Spatial and Temporal Variations of PM2.5 and Its Relation to Meteorological Factors in the Urban Area of Nanjing, China

Abstract

The serious air pollution problem has aroused widespread public concerns in China. Nanjing city, as one of the famous cities of China, is faced with the same situation. This research aims to investigate spatial and temporal distribution characteristics of fine particulate matter (PM2.5) and the influence of weather factors on PM2.5 in Nanjing using Spearman-Rank analysis and the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) method. Hourly PM2.5 observation data and daily meteorological data were collected from 1 April 2013 to 31 December 2015. The spatial distribution result shows that the Maigaoqiao site suffered the most serious pollution. Daily PM2.5 concentrations in Nanjing varied from 7.3 μg/m3 to 336.4 μg/m3. The highest concentration was found in winter and the lowest in summer. The diurnal variation of PM2.5 increased greatly from 6 to 10 a.m. and after 6 p.m., while the concentration exhibited few variations in summer. In addition, the concentration was slightly higher on weekends compared to weekdays. PM2.5 was found to exhibit a reversed relation with wind speed, relative humidity, and precipitation. Although temperature had a positive association with PM2.5 in most months, a negative correlation was observed during the whole period. Additionally, a high concentration was mainly brought with the wind with a southwest direction and several relevant factors are discussed to explain the difference of the impacts of diverse wind directions.

Analysis and Modelling of PM2.5 Temporal and Spatial Behaviors in European Cities

“…Despite the weak variability observed at VDUTNL (Amsterdam) and HGUTSE (Stockholm) sites (σ = 0.69 µg/m 3 and 0.50 µg/m 3 , respectively), higher PM 2.5 levels also happened during colder months at both sites, decreasing during spring and summer. This pattern is commonly presented in a variety of studies related to PM 2.5 seasonality [6,[38][39][40][41][42]. On the other hand, higher concentrations during summer were observed at MNUTFI (Helsinki) (σ = 0.66 µg/m 3 ).…”

“…This behavior is commonly stated in a variety of studies about diurnal variations of PM 2.5 concentrations in different locations [6,40,51,52]. Increases of PM levels during the night period can be associated with more frequent temperature inversions and boundary layer dynamics related to that period [38,51,53,54]. In the case of MNUTFI (Helsinki) and HGUTSE (Stockholm), highly stable PM 2.5 diurnal concentrations were observed (σ = 0.39 µg/m 3 and 0.31 µg/m 3 , respectively).…”

“…On the other hand, higher concentrations during summer were observed at MNUTFI (Helsinki) (σ = 0.66 µg/m 3 ). As reported by some authors, a possible reason for this behavior is the stronger photochemical activity during higher temperatures, which contributes to the formation of secondary PM particles [38,43]. Biogenic emissions, which are higher in warmer seasons, can also have a significant impact on PM 2.5 levels during that season [44][45][46][47].…”

“…These results were obtained from the determined model based on the 2015-2016 period because this period allowed for evaluating the effect of all the variables mentioned above for both regimes. These explanatory variables are also commonly found as prominent in PM 2.5 behaviors by different authors [7,38,42,43,[59][60][61][62][63]. Figure 17 presents the combined effects of temperature (T), wind speed (WS), relative humidity (RH) and PM10 concentrations (PM10) on PM2.5 concentrations, for two different regimes (RH < 79.1% and for RH ≥ 79.1%), at SIUCTR (Istanbul).…”

Characterization of atmospheric trace gases and particulate matter in Hangzhou, China

“…Being one of the most rapidly growing regions in China in terms of transportation, industries, and urbanization, it has become a hot spot for air pollution over the past 3 decades, together with the Pearl River Delta (PRD) and Beijing-Tianjin-Hebei (BTH) regions. To date, numerous combined studies of O 3 and PM 2.5 were implemented in representative urban cities in the YRD region such as Shanghai (Geng et al, 2007;Ding et al, 2013;Miao et al, 2017a) and Nanjing Kang et al, 2013;Chen et al, 2016). On the contrary, in • E), the capital city of Zhejiang Province in the YRD region, which lies along the mid-YRD, only a few sole studies of PM 2.5 or O 3 have been sporadically conducted.…”