Long-term changes in the tropospheric column ozone from the ozone soundings over Europe

The tropospheric column of ozone is analyzed from the measurements of the vertical profile of ozone by balloon-born ozonesondes. The data base includes ∼16,000 ozone profiles collected above six European stations—three of them have begun the ozonesoundings since 1970. We present a trend analysis (with data up to 2005) focusing on detection of the long-term tropospheric ozone variability over the European network. The ozone time series have been examined separately for each station and season (DJF, MAM, JJA, SON) using a flexible trend model. A trend component of the model is taken as a smooth curve without a priori defined shape. A large increase in the European tropospheric ozone since the beginning of the 1970s (net change of ∼10% in summers and ∼30% in winters) and a kind of stabilization in the early 1990s have been corroborated by the study. This pattern comes from the most extensive data set of ozonesoundings over Hohenpeissenberg and Payern. The decadal differences in the trend pattern between these and other European stations are disclosed. The results of a stepwise regression model using various characteristics of the ozone and temperature profiles as explanatory variables for the tropospheric column ozone (TCO₃) variations show that the ozone changes may be reconstructed using the ozone mixing ratio at 500 hPa, the thermal tropopause (TT) height, and the difference between ozonepause and TT heights. It appears that the last two factors induce 20–30% of the net TCO₃ change over Hohenpeissenberg in the 1970–2004 period.     

Ground-level ozone in the Pearl River Delta region: Analysis of data from a recently established regional air quality monitoring network

The ambient air quality monitoring data of 2006 and 2007 from a recently established Pearl River Delta (PRD) regional air quality monitoring network are analyzed to investigate the characteristics of ground-level ozone in the region. Four sites covering urban, suburban, rural and coastal areas are selected as representatives for detailed analysis in this paper. The results show that there are distinct seasonal and diurnal cycles in ground-level ozone across the PRD region. Low ozone concentrations are generally observed in summer, while high O₃ levels are typically found in autumn. The O₃ diurnal variations in the urban areas are larger than those at the rural sites. The O₃ concentrations showed no statistically significant difference between weekend and weekdays in contrast to the findings in many other urban areas in the world. The average ozone concentrations are lower in urban areas compared to the sites outside urban centers. Back trajectories are used to show the major air-mass transport patterns and to examine the changes in ozone from the respective upwind sites to a site in the center of the PRD (Wanqingsha). The results show higher average ozone concentrations at the upwind sites in the continental and coastal air masses, but higher 1 h-max O₃ concentrations (by 8–16 ppbv) at the center PRD site under each of air-mass category, suggesting that the ozone pollution in the PRD region exhibits both regional and super-regional characteristics.     

An ozone budget for the UK: using measurements from the national ozone monitoring network; measured and modelled meteorological data,and a 'big-leaf' resistance analogy model of dry deposition

Data from the UK national air-quality monitoring network are used to calculate an annual mass budget for ozone (O3) production and loss in the UK boundary layer during 1996. Monthly losses by dry deposition are quantified from 1 km x 1 km scale maps of O(3) concentration and O(3) deposition velocities based on a big-leaf resistance analogy. The quantity of O(3) deposition varies from approximately 50 Gg-O(3) month(-1) in the winter to over 200 Gg-O(3) month(-1) in the summer when vegetation is actively absorbing O(3). The net O(3) production or loss in the UK boundary layer is found by selecting days when the UK is receiving "clean" Atlantic air from the SW to NW. In these conditions, the difference in O(3) concentration observed at Mace Head and a rural site on the east coast of the UK indicates the net O(3) production or loss within the UK boundary layer. A simple box model is then used to convert the concentration difference into a mass. The final budget shows that for most of the year the UK is a net sink for O(3) (-25 to -800 Gg-O(3) month(-1)) with production only exceeding losses in the photochemically active summer months (+45 Gg-O(3) month(-1)).     

Potential interference bias in ozone standard compliance monitoring

The U.S. Environmental Protection Agency has established a federal reference method (FRM) for ozone (O3) and allowed for designation of federal equivalent methods (FEMs). However, the ethylene-chemiluminescence FRM for O3 has been replaced by the UV photometric FEM by most state and local monitoring agencies because of its relative ease of operation. Accumulating evidence indicates that the FEM is prone to bias under the hot, humid, and stagnant conditions conducive to high O3 formation. This bias may lead to overreporting hourly O3 concentrations by as much as 20-40 ppb. Measurement bias is caused by contamination of the O3 scrubber, a problem that is not detected by dry air calibration. An adequate wet test has not been codified, although a procedure has been proposed for agency consideration. This paper includes documentation of laboratory tests quantifying specific interferant responses, collocated ambient FRM/FEM monitoring results, and smog chamber comparisons of the FRM and FEMs with alternative scrubber designs. As the numbers of reports on monitor interferences have grown, interested parties have called for agency recognition and correction of these biases.     

臭氧预处理—厌氧消化工艺促进剩余污泥减量化的研究

主要研究了臭氧氧化对剩余污泥的破解效果及污泥厌氧消化效率的影响.结果表明,随着臭氧投加量的增加,悬浮物(SS)、可挥发性悬浮物(VSS)逐步减少,而剩余污泥上清液中的溶解性COD(SCOD)、总有机碳(TOC)、蛋白质和多糖则明显增加.经臭氧预处理(臭氧投加量为0.050 g(以每克SS计))后,剩余污泥中温(35℃)厌氧消化效率明显提高,经65d稳定运行后,总挥发性固体(TVS)去除率为67.58％,与未经臭氧预处理的剩余污泥相比提高50.61％;甲烷平均产率为0.303 L(以每克TVS计),与未经臭氧预处理的剩余污泥相比提高54.59％.可见,臭氧预处理能有效促进污泥厌氧消化,从而达到污泥减量的目的.     

Air quality modeling and decisions for ozone reduction strategies

Despite the widespread application of photochemical air quality models (AQMs) in U.S. state implementation planning (SIP) for attainment of the ambient ozone standard, documentation for the reliability of projections has remained highly subjective. An "idealized" evaluation framework is proposed that provides a means for assessing reliability. Applied to 18 cases of regulatory modeling in the early 1990s in North America, a comparative review of these applications is reported. The intercomparisons suggest that more than two thirds of these AQM applications suffered from having inadequate air quality and meteorological databases. Emissions representations often were unreliable; uncertainties were too high. More than two thirds of the performance evaluation efforts were judged to be substandard compared with idealized goals. Meteorological conditions chosen according regulatory guidelines were limited to one or two cases and tended to be similar, thus limiting the extent to which public policy makers could be confident that the emission controls adopted would yield attainment for a broad range of adverse atmospheric conditions. More than half of the studies reviewed did not give sufficient attention to addressing the potential for compensating errors. Corroborative analyses were conducted in only one of the 18 studies reviewed. Insufficient attention was given to the estimation of model and/or input database errors, uncertainties, or variability in all of the cases examined. However, recent SIP and policy-related regional modeling provides evidence of substantial improvements in the underlying science and available modeling systems used for regulatory decision making. Nevertheless, the availability of suitable databases to support increasingly sophisticated modeling continues to be a concern for many locations. Thus, AQM results may still be subject to significant uncertainties. The evaluative process used here provides a framework for modelers and public policy makers to assess the adequacy of contemporary and future modeling work.     

Background ozone monitoring and phytodetection in the greater rural area of Corinth--Greece

Natural background ozone levels were monitored in three places within the greater rural area of Corinth, namely Bogdani Hill, Astronomical Observatory of Krionerion, and Kiato, and compared with ambient ozone monitored in the metropolitan area of Athens. Measurements were made sequentially, for a few weeks at each place, during the summer of 2000. In addition, ozone phytodetection, using tobacco (Nicotiana tabacum L.) plants of the Bel-W3 and Zichnomirodata varieties, was conducted in 12 places (the above included). Moreover, stomatal conductance was measured in the Bel-W3 plants, as well as in leaves of cultivated grape-vines (Vitis vinifera L.) and in needles of Aleppo pine (Pinus halepensis Mill.) trees and compared with the diurnal pattern of ozone concentrations.The 24 and 12 (08:00-20:00) hourly averages of ozone concentrations were high in Athens (37; 51 ppb), at Bogdani Hill (53; 56 ppb) and at the Astronomical Observatory (56; 55 ppb), but relatively low in Kiato (30; 34 ppb). Furthermore, the average daily AOT40 (accumulated exposure over 40 ppb for the daylight hours) (ppbh) was 193 in Athens, 212 at Bogdani Hill, 192 at the Astronomical Observatory and 47 in Kiato. Ozone concentrations exhibited the usual diurnal pattern in Athens (altitude 50 m), where they were maximum during midday and early afternoon hours, as well as at Bogdani Hill (300 m) and in Kiato (5 m) where, however, they were maximal 1-3 h later. At the Astronomical Observatory (altitude 920 m) ozone remained constant during both daylight and night hours. The differences in diurnal patterns are consistent with those in places of different elevation, reported elsewhere.The Bel-W3 plants were injured at all 12 places; Zichnomirodata plants exhibited lower injury and only in some of the places; probable ozone symptoms were also observed on vine plants and pine trees. The greatest injury was observed at the high altitude places of Astronomical Observatory and Mougostos. Stomatal conductance, in all three species, peaked during morning and early midday hours when ozone levels were higher in the high altitude, and lower in the low altitude, places.     

污泥臭氧减量化过程中氮溶出物的规律

以污泥臭氧减量化过程中含氮物质的转变为研究核心,分析了减量过程中不同形态氮溶出物随臭氧投量的变化,并利用线性回归方程归纳出污泥溶解过程中各形态含氮物质的溶出规律。结果表明：当臭氧投量在0.15 g O3·（g TSS）-1时,TN的增长速率最高,增幅达437.44%,此时MLSS减少了41.28%,可将0.15 g O3·（g TSS）-1视为臭氧最佳投量;XPS图谱显示,溶出的NH4+-N、NO3--N主要由污泥絮体中铵态氮和硝态氮的释放所致,而凯氏氮主要来源于胞内蛋白质-N（有机态凯氏氮）的溶出,在臭氧投量为0.30 g O3·（g TSS）-1时,凯氏氮占溶出TN的93.46%;最终建立TN关于ΔMLSS、臭氧投量D和臭氧浓度C的数学模型为TN=ΔMLSS·（0.000 96C+0.011 2）=e3.992·D0.774·C1.466·（0.000 96C+0.011 2）,该模型应用范围为MLSS=4 000~5 000 mg·L-1,20 mg·L-1C-1,0.02 g O3·（g TSS）-1D3·（g TSS）-1。     

Comparison between weekend and weekday ozone concentration in large cities in France

This paper examines ozone data from five large French cities (Marseilles, Lyon, Paris, Strasbourg and Toulouse) in spring and summer over a three-year period to study the possible influence of local primary pollutant emissions. In these cities the level of traffic emission varies according to the day of the week. There is a decrease of about 25% in traffic emissions between non-consecutive Tuesdays and Sundays. Traffic emissions on Fridays are about 40% more than on non-consecutive Sundays whereas they seem to be similar for non-consecutive Tuesdays and Thursdays. Despite this variation in traffic emissions between Fridays and Sundays, 85% of daily ozone maxima are identical for all days compared; in 15% of cases, percentiles of daily ozone maxima vary by about 20% at the most. This difference is observed for the highest values of daily ozone maxima that we can find both in rural and urban sites. Marseilles is the most pollution-sensitive city; every site of this area is concerned, which gives a regional origin to ozone variability. In the less-populated Toulouse area, differences between ozone on Fridays and Sundays are less significant. Our results show the importance of advection phenomena of ozone. It calls into question strategies of local reductions in traffic during ozone episodes.     

An experimental study of the horizontal and vertical distribution of ozone over Athens

In this study, we present measurements of ozone (O₃) concentrations both on the surface and aloft, taken at sites appropriately located to give information about the effect of the local flows, such as the sea breeze circulation, on the air quality of Athens. Profiles of O₃ and other meteorological parameters of the atmospheric boundary layer were obtained at a location in the center of Athens. Surface measurements of O₃ were conducted in a number of other locations which included the shoreline and an island. The measurements confirmed well known models for the effect of sea breeze on photochemical pollutants and the diurnal variation of O₃ in the evolving atmospheric boundary layer and showed that pollutants released in the evening and early morning hours are advected offshore where they generate O₃ which in turn is advected back to the city by the sea breeze. They also showed that Athens pollutants are found in considerable concentrations in Aegina and outside the main basin to the north. The results of this study demonstrate the need to take into account advection patterns in any attempt to formulate pollution abatement strategies for sites with strong local circulations such as the Athens basin.     

Annual and seasonal trends of ambient ozone concentration and its impact on forest vegetation in Mercantour National Park (South-eastern France) over the 2000-2008 period

In the South-Eastern French Mediterranean region, high ozone concentrations were measured since many years and specific symptoms like chlorotic mottles were detected on Arolla pines. We presented results for the 2000-2008 period concerning the trend analysis for ambient ozone concentrations and related forest damages, with the Mann and seasonal Kendall tests. Ozone precursor’s emissions from Europe have been reduced over the last 20 years. Decreases in annual averages, median, 25th and 98th percentiles and maxima values were found. The seasonal trend analysis for the high-lying stations showed a decreasing trend for the warm season, when main ozone production is the photochemistry, and an increase for the cold period, caused by a reduced ozone titration. Statistics on Arolla Pine reveal strong correlations between mottling intensity and the high ozone concentrations. Finally, decreases for the ozone concentrations, and associated statistics, AOT40 values and for the mottling intensity on conifers needles were observed.     

Validation of a hybrid forecasting system for the ozone concentrations over the Paris area

A simplified hybrid statistical-deterministic chemistry-transport model, is used in real time for the prediction of ozone in the area of Paris during Summer 1999. We present here a statistical validation of this experiment. We distinguish the forecasts in the urban area from forecasts in the pollution plume downwind of the city. The validation of model forecasts, up to 3 days ahead, is performed against ground based observations within and up to 50 km outside of Paris. In the urban area, ozone levels are fairly well forecast, with correlation coefficients between forecast and observations ranging between 0.7 and 0.8 and root mean square errors in the range 15–20 μg m⁻³ at short lead times. While the bias of urban forecast is very low, the largest peaks are somehow underestimated. The ozone plume amplitude is generally well reproduced, even at long lead times (root mean square errors of about 20–30 μg m⁻³), while the direction of the plume is only captured at short lead times (about 70% of the time). The model has difficulties in forecasting the direction of the plume under stagnant weather conditions. We estimate the model ability to forecast concentrations above 180 μg m⁻³, which are of practical relevance to air quality managers. It is found that about 60% of these events are well forecast, even at long lead times, while the exact monitoring station where the exceedance is observed can only be forecast at short lead times. Finally, we found that about half of the forecast error is due to the error in the estimation of the boundary conditions, which are forecast by a simple linear regression model here.     

Diurnal variability of total ozone column over Madrid (Spain)

In recent years, research on ozone variability has mainly focused on the analysis of its trend. Additionally some studies have analyzed the annual, seasonal and day-to-day ozone variations. However, intra-diurnal total ozone variations are notably less explored. Thus, the main objective of this paper is to analyze the diurnal variability of total ozone column (TOC) as recorded by a Brewer spectrophotometer in Madrid (Spain). The results show that about 90% of days present non-negligible diurnal variability, indicating that, in general, it should not be assumed that TOC remains constant throughout a particular day in urban areas. In addition, this variability has a notable seasonal behavior which should be considered (the spring and summer months show higher diurnal TOC variations than autumn and winter months). This pattern is likely caused by the diurnal photochemical processes in the lower troposphere related to the formation of tropospheric ozone near the earth’s surface at populated urban locations. Thus, these diurnal fluctuations in tropospheric ozone could explain part of diurnal TOC variations (between 20% and 70% depending on the mixing layer height).     

Detecting plant effects is necessary to give biological significance to ambient ozone monitoring data and predictive ozone standards

The use of mechanical monitors and passive samplers has made it possible to assess concentrations of ozone over wide areas and to develop air quality standards, like AOT40 and SUM60. Monitored ozone data and AOT40 and SUM60 are also used to predict ozone injury on local and regional scales. The data and the standards do not include or account for environmental and biological variables that affect ozone uptake and plant injury. Ground proofing via vegetation surveys must be done to verify and validate plant injury predictions. If this is not done, then the standards have no biological significance and are only exercises in air quality assessment.     

Performance evaluation of a tailor-made passive sampler for monitoring of tropospheric ozone

Introduction

This study presents the performance evaluation of a tailor-made passive sampler developed for the monitoring of tropospheric ozone.

Methods

The performance of the passive sampler was tested in the field conditions in terms of accuracy, precision, blank values, detection limit, effects of some parameters such as sampling site characteristics and sampling period on the field blanks, self-consistency, experimental and theoretical uptake rates, shelf life and comparison with commercial passive samplers.

Results

There was an agreement (R ²?=?0.84) between the responses of passive sampler and the continuous automatic analyser. The accuracy of the sampler, expressed as percent relative error, was obtained lower than 15%. Method precision in terms of coefficient of variance for three simultaneously applied passive samplers was 12%. Sampler detection limit was 2.42???g?m^?3 for an exposure period of 1?week, and the sampler can be stored safely for a period of up to 8?weeks before exposure. Satisfactory self-consistency results showed that extended periods gave the same integrated response as a series of short-term samplers run side by side. The uptake rate of ozone was found to be 10.21?mL?min^?1 in a very good agreement with the theoretical uptake rate (10.32?mL?min^?1). The results of the comparison study conducted against a commercially available diffusion tube (Gradko diffusion tube) showed a good linear relationship (R ²?=?0.93) between two passive samplers.

Conclusions

The sampler seems suitable to be used in large-scale measurements of ozone where no data are available or the number of existing automated monitors is not sufficient.     

Optimal deployment of emissions reduction technologies for construction equipment

The objective of this research was to develop a multiobjective optimization model to deploy emissions reduction technologies for nonroad construction equipment to reduce emissions in a cost-effective and optimal manner. Given a fleet of construction equipment emitting different pollutants in the nonattainment (NA) and near -nonattainment (NNA) counties of a state and a set of emissions reduction technologies available for installation on equipment to control pollution/emissions, the model assists in determining the mix of technologies to be deployed so that maximum emissions reduction and fuel savings are achieved within a given budget. Three technologies considered for emissions reduction were designated as X, Y, and Z to keep the model formulation general so that it can be applied for any other set of technologies. Two alternative methods of deploying these technologies on a fleet of equipment were investigated with the methods differing in the technology deployment preference in the NA and NNA counties. The model having a weighted objective function containing emissions reduction benefits and fuel-saving benefits was programmed with C++ and ILOG-CPLEX. For demonstration purposes, the model was applied for a selected construction equipment fleet owned by the Texas Department of Transportation, located in NA and NNA counties of Texas, assuming the three emissions reduction technologies X, Y, and Z to represent, respectively, hydrogen enrichment, selective catalytic reduction, and fuel additive technologies. Model solutions were obtained for varying budget amounts to test the sensitivity of emissions reductions and fuel-savings benefits with increasing the budget. Different mixes of technologies producing maximum oxides of nitrogen (NO(x)) reductions and total combined benefits (emissions reductions plus fuel savings) were indicated at different budget ranges. The initial steep portion of the plots for NO(x) reductions and total combined benefits against budgets for different combinations of emissions reduction technologies indicated a high benefit-cost ratio at lower budget amounts. The rate of NO(x) reductions and the increase of combined benefits decreased with increasing the budget, and with the budget exceeding certain limits neither further NO(x) reductions nor increased combined benefits were observed. Finally, the Pareto front obtained would enable the decision-maker to achieve a noninferior optimal combination of total NO(x) reductions and fuel-savings benefits for a given budget.     

氧化铈/活性炭催化臭氧氧化技术去除水中邻苯二甲酸二甲酯

用浸渍法在活性炭(AC)上负载氧化铈(CeO2)制备催化刺CeO2/AC催化臭氧氧化去除邻苯二甲酸二甲酯(DMP),考察了臭氧投加量,DMP初始浓度和溶液初始pH的影响.结果表明,CeO2/AC催化臭氧氧化去除DMP的最佳臭氧投加量为50mg/h,DMP初始浓度和溶液初始pH对CeO2/AC催化臭氧氧化DMP过程都有一定的影响.在DMP初始质量浓度为30 mg/L、溶液初始pH为5、臭氧投加量为50 mg/h、反应60 min时,CeO2/AC的加入(1.5g/L)有利于催化臭氧氧化DMP过程中总有机碳(TOC)的去除,TOC去除率由AC催化臭氧氧化的48%提高到68%.而单独臭氧氧化过程中的TOC去除率仅22%;且单独臭氧氧化与AC、CeO2/AC催化臭氧氧化DMP的矿化过程均符合二级反应动力学方程,CeO2/AC催化臭氧氧化DMP时TOC降解的二级反应动力学常数为0.0015L/(mg·min),分别是AC催化臭氧氧化的2.5倍和单独臭氧氧化的7.5倍.     

A numerical study of an autumn high ozone episode over southwestern Taiwan

Elevated ozone concentration is one of the current major environmental concerns in Taiwan. The spatial distribution and seasonal variations of ground level ozone over Taiwan are investigated by using air quality network stations of Taiwan Environmental Protection Administration (TEPA). Data shows that high ozone episodes frequently occur over southwest Taiwan during autumn. In this season, shallow northeasterly winds prevail after frontal passage and are diverted by the Central Mountain Range (CMR) because of its mean altitude of about 2.5 km. The windward side in northern Taiwan is usually associated with cloudy days, whereas sunny days with weak wind speeds usually occur on the lee side of the CMR over southwest Taiwan due to topographical blocking. Numerical results indicate that anthropogenic emissions from the north of Kaohsiung could contribute as much as 41% of ozone for the Kaohsiung metropolitan area and 24% for the inland rural Pingtung area during the northerly flow. It is concluded that the contribution of the emissions from the north of Kaohsiung is significant and cannot be ignored. The northerly air masses, which flows over the western plain during daytime, picks up ozone and its precursors which are transported to southwestern Taiwan. After a sea breeze develops, strong onshore flow transports significant amounts of ozone and precursors to the inland rural areas resulting in the high ozone episodes that frequently occur over southwestern Taiwan during the autumn season.     

Characteristics of springtime profiles and sources of ozone in the low troposphere over northern Taiwan

To quantify the possible sources of the high ambient ozone concentration in the low troposphere over Taiwan, ozone sounding data from a two-year intensive field measurement program conducted in April and early May of 2004 and 2005 in northern Taiwan has been examined. We found that the vertical ozone distributions and occurrence of enhanced ozone in the lower troposphere (below 6 km) mainly resulted from (1)Type NE: the long-range transport of ozone controlled by the prevailing northeasterly winds below 2 km, (2)Type LO: the local photochemical ozone production process, and (3)Type SW: the strong southwest/westerly winds aloft (2–6 km). In the boundary layer (BL), where Asian continental outflow prevails, the average profile for type NE is characterized by a peak ozone concentration of nearly 65 ppb at about 1500 m altitude. For type LO, high ozone concentration with an average ozone concentration greater than 80 ppb was also found in the BL in the case of stagnant atmospheric and sunny weather conditions dominated. For type SW, significant ozone enhancement with average ozone concentration of 70–85 ppb was found at around 4 km altitude. It is about 10 ppb greater than that of the types NE and LO at the same troposphere layer owing to the contribution of the biomass burning over Indochina. Due to Taiwan's unique geographic location, the complex interaction of these ozone features in the BL and aloft, especially features associated with northeasterly and south/southwesterly winds, have resulted in complex characteristics of ozone distributions in the lower troposphere over northern Taiwan.