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431.
432.
Misra C Geller MD Shah P Sioutas C Solomon PA 《Journal of the Air & Waste Management Association (1995)》2001,51(9):1309-1317
In this paper, we describe the development and laboratory and field evaluation of a continuous coarse (2.5-10 microm) particle mass (PM) monitor that can provide reliable measurements of the coarse mass (CM) concentrations in time intervals as short as 5-10 min. The operating principle of the monitor is based on enriching CM concentrations by a factor of approximately 25 by means of a 2.5-microm cut point round nozzle virtual impactor while maintaining fine mass (FM)--that is, the mass of PM2.5 at ambient concentrations. The aerosol mixture is subsequently drawn through a standard tapered element oscillating microbalance (TEOM), the response of which is dominated by the contributions of the CM, due to concentration enrichment. Findings from the field study ascertain that a TEOM coupled with a PM10 inlet followed by a 2.5-microm cut point round nozzle virtual impactor can be used successfully for continuous CM concentration measurements. The average concentration-enriched CM concentrations measured by the TEOM were 26-27 times higher than those measured by the time-integrated PM10 samplers [the micro-orifice uniform deposit impactor (MOUDI) and the Partisol] and were highly correlated. CM concentrations measured by the concentration-enriched TEOM were independent of the ambient FM-to-CM concentration ratio, due to the decrease in ambient coarse particle mass median diameter with an increasing FM-to-CM concentration ratio. Finally, our results illustrate one of the main problems associated with the use of real impactors to sample particles at relative humidity (RH) values less than 40%. While PM10 concentrations obtained by means of the MOUDI and Partisol were in excellent agreement, CM concentrations measured by the MOUDI were low by 20%, and FM concentrations were high by a factor of 5, together suggesting particle bounce at low RH. 相似文献
433.
L T Chang H H Suh J M Wolfson K Misra G A Allen P J Catalano P Koutrakis 《Journal of the Air & Waste Management Association (1995)》2001,51(10):1414-1422
While researchers have linked acute (less than 12-hr) ambient O3, PM2.5, and CO concentrations to a variety of adverse health effects, few studies have characterized short-term exposures to these air pollutants, in part due to the lack of sensitive, accurate, and precise sampling technologies. In this paper, we present results from the laboratory and field evaluation of several new (or modified) samplers used in the "roll-around" system (RAS), which was developed to measure 1-hr O3, PM2.5, and CO exposures simultaneously. All the field evaluation data were collected during two sampling seasons: the summer of 1998 and the winter of 1999. To measure 1-hr O3 exposures, a new active O3 sampler was developed that uses two nitrite-coated filters to measure O3 concentrations. Laboratory chamber tests found that the active O3 sampler performed extremely well, with a collection efficiency of 0.96 that did not vary with temperature or relative humidity (RH). In field collocation comparisons with a reference UV photometric monitor, the active O3 sampler had an effective collection efficiency ranging between 0.92 and 0.96 and a precision for 1-hr measurements ranging between 4 and 6 parts per billion (ppb). The limits of detection (LOD) of this method were 9 ppb-hr for the chamber tests and approximtely 16 ppb-hr for the field comparison tests. PM2.5 and CO concentrations were measured using modified continuous monitors--the DustTrak and the Langan, respectively. A size-selective inlet and a Nafion dryer were placed upstream of the DustTrak inlet to remove particles with aerodynamic diameters greater than 2.5 microm and to dry particles prior to the measurements, respectively. During the field validation tests, the DustTrak consistently reported higher PM2.5 concentrations than those obtained by the collocated 12-hr PM2.5 PEM samples, by approximately a factor of 2. After the DustTrak response was corrected (correction factor of 2.07 in the summer and 2.02 in the winter), measurements obtained using these methods agreed well with R2 values of 0.87 in the summer and 0.81 in the winter. The results showed that the DustTrak can be used along with integrated measurements to measure the temporal and spatial variation in PM2.5 exposures. Finally, during the field validation tests, CO concentrations measured using the Langan were strongly correlated with those obtained using the reference method when the CO levels were above the LOD of the instrument [approximately 1 part per million (ppm)]. 相似文献
434.
A digestive tract mass balance was performed on six men with high body burdens of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Intake via food was measured by analyzing duplicate portions of the food consumed by the volunteers and excretion via feces was determined by quantitative collection and analysis of the feces. Blood samples were taken to determine the current body burden. The results showed that the quantity of non-metabolized chemical excreted in the feces clearly exceeded the uptake via food for all of the 2,3,7,8-substituted PCDDs and some of the PCDFs, indicating a significant clearance across the gastrointestinal tract. The concentrations of these PCDD/F congeners in blood and feces were highly correlated (r > 0.8), demonstrating that the fecal PCDD/F content was determined by the body burden. The half lives in the test persons due to fecal clearance of non-metabolized chemical were estimated from the excretion rate and the current body burden and ranged between 10 years (Cl8DD) and 33 years (2,3,4,7,8-Cl5DF). These were compared with the overall contaminant half-lives due to all clearance processes which were calculated from the body burden and the decrease in blood concentrations measured over several years. The fecal clearance of non-metabolized PCDD/F contributed on average between 37% (2,3,7,8-Cl4DD) and 90% (Cl8DD) to the total elimination. This indicates that the gastrointestinal pathway plays a decisive role in the clearance of most 2,3,7,8-subsituted PCDD/F congeners. 相似文献
435.
436.
Fritz Nü?lein Ernst Anton Feicht Sigurd Schulte-Hostede und Antonius Kettrup 《Umweltwissenschaften und Schadstoff-Forschung》1997,9(3):136-142
Zusammenfassung Ein quecksilberkontaminierter Altstandort dient als Beispiel für eine umweltmedizinische Beurteilung der Belastung der im
Umfeld wohnenden Personen durch Quecksilberimmissionen. Dabei wird die innere Exposition für sieben verschiedene Altersgruppen
bezüglich der KontaktmedienBoden, Luft undNahrungsmittel anhand von konventionell festgelegten Szenarien abgesch?tzt und ein Vergleich mit den epidemiologischen Ergebnissen eines
Humanmonitorings angestrebt. Die standortspezifisch und pfadspezifisch durchgeführte Expositionsabsch?tzung stützt sich auf
cine Vielzahl von unterschiedlichen Probenehmern sowie auf über mehrere Jahre durchgeführte Konzentrationsmessungen in den
aufnahmerelevanten Kompartimenten. Sowohl die Berechnungen als auch die epidemiologischen Untersuchungen zeigen eine leichte
Erh?hung der Quecksilberexposition, gemessen an strengen Richtwerten.
相似文献
437.
438.
Gerrit Schüürmann Gerd Sch?dlich Ralph Kühne 《Umweltwissenschaften und Schadstoff-Forschung》1994,6(1):3-4
Die Cadmium-Belastung im Ackerboden der Region Leipzig-Halle wurde an 63 terrestrischen Standorten über einer Fl?che von etwa
7 000 km2 bestimmt. Die Verteilung der durch Normierung auf einheitlichen Gehalt an Ton und organischem Material erhaltenen effektiven
Expositionswerte wurde mit Literaturangaben über NOEC-Werte verglichen. Die Risikoanalyse ergibt, da? an 9% der untersuchten
Standorte eine potentielle Gef?hrdung der Bodenorganismen durch Cadmium vorliegt.
Cadmium contamination in the agricultural soil of the region Leipzig-Halle was determined at 63 sites covering an area of
ca. 7 000 km2. Normalization according to lutum and organic matter lead to effective exposure values; their distribution was compared with
NOEC data taken from literature. The risk analysis reveals that the soil fauna is potentially affected by cadmium contamination
at 9% of the investigated sites. 相似文献
439.
Orrù R Cincotti A Concas A Cao G 《Environmental science and pollution research international》2003,10(6):385-389
The possibility of exploiting self-propagating reactions for environmental protection is discussed in this paper. In particular, results obtained at the laboratory scale and related to the fixation and consolidation of high level radioactive wastes, the recycling of silicon sludge and aluminum dross produced by semiconductor industries and aluminum foundries, the treating and recycling of a highly toxic solid waste from electrolytic zinc plants, and the degradation of chlorinated aromatics, are examined with particular emphasis on the latter case. Specifically, the self-propagating destruction of hexachlorobenzene and 2-(2-4-dichlorophenoxy)-propanoic acid with calcium hydride as reductive substrate is demonstrated. In fact, the heat liberated by the reactions involved is large enough to guarantee the self-sustaining character of the process within a wide range of reactants compositions. Moreover, no residual chlorinated organic compounds were found in the final solid product. Some reactor engineering aspects, as well as other significant future scientific and technological issues, are also addressed in view of large-scale applicability of processes based on self-propagating reactions. To date, the batch reactor technology seems to be more easily applicable, although the use of continuous reactors is not excluded in the next future. 相似文献
440.