Passive Diffusion Samplers Research Articles

Quantifying the Spatial and Temporal Variation of Ground-Level Ozone in the Rural Annapolis Valley, Nova Scotia, Canada Using Nitrite-Impregnated Passive Samplers

The spatiotemporal variability of ground-level ozone (GLO) in the rural Annapolis Valley, Nova Scotia was investigated between August 29, 2006, and September 28, 2007, using Ogawa nitrite-impregnated passive diffusion samplers (PS). A total of 353 PS measurements were made at 17 ambient and 1 indoor locations over 18 sampling periods ranging from 2 to 4 weeks. The calculated PS detection limit was 0.8 ±0.02 parts per billion by volume (ppbv), for a 14-day sampling period. Duplicate samplers were routinely deployed at three sites and these showed excellent agreement (R 2 values of 0.88 [n =11], 0.95 [n =17], and 0.96 [n =17]), giving an overall PS imprecision value of 5.4%. Comparisons between PS and automated continuous ozone analyzers at three sites also demonstrated excellent agreement with R 2 values of 0.82, 0.95, and 0.95, and gradients not significantly different from unity. The minimum, maximum, and mean (±1σ) ambient annual GLO concentrations observed were 7.7, 72.1, and 34.3 ± 10.1 ppbv, respectively. The three highest sampling sites had significantly greater (P =0.032) GLO concentrations than three Valley floor sites, and there was a strong correlation between concentration and elevation (R 2 =0.82). Multivariate models were used to parameterize the observed GLO concentrations in terms of prevailing meteorology at an elevated site found at Kejimkujik National Park and also at a site on the Valley floor. Validation of the multivariate models using 30 months of historical meteorological data at these sites yielded R 2 values of 0.70 (elevated site) and 0.61 (Valley floor). The mean indoor ozone concentration was 5.4 ± 3.3 ppbv and related to ambient GLO concentration by the equation: indoor =0.34 ×ambient & 5.07. This study has demonstrated the suitability of PS for long-term studies of GLO over a wide geographic area and the effect of topographical and meteorological influences on GLO in this region.

Air quality assessment in Southern Kuwait using diffusive passive samplers

Measurements of fortnightly average concentrations of NO, NO2, SO2, H2S, NH3, and volatile organic compounds (VOCs) (aromatics=benzene, toluene, o-xylene, m+p-xylene, ethyl benzene; non-aromatics=nonane and octane) were carried out in the period from 26/10/05 to 24/11/05 at 20 points in the southern part of Kuwait as part of a baseline environmental impact assessment study requested by Kuwait National Petroleum Company. Two waves of triplicate diffusive passive samplers were used. A high volume air sampler was used to measure PM10 too. During the sampling period, the wind was observed to be mainly from the west and northwest with an average of 4.28 m/s. The consistency of the results allowed the production of spatial distribution maps of the pollutants measured and consequently the comparison between levels of air pollution at different locations. A comparison between the measured concentrations and the applicable air quality standards promulgated by Kuwait Environment Public Authority (KEPA) showed that those compounds had low concentrations compared to both industrial and residential KEPA standards. For other compounds which are not covered by KEPA standards, the results were compared with relevant limits of US Environment Protect Agency (USEPA) and US Department of Labor, Occupational Safety and Health Administration. The comparison showed that the measured compounds had low concentrations compared to the existing standards and, accordingly, no violation of air quality standards is reported.

A Cohort Study of Traffic-Related Air Pollution and Mortality in Toronto, Ontario, Canada

BackgroundChronic exposure to traffic-related air pollution (TRAP) may contribute to premature mortality, but few studies to date have addressed this topic.ObjectivesIn this study we assessed the association between TRAP and mortality in Toronto, Ontario, Canada.MethodsWe collected nitrogen dioxide samples over two seasons using duplicate two-sided Ogawa passive diffusion samplers at 143 locations across Toronto. We calibrated land use regressions to predict NO2 exposure on a fine scale within Toronto. We used interpolations to predict levels of particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5) and ozone levels. We assigned predicted pollution exposures to 2,360 subjects from a respiratory clinic, and abstracted health data on these subjects from medical billings, lung function tests, and diagnoses by pulmonologists. We tracked mortality between 1992 and 2002. We used standard and multilevel Cox proportional hazard models to test associations between air pollution and mortality.ResultsAfter controlling for age, sex, lung function, obesity, smoking, and neighborhood deprivation, we observed a 17% increase in all-cause mortality and a 40% increase in circulatory mortality from an exposure contrast across the interquartile range of 4 ppb NO2. We observed no significant associations with other pollutants.ConclusionsExposure to TRAP was significantly associated with increased all-cause and circulatory mortality in this cohort. A high prevalence of cardiopulmonary disease in the cohort probably limits inference of the findings to populations with a substantial proportion of susceptible individuals.

Validation of model calculation of ammonia deposition in the neighbourhood of a poultry farm using measured NH 3 concentrations and N deposition

Substantial emission of ammonia (NH 3) from animal houses and the related high local deposition of NH 3-N are a threat to semi-natural nitrogen-deficient ecosystems situated near the NH 3 source. In Denmark, there are regulations limiting the level of NH 3 emission from livestock houses near N-deficient ecosystems that are likely to change due to nitrogen (N) enrichment caused by NH 3 deposition. The models used for assessing NH 3 emission from livestock production, therefore, need to be precise, as the regulation will affect both the nature of the ecosystem and the economy of the farmer. Therefore a study was carried out with the objective of validating the Danish model used to monitor NH 3 transport, dispersion and deposition from and in the neighbourhood of a chicken farm. In the study we measured NH 3 emission with standard flux measuring methods, NH 3 concentrations at increasing distances from the chicken houses using passive diffusion samplers and deposition using 15N-enriched biomonitors and field plot studies. The dispersion and deposition of NH 3 were modelled using the Danish OML-DEP model. It was also shown that model calculations clearly reflect the measured NH 3 concentration and N deposition. Deposition of N measured by biomonitors clearly reflected the variation in NH 3 concentrations and showed that deposition was not significantly different from zero ( P < 0.05) at distances greater than 150–200 m from these chicken houses. Calculations confirmed this, as calculated N deposition 320 m away from the chicken farm was only marginally affected by the NH 3 emission from the farm. There was agreement between calculated and measured deposition showing that the model gives true estimates of the deposition in the neighbourhood of a livestock house emitting NH 3.

Residential vapor‐intrusion evaluation: Long‐duration passive sampling vs. short‐duration active sampling

AbstractSampling indoor air for potential vapor‐intrusion impacts using current standard 24‐hour sample collection methods may not adequately account for temporal variability and detect contamination best represented by long‐term sampling periods. Henry Schuver of the U.S. Environmental Protection Agency Office of Solid Waste stated at the September 2007 Air &amp; Waste Management Association vapor‐intrusion conference that the US EPA may consider recommending longer‐term vapor sampling to achieve more accurate time‐weighted‐average detections.In November 2007, indoor air at four residences was sampled to measure trichloroethene (TCE) concentrations over short‐ and long‐duration intervals. A carefully designed investigation was conducted consisting of triplicate samplers for three different investigatory methods: dedicated 6‐liter Summa canisters (US EPA Method TO‐15), pump/sorbent tubes (US EPA Method TO‐17), and passive diffusion samplers (MDHS 80). The first two methods collected samples simultaneously for a 24‐hour period, and the third method collected samples for two weeks.Data collected using Methods TO‐15 (canisters) and TO‐17 (tubes) provided reliable short‐duration TCE concentrations that agree with prior 24‐hour sampling events in each of the residences; however, the passive diffusion samplers may provide a more representative time‐weighted measurement. The ratio of measured TCE concentrations between the canisters and tubes are consistent with previous results and as much as 28.0 μg/m3 were measured. A comparison of the sampling procedures, and findings of the three methods used in this study will be presented. © 2008 Wiley Periodicals, Inc.

Biological monitoring of low benzene exposure in Italian traffic policemen

A comparative evaluation of urinary biomarkers was carried out to characterize benzene exposure in a group of 100 traffic policemen of the city of Parma (Italy). All subjects were monitored once, in two consecutive days characterized by similar climatic conditions but preceded by two windy days. Benzene ambient concentration measured by municipal air monitoring stations was 1 μg/m 3 (Day 1) and 2 μg/m 3 (Day 2). Personal exposure to ambient concentrations of benzene, toluene, ethylbenzene and xylene (BTEX) was assessed by using Radiello ® passive-diffusive samplers in a subgroup of 24 workers. Benzene metabolites, t, t-muconic acid ( t, t-MA) and S-phenylmercapturic acid ( S-PMA) were determined by isotopic dilution liquid chromatography– tandem mass spectrometry on spot urine samples collected at the end of the shift. Urinary benzene (U-B) was determined by solid-phase microextraction gas chromatography–mass spectrometry. Airborne benzene concentration expressed as median [and interquartile range] was 6.07 [0.28–9.53] μg/m 3, as assessed by personal sampling. Urinary concentrations of biomarkers in the whole group were 41.8 [34.1–89.8] μg/g creatinine for t, t-MA, 0.67 [0.23–1.32] μg/g creatinine for S-PMA, and 0.16 [0.13–0.26] μg/l for U-B. Smokers eliminated significantly higher concentrations of unchanged BTEX and benzene metabolites than non-smokers ( p < 0.05). When traffic policemen were distinguished into indoor ( n = 31) and outdoor workers, no significant differences were observed for either airborne benzene or urinary biomarkers. Significantly lower concentrations of S-PMA and U-B were determined in samples collected at Day 1 as compared to Day 2 ( p < 0.0001 and p = 0.003, respectively) suggesting that these biomarkers are enough sensitive and specific to detect changes in airborne benzene concentration even at few μg/m 3.

확산측정기를 이용한 대전시 도로변에서의 이산화질소 측정

This study investigates the variation and spatial distribution of nitrogen dioxide(<TEX>$NO_2$</TEX>) concentrations measured with passive diffusive samplers at 40 curbside points in Daejeon. Average <TEX>$NO_2$</TEX> concentration was <TEX>$39.8{\pm}18.0\;ppb$</TEX> (n=1,127) and the significant difference in concentrations by regional groups (Dong-gu, Jung-gu, Seo-gu, Daedeok-gu, Yuseong-gu) was not observed. The frequency distribution of <TEX>$NO_2$</TEX> concentration was found to be a normal distribution with the high frequency in the concentration range of 30 to 40 ppb (20 to 25%). Average <TEX>$NO_2$</TEX> concentration measured during the rainy periods was lower than that measured during the non-rainy periods and the decrease of concentration by rainfall was about 16% (7 ppb). The variation of <TEX>$NO_2$</TEX> concentrations measured by passive diffusive samplers during the sampling period was similar to that continuously measured at the air quality monitoring station.

Passive dosimeters for nitrogen dioxide in personal/indoor air sampling: A review

Accurate measurement of nitrogen dioxide concentrations in both outdoor and indoor environments, including personal exposures, is a fundamental step for linking atmospheric nitrogen dioxide levels to potential health and ecological effects. The measurement has been conducted generally in two ways: active (pumped) sampling and passive (diffusive) sampling. Diffusion samplers, initially developed and used for workplace air monitoring, have been found to be useful and cost-effective alternatives to conventional pumped samplers for monitoring ambient, indoor and personal exposures at the lower concentrations found in environmental settings. Since the 1970s, passive samplers have been deployed for ambient air monitoring in urban and rural sites, and to determine personal and indoor exposure to NO2. This article reviews the development of NO2 passive samplers, the sampling characteristics of passive samplers currently available, and their application in ambient and indoor air monitoring and personal exposure studies. The limitations and advantages of the various passive sampler geometries (i.e., tube, badge, and radial type) are also discussed. This review provides researchers and risk assessors with practical information about NO2 passive samplers, especially useful when designing field sampling strategies for exposure and indoor/outdoor air sampling.

Determination of Dominant Biogeochemical Processes in a Contaminated Aquifer‐Wetland System Using Multivariate Statistical Analysis

Determining the processes governing aqueous biogeochemistry in a wetland hydrologically linked to an underlying contaminated aquifer is challenging due to the complex exchange between the systems and their distinct responses to changes in precipitation, recharge, and biological activities. To evaluate temporal and spatial processes in the wetland-aquifer system, water samples were collected using cm-scale multi-chambered passive diffusion samplers (peepers) to span the wetland-aquifer interface over a period of 3 yr. Samples were analyzed for major cations and anions, methane, and a suite of organic acids resulting in a large dataset of over 8000 points, which was evaluated using multivariate statistics. Principal component analysis (PCA) was chosen with the purpose of exploring the sources of variation in the dataset to expose related variables and provide insight into the biogeochemical processes that control the water chemistry of the system. Factor scores computed from PCA were mapped by date and depth. Patterns observed suggest that (i) fermentation is the process controlling the greatest variability in the dataset and it peaks in May; (ii) iron and sulfate reduction were the dominant terminal electron-accepting processes in the system and were associated with fermentation but had more complex seasonal variability than fermentation; (iii) methanogenesis was also important and associated with bacterial utilization of minerals as a source of electron acceptors (e.g., barite BaSO(4)); and (iv) seasonal hydrological patterns (wet and dry periods) control the availability of electron acceptors through the reoxidation of reduced iron-sulfur species enhancing iron and sulfate reduction.

Laboratory and field evaluation of a diffusive sampler for measuring halogenated anesthetic compounds

Anesthetic gases such as desflurane, sevoflurane, isoflurane, enflurane, and halothane are used on a daily basis in operating theaters. Active sampling has historically been used to control the level of exposure to personnel. SKC 575-002 is a diffusive passive sampler filled with Anasorb 747. We validated this sampler in both laboratory and field experiments. Parameters tested were desorption efficiency, concentration, sampling time, relative humidity, and reverse diffusion, as well as storage stability for up to 8 weeks. Uptake rates were achieved by comparison with active sampling for each passive sampling trial of 1,4, or 8 h. Analysis and detection were performed using gas chromatography with flame ionization detection (GC/FID). Multiple regression analysis was used to evaluate the influence of time, concentration, dose, and relative humidity. In the field evaluation experiments, intraclass correlation coefficients (ICC) were estimated. In the laboratory experiments, no problems were found with storage stability or reverse diffusion. The sampling rates for the five anesthetics vary, however, with exposure time and exposure level, with generally higher uptake rates at low concentrations and short sampling times. In the field experiments there was high agreement between the active and passive samplers for halothane, sevoflurane, and isoflurane (ICC > 0.83). When performing whole-day workplace measurements (TWA measurements) the SKC 575-002 can be recommended, and at levels around 1 ppm the following uptake rates should be used: enflurane and halothane, 12.3 mL min(-1); desflurane, 13.6 mL min(-1); isoflurane, 12.0 mL min(-1); and sevoflurane, 11.9 mL min(-1).

Integrated Sampling and Analytical Approach for Common Groundwater Dissolved Gases

A novel passive gas diffusion sampler (PGDS) combines sampling, storage and direct injection into a single gas chromatograph (GC). The sampler has a 4.5 mL internal volume when deployed, is easy to operate, and eliminates sample-partitioning. The associated GC method analyzes for a large, dynamic sampling range from a single, small volume injection. Dissolved gases were separated on parallel Rt-Molsieve 5A and Rt-Q-PLOT columns and eluted solutes were quantified using a pulse discharge helium ionization detector (PD-HID). The combined sampling and analytical method appears to be less prone to systematic bias than conventional sampling and headspace partitioning and analysis. Total dissolved gas pressure used in tandem with the PGDS improved the accuracy of dissolved gas concentrations. The incorporation of routine measurements of dissolved biogeochemical and permanent gases into groundwater investigations will provide increased insight into chemical and biological processes in groundwater and improve chemical mass balance accuracy.

Emissions of ammonia from weeping wall stores and earth-banked lagoons determined using passive sampling and atmospheric dispersion modelling

Ammonia emissions from stored farm manures form a small but significant proportion (∼10%) of the total emitted annually from UK sources. These emissions are regulated by factors including: the surface area of the store; the storage method; the physical form of the stored manure and the source of manure. A method was developed to estimate in situ emissions from a range of store types (weeping wall and earth-banked lagoon) that are currently under-represented in UK emissions estimates. Passive diffusion samplers (Willems Badges) were used to determine vertical concentration profiles to a height of 4.5 m at a number of locations around each slurry store. An atmospheric dispersion model was applied to estimate the contribution from emissions from other on-farm ammonia sources to the measured data and also to determine the emission rates from the stored manure. A procedure was applied whereby the emission rates from each source were allowed to vary and a numerical equation solver was applied to backfit the modelled data set to the field measurements. Measurements were collected at four farms on a monthly basis throughout the year, with each dataset being collected over 24 h. The uncertainties in the estimates of emissions from the slurry stores during individual measurement periods typically ranged between 20–40% though higher uncertainties occurred when emission fluxes from the stores were below 0.25 g NH3–N m−2 day−1 and were entrained in the wakes, and mixed with the emissions, of adjacent buildings. The average emission from the farms was 0.6 g NH3–N m−2 day−1 which agrees with other recent data on ammonia emissions from crusted slurry stores and, though it is within the range of data considered in the UK emissions inventory, suggests that emissions from weeping wall stores and earth-banked lagoons may be currently overestimated in national predictions.

Centimeter-scale characterization of biogeochemical gradients at a wetland–aquifer interface using capillary electrophoresis

Steep biogeochemical gradients were measured at mixing interfaces in a wetland–aquifer system impacted by landfill leachate in Norman, Oklahoma. The system lies within a reworked alluvial plain and is characterized by layered low hydraulic conductivity wetland sediments interbedded with sandy aquifer material. Using cm-scale passive diffusion samplers, “peepers”, water samples were collected in a depth profile to span interfaces between surface water and a sequence of deeper sedimentary layers. Geochemical indicators including electron acceptors, low-molecular-weight organic acids, base cations, and NH 4 + were analyzed by capillary electrophoresis (CE) and field techniques to maximize the small sample volumes available from the centimeter-scale peepers. Steep concentration gradients of biogeochemical indicators were observed at various interfaces including those created at sedimentary boundaries and boundaries created by heterogeneities in organic C and available electron acceptors. At the sediment–water interface, chemical profiles with depth suggest that SO 4 2 - and Fe reduction dominate driven by inputs of organic C from the wetland and availability of electron acceptors. Deeper in the sediments (not associated with a lithologic boundary), a steep gradient of organic acids (acetate maximum 8.8 mM) and NH 4 + (maximum 36 mM) is observed due to a localized source of organic matter coupled with the lack of electron acceptor inputs. These findings highlight the importance of quantifying the redox reactions occurring in small interface zones and assessing their role on biogeochemical cycling at the system scale.

Modeling the intra-urban variability of outdoor traffic pollution in Oslo, Norway—A GA 2LEN project

Traffic is a major source of air pollutants in urban environments, and exposure to these pollutants may be associated with adverse health effects. However, inconsistencies in observational epidemiological studies may be caused by differential measurement errors in various approaches in assessing exposure. We aimed to evaluate a simple method for assessing outdoor air pollutant concentrations in Oslo, Norway, through a land-use regression method. Samples of nitrogen oxides (NO x ) were collected in two different weeks using Ogawa passive diffusion samplers simultaneously at 80 locations across Oslo. Independent variables used in subsequent regression models as predictors of the pollutants were derived using the Arc 9 geographic information system (GIS) software. Indicators of land use, traffic, population density, and physical geography were tested. The final regression model yielded an adjusted coefficient of determination ( R 2) of 0.77 for nitrogen dioxide (NO 2), 0.66 for nitric oxide (NO), and 0.73 for NO x . The results suggest that a good predictive exposure model can be derived from this approach, which can be used to estimate long-term small-area variation in concentrations for individual exposure assessment in epidemiological studies in a highly cost-effective way. These small-area variations in traffic pollution are important since they may have associations with health effects.

Geostatistical characterization of nitrogen dioxide concentration in an urban area: Part II: Time component of the estimation error

The temporal component of the estimation error is usually neglected in calculation of the variance of the error associated with the mapping of annual nitrogen dioxide (NO 2) concentration. However, under realistic hypotheses, adding a temporal term to the spatial estimation variance is convenient enough. In a survey using passive diffusion samplers, which was carried out in 2001 on the Mulhouse area, the two measurement phases do not allow calculation of variance of the temporal error. But this error is accessible by means of the few fixed analyzers that continuously measure NO 2 concentrations. The statistics of the experimental temporal error are examined and the temporal variogram is calculated. Experimental quadratic error is then compared to the theoretical estimation variance, deduced from the temporal variogram. The fixed analyzers available in Alsace are then used to “optimize” empirically the duration and the date of the beginning of the temporary measurement phases. Without increasing the cost of the temporary survey, it is then possible to improve the precision of the maps of annual NO 2 concentration, by combining the spatial optimization presented in Part I of the paper, and the temporal optimization presented here.

장기 NO2및 SO2Passive Diffusive Sampler(PDS)를 이용한 대전시 대기질 모니터링

TOMS/AI data with nearly 20 years are utilized in the paper to evaluate dust activities in North China. Combined with simultaneous NCEP reanalysis climate data, climate effects on dust activities are assessed. The results showed that the whole North China suffers impact by dust aerosols, with three centers standing out in TOMS/AI spring average map that are western three basins, which are characterized by lower annual precipitation and elevation. Gobi deserts in Mongolia Plateau do not attain higher TOMS/AI value due to cloud contamination and relative higher elevation. Spring is the season with the highest TOMS dust aerosol index; within the western three basins, high dust aerosol index appears in both spring and summer, especially in Tarim Basin. Wind speed in spring and precipitation in previous rainy season play important roles in controlling dust activities, higher wind speed and less precipitation than the normal are in favor of dust activities in spring. Temperature in spring and previous winter also affect dust activity to a certain extent, but with contrary spatial distribution. Temperature in winter exert effect principally in west part, contrarily, temperature effect in spring is mainly shown in east part. Both of them have negative correlation with dust activity.

Modeling the Intraurban Variability of Ambient Traffic Pollution in Toronto, Canada

The objective of this paper is to model determinants of intraurban variation in ambient concentrations of nitrogen dioxide (NO2) in Toronto, Canada, with a land use regression (LUR) model. Although researchers have conducted similar studies in Europe, this work represents the first attempt in a North American setting to characterize variation in traffic pollution through the LUR method. NO2 samples were collected over 2 wk using duplicate two-sided Ogawa passive diffusion samplers at 95 locations across Toronto. Independent variables employed in subsequent regression models as predictors of NO2 were derived by the Arc 8 geographic information system (GIS). Some 85 indicators of land use, traffic, population density, and physical geography were tested. The final regression model yielded a coefficient of determination (R2) of .69. For the traffic variables, density of 24-h traffic counts and road measures display positive associations. For the land use variables, industrial land use and counts of dwellings within 2000 m of the monitoring location were positively associated with NO2. Locations up to 1500 m downwind of major expressways had elevated NO2 levels. The results suggest that a good predictive surface can be derived for North American cities with the LUR method. The predictive maps from the LUR appear to capture small-area variation in NO2 concentrations. These small-area variations in traffic pollution are probably important to the exposure experience of the population and may detect health effects that would have gone unnoticed with other exposure estimates.

A Longitudinal Study of Nitrogen Dioxide Concentrations Around a Major Metropolitan Airport: 1987–2005

P-058 Introduction: Nitrogen dioxide (NO2) is regulated in the United States as a “criteria pollutant” suggesting ubiquitous sources and the potential for adverse health impact. A major source of NO2 is combustion. Jet aircraft with their high temperature combustion produce a significant amount of NO2 particularly during the take-off phase. There has been much interest in air pollution, including NO2, in communities surrounding large airports. Other air contaminants, including various hydrocarbons and aldehydes, are also commonly associated with aircraft. Since NO2 is produced by the same sources, it may be viewed as a surrogate for these compounds as well. Thus the spatial distribution and temporal variability in these compounds is of interest in assessing the impact of airport-related contamination on the surrounding community. Methods: Nitrogen dioxide concentrations were monitored at 28 locations both on airport grounds and in the surrounding community for one week each month commencing in 1987 and continuing through 2005, a total of 19 years. Passive diffusion (Palmes) samplers were used. All samplers were placed in duplicate in sheltered holders designed to reduce wind effects and protect the samplers from the elements. Statistical analyses were designed to assess overall and neighborhood concentrations, temporal trends and variability, seasonality, and source contributions. Results: Results show a downward trend in nitrogen dioxide during this period with an average 40% reduction in concentrations occurring from an average of about 25 ppb in 1987 to less than 15 ppb in 2005. Neighborhood-level aggregation shows that levels on the airport runways are similar to concentrations found in the surrounding community. Higher levels are found in areas subject to increased motor vehicle traffic. Long-term measures suggest a precision of 10% for the method. Further, less than 5% of the samples were lost due to all causes, including vandalism, weather, and other causes. Discussion and Conclusions: The data presented represent one of the longest continuous records of an air pollutant currently available. The passive sampling method for nitrogen dioxide is low in cost allowing for a greater spatial coverage of a given area. Further, the use of these sampler results as surrogates for other contaminants offers an excellent screening tool. Researchers investigating strategies designed to assess the impact of airports on community pollutant levels may wish to consider this type of design in conjunction with the continuous-monitor data collection.

Ammonia emissions from outdoor concrete yards used by livestock—quantification and mitigation

Outdoor concrete yards are commonly found on UK livestock farms, and, to a lesser extent, elsewhere in Europe, and represent a potentially significant source of ammonia (NH 3) emissions to the atmosphere. This study provided further measurements from a larger sample than previously made, to improve the robustness of the estimate of total NH 3 emission for inclusion in the UK NH 3 emission inventory. In addition, an assessment was made of a number of potential mitigation strategies. Measurements were made using the equilibrium concentration technique, employing small dynamic chambers and passive diffusion samplers, from 20 yards used by livestock on commercial farms. Mean emission rates (±standard error) were 0.31±0.07, 0.23±0.12, 0.19±0.05 and 0.18±0.09 g NH 3–N m −2 h −1 (0.70±0.21, 0.53±0.34, 0.76±0.22 and 0.18±0.14 g NH 3–N animal −1 h −1) for dairy cow-collecting yards, dairy cow-feeding yards, beef-feeding yards and sheep-feeding/handling areas, respectively, with mean respective livestock densities of 0.3, 0.5, 0.2 and 1.1 animals per m 2. There was a significant effect of season, with lower emission rates in the winter. There was a significant, albeit poor, positive linear relationship between emission rate and ambient air temperature ( r 2=0.22) and between emission rate and total ammoniacal N content on the yard surface ( r 2=0.14), but not with ambient wind speed. Pooling data from the present study with that from previous studies gave mean emission factors of 0.47±0.09, 0.98±0.39 and 0.13±0.09 g NH 3–N animal −1 h −1 for yards used by dairy cattle, beef cattle and sheep, respectively. Inclusion of these values, together with survey data on yard use, gave a total annual UK emission of approximately 25 kt NH 3 (95% confidence interval of 12–40 kt NH 3), representing almost 10% of total NH 3 emission from UK agriculture. In controlled studies, pressure washing and the use of a urease inhibitor in addition to yard scraping were found to be effective means of reducing emissions compared with yard scraping alone. Reduction of yard area per animal was also an effective strategy to reduce total emissions.

Use of passive diffusion sampling method for defining NO2 concentrations gradient in São Paulo, Brazil

BackgroundAir pollution in São Paulo is constantly being measured by the State of Sao Paulo Environmental Agency, however there is no information on the variation between places with different traffic densities. This study was intended to identify a gradient of exposure to traffic-related air pollution within different areas in São Paulo to provide information for future epidemiological studies.MethodsWe measured NO2 using Palmes' diffusion tubes in 36 sites on streets chosen to be representative of different road types and traffic densities in São Paulo in two one-week periods (July and August 2000). In each study period, two tubes were installed in each site, and two additional tubes were installed in 10 control sites.ResultsAverage NO2 concentrations were related to traffic density, observed on the spot, to number of vehicles counted, and to traffic density strata defined by the city Traffic Engineering Company (CET). Average NO2concentrations were 63μg/m3 and 49μg/m3 in the first and second periods, respectively. Dividing the sites by the observed traffic density, we found: heavy traffic (n = 17): 64μg/m3 (95% CI: 59μg/m3 – 68μg/m3); local traffic (n = 16): 48μg/m3 (95% CI: 44μg/m3 – 52μg/m3) (p < 0.001).ConclusionThe differences in NO2 levels between heavy and local traffic sites are large enough to suggest the use of a more refined classification of exposure in epidemiological studies in the city. Number of vehicles counted, traffic density observed on the spot and traffic density strata defined by the CET might be used as a proxy for traffic exposure in São Paulo when more accurate measurements are not available.