Variations Of O3 Concentrations Research Articles

Ozone changes in response to the heavy-duty diesel truck control in the Pearl River Delta

In recent years, restricting heavy-duty diesel trucks from driving within urban areas during the daytime is implemented in major PRD cities (e.g. Guangzhou and Shenzhen). Potential effects of this traffic control policy on spatial and temporal variations of O3 concentrations are examined by CMAQ model system. Temporal profiles of mobile source emissions are modified to reflect the emission characteristics after the control. Our results show that: (1) with the updated mobile emission profile, there is a notable improvement in O3 simulation performance for urban sites, with reductions in both the nighttime O3 overestimation (up to 25 ppb) and the daytime underestimation on O3 peak values (up to 20 ppb); (2) although the control policies are only applied in urban locations, their effects may extend to much larger downwind areas. The results from this study provide basic information that is useful in understanding the effects of mobile control policies on ambient O3 in highly developing regions of China where similar strategies have been widely implemented.

Characteristics of Surface Ozone Concentrations at Stations with Different Backgrounds in the Malaysian Peninsula

One of the main challenges for countries in tropical areas is the high concentration of ozone caused by elevated levels of anthropogenic and natural ozone precursors. In this study, variations in O3 concentrations from urban, suburban and rural regions of the Malaysian Peninsula were investigated using data covering a five-year period (2005–2009) obtained from the Malaysian Department of the Environment. The principal aim of the study is to identify and describe the variations in O3 concentrations recorded at three monitoring stations with different backgrounds, namely Petaling Jaya (S2) (urban), Putrajaya (S1) (suburban) and Jerantut (S3) (rural). The study also investigated the relationship between O3 distribution and its association with nitrogen oxides (NO and NO2) and non-methane hydrocarbon (NMHC). The results showed that the highest O3 concentration was recorded in a suburban area (Putrajaya (S1) with an average daily maximum value of 60 ± 20 ppbv). The O3 concentration was influenced by the characteristics of nitrogen oxides, particularly the titration of NO. The surface O3 level was found to be influenced by solar radiation and wind direction from the busy areas, most notably Kuala Lumpur's city centre. This study suggests that the emission of O3 precursors, particularly NOx from motor vehicles, needs to be regulated to reduce the incidence of high O3 levels in Malaysia.

Assessment of Variations of O3 Concentrations in Kopački Rit Nature Park, Eastern Croatia

Result of the first ozone monitoring in ambient air Nature Park of Kopacki Rit (Eastern Croatia) are reported for the growth season in 2008. The measured hourly concentrations of ozone in the air do not exceed the limit value of 110 mu g m(-3) statutory regulation by Croatian legalization for the protection of human health. There were only 13 days exceeding of the target value of 120 mu g m(-3) (8-h averages) as established in the European Union guidelines on ozone pollution in ambient air. In contrast to the measured AOT40 whose value does not exceed the critical level of 18 000 (mu g m(-3)).h for vegetation injury, an estimated AOT40 value was somewhat higher. The relationships between O-3 and meteorological variables were investigated by a principal component analysis (PCA). Fourier analysis methods applied to ozone concentrations data showed that the most important variations in the O-3 data are represented by usual daily cycles.

Analysis of Diurnal and Seasonal Behavior of Surface Ozone and Its Precursors (NOx) at a Semi-Arid Rural Site in Southern India

Surface measurements of O3, NO, NO2 and NOx have been made over a semi-arid rural site, Anantapur (14.62°N; 77.65°E; 331 m asl) in southern India, during January-December 2010. The highest monthly mean O3 concentration was observed in April (56.1 ± 9.9 ppbv) and the lowest in August (28.5 ± 7.4), with an annual mean of 40.7 ± 8.7 ppbv for the observation period. Seasonal variations in O3 concentrations were the highest during the summer (70.2 ± 6.9 ppbv), and lowest during the monsoon season (20.0 ± 4.7 ppbv), with an annual mean of 40.7 ± 8.7 ppbv. In contrast, higher NOx values appeared in the winter (12.8 ± 0.8 ppbv) followed by the summer season (10.9 ± 0.7 ppbv), while lower values appeared in the monsoon season (3.7 ± 0.5 ppbv). The results for O3, NO and NO2 indicate that the level of oxidant concentration ([OX] = NO2 + O3) at a given location is the sum of NOx-independent “regional contribution” (background level of O3) and linearly NOx-dependent “local contribution”. The O3 concentration shows a significant positive correlation with temperature, and a negative correlation with both wind speed and relative humidity. In contrast, NOx have a significant positive correlation with humidity and wind speed, and negative correlation with temperature. The slope between [BC] and [O3] suggests that every 1 μg/m3 increase in black carbon aerosol mass concentration causes a reduction of 4.7 μg/m3 in the surface ozone concentration. A comparative study using satellite data shows that annual mean values of tropospheric ozone contributes 12% of total ozone, while near surface ozone contributes 82% of tropospheric ozone. The monthly mean variation of tropospheric ozone is similar to that tropospheric NO2, with a correlation coefficient of +0.80.

Relationships among the springtime ground–level NOx, O3 and NO3 in the vicinity of highways in the US East Coast

To characterize the relationships among the springtime NOx (NO + NO2), O3 and NO3 (defined as the combination of gaseous nitric acid, HNO3, and aerosol nitrate, NO3–) concentrations in the ambient air of the vicinity of highways, an intensive sampling was carried out in spring 2007 at Lyndhurst, NJ in the U.S. East Coast. Ambient concentrations of O3 and NOx were measured by O3 and NOx analyzers, while NO3 was collected using a ChemComb cartridge and determined by ion chromatography. Significant variations in O3 concentrations were observed diurnally as well as between weekdays and weekends, with higher concentrations occurring during the daytime and on weekends. The 24–h diurnal variations of O3 and NOx could be divided into four periods: (1) morning NOx peak, (2) mid–day O3 formation, (3) afternoon NOx accumulation and (4) nighttime balancing. Daily averaged relative humidity and wind speed were the two weather parameters affecting O3 levels more than other averaged parameters, and daily maximum temperature was positively correlated to the maximum O3. Via photochemical reactions and emission– diffusion balance, NOx showed primarily negative influences on the daily O3 variations with decayed exponential correlations, in particular during nighttime and weekdays, indicating a possible VOC–sensitive characteristic of the study area. A negative correlation between NO3– and O3 concentrations was found while no obvious influence of HNO3 on O3 was observed. Results by a multi–regression model involving three parameters (NO2/OX ratio, NO2 and HNO3) reveal that the NO2/OX ratio is an important parameter controlling the ground O3 level in the study area.

Analysis of the Relationship between O3, NO and NO2 in Tianjin, China

The continuous measurement of nitric oxide (NO), nitrogen dioxide (NO2), nitrogen oxides (NO(subscript x)) and ozone (O3) was conducted in Tianjin from September 8 to October 15, 2006. The data were used to investigate the relationship between the O3 distribution and its association with ambient concentrations of NO, NO2 and NO(subscript x) (NO and NO2). The measured concentrations of the pollutants in the study area varied as a function of time, while peaks in NO, NO2 and O3 all occurred in succession in the daytime. The diurnal cycle of ground-level ozone concentration showed a mid-day peak and lower nighttime concentrations. Furthermore, an inverse relationship was found between O3 NO, NO2 and NO(subscript x). In addition, a linear relationship between NO2 and NO(subscript x), as well as NO and NO(subscript x), and a polynomial relationship between O3 and NO2/NO was found. The variation in the level of oxidant (O3 and NO2) with NO2 was also obtained. It can be seen that OX concentration at a given location is made up of two parts: one independent and the other dependent on NO2 concentration. The independent part can be considered as a regional contribution and is about 20 ppb in Tianjin. An obvious difference in NO, NO(subscript x) and O3 concentrations between weekdays and weekends was also found, but this difference did not appear in NO2. Lastly, the diurnal variation of O3 concentration under different meteorological conditions was demonstrated and analyzed.

Adaptive Grid Modeling with Direct Sensitivity Method for Predicting the Air Quality Impacts of Biomass Burning

The objective of this study was to improve the ability to model the air quality impacts of biomass burning on the surrounding environment. The focus is on prescribed burning emissions from a military reservation, Fort Benning in Georgia, and their impact on local and regional air quality. The approach taken in this study is to utilize two new techniques recently developed: (1) adaptive grid modeling and (2) direct sensitivity analysis. An advanced air quality model was equipped with these techniques, and regional-scale air quality simulations were conducted. Grid adaptation reduces the grid sizes in areas that have rapid changes in concentration gradients; consequently, the results are much more accurate than those of traditional static grid models. Direct sensitivity analysis calculates the rate of change of concentrations with respect to emissions. The adaptive grid simulation estimated large variations in O3 concentrations within 4 × 4-km2 cells for which the static grid estimates a single average concentration. The differences between adaptive average and static grid values of O3 sensitivities were more pronounced. The sensitivity of O3 to fire is difficult to estimate using the brute-force method with coarse scale (4 × 4 km2) static grid models.

Carbonyls and non-methane hydrocarbons at a rural mountain site in northeastern United States

Measurements of carbonyls and C2–C6 non-methane hydrocarbons (NMHCs) were made in ambient air at a rural site at the summit of Whiteface Mountain (WFM) in New York State. Alkanes dominated in the samples, with ethane and propane making up about 55% of the total on a carbon-atom basis. Ethane, the longest-lived of the NMHCs, showed a mixing ratio in the range of 0.86–2.1ppbv. Photochemical ageing analysis indicated an anthropogenic influence on the NMHC levels. The photochemical reactivity of the hydrocarbons, calculated in terms of propylene-equivalent concentration, was dominated by alkenes (propene and ethene), which accounted for 74% of the total NMHC sum. Air mass back-trajectories have been used to investigate the origin of the observed NMHCs and carbonyls. Higher concentrations were found when air masses arrived from the midwestern US corridor. Acetone was the most abundant species, comprising from 31% to 53% of the total detected carbonyls, followed by MEK (15–53%), HCHO (7–39%), and CH3CHO (7–19%). Average concentrations were determined to be 1.61ppbv for CH3C(O)CH3, 1.40ppbv for MEK, 1.16ppbv for HCHO, and 0.49ppbv for CH3CHO. The variations in carbonyl concentrations were observed to follow patterns similar to variations in O3 concentrations, typical of secondary products. Correlations and statistical analysis of the carbonyls and NMHCs were performed, and showed that most of the compounds derived from mixing and photochemical transformation of long-range transported pollutants from the major source areas. Ranking of the carbonyls with respect to removal of the OH radical showed HCHO to be the most important species, followed by CH3CHO, MEK, and CH3C(O)CH3.

Production of ozone in the Chamonix Valley (France)

In the framework of the Pollution of Alpine Valleys (POVA) programme, a numerical investigation aims to better understand how a reduction of traffic emissions can affect air quality in the Chamonix Valley (France). The MM5 model coupled with the Chemistry Transport Model (CTM) TAPOM using a 1-km cell grid for the period 5–12 July 2003 showed that the ozone formation in the Chamonix Valley was strongly NOx-saturated. A comparison with physical and chemical measurements (tethered balloon, UHF radar, monitoring data) prove the temperature profile and the up- and downhill thermally driven winds to be reasonably well described by MM5. Moreover spatial and temporal variation of O3 concentration is well described by TAPOM. Ozone production within the valley is estimated to 20 to 30 µg/m³ and 10 µg/m³ are locally produced from precursors emitted by international traffic through the tunnel.

An analysis of pesticide impact on air quality, especially surface ozone

The present study aims at shedding some light on the serious effect of insecure pesticides to the surface ozone as a secondary pollutant resulting from some photochemical reactions during the sunny days. The temporal variation in O3 concentrations due to pesticide spray, the corresponding temperature and relative humidity have been monitored and discussed. The air quality index (AQI) for the maximum concentrations of O3 within each day of study has also been deduced. The obtained results illustrated that O3 concentrations had been increased after pesticide spray with different values from hour to hour and then began to decay after one day or more according to its concentrations. The second day had the highest concentrations of the O3 including the maximum concentration, which was recorded at hour 14 local time. Furthermore, most of AQI values were restricted between harmful and very harmful index during the second days and only the third day of the first experiment. Moreover, temperature and relative humidity have significantly influenced ozone concentrations with positive and negative correlation coefficients, respectively.

Nature of variation of Antarctic O3 depletion and its correlation with solar UV radiation

The purpose of this paper is to study the nature of variation of O3 concentration of Antarctic Survey Stations and its correlation with solar ultraviolet radiation. Solar UV data for the period November 1978 to October 1984 are taken from Solar Geophysical Data Book. In absence of solar UV data for long period, a calibration curve between solar UV radiation and solar flare number (S.F.NO.) is drawn. (A straight line is obtained and correlation coefficient between two variables is 80%). The equation of straight line from least square principle becomes, UV flux = 0.2672 + 2.7578 × 10−5 × S.F.NO. From this equation UV flux values for long period are calculated from known values of solar flare numbers. O3 concentration of two Antarctic Survey Stations, Halley Bay (76‡ S, 27‡ W) and McMurdo (78‡ S, 166‡ E) are considered for analysis and following important results are obtained: (i) Yearly variations of O3 concentrations and UV radiations are mainly controlled by their October concentrations. (ii) Correlation coefficient between O3 concentration and UV radiation is 62% for the month of October. For the other months it is poor. (iii) It is concluded that dramatic decrease of O3 concentration at Antarctica is independent of solar UV radiation and chemical processes are responsible for special depletion of O3.