Showing papers on "Particulates published in 1994"

Air pollution control engineering

Abstract: Introduction to air pollution control air pollution effects air pollution control laws and regulations, air pollution control philosophies air pollution measurements, emission estimates air pollution meteorology air pollution concentration models general ideas in air pollution control the nature of particulate air pollutants control of primary particulate air pollutants control of volatile organic compounds (VOC) control of sulphur oxides control of nitrogen oxides the motor vehicle problem air pollutants and the global climate other topics.

Production and transport of methane in oceanic particulate organic matter

Abstract: METHANE is an important component of the global carbon cycle1 and a potent greenhouse gas2,3. Surface ocean waters are typically supersaturated with dissolved methane relative to atmospheric equilibrium, presumably as a result of in situ microbial methane production4–8. Because methanogenic bacteria are strict anaerobes9and surface ocean waters are highly oxygenated, the observation of methane supersaturation has been termed the 'oceanic methane paradox'10. Although methanogenic bacteria have been isolated from oceanic particulate matter, faecal pellets and zooplankton11–14, no data are available on in situ rates of methane formation in these microenvironments. During a series of experiments in the North Pacific ocean, we have identified a previously unrecognized component of the oceanic methane cycle. We find that methane is associated with sinking particles, presumably as a dissolved constituent of the interstitial fluids of particulate biogenic materials, which exchanges with the water column as particles sink. This phenomenon provides a mechanism for the active transport in the water column of an otherwise passive, dissolved species. The particle-to-seawater methane flux that we measure is sufficient to replace all of the methane present in the upper water column in about 50 days and to produce the characteristic methane supersaturations in less than a month. We suggest that particulate production and transport may also be relevant to the redistribution and cycling of other bioreactive compounds in the marine environment.

Chemical Mass Balance Source Apportionment of PM10 during the Southern California Air Quality Study

Abstract: The chemical mass balance (CMB) receptor model was applied to the chemically speciated diurnal particulate matter samples acquired at nine locations in California's South Coast Air Basin (SoCAB) during the summer and fall of 1987 as part of the Southern California Air Quality Study (SCAQS) Source profiles applicable to the Los Angeles area were used to apportion PM25 and PM10 (particles with aerodynamic diameters < 25 and 10 μm, respectively) to primary paved road dust, primary construction dust, primary motor vehicle exhaust, primary marine aerosol, secondary ammonium nitrate, and secondary ammonium sulfate Suspended dust was the major contributor to PM10 during the summer, whereas secondary ammonium nitrate and primary motor vehicle exhaust contributions were high during the fall Secondary ammonium sulfate contributions were uniform across the SoCAB, with average contributions during the fall less than half those found during the summer Marine aerosol contributions were lower during the fall than

Coupling of near-bottom pelagic and benthic processes at abyssal depths in the eastern North Pacific Ocean

Abstract: A time-series site was established in the eastern North Pacific Ocean to study the coupling between near-bottom pelagic and benthic processes at abyssal depths in an area with well-documented seasonality in surface water productivity. Particulate total mass (PTM), particulate organic C (POC), particulate total N (PTN), and particulate calcium carbonate [P(CaCO,)] fluxes were measured from sediment trap collections at 600 and 50 m above bottom from February 1990 to October 199 1 (606 d). The sea floor at 4,100 m was concurrently monitored with a time-lapse camera over a 386-d period from July 1990 to July 199 1. During this study, in situ measurements of sediment community oxygen consumption (SCOC) were made and surface sediment samples collected seasonally with a free-vehicle grab respirometer. PTM, POC, PTN, and P(CaC0,) fluxes exhibited a strong seasonal signal, with episodic peaks from spring through fall and lows in winter. SCOC increased sharply between winter and summer, coinciding with spring peaks in particulate fluxes. Detrital aggregates appeared on the sea floor in pulses over a 6-month period from July to December 1990, coinciding with periods when particulate fluxes were elevated but delayed - 1.5 months after the initial peaks in particulate flux. Mobile epibenthic megafauna monitored with time-lapse photography consisted primarily of holothuroids and echinoids and were twice as active when detrital aggregates were observed on the sea floor as during the rest of the year. Our results show a temporal relationship between the flux of particulate matter entering the benthic boundary layer, the arrival and residence of detritus on the sea floor, and the activity of the sediment community and mobile epibenthic megafauna.

Fine mode aerosol composition at three long-term atmospheric monitoring sites in the Amazon Basin

Abstract: The Amazon Basin tropical rain forest is a key region to study processes that are changing the composition of the global atmosphere, including the large amount of fine mode aerosol particles emitted during biomass burning that might influence the global atmosphere. Three background monitoring stations, Alta Floresta, Cuiaba, and Serra do Navio, are operating continuously measuring aerosol composition. Fine (dp < 2.0 μm) and coarse (2.0 < dp < 10 μm) mode aerosol particles were collected using stacked filter units. Particle-induced X-ray emission was used to measure concentrations of up to 20 elements in the fine mode: Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr, and Pb. Soot carbon and gravimetric mass analysis were also performed. Absolute Principal Factor Analysis (APFA) has derived absolute elemental source profiles. APFA showed four aerosol particle components: soil dust (Al, Ca, Ti, Mn, Fe), biomass burning (soot, fine mode mass concentration, K, Cl), natural primary biogenic particles with gas-to-particle component (K, S, Ca, Mn, Zn), and marine aerosol (Cl). Biogenic and biomass burning aerosol particles dominate the fine mode mass concentration, with the presence of K, P, S, Cl, Zn, Br, and fine mode mass concentration (FPM). At the Alta Floresta and Cuiaba sites, during the dry season, a strong component of biomass burning is observed. Inhalable particulate matter (dp < 10 μm) mass concentration up to 700 μg/m3 was measured. Fine particle mass concentration alone can go as high as 400 μg/m3 for large regions. The fine mode biogenic and biomass burning components show remarkable similarities in the elemental composition, even though the sampling sites are more than 3000 km apart. Fine mode sulfur concentration is entirely associated with the primary biogenic aerosol particles, with gas-to-particle conversion and the biomass burning component. Large amounts of essential plant nutrients like P are mobilized into the atmosphere and possibly lost from the Amazon Basin ecosystem by long-range transport.

Photochemical Oxidant Processes in the Presence of Dust: An Evaluation of the Impact of Dust on Particulate Nitrate and Ozone Formation

Abstract: The influence of dust on the tropospheric photochemical oxidant cycle is studied through the use of a detailed coupled aerosol and gas-phase chemistry model. Dust is a significant component of the troposphere throughout Asia and provides a surface for a variety of heterogeneous reactions. Dust is found to be an important surface for particulate nitrate formation. For dust loading and ambient concentrations representative of conditions in East Asia, particulate nitrate levels of 1.5-11.5 micrograms/cubic meter are predicted, consistent with measured levels in this region. Dust is also found to reduce NO(x) levels by up to 50%, HO2 concentrations by 20%-80%, and ozone production rates by up to 25%. The magnitude of the influence of dust is sensitive to mass concentration of the aerosol, relative humidity, and the value of the accommodation coefficient.

Response of benthic oxygen demand to particulate organic carbon supply in the deep sea near Bermuda

Abstract: OVER the past decade an increasing body of evidence has accumulated indicating that much, perhaps most, of the deep sea floor is an environment of substantial temporal variability1–4. This variability is driven largely by seasonal changes of processes occurring in the surface waters2,3,5. The coupling of the deep sea floor environment to the surface waters is the result of rapid vertical transport of particulate matter through the water column6–8, affording only limited time for degradation before arrival at the sea floor. Studies in the Pacific Ocean have indicated that temporal variations in particulate organic carbon fluxes to the sea floor are accompanied by temporal variability in sediment oxygen demand by as much as a factor of four1,2. We report here time-series studies of oxygen fluxes into the sediments of the oligotrophic Atlantic near Bermuda which contrast sharply with these previous reports. At the Bermuda site, despite large seasonal variations in particulate organic carbon fluxes, in situ measured sediment oxygen consumption does not vary significantly. These results imply that large areas of the sea floor may be characterized by seasonally invariant sediment oxygen demand.

improvement of the wet-oxidation procedure for simultaneous determination of particulate organic nitrogen and phosphorus collected on filters

Abstract: A new digestion technique is presented for simultaneous analysis of particulate organic nitrogen (PON) and particulate organic phosphorus (POP) collected on filters. This method is based on a standard persulfate digestion procedure at 120°C and adapted from a former method for the simultaneous determinat~on of total nitrogen and total phosphorus in natural waters. Comparisons 1~1th usual methods using separate determinations for PON and POP indicate a high efficiency of the procedure for cell cultures or natural seawater samples. N~t ra t e and phosphate formed by oxidation can be analysed s~multaneously on an automated system. The procedure is highly suitable for routlne analysis and especially appropriate for shipboard use.

Well treating methods and devices 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.

Total suspended particulate matter and daily mortality in Cincinnati, Ohio.

Abstract: Recent studies have associated particulate air pollution with daily mortality in a number of U.S. communities. This study sought to replicate those analyses in Cincinnati, Ohio, and to test the str...

Ammonium Nitrate, Nitric Acid, and Ammonia Equilibrium in Wintertime Phoenix, Arizona

Abstract: A secondary aerosol equilibrium model, SEQUILIB, is applied to evaluate the effects of emissions reductions from precursor species on ambient concentrations during the winter in Phoenix, Arizona. The model partitions total nitrate and total ammonia to gas-phase nitric acid and ammonia and to particle-phase ammonium nitrate. Agreement between these partitions and ambient measures of these species was found to be satisfactory. Equilibrium isopleths were generated for various ammonium nitrate concentrations corresponding to high and low humidity periods which occurred during sampling. These diagrams show that ammonia is so abundant in Phoenix that massive reductions in its ambient concentrations would be needed before significant reductions in particulate ammonium nitrate would be observed. When total nitrate is reduced by reductions in its nitrogen oxides precursor, proportional reductions in particulate nitrate are expected. Many of the complex reactions in SEQUILIB do not apply to Phoenix, and its ability...

Detrital bedrock elements as tracers of settling resuspended particulate matter in a coastal area of the Baltic Sea

Abstract: Particulate matter settling out of the trophogenic layer was collected in sediment traps at five stations during 5 yr in a coastal area of the Baltic Sea. Al, Fe, and Ti in the intercepted matter were inferred to bc due mainly to the presence of fine-grained bedrock detritus and were used as markers to calculate the proportion of primary settling matter and resuspended sediment in the collected matter. Considerable variations within and between years, seasons, and nearby stations were found for gross sedimentation rate and for the ratio between primary settling matter and resuspended sediment. This pattern also applied to organic C. A predominance of primary settling matter was recorded mainly in spring. Resuspended matter was a large component in the annual budget for all years and stations. In fact, the resuspended portion commonly exceeded 50%, and periods without resuspension seem to occur rarely or never in the investigated area. The settling rate of particulate matter is a key variable in studies on pelagic biological production and benthic food supply, in efforts to model flows of energy and matter in ecosystems, in geochemical and biogeochemical mass balance calculations, and in studies on dispersion and dynamics of particle-borne elements and contaminants. Commonly, estimates of settling flux are obtained by means of sediment traps (Reynolds et al. 1980; Blomqvist and Hakanson 198 1; Walsh 1988; Jahnke 1990). The settling flux of fine particles in coastal limnetic and marine environments, as well as in nepheloid zones of aphotic ocean waters, often comprises a mixture of primary settling matter (i.e. material derived from the productivity of the trophogenic layer which has not

Effectiveness of Portable Indoor Air Cleaners: Sensory Testing Results

Abstract: The objective of this study was to test the effectiveness of individual commercially available portable indoor air cleaning units in removing dust particulates, tobacco smoke particulate and vapor phase constituents (nicotine and vinyl pyridine), viable and total fungal spores, pollen, and gaseous contaminants (carbon monoxide[CO], nitrogen dioxide[NO2], and formaldehyde[HCHO]), in a clean air test chamber. The air cleaner chamber results presented here represent initial-use results. In general, High Efficiency Particulate Air (HEPA) and electrostatic precipitator systems demonstrated the highest efficiencies with respect to particulate, contaminants, followed closely by electret filter systems. Ionizers and ozone generators were least effective in particulate removal. Systems which included sufficient sorbent material (i.e. activated carbon or potassium permanganate) were marginally effective at gaseous contaminant removal. None of the systems tested were effective at carbon monoxide removal. Sensory testing was conducted to discern potential correlation between human perceptive response and measured air cleaner performance (with respect to tobacco smoke removal). An electret filter (EF) loaded with carbon sorbent received the best ratings with respect to odor strength, nasal irritation, eye irritation, and overall air acceptability.

Dry deposition of ammonia and ammonium aerosols over heathland

Abstract: The dry deposition velocities of ammonia (NH3) and particulate ammonium were determined using the micrometeorological gradient method. About 130 measurements of 1 hour duration were conducted in the Netherlands from 1984 to 1987 in different seasons, mainly over heather/purple moor grass vegetation. The results show that NH3 is deposited more rapidly than other trace gases, such as ozone, sulfur dioxide or nitrogen dioxide. An average deposition velocity of 1.9 cm/s was observed during the measurements (most of them carried out during the daytime) over all heather locations. The average flux of NH3 during these periods was equivalent to 16 kg NH3/ha/yr. The canopy resistance for NH3 varied between close to zero and 150 s/m, which is low relative to the stomatal resistance to water vapor. The effect of several variables on the canopy resistance was investigated, but only that of surface wetness and air temperature was established clearly. The results indicate that wet vegetation acts as an almost perfect sink for NH3. The low canopy resistance observed and the lack of any diurnal variation suggest that uptake at the leaf surface is relevant. No clear-cut difference between the various locations was found. The observed variation in the measured deposition velocities could be explained to some 60% with a surface layer resistance model on the basis of fluctuations in meteorological variables, surface wetness, and air temperature. To obtain an estimate of the long-term average deposition velocity of NH3, we used a surface-layer model to account for the effect of nighttime meteorology. Measurements and calculations indicate an annual average 24-hour deposition velocity to heathland of 1.4 cm/s. For particulate ammonium, only one in 10 measurements leads to flux values significantly higher than the detection limit of the method, owing to the low deposition velocity of particulate NH4+. The average flux measured is equivalent to 3.8 kg NH4+/ha/yr. The annual average 24-hour dry deposition velocity for particulate NH4+ is 0.17 cm/s. Under the circumstances encountered in the Netherlands, only about 20% of NHx dry deposition was by way of dry deposition of particulate NH4+. For a typical site in the Netherlands the dry deposition was about 50% of the estimated input by wet deposition.

Evaluation of filter-based aerosol measurements during the 1987 Southern California Air Quality Study.

Abstract: The Southern California Air Quality Study (SCAQS) was conducted during the summer and fall of 1987 to assess the causes of elevated ozone and suspended particulate matter concentrations in California's South Coast Air Basin (SoCAB). Extensive gaseous (i.e. nitric acid, ammonia, sulfur dioxide) and particle (i.e. PM2.5 and PM10 mass, elements, ions, carbon) measurements were acquired for 11 days during the summer at nine locations, and six days during the fall at six locations. Outliers were identified so that they could be excluded from further statistical analyses. Carbon and elemental measurements were found to be negatively biased by ∼ 20% owing to inhomogenous aerosol deposits on the SCAQS filters and analysis methods which were applied to a portion of the filters. These biases seem relatively consistent, however, and should not affect conclusions drawn from data analysis efforts if they are appropriately considered. Significant fractions (30–60%) of ammonium nitrate volatilized during the summer when temperatures were higher. Less than 10% typically volatilized during the fall when temperatures were lower. Anion/cation balances support the accuracy and precision estimates of the nitrate, sulfate, and ammonium measurements. Coarse particle sulfate was generally low, while coarse particle nitrate was most pronounced at the coastal sites. This paper documents SCAQS filter-based aerosol measurement methods, and evaluates the accuracy, precision, and validity of the data set. Various comparisons were made for: (1) PM2.5/PM10 ratios for mass and major chemical species; (2) sum of chemical species versus measured mass; (3) sulfate versus sulfur ratios; (4) PM2.5 particulate nitrate versus nitric acid-denuded nitrate; and (5) anion/cation balances. The measurement and evaluation techniques presented in this paper serve as a guideline for other data analysis and modeling studies.

Nonparticulating adsorbent recirculating filter

Abstract: The present invention is a sorbent filter for use in both particulate filtration and absorption of gaseous contaminants in a variety of applications, such as for filtration in a computer disk drive. The filter of the present invention provides previously unavailable levels of combined particulate filtration and contaminant sorption while being capable of ready reconditioning (such as through washing with D.I. water).

A flow-through particulate incineration system coupled to an aerodynamically regenerated particulate trap for diesel engine exhaust gas

Abstract: A flow-through particulate incineration system is coupled to an aerodynamically regenerated diesel engine exhaust gas particulate (soot, condensed polynuclear aromatic and aliphatic hydrocarbons and ash) trap (418). An incineration chamber (430) is provided downstream of the particulates dislodged from the particulate trap (418) during regeneration thereof by a pulse of compressed air. During regeneration, a valve (434) between the particulate trap (418) and the incineration chamber (430) opens to allow the air and entrained particles to pass into the incineration chamber (430) to allow passage of the regeneration air therethrough, but prevent passage of the particulates, whereby the particulates are retained in the incineration chamber (430). A heater (464) in the incineration chamber is periodically activated to burn the particulates collected in the trap. The oxidation products may be exhausted to ambient or may be returned to the engine intake (472) in an exhaust gas recirculation system.

Rapid post-bloom resuspension in the northeastern Atlantic

Abstract: The importance of particulate matter input on the seafloor following spring bloom and of resuspension processes in middle and high latitudes of the north Atlantic ocean has been recently emphasized. However the possibility of the coupling between both processes until now, has not been reported. To study the fate of the particulate matter after its arrival on the bottom, a deep-sea observatory has been launched in the NEA (Nuclear Energy Agency) area of the northeastern Atlantic abyssal hill province. Time series of botton currents, near bottom particle concentration measurements and time lapse photographs were obtained from March to July 1988, while particulate matter fluxes were recorded with a sequential sediment trap. The most interesting results are the observation of a series of events starting with the arrival on the bottom of 5–10 mm aggregates following the spring bloom, their disaggregation within 2 weeks immediately followed by a rise of the near-bottom particle concentration, concomitant with the passage of a bottom current eddy. These observations illustrate how rapid disaggregation rates may lead to resuspension following high particulate matter input.