The average PM10 concentration was 36.71±19.72 µg/m³ during the study period in Uskudar station in 2020 (Fig.4). The average PM10 concentrations were 40.18±18.43 µg/m³ and 31.56±20.75 µg/m³ during the BV and the AV respectively. PM10 concentration during the AV was lower than the BV for all years except 2016 and 2018. Also, the minimum PM10 concentration was obtained in 2020. Although the minimum temperature was seen, which in turn expectation of high PM10 concentration, the minimum PM10 concentration was observed during the AV in 2020. Thanks to precautions taken for COVID-19 epidemic, there was statistically significant difference for PM10 concentration between the BV and the AV in 2020, statistically (p=0.019; p<0.05) (Table 1).
The avarage PM10 concentration was 46.85±21.32 µg/m³ for the study period at Sirinevler station in 2020 (Fig.5). As it was expected, the avarage PM10 concentration during the AV (45.58±23.57 µg/m³) was lower than the BV (47,85±19,56 µg/m³). Except 2018, the PM10 concentration during the BV was higher than the AV for all years. However, the differences between the BV and the AV were not attributed to positive affect on air quality in terms of PM10 concentration. Although 2016 has the lowest value for PM10 concentration, there was no meaningful difference for PM10 concentrations between the BV and the AV, statistically (p=0,388; p> 0.05) (Table 1).
The average PM10 concentration was 57.31±28.40 µg/m³ in the study period and PM10 concentration during the BV (56.25±20.31 µg/m³) and the AV (58.47±35.55 µg/m³) were seen very close to each other at Mecidiyekoy station in 2020 (Fig.6).. Unfortunately, there was no significant difference for PM10 concentrations between the AV and the BV, while expecting the AV to be lower than the BV. This indicates the importance of other emission sources for PM pollutant, such as commercial and institutional buildings, household heating, etc. Contrary to expectations it was not seen positive effect of COVID-19 pandemic related to mobility on air quality at Mecidiyekoy station in the study period. Consequently, the statistically significant difference could not be seen for the PM10 concentrations regarding to Mecidiyekoy stations (p=0,608; p> 0.05) (Table 1) during the BV and the AV.
The average PM10 concentration was 32.35±13.20 µg/m³ at Umraniye station for the study period in 2020 (Fig.7). There was approximately equality for PM10 concentrations between the BV (32.49±9.80) and the AV (32.18±16.56 µg/m³) in 2020. Although the PM10 concentration during the AV was higher than the BV between 2016 and 2018, the PM10 concentrations during the AV were lower than the BV in 2019 and 2020. However, it cannot be seen the positive effect of the prevention taken for COVID-19 pandemic on air quality in the manner of PM10 concentration between the BV and the AV. Hence, there was no statistically significant difference for PM10 concentration during the BV and the AV (p = 0.395; p >0.05) (Table 1). Interestingly, for PM10 higher exceedances were recorded during the AV more than the BV only at Umraniye Station in Istanbul.
The average PM10 concentrations of Istanbul, were calculated using the data from Uskudar, Sirinevler, Mecidiyekoy and Umraniye stations, were seen in Fig. 8. The average PM10 concentration was 43.22±19.76 µg/m³ for the study period in İstanbul. There was approximately equality for PM10 concentrations between the BV (43.79±15.37 µg/m³) and the AV (42.50±24.41 µg/m³) in 2020. Although PM10 concentrations during the AV was lower than the BV comparing to all years except 2017, there was no statistically significant difference for PM10 concentration between the BV and the AV (p =0.215; p>0.05) (Table 1). Hence, the precaution taken for COVID-19 pandemic on air quality was not effective. This indicates the importance of other emission sources for PM10 pollutant, such as commercial and institutional buildings, household heating, etc.
When considering to all station, it was not seen statistically significant difference according to all stations (p>0.05) except Uskudar station (p=0.019; p<0.05) (Table 3.) for PM10 concentrations between the BV and the AV. Therefore, the binary comparison was made to identify the group that creates the differency between all stations for PM10 concentration. According to the binary comparison, there was statistically signifant difference for PM10 concentrations between the BV and the AV: Uskudar-Mecidiyekoy, Sirinevler-Umraniye, Mecidiyekoy-Umraniye stations (p<0.01); Uskudar-Sirinevler, Uskudar-Mecidiyekoy, Sirinevler-Umraniye, Mediyekoy-Umraniye stations (p<0.05) respectively (Table 1).
Table 1: Evaluations of PM10 concentrations during the BV and during the AV at all Stations.
Stations
|
|
PM10 concentrations in 2020
|
ap
|
|
BV (n=44)
|
AV (n=35)
|
1Uskudar
|
Min.-Max.(Median)
Avrg.±SD
|
10,4-77,2 (40,7)
40,18±18,43
|
12,9-116,2 (27)
31,56±20,75
|
0,019*
|
2Sirinevler
|
Min.-Max.(Median)
Avrg.±SD
|
19,9-116,1 (43,8)
47,85±19,56
|
22,3-131,7 (41,8)
45,58±23,57
|
0,388
|
3Mecidiyeköy
|
Min.-Max.(Median)
Avrg.±SD
|
22,3-125,5 (53,4)
56,25±20,31
|
26,6-185,1 (51,7)
58,47±35,55
|
0,608
|
4Umraniye
|
Min.-Max.(Median)
Avrg.±SD
|
15,6-55,9 (30,1)
32,49±9,80
|
12,8-83,2 (29)
32,18±16,56
|
0,395
|
|
bp
|
0,001**
|
0,001**
|
|
Binary evaluations between stations
|
cp1-2
|
0,321
|
0,010*
|
|
cp1-3
|
0,001**
|
0,001**
|
|
cp1-4
|
0,200
|
1,000
|
|
cp2-3
|
0,263
|
0,810
|
|
cp2-4
|
0,001**
|
0,024*
|
|
cp3-4
|
0,001**
|
0,001**
|
|
aMann Whitney U Test bKruskal Wallis Test cBonferroni Dunn Test
**p<0.01 *p<0.05
The average NO2 concentration was 41.90±18.79 µg/m³ during the study period at Uskudar station in 2020 (Fig.9). The average NO2 concentrations were 48.12±18.06 µg/m³ and 33.34±16.47 µg/m³ during the BV and the AV respectively. Considering to all years the NO2 concentration during the AV was higher than the BV, except 2020. In addition, the minimum temperature was observed in 2020, which in turn expectation of high NO2 concentration, the minimum NO2 concentration was seen during the AV in 2020. This result exhibits that precautions taken for COVID-19 epidemic had positive effects on air quality. Hence, significant difference was seen for NO2 concentrations between the BV and the AV in 2020, statistically (p=0.001; p<0.01) (Table 2).
The average NO2 concentration was 62.96±23.71µg/m³ during the study period at Sirinevler station in 2020 (Fig.10). The average concentration was identified as 50.05±21.13 µg/m³ during the AV, while it was 72.94±20.75 µg/m³ during the BV. Except 2018, the NO2 concentration during the BV was higher than the AV among all years. Although 2020 had the minimum temperature in five years, the difference of NO2 concentrations between the BV and the AV was maximum level in 2020. The positive contribution of precautions taken for COVID-19 was clearly seen. Statistically significant difference for this pollutant during the BV and the AV (p=0.001; p <0.01) supports these comments (Table 2).
The average NO2 concentration was 44.41±15.35 µg/m³ during the study period at Mecidiyekoy station in 2020 (Fig.11). While the average NO2 concentration was 48.79±16.05 µg/m³ during the BV, it was 39.52±13.09 µg/m³ during the AV. Contrary to other years, the average NO2 concentration during the AV was lower than the BV in 2020. This situation indicates the results of the prevention taken for COVID-19 on air quality are positive. In addition, there was statistically significant difference for NO2 concentration between the BV and the AV (p=0.02; p <0.05) supports this comment (Table 2).
The average NO2 concentration was 53.36±14.04 µg/m³ during the study period in 2020. While the average NO2 concentration during the AV (47.08±11.58 µg/m³) was lower than the BV (57.99±14.01 µg/m³) (Fig.12). Although, the average NO2 concentration during the BV was higher than the AV comparing to all years. Due to COVID-19 outbreak, NO2 concentration during the AV was lower than the BV in 2020. This situation shows the success of social isolation to prevent COVID-19 pandemic, also statistically supported (p=0.002; p<0.01) (Table 2).
The average NO2 concentrations of Istanbul were detected using the data from Uskudar, Sirinevler, Mecidiyekoy and Umraniye stations, in Fig. 13. The average NO2 concentration was 50.82±15.65 µg/m³ during the study period in 2020. Unlike other years, the average NO2 concentration during the BV (57.61±13.20 µg/m³) was higher than the AV (42.03±14.68 µg/m³), in 2020. This result illustrates the positive effect of COVID-19 pandemic on air quality, also statistically supported (p=0.001; p<0.01) (Table 2).
The statistically significant difference was seen in the NO2 concentrations at all stations (for Uskudar, Sirinevler and Umraniye p<0.01; for Mecidiyekoy p<0.05) during the BV and the AV. The group that creates the difference of NO2 concentration between the BV and AV were detected by binary comparison. According to binary comparison, there was statistically signifant difference between Uskudar-Sirinevler, Sirinevler-Mecidiyekoy, Mecidiyekoy-Umraniye (p<0.01); Uskudar-Sirinevler, Uskudar-Umraniye stations (p<0.01) during the BV and the AV, respectively (Table 2).
Table 2: Evaluation of NO2 Concentrations in the BV and in the AV at all Stations.
Stations
|
|
NO2 concentrations in 2020
|
ap
|
|
BV (n=44)
|
AV (n=35)
|
1Uskudar
|
Min.-Max.(Median)
Avrg.±SD
|
15,9-92,8 (46,3)
48,12±18,06
|
9-67,6 (25,7)
33,34±16,47
|
0,001**
|
|
2Sirinevler
|
Min.-Max.(Median)
Avrg.±SD
|
33,9-122 (68,6)
72,94±20,75
|
18,9-99,4 (41,6)
50,05±21,13
|
0,001**
|
3Mecidiyekoy
|
Min.-Max.(Median)
Avrg.±SD
|
20,7-75,9 (53,1)
48,79±16,05
|
16,9-67,5 (35,4)
39,52±13,09
|
0,020*
|
4Umraniye
|
Min.-Max.(Median)
Avrg.±SD
|
29,4-86,3 (55,3)
57,99±14,01
|
23,2-69,3 (47,8)
47,08±11,58
|
0,002**
|
|
bp
|
0,001**
|
0,001**
|
|
Binary evaluations between stations
|
cp1-2
|
0,001**
|
0,003**
|
|
cp1-3
|
1,000
|
0,815
|
|
cp1-4
|
0,099
|
0,003**
|
|
cp2-3
|
0,001**
|
0,254
|
|
cp2-4
|
0,009**
|
1,000
|
|
cp3-4
|
0,371
|
0,214
|
|
aMann Whitney U Test bKruskal Wallis Test cBonferroni Dunn Test
**p<0.01 *p<0.05
According to the related regulation (RAQAM) in Turkey and EU Directive, 24h averages of PM10 and 1 h averages of NO2 limit values are 50µg/m3 and 200 µg/m3 respectively. 24 h averages PM10 limit was exceeded 3 times during the AV-9 times during the BV at Uskudar station, 10 times during the AV-12 times during the BV at Sirinevler station, 16 times during the AV-21 times during the AV at Mecidiyekoy station, 4 times during the AV-2 times during the BV at Umraniye station. The number of days that cannot be measured PM10 concentration were 6, 0, 4, 1 day during the AV and 1, 0, 10, 3 during the BV at Uskudar, Sirinevler, Mecidiyekoy and Umraniye stations respectively. The NO2 concentrations 1 h averages were exceeded only once at Sirinevler station among all stations. The number of days that cannot be measured for NO2 concentration were 3, 1, 1, 4 days during the AV and 0, 0, 6, 2 during the BV at Uskudar, Sirinevler, Mecidiyekoy and Umraniye stations respectively.