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A negative-ion proton-transfer chemical ionization mass spectrometer was deployed on a mobile tower-mounted platform during Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT) to measure nitrous acid (HONO) in the winter of 2011. High resolution vertical profiles revealed (i) HONO gradients in nocturnal boundary layers, (ii) ground surface dominates HONO production by heterogeneous uptake of NO2, (iii) significant quantities of HONO may be deposited to the ground surface at night, (iv) daytime gradients indicative of ground HONO production or emission, and (v) an estimated surface HONO reservoir comparable or larger than integrated daytime HONO surface production. Nocturnal integrated column observations of HONO and NO2 allowed direct evaluation of nocturnal ground surface uptake coefficients for these species (γNO2, surf = 2 × 10 -6 to 1.6 × 10-5 and γHONO, surf = 2 × 10-5 to 2 × 10-4). A chemical model showed that the unknown source of HONO was highest in the morning, 4 × 10 6 molecules cm-3 s-1 (600 pptv h-1), declined throughout the day, and minimized near 1 × 106 molecules cm-3 s-1 (165 pptv h-1). The quantity of surface-deposited HONO was also modeled, showing that HONO deposited to the surface at night was at least 25%, and likely in excess of 100%, of the calculated unknown daytime HONO source. These results suggest that if nocturnally deposited HONO forms a conservative surface reservoir, which can be released the following day, a significant fraction of the daytime HONO source can be explained for the NACHTT observations. Key Points HONO vertical gradients form on nights with stable nocturnal boundary layersNocturnal HONO production consistent with ground surface area dominanceSurface deposition of HONO may be a reservoir for the unknown daytime source ©2013. American Geophysical Union. All Rights Reserved.

The Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT) field experiment took place during late winter, 2011, at a site 33 km north of Denver, Colorado. The study included fixed-height measurements of aerosols, soluble trace gases, and volatile organic compounds near surface level, as well as vertically resolved measurements of nitrogen oxides, aerosol composition, soluble gas-phase acids, and halogen species from 3 to 270 m above ground level. There were 1928 individual profiles during the three-week campaign to characterize trace gas and aerosol distributions in the lower levels of the boundary layer. Nitrate and ammonium dominated the ionic composition of aerosols and originated primarily from local or regional sources. Sulfate and organic matter were also significant and were associated primarily with longer-range transport to the region. Aerosol chloride was associated primarily with supermicron size fractions and was always present in excess of gas-phase chlorine compounds. The nighttime radical reservoirs, nitryl chloride, ClNO2, and nitrous acid, HONO, were both consistently present in nighttime urban air. Nitryl chloride was especially pronounced in plumes from large point sources sampled aloft at night. Nitrous acid was typically most concentrated near the ground surface and was the dominant contributor (80%) to diurnally averaged primary OH radical production in near-surface air. Large observed mixing ratios of light alkanes, both in near-surface air and aloft, were attributable to local emissions from oil and gas activities.

Viral gastroenteritis outbreaks are associated with illness and death when they occur in institutional settings, notably in long-term care facilities (LTCFs) for the elderly (1). Although most reported outbreaks in [...]

Neurocysticercosis (NCC) is a parasitic disease caused by central nervous system infection with Taenia solium larval cysts. It is the most common helminthic infection of the central nervous system and [...]

Internet-based questionnaires are increasingly used during investigations of outbreaks; however, compared with telephone interviews, a differential response rate on the basis of exposures or outcomes might bias results (1-6). On [...]

Sporadic infections following ear piercing are well documented, but common source outbreaks are rarely recognized. Investigation by Oregon public health agencies in August-September 2000, confirmed that cases had pseudomonas aeruginosa cultured from ear wounds.

Based on in vitro data, the U.S. Food and Drug Administration recommends chemical disinfection of raw sprout seeds to reduce enteric pathogens contaminating the seed coats. However, little is known [...]

Water in lakes and other places people swim may be contaminated with the Escherichia (E.) coli and Shigella (S.) sunnei bacteria, leading to infection of swimmers. In 1991, a larger-than-expected number of cases of bloody diarrhea, shigellosis and hemolytic-uremic disorder (a kidney disease) were reported in the Portland, OR, area. Twenty-one cases were reported to have an E. coli infection and 38 were infected with S. sonnei. Most the victims were children. The lake in Blue Lake Park was found to be contaminated with these organisms, probably from fecal matter produced by swimmers. From this episode, it appears these bacteria can survive some time in lake water. The concentration of the organisms does not need to be high for people to become ill from swallowing some of the water.

One goal of any outbreak investigation is to identify the causative pathogen (1). In a recent analysis of foodborne disease outbreaks in the United States during 2006, only 49% had [...]

A newly-developed method for measuring inorganic chlorine gases in the marine boundary layer was presented. The technique involves the removal of coarse and fine aerosol and the use of a trace gas concentrator in an acidic mist chamber. Ion chromatography was used to analyze mist solutions. The detection limits of the technique were estimated to be approximately 39 pptv for HCl and 13 pptv for Cl2.

In 1995, an outbreak of Escherichia coli O157:H7 infection was traced to beef jerky made from deer meat. An investigation by the Oregon health department uncovered 6 confirmed and 5 presumed cases of the infection. Nine cases occurred in an extended family of three households. The remaining two had been visitors. All but one had eaten jerky made from a deer killed a week before the outbreak. The bacterium was found in samples of deer meat and in deer fecal pellets recovered from the nearby forest., Objective.--To investigate a 1995 outbreak of Escherichia coli O157:H7 infections and to assess the safety of meat dehydration methods. Design.--Survey subsequent to routine surveillance report, environmental investigations, and laboratory experimentation. Setting.--Oregon community. Participants.--Members of an extended household and their social contacts with confirmed or presumptive E coli O157:H7 infections. Results.--A total of 6 confirmed and 5 presumptive cases were identified. Homemade venison jerky was implicated as the source of transmission. E coli O157:H7 with the same distinctive, pulsed-field gel electrophoresis pattern seen in the case isolates was recovered from leftover jerky, uncooked meat from the same deer, a saw used to dismember the carcass, and fragments of the deer hide. In a subsequent survey, E coli O157:H7 was recovered from 3 (9%) of 32 deer fecal pellets collected in nearby forest land. In the laboratory, inoculated venison was dried at several time and temperature combinations, ranging up to 10 hours at 62.8 degrees C. Viable organisms were recovered under all conditions tested. Conclusions.--Deer can be colonized by E coli O157:H7 and can be a source of human infections. Conditions necessary to ensure the safety of dried meat deserve further review. Game should be handled with the same caution indicated for commercially Slaughtered meat. JAMA. 1997;277:1229-1231