their partitioning through coal-fired combustion and gasification processes, and downstream pollution control equipment. The importance of coal utilization as a source of trace element emissions to the atmosphere is evaluated. Limits controlling atmospheric emissions of certain potentially toxic trace elements have been introduced in some countries. Currently little legislation applies directly to emissions from coal utilisation, but it is unlikely that this source will remain exempt from regulation in future. Flue gases exiting a coal-fired boiler or gasifier contain trace elements either bound to particles or as volatile substances in the gas phase. High efficiency electrostatic precipitators or fabric filters can reduce particulate emissions to low concentrations. Wet or dry flue gas desulphurisation systems reduce emissions of volatile elements by concentrating the elements from flue gases in solid or liquid streams. Low temperature scrubbers present in some gasification systems provide an effective method for removal of most trace elements from the gas streams. The installation of pollution control equipment to comply with legislation for particulate and sulphur emissions will thus incidentally reduce the release of trace elements to the atmosphere. The report includes studies of the distribution of trace elements in all output stream from coal-fired power stations, focusing on releases to the atmosphere. An integrated approach to pollution control should ensure that reductions in emission to the atmosphere do not result in increased pollution from solid or liquid wastes. 234 refs., 46 figs., 46 tabs.

Biomass Burning Airborne and Spaceborne Experiment in the Amazonas (BASE-A)

Abstract: Results are presented on measurements of the trace gas and particulate matter emissions due to biomass burning during deforestation and grassland fires in South America, conducted as part of the Biomass Burning Airborne and Spaceborne Experiment in the Amazonas in September 1989. Field observations by an instrumented aircraft were used to estimate concentrations of O3, CO2, CO, CH4, and particulate matter. Fires were observed from satellite imagery, and the smoke optical thickness, particle size, and profiles of the extinction coefficient were measured from the aircraft and from the ground. Four smoke plumes were sampled, three vertical profiles were measured, and extensive ground measurements of smoke optical characteristics were carried out for different smoke types. The simultaneous measurements of the trace gases, smoke particles, and the distribution of fires were used to correlate biomass burning with the elevated levels of ozone.

The cycling of iron and manganese in the water column of Lake Sammamish, Washington

Abstract: Processes controlling the distribution and mobility of Fe and Mn in Lake Sammamish, Washington, a seasonally anoxic lake, are deduced from a year-long monthly study of physical, chemical, and biological parameters in the lake. Inventories of dissolved Mn and Fe in the bottom waters increase as the redox potential lowers with dissolved Mn inventories during stagnation being much larger than inventories of dissolved Fe. The shapes of the dissolved metal profiles indicate that dissolved Fe is supplied to the hypolimnion during stratification by diffusion of Fe(II) from the sediments into the overlying anoxic water as well as reduction of Fe oxide particles settling through the anoxic water column, while the dominant source of dissolved Mn to the anoxic bottom waters during most of the stratification period appears to be reduction of settling Mn-oxide particles. Inventories of particulate Fe in the hypolimnion during the latter stages of stratification are significantly larger than inventories of particulate Mn. Peaks of particulate Fe and Mn occur in the water column from July through November and particulate Mn peaks always occur at shallower depths than peaks of particulate Fe. Flux calculations suggest that there is a sufficient supply of both oxygen and reduced metal to the particulate zones for metal-oxide precipitation to occur. Thermodynamic calculations suggest that during the sulfidic phase of stagnation dissolved Fe concentrations in the very bottom waters may be controlled by FeS precipitation.

Standing stocks of particulate carbon and nitrogen in the equatorial Pacific at 150°W

Abstract: In March 1988 a north-south transect at longitude 150°W was carried out in the equatorial Pacific between latitude 15°N and 15°S. Observations of suspended particulate matter in the euphotic zone included particulate carbon, nitrogen, and chlorophyll, with a few samples taken for counting picoplankton and nanoplankton. Nearly all the particulate nitrogen is accounted for by bacteria and phytoplankton. The standing stock of bacterial C and N exceeded that of phytoplankton. The residence time of particulate organic carbon in the surface water was only 4–5 days in the equatorial upwelling, but 10–15 days to the north and south, suggesting relatively rapid removal by recycling and lateral advection.

Method and apparatus for electrostatically cleaning particulates from air

Abstract: An electrostatic air cleaner is disclosed along with a method for removing particulate matter from moving streams of air. A high voltage ionizer is used as a corona source to ionize the particulate matter as it approaches the air filter portion of the electrostatic air cleaner. The air filter uses a pair of reticulated polyether foam filters for collecting the particulate matter. The foam filters are separated by a thin, grid-like layer of semiconductive material (carbon-impregnated polycarbonate) which is raised to a very high DC voltage. The foam filters are also surrounded by thin, grid-like layers of electrically conductive material which are held at ground potential, thus creating a high-voltage electric field through each of the foam filters. The polyether foam filter media is non-deliquescent, thus preventing the high-voltage electric field from being dissipated by such imbedded water vapor, which is the cause of filter inefficiency in the prior art. The electrostatic air cleaner of the present invention has such high initial efficiency that it does not require the addition of any particulate matter to its surfaces to achieve its nominal efficiency when first put into use. The air filter can be constructed in a relatively thin, rectangular shape, or in a cylindrical cartridge for use with industrial dust collecting systems. Both shapes lend themselves for ease of installation and removal within air handling systems.

The investigation of dissolved and suspended-particulate trace metal fractionation in the Black Sea

Abstract: A sequential filtration-ion-exchange column scheme has been developed for the investigation of dissolved trace metal fractionation. The method is designed to separate water column metals rapidly into particulate and colloidal-sized species, anionic dissolved metal-organic and/or metal-sulfide complexes, and «free» (hydrated) metal cations and/or labile major ion complexes. The suspended-particulate matter (0.4 μm filterable material) is further subjected to a sequential leaching procedure to separate particulate metals into weak-acid leachable, strong-acid leachable, and refractory fractions

The effect of particulate organic matter on biofilm nitrification

Abstract: The effects of particulate and soluble organic matter (BOD) on nitrification were investigated in laboratory experiments using a bench-scale rotating biological contactor (RBC). This work was initiated by lower than expected nitrification rates in the second state biofilm processes at the Longmont Waste Water Treatment Plant (LWWTP). It was hypothesized that this was due to particulate matter since soluble BOD in the influent was low. For a range of 12 and 82 mg/L total BOD to the pilot RBC; particulate BOD was found to inhibit nitrification to the same degree as soluble BOD. In fact, total (soluble plus particulate) influent organic mater was found to be a better predictor of nitrification than soluble organic matter concentration

Evolution of Dissolved and Particulate Matter during the Ice-Covered Period in a Deep, High-Mountain Lake

Abstract: Changes in inorganic and organic matter beneath the ice in a deep oligotrophic lake are used to establish temporal and spatial scales of physical and biological processes involved in the dynamics o...

The influence of organic matter quality on the toxicity and partitioning of sediment‐associated fluoranthene

Abstract: Organic matter in sediment is derived from many sources, including dead plants and animals, fecal matter, and flocculated colloidal organic matter. Chemical partitioning and toxicity of nonpolar organic contaminants is strongly affected by the quantity of sediment organic matter. The purpose of the study was to determine whether the quality of sediment organic matter affects partitioning and bioavailability of such contaminants. A base substrate, amended to a consistent organic carbon level (nominally 0.4%, measured 0.35% + or - 0.11 sd POC (particulate organic carbon)) with five types of organic matter (a macrophyte, fecal matter of two invertebrate species, suspended particulate organic matter, and an organic-rich mud), was spiked with serial concentrations of the polynuclear aromatic hydrocarbon, fluoranthene. After a five-week equilibration period, the toxicity of the spiked substrates to an infaunal amphipod, Rhepoxynius abronius, was measured, and the distribution of fluoranthene between particulate and interstitial water phases (including total and freely dissolved interstitial water phases) was determined.

Particulate carbon content in rain at various temperate and tropical locations

Abstract: Particulate organic and black carbon concentrations in rain were determined in various source or remote regions, in order to gain information on the incorporation of atmospheric carbonaceous particles in hydrometeors. The analyses of rainwaters indicate that all the samples contained particles derived from combustion. Data obtained on a sample basis, show an important areal and temporal variability of the composition of rain carbonaceous particles, a variability which is reported to that of the black carbon to total carbon ratio, Cb/Ct, ranging from 10 to 72%. In addition to the fluctuations of the aerosol atmospheric burden, these variations may be related to alterations of the organic fraction of the particles or their involvement in in-cloud nucleation processes during atmospheric transport. Also, a comparison of the mean relative abundance of black carbon in aerosols and in rainwaters, gives evidence of a partial disappearance of the organic particles, a phenomenon which could be due to their dissolution when incorporated in the hydrometeors. Precipitation scavenging ratio values of black carbon particles, which range from 100 to 370, are similar to those found for sulphate anthropogenic aerosols. Due to their hygroscopic properties and mean size, black carbon aerosols could possibly trace the physico-chemical processes involved in the incorporation of fine combustion particles into hydrometeors. It is also suggested that smoke particles may act as cloud condensation nuclei (CCN). Consequently, emissions of particulates derived from combustion in some tropical or industrial regions could result locally in alteration of cloud albedo and precipitation regimes.

Temporal variations of 234Th activity in the water column of Dabob Bay: Particle scavenging

Abstract: Monthly measurements of total, dissolved, and particulate 234Th, along with fluxes of total mass and particulate 234Th, were made throughout 1987 in Dabob Bay, Washington. Vertical distributions of total 234Th showed a large deficiency relative to 238U throughout the water column during all sampling periods. Total 234Th activities in surface waters were generally bigher in winter and lower in summer, in response to seasonal biological activity. In spite of this variation, the steady state assumption seems valid for modeling 234Th of the bay because the magnitude of variation is insignificant in the mass balance calculation. The range of residence times of total, dissolved, and particulate 234Th estimated horn an irreversible scavenging model are 4-70, <: l-10, and 3-60 d, respectively. The residence time of 234Th is controlled by the suspended particles whose distribution is determined by biological production in the surface layer and resuspension of bottom sediments. Vertical fluxes of 234Th measured by sediment traps also showed wide seasonal variation and generally increased monotonically from 200-l ,000 dpm me2 d-l at 20 m to 2,000-4,000 at 100 m. The flux of 234Th predicted with the steady state scavenging model tends to be about twice the directly measured 234Th flux. This difference may be due either to low trap efhciency for 234Thcontaining particles or to boundary scavenging at the sides of the basin. The residence times of particulate 234Th and total suspended matter agree well, and both are influenced by biological processes.

Trace metal distribution coefficients in the Weser Estuary (Germany)

Abstract: Trace metals in the dissolved phase, and in operationally defined available and total particulate associations, have been determined along an axial transect of the Weser Estuary, together with measurements of salinity, temperature, pH, dissolved oxygen, suspended particulate matter (SPM), chlorophyll a, free and attached bacteria, particulate carbon and particle specific surface area. Throughout the estuary the dissolved metals exhibited non-conservative behaviour due to sorption reactions with particle surfaces and sediment-water exchange processes. This reactivity was enhanced at the fresh water-brackish water interface where changes in the master variables were most pronounced. The influence of sorptive processes on total particulate metal distributions was not evident and major compositional variability was ascribed to physical mixing of different particle populations. The relative proportions of trace metals in the dissolved and solid phases were interpreted in terms of conditional distribution coefficients, KDs, whose magnitude depends critically on which fraction of particulate metal is selected (i.e. available or total). The KDs for Fe and Mn increased with increased SPM concentration, whereas those for Cu, Ni, Zn and possibly Pb decreased with SPM; such observations are related to whether particle-water exchange processes at any locality in the system are far from or at (quasi-) equilibrium, and to differences in the sorptive characteristics of suspended particle populations. These results have implications for the behaviour of trace metals in the Weser Estuary and are also discussed in the context of the value of the KD concept for quantitative modelling of dissolved trace metal distribution in estuaries.

Particulate heating/cooling agents

Abstract: The invention discloses novel compositions of matter, in particulate forms, which function as heat transfer agents for heating or cooling applications. The particulates comprise solid carriers containing microwave responsive substances which are liquid at a predetermined elevated operating temperature. These particulate agents, preheated by microwave energy, serve as sources of dry heat or moist heat, depending on their composition. They also serve as sources of cold, when prechilled in a freezer.

Particulate flux of A1, a component of land origin, in the western North Pacific

Abstract: The particulate fluxes of A1 are generally greater in the western North Pacific than in the central and eastern North Pacific, Atlantic and Antarctic oceans. For instance, sediment trap data reported in this paper show the Al flux in the northern part of the Japan Trench is 12.7 mg m−2 day−1 at 5.2 km depth, 130 times greater than that in the deep Antarctic, even though total particulate fluxes are similar. The particulate fluxes of A1 extrapolated to the ocean surface layer roughly equals the observed A1 flux occurring at the ocean-atmosphere interface, suggesting that particulate A1 is atmospheric in origin. Excess A1 fluxes in the subsurface water probably indicate horizontal transport from the continental margin. This is indicated by the different Mg/K ratios of settling particles between the western and eastern North Pacific.

Pulsed, reverse-flow, regenerated diesel trap capturing soot, ash and PAH's

Abstract: A simple, low cost and reliable total particulate (soot, polynuclear aromatic and aliphatic hydrocarbons and ash) control system is disclosed that separates the particulate burning process from the body of a particulate filter and that needs very little compressed air to regenerate. The system can retrofit any existing diesel-powered equipment. The particulate control system includes a stationary ceramic monolith trap that is regenerated by one or more pulses of high-pressure and low-velocity air that move in the opposite direction of the engine exhaust flow through the trap. The particulate control system in a single trap embodiment conducts the engine exhaust to the atmosphere during regeneration periods, and in a dual trap embodiment, conducts the engine exhaust through two traps that are operated alternatively such that while one is filtering the exhaust the other is being regenerated, and vice versa.

Sulfur gases and aerosols in and above the equatorial African rain forest

Abstract: We determined the distribution of gaseous and particulate sulfur compounds in the canopy of the tropical rain forest of northern Congo and the overlying atmosphere during February 12–25, 1988. Hydrogen sulfide and dimethylsulfide decayed exponentially with altitude from approximately 30–40 ppt at ground level to 3–5 ppt at around 3 km altitude. Emission fluxes from the forest to the atmosphere were estimated by fitting a one-dimensional time-dependent numerical model of chemistry and transport of the sulfur compounds to their observed vertical profiles. Emission fluxes of 0.6–1.0 nmol H2S m−2 min−1 and 0.3–0.7 nmol DMS m−2 min−1 were consistent with the observed vertical profiles of H2S and DMS. These fluxes compare well with fluxes reported previously for the Amazon rain forest during the dry season and support the view of a subordinate role of land biota in the global cycling of sulfur. The particulate sulfur concentration of 248 ppt was found below the forest canopy. Biomass burning is considered to be an important contributor to this particulate sulfur. Carbonyl sulfide was found to be enhanced above the 500 ppt tropospheric background throughout the mixing layer of 2–3 km depth, likely due to biomass burning.