Concentrations of decabromodiphenyl ether in air from Southern Ontario: implications for particle-bound transport

Atmospheric concentrations are reported for the main component of the brominated flame retardant decaBDE (BDE-209) in air samples collected from Southern Ontario for the period January 23-June 06, 2002. Levels ranged from below detection to 105pgm(-3) with virtually all of BDE-209 being trapped by the filter and thus deduced to be sorbed to aerosol particles. Thus, it is likely that the long-range atmospheric transport (LRAT) of BDE-209 is controlled by the transport characteristics of the aerosols. This conclusion that BDE-209 does not have the same potential for LRAT as other more volatile PBDEs is subject to possible complications arising from the uncertainties about the LRAT potential of aerosols.     

The Chemical and Meteorological Conditions Associated with High and Low Ozone Concentrations in Southeastern Michigan and Nearby Areas of Ontario

This analysis represents the first characterization of the photochemistry and transport of ozone in the Detroit metropolitan area and provides a basis for comparing data for Detroit to that for other cities. The characterization is based on a comprehensive set of meteorological and chemical measurements obtained at a site in the urban core of Detroit during the summer of 1981, together with measurements of O₃, nitrogen oxides (NO _X ), and nonmethane organic compounds (NMOC) from rural, suburban, and urban areas in southeastern Michigan and adjacent areas of Ontario.

For the quartile (23 days) with highest ozone maxima (97-180 ppb), the maxima occurred 10-70 km north-northeast of the city on days that were warm and hazy with light southsouthwest winds. On such days there was a marked accumulation of ozone precursors (NMOC and NO_X) in the early morning, as well as a rapid chemical removal of NO _X (NO _X half-life of ～5 h) from morning to midday. The timing of the daily ozone increase across the study region suggests that local photochemical generation in a moving plume was responsible for more than half of the ozone measured downwind. However, there was also evidence that ozone transported into Detroit as part of the regional background was a significant part of the O₃ maxima on high ozone days. The average contributions of photochemistry and transport for the 23 days with the highest ozone maxima were estimated to be 57 ppb and 47 ppb, respectively.     

Concentrations of two organic contaminants in precipitation, soils and plants in the Essex region of Southern Ontario

Recent research has indicated that the atmosphere is an important pathway by which pollutants enter terrestrial and aquatic ecosystems. We report here concentrations of PCBs and octachlorostyrene (OCS) in precipitation, soils and plants in Essex County, Ontario. The average PCB concentration in urban precipitation (23 ng litre(-1)) was lower than that previously reported for urban areas in the Great Lakes basin. Differences between sites and with varying wind directions were not significant. OCS concentrations in precipitation averaged 1.6 ng litre(-1). Concentrations of PCBs in soils were 2-3 orders of magnitude greater than in precipitation. Concentrations of these pollutants in city soils and plant roots were consistently higher than those from suburban and rural sites. Ratios of urban to suburban concentrations in soils and precipitation were approximately 5:1 for PCBs. However, concentrations of OCS were similar in urban and suburban samples of precipitation, soils and plant tissues. These comparisons suggest an urban source for PCBs, but not OCS. Concentrations of all contaminants in plant leaves, unlike those in precipitation, roots and soils, were relatively similar in urban and suburban areas. That similarity suggests that direct foliar uptake is not an important pathway for pollutant uptake in plants.     

Hydrocarbon Production and Photochemical Ozone Formation in Forest Burn Plumes

The purpose of this paper is to describe ozone production in forest slash burn plumes. Plumes from controlled fires in the state of Washington were monitored using an instrumented aircraft. Ozone, oxides of nitrogen, condensation nuclei, and visual range (nephelometer) were measured continuously on board the plane. Airborne grab samples were collected for detailed hydrocarbon analysis.

The slash burn plumes were found to contain significant quantities of ozone. A buildup of 40–50 ppb above the ambient background ozone concentrations was not unusual. Hydrocarbon analyses revealed the presence of many photochemically reactive olefins in the plume. Hydrocarbon/NO _x ratios were favorable for photochemical oxidant production.     

A Comparison of Measured and Simulated Ozone Concentrations in the Rural Areas of the Eastern United States during Summer 1995

ABSTRACT

The recent regulatory actions toward a longer-term (i.e., 8-hr) average ozone standard have brought forth the potential for many rural areas in the eastern United States to be in noncompliance. However, since a majority of these rural areas have generally few sources of anthropogenic emissions, the measured ozone levels primarily reflect the effects of the transport of ozone and its precursor pollutants and natural emissions. While photochemical grid models have been applied to urban areas to develop ozone mitigation measures, these efforts have been limited to high ozone episode events only and do not adequately cover rural regions. In this study, we applied a photochemical modeling system, RAMS/UAM-V, to the eastern United States from June 1-August 31, 1995. The purpose of the study is to examine the predictive ability of the modeling system at rural monitoring stations that are part of the Clean Air Status Trends Network (CASTNet) and the Gaseous Pollutant Monitoring Program (GPMP).

The results show that the measured daily 1-hr ozone maxima and the seasonal average of the daily 1-hr ozone maxima are in better agreement with the predictions of the modeling system than those for the daily 8-hr ozone maxima. Also, the response of the modeling system in reproducing the measured range of ozone levels over the diurnal cycle is poor, suggesting the need for improvement in the treatment of the physical and chemical processes of the modeling system during the nighttime and morning hours if it is to be used to address the 8-hr ozone standard.     

Empirical Relationships between Observed Ozone Concentrations and Geographical Areas with Concentrations Likely to Be above 120 ppb

The extent to which existing ozone monitoring data can be used to represent concentrations outside the area immediately surrounding a monitoring station is investigated. The results should be of Interest to those who wish to define areas within which standards are likely to have been exceeded. Relationships are established between the observed second-maximum hour-average ozone concentrations and the area within which It is possible to state with reasonable probability that National Ambient Air Quality Standards (NAAQS) have or have not been exceeded. All pairs of SAROAD stations (Storage and Retrieval of Aerometric Data) separated by 500 km or less which had nearly complete annual data sets were considered for the years 1974 through 1977 to determine the probability that the NAAQS would be exceeded at one station of the pair, given station separation and the observed second-maximum hourly ozone concentration at the other station. The resulting relationship was applied to SAROAD data for 1977, and circles were drawn around each SAROAD monitoring site to show the area within which it is 90% probable that the 120 ppb NAAQS was exceeded during 1977.     

An Alternative Approach to Photochemical Ozone Creation Potentials Applied under European Conditions

ABSTRACT

Photochemical ozone creation potential (POCP) values for 83 different volatile organic compounds (VOCs), including CO and CH₄, were calculated under different environmental conditions representative for Europe. These calculations show that variations in POCP values are large between different types of chemical environments and that POCP values for VOCs should be presented as ranges instead of single values. POCP ranges are based on the extremes of the POCP values and are defined with the intention to include all POCP values an individual VOC will obtain in any European environment where O₃ formation is of environmental concern. The POCP ranges indicate large differences in O₃ production between individual VOCs, which justifies the use of this ranking scale instead of treating all VOCs as a homogeneous group of species in abatement strategies.

Both the average O₃ production over 96 hr and the maximum contribution to the O₃ concentration were studied. The most efficient O₃ producers were found to be iso-prene, 2-methyl-2-butene, and acrolein. As a group, the alkenes are the most potent O₃ producers, followed by higher alkanes and then the aromatics. The calculated values show a good agreement with previously calculated POCP values under northern European conditions.     

Consideration of Air Quality Standards for Vegetation With Respect to Ozone

Present evidence suggests that ozone is the most damaging of all air pollutants affecting vegetation. It is the principal oxidant in the photochemical smog complex. Concentrations of ozone have exceeded 0.5 part per million (ppm) in the Los Angeles area. One-tenth of this level for 8 hours is known to injure very sensitive tobacco varieties. Many plant species are visibly affected after a few hours exposure at concentrations much lower than 0.5 ppm. There is also some evidence that ozone reduces plant growth. Many factors must be taken into account when considering standards to protect vegetation from ozone damage. These include ozone concentration and methods of measurement, time of exposure, possible additive effects of other pollutants, sensitivity of plant species, their economic value, and the extent of injury which can be tolerated. The response of a species to the pollutant is conditioned by genetic factors and environmental conditions. Lack of specific routine methods for measuring ozone in ambient air is a handicap. California and Colorado established standards for oxidants at 0.15 and 0.10 ppm, respectively, for 1 hour. How these standards relate to the ozone dosage causing acute and chronic injury to various plant species is discussed.     

Important Considerations for Establishing a Secondary Ozone Standard to Protect Vegetation

Air quality standards are established to prevent or minimize the risk of adverse effects from air pollution to human health, vegetation, and materials. In order to develop standards which provide an adequate measure of protection to vegetation, it is necessary to define, in as precise terms as possible, the relationship between ambient air quality and the potential for adverse effects on vegetation. Based on recent evidence published in the literature, as well as retrospective studies using data from the National Crop Loss Assessment Network (NCLAN), cumulative indices can be used to describe exposures of ozone for predicting agricultural crop effects. However, the mathematical form of the standard that may be proposed to protect crops does not necessarily have to be of the same form as that used in the statistical or process oriented mathematical models that relate ambient ozone exposures with vegetation effects. This paper discusses the limitations associated with applying a simple statistic that may take the place of a more biologically meaningful exposure parameter. While the NCLAN data have been helpful in identifying indices that may be appropriate for establishing exposure-response relationships, the limitations associated with the NCLAN protocol need to be considered when attempting to apply these relationships in the establishment of a secondary national ambient air quality standard. The Weibull model derived from NCLAN experiments must demonstrate its generality and universal applicability. Furthermore, its predictive power must be tested using independent sets of field data.     

Ozone Concentrations in the Central Wasatch Mountains of Utah

Abstract

In the Salt Lake Valley, a June through August SUM60 value (sum of hourly average ozone concentrations ≥60 parts per billion by volume [ppbv]) of 25,000 ppbv-hr was exceeded in 9 yr between 1978 and 1998. Ozone concentrations in the nearby Central Wasatch Mountains were monitored to determine the potential for vegetation injury. The SUM60 value of 19,000 ppbv-hr in these mountains and peak hourly concentrations >100 ppbv suggests that ozone-sensitive species may be injured. Ozone concentrations in the mountains were greatest during periods of strong upslope winds from the Salt Lake Valley. Both SUM60 values and hourly average concentrations in the Central Wasatch Mountains were strongly correlated with those in the Salt Lake Valley, suggesting that data from valley stations could be used to estimate ozone in the mountains.     

Application of Artificial Neural Networks to Modeling and Prediction of Ambient Ozone Concentrations

ABSTRACT

The deterministic modeling of ambient O₃ concentrations is difficult because of the complexity of the atmospheric system in terms of the number of chemical species; the availability of accurate, time-resolved emissions data; and the required rate constants. However, other complex systems have been successfully approximated using artificial neural networks (ANNs). In this paper, ANNs are used to model and predict ambient O₃ concentrations based on a limited number of measured hydrocarbon species, NO_x compounds, temperature, and radiant energy. In order to examine the utility of these approaches, data from the Coastal Oxidant Assessment for Southeast Texas (COAST) program in Houston, TX, have been used. In this study, 53 hydrocarbon compounds, along with O₃, nitrogen oxides, and meteorological data were continuously measured during summer 1993. Steady-state ANN models were developed to examine the ability of these models to predict current O₃ concentrations from measured VOC and NO concentrations. To predict the future concentrations of O₃, dynamic models were also explored and were used for extraction of chemical information such as reactivity estimations for the VOC species.

The steady-state model produced an approximation of O₃ data and demonstrated the functional relationship between O₃ and VOC-NO_x concentrations. The dynamic models were able to the adequately predict the O₃ concentration and behavior of VOC-NO_x-O₃ system a number of hourly intervals into the future. For 3 hr into the future, O₃ concentration could be predicted with a root-mean squared error (RMSE) of 8.21 ppb. Extending the models further in time led to an RMSE of 11.46 ppb for 5-hr-ahead values. This prediction capability could be useful in determining when control actions are needed to maintain measured concentrations within acceptable value ranges.     

Artificial Neural Network-Derived Trends in Daily Maximum Surface Ozone Concentrations

ABSTRACT

Interannual variability in meteorological conditions can confound attempts to identify changes in ozone concentrations driven by reduced precursor emissions. In this paper, a technique is described that attempts to maximize the removal of meteorological variability from a daily maximum ozone time series, thereby revealing longer term changes in ozone concentrations with increased confidence. The technique employs artificial neural network [multilayer perceptron (MLP)] models, and is shown to remove more of the meteorological variability from U.S. ozone data than does a Kolmogorov-Zurbenko (KZ) filter and conventional regression-based technique.     

Chlorophyll Content of Soybean Foliage in Relation to Seed Yield and Ambient Ozone Pollution

A field test was conducted to determine if ozone pollution adversely affected the chlorophyll content and seed yield of soybean. Eight soybean cultivars were grown to maturity in test plots in central New Jersey; one-half of the plots was treated with an antioxidant (ethylenediurea) to protect the plants from the effects of ambient ozone and one-half was left untreated. Periodic chlorophyll measurements revealed no significant difference between EDU-treated and untreated plots during the major part of plant growth. The absence of a yield effect predicated on the normal chlorophyll content was corroborated by actual total seed measurement. Our results did not support predictive models that forecast a significant yield reduction from a 7-h seasonal mean of 0.058 ppm 0₃, but agreed with results obtained previously in Maryland and Georgia.     

Photochemical production of ozone and control strategy for Southern Taiwan

An observation-based method (OBM) is developed to evaluate the ozone (O₃) production efficiency (O₃ molecules produced per NO_x molecule consumed) and O₃ production rate (P(O₃)) during a field campaign in southern Taiwan. The method can also provide an estimate of the concentration of OH. A key step in the method is to use observed concentrations of two aromatic hydrocarbons, namely ethylbenzene and m,p-xylene, to estimate the degree of photochemical processing and amounts of photochemically consumed NO_x and NMHCs by OH. In addition, total oxidant (O₃+NO₂) instead of O₃ itself turns out to be very useful for representing ozone production in the OBM approach. The average O₃ production efficiency during the field campaign in Fall (2003) is found to be about 10.2±3.9. The relationship of P(O₃) with NO_x is examined and compared with a one-dimensional (1D) photochemical model. Values of P(O₃) derived from the OBM are slightly lower than those calculated in the 1D model. However, OH concentrations estimated by the OBM are about a factor of 2 lower than the 1D model. Fresh emissions, which affect the degree of photochemical processing appear to be a major cause of the underestimate. We have developed a three-dimensional (3D) OBM O₃ production diagram that resembles the EKMA ozone isopleth diagram to study the relationship of the total oxidant versus O₃ precursors. The 3D OBM O₃ production diagram suggests that reducing emissions of NMHCs are more effective in controlling O₃ than reducing NO_x. However, significant uncertainties remain in the OBM, and considerable more work is required to minimize these uncertainties before a definitive control strategy can be reached. The observation-based approach provides a good alternative to measuring peroxy radicals for evaluating the production of O₃ and formulating O₃ control strategy in urban and suburban environments.     

Application of the Urban Airshed Model to Forecasting Next-Day Peak Ozone Concentrations in Atlanta,Georgia

ABSTRACT

Twenty-four to forty-eight-hour ozone air quality forecasts are increasingly being used in metropolitan areas to inform the public about potentially harmful air quality conditions. The forecasts are also behind “ozone action day” programs in which the public and private sectors are encouraged or mandated to alter activities that contribute to the formation of ground-level ozone. Presented here is a low-cost application of the Urban Airshed Model (UAM), an Eulerian 3-dimensional photochemical-transport grid model for generating next-day peak ozone concentration forecasts. During the summer of 1997, next-day peak ozone concentrations in Atlanta, GA, were predicted both by a team of eight forecasters and by the Urban Airshed Model in Forecast Mode (UAM-FM). Results are presented that compare the accuracy of the team and the UAM-FM. The results for the summer of 1997 indicate that the UAM-FM may be a better predictor of peak ozone concentrations when concentrations are high (> 0.095 ppmv), and the team may be a better predictor of ozone concentrations when concentrations are low (< 0.095 ppmv). The UAM-FM is also discussed in the context of other forecasting tools, primarily linear regression models and a no-skill, persistence-based technique.     

Measurement of Ozone Concentrations in Ambient Air Using a Badge-Type Passive Monitor

Abstract

A badge-type passive monitor was used to evaluate the effectiveness of four ozone trapping reagents for measuring O₃ concentrations in the air. These were sodium nitrite (NaNO₂), 3-methyl-2-benzothiazolinone acetone azine (MBTH), p-acetamidophenol (p-ATP), and indigo carmine. Experiments in an exposure chamber showed that only NaNO₂ and MBTH monitors gave sensitive and linear responses over realistic ranges of O₃ concentrations. When tested in ambient air, NaNO₂ and MBTH monitors with a single-layer diffusion barrier overestimated O₃ concentrations by a significant amount. This was largely canceled out in the NaNO₂ monitor by using a multi-layered diffusion barrier to combat wind turbulence effects. However it had almost no effect on the MBTH monitor, and it was found that NO₂ was a source of serious interference. We concluded that using the NaNO₂ monitor with an effective diffusion barrier can measure O₃ in ambient air with an accuracy of ±16%.     

Cluster Analysis for Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans Concentrations in Southern Taiwan

Abstract

This study investigates the characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the ambient air of two municipal solid waste incinerators (MSWIs: GS and RW) and a coal-fired power plant (PW) in the Kaohsiung County (KC) area in Taiwan. The results show that the toxic equivalency (TEQ) concentration in the flue gas of GS and RW averaged 0.090 and 0.044 ng international toxic equivalents (I-TEQ)/N·m³, respectively. The TEQ concentration in the flue gas of PW averaged 0.050 ng I-TEQ/N·m³. All PCDD/Fs concentrations from the stack flue gas are lower than the Taiwan Environmental Protection Administration emission standard. Furthermore, the mean I-TEQ concentration in the ambient atmosphere ranged from approximately 0.019 to 0.165 pg I-TEQ/N·m³, much lower than the environmental quality standards for dioxins in Japan (0.6 pg TEQ/N·m³). This work classified all sampling sites into three clusters according to k-means cluster analysis. The result shows a probable direct correlation between the GS incinerator and site C. Although the concentration from the PW plant did not exceed the emission standard, it was much higher than that in Fernández-Martínez’s study. For proper environmental management of dioxins, establishing a complete emission inventory of PCDD/Fs is necessary. The government of Taiwan should particularly pay more attention to power plants to address the information shortage.     

Damage to Eastern White Pine by Sulfur Dioxide,Semimature-Tissue Needle Blight,and Ozone

Eastern white pine (Pinus strobus L.) forests were severely damaged by atmospheric sulfur dioxide up to distances of 25 miles northeast of large smelters located in the Sudbury mining district of Ontario. Damage to white pine was measured in terms of foliage, bark, and biological injuries, radial and volume growth decrement, and tree mortality. The foliar symptoms of sulfur dioxide injury on white pine trees sometimes resembles those caused by a physiogenic disease, semimature-tissue needle blight (abbreviated to SNB). Studies on the nature and etiology of SNB were conducted in white pine forests in the Upper Ottawa Valley, which are remote from smelter operations which might pollute the atmosphere. These studies included the determination of the role that naturallyoccurring atmospheric ozone plays in the occurrence of SNB. Differences between the symptoms of sulfur dioxide injury, SNB, and ozone damage are outlined.     

Measurement of Organic Acids,Aldehydes, and Ketones in Residential Environments and Their Relation to Ozone

Abstract

Ozone and several polar volatile organic compounds (VOCs) including organic acids and carbonyls (aldehydes and ketones) were measured over an approximately 24 hour period in four residences during the winter of 1993 and in nine residences during the summer of 1993. All residences were in the greater Boston, Massachusetts area. The relation of the polar VOCs to the ozone concentration was examined. Indoor carbonyl concentrations were similar between the summer and winter, with the total mean winter concentration being 31.7 ppb and the total mean summer concentration being 36.6 ppb. However, the average air exchange rate was 0.9 hr^?1 during the winter and 2.6 hr^?1 during the summer. Therefore, the estimated carbonyl emission rates were significantly higher during the summer. Indoor organic acid concentrations were about twice as high during the summer as during the winter. For formic acid, the indoor winter mean was 9.8 ppb, and the summer indoor mean was 17.8 ppb. For acetic acid, the indoor winter mean was 15.5 ppb, and the summer indoor mean was 28.7 ppb. The concentrations of the polar VOCs were found to be significantly correlated with one another. Also, the emission rates of the polar VOCs were found to be correlated with both the environmental variables such as temperature and relative humidity and the ozone removal rate; however, it was difficult to apportion the relative effects of the environmental variables and the ozone removal.