Enhanced ozone over western North America from biomass burning in Eurasia during April 2008 as seen in surface and profile observations

During April 2008, as part of the International Polar Year (IPY), a number of ground-based and aircraft campaigns were carried out in the North American Arctic region (e.g., ARCTAS, ARCPAC). The widespread presence during this period of biomass burning effluent, both gaseous and particulate, has been reported. Unusually high ozone readings for this time of year were recorded at surface ozone monitoring sites from northern Alaska to northern California. At Barrow, Alaska, the northernmost point in the United States, the highest April ozone readings recorded at the surface (hourly average values >55 ppbv) in 37 years of observation were measured on April 19, 2008. At Denali National Park in central Alaska, an hourly average of 79 ppbv was recorded during an 8-h period in which the average was over 75 ppbv, exceeding the ozone ambient air quality standard threshold value in the U.S. Elevated ozone (>60 ppbv) persisted almost continuously from April 19–23 at the monitoring site during this event. At a coastal site in northern California (Trinidad Head), hourly ozone readings were >50 ppbv almost continuously for a 35-h period from April 18–20. At several sites in northern California, located to the east of Trinidad Head, numerous occurrences of ozone readings exceeding 60 ppbv were recorded during April 2008. Ozone profiles from an extensive series of balloon soundings showed lower tropospheric features at ～1–6 km with enhanced ozone during the times of elevated ozone amounts at surface sites in western Canada and the U.S. Based on extensive trajectory calculations, biomass burning in regions of southern Russia was identified as the likely source of the observed ozone enhancements. Ancillary measurements of atmospheric constituents and optical properties (aerosol optical thickness) supported the presence of a burning plume at several locations. At two coastal sites (Trinidad Head and Vancouver Island), profiles of a large suite of gases were measured from airborne flask samples taken during probable encounters with burning plumes. These profiles aided in characterizing the vertical thickness of the plumes, as well as confirming that the plumes reaching the west coast of North America were associated with biomass burning events.     

Seasonal trends,meteorological impacts,and associated health risks with atmospheric concentrations of gaseous pollutants at an Indian coastal city

This study presents surface ozone (O₃) and carbon monoxide (CO) measurements conducted at Bhubaneswar from December 2010 to November 2012 and attempts for the very first time a health risk assessment of the atmospheric trace gases. Seasonal variation in average 24 h O₃ and CO shows a distinct winter (December to February) maxima of 38.98?±?9.32 and 604.51?±?145.91 ppbv, respectively. O₃ and CO characteristics and their distribution were studied in the form of seasonal/diurnal variations, air flow patterns, inversion conditions, and meteorological parameters. The observed winter high is likely due to higher regional emissions, the presence of a shallower boundary layer, and long-range transport of pollutants from the Indo-Gangetic Plain (IGP). Large differences between daytime and nighttime O₃ values during winter compared to other seasons suggest that photochemistry is much more active on this site during winter. O₃ and CO observations are classified in continental and marine air masses, and continental influence is estimated to increase O₃ and CO by up to 20 and 120 ppbv, respectively. Correlation studies between O₃ and CO in various seasons indicated the role of CO as one of the O₃ precursors. Health risk estimates predict 48 cases of total premature mortality in adults due to ambient tropospheric O₃ during the study period. Comparatively low CO concentrations at the site do not lead to any health effects even during winter. This study highlights the possible health risks associated with O₃ and CO pollution in Bhubaneswar, but these results are derived from point measurements and should be complemented either with regional scale observations or chemical transport models for use in design of mitigation policies.     

Flow patterns influencing the seasonal behavior of surface ozone and carbon monoxide at a coastal site near Hong Kong

Surface O₃ and CO were measured at Cape D’Aguilar, Hong Kong during the period of January 1994 to December1996 in order to understand the temporal variations of surface O₃ and CO in East Asia–West Pacific region. The isentropic backward trajectories were used to isolate different air masses reaching the site and to analyze the long-range transport and photochemical buildup of O₃ on a regional scale. The results show that the diurnal variation of surface O₃ was significant in all seasons with daily O₃ production being about 20 ppbv in fall and 10 ppbv in winter, indicating more active photochemical processes in the subtropical region. The distinct seasonal cycles of O₃ and CO were found with a summer minimum (16 ppbv)–fall maximum (41 ppbv) for O₃ and a summer minimum (116 ppbv)–winter maximum (489 ppbv) for CO. The isentropic backward trajectory cluster analyses suggest that the air masses (associated with regional characteristics) to the site can be categorized into five groups, which are governed by the movement of synoptic weather systems under the influence of the Asian monsoon. For marine-originated air masses (M-SW, M-SE and M-E, standing for marine-southwest, marine-southeast and marine-east, respectively) which always appear in summer and spring, the surface O₃ and CO have relatively lower mixing ratios (18, 16 and 30 ppbv for O₃, 127, 134 and 213 ppbv for CO), while the continental air masses (C-E and C-N, standing for continent-east and continent-north, respectively) usually arrive at the site in winter and fall seasons with higher O₃ (43 and 48 ppbv) and CO (286 and 329 ppbv). The 43 ppbv O₃ and 286 ppbv CO are representative of the regionally polluted continental outflow air mass due to the anthropogenic activity in East Asia, while 17 ppbv O₃ and 131 ppbv CO can be considered as the signature of the approximately clean marine background of South China Sea. The very high CO values (461–508 ppbv) during winter indicate that the long-range transport of air pollutants from China continent is important at the monitoring site. The fall maximum (35–46 ppbv) of surface O₃ was believed to be caused by the effects of the weak slowly moving high-pressure systems which underlie favorable photochemical production conditions and the long-range transport of aged air masses with higher O₃ and its precursors.     

Factors controlling the diurnal variation of CO above a forested area in southeast Europe

Carbon monoxide (CO) measurements have been performed in a forested site in central Greece in the framework of the AEROBIC (AEROsol formation from Biogenic Carbon) campaign in summer 1997. The mean CO observed during the whole campaign ranged between 114 and 250 ppbv (mean of 170±27 ppbv), reflecting continental influence. The observed mean diurnal cycle of CO presented a minimum in the early morning due to the efficient deposition of CO in a shallow nocturnal layer sealed from the free tropospheric air during the night (loss rates of about 2 ppbv h⁻¹). In the early morning and in the late afternoon, a sharp and fluctuating increase of CO was observed as the consequence of CO primary sources, likely by local traffic as suggested by the concomitant enhancements of black carbon (BC) and other combustion tracers. The morning pollution peak (6:30–8:30 local time) preceded slightly the opening of the nocturnal layer to the free troposphere, which resulted in CO reduction down to background levels at about 10:00. During the day (10:00–17:00), a slight but regular increase was observed on CO levels. For lack of simultaneous increase of other anthropogenic tracers, this CO enhancement has been attributed to its photochemical formation initiated by the oxidation of reactive biogenic hydrocarbons. This observed net production of CO averaging 1.2 ppbv h⁻¹ is quite well reproduced by a box model containing an explicit chemical scheme of isoprene and α- and β-pinene and taking into account the measured mixing ratios and the reactivity of all biogenic organic reactive compounds when uncertainties in measurements and modelling are considered.     

Atmospheric alcohols and aldehydes concentrations measured in Osaka,Japan and in Sao Paulo,Brazil

The use of alcohol fuel has received much attention since 1980s. In Brazil, ethanol-fueled vehicles have been currently used on a large scale. This paper reports the atmospheric methanol, ethanol and isopropanol concentrations which were measured from May to December 1997, in Osaka, Japan, where alcohol fuel was not used, and from 3 to 9 February 1998, in Sao Paulo, Brazil, where ethanol fuel was used. The alcohols were determined by the alkyl nitrite formation reaction using gas chromatography (GC-ECD) analysis. The concentration of atmospheric alcohols, especially ethanol, measured in Sao Paulo were significantly higher than those in Osaka. In Osaka, the average concentrations of atmospheric methanol, ethanol, and isopropanol were 5.8±3.8, 8.2±4.6, and 7.2±5.9 ppbv, respectively. The average ambient levels of methanol, ethanol, and isopropanol measured in Sao Paulo were 34.1±9.2, 176.3.±38.1, and 44.2±13.7 ppbv, respectively. The ambient levels of aldehydes, which were expected to be high due to the use of alcohol fuel, were also measured at these sampling sites. The atmospheric formaldehyde average concentration measured in Osaka was 1.9±0.9 ppbv, and the average acetaldehyde concentration was 1.5±0.8 ppbv. The atmospheric formaldehyde and acetaldehyde average concentrations measured in Sao Paulo were 5.0±2.8 and 5.4±2.8 ppbv, respectively. The C₂H₅OH/CH₃OH and CH₃CHO/HCHO were compared between the two measurement sites and elsewhere in the world, which have already been reported in the literature. Due to the use of ethanol-fueled vehicles, these ratios, especially C₂H₅OH/CH₃OH, are much higher in Brazil than these measured elsewhere in the world.     

Atmospheric peroxides over the North Pacific during IOC 2002 shipboard experiment

Atmospheric hydrogen peroxide and methyl hydroperoxide were determined onboard the Melville over the North Pacific from Osaka to Honolulu during May-June 2002. The concentrations of H(2)O(2) and CH(3)OOH increased from 0.64+/-0.57 ppbv and 0.27+/-0.59 ppbv in subpolar region (30-50 degrees N) to 1.96+/-0.95 ppbv and 1.56+/-1.3 ppbv in subtropical region (24-30 degrees N). The increase in concentrations towards the Equator was more pronounced for CH(3)OOH than H(2)O(2). In contrast, the levels of O(3) and CO were decreased at lower latitudes as air mass was more aged, denoted by the ratios of C(2)H(2)/CO and C(3)H(8)/C(2)H(6). CH(3)OOH concentrations showed a clear diurnal variation with a maximum around noon and minimum before sunrise. Frequently, the concentrations of peroxides remained over 1 ppbv in the dark and even gradually increased after sunset. In addition, the ratios of C(2)H(4)/C(2)H(6) and C(3)H(6)/C(3)H(8) were increased in aged subtropical air, which implies that these alkenes were emitted from the ocean surface. As a result, the reaction of these biogenic alkenes with O(3) was suggested to be a potential source for peroxides in aged marine air at lower latitudes.     

Continuous measurement of peroxyacetyl nitrate (PAN) in suburban and remote areas of western China

Knowledge on atmospheric abundance of peroxyacetyl nitrate (PAN) is important in assessing the severity of photochemical pollution, and for understanding chemical transformation of reactive odd nitrogen and its impact on the budget of tropospheric ozone (O₃). In summer 2006, continuous measurements of PAN were made using an automatic GC–ECD analyzer with an on-line calibrator at a suburban site of Lanzhou (LZ) and a remote site of Mt. Waliguan (WLG) in western China, with concurrent measurements of O₃, total reactive nitrogen (NO_y) and carbon monoxide (CO). At LZ, several photochemical episodes were observed during the study, and the average mixing ratio of PAN (plus or minus standard deviation) was 0.76 (±0.89) ppbv with the maximum value of 9.13 ppbv, compared to an average value of 0.44 (±0.16) ppbv at remote WLG. The PAN mixing ratios in LZ exhibited strong diurnal variations with a maximum at noon, while enhanced concentrations of PAN were observed in the evening and a minimum in the afternoon at WLG. The daily O₃ and PAN concentration maxima showed a strong correlation (r² = 0.91) in LZ, with a regression slope (PAN/O₃) of 0.091 ppbv ppbv^?1. At WLG, six well-identified pollution plumes (lasting 2–8 h) were observed with elevated concentrations of PAN (and other trace gases), and analysis of backward particle release simulation shows that the high-PAN events at WLG were mostly associated with the transport of air masses that had passed over LZ.     

Seasonal ozone behavior along an elevation gradient in the Colorado Front Range Mountains

Ambient surface ozone was monitored for one year at a series of seven sites along an elevation gradient from 1600 m to 3500 m above sea level (ASL) in Boulder County, Colorado. Spatial variability of ozone, quantified as the root mean squared deviation of hourly ozone per kilometer horizontal separation, decreased with elevation and distance from local sources, validating the assumption that (except at the City of Boulder (BO) site) the results of the study are representative of the Colorado Front Range. The northern hemisphere (NH) tropospheric spring ozone peak was clearly apparent in late April and early May and affected ozone at all elevations. Ozone consistently increased with elevation during winter, with a mean monthly rate of 1.5 ppbv per 100 m elevation. In summer, this monotonic increase in ozone with elevation was not observed; instead mean monthly ozone increased in two steps, by ～15 ppbv between 1610 m and 1940 m ASL and by ～10 ppbv between 3350 m and 3530 m ASL to a maximum of 60 ppbv. The amplitude of the diurnal ozone cycle decreased with increasing elevation. Average summertime diurnal swings in ozone concentration had a magnitude of 29 ppbv at 1610 m ASL, and 7–16 ppbv at the mid-elevation sites. In winter a diurnal cycle was observed only at the BO site, ozone concentrations at the remaining six locations changed on a multi-day timescale, indicating regional background behavior as the primary factor for wintertime ozone. Even the highest elevation site was influenced by transported urban air pollution in summer, indicated by the average 5 ppbv diurnal increase in ozone. Ozone exposure at the mid- to high-elevation sites in many instances approached and exceeded the 8-h National Ambient Air Quality Standard of 75 ppbv. The elevated ozone levels along this transect were interpreted to be caused by the confounding effects of the high elevation of these sites, increased ozone in long-range transported air, and anthropogenic ozone production in air transported from the nearby urban and suburban areas east of the Colorado Front Range Mountains.     

Vehicle emissions of radical precursors and related species observed in the 2009 SHARP campaign

The 2009 Study of Houston Atmospheric Radical Precursors (SHARP) field campaign had several components that yielded information on the primary vehicular emissions of formaldehyde (HCHO) and nitrous acid (HONO), in addition to many other species. Analysis of HONO measurements at the Moody Tower site in Houston, TX, yielded emission ratios of HONO to the vehicle exhaust tracer species NO_x and CO of 14 pptv/ppbv and 2.3 pptv/ppbv, somewhat smaller than recently published results from the Galleria site, although evidence is presented that the Moody Tower values should be upper limits to the true ratios of directly emitted HONO, and are consistent with ratios used in current standard emissions models. Several other Moody Tower emission ratios are presented, in particular a value for HCHO/CO of 2.4 pptv/ppbv. Considering only estimates of random errors, this would be significantly lower than a previous value, though the small sample size and possible systematic differences should be taken into account. Emission factors for CO, NO_x, and HCHO, as well as various volatile organic compounds (VOCs), were derived from mobile laboratory measurements both in the Washburn Tunnel and in on-road exhaust plume observations. These two sets of results and others reported in the literature all agree well, and are substantially larger than the CO, NO_x, and HCHO emission factors derived from the emission ratios reported from the Galleria site.

Implications: Emission factors for the species measured in the various components of the 2009 SHARP campaign in Houston, TX, including HCHO, HONO, CO, CO₂, nitrogen oxides, and VOCs, are needed to support regional air quality monitoring. Components of the SHARP campaign measured these species in several different ways, each with their own potential for systematic errors and differences in vehicle fleets sampled. Comparisons between data sets suggest that differences in sampling place and time may result in quite different emission factors, while also showing that different vehicle mixes can yield surprisingly similar emission factors.     

Chemical climatology of high elevation spruce-fir forests in the southern Appalachian mountains

The physical and chemical climatology of high elevation (> 1500 m) spruce-fir forests in the southern Appalachian mountains was studied by establishing a weather and atmospheric chemical observatory at Mt Mitchell State Park in North Carolina (35 degrees 44' 05" N, 82 degrees 17' 15"W). Data collected during the summer and autumn (May-October) of 1986, 1987, and 1988 are reported. All measurements were made on or near a 16.5 m walk-up tower extending 10 m above the forest canopy on Mt Gibbes (2006 m msl), which is located approximately 2 km SW of Mt Mitchell. The tower was equipped with standard meteorological instrumentation, a passive cloud water collector, and gas pollutant sensors for O3, SO2, NOx. The tower and nearby forest canopy were immersed in clouds 25 to 40% of the time. Non-precipitating clouds were very acidic (pH 2.5-4.5). Precipitating clouds were less acidic (pH 3.5-5.5). The dominant wind directions were WNW and ESE. Clouds from the most common wind direction (WNW) were more acidic (mean pH 3.5) than those from the next most common wind direction (ESE, mean pH 5.5). Cloud water acidity was related to the concentration of SO4(2-), and NO3- ions. Mean concentration of H+, NH4+, SO4(2-), and NO3- ions in the cloud water varied from 330-340, 150-200, 190-200 and 120-140 micromol litre(-1) respectively. The average and range of O3 were 50 (25-100) ppbv (109) in 1986, 51 (26-102) ppbv in 1987, and 66 (30-140) during the 1988 field seasons, respectively. The daily maximum, 1-h average, and 24-h average concentrations were all greatest during June through mid-August, suggesting a correlation with the seasonal temperature and solar intensity. Throughfall collectors near the tower were used to obtain a useful estimate of deposition to the forest canopy. Between 50-60% of the total deposition of SO4(2-) was due to cloud impact.     

Variability of tropospheric hydroperoxides at a coastal surface site in Antarctica

The annual cycles of hydrogen peroxide (H₂O₂) and methylhydroperoxide (MHP) have been investigated at a remote site in Antarctica in order to study seasonal variations as well as chemical processes in the troposphere. The measurements have been performed from March 1997 to January 1998 and in February 1999 at the German Antarctic research station Neumayer which is located at 70°39′S, 8°15′W. The obtained time series for hydrogen peroxide and methylhydroperoxide in near-surface air represents the first all-year measurements in Antarctica and indicates clearly the occurrence of seasonal variations. During polar night mean values of 0.054±0.046 ppbv (range<0.03–0.11 ppbv) for hydrogen peroxide and 0.089±0.052 ppbv (range<0.05–0.14 ppbv) for methylhydroperoxide were detected. At the sunlit period higher Mixing ratios were found, 0.20±0.13 ppbv (range<0.03–0.91 ppbv) for hydrogen peroxide and 0.19±0.10 ppbv (range<0.05–0.89 ppbv) for methylhydroperoxide. Occasional long-range transport of air masses from mid-latitudes caused enhanced peroxide concentrations at polar night. During the period of stratospheric ozone depletion we observed peroxide mixing ratios comparable to typical winter levels.     

South Philadelphia passive sampler and sensor study

From June 2013 to March 2015, in total 41 passive sampler deployments of 2 wk duration each were conducted at 17 sites in South Philadelphia, PA, with results for benzene discussed here. Complementary time-resolved measurements with lower cost prototype fenceline sensors and an open-path ultraviolet differential optical absorption spectrometer were also conducted. Minimum passive sampler benzene concentrations for each sampling period ranged from 0.08 ppbv to 0.65 ppbv, with a mean of 0.25 ppbv, and were negatively correlated with ambient temperature (–0.01 ppbv/°C, R² = 0.68). Co-deployed duplicate passive sampler pairs (N = 609) demonstrated good precision with an average and maximum percent difference of 1.5% and 34%, respectively. A group of passive samplers located within 50 m of a refinery fenceline had a study mean benzene concentration of 1.22 ppbv, whereas a group of samplers located in communities >1 km distant from facilities had a mean of 0.29 ppbv. The difference in the means of these groups was statistically significant at the 95% confidence level (p < 0.001). A decreasing gradient in benzene concentrations moving away from the facilities was observed, as was a significant period-to-period variation. The highest recorded 2-wk average benzene concentration for the fenceline group was 3.11 ppbv. During this period, time-resolved data from the prototype sensors and the open-path spectrometer detected a benzene signal from the west on one day in particular, with the highest 5-min path-averaged benzene concentration measured at 24 ppbv.

Implications: Using a variation of EPA’s passive sampler refinery fenceline monitoring method, coupled with time-resolved measurements, a multiyear study in South Philadelphia informed benzene concentrations near facilities and in communities. The combination of measurement strategies can assist facilities in identification and mitigation of emissions from fugitive sources and improve information on air quality complex air sheds.     

Factors contributing to seasonal variations in wet deposition fluxes of trace elements at sites along Japan Sea coast

In this study, we measured the wet deposition fluxes of ten trace elements (As, Cd, Cr, Cu, Mn, Ni, Pb, Sb, V and Zn) from December 2002 to March 2006 at three sites along the Japan Sea coast, which have been strongly affected by the long-range transport of air pollutants from the Asian continent. Also, factors, contributing to their seasonal variations were investigated. At the northern and central sites, the monthly wet deposition fluxes of all or most trace elements greatly increased during the cold season (typically, November–April), along with their monthly average (volume-weighted) concentrations in the precipitation. The cold/warm season ratios for the average concentrations of trace elements in precipitation were within the range of 2.7–5.1 at the northern site and 1.8–5.9 at the central site, which were similar to the average scavenging ratios (= concentration in precipitation/concentration in air) at each site. However, there were small differences (0.47–1.2 at the northern site and 0.73–1.7 at the central site) in the ratios of average concentrations in air between the two seasons. These suggest that the increase in the wet deposition fluxes of trace elements during the cold season is due to increases in their scavenging ratios. On the other hand, the result for the southern site was different from those at the other sites. The number of days when the daily maximum wind speed exceeded 10 m s^?1 at the meteorological observatories near the study sites increased markedly during the cold season at the northern and central sites, showing that strong winds usually blow during the cold season at those sites, but not at the southern site. Higher wind speed transports larger amounts of constituents into the cloud system, which can result in their increased concentrations in precipitation. Thus, high scavenging ratios of trace elements during the cold season may be caused by the increase in their amounts of discharge into the cloud system owing to high wind speed, suggesting that wind speed is an important factor in the seasonal variations in the wet deposition fluxes.     

Spatial distribution of tropospheric ozone in western Washington, USA

We quantified the distribution of tropospheric ozone in topographically complex western Washington state, USA (total area approximately 6000 km(2)), using passive ozone samplers along nine river drainages to measure ozone exposure from near sea level to high-elevation mountain sites. Weekly average ozone concentrations were higher with increasing distance from the urban core and at higher elevations, increasing a mean of 1.3 ppbv per 100 m elevation gain for all mountain transects. Weekly average ozone concentrations were generally highest in Cascade Mountains drainages east and southeast of Seattle (maximum=55-67 pbv) and in the Columbia River Gorge east of Portland (maximum=59 ppbv), and lowest in the western Olympic Peninsula (maximum=34 ppbv). Higher ozone concentrations in the Cascade Mountains and Columbia River locations downwind of large cities indicate that significant quantities of ozone and ozone precursors are being transported eastward toward rural wildland areas by prevailing westerly winds. In addition, temporal (week to week) variation in ozone distribution is synchronous within and between all drainages sampled, which indicates that there is regional coherence in air pollution detectable with weekly averages. These data provide insight on large-scale spatial variation of ozone distribution in western Washington, and will help regulatory agencies optimize future monitoring networks and identify locations where human health and natural resources could be at risk.     

Mixing ratios of volatile organic compounds (VOCs) in the atmosphere of Karachi,Pakistan

Mixing ratios of carbon monoxide (CO), methane (CH₄), non-methane hydrocarbons, halocarbons and alkyl nitrates (a total of 72 species) were determined for 78 whole air samples collected during the winter of 1998–1999 in Karachi, Pakistan. This is the first time that volatile organic compound (VOC) levels in Karachi have been extensively characterized. The overall air quality of the urban environment was determined using air samples collected at six locations throughout Karachi. Methane (6.3 ppmv) and ethane (93 ppbv) levels in Karachi were found to be much higher than in other cities that have been studied. The very high CH₄ levels highlight the importance of natural gas leakage in Karachi. The leakage of liquefied petroleum gas contributes to elevated propane and butane levels in Karachi, although the propane and butane burdens were lower than in other cities (e.g., Mexico City, Santiago). High levels of benzene (0.3–19 ppbv) also appear to be of concern in the Karachi urban area. Vehicular emissions were characterized using air samples collected along the busiest thoroughfare of the city (M.A. Jinnah Road). Emissions from vehicular exhaust were found to be the main source of many of the hydrocarbons reported here. Significant levels of isoprene (1.2 ppbv) were detected at the roadside, and vehicular exhaust is estimated to account for about 20% of the isoprene observed in Karachi. 1,2-Dichloroethane, a lead scavenger added to leaded fuel, was also emitted by cars. The photochemical production of ozone (O₃) was calculated for CO and the various VOCs using the Maximum Incremental Reactivity (MIR) scale. Based on the MIR scale, the leading contributors to O₃ production in Karachi are ethene, CO, propene, m-xylene and toluene.     

A scale-up field experiment for the monitoring of a burning process using chemical, audio, and video sensors

Fires are becoming more violent and frequent resulting in major economic losses and long-lasting effects on communities and ecosystems; thus, efficient fire monitoring is becoming a necessity. A novel triple multi-sensor approach was developed for monitoring and studying the burning of dry forest fuel in an open field scheduled experiment; chemical, optical, and acoustical sensors were combined to record the fire spread. The results of this integrated field campaign for real-time monitoring of the fire event are presented and discussed. Chemical analysis, despite its limitations, corresponded to the burning process with a minor time delay. Nevertheless, the evolution profile of CO₂, CO, NO, and O₂ were detected and monitored. The chemical monitoring of smoke components enabled the observing of the different fire phases (flaming, smoldering) based on the emissions identified in each phase. The analysis of fire acoustical signals presented accurate and timely response to the fire event. In the same content, the use of a thermographic camera, for monitoring the biomass burning, was also considerable (both profiles of the intensities of average gray and red component greater than 230) and presented similar promising potentials to audio results. Further work is needed towards integrating sensors signals for automation purposes leading to potential applications in real situations.     

Concentration of tetrachloroethylene in indoor air at a former dry cleaner facility as a function of subsurface contamination: a case study

A field study was performed to evaluate indoor air concentrations and vapor intrusion (VI) of tetrachloroethylene (PCE) and other chlorinated solvents at a commercial retail site in Dallas, TX. The building is approximately 40 yr old and once housed a dry cleaning operation. Results from an initial site characterization were used to select sampling locations for the VI study. The general approach for evaluating VI was to collect time-integrated canister samples for off-site U.S. Environmental Protection Agency Method TO-15 analyses. PCE and other chlorinated solvents were measured in shallow soil gas, subslab soil-gas, indoor air, and ambient air. The subslab soil gas exhibited relatively high values: PCE < or =2,600,000 parts per billion by volume (ppbv) and trichloroethylene < or =170 ppbv. The attenuation factor, the ratio of indoor air and subslab soil-gas concentrations, was unusually low: approximately 5 x 10(-6) based on the maximum subslab soil-gas concentration of PCE and 1.4 x 10(-5) based on average values.     

The performance of three cultivars of rice grown near to, and distant from, a fertiliser plant

The effects of three cultivars, two water regimes and two rates of applying nitrogen fertilisers were tested when studying the performance of rice (Oryza sativa L.) near to, and distant from, a fertiliser plant emitting atmospherically dispersed pollutants. The atmosphere near the fertiliser plant had average daily peak concentrations of 144 and 210 microg m(-3) of SO(2) and NO(2), respectively. Growth was less near to, than at a distance from, the fertiliser plant. On average it was decreased by water stress while the effects of different amounts of nitrogen fertiliser were variable. Whilst there were a number of interactions involving nitrogen and water treatments, the most consistent were associated with the responses of the three cultivars at the two locations. The three cultivars performed similarly at the unpolluted control site, but there were major differences at the polluted site. These were most clearly exemplified by changes in the proportion of dry matter allocated to yields of grain and straw. At the unpolluted site, grain accounted for about 30% of the combined yields of grain and straw. At the polluted site, grain accounted for 1, 23 and 31% of the combined grain and straw yields of cultivars CO 43 (the most sensitive), TKM 9 and GR 3 (the most tolerant). Grain yields were closely related to numbers of filled grains per plant. At the polluted site, 98% of grains failed to develop in CO 43, whereas in GR 3, the number of panicles, and therefore the potential number of grains, was significantly enhanced.     

Effects of water vapor pretreatment time and reaction temperature on CO(2) capture characteristics of a sodium-based solid sorbent in a bubbling fluidized-bed reactor

CO(2) capture from flue gas using a sodium-based solid sorbent was investigated in a bubbling fluidized-bed reactor. Carbonation and regeneration temperature on CO(2) removal was determined. The extent of the chemical reactivity after carbonation or regeneration was characterized via (13)C NMR. In addition, the physical properties of the sorbent such as pore size, pore volume, and surface area after carbonation or regeneration were measured by gas adsorption method (BET). With water vapor pretreatment, near complete CO(2) removal was initially achieved and maintained for about 1-2min at 50 degrees C with 2s gas residence time, while without proper water vapor pretreatment CO(2) removal abruptly decreased from the beginning. Carbonation was effective at the lower temperature over the 50-70 degrees C temperature range, while regeneration more effective at the higher temperature over the 135-300 degrees C temperature range. To maintain the initial 90% CO(2) removal, it would be necessary to keep the regeneration temperature higher than about 135 degrees C. The results obtained in this study can be used as basic data for designing and operating a large scale CO(2) capture process with two fluidized-bed reactors.