Showing papers on "Particulates published in 1991"

Do upper-ocean sediment traps provide an accurate record of particle flux?

Abstract: SEDIMENT traps are widely used to measure the vertical flux of particulate matter in the oceans. In the upper ocean, sediment traps have been used to determine the extent to which CO2 Axed by primary producers is exported as particulate organic carbon1–3. In addition, the observed decrease of particle flux with depth has been used to predict regeneration rates of organic matter and associated elements3. Over seasonal or annual timescales, the import of limiting nutrients into the upper ocean (new production) should be balanced by particle export4,5. Given the importance of accurately determining the sinking particle flux, it has been suggested that 234Th might be used to 'calibrate' shallow-trap fluxes6. Here I present a re-evaluation of existing 234Th data which indicates that trap-derived and model-derived 234Th particle fluxes can differ by a factor of ±3–10, suggesting that shallow traps may not provide an accurate measure of particle fluxes.

Los Angeles Summer Midday Particulate Carbon: Primary and Secondary Aerosol

Abstract: Aerosol sampling during photochemically active times across the Los Angeles Basin has provided evidence of secondary formation of organic aerosol from gas-phase precursors at midday. Ambient organic carbon/elemental carbon ratios exceeded the estimated ratio of organic carbon/elemental carbon in primary source emissions on most sampling days at all sites. The concentration of secondary organic aerosol was calculated by using ambient data and estimates of the organic carbon/elemental carbon ratio in primary source emissions. Nonparametric sign correlations comparing calculated secondary organic carbon concentrations with tracers of both primary and secondary aerosols supported the method used to quantify secondary organic carbon. Secondary organic aerosol appears to have contributed roughly half of the organic aerosol in Pasadena during midday summer conditions.

Chemical and biological characterization of particulate-, semivolatile-, and gas-phase-associated compounds in diluted heavy-duty diesel exhausts: a comparison of three different semivolatile-phase samplers

Abstract: Exhaust emission from a heavy-duty diesel vehicle during transient driving conditions have been characterized chemically and tested for mutagenicity. Both the particulate phase and the semivolatile phase were investigated chemically and by the Ames test. Three different sampling techniques, i.e., cryocondensation and two adsorbents XAD-2 and polyurethane foam (PUF), were used for collection of the semivolatile phase together with a particulate filter situated upstream. The cryogenic technique was the least efficient type and the PUF technique gave the highest recovery of polycyclic aromatic hydrocarbons (PAH) and mutagenic activity. The amount of PAH, mainly three-ringed PAH, emitted in the semivolatile phase was approximately 3 time higher than that emitted in the particulate phase. The contribution of the semivolatile phase to the total mutagenicity was approximately 20% in strain TA100 {plus minus} S9, 10% in strain TA98-S9, and 37% in strain TA98 + S9. The results thus show the importance of both particulate- and semivolatile-phase-associated compounds when possible health effects from diesel engine exhausts are being considered.

Sulfur, iron and organic carbon fluxes in the Black Sea: sulfur isotopic evidence for origin of sulfur fluxes

Abstract: In the southern and central Black Sea, reduced sulfur comprises nearly 1% of the total particulate flux in the anoxic water column, as measured by time-series sediment traps. Sulfur isotopic composition of particulate sulfide fluxes indicates an origin near the oxic-anoxic interface, where dissolved sulfide is isotopically heavier than dissolved sulfide below 175 m due to chemical oxidation A strong seasonal correlation exists between sulfur and organic carbon fluxes; this, together with particulate sulfide precipitation at the oxic-anoxic interface, suggests that sulfides are scavenged from the interface during maximum production of settling organic aggregates, particularly during the late summer coccolithophorid blooms. Sulfide precipitation deeper in the water column and in sediments may be limited by availability of iron and/or polysulfides, since there are no particulate sulfide fluxes which have the same isotopic composition as ambient dissolved sulfide at trap depths. Since sulfides in surface sediments are often isotopically similar to dissolved sulfide at the top of the sulfide zone and to sediment trap fluxes, sedimentary sulfides could originate from metal sulfide fluxes forming at the oxic-anoxic interface and would reflect sulfur-cycling processes at the oxic-anoxic interface Sedimentary sulfate reduction rates estimated from assuming 65–80% utilization of particulate organic carbon fluxes agree reasonably well with other estimates of sulfate reduction and sulfide production rates. A sulfur isotope-based box model for sulfur cycling between dissolved and particulate phases in the water column and sediments is presented.

Particulate and Trace Gas Emissions from Large Biomass Fires in North America

Abstract: This chapter contains sections titled: Particle Emission Factors, Particle Size Distributions, Optical Properties, Biomass Smokes as a Source of Cloud Condensation Nuclei, Cloud and Precipitation Scavenging of Smokes, Trace Gas Emissions, Summary and Conclusions, Acknowledgments

Anthropogenic mercury emission in Europe

Abstract: Preliminary estimates of Hg emissions from anthropogenic sources in Europe have been prepared to meet the request of air pollution transport modeling. Major emphasis was placed on four source categories: 1) combustion of fossil fuels, 2) non-ferrous metal production, 3) waste related sources, and 4) chlor-alkali production. Three chemical species: elemental, bivalent and particulate Hg were considered in these estimates. The emission estimates were spatially distributed within the EMEP grid of 150 km × 150 km for the year 1982.

Mercury and methylmercury in sediments and suspended particles from the river Elbe, North Germany

Abstract: Total Hg and McHg concentrations have been determined in sediments and suspended particulate matter from one of the most Hg-polluted rivers of the world, the Elbe river in Northern Germany. Results of total Hg and McHg are presented. Total Hg concentrations in suspended particulate matter (SPM) are 30 mg kg−1 in the average and up to 150 mg kg−1 as the maximum value. Total Hg-fluxes −1 calculated from measurements of an automatically operating station upstream Hamburg as about 17 ta−1 in suspended particles. A new McHg determination by HPLC chromatography and photometric detection was developed and verified. Methylmercury concentrations were up to 10% of the total Hg, i. e. 2.7 mg kg−1 (dw).

Suspended particulate organic matter in a Mediterranean submarine cave

Abstract: Submarine caves display a paucity of benthic density and biomass that may be related to low trophic resources. Analysis of organic carbon, organic nitrogen, carbohydrate, protein and lipid content of suspended particulate matter was made during the period July 1985–July 1987 in a Mediterranean cave (Marseille, France) in order to determine any differences in the particulate organic matter composition along an horizontal transect. Particulate organic matter content clearly declined from the entrance of the cave to the dark inner area. This impoverishment could not be explained by a simple decrease in a few organic compounds, but appeared to be related to the combination of a decrease in both the amount and the composition of the suspended particles. Three progressive levels of impoverishment were identified towards the dark inner area of the cave: (i) decreasing amounts of seston; (ii) decreasing organic content of particles; (iii) increasing proportions of the geopolymeric (i.e., humic) components in the remaining organic matter, indicating increased degradation. The cave appeared to be sharply divided into two distinct sections — a twilight outer section whose waters contained slightly lower amounts of particulate organic matter than the open sea, and a dark inner section, 8 to 10 m higher, separated from the outer section by a steep rise and with waters of low organic matter content. The water in the twilight section appeared to be in thermal equilibrium with the open sea, and that in the dark inner section displayed thermal stratification. These differences indicated the presence of two distinct water bodies with contrasting average residence times, estimated as 1 d in the outer twilight section and 8 d in the dark inner section. The joint action of sedimentation and degradation resulted in an abrupt depletion of particulate organic matter in the dark inner section accompanied by a decrease in the benthic fauna. The decline in benthic heterotroph populations is probably related to the abrupt transition to oligotrophic conditions.

Reduction of foreign particulate matter on semiconductor wafers

Abstract: A substantial reduction in the foreign particulate matter contamination on surfaces, such as the surfaces of semiconductor wafers, is achieved by treating the surfaces with a solution comprising a strong acid and a very small amount of a fluorine-containing compound. A preferred method employs a solution containing sulfuric acid, hydrogen peroxide and a very small amount of hydrofluoric acid, which is effective in reducing foreign particulate matter contamination, without significant etching, of the surface being treated.

Organic Matter Sources in the Black Sea as Inferred from Hydrocarbon Distributions

Abstract: Suspended and sinking particulate matter from the water column and sediment and fecal pellets from Unit I sediments were collected in the central basin of the Black Sea for organic geochemical investigations. The hydrocarbon compositions of these samples proved informative for providing information on the sources for the particulate and sedimentary organic matter. Hydrocarbons derived from planktonic, terrestrial, bacterial, and fossil sources can be distinguished. Plankton-derived hydrocarbons dominated the 53 µm particles. By contrast, 53 µm) particles in the anoxic zone contained equal amounts of hydrocarbons from all four sources. Fecal pellets and sediments contained the greatest contribution of hydrocarbons of terrestrial origin (up to 56% of total hydrocarbons).

Variability and transport of suspended sediment, particulate and dissolved organic carbon in the tidal freshwater Hudson River

Abstract: Measurements of suspended matter, particulate organic carbon and dissolved organic carbon were made over a three year period at stations spanning 150 km of the tidal freshwater Hudson River. Suspended matter concentrations varied from year-to-year and were not related to freshwater discharge. The increase in suspended matter with depth in vertical profiles suggests that, during medium to low flow conditions, resuspension of bottom sediments was as important a source of sediment as loadings from tributaries. Particulate organic carbon showed significant variability among stations, and both autochthonous primary production and detrital organic matter are contributing to POC standing stocks. Dissolved organic carbon represented over half of the total organic carbon in the water column and showed little variation among stations.

Removal of particulate matter from combustion gas streams

Abstract: Unburned particulate matter is removed from a combustion gas stream by adding a conditioning agent to modify the resistivity of the particulate matter and passing the conditioned combustion gas stream through an electrostatic precipitator whose precipitating elements are energized with an intermittent applied voltage. The addition of conditioning agent and the precipitating voltage signal are mutually optimized. A controller receives measurement signals from sensors that monitor the total flow rate of particulate matter in the gas stream before the electrostatic precipitation treatment, and the concentration of particulate matter in the gas stream after the treatment. Performance of the system may be optimized according to selected combinations of variables.

Aerosol chemical components in Alaska air masses: 2. Sea salt and marine product

Abstract: The inhomogeneity of the aerosol chemistry for a 4-year data set from the geographic central region of Alaska expressed through loading of principal components provides provisional multivariate statistical identification for components of nonanthropogenic (apparently natural) sources of particles. Besides an Al-rich dust which is generally present but is slightly elevated in summer months, a marine sea-salt component of aerosol is detectable as well as a Br component. The marine sea-salt component was most evident when air over the ocean flowed behind the Alaska mountain range barrier from the Bering Sea and entered into the flat river floodplain of interior Alaska, undergoing little or no orographic lifting in the process. During such flow patterns, marine components such as sodium, chlorine, potassium, arid selenium are enhanced by up to a factor of 10 from average, but these very components are also attenuated strongly during forced overmountain “chinook” flow. We hypothesize that the sea-salt deficiency for the latter flow is due to nucleation and rainout on the windward side of the Alaska mountain range and calculate that this is plausible. Chlorine in sea salt is evidently volatilized and released from the particulate phase, leading to a severalfold depletion relative to sodium aerosol during incursions of acid-rich pollution aerosol from the Arctic. Bromine in aerosol in the central geographic region in Alaska undergoes a large (×10) enhancement each year in late March to early April in affiliation with flow of air from the Arctic.

Trace Gas and Particulate Emissions from Biomass Burning in Temperate Ecosystems

Abstract: Emissions measured from fires in graminoid wetlands, Mediterranean chaparrals, and boreal forests, suggest that such ecosystemic parameters as fuel size influence combustion emissions in ways that are broadly predictable. The degree of predictability is most noticeable when wetland fire-related results are compared with boreal forest emissions; the inorganic fraction of the particulate emissions is close in composition irrespective of the ecosystem. It is found that both aerosol and trace gas emissions are influenced by the phase of combustion.