Influence of fires on O3 concentrations in the western U.S

Because forest fires emit substantial NOx and hydrocarbons--known contributors to O3 production--we hypothesize that interannual variation in western U.S. O3 is related to the burned area. To evaluate this hypothesis we used a gridded database of western U.S. summer burned area (BA) and biomass consumed (BC) by fires between 101-125 degrees W. The fire data were compared with daytime summer O3 mixing ratios from nine rural Clean Air Status and Trends Network (CASTNET) and National Park Service (NPS) sites. Large fire years exhibited widespread enhanced O3. The summer BA was significantly correlated with O3 at all sites. For each 1 million acres burned in the western U.S. during summer, we estimate that the daytime mean O3 was enhanced across the region by 2.0 ppbv. For mean and maximum fire years, O3 was enhanced by an average of 3.5 and 8.8 ppbv, respectively. At most sites O3 was significantly correlated with fires in the surrounding 5 x 5 degrees and 10 x 10 degrees regions, but not with fires in the nearest 1 x 1 degree region, reflecting the balance between O3 production and destruction in a high NOx environment. BC was a slightly better predictor of O3, compared with BA. The relationship between O3 and temperature was examined at two sites (Yellowstone and Rocky Mountain National Parks). At these two sites, high fire years were significantly warmer than lowfire years; however, daytime seasonal meantemperature and O3 were not significantly correlated. This indicates that the presence of fire is a more important predictor for O3 than is temperature.     

Influence of tropospheric ozone control on exposure to ultraviolet radiation at the surface

Improving air quality by reducing ambient ozone (O(3)) will likely lower O(3) concentrations throughout the troposphere and increase the transmission of solar ultraviolet (UV) radiation to the surface. The changes in surface UV radiation between two control scenarios (nominally 84 and 70 ppb O(3) for summer 2020) in the Eastern two-thirds of the contiguous U.S. are estimated, using tropospheric O(3) profiles calculated with a chemistry-transport model (Community Multi-Scale Air Quality, CMAQ) as inputs to a detailed model of the transfer of solar radiation through the atmosphere (tropospheric ultraviolet-visible, TUV) for clear skies, weighed for the wavelengths known to induce sunburn and skin cancer. Because the incremental emission controls differ according to region, strong spatial variability in O(3) reductions and in corresponding UV radiation increments is seen. The geographically averaged UV increase is 0.11 ± 0.03%, whereas the population-weighted increase is larger, 0.19 ± 0.06%, because O(3) reductions are greater in more densely populated regions. These relative increments in exposure are non-negligible given the already high incidence of UV-related health effects, but are lower by an order of magnitude or more than previous estimates.     

梯度降温对鸭梨采后果肉膜脂过氧化及褐变的影响

以不同成熟度鸭梨为试材,采用每2.5d降1℃,30d降至(0±1)℃的梯度降温方法,探讨梯度降温对鸭梨果肉膜脂过氧化及褐变的影响。结果表明：鸭梨采后果肉褐变指数与丙二醛(MDA)含量、自由基含量呈显著的正相关,与还原性物质含量、保护酶活性呈显著的负相关。梯度降温提高了早采果果肉超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性,一定程度上延缓了VC、还原性谷胱甘肽(GSH)含量的下降,抑制了过氧化氢(H2O2)、超氧阴离子自由基(O2－·)的积累,降低了MDA含量和膜渗透率,从而抑制了鸭梨果肉褐变。与早采鸭梨相比,晚采鸭梨果肉中VC和GSH含量高但下降快,O2－·、H2O2和MDA积累量高,SOD和POD活性较低,梯度降温促进了晚采果果肉的膜脂过氧化和褐变。所以,适时采收结合梯度降温可以很好抑制鸭梨采后果肉褐变。     

Passive ozone network of Dallas: a modeling opportunity with community involvement. 1

Despite tremendous efforts toward regulating and controlling tropospheric ozone (O3) formation, a large portion of the U.S. population presently lives in environments where air quality exceeds both 1- and 8-h National Ambient Air Quality Standards (NAAQS) set for O3. High O3 concentrations annually cost the United States billions of dollars in excessive human health costs, reduced crop yields, and ecological damage. This paper describes a regional networking of O3 monitoring sites, operated by the public, that used simplified passive sampling devices (PSDs). In collaboration with EPA Region 6, a lay network (i.e., Passive Ozone Network of Dallas, acronym POND), consisting of 30 PSD sites in the Dallas-Fort Worth (DFW) Metroplex, a region representing 16 counties, successfully measured daily ozone during 8 weeks of the 1998 high ozone season. It was demonstrated that the concerned public, when properly trained, could successfully operate a large PSD network that requires daily sample handling and weekly mailing procedures, even from remote sites. Data treatment of the 2880 POND measurements included (i) high correlations with collocated continuous monitoring data [r range = 0.95-0.97], (ii) daily O3 contour mapping of the 24,000 km2 area, and (iii) a ranking of O3 severity in 12 peri-urban counties for guidance in sitting additional monitors. With a new 8-h NAAQS standard now in place, a cost-effective network such as POND could aid regional airshed models in generating meaningful guidance for O3 state implementation plans (SIPs) by providing input that is representative of both rural and urban sites.     

Ozone levels in passenger cabins of commercial aircraft on North American and transoceanic routes

Ozone levels in airplane cabins, and factors that influence them, were studied on northern hemisphere commercial passenger flights on domestic U.S., transatlantic, and transpacific routes. Real-time data from 76 flights were collected in 2006--2007 with a battery-powered UV photometric monitor. Sample mean ozone level, peak-hour ozone level, and flight-integrated ozone exposures were highly variable across domestic segments (N = 68), with ranges of < 1.5 to 146 parts per billion by volume (ppbv), 3--275 ppbv, and < 1.5 to 488 ppbv-hour, respectively. On planes equipped with ozone catalysts, the mean peak-hour ozone level (4.7 ppbv, N = 22)was substantially lower than on planes not equipped with catalysts (47 ppbv, N = 46). Peak-hour ozone levels on eight transoceanic flight segments, all on planes equipped with ozone catalysts, were in the range < 1.5 to 58 ppbv. Seasonal variation on domestic routes without converters is reasonably modeled by a sinusoidal curve that predicts peak-hour levels to be approximately 70 ppbv higher in Feb--March than in Aug--Sept The temporal trend is broadly consistent with expectations, given the seasonal cycle in tropopause height. Episodically elevated (>100 ppbv) ozone levels on domestic flights were associated with winter-spring storms that are linked to enhanced exchange between the lower stratosphere and the upper troposphere.     

Measurements of atmospheric carboxylic acids and carbonyl compounds in São Paulo City, Brazil

Winter atmospheric measurements of gaseous lower carbonyl and carboxylic acids were carried out simultaneously (in 1999) at two distinct urban sites located in the city of S?o Paulo, Brazil. The greater metropolitan area of S?o Paulo is the largest industrialized region of Latin America and has a highly polluted atmosphere. It has an unconventional mix of vehicle types in that a variety of gasoline blends, including oxygenated ones, are used. Mixing ratios of formic and acetic acids ranged, respectively, from 0.6 to 19.4 and from 0.1 to 10.6 ppbv in one of the sites studied and from 1.4 to 18.4 and from 0.4 to 6.7 ppbv in the other site. High values of formic to acetic ratios were found, especially in the latter site (average = 4.3), suggesting that photochemical production was the predominant source of the formic and acetic acid during the afternoon. Differing from the acids, levels of carbonyls were similar at both sites. Higher average mixing ratios of acetaldehyde and formaldehyde were found in the morning (18.9 and 17.2 ppbv) and gradually decreased from midday (9.5 and 11.8 ppbv) to evening (7.2 and 10.2 ppbv). In the morning, vehicular direct emission seemed to be the main primary source of formaldehyde and acetaldehyde, whereas at midday and evening these compounds appeared to be mainly formed by photochemistry. Secondary photochemical production of organic acids and aldehydes (rather than primary emissions from vehicles) was shown to be more important in S?o Paulo's atmosphere from midday to evening, particularly on days with strong solar radiation.     

Distribution of volatile organic compounds over a semiconductor Industrial Park in Taiwan

This study examined volatile organic compounds (VOC) concentration in ambient air collected during the years 2000--2003 at several different locations of Hsinchu Science-based Industrial Park (HSIP) in Taiwan. A canister automated GC-MS system analyzed the volatile organics in ambient air grasp samples according to T0-15 method. Oxygenated volatiles were the most abundant VOC detected in HSIP followed by aromatics that are commonly used as solvents in the semiconductor industries. The major components measured in the ambient air are 2-propanol (29-135 ppbv), acetone (12-164 ppbv), benzene (0.7-1.7 ppbv), and toluene (13-20 ppbv). At some of the sampling locations, odorous compounds such as carbon disulfide and dimethyl sulfide levels exceed threshold values. The estimated toluene/benzene ratio is very high at most of the sites. However, the total amount of VOC is reduced over the years from 2000 to 2003 due to strict implementation on use and discharge of solvents in industries. There exists no definite seasonal pattern for sporadic occurrence of high levels of some of the volatile organics. Stagnant weather conditions with low wind speeds aid accumulation of toxic species at ground level. The results entail that hi-tech semiconductor industries are still a potential source for harmful organic substances to surrounding microenvironment.     

The Synergistic Effects of Low-Concentration Acidic Electrolyzed Water and Ultrasound on the Storage Quality of Fresh-Sliced Button Mushrooms

The objective of this study was to determine the effects of low-concentration acidic electrolyzed water (LcEW) combined with ultrasound (US) on fresh-sliced button mushrooms (Agaricus bisporus), by evaluating the enzymatic browning, physio-biochemical changes, and microbial loads. The sliced button mushrooms were divided randomly into three groups (control, LcEW, and LcEW+US) and treated separately with tap water, LcEW, and LcEW+US for 3 min, and afterwards, they were stored at 5 °C for 8 days. The results indicated that LcEW delayed surface browning and maintained the flesh firmness of fresh-cut mushrooms compared with the control, and ultrasound enhanced these effects. Moreover, LcEW+US slowed down the electrolyte leakage (EL) rate and malondialdehyde (MDA) content, which were 5.29% and 0.5227 μmol/fresh weight less than those in control at day 8, respectively. The combined treatment of LcEW and US also significantly inhibited the activities of polyphenol oxidase (PPO) and peroxidase (POD) and controlled the counts of total bacteria (TBC) and yeast and mold counts (Y&M). Meanwhile, LcEW+US maintained a high level of total soluble protein and total phenolic contents, which were 1.49 and 1.24 times higher than those in control at the end of the storage time, respectively, and the combined treatment was more effective than LcEW treatment alone. These results demonstrated that the combination of LcEW and US could be an effective pretreatment technology in maintaining the product quality and prolonging the shelf life of fresh-sliced button mushrooms.     

Formation and Stabilization of Combustion-Generated, Environmentally Persistent Radicals on Ni(II)O Supported on a Silica Surface

Previous studies have indicated environmentally persistent free radicals (EPFRs) are formed when hydroxyl- and chlorine-substituted aromatics chemisorbed on Cu(II)O and Fe(III)(2)O(3) surfaces and were stabilized through their interactions with the surface metal cation. The current study reports our laboratory investigation on the formation and stabilization of EPFRs on a Ni(II)O surface. The EPFRs were produced by the chemisorption of adsorbates on the supported metal oxide surface and transfer of an electron from the adsorbate to the metal center, resulting in reduction of the metal cation. Depending on the temperature and the nature of the adsorbate, more than one type of organic radical was formed. A phenoxyl-type radical, with g-value between 2.0029 and 2.0044, and a semiquinone-type radical, with g-value from 2.0050 to as high as 2.0081, were observed. The half-lives on Ni(II)O were long and ranged from 1.5 to 5.2 days, which were similar to what were observed on Fe(III)(2)O(3). The yields of the EPFRs formed on Ni(II)O were ～8× higher than on Cu(II)O and ～50× higher than on Fe(III)(2)O(3).     

生长调节剂DA-6和DCPTA处理对冬枣果实发育过程中活性氧及其相关生理指标的影响

研究采前己酸二乙氨基乙醇酯(DA-6)和2-(3,4-二氯苯氧基)-乙基-二乙胺(DCPTA)喷施处理对冬枣发育期果实活性氧代谢的影响。试验于盛花期、盛花后20d和40d进行DA-6、DCPTA的喷施树冠处理,并在冬枣果实发育过程中定期取样进行活性氧及其相关生理指标的测定。结果表明：采前DA-6和DCPTA喷施处理后,对O2－ ·的产生速率没有显著影响,仅提前了其低谷的产生;DA-6处理冬枣果实的H2O2含量显著高于DCPTA处理;与对照相比,两处理在整个发育期内显著提高了冬枣果实的SOD和PPO的活性;DCPTA处理显著提高冬枣果实发育末期的CAT活性而DA-6处理显著抑制了冬枣果实的CAT活性,同期DCPTA处理抑制了MDA含量。     

杂粮早餐粉对砷致小鼠雄性生殖毒性的缓解作用

以昆明种纯系雄性小白鼠为受试动物,检测杂粮早餐粉对砷致小鼠雄性生殖毒性的影响。砷染毒组小鼠饮用含砷蒸馏水（砷质量浓度为10 mg/L）,早餐粉干预组小鼠在饮用含砷蒸馏水的同时分别灌胃7.15 g/100 mL和14.30 g/100 mL杂粮早餐粉溶液,每3 d一次。实验周期60 d,期间小鼠自由取水。灌胃结束后检测小鼠睾丸组织的抗氧化指标与组织结构,计算精子总数和精子畸形率。结果表明：通过饮水摄入砷能使小鼠睾丸脏器系数下降,睾丸组织超氧化物歧化酶（superoxide dismutase,SOD）活力和还原型谷胱甘肽（glutathione,GSH）含量下降,H2O2含量升高,丙二醛（malondialdehyde,MDA）含量显著升高（P＜0.05）,睾丸组织结构出现病理性改变,精子总数降低,精子畸形率升高;用杂粮早餐粉干预后,小鼠睾丸脏器系数升高,睾丸组织SOD活力和还原型GSH含量升高,H2O2和MDA含量降低,睾丸组织结构损伤得到缓解,精子总数升高,精子畸形率下降。上述结果表明,所用杂粮早餐粉能降低砷致雄性生殖毒性,对睾丸结构和功能有一定的保护作用,对雄性动物生殖健康具有积极意义。     

Analysis of atmospheric sesquiterpenes: sampling losses and mitigation of ozone interferences

Atmospheric standards containing parts-per-billion levels of 14 semivolatile hydrocarbon compounds, including eight sesquiterpenes (SQTs) (longipinene, alpha-copaene, isolongifolene, alpha-cedrene, trans-caryophyllene, aromadendrene, alpha-humulene, delta-cadinene), two oxidized sesquiterpenoids (cisnerolidol, trans-nerolidol), one biogenic ketone (geranylacetone) and three aromatic compounds (1,3,5-triisopropylbenzene, diphenylmethane, nonylbenzene), were collected onto four solid adsorbent materials at increasing ozone mixing ratios (0-100 ppbv 03) for analysis by thermodesorption-gas chromatography. Substantial sampling losses of up to >90% were found for the most reactive SQT, even at the lowest ozone level investigated of 20 ppbv. Loss rates from the ozone-SQT reaction were used to derive estimates of gas-phase ozone reaction rate constants for longipinene, alpha-copaene, isolongifolene, geranylacetone, aromadendrene, delta-cadinene, cis-nerolidol, and transnerolidol. Three different ozone mitigation techniques were investigated to prevent these sampling losses. These strategies included (a) placing glass fiber filters impregnated with sodium thiosulfate (Na2S2O3) into the sampling line, (b) titration of ozone in the sampling stream with nitric oxide (NO), and (c) catalytically removing ozone with a commercially available manganese dioxide (MnO2) catalyst. All three techniques reduced ozone-mixing ratios from 100 ppbv to <0.6 ppbv at sampling flow rates of 1 L min(-1). When the Na2S2O3 filters and the NO-titration techniques were applied, SQT loss rates decreased from 25-60% to 0-5% for most SQT compounds and from >90% to approximately 10-50% for the two most reactive compounds at ozone mixing ratios of up to 100 ppbv. The commercial manganese dioxide scrubber, however, caused complete analyte losses (>98%) even at 0 ppbv ozone. These results underline the need and present applicable techniques for removal of ozone in air samples for SQT analysis by solid adsorption techniques.     

Semivolatile organochlorine compounds in the free troposphere of the Northeastern Atlantic

Polychlorobiphenyls (PCBs), hexachlorobenzene (HCB), hexachlorocyclohexanes, and DOTs were analyzed over 1 entire year period in the air of a high altitude remote site (2367 m above sea level) located in Teide (Tenerife, Canary Islands, 28 degrees N16 degrees W) in the Eastern North Atlantic region. Twenty samples were collected providing information on the concentrations of these semivolatile organochlorine compounds (SOCs) in the free troposphere since the stable and persistenttemperature inversion in the subtropics defines a clear separation from the marine boundary layer. More than 80% of total SOCs were in the gas phase. HCB was the individual SOC in higher concentration, 51 pg m(-3), well above than the other SOCs identified, 1-11 pg m(-3). Sum PCB concentrations were 78 pg m(-3). These concentrations range among the lowest described in atmospheric samples. The collected air originated from four main sectors, high and middle latitudes in the north Atlantic, Europe, and Africa, as determined from isentropic backward air mass trajectories. No significant differences were observed for the concentrations of these compounds between air masses showing a high uniform SOC composition of the free troposphere. Only the more volatile PCB congeners, #18 and #28, exhibited significant differences between air masses from northern and southern latitudes. A seasonal temperature dependence for the less volatile PCB congeners, five or more chlorine subtituents, was also observed. Free tropospheric concentrations of all SOCs except HCB were lower than those measured near sea level for reference. PCB concentrations at the two altitudes exhibited consistent differences according to degree of chlorination. The stronger decrease of the more volatile compounds with altitude might reflect higher photodegradation.     

Isotopic character of nitrous oxide emitted from streams

Global models have indicated agriculturally impacted rivers and streams may be important sources of the greenhouse gas nitrous oxide (N(2)O). However, there is significant uncertainty in N(2)O budgets. Isotopic characterization can be used to help constrain N(2)O budgets. We present the first published measurements of the isotopic character of N(2)O emitted from low (2-4) order streams. Isotopic character of N(2)O varied seasonally, among streams, and over diel periods. On an annual basis, δ(18)O of emitted N(2)O (+47.4 to +51.4‰; relative to VSMOW) was higher than previously reported for larger rivers, but δ(15)N of emitted N(2)O (-16.2 to +2.4‰ among streams; relative to atmospheric N(2)) was similar to that of past studies. On an annual basis, all streams emitted N(2)O with lower δ(15)N than tropospheric N(2)O. Given these streams have elevated nitrate concentrations which are associated with enhanced N(2)O fluxes, this supports the hypothesis that streams are contributing to the accumulation of (15)N-depleted N(2)O in the troposphere.     

Aircraft measurement of organic aerosols over China

Lower to middle (0.5-3.0 km altitude) tropospheric aerosols (PM2.5) collected by aircraft over inland and east coastal China were, for the first time, characterized for organic molecular compositions to understand anthropogenic, natural, and photochemical contribution to the air quality. n-Alkanes, fatty acids, sugars, polyacids are detected as major compound classes, whereas lignin and resin products, sterols, polycyclic aromatic hydrocarbons, and phthalic acids are minor species. Average concentrations of all the identified compounds excluding malic acid correspond to 40-50% of those reported on the ground sites. Relative abundances of secondary organic aerosol (SOA) components such as malic acid are much higher in the aircraft samples, suggesting an enhanced photochemical production over China. Organic carbon (OC) concentrations in summer (average, 24.3 microg m(-3)) were equivalent to those reported on the ground sites. Higher OC/EC (elemental carbon) ratios in the summer aircraft samples also support a significant production of SOA over China. High loadings of organic aerosols in the Chinese troposphere may be responsible to an intercontinental transport of the pollutants and potential impact on the regional and global climate changes.     

Attachment of Shiga toxigenic Escherichia coli to stainless steel

Shiga toxigenic Escherichia coli (STEC) are important foodborne pathogens causing gastrointestinal disease worldwide. Bacterial attachment to food surfaces, such as stainless steel may lead to cross contamination of foods and subsequent foodborne disease. A variety of STEC isolates, including E. coli O157:H7/H- strains, were grown in planktonic (broth) and sessile (agar) culture, following which initial attachment to stainless steel was determined using epifluorescence microscopy. Experiments were performed to determine whether the number of bacteria attached to stainless steel differed between STEC strains and between the two modes of growth. No relationship was found between STEC strains and the number of bacteria attached to stainless steel. Five STEC strains, including one non-toxigenic O157 isolate, attached in significantly greater (p<0.05) numbers to stainless steel following growth in planktonic culture compared to sessile culture. In contrast, two clinical strains of O157:H7 attached in significantly greater (p<0.05) numbers following growth in sessile culture compared to planktonic culture. Thirteen out of twenty E. coli strains showed no significant difference (p>0.05) in attachment when grown in planktonic or sessile culture. The change of interfacial free energy between the bacterial strains and stainless steel was calculated and the influence of free energy in attachment was determined. Although a significant variation (p<0.05) in free energy values was found between STEC strains, no correlation was found between free energy values and bacterial counts on stainless steel. In addition, no correlation was also found between bacterial hydrophobicity and surface charge values or production of surface structures (type I fimbriae or flagella) (previously determined) with the number of bacteria attached to stainless steel. The results of this study suggest that different growth conditions (planktonic and sessile) can influence the attachment of STEC to stainless steel. Factors other than bacterial physicochemical properties and these surface structures may also influence STEC attachment to stainless steel.     

Polyfluorinated telomer alcohols and sulfonamides in the North American troposphere

In 2001, a sampling campaign was conducted in six North American cities--Reno, NV; Griffin, GA; Cleves, OH; Winnipeg, MB; Long Point, ON; and Toronto, ON--to investigate the tropospheric distribution of a suite of polyfluorinated alcohols and amides. Analysis via gas chromatography-chemical ionization-mass spectrometry indicated that both polyfluorinated sulfonamides and fluorinated telomer alcohols (FTOHs) are widely distributed throughout the North American troposphere with mean concentrations ranging from 22 to 403 pg/m3 and from 11 to 165 pg/m3 respectively. The dominant polyfluorinated contaminant was dependent on sampling location. Large mean concentrations of N-methyl perfluorooctane sulfonamidoethanol (359 pg/m3) and N-ethyl perfluorooctane sulfonamidoethanol (199 pg/m3) identified in Griffin and Reno, respectively, may indicate the release of polyfluorinated sulfonamides to the environment through paper and carpet treatment processes. The nonuniform nature of the spatial distribution of both polyfluorinated sulfonamides and FTOHs is indicative of the importance of point sources for the dissemination of these contaminants in the North American troposphere.     

Evidence for a free troposphere source of mercury in wet deposition in the Western United States

Mercury (Hg) in wet deposition in the United States is measured as part of the National Atmospheric Deposition Program--Hg Deposition Network (MDN). This study focused on compiling and assessing data collected since 2003 at two sites in Nevada, and at one in Nevada and three in Idaho where data were collected over shorter time intervals. At all locations the highest volume weighted concentrations and deposition were observed in the summer, a time of low precipitation, but high gaseous oxidized Hg (GOM) concentrations. Detailed assessment of high Hg wet deposition events showed variability across the region and higher deposition at the higher elevation sites. Potential Source Contribution Function analyses showed no specific point sources associated with the high Hg wet deposition events, but air masses derived predominantly from the southwest. Although this region has potential local and regional sources of GOM, detailed back trajectory analyses, the environmental setting of Nevada, results from other studies in Nevada, and GEOS-Chem modeling results point toward a free troposphere contribution to mercury in wet deposition input to this area of the western United States.     

渍水胁迫对油菜根系形态与生理活性的影响

盆栽条件下研究连续渍水胁迫对2个甘蓝型油菜品种中双9号和中油杂12号苗期根系形态及生理活性的影响。结果表明,渍水处理初期（前5d）两个油菜品种根系超氧自由基阴离子（O2.-）产生速率均较对照显著提高,超氧化物歧化酶（SOD）活性较对照显著升高,活性氧累积引起的细胞膜脂过氧化程度（MDA含量）变化不显著,根系生物量及形态参数未发生显著变化。但随着渍水时间延长至5d后,根系O2.-产生速率继续加快而SOD和过氧化氢酶（CAT）活性显著降低,细胞膜脂过氧化程度（MDA含量）显著提高;根系组织坏死严重,根生物量显著降低;根系形态发生显著变化,根表面积、根体积、主根长和总根长显著降低,平均根直径显著增加,须根数量明显减少。