Showing papers on "Particulates published in 1996"

Elemental Carbon-Based Method for Monitoring Occupational Exposures to Particulate Diesel Exhaust

Abstract: Diesel exhaust has been classified a probable human carcinogen, and the National Institute for Occupational Safety and Health (NIOSH) has recommended that employers reduce workers' exposures. Because diesel exhaust is a chemically complex mixture containing thousands of compounds, some measure of exposure must be selected. Previously used methods involving gravimetry or analysis of the soluble organic fraction of diesel soot lack adequate sensitivity and selectivity for low-level determination of particulate diesel exhaust; a new analytical approach was therefore needed. In this paper, results of investigation of a thermal-optical technique for analysis of the carbonaceous fraction of particulate diesel exhaust are reported. With this technique, speciation of organic and elemental carbon is accomplished through temperature and atmosphere control, and by an optical feature that corrects for pyrolytically generated carbon, or “char,” which is formed during the analysis of some materials. The therma...

Flow-induced uptake of particulate matter in permeable sediments

Abstract: We demonstrate the fast transfer of suspended particles from the boundary layer into the upper strata (z 2 x 10-l l m2) incubated in a laboratory flume. Increased pressure up- and downstream of small mounds (z = 2.5 cm) drove water 5.5 cm into the core, carrying suspended particles (1 pm) to 2.2-cm sediment depth within 10 h. Simultaneously, decreased pressure at the downstream slope of the protrusions drew pore fluid from deeper layers (z 5 10 cm) to the surface. In the sediment, friction reduced the velocity of the particulate tracers, resulting in size fractionation and layers of increased particle concentration. Ripple topography (0.8-2.8 cm high) enhanced interfacial particle (1 pm) flux by a factor 2 .3 when compared to a level control core. The pathways of the particle and solute tracers below a sediment ripple are explained with a source-sink model that describes the pore flow velocity field. Our results suggest that bedform-induced interfacial flows are important for the uptake of particulate organic matter into permeable shelf sediments.

Oxidant Generation and Lung Injury after Particulate Air Pollutant Exposure Increase with the Concentrations of Associated Metals

Abstract: We tested the hypothesis that particulate air pollutants are associated with metals that have a capacity to transport electrons and that biologic activity of the particulates can correlate with the concentrations of these metals. The metals studied were titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper. Measurements included (1) oxidized products of deoxyribose catalyzed by particulates, (2) induction of a neutrophilic alveolitis after particulate instillation, (3) increments in airway reactivity after particulate instillation, and (4) mortality after exposures to both dusts and a microbial agent. Employing 10 different dusts of either natural or anthropogenic origin, in vitro generation of oxidized products of deoxyribose increased with ionizable concentrations of all metals, except for titanium, associated with the particles. After tracheal instillation of dust into rats, both the neutrophil influx and lavage protein increased with ionizable concentrations of these same m...

Elemental carbon-based method for occupational monitoring of particulate diesel exhaust: methodology and exposure issues.

Abstract: Diesel exhaust has been classified a probable human carcinogen, and the National Institute for Occupational Safety and Health (NIOSH) has recommended that employers reduce workers' exposures. Because diesel exhaust is a chemically complex mixture containing thousands of compounds, some measure of exposure must be selected. Previously used methods involving gravimetry or analysis of the soluble organic fraction of diesel soot lack adequate sensitivity and selectivity for low-level determination of particulate diesel exhaust; a new analytical approach was therefore needed. In this paper, results of investigation of a thermal–optical technique for the analysis of the carbonaceous fraction of particulate diesel exhaust are discussed. With this technique, speciation of organic and elemental carbon is accomplished through temperature and atmosphere control and by an optical feature that corrects for pyrolytically generated carbon, or ‘char,’ which is formed during the analysis of some materials. The thermal–optical method was selected because the instrument has desirable design features not present in other carbon analysers. Although various carbon types are determined by the method, elemental carbon is the superior marker of diesel particulate matter because elemental carbon constitutes a large fraction of the particulate mass, it can be quantified at low levels and its only significant source in most workplaces is the diesel engine. Exposure-related issues and sampling methods for particulate diesel exhaust also are discussed.

Role of Photoinduced Charge Carrier Separation Distance in Heterogeneous Photocatalysis: Oxidative Degradation of CH3OH Vapor in Contact with Pt/TiO2 and Cofumed TiO2−Fe2O3

Abstract: As a means of testing the widely held premise of a positive correlation between photoinduced charge carrier separation distance (CCSD) and the photocatalytic activity of particulate photocatalysts, an investigation of the oxidative degradation of CH3OH vapor in contact with coatings of particulate Pt (0−8 wt %)/TiO2 is combined with time-resolved photocharge (TRPC) measurements. Preliminary studies were also performed on several commercially available cofumed Fe2O3−TiO2 (0, 2, and 6−8 wt % Fe) particulate photocatalysts. TRPC is capable of providing a noncontact electronically derived measure of CCSD. Contrary to common wisdom prevalent at the initiation of this study, Pt/TiO2 catalysts displaying the largest CCSD values do not correspond with highest photocatalytic efficiency for the oxidative degradation of CH3OH. Indeed the present investigation supports an extension of a “Russell-like” mechanism for oxidative degradation of organic molecules, where photoelectrons, e-, and photoholes, h+, each initiate...

Humic-like substances in air pollution particulates correlate with concentrations of transition metals and oxidant generation

Abstract: We tested the hypotheses that (1) an incomplete oxidation of carbon-based fossil fuels during their combustion produces humic-like substances (HIS), which can be present in air pollution particulates and confer a capacity to complex metals; (2) air pollution particulates collected on PM10 filters can be associated with concentrations of first-row transition metals; (3) particulates can catalyze the production of free radicals by cycling these transition metals through two stable valence states; and (4) concentrations of transition metals and oxidant generation by air pollution particulates increase with the content of HLS associated with these particles. HLS were isolated by alkali extraction. The content of these substances in combustion products of coal, diesel, oil, and wood was 3.1 ± 0.8%, 4.7 ± 1.0%, 1.0 ± 0.1%, and 8.2 ± 0.6%, respectively. Similarly, filters with sequestered air pollution particulates contained HLS ranging from 0.0 to 7.1%. Elemental analysis of these materials isolated fro...

Mutagenic activity of total and particle-sized fractions of urban particulate matter

Abstract: Total or inhalable (PM 10 ) particulate matter is monitored as a quality air criteria. Airborne particles deposit onto the differently sensitive biological tissues of the respiratory tract depending on their size. So it is very important to know the mutagenic activity (index of potential carcinogenicity) of the substances carried onto the diverse sized fractions of urban particulate matter, especially those under 1 μm in diameter. The mutagenicity of total and sized fractions of urban particulate matter of Bologna (Italy), representative of a medium size town surrounded by small and medium industries, was investigated using the plate incorporation test on Salmonella typhimurium. There is no correlation between total and/or coarse particle matter concentration in air and mutagenic activity, the correlation increases as the particle size decreases ; moreover, the finer the particulate matter, the greater the mutagenicity is. That is of great concern for health risk estimation. Total or inhalable (PM 10 ) particulate matter is not representative of air quality, at least with regard to the mutagenicity.

Atmospheric sulfur over the east Mediterranean region

Abstract: Particulate sulfate has been measured intermittently at various ground sites in Israel and from an instrumented aircraft for a 10-year period between 1984 and 1993. The measurements were accompanied by concurrent monitoring of primary and secondary air pollutants and meteorological parameters. In three studies, Etzion 1984–1986, Jerusalem 1987–1988, and Jerusalem 1990–1991, measurements were taken for at least a year. The other studies were performed during summer months when higher levels of secondary pollutants, including particulate sulfate, were observed. In most of the studies samples were taken for four sequential 6-hour time segments. In one study, at Caesarea 1993, sulfate samples were taken only when wind flows were perpendicular to the coastline. The airborne measurements were performed along three north-south paths inside the planetary boundary layer, over the Mediterranean coast, over the Judea-Samaria mountains and over the Jordan Valley. Each flight path consisted of 30 to 45 minutes of continuous sampling of SO2 and one integrated sample of particulate sulfate. In all of our studies the concentration of particulate sulfate observed was relatively high compared with other world locations. The highest values, occasionally exceeding 500 nmole m−3, were found during the summer. Wintertime levels were in the range of 50–100 nmole m−3. The annual average, calculated for the three long studies, is 100 ± 15 nmole m−3, which is twice as high as predicted for the region by a global model and as high as reported for some of the more polluted regions in the US. Several indicators suggested that the origin of the sulfate in the region is not from local sources but the result of long range transport. The indicators include the lack of correlation between particulate sulfate and primary pollutants, the high sulfate to total sulfur values, the origin of the airmass back trajectories and the fact that similar levels were observed during concurrent periods at different sites. Throughout the study, higher concentration of particulate sulfate was found during the afternoon hours, especially during the summer and at the inland locations. The contribution to the afternoon elevated values could not be associated with long range transport and results probably from major sulfur emission sources located along the Israeli Mediterranean coast.

Simultaneous control of particulate and NOx emissions from diesel engines

Abstract: In view of increased concerns regarding the effects of diesel engine particulate and NO x emissions on human health and the environment, legislators are currently reviewing and proposing legislation targeting the reduction of these pollutants. The reported serious health risks of particulate matter on the respiratory system and its carcinogenic effects, along with the known contributions of NO x in acid rain and ground ozone formation, demand that the enacted legislation reflect in severity the health and environmental threats. As a consequence, diesel engine manufacturers and users are under increasing pressure to greatly reduce the engine's exhaust emissions. A system which is currently being proposed for the simultaneous control of diesel particulate matter and NO x emissions involves the use of a cerium fuel-borne catalyst/filter/EGR system. This paper describes the principles of operation of Rhoˆne-Poulenc's cerium fuel-borne catalyst and the factors that govern its use.

Trace metals in the central and southern North Sea

Abstract: Measurements of both dissolved and particulate trace metals (Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn) were made on samples collected simultaneously in the central and southern North Sea (below 56°N), during four cruises covering the seasonal cycle. Analyses of trace metals in both phases were undertaken using similar analytical protocols, and the data subjected to rigorous quality controls. Clean techniques were used throughout sampling and analysis. Trace metal concentrations ranged from those characteristic of waters entering the shelf region from the North Atlantic Ocean to values which in some cases were two orders of magnitude higher. Marked increases in concentrations were often associated with waters directly influenced by riverwaters, but the results showed that the distributions could be influenced by processes other than fluvial inputs. The redox-sensitive metals, Fe and Mn, were influenced at some sites, including those overlying areas of fine-grained sediments, by benthic inputs associated with seasonal changes in oxidation-reduction conditions in the benthic interfacial zone. The behaviour of metals which are not redox-sensitive (Cd, Zn) in some cases paralleled those of Fe and Mn, suggesting an association with Mn-or Fe-rich solid phases, or with organic matter. However, seasonal variations in concentrations of Cd and Zn were not directly linked to the cycle of biological utilization and regeneration of nutrients, suggesting that their geochemistry is more influenced by boundary inputs. Resuspension of Pb-rich sediments, long-range transport of Pb-rich suspended particulate matter (SPM), and enhanced, though diffuse, atmospheric inputs of lead were considered to have contributed to the elevated concentrations of particulate Pb (mass metal/mass sediment) in the water column during winter. Estimates of partitioning (K D s) were derived from the dissolved and particulate data for each of the metals over the seasonal cycle. For the more particle-reactive metals (Co, Fe, Mn, Pb), transport in the suspended particulate phase is a significant, sometimes dominant factor. In contrast, for Cd, Cu and Zn, transport in solution will dominate under almost all conditions in the southern North Sea. Furthermore, the values of K D , for a particular metal, varied widely, partly in response to seasonal differences in the relative contributions of lithogenous and biogenous particles to the particles in suspension. Only for Cu and Zn during the winter could the partitioning be described by a narrow range of K D values covering the observed concentrations of SPM. The data from this study give unique information concerning the contemporaneous distribution of dissolved and particulate trace metals in the southers North Sea and they provide a baseline against which the effects of reductions of inputs into the North Sea may be more accurately assessed. Viewed in combination, the dissolved and particulate data have yielded new insights into mechanisms affecting trace metal cycling and transport, essential in the development of coupled hydrodynamic-geochemical models.

Method and apparatus for cleaning a vacuum line in a CVD system

Abstract: An apparatus for preventing particulate matter and residue build-up within a vacuum exhaust line of a semiconductor processing device. The apparatus uses RF energy to form excite the constituents of particulate matter exhausted from a semiconductor processing chamber into a plasma state such that the constituents react to form gaseous products that may be pumped through the vacuum line. The apparatus may include a collection chamber structured and arranged to collect particulate matter flowing through the apparatus and inhibiting egress of the particulate matter from the apparatus. The apparatus may further include an electrostatic collector to enhance particle collection in the collection chamber and to further inhibit egress of the particulate matter.

Overview of the atmospheric research program during the International Arctic Ocean Expedition of 1991 (IAOE-91) and its scientific results

Abstract: The broad aim of the Atmospheric program of the International Arctic Ocean Expedition (IAOE-91) was to test the hypothesis that marine biogenically produced dimethyl sulfide (DMS) gas can exert a significant global climatic control. The hypothesis states that DMS is transferred to the atmosphere and is oxidised to form airborne particles. Some of these grow large enough to act as cloud condensation nuclei (CCN) which help determine cloud droplet concentration. The latter has a strong influence on cloud albedo and hence on the radiation balance of the area affected. In summer, the central Arctic is a specially favourable region for studying the natural sulfur cycle in that the open waters surrounding the pack ice are the only significant sources of DMS and there are almost no anthropogenic particle sources. Concentrations of seawater and atmospheric DMS decreased at about the same rate during the period of measurements, (1 August to 6 October, latitudes 75°N to 90°N) spanning about three orders of magnitude. Methane sulfonate and nonsea salt sulfate in the submicrometer particles, which may be derived from atmospheric DMS, also decreased similarly, suggesting that the first part of the hypothesis under test was true. Influences on cloud droplet concentration and radiation balance could not be measured. Size-resolved aerosol chemistry showed a much lower proportion of methane sulfonate to be associated with supermicrometer particles than has been found elsewhere. Its molar ratio to nonsea salt sulfate suggested that the processes controlling the particulate chemistry do not exhibit a net temperature dependence. Elemental analysis of the aerosol also revealed the interesting possibility that debris from Siberian rivers transported on the moving ice represent a fairly widespread source of supermicrometer crustal material within the pack ice. Highly resolved measurements of aerosol number size distributions were made in the diameter range 3 nm to 500 nm. 3 distinct modal sizes were usually present, the “ultrafine”, “Aitken” and “accumulation” modes centred on 14, 45 and 170 nm diameter, respectively. The presence of ultrafine particles, implying recent production, was more frequent than has been found in lower latitude remote marine areas. Evidence suggests that they were mixed to the surface from higher levels. Sudden and often drastic changes in aerosol concentration and size distribution were surprisingly frequent in view of the relatively slowly changing meteorology of the central Arctic during the study period and the absence of strong pollution sources. They were most common in particles likely to have taken part in cloud formation (> 80 nm diameter). 2 factors appear to have been involved in these sudden changes. The 1st was the formation of vertical gradients in aerosol concentration due to interactions between particles and clouds or favoured regions for new particle production during periods of stability. The 2nd was sporadic localised breakdowns of the stability, bringing changed particle concentrations to the measurement level. Probable reasons for these sporadic mixing events were indicated by the structure of the Marine Boundary Layer (MBL) investigated with high resolution rawinsondes. Low level jets were present about 60% of the time, producing conditions conductive to turbulence and shear-induced waves. It is concluded that an even more detailed study of meteorological processes in the MBL in conjunction with more highly time-resolved measurements of gas-aerosol physics and chemistry appears to be essential in any future research aimed at studying the indirect, cloud mediated, effect of aerosol particles. DOI: 10.1034/j.1600-0889.1996.t01-1-00002.x

Toxic potencies of lipophilic extracts from sediments and settling particulate matter (SPM) collected in a PCB-contaminated river system

Abstract: Sediments and settling particulate matter (SPM) were sampled in a polychlorinated biphenyl (PCB)-contaminated lake, Lake Jarnsjon, and in lakes located up-/and downstream from Lake Jarnsjon. The 7- ...

Atmospheric pollutant emission factors from open burning of agricultural and forest biomass by wind tunnel simulations. Volume 1. Final report

Abstract: Atmospheric pollutant emission factors were determined by wind tunnel simulations of spreading and pile fires for 8 different types of fuel including barley, rice and wheat straw, corn stover, almond and walnut tree prunings, and Douglas fir and Ponderosa pine slash. Cereal straws and stover were burned in fires spreading against an impressed wind, pile burns in wood fuels were naturally ventilaled through the side doors. Emission factors were determined for each fuel for CO, NO, NOx, SO2, total hydrocarbons, methane, nonmethane hydrocarbons, total sulfur, CO2, particulate matter, volatile organic matter (VOC), and polycyclic aromatic hydrocarbons (PAH). Elemental compositions of particulate matter were determined by size category. Bulk aerosol absorption coefficients were determined from light transmission measurements through filter samples. Emission rates were correlated against burning conditions and fuel compositions. Factor affecting the burning rates and emission factors included inlet air temperature, loading rate, and wind speed.

Diesel NOx reduction by plasma-regenerated absorbend beds

Abstract: Reduction of NOx from diesel engine exhaust by use of plasma-regenerated absorbent beds. This involves a process for the reduction of NOx and particulates from diesel engines by first absorbing NOx onto a solid absorbent bed that simultaneously acts as a physical trap for the particulate matter, and second regenerating said solid absorbent by pulsed plasma decomposition of absorbed NOx followed by air oxidation of trapped particulate matter. The absorbent bed may utilize all metal oxides, but the capacity and the kinetics of absorption and desorption vary between different materials, and thus the composition of the absorbent bed is preferably a material which enables the combination of NOx absorption capability with catalytic activity for oxidation of hydrocarbons. Thus, naturally occurring or synthetically prepared materials may be utilized, particularly those having NOx absorption properties up to temperatures around 400° C. which is in the area of diesel engine exhaust temperatures.