Between 1999 and 2005 a sampling campaign was conducted to identify and quantify the major species of atmospheric nonmethane hydrocarbons (NMHCs) in United States cities. Whole air canister samples were collected in 28 cities and analyzed for methane, carbon monoxide (CO) and NMHCs. Ambient mixing ratios exhibited high inter-and intra-city variability, often having standard deviations in excess of 50% of the mean value. For this reason, ratios of individual NMHC to CO, a combustion tracer, were examined to facilitate comparison between cities. Ratios were taken from correlation plots between the species of interest and CO, and most NMHCs were found to have correlation coefficients (r 2) greater than 0.6, particularly ethene, ethyne and benzene, highlighting the influence of vehicular emissions on NMHC mixing ratios. Notable exceptions were the short-chain alkanes, which generally had poor correlations with CO. Ratios of NMHC vs. CO were also used to identify those cities with unique NMHC sources.

Light alkane hydrocarbons are present in major quantities in the near-surface atmosphere of Texas, Oklahoma, and Kansas during both autumn and spring seasons. In spring 2002, maximum mixing ratios of ethane [34 parts per 10 9 by volume (ppbv)], propane (20 ppbv), and n-butane (13 ppbv) were observed in north-central Texas. The elevated alkane mixing ratios are attributed to emissions from the oil and natural gas industry. Measured alkyl nitrate mixing ratios were comparable to urban smog values, indicating active photochemistry in the presence of nitrogen oxides, and therefore with abundant formation of tropospheric ozone. We estimate that 4 -6 teragrams of methane are released annually within the region and represents a significant fraction of the estimated total U.S. emissions. This result suggests that total U.S. natural gas emissions may have been underestimated. Annual ethane emissions from the study region are estimated to be 0.3-0.5 teragrams.W e have performed two regional studies in different seasons of hydrocarbon and halocarbon mixing ratios in surfacelevel air sampled within the southwestern United States. Elevated atmospheric mixing ratios of C 1 -C 4 alkanes and C 2 -C 4 alkyl nitrates (RONO 2 ) were measured over much of the region during both studies. The alkyl nitrate enhancements show that significant photochemistry analogous to urban smog formation is occurring within the source region. The release of hydrocarbons into the atmosphere contributes to photochemical ozone (O 3 ) production, with related adverse health effects, reduction in plant growth, and climate change (1-3). The production, storage, and transport of oil and natural gas are a major global source of hydrocarbons into the atmosphere (4), and the southwestern states have some of the largest oil and natural gas reserves in the United States. Although the U.S. natural gas industry has been estimated to account for Ϸ20% of the total U.S. anthropogenic methane (CH 4 ) emissions (5), the global budgets of light (C 2 -C 4 ) alkanes, including their emissions from the oil and natural gas industry, are more poorly assessed.The C 2 -C 4 alkanes have globally averaged lifetimes ranging from Ϸ2 months for ethane to several days for the butanes (6). Because of their short lifetimes, the atmospheric concentrations of light alkanes are variable and depend on the number and strength of nearby emission sources. By contrast, CH 4 is by far the most abundant hydrocarbon in the atmosphere, in part because of its 8-year atmospheric lifetime (7), which allows it to be widely distributed throughout both the northern and southern hemispheres. The greater reactivity of C 2 -C 4 alkanes relative to CH 4 ensures that a much larger fraction of the former will react in the area where the emissions occur, making the combined C 2 -C 4 alkane contributions more important for local and regional O 3 formation than the influence of the incremental local increases in CH 4 .In the troposphere, photochemical O 3 production begins with the attack of parent hydrocarbon...

In light of diminishing natural resources, global climatic change and increased environmental sensitivity, renewable-based lubricants are being considered potential alternatives to petroleum-based lubricants. Understanding the tribological performance of vegetable-based lubricants in relation to their chemical composition is essential for their industrial implementation. This study focuses on the friction and abrasion rate characteristics of soybean and sunflower oils in comparison to a base mineral oil under sliding wear at ambient conditions for various applied loads. It was found that the abrasion rate and friction were the least severe for the soybean, followed by the sunflower oil. The observed trends were attributed to differences in their fatty acid compositions, in particular, a lower percentage of linoleic and oleic acids within the soybean oil.

Extractive electrospray ionization mass spectrometry (EESI-MS) has been shown, in other laboratories, to be a useful technique for the analysis of aerosols from a variety of sources. EESI-MS is applied here, for the first time, to the analysis of secondary organic aerosol (SOA) formed from the reaction of ozone and a-pinene. The results are compared to those obtained using atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The SOA was generated in the laboratory and merged with electrospray droplets. The recovered ions were directed towards the inlet of a triple quadrupole mass spectrometer. Through the use of a denuder to remove gas phase compounds, the EESI-MS technique was found to be effective for measuring the major ozonolysis products either in particles alone or in a combination of vapor phase and particulate products. Due to its relatively simple setup and the avoidance of sample collection and work-up, EESI-MS shows promise as an excellent tool for the characterization of atmospherically relevant particles.

[1] An extensive set of carbonyl sulfide (OCS) observations were made as part of the NASA Intercontinental Chemical Transport Experiment-North America (INTEX-NA) study, flown from 1 July to 14 August 2004 mostly over the eastern United States and Canada. These data show that summertime OCS mixing ratios at low altitude were dominated by surface drawdown and were highly correlated with CO 2 . Although local plumes were observed on some low-altitude flight legs, anthropogenic OCS sources were small compared to this sink.

This paper presents a different approach to the data treatment for the electronic absorption spectrum of molecular iodine, a standard experiment in the undergraduate physical chemistry laboratory. Traditionally, students analyze the transitions originating from the υ' ' = 0 level using a Birge-Sponer plot and thereby determine the various molecular constants and energies. Our treatment involves simply fitting the transition frequencies to a second-order polynomial. This fit then yields a direct determination of the important molecular constants along with the various energy terms. With the availability of common graphing programs such as Excel, Kaleidagraph, and SigmaPlot, students can take advantage of more advanced fitting techniques and no longer have to rely on simple linear plots. Additionally, students find this new approach more satisfying and we believe it has pedagogical advantages over the Birge-Sponer treatment.

No abstract

Vegetable oils are potential substitutes for petroleum-based lubricants because they are environmentally friendly, renewable, less toxic and readily biodegradable. The addition of free fatty acids has been shown to increase the lubrication performance of vegetable oils at elevated temperatures. The purpose of this study was to evaluate the relationship between the length of the carbon chain in the fatty acid and its effectiveness as an additive for a range of elevated temperatures. Stearic, arachidic and behenic fatty acid additives were added to commercial sunfl ower oil. All fatty acid additives were shown to be effective in lowering the wear rate and coeffi cient of friction in ball-on-disc tribological tests. The overall carbon chain length was not observed to have a consistent infl uence on the effectiveness of the additive. All additives were less effective at temperatures above 100°C.