Thomas M. Cahill

Secondary organic aerosols formed from oxidation of biogenic volatile organic compounds in the Sierra Nevada Mountains of California

Received 7 February 2006; revised 14 April 2006; accepted 17 May 2006; published 25 August 2006. [1] Biogenic volatile organic compound (BVOC) emissions, such as isoprene and terpenes, can be oxidized to form less volatile carbonyls, acids, and multifunctional oxygenated products that may condense to form secondary organic aerosols (SOA). This research was designed to assess the contribution of oxidized BVOC emissions to SOA in coniferous forests by collecting high-volume particulate samples for 6 days and 5 nights in the summer of 2003. The samples were analyzed for acids, carbonyls, polyols and alkanes to quantify oxidized BVOCs. Terpene and isoprene oxidation products were among the most abundant chemical species detected with the exception of hexadecanoic acid, octadecanoic acid and two butyl esters of unknown origin. The terpene oxidation products of pinonic acid, pinic acid, nopinone and pinonaldehyde showed clear diurnal cycles with concentrations two- to eight-fold higher at night. These cycles resulted from the diurnal cycles in gaseous terpene concentrations and lower temperatures that enhanced condensation of semivolatile chemicals onto aerosols. The terpene-derived compounds averaged 157 ± 118 ng/m 3 of particulate organic matter while the isoprene oxidation compounds, namely the 2-methyltetrols and 2-methylglyceric acid, accounted for 53 ± 19 ng/m 3 . Together, the terpene and isoprene oxidation products represented 36.9% of the identified organic mass of 490 ± 95 ng/m 3 .P M10 organic matter loadings in the region were approximately 2.1 ± 1.2 mg/m 3 , so about 23% of the organic matter was identified and at least 8.6% was oxidized BVOCs. The BVOC oxidation products we measured were significant, but not dominant, contributors to the regional SOA only 75 km downwind of the Sacramento urban area.

Very Fine and Ultrafine Metals and Ischemic Heart Disease in the California Central Valley 1: 2003–2007

The enhancement of mortality associated with cardiovascular and specifically ischemic heart disease (IHD) has been observed in the southern California Central Valley since at least 1990, and it continues to be a major source of mortality. While there is a strong statistical association of IHD with wintertime PM2.5 mass, the causal agents are uncertain. Medical studies identify some potential causal agents, such as very fine and ultrafine metals, but they have not been fully characterized in most Central Valley regions. To provide improved information on specific and potentially causal agents, a five site aerosol sampling transect was conducted from Redding to Bakersfield during a 17-day period of strong stagnation, January 5–22, 2009. Mass and elemental components were measured every 3 h in eight particle size modes, ranging from 10 to 0.09 μm, while the ultrafine particles (<0.09 μm) were collected on Teflon filters. Ancillary studies were performed including direct upwind–downwind profiles across a heavily traveled secondary street near a stoplight. Very fine and ultrafine iron, nickel, copper, and zinc were identified as vehicular, with the most probable sources being brake drums and pads and the lubrication oil additive zinc thiophosphate. High correlations, many with r 2 > 0.9, were found between these vehicular metals and IHD mortality, enhanced by the meteorology, terrain, and traffic patterns of the southern Central Valley. The braking systems of cars and trucks must now be considered along with direct exhaust emissions in estimating the health impacts from traffic.

MERCURY RESIDUES AND PRODUCTIVITY IN OSPREY AND GREBES FROM A MINE-DOMINATED ECOSYSTEM

Mercury (Hg) and reproduction and status of Western and Clarks Grebes (Aechmophorus sp.) and Osprey (Pandion haliaetus) were studied from 1992 through 2001 and then less intensely through 2006 at Clear Lake, California, USA. Remediation to reduce Hg loading from the Sulphur Bank Mercury Mine was initiated in 1992. Mercury in grebe feathers declined monotonically from approximately 23 mg/kg dry mass (DM) in 1967-1969 to 1 mg/kg in 2003, but then increased to 7 mg/kg in 2004-2006. Mercury in Osprey feathers varied similarly, with mean values of 20 mg/kg DM in 1992, declining to a low of 2 mg/kg in 1998, but increasing to 23 mg/kg in 2003, and 12 mg/kg in 2006. Mercury in Osprey feathers at our reference site (Eagle Lake, California) remained low (1-8 ppm) throughout the entire period, 1992-2003. Grebe productivity at Clear Lake improved from approximately 0.1 to 0.5 fledged young per adult during the latter part of the study when human disturbance was prevented. At that period in time, improved productivity did not differ from our reference site at Eagle Lake. Human disturbance, however, as a co-factor made it impossible to evaluate statistically subtle Hg effects on grebe productivity at Clear Lake. Osprey reproduced sufficiently to maintain increasing breeding numbers from 1992 to 2006. Mercury in Clear Lake water, sediments, invertebrates, and fish did not decline from 1992 to 2003, but a shift in trophic structure induced by an introduced planktivorous fish species may have caused significant alterations in Hg concentrations in several species of prey fishes that may have produced concomitant changes in Osprey and grebe Hg exposure. The temporary declines observed in grebe and Osprey feather residues in the late 1990s, with coincidental improvements in reproductive performance, however, could not be attributed to remediation at the mine site.

Inorganic and organic aerosols downwind of California's Roseville Railyard

Inorganic and organic constituents of aerosols from a major railyard and repair facility were characterized to develop a profile of emissions from railyard activities. The railyard has very consistent downslope winds blowing laterally across the railyard for about 8 hours each night, so two sampling stations were used, one just upwind of the railyard and one downwind adjacent to the railyard fence line. Aerosol samples were collected by rotating drum impactors (DRUM and Lundgren) in up to 9 size modes for 5 weeks in summer and fall of 2005 in tandem with the Roseville Railyard Aerosol Monitoring Project (RRAMP), which measured, black carbon (BC) PM2, as well as NO and NO2. The DRUM aerosol samples were analyzed for mass, optical absorption, and elemental content in 3 h time resolution to allow separation of day and night. Organic analysis was conducted on another set of time integrated size-segregated samples taken by a Lundgren impactor during nighttime hours. The ratio between the downwind versus upwind sites at night was as high as 21.9 (NO, RRAMP) and 6.4 (optical absorption, DRUM) but many species had ratios greater than 2, demonstrating which aerosols arose from railyard activities. The main emissions from the railyard consisted of very fine (0.26 > D p > 0.09 μm) and ultrafine (<0.1 μm) aerosols associated with diesel exhaust such as mass, organic matter, transition metals, and sulfur, the latter 3.3% of the mass since locomotive diesel fuel still contained sulfur. There were also coarse soil aerosols contaminated with anthropogenic metals and petroleum-derived n-alkanes. The aerosol PAH (polycyclic aromatic hydrocarbons) profile showed higher proportions of the heavier PAHs, such as benzo[a]pyrene, compared to diesel truck exhaust on a per unit mass. These aerosols were mostly in the ultrafine (<0.1 μm) size mode, enhancing lung capture. These results and those of Roseville Railyard Aerosol Monitoring Project (RRAMP) largely confirm earlier California Air Resources Boards (ARB) model estimates of health impacts downwind of the railyard based on diesel exhaust, while adding data on very fine transition metals and contaminated soils, potentially important to human health.

A high-resolution model for estimating the environmental fate of multi-species chemicals: application to malathion and pentachlorophenol

A high-resolution multi-species (HR-MS) model is presented that assesses the fate of up to four inter-converting chemical species. The current model has a more detailed environmental description than previous multi-species models in order to give a more accurate description of environmental fate. Improvements to the model environment include stratified air, soil and sediment compartments, the inclusion of a vegetation compartment, and the separation of the aerosol phase from the gas phase of the atmosphere. Such detailed environmental descriptions are particularly valuable when chemical heterogeneity is expected within environmental media as occurs with more reactive chemicals or local-scale simulations. The HR-MS model is illustratively applied to two situations for which a detailed environmental description is needed to describe the chemical fate accurately. The first example is the estimation of the atmospheric concentrations of malathion and its degradation product malaoxon following a local-scale application. The second example is a regional simulation of pentachlorophenol, which benefits from the more detailed treatment of ionizing chemical in the atmosphere. In both these cases, the HR-MS model is shown to be in good agreement with observed field data and provides a more accurate description of environmental fate than simpler multi-species models.

Emissions of acrolein and other aldehydes from biodiesel-fueled heavy-duty vehicles.

Aldehyde emissions were measured from two heavy-duty trucks, namely 2000 and 2008 model year vehicles meeting different EPA emission standards. The tests were conducted on a chassis dynamometer and emissions were collected from a constant volume dilution tunnel. For the 2000 model year vehicle, four different fuels were tested, namely California ultralow sulfur diesel (CARB ULSD), soy biodiesel, animal biodiesel, and renewable diesel. All of the fuels were tested with simulated city and high speed cruise drive cycles. For the 2008 vehicle, only soy biodiesel and CARB ULSD fuels were tested. The research objective was to compare aldehyde emission rates between (1) the test fuels, (2) the drive cycles, and (3) the engine technologies. The results showed that soy biodiesel had the highest acrolein emission rates while the renewable diesel showed the lowest. The drive cycle also affected emission rates with the cruise drive cycle having lower emissions than the urban drive cycle. Lastly, the newer vehicle with the diesel particulate filter had greatly reduced carbonyl emissions compared to the other vehicles, thus demonstrating that the engine technology had a greater influence on emission rates than the fuels.

Extraction and Analysis of Trifluoroacetic Acid in Environmental Waters

Trifluoroacetic acid (TFA), a mildly phytotoxic compound, is a stable atmospheric breakdown product of HFC-134a, HCFC-123, and HCFC-124. An extraction and analytical method has been developed for the routine analysis of low ppt levels of TFA in aqueous samples. TFA can be quantitatively recovered from most environmental waters by an extraction procedure using a commercial anion-exchange disk. In saline samples (conductivity >620 μS), where the presence of competing anions interfered with recovery, a liquid-liquid extraction cleanup was necessary. After extraction of TFA from water, the dried disk was placed in a headspace vial containing 10% sulfuric acid in methanol and the vial sealed and then vortexed for 30 s. The sulfuric acid-methanol solution extracts trifluoroacetate anion (TFA) from the anion-exchange matrix and, when heated, quantitatively converts it to the methyl ester, which is then analyzed by automated headspace gas chromatography using electron capture or mass spectrometry detection. Several environmental samples in addition to laboratory spike solutions were successfully extracted and analyzed with this technique. Recoveries averaged 108.2% for reagent water spiked at levels from 53 to 2110 ng/L with relative standard deviations ranging from 0.3 to 8.4%. The instruments limit of detection for TFA standard was 3.3 ng. The limit of quantitation for the extraction and analytical technique was 36 ng/L. Three water samples can be prepared for automated analysis in 20 min using this technique.

Ambient Acrolein Concentrations in Coastal, Remote, and Urban Regions in California

Acrolein (2-propenal) is a reactive chemical that is very toxic and has many sources. Acrolein is commonly detected in the atmosphere, but understanding the ambient concentrations of this compound has been hampered by analytical difficulties. The objective of this research was to utilize an analytical method specifically designed for acrolein to determine acrolein concentrations in remote regions. The purpose was to determine the natural background concentrations of acrolein which were simply lacking in the literature. In addition, rural and urban areas were sampled to determine the degree of anthropogenic enrichment in polluted environments. The results from the coastal and remote inland areas suggest that the median natural summertime background of acrolein was near 40 ng/m(3), which was higher than the Environmental Protection Agencys Reference Concentration (RfC) of 20 ng/m(3). Acrolein concentrations in urban areas were approximately 3- to 8-fold higher than background concentrations, which was a lower degree of urban enrichment than expected. The results suggest that additional research is needed to understand the natural background concentrations of acrolein.

Size-resolved organic speciation of wintertime aerosols in California's Central Valley.

Size-resolved aerosol samples, including the entire ultrafine fraction, were simultaneously collected along a transect in Californias Central Valley during the winter of 2009. The samples were analyzed for PAHs, alkanes, organic acids, and sugars. The results showed that the organic constituents of aerosols did not follow the same pattern as PM(10), thus indicating that simple PM measurements are not good indicators of trace toxic organic chemicals. Levoglucosan, a tracer of wood smoke, was the most abundant organic chemical detected, thus demonstrating the predominance of wood smoke in the valley. The size profile of levoglucosan showed a maximum in the 0.34-0.56 microm size mode, which is larger than published emission profiles. This suggests that wood smoke aerosols increased in size as they aged in the environment. Some chemicals, such as benzo[a]pyrene, had similar aerosol size profiles as levoglucosan and likely arose from the same source. Other chemicals, such as coronene and sugars, had very different size profiles, indicating that they have different sources. One unexpected result was the relatively large fraction of certain chemicals present in the ultrafine fraction, which highlights the importance of collecting the entire ultrafine fraction.

Variability in capsaicinoid content and Scoville heat ratings of commercially grown Jalapeño, Habanero and Bhut Jolokia peppers

The variability of capsaicinoid content of three common, commercially-available hot pepper varieties, namely Jalapeño, Habanero and Bhut Jolokia, was investigated. For each variety tested, ten peppers were acquired from each of ten different suppliers resulting in 100 peppers per variety that were individually analyzed. The results showed that different pepper varieties had different distribution types. The Habanero peppers showed a normal distribution; the Bhut Jolokia showed a skewed distribution and the Jalapeño peppers showed a very skewed distribution. The source of variability was also different; the Habaneros were very consistent within a given pepper supplier so most of the overall variation resulted from differences between suppliers. The Jalapeño peppers were the exact opposite with a very high degree of variability within a given supplier and relatively low variation between suppliers. A bootstrap statistical simulation was conducted on the data to suggest a minimum number of peppers to analyze to characterize the variation in a population. The simulations indicated that small sample sizes are effective at estimating the mean concentrations, but a sample size of ten or more is necessary to describe the population and capture the high-end tail of the distributions, which are the very hottest peppers.