Showing papers on "Particulates published in 1988"

Stable carbon and nitrogen isotope biogeochemistry in the Delaware estuary

Abstract: ,Qbstract Seasonal variability in stable carbon (S’XZ) and nitrogen (b15N) isotope ratios was observed in suspended particulate matter of the Delaware estuary. Two major pools of organic matter were found in the estuary-phytoplankton growing in situ and a mixture of planktonic and terrestrial detritus. In general, the 6°C and 615N of suspended particulate matter reflected planktonic dominance. With the background chemical and physical information available for the estuary, it is evident that biogeochemical processes influence isotopic distributions in the estuary to a greater extent than does physical mixing. During spring, we postulate that isotopic fractionation of ammonium assimilated at concentrations >20 PM resulted in more negative 615N values for organic matter fixed by phytoplankton. As algal growth proceeded, the 615N of seston reached a maximum (+ 1 SY&) because phytoplankton were using a pool of NH,+ enriched in 15N as a result of previous fractionation during assimilation. Similarly, maximal 813C values were related to high rates of primary productivity associated with algal growth. Decreased isotopic fractionation occurred at high rates of production, implying that diffusion of CO, across the cell membrane became increasingly rate limiting. The 613C values in bottom sediments were equivalent to those in suspended particulate matter, but a 2Y60 difference in 615N was found between suspended and bottom sediments. With nitrogen isotopic differences between water-column seston and surficial sediments, we estimate that 1530% of planktonic production is deposited in the sediments during spring. If this organic matter is remineralized in late summer and fall, it could support up to 20% of primary production at that time.

Downward flux of particulate organic matter in the ocean: a particle decomposition paradox

Abstract: Oceanographers now recognize two distinct classes of particles in seawater, broadly categorized as suspended and sinking. The former class dominates the standing stock of particulate matter in the ocean and the latter class dominates the exchange between the surface waters and greater ocean depths1. The downward vertical flux of particulate organic matter (POM) in the open ocean exhibits a non-linear decrease with increasing water depth2–6, and greater than 75% of the net POM loss occurs in the upper 500 m of the water column6. Because sinking particles contain viable, metabolically active microorganisms7–12, the process of microbial decomposition is considered to be an important mechanism controlling POM flux. This model is consistent with the observed correspondence between POM flux and dissolved inorganic carbon concentrations13, and with the reported selective loss of biochemically labile compounds from sinking particles14–17. From our experiments, however, we conclude that the large sinking particles are, in general, poor habitats for bacterial growth and therefore unlikely sites for the active remineralization of organic matter. Our results require a shift in the emphasis of current ideas of particle decomposition from microbes attached to rapidly sinking particles to the microbial populations which are either free-living in the water column or attached to suspended (non-sinking) particulate matter.

High Combustion Temperature for the Reduction of Particulate in Diesel Engines

Abstract: Experiments on the effects of temperature T and equivalence ratio Φ on soot formation at high pressures up to 5 MPa were conducted. Discussion of the trajectory in relation to both soot and NO formation region gives suggestion of a possibility of high temperature ― rich mixture combustion to reduce particulate formation in diesel engines

Effect of sunlight on redox cycles of manganese in the southwestern Sargasso Sea

Abstract: The cycling of manganese between soluble Mn(II) and particulate manganese oxides was investigated in the upper 750 m at a station in the southwestern Sargasso Sea. Dissolved manganese was present at a maximum concentration (4.3 ± 0.6 nM) in the surface mixed layer (0–40 m) and decreased to 0.67 ± 0.19 nM at depths of 400–750 m. Particulate manganese, on the other hand, occurred at a minimum concentration (0.034 ± 0.012 nM) in the mixed layer and increased to a maximum of 0.41–0.48 nM at depths of 120–250 m. All of the increase in particulate manganese with depth occurred within the fraction that could be reductively dissolved by 0.3 mM ascorbic acid at ambient seawater pH, indicating that the rise resulted from an increase in the concentration of manganese oxides. Oxides were undetectable in the mixed layer, but a mean of 94% of the particulate manganese appeared to be associated with oxides at depths of 80–250 m. Radiotracer (54MnCl2) measurements of particulate formation rates and concomitant steady-state calculations of particulate turnover rates indicate that the low near-surface concentrations of particulate manganese resulted from both low formation rates and high turnover rates of particulate manganese. The formation of particulate manganese was sharply inhibited by sunlight, consistent with photoinhibition of manganese oxidizing microorganisms. Likewise, sunlight caused a 12-fold increase in the dissolution rate of 54Mn-labeled particulate manganese, which we attribute to photoreduction of manganese oxides. Both photo-effects appear to be important in sharply reducing the concentration of particulate manganese in near-surface seawater, and thereby minimizing the removal of manganese via particulate sinking. The resulting reduction in removal rates should be a major factor contributing to the surface maximum in manganese concentrations, which is a prominent feature of manganese profiles in much of the worlds ocean.

Particulate and dissolved phosphorus forms in freshwater: composition and analysis

Abstract: In recent research, particulate and dissolved phosphorus components have been separated and characterized on the basis of their physical and chemical properties and partly by their origins.

Thermocline ventilation of anthropogenic lead in the western North Atlantic

Abstract: Massive industrial aerosol emissions from North America have over the past century overwhelmed the natural distribution of lead in the western North Atlantic thermocline. The resultant features to 2000-m depth have been mapped near Bermuda for the year 1984. Since earlier reported measurements have largely been rejected on grounds of sample contamination, the twentieth-century evolution of anthropogenic Pb in the oceanic water column is unknown. Coupling of the 1984 water column Pb distribution to historical records in reef-building corals and tracer-derived thermocline ventilation rates (Jenkins, 1980) has permitted a model reconstruction of Pb penetration into the Sargasso Sea. The model is constrained by three distinct Pb distributions (Pb concentration, stable Pb isotopes, and 210Pb) with adjustable scavenging and regeneration parameters to account for nonconservative behavior. The results of the model substantiate the importance of lateral isopycnal ventilation while pointing out the necessity of dissolved-particulate exchange (i.e., scavenging τΓ of the order of 70 years in the deep thermocline; minimum regeneration of 10% particulate Pb between surface and 1700 m). Residual discrepancies between model isotopic predictions and observations below 800 m are likely due to a combination of the following factors: (1) presence of nonradiogenic background Pb in intermediate depth waters, (2) geographic variability in North American industrial source signatures, (3) Mediterranean Pb inputs of European origin, and (4) along-isopycnal mixing effects.

Chemiluminescence-based static and flow cytometry

Abstract: Apparati and methods of use for static and flow cytometry of cells and other particulate matter that eliminate the need for a laser or other external energy source to separate and/or detect differences in cells and other particulate matter wherein components of cells and other particulate matter interact with added thermally, chemically, electrochemically, photochemically or enzymatically decomposible chemiluminescent compounds, to produce light energy emissions optically detectable by said apparati.

Influence of Fuel Sulfur on Diesel Particulate Emissions

Abstract: An experimental program was conducted to evaluate the contribution of fuel sulfur to brake specific particulate emissions. Analysis of test results concluded that, among the factors investigated, fuel sulfur was the most important factor contributing to brake specific particulate sulfate variation. Combustion system, engine type, cycle loading, particulate makeup, had only a weak contribution to the brake specific sulfate variation

Time release cooling system

Abstract: Extended period cooling packs are provided by employing reaction mixtures of coated particulate matter and a liquid reactant, where the liquid reactant reacts with the particulate matter in an endothermic reaction. The coating acts to slow the rate of reaction between the reactants, so as to extend the period of cooling.

Development and evaluation of a novel gas and particle sampler for semivolatile chlorinated organic compounds in ambient air.

Abstract: A prototype annular diffusion denuder inlet has been adapted to a dichotomous sampler for the collection of organic compounds which occur in both the gas and particulate phase. The inlet selectively removes and efficiently preconcentrates atmospheric vapor-phase components by molecular diffusion prior to the collection of the particulate phase (coarse and fine fractions) by filtration. Backup adsorbent cartridges collect any vapor-phase constituents which might volatilize from the collected particulate matter and submicron particles which might penetrate the filter media. Special techniques were developed for coating the annular denuder with solid adsorbents. Laboratory tests with lindane and hexachlorobenzene have demonstrated better than 98% trapping efficiency over a 24-h sampling period at contaminant concentrations representative of ambient air and under most simulated atmospheric conditions.

Method and apparatus for separating fine particulates from a mixture of fine particulates and gas

Abstract: A method and apparatus for removal of fine particulate fly ash at high temperature and pressures using a bag filter which produces a clean gas stream that is recycled to compressors or power recovery turbines and a concentrated syngas stream blowdown from which additional solids are subsequently removed.

In vitro characterization and biomechanical optimization of a biodegradable particulate composite bone cement.

Abstract: We have developed a biodegradable particulate composite bone cement and used in vitro and in vivo methods for studying its suitability for orthopaedic applications. The composite matrix consists of gelatin, water, and sodium salicylate. The particulate phase is made up of powdered and particulate (355-600 microns diameter) tricalcium phosphate. Paraformaldehyde (0.1% to 0.5% by weight) is used as a matrix cross-linking agent. The effects of incubation time, particulate volume fraction, density of the individual particles, water content, concentration of crosslinking agent, and freeze-drying on the unconfined compressive strength and modulus of the particulate composite were measured. Compressive strengths of 7 MPa and moduli of 65 MPa could be achieved. Mechanical properties depended critically upon the water content of the particulate composite, with values of strength and modulus decreasing rapidly outside a range of 10-14% of specimen dry weight. High-density tricalcium phosphate particulate produced cement with twice the strength found with porous particulate. In a companion study we document in vivo performance of this particulate composite in an animal model system.

The reduction in diesel particulate emissions using emulsified fuels

Abstract: Although water injection or water/fuel emulsions are a well known method of reducing NO/sub x/ in stationary Diesel engines, their influence on Diesel particulates and particulate SOF has received little study. A single cylinder DI petter engine was used to investigate the influence of Diesel/water emulsions on particulate emissions and associated gaseous emissions. Water/fuel ratios of up to 20% were used and a strong influence on emissions was found. Both NO/sub x/ and particulate emissions were decreased with increased water content. However, there was a major increase in the unburnt hydrocarbons. Associated with this was a similar increase in the particulate solvent organic fraction and of the PAH fraction of this. These effects on UHC and PAH emissions make Diesel/fuel emulsions an unattractive solution to the Diesel NO/sub x/ and particulate emissions problems.

Particulate emissions from a mid-latitude prescribed chaparral fire

Abstract: Particulate emission from a 400-acre prescribed chaparral fire in the San Dimas Experimental Forest was investigated by collecting smoke aerosol on Teflon and glass-fiber filters from a helicopter, and using SEM and EDAX to study the features of the particles. Aerosol particles ranged in size from about 0.1 to 100 microns, with carbon, oxygen, magnesium, aluminum, silicon, calcium, and iron as the primary elements. The results of ion chromatographic analysis of aerosol-particle extracts (in water-methanol) revealed the presence of significant levels of NO2(-), NO3(-), SO4(2-), Cl(-), PO4(3-), C2O4(2-), Na(+), NH4(+), and K(+). The soluble ionic portion of the aerosol was estimated to be about 2 percent by weight.