Abstract
The Dallas-Fort Worth (DFW) area that experiences high temperature and intense solar radiation falls into the moderate nonattainment classification. The variation in meteorological parameters plays an important role in ambient ozone levels variation. Meteorological influences need to be decoupled from ozone data for long-term trend analysis. Temporal separation of maximum daily average 8-h ozone (MDA8 ozone), maximum daily temperature (TMAX), daily average solar radiation (DASR), and daily average wind speed (DAWS) were conducted using Kolmogorov-Zurbenko (KZ) filter for ozone records at Keller (C17), Arlington (C61), Red Bird (C402) monitoring stations in the DFW area from 2003 to 2017. Temporal separation, regression analysis, and meteorological detrending were performed. The long-term component had a clear and stable trend. The contribution of the long-term component to total variation was negligible, which is less than 2%. This is due to the removal of the data noise from the original time series data. The seasonal component had a major contribution (55% to 72%) in the total variation of the maximum temperature and solar radiation. However, the short-term component was dominant in the total variation of the MDA8 ozone (41–54%) and wind speed (68–79%). Regression analysis showed the baseline component bears the highest correlation than the short-term and raw. Solar radiation had the highest correlation to the MDA8 ozone, followed by temperature data in all three stations. Meteorological detrending showed the detrended long-term ozone had an increasing trend. The increasing trend was significant at C402 with a trend of 0.19 ± 0.006 ppb/y (0.398 R2), whereas slight increasing trends were found at C17 (0.072 ± 0.006 (0.107 R2)) and at C61 (0.019 ± 0.007 (0.005 R2)). The increasing trend of long-term components of MDA8 ozone was justified by the increasing level of NOx and VOCs from the mobile sources in the DFW area.
Highlights
Air pollution has significantly increased in the last 50 years, which poses a serious threat to human health
The MDA8 ozone time series, daily maximum temperature, daily average solar radiation, and daily average wind speed data were considered for the study
The overall linear trend analysis was done for each site, MDA8 ozone data
Summary
Air pollution has significantly increased in the last 50 years, which poses a serious threat to human health. The concern of pollutants (sulfur dioxide) emitted due to fossil fuel consumption has been shifted to new pollutants (Nitrogen Oxides (NOx), Volatile Organic. Compounds (VOCs), and ozone due to the increased use of vehicles in urban areas [1]. Ozone is formed secondarily from the reaction between NOx and VOCs in the presence of sunlight. As ozone formation occurs during day-time, mostly in summer, the ozone problems are more likely short-term and seasonal. Higher levels of ozone have been detected in the tropospheric layer of some large. A total of 196 counties in the U.S are in the Non-Attainment Area List of USEPA according to the 8-H Ozone (2015) National Ambient Air Quality Standards (NAAQS) [2]
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