ISSS608 2018-19 T1 Assign Lim Si Ling Evelyn Task 1
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Figure 1 – Time Series plot for Maximum and Average PM10 concentration recorded for each day from 2013 to 2018.
Data Anomaly
1 – There are no reading recorded between 1 Jan 2017 to 27 Nov 2017 and on 20 Jan 2016.
2 – Mladost station only started operation on 1 Jan 2018 while Orlov Most station stopped operation after 1 Oct 2016.
3 – Generally, readings which were taken before 1 Jan 2017 were daily average readings while readings taken after 1 Dec 2017 were hourly average readings. However, there are hourly averaging time captured on some days in 2016 and daily averaging time captured on some days in 2018. For analysis of Past and Present situation, period for Past will be from year 2013 to 2016 and Present will be from 1 Dec 2017 to 14 Sep 2018. Anomaly data will be excluded.
Observations
1 – Higher concentration of PM10 during winter months
PM10 concentration usually peak between November to February which coincides with winter months in Sofia City.
2 – Did PM10 pollution worsen?
Maximum hourly average PM10 concentration were higher for Hipodruma and IAOS/Pavlovo stations when compared to daily average. However, maximum hourly average and daily average PM10 concentration for Druzhba station remains consistent. When comparing between Past and Present, it is not definitive to conclude that the air quality around Hipodruma and IAOS/Pavlovo had worsened as maximum value might have been lowered because of the daily average aggregation method.
For a fair comparison, average PM10 concentration chart should be used to compare the daily situation between Past and Present. From the average chart, it shows that the present situation improved.
Figure 2 – Air Quality Stations in Sofia City
Figure 3 – Official Station Data Against Topography Data
All of them are located in central Sofia City. When compared against the given topography data, altitude for Mladost station is not correctly captured.
Figure 4 – Air Quality from 2013 to 2016 by classifying daily average PM10 concentration by Common Air Quality Index (CAQI) and the bar shows % of days with observations under the various categories for each station, month and year.
Observations
1 – Air quality for most days in April to September were within the healthy range of ≤50, i.e. Low and Very Low. Sofia City was exposed to unhealthy PM10 pollutant range for more than 50% of the times in December and January. Situation was very bad in Dec 2013 to Jan 2014 where at least 50% of the months are in High to Very High range.
2 – With respect to the proportion of days in the unhealthy range, the situation seems to have worsen from 1 Jan 2013 to Feb 2014 but improved afterwards.
3 – Area near Hipodruma, IAOS/Pavlov and Orlov Most stations seem to be more exposed to PM10 pollution compared to other stations.
Figure 5 – Average and Median hourly average of PM10 concentration aggregated by Month, Time of the Day and Station for readings taken from Dec 2017 to Sep 2018
Observations
1 – Daily PM10 concentration is right skewed as Median is lower than Average from the colour coding of CAQI where daily average PM10 concentration is higher than daily median PM10 concentration.
2 – Daily average PM10 concentration was in the healthy range for most of the months except for Jan 2018 and Dec 2017 for area near Nadezhda station. For Jan 2018 pollutant is higher during dawn and after sunset.
3 – Daily Median PM10 concentration was in healthy range for all the months and time of the day except for 9-10am in Jan 2018. i.e. citizen living near the stations were exposed to healthy range of PM10 at least half of the time.
Figure 6 – Median PM10 concentration in Jan 2018 (among the 5 stations) to investigate for 9-10am in Jan 2018
From figure 6, it is evident that the high concentration between 9am-10am in January 2018 is because only 3 days were recorded, and those days happened to be days which were highly polluted. PM10 concentration was higher at the start of the month and towards the end of the month and dirty air were continuous for a few days.
The map on the left also shows that maximum PM10 levels are relatively high for all the stations except Druzhba.
Figure 7 – Distribution of Hourly Average for Dec 2017 and Jan 2018 by Station
Figure 7 shows that most of PM10 hourly average were within the healthy range. It is interesting to note that hourly average is consistently higher for Nadezhda station in Dec 2017 and Hipodruma station in Jan 2018.
Figure 8 & 9– Situation of PM10 pollution with Calendar View
Calendar view allows users to have a better visual understanding of the situation in a more conventional manner. It also allows users to view if any particular day is more prone to pollution.
Tableau Public link for Air Quality in Sofia City - Official Data
Banner Photo from Pexels
