In this study, long-term rainfall data with irregular spatial distribution in Seoul, Korea, were separated into individual precipitation events by the inter-event time definition of 6 hours. Precipitation washout of $PM_{10}$ and $NO_2$ concentrations in the air considering var...
In this study, long-term rainfall data with irregular spatial distribution in Seoul, Korea, were separated into individual precipitation events by the inter-event time definition of 6 hours. Precipitation washout of $PM_{10}$ and $NO_2$ concentrations in the air considering various complex factors were analyzed quantitatively. Concentrations of $PM_{10}$ and $NO_2$ in the atmosphere were lower under condition of rainfall compared to that of non-precipitation, and a noticeable difference in average $PM_{10}$ concentrations was observed. The reduction of concentrations of $PM_{10}$ and $NO_2$ by rainfall monitored at road-side air monitoring sites was also lower than that of urban air monitoring sites due to continuous pollutant emissions by transportation sources. Meanwhile, a relatively smaller reduction of average $PM_{10}$ concentration in the atmosphere was observed under conditions of light rainfall below 1 mm, presumably because the impact of pollutant emission was higher than that of precipitation scavenging effect, whereas an obvious reduction of pollutants was shown under conditions of rainfall greater than 1 mm. A log-shaped regression equation was most suitable for the expression of pollutant reduction by precipitation amount. In urban areas, a lower correlation between precipitation and reduction of $NO_2$ concentration was also observed due to the mobile emission effect.
In this study, long-term rainfall data with irregular spatial distribution in Seoul, Korea, were separated into individual precipitation events by the inter-event time definition of 6 hours. Precipitation washout of $PM_{10}$ and $NO_2$ concentrations in the air considering various complex factors were analyzed quantitatively. Concentrations of $PM_{10}$ and $NO_2$ in the atmosphere were lower under condition of rainfall compared to that of non-precipitation, and a noticeable difference in average $PM_{10}$ concentrations was observed. The reduction of concentrations of $PM_{10}$ and $NO_2$ by rainfall monitored at road-side air monitoring sites was also lower than that of urban air monitoring sites due to continuous pollutant emissions by transportation sources. Meanwhile, a relatively smaller reduction of average $PM_{10}$ concentration in the atmosphere was observed under conditions of light rainfall below 1 mm, presumably because the impact of pollutant emission was higher than that of precipitation scavenging effect, whereas an obvious reduction of pollutants was shown under conditions of rainfall greater than 1 mm. A log-shaped regression equation was most suitable for the expression of pollutant reduction by precipitation amount. In urban areas, a lower correlation between precipitation and reduction of $NO_2$ concentration was also observed due to the mobile emission effect.
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가설 설정
At roadside sites, as shown in Fig. 10 (b), the NO2 concentration variation under the conditions of non-precipitation were similar with the case of precipitation, just like PM10, because the amount of NO emissions/NO2 production by vehicles was presumably larger than NO2 reduction by photochemical reaction.
제안 방법
In this study, long-term rainfall data with irregular distribution during a 10 year period in Seoul, Korea,were separated into individual precipitation events by IETD estimation. The precipitation washout of PM10 and NO2 concentrations in the air were analyzed quantitatively including consideration of various complicated factors, and the reduction of PM10 and NO2 concentrations by rainfall were also evaluated using regression analysis.
In this study, precipitation data for ten years in Seoul was categorized as independent rainfall events by using the inter-event time definition of 6 hours. The washout effects of precipitation scavenging on the removal of PM10 and NO2 were evaluated quantitatively, and regression analyses of PM10 and NO2 concentration reduction by effect of rainfall was also performed.
In this study, long-term rainfall data with irregular distribution during a 10 year period in Seoul, Korea,were separated into individual precipitation events by IETD estimation. The precipitation washout of PM10 and NO2 concentrations in the air were analyzed quantitatively including consideration of various complicated factors, and the reduction of PM10 and NO2 concentrations by rainfall were also evaluated using regression analysis.
In this study, precipitation data for ten years in Seoul was categorized as independent rainfall events by using the inter-event time definition of 6 hours. The washout effects of precipitation scavenging on the removal of PM10 and NO2 were evaluated quantitatively, and regression analyses of PM10 and NO2 concentration reduction by effect of rainfall was also performed.
대상 데이터
Data of major pollutant concentrations such as PM10 and NO2, and precipitation data were collected from national air monitoring sites and from the Korean Meteorological Administration (KMA, 2012) for the period of 1999 to 2008. PM10 concentration is measured by the β-ray absorption method and NO2 concentration is measured by the chemiluminescent method at the air monitoring sites (MOE, 2012).
So it was determined that spatial averaging would only confuse our analysis. Therefore,for this research, the Seosomun urban air monitoring site and the Seoul-station roadside air monitoring site,which are located in the central part of Seoul and are close to the weather monitoring site about 2 km away from where we obtained the meteorological information, were selected as the target sites. The selected sites are shown in Fig.
이론/모형
In this study, the IETD, which is obtained from serial correlation analysis (Adams et al., 2000), was applied to define a precipitation event. As illustrated in Fig.
성능/효과
1) Calculation of the “time-of-day” hourly average concentration of pollutants during non-precipitation events from the data for ten years, i.e. the 10-year concentration average for 1 am, 2 am, …, 11 pm, 12 am,all 24 excluding hours with precipitation.
concentration reduction by precipitation at urban and road-side air monitoring sites were 1~4 ppb, 2~5 ppb, respectively (Table 2). The NO2 concentrations were reduced under precipitation but the NO2 concentration reduction and rainfall at both site types had extremely low correlation (Fig. 11(c) and (d)).
후속연구
for the 10 year period were separated according to conditions of precipitation and non-precipitation by using the pre-determined IETD. For a more accurate analysis, in general,concentration variation attributable to other parameters such as the emission amount, wind direction, and wind speed, should be excluded. Analyzing the reduction effect on the air pollutants due to precipitation scavenging effect only is also very difficult, as the concentration sometimes increases after the onset of precipitation.
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