Determination of fine particulate semi-volatile organic material at three eastern U.S. sampling sites.

Correct assessment of fine particulate carbonaceous material as a function of particle size is, in part, dependent on the determination of semi-volatile compounds, which can be lost from particles during sampling. This study gives results obtained for the collection of fine particulate carbonaceous material at three eastern U.S. sampling sites [Philadelphia, PA; Shenandoah National Park, VA; and Research Triangle Park (RTP), NC] using diffusion denuder technology. The diffusion denuder samplers allow for the determination of fine particulate organic material with no artifacts, due to the loss of semi-volatile organic particulate compounds, or collection of gas-phase organic compounds by the quartz filter during sampling. The results show that an average of 41, 43, and 59% of fine particulate organic material was lost as volatilized semi-volatile organic material during collection of particles on a filter at Philadelphia, RTP, and Shenandoah, respectively. The particle size distribution of carbonaceous material retained by a filter and lost from a filter during sampling was obtained for the samples collected at Philadelphia and Shenandoah. The carbonaceous material retained by the particles during sampling was found predominantly in particles smaller than 0.4 microm in aerodynamic diameter. In contrast, the semi-volatile organic material lost from the particles during sampling had a mass median diameter of approximately 0.5 microm.

Acute exposure to environmental tobacco smoke and heart rate variability.

Environmental tobacco smoke (ETS) has been associated with cardiovascular mortality. Pathophysiologic pathways leading from ETS exposure to cardiopulmonary disease are still being explored. Reduced cardiac autonomic function, as measured by heart rate variability (HRV), has been associated with cardiac vulnerability and may represent an important pathophysiologic mechanism linking ETS and risk of cardiac mortality. In this study we evaluated acute ETS exposure in a commercial airport with changes in HRV in 16 adult nonsmokers. We conducted ambulatory electrocardiographic (ECG) monitoring for 8-hr periods while participants alternated 2 hr in nonsmoking and smoking areas. Nicotine and respirable suspended particle concentrations and participants' blood oxygen saturation were also monitored. We calculated time and frequency domain measures of HRV for periods in and out of the smoking area, and we evaluated associations with ETS using comparative statistics and regression modeling. ETS exposure was negatively associated with all measures of HRV. During exposure periods, we observed an average decrement of approximately 12% in the standard deviation of all normal-to-normal heart beat intervals (an estimate of overall HRV). ETS exposures were not associated with mean heart rate or blood oxygen saturation. Altered cardiac autonomic function, assessed by decrements in HRV, is associated with acute exposure to ETS and may be part of the pathophysiologic mechanisms linking ETS exposure and increased cardiac vulnerability.

Potential particulate impacts at the Grand Canyon from northwestern Mexico.

Project MOHAVE was a major air quality and visibility research program conducted from 1990 to 1999 to investigate the causes of visibility impairment in the Grand Canyon National Park region. At Meadview, a remote monitoring site just west of the Grand Canyon National Park, on September 1 and 2, 1992, the concentrations of sulfate (3.1 and 4.3 microg sulfate/m3) were the highest seen in 6 years of monitoring at this site. During this period, the concentrations of SO2 at Meadview were also abnormally high and approximately three times the sulfate concentrations, on a nmol/m3 basis. High concentrations of sulfate and SO2 extended south into southern Arizona and northwestern Mexico. Based on ambient atmospheric conditions, emissions from the Mohave Power Project (MPP) 110 km upwind of Meadview could not have been responsible for the majority of the regionally observed sulfur oxides. The geographical distribution of SO2 and sulfate, and available source information suggest that northwestern Mexico was a significant source of the unusually high observed sulfur oxides. A CMB model developed during Project MOHAVE was used to apportion sulfur oxides at Meadview and other sampling sites throughout the study region for August 31-September 2, 1992. The results indicate that the contribution of MPP to sulfate at Meadview was typical. However, the transport of SOx from northwestern Mexico was elevated throughout much of the region during this time period. This led to the large increase in sulfate concentrations at Meadview on September 1 and 2. These results indicate that emissions from Mexico can be a significant source of particulate material in the Grand Canyon.

Semi-volatile species in PM2.5: comparison of integrated and continuous samplers for PM2.5 research or monitoring.

Fine particles in urban atmospheres contain substantial quantities of semi-volatile material [e.g., NH4NO3 and semi-volatile organic compounds (SVOCs)] that are lost from particles during collection on a filter. Several diffusion denuder samplers have been developed for the determination of both NO3- and organic semi-volatile fine particulate components. The combination of technology used in the BOSS diffusion denuder sampler and the Harvard particle concentrator has resulted in the Particle Concentrator-Brigham Young University Organic Sampling System (PC-BOSS) for the 24-hr (or less) integrated collection of PM2.5, including NH4NO3 and semi-volatile organic material. Modification of the BOSS sampler allows for the weekly determination of these same species. Combination of BOSS denuder and tapered element oscillating microbalance (TEOM) monitor technology has resulted in the real-time ambient mass sampler (RAMS) for the continuous measurement of PM2.5, including the semi-volatile components. Comparison of the results obtained with the BOSS and with each of the newly developed modifications of the BOSS indicates that the modified versions can be used for the continuous, daily, or weekly monitoring of PM2.5, including semi-volatile species, as appropriate to the design of each sampler.

Second generation chemical mass balance source apportionment of sulfur oxides and sulfate at the Grand Canyon during the Project MOHAVE summer intensive.

Receptor-based chemical mass balance (CMB) analysis techniques are designed to apportion species that are conserved during pollutant transport using conserved source profiles. The techniques will fail if non-conservative species (or profiles) are not properly accounted for in the CMB model. The straightforward application of the CMB model developed for Project MOHAVE using regional profiles resulted in a significant under-prediction of total sulfate oxides (SOx, SO2 plus fine particulate sulfate) for many samples at Meadview, AZ. In addition, for these samples the concentration of the inert tracer emitted from the MOHAVE Power Project (MPP), ocPDCH, was also under-predicted. A second-generation model has been developed which assumes that separation of particles and SO2 can occur in the MPP plume during nighttime stable plume conditions. This second-generation CMB model accounts for all SOx present at the various receptor sites. In addition, the concentrations of ocPDCH and the presence of other inert tracers of emission from regional sources are accurately predicted. The major source of SOx at Meadview was the MPP, but the major source of sulfate at this site was the Las Vegas urban area. At Hopi Point in the Grand Canyon, the Baja California region (Imperial Valley and northwestern Mexico) was the major source of both SOx and sulfate.

Indoor/outdoor relationships for ambient PM2.5 and associated pollutants: epidemiological implications in Lindon, Utah.

Outdoor and indoor fine particulate species were measured at the Lindon Elementary School in Lindon, Utah, to determine which components of ambient fine particles have strong indoor and outdoor concentration correlations. PM2.5 mass concentrations were measured using tapered element oscillating microbalance (TEOM) monitors and by gravimetric analysis of Teflon filter samples. Gas-phase HNO3, sulfur dioxide, particulate nitrate, strong acid, and particulate sulfate were measured using annular denuder samplers. Soot was measured using quartz filters in filter packs. Total particulate number was measured with a condensation nucleus counter (CNC). Total particulate number and fine particulate sulfate and soot were correlated for ambient and indoor measurements. Indoor PM2.5 mass showed a low correlation with outdoor PM2.5 mass because of the influence of coarse material from student activities on indoor PM2.5. Fine particle acidity and the potentiation of biological oxidative mechanisms by iron were not correlated indoors and outdoors.

The determination of nicotine and cotinine by ion pair reversed-phase chromatography.

An ion chromatographic method is described for the determination of nicotine and cotinine in aqueous solutions. This method is based on a type of reversed-phase chromatography involving ion pair formation of protonated nicotine, cotinine, pyridine, and pyridine derivatives. Detection is accomplished by measuring the UV absorption at 262 nm. Detection limits for nicotine and cotinine are 8 ng/mL and 2 ng/mL, respectively. Analyses of environmental samples and spiked environmental samples by both this ion chromatographic method and a previously reported gas chromatographic method have been used to demonstrate the accuracy and precision of this technique. The results of the analyses of both sets of samples by the two methods are in excellent agreement with a linear correlation coefficient of 0.97.

Kinetics of drug decomposition by heat conduction calorimetry.

The application of heat conduction calorimetry to the determination of decomposition mechanisms and rates for drugs is shown to be a rapid and generally useful method. The application of the method to determine the nature of the decomposition reaction, sources of systematic errors in the method, the equations relating the calorimetric signal to the kinetics of the reaction, and some examples of results are presented and discussed.

Binding of the Triton X series of nonionic surfactants to bovine serum albumin.

The binding of a series of Triton X nonionic surfactants (NIS) tobivine serum albumin (BSA) has been studied by equilibrium dialysis and titration calorimetry. At pH 7.0, Triton X molecules bind to two classes of sites, the first 2 molecules binding with positive cooperativity to high-affinity sites following by the binding of approximately 15 additional molecules to lower affinity, thermodynamically identical, and independent sites. The strength of the binding decreases as the number of oxyethylene units is increased in the surfactants Triton X-114, X-100, X-102, and X-165. Calorimetric measurements show the enthalpy change for the NIS-BSA interaction to be small and endothermic. Increasing the hydrophilic oxyethylene chain length results in a more endothermic enthalpy change and a smaller association constant. Electron spin resonance studies of Triton X binding to BSA, covalently spin-labeled with N-(2,2,6,6-tetramethyl-piperidinyl-1-oxy)maleimide, indicated that the protein conformation in the vicinity of the labeled sulfhydryl was insensitive to NIS binding from dilute monomeric solutions. Calorimetric experiments near the critical micelle concentration indicate, however, that the protein probably undergoes a conformational change associated with the population of the lower affinity NIS binding sites.

S(IV) chemistry in smelter produced particulate matter.

Epidemiological and animals toxicological studies have indicated that reactions between SO2(g) and metal containing aerosols result in the formation of respiratory irritants. It had initially been suggested by EPA that sulfate per se was responsible for the observed health effects. That now appears unlikely. These studies point out the importance of understanding in detail the chemical species formed by such interactions. In the present paper procedures which have been used to study the formation of aerosol inorganic S(IV) species are described, together with the results obtained from studies in the flue line, workroom, and plume of smelters. Both atmospheric and laboratory studies indicate that very stable complexes of S(IV) with Fe(III) or Cu(?) can form in aerosols. The data suggest that the concentration of these (S(IV) complexes in primary particulate emissions from smelters will be about 10% of the sulfate concentration. In plumes the concentration of inorganic S(IV) varied from 10 to 80% of the sulfate concentration. The most important variable controlling the formation of these S(IV) complexes in a plume aerosol droplet is the aerosol acidity. The formation of aerosol inorganic S(IV) complexes in the plume is not related to the formation of sulfate. There have been no studies previously reported that would allow an unequivocal evaluation of the toxicological implications of the chemistry reviewed in this paper. If these various S(IV) species are responsible at the low concentrations reported here for the "synergistic" effects previously reported between SO2(g) and aerosols, then additional toxicological work would appear warranted.

Dimethyl and monomethyl sulfate: presence in coal fly ash and airborne particulate matter.

Dimethyl sulfate and its hydrolysis product monomethyl sulfate have been found at concentrations as high as 830 parts per million in fly ash and in airborne particulate matter from coal combustion processes. This discovery poses a new environmental problem because of the mutagenic and carcinogenic properties of these compounds.

The binding isotherms for the interaction of 5-doxyl stearic acid with bovine and human albumin.

Binding isotherms for the interaction of 5-doxyl stearic acid with bovine and human albumin are reported. The critical micelle concentration (CMC) and the limiting solubility of 5-doxyl stearic acid were determined using the electron spin resonance (ESR)-spin label method. The CMC and the limiting solubility of this spin-label stearic acid in saline-phosphate buffer are 3.5 x 10(-5) M and 2 x 10(-4) M, respectively. We found no ESR line width evidence for pre-association of the spin-label stearate below the CMC. Maximum binding of the spin-label stearate to both bovine and human albumin occurs before micelle formation. The binding isotherm for spin-label stearic acid interaction with bovine albumin is in agreement with data obtained by others using [1-(14)C]stearic acid. For human albumin, comparison is difficult since previous data obtained with [1-(14)C]stearic acid vary widely. Comparison of the ESR 2T(||) values (the splitting between low and high field extremes, a measure of the degree of immobilization of protein-bound spin-label stearate) for bovine and human albumin indicates a greater immobilization of the spin-label molecules bound to human albumin. The binding data indicate that complexes are formed with bound spin-label stearate/albumin ratios of at least 18. The computed equilibrium constants for both bovine and human albumin indicate that the first seven spin-label molecules are tightly bound, log K > 5.0. The species predicted to form in solution by these equilibrium constants are reported.