Characterization of an episode with elevated ozone concentrations.

A detailed analysis has been made of a seven day period in 1973, during which elevated ozone levels were observed at Ottawa. In addition to the ozone data, results are also presented for oxides of nitrogen, carbon monoxide, methane, total hydrocarbons and particulate matter. The particulates were analyzed for seven constituents, including the cations ammonium, calcium, sodium, potassium and lead and the anions sulfate and nitrate. Also measured were several other properties of the particulates, including the size distribution. It was found that none of the other gaseous pollutants showed any increase in concentration when high ozone levels were present. In contrast, the particulate matter did increase and several constituents, notably ammonium and sulfate, showed a dramatic rise. A comparison with ozone data from Toronto and upper New York state showed that the high ozone concentrations were widespread. A meteorological analysis showed that elevated ozone levels were associated with a Tropical air mass with a moderate southwesterly flow of air. Trajectory calculations were carried out to show the origin of the air over Ottawa before, during and after the period of increased ozone.     

Analysis of high level ozone concentrations using nonparametric methods

Controlling emissions of air pollutants and establishing air quality objectives to improve and protect ambient air quality are very important tasks of Governments. Ozone (O₃), one of those pollutants of concern, is not emitted directly into the atmosphere, but is a secondary pollutant produced by reaction between nitrogen dioxide (NO₂), hydrocarbons and sunlight. High levels of ozone can produce harmful effects on human health and the environment in general. Therefore, the study of extreme values of ozone represents an important topic of research in environmental problems. Classical extreme value theory has been usually used in air-pollution studies. It consists of fitting a parametric generalized extreme value (GEV) distribution to a data set of extreme values and using the estimated distribution to compute quantities like the probability of exceedance, the quantiles, the return levels or the mean return periods. In this paper, we propose nonparametric methods to estimate those quantities. Additionally, nonparametric estimators of the trends of very high values of ozone are proposed. The nonparametric estimators are applied to real samples of maximum ozone values obtained from several monitoring stations belonging to the Automatic Urban and Rural Network (AURN) from the UK. Results show that nonparametric estimators work satisfactorily, generally outperforming the behaviour of classical parametric estimators.     

Ground level ozone concentrations at a rural location in northern Spain

A systematic analysis of surface ozone observations at a rural area of the upper Spanish plateau is presented. A near four-year study of ozone concentrations was carried out between February 2000 and October 2003. Diurnal and monthly variations of ozone are studied. The peak concentration levels are obtained between 13:00 and 15:00 GMT and the lowest levels at 4:00 and 5:00 GMT. The highest values together with a slight increase in data variability are found from April to August, when spring and summer maxima are appreciated. The relationship between synoptic-scale atmospheric transport patterns and the maximum ozone concentrations was also examined. Analysis of the 500-hPa synoptic weather patterns revealed that the highest values occur during continental and Atlantic ridges in summer and, to a lesser extent, during troughs in the east-northeast of the Iberian Peninsula in spring. Our approach entailed calculating 3-day isobaric backward air mass trajectories at the observational site sorted on the following main origins: European continent, African continent, Atlantic Ocean and local. The assessment of the results showed the influence of local conditions on the daily maximum ozone concentrations. Moreover, continental air masses provide certain evidence of long-range transport added to the local or regional contribution of the main cities affecting the sampling site. Conversely, Atlantic trajectories show the least contribution to ozone levels.     

Some factors affecting the ambient ozone concentrations measured at Ottawa

The concentration of ozone was measured from June 1972 to February 1973 at a location just outside the centre of Ottawa. Average monthly ozone levels were found to fall on a smooth curve with a maximum concentration in early summer and a minimum concentration in November. The daily ozone concentration profiles showed a consistent pattern, with a significant difference, however, between weekdays and weekends. The strong morning minimum found on weekdays could be attributed to anthropogenic effects. Measurements of NO and NO₂ concentrations appear to confirm the role of NO as the pollutant primarily responsible for the destruction of ozone.     

The impact of anthropogenic and biogenic emissions on surface ozone concentrations in Istanbul

Surface ozone concentrations at Istanbul during a summer episode in June 2008 were simulated using a high resolution and urban scale modeling system coupling MM5 and CMAQ models with a recently developed anthropogenic emission inventory for the region. Two sets of base runs were performed in order to investigate for the first time the impact of biogenic emissions on ozone concentrations in the Greater Istanbul Area (GIA). The first simulation was performed using only the anthropogenic emissions whereas the second simulation was performed using both anthropogenic and biogenic emissions. Biogenic NMVOC emissions were comparable with anthropogenic NMVOC emissions in terms of magnitude. The inclusion of biogenic emissions significantly improved the performance of the model, particularly in reproducing the low night time values as well as the temporal variation of ozone concentrations. Terpene emissions contributed significantly to the destruction of the ozone during nighttime. Biogenic NMVOCs emissions enhanced ozone concentrations in the downwind regions of GIA up to 25 ppb. The VOC/NO_x ratio almost doubled due to the addition of biogenic NMVOCs. Anthropogenic NO_x and NMVOCs were perturbed by ± 30% in another set of simulations to quantify the sensitivity of ozone concentrations to the precursor emissions in the region. The sensitivity runs, as along with the model-calculated ozone-to-reactive nitrogen ratios, pointed NO_x-sensitive chemistry, particularly in the downwind areas. On the other hand, urban parts of the city responded more to changes in NO_x due to very high anthropogenic emissions.     

Problems of reunified Jerusalem

The reunification of Jerusalem following the war between Israel and Jordan in 1967 has not solved many of the most difficult problems facing the city. More than 20 years later the same difficulties persist here as in the West Bank.     

Surface ozone concentrations and ecosystem health: past trends and a guide to future projections

This paper reviews current understanding of the sources and sinks of ozone in the troposphere, recent studies of long-term trends, and the factors which have to be taken into consideration when constructing and interpreting future models of ozone concentration. The factors controlling surface O₃ concentrations are discussed initially to provide a basis for the ensuing discussion, followed by a summary of the evidence for recent trends in ground-level ozone concentrations, i.e. over the past 3 decades, which have shown a significant increase in the annual average in ‘background’ air typical of the unpolluted northern hemisphere. Closer to precursor sources, although urban winter concentrations have increased, rural peak spring and summer concentrations during ozone ‘episodes’ have decreased markedly in response to emissions reductions. In order to determine whether such trends are meaningful, the statistical techniques for determining temporal trends are reviewed. The possible causes of long-term trends in ozone are then discussed, with particular reference to the use of chemistry-transport models to interpret past trends. Such models are also used to make predictions of future trends in surface ozone concentrations, but few are comprehensive in integrating future climate changes with changes in land use and in emissions of ozone precursors. Guidance is given on the likely effects of climate/precursor/chemistry interactions so that model predictions can be judged.     

Trends of phosphorus,nitrogen and chlorophyll a concentrations in Finnish rivers and lakes in 1975-2000

During recent decades the amounts of nutrients discharged to Finnish surface waters have markedly decreased. This has been achieved by considerable investments in water protection, which were made mainly to improve municipal and industrial wastewater purification. We investigated whether these water protection measures have decreased phosphorus and nitrogen concentrations in Finnish rivers and lakes. In addition, possible trends in chlorophyll a concentrations in lakes were studied. The data consisted of a total of over 68000 monitoring results of 22 rivers and 173 lakes (or sub-basins of lakes) with different types of catchment areas. The study period covered the years 1975-2000 and the non-parametric Kendall Tau b and Seasonal Kendall tests were applied for detecting trends. Decreasing nutrient concentration trends were typical in many lakes and rivers earlier polluted by municipal and industrial wastewaters. Increasing nutrient concentration trends were common in smaller rivers and lakes receiving diffuse loading from agriculture. The results show that the investments directed towards wastewater purification have effectively improved the quality of Finnish inland waters. However, no clear effects of decreasing non-point loading were found. Thus, more effective measures should be directed towards decreasing non-point source loading.     

Integrating monitoring networks to obtain estimates of ground-level ozone concentrations --a proof of concept in Tuscany (central Italy)

Prior to 2000 a network of conventional ozone (O3) analysers existed in the Province of Firenze (Tuscany, central Italy). Between 2000 and 2004 the network was extended to incorporate a newly designed bioindicator network of tobacco plants (Nicotiana tabacum Bel W3). The objective was to set-up an integrated monitoring system to obtain estimates of ground-level O3 concentrations over the whole study area (3513 km2) in order to fill data gaps and cover reporting requirements. The existing conventional monitors were purposefully located mainly in urban areas. A total of 45 biomonitoring sites were selected using a systematic design to cover the target area. Two to five additional biomonitoring sites were co-located with conventional O3 analysers for calibration purposes, and five more sites for independent validation of modelled O3 concentrations. Visible Leaf Injury Index (LII) on the tobacco plants was significantly correlated (P: 0.018/0.0014) with a series of O3 exposure variables (mean of weekly 1-hour maxima, M1; mean of 7-hour means, M7; 24-hour mean, M24; and weekly AOT40). LII was found to be a significant predictor of weekly means of the O3 exposure variables with a standard error of estimates between 13.6 and 24.3 microg m(-3) (absolute values). LII was mapped with an ad-hoc spatial model over the study area at a 22 km grid resolution, and mapped values were used to predict O3 concentrations by means of a first order linear model. Results showed that high estimates of O3 (up to 188 microg m(-3) as mean of weekly maxima, M1) occurred more frequently in hilly and mountainous areas, with a spatial pattern changing on an annual basis. Predicted O3 concentrations were not significantly different from the measured concentrations (P: 0.34), although marked differences were observed for individual sites and years. The study provided evidence that integration of monitoring networks using different methods can be a viable option to obtain estimates of O3 concentrations over large areas.     

Invisible city: a Jerusalem in the forest?

The Bielski partisans are perhaps the most famous of the 'Forest Jews' of Belarus, Jews who engaged in active resistance to the Germans in the years between 1941 and 1944 from their hide-outs in the forest. When they escaped to 'partisan country' Jews had to adjust to an entirely new physical and social environment. Persecuted by one of the most technologically advanced armies in the world, and forced by circumstances to join the Soviet-led, communist, anti-religious partisan movement, the Bielski group faced numerous social and cultural dilemmas in establishing the living conditions that ensured their survival. The extreme cold of the Russian winter made circumstances extremely harsh, 'living like animals'1 according to one partisan, although in time life improved sufficiently for many in the Bielski detachment to believe that their final camp had acquired the status of a small town or shtetl. If, however, such military camps have often recalled more established urban settlements, this question requires clarification in the Bielski case, and is the principal focus of this paper. In its examination of the dwellings and settlements constructed by the Bielski group, and how they evolved over time, the study underlines the minimum dimensions of culture that arise in near-survival conditions.     

The 1996 Paso del Norte Ozone Study: analysis of meteorological and air quality data that influence local ozone concentrations

The 1996 Paso del Norte Ozone Study and subsequent data analyses were implemented to develop an understanding of the chemical and physical processes which lead to high concentrations of ozone in the Paso del Norte study area which includes El Paso County, Texas, Sunland Park, New Mexico, and Ciudad Juárez, Mexico. Both the data and data analysis results are being used to support photochemical grid modeling. El Paso County and Sunland Park fail to meet the National Ambient Air Quality Standard (NAAQS) for ozone, and neighboring Ciudad Juárez fails to meet the Mexican ambient standard for ozone. This paper summarizes the measurement campaigns of the 1996 Paso del Norte Ozone Study and the findings and conclusions that arose from subsequent data analyses. Data analyses showed that high ozone concentrations resulted from a combination of conditions, including high surface temperatures, strong sunlight with few clouds, light surface winds and high concentrations of ozone precursors at ground level in the morning, and slow convective boundary layer (CBL) growth. Synoptic-scale meteorological conditions observed during high ozone episodes included an aloft high-pressure system and aloft warming. Aloft carryover of ozone and ozone precursors did not significantly contribute to high concentrations of ozone at the surface.     

Trends of phosphorus, nitrogen and chlorophyll a concentrations in Finnish rivers and lakes in 1975–2000

During recent decades the amounts of nutrients discharged to Finnish surface waters have markedly decreased. This has been achieved by considerable investments in water protection, which were made mainly to improve municipal and industrial wastewater purification. We investigated whether these water protection measures have decreased phosphorus and nitrogen concentrations in Finnish rivers and lakes. In addition, possible trends in chlorophyll a concentrations in lakes were studied. The data consisted of a total of over 68 000 monitoring results of 22 rivers and 173 lakes (or sub-basins of lakes) with different types of catchment areas. The study period covered the years 1975–2000 and the non-parametric Kendall Tau b and Seasonal Kendall tests were applied for detecting trends. Decreasing nutrient concentration trends were typical in many lakes and rivers earlier polluted by municipal and industrial wastewaters. Increasing nutrient concentration trends were common in smaller rivers and lakes receiving diffuse loading from agriculture. The results show that the investments directed towards wastewater purification have effectively improved the quality of Finnish inland waters. However, no clear effects of decreasing non-point loading were found. Thus, more effective measures should be directed towards decreasing non-point source loading.     

Kinetic regularities of ozone decomposition in water

The paper studied the impact of the pH and temperature on kinetics of ozone decomposition in water. It has been shown that in the pH range 4 to 8 it is well described by the equation of the second order reaction. At an increase of the pH and temperature the rate of ozone decomposition increases. The relationship between the logarithm of the constant and the pH at 19°C corresponds to the equation log k_(pH) = −0.7 + (0.49 ± 0.03)(pH 4). The energy of ozone decomposition activation constitutes 76.0 ± 8.3 kJ/mol. The presence in the solution of phosphate ions and tert-butyl alcohol substantially increases the rate of the decomposition chain process.     

Disinfection of viruses in sewage by ozone

The action of ozone on poliovirus was examined employing two different methods. In the first, the filtered sewage together with a virus inoculum was added to a buffer solution which contained known concentrations of ozone. The most outstanding finding was the complete disappearance of the ozone immediately after the addition of the effluent. At the same time, there was a rapid reduction in virus titer. However, after the initial reduction, the virus titer remained unchanged. The degree of virus inactivation was dependent on ozone concentration and on the amount of organic matter in the effluent. With increased ozone concentration and decreased organic matter, a larger percentage of viruses were inactivated. With the second method, ozone was bubbled into filtered sewage containing a virus inoculum. Inactivation of the virus started after a lag period of about 30 s. even before ozone residual in the sewage was detected. Inactivation of 99.999% of the virus was obtained when the ozone residual was about 0.6 mg l⁻¹. In similar experiments performed with buffer instead of sewage, the entire process took place at a much faster rate. When ozone concentrations reached about 1.0 mg l⁻¹. 99.999% of the virus was inactivated. In conclusion, ozone was found to be a very potent viral disinfectant, even in contaminated water.     

Characterization of raw water for the ozone application measuring ozone consumption rate.

This study was conducted to illustrate an ideal method for characterizing natural waters for ozonation processes in drinking water treatment plants. A specific instrument designed with the flow injection analysis (FIA) technique enabled us to measure accurately the ozone decomposition rate, which was found to consist of two stages: the instantaneous ozone consumption stage and the slower ozone decay stage. The ozone consumption rate was measured at the initial and secondary stages by determining certain parameters called the instantaneous ozone demand (ID) and the pseudo first-order decay rate constant (k(c)). Using the OH*-probe, the yield of OH* per consumed ozone was also measured to determine its potential to produce OH* for the oxidation of micropollutants during the ozonation process. The ozone consumption of the ID values was significant in most natural waters, and substantial amounts of OH* were found to generate during the instantaneous ozone consumption stage. This study also investigated the effects of particulates, ozone doses, and sequential ozone injection on ozone decomposition kinetics and OH* formation yield.     

Trends in product information

Within CIB working commission W 74 on information co-ordination a special ‘Product file’ group monitors developments in this latter area. Here, chairman of the group, Anne Volbeda, deputy director of the Bouwcentrum in the Netherlands, comments on the move towards the data base approach, while presenting the results of an updated survey of some data sheet systems available in different countries at the time of the survey.