Comparing Methods to Impute Missing Daily Ground-Level PM10 Concentrations between 2010–2017 in South Africa
Abstract
:1. Introduction
2. Materials and Methods
2.1. Methods
2.2. Monitoring Sites
2.3. Quality Check and Data Management
2.4. Temporal Parameters
2.5. Spatial Parameters
2.6. Random Forest Model
- Randomly resample the data with replacement to create training and validation sets of same sample size as the original dataset.
- Repeatedly construct regression trees on the training sets and predict on the validation sets.
- At each trees node, the best predictors from the random subsets of predictors were subsequently used to partition the nodes of respective trees.
- The final estimate of PM10 is the average of individual trees of PM10 predictions in a process called bagging.
2.7. Model Validation
2.8. Error Metrics
3. Results
3.1. National Model
3.2. Provincial Model
3.3. Site-Specific Models
3.4. Models Prediction
4. Discussion
5. Conclusions
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Variable | Description | Source | Resolution |
---|---|---|---|
Population density | Mean population within 1 × 1 km2 grid cell | SEDAC | ~1 km |
Landcover | South Africa National Land Cover 2018 densities (summary of meters within the grid cells by land cover categories of Natural, Built-up, Residential, Agricultural, Industrial) | South Africa Department of Environmental Affairs. | 20 m |
Light at night | 1 × 1 km2 Intersected aggregate | VIIRS-DNB | 750 m |
Impervious Surface | 1 × 1 km2 Intersected aggregate after removing no data, clouds, shadows data | NOAA | 30 m |
Elevation | 1 × 1 km2 intersected aggregate of mean elevation | SRTM Digital Elevation Database | 90 m |
Roads | Summary of road length distance to nearest road type: major roads and other roads | OpenStreetMap | Lines |
Climate zones | Cold interior, Temperate interior, Hot interior, Temperate coastal, Sub-tropical coastal, Arid interior | South Africa Bureau of Standards 2005 | 6 Zones |
Meteorological variables (daily modelled planetary boundary layer height, temperature, precipitation, wind speed, wind direction, relative humidity, vertical velocity | Daily global ECMWF re-analysis estimates | ERA5-reanalysis | 10 × 10 km |
Modeled Tropospheric estimates of NO2, PM10, O3 | Daily Chemical transport model estimate | Chemical transport model Copernicus Atmosphere Monitoring Service (CAMS) | 10 × 10 km |
Model Building | Spatial LOLO CV | Temporal LTO CV | Data Availability | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
R2 (Range) | RMSE (Range) | MAE (Range) | R2 (Range) | RMSE (Range) | MAE (Range) | R2 (Range) | RMSE (Range) | MAE (Range) | No of Unique Sites | Years | |
National | 0.77–0.79 | 12.1–16.76 | 8.69–11.38 | 0.11–0.35 | 17.72–29.47 | 13.62–23.65 | 0.77–0.79 | 12.31–16.43 | 8.85–11.39 | 20–44 | 2010–2017 |
Provincial * | |||||||||||
Mpumalanga | 0.73–0.81 | 14.03–19.35 | 9.63–12.13 | 0.39–0.69 | 22.06–36.21 | 13.5–29.59 | 0.73–0.78 | 13.55–19.21 | 9.85–12.01 | 5–17 * | 2010–2017 |
Gauteng | 0.49–0.79 | 10.34–23.36 | 9.24–16.75 | 0.26–0.52 | 19.72–34.25 | 15.69–29.42 | 0.52–0.79 | 15.11–23.43 | 9.94–16.87 | 6–18 * | 2010–2017 |
Western Cape | 0.29–0.71 | 6.74–8.73 | 5.11–6.72 | 0.35–0.54 | 7.38–11.22 | 5.76–8.86 | 0.44–0.66 | 6.66–23.29 | 5.18–17.92 | 1–11 * | 2010–2017 |
KwaZulu-Natal | 0.55–0.79 | 7.36–9.53 | 5.29–8.11 | 0.29–0.57 | 8.54–19.95 | 6.95–16.82 | 0.47–0.78 | 7.37–10.71 | 5.46–8 | 3–6 * | 2010–2017 |
Site-specific ** | |||||||||||
Beliville | 0.42–0.47 | 5.81–9.16 | 4.51–7.26 | NA | NA | NA | 0.45–0.49 | 5.67–9.02 | 4.45–7.03 | NA | 2012, 2013, 2015–2017 |
Bodibeng | 0.54–0.63 | 16.89–19.42 | 13.61–15.07 | NA | NA | NA | 0.57–0.67 | 16.36–18.91 | 13.32–14.87 | NA | 2012–2013 |
Brackenham | 0.41–0.49 | 8.06–8.95 | 6.31–7.10 | NA | NA | NA | 0.46–0.49 | 7.81–8.95 | 6.25–7.15 | NA | 2011, 2015–2017 |
Booysens | 0.45–0.67 | 22.13–22.82 | 17.99–20.77 | NA | NA | NA | 0.5–0.71 | 22.10–25.74 | 17.87–20.53 | NA | 2012,2014 |
Camden | 0.38–0.62 | 10.64–23.27 | 8.69–17.85 | NA | NA | NA | 0.39–0.65 | 10.29–22.43 | 9.61–17.15 | NA | 2013, 2015, 2017 |
CBD | 0.38–0.59 | 6.35–9.55 | 4.93–7.45 | NA | NA | NA | 0.41–0.64 | 6.28–9.23 | 4.98–7.21 | NA | 2011–2013, 2015–2017 |
City Hall | 0.45 | 10.29 | 7.69 | NA | NA | NA | 0.48 | 9.78 | 7.43 | NA | 2010 |
Elandsfontein | 0.39–0.52 | 11.72–12.49 | 9.38–9.68 | NA | NA | NA | 0.45–0.57 | 11.17–11.79 | 8.99–9.38 | NA | 2016–2017 |
Ermelo | 0.48–0.76 | 9.20–18.96 | 7.69–15.31 | NA | NA | NA | 0.51–0.77 | 9.12–19.98 | 7.54–13.89 | NA | 2010–2016 |
Etwatwa | 0.63 | 24.03 | 18.74 | NA | NA | NA | 0.69 | 23.78 | 18.56 | NA | 2012 |
Ferndale | 0.68–0.74 | 3.63–5.42 | 2.84–3.92 | NA | NA | NA | 0.65–0.77 | 3.49–5.38 | 2.76–3.88 | NA | 2010–2012 |
Foreshore | 0.32–0.49 | 5.29–9.76 | 4.1–7.22 | NA | NA | NA | 0.33–0.49 | 5.27–9.58 | 4.13–7.08 | NA | 2011–2013,2015–2017 |
Gangles | 0.48–0.74 | 11.86–13.4 | 9.22–10.11 | NA | NA | NA | 0.51–0.75 | 11.23–11.88 | 8.96–9.71 | NA | 2010, 2011, 2013,2014 |
Germiston | 0.42 | 19.65 | 14.96 | NA | NA | NA | 0.44 | 19.07 | 14.79 | NA | 2011 |
George | 0.55–0.56 | 7.09–8.41 | 5.49–6.56 | NA | NA | NA | 0.58 | 6.95–8.12 | 5.39–6.34 | NA | 2010, 2013 |
Goodwood | 0.46–0.57 | 6.77–8.78 | 5.26–8.24 | NA | NA | NA | 0.49–0.59 | 6.60–8.49 | 5.29–7.80 | NA | 2011–2012, 2014–2016 |
Grootvlei | 0.41–0.44 | 10.76–11.32 | 8.70–8.87 | NA | NA | NA | 0.42–0.49 | 10.65–11.12 | 8.63–8.82 | NA | 2011, 2013 |
Hendrina | 0.39–0.71 | 11.12–17.02 | 8.32–13.62 | NA | NA | NA | 0.43–0.74 | 11.18–16.56 | 8.36–12.96 | NA | 2010–2012,2015–2016 |
Middleburg | 0.67–0.81 | 7.81–19.25 | 6.08–14.73 | NA | NA | NA | 0.70–0.82 | 7.49–18.63 | 5.92–14.25 | NA | 2010–2016 |
Olievenhoutbosch | 0.57 | 34.23 | 27.01 | NA | NA | NA | 0.59 | 34.16 | 26.98 | NA | 2012 |
Orange Farm | 0.45–0.69 | 10.78–19.81 | 8.57–15.56 | NA | NA | NA | 0.49–0.71 | 10.23–19.49 | 8.28–15.62 | NA | 2010,2017 |
Rosslyn | 0.55–0.61 | 5.91–11.49 | 4.77–9.30 | NA | NA | NA | 0.52–0.67 | 5.86–11.05 | 4.47.8.93 | NA | 2012–2014 |
Secunda | 0.63–0.77 | 7.73–25.21 | 5.86–19.96 | NA | NA | NA | 0.67–0.77 | 7.47–24.64 | 5.75–19.7 | NA | 2010–2013 |
Witbank | 0.72–0.83 | 9.21–22.33 | 7.63–17.27 | NA | NA | NA | 0.73–0.83 | 8.79–21.87 | 7.34–16.75 | NA | 2010,2013–2016 |
Komati | 0.45–0.83 | 8.52–28.02 | 6.61–21.51 | NA | NA | NA | 0.46–0.84 | 8.29–27.11 | 6.5–20.91 | NA | 2011–2012,2014–2017 |
Leandra | 0.29–0.36 | 6.63–14 | 4.86–10.38 | NA | NA | NA | 0.35–0.4 | 6.35–13.64 | 4.81–10.31 | NA | 2011–2012 |
Newtown | 0.43 | 22.07 | 17.52 | NA | NA | NA | 0.47 | 21.68 | 17.27 | NA | 2012 |
Phola | 0.54–0.65 | 22.44–28.89 | 17.83–22.55 | NA | NA | NA | 0.57–0.65 | 22.02–28.88 | 17.48–22.72 | NA | 2013–2014,2016–2017 |
Stellenbosch | 0.35–0.56 | 6.34–7.31 | 4.85–5.67 | NA | NA | NA | 0.37–0.61 | 6.26–7.14 | 4.83–5.62 | NA | 2012–2013 |
Tableview | 0.36–0.4 | 5.63–7.04 | 4.43–5.81 | NA | NA | NA | 0.38–0.43 | 5.54–7 | 4.31–5.6 | NA | 2011–2013 |
Tembisa | 0.71 | 17.78 | 14.09 | NA | NA | NA | 0.73 | 17.35 | 13.89 | NA | 2011 |
Thokoza | 0.56 | 41.30 | 29.22 | NA | NA | NA | 0.57 | 40.25 | 28.76 | NA | 2011 |
Wallacedene | 0.47–0.51 | 5.53–11.26 | 4.28–8.9 | NA | NA | NA | 0.47–0.54 | 5.52–10.82 | 4.29–8.69 | NA | 2012, 2015–2017 |
Wattville | 0.52 | 39.10 | 29.09 | NA | NA | NA | 0.57 | 37.16 | 28.57 | NA | 2012 |
Club | 0.59–0.67 | 11.01–14.87 | 8.76–11.86 | NA | NA | NA | 0.62–0.69 | 10.7–14.88 | 8.55–11.99 | NA | 2012–2014, 2016–2017 |
Ekandustria | 0.46–0.59 | 11.14–16.83 | 8.88–13.09 | NA | NA | NA | 0.50–0.64 | 10.58–16.43 | 8.5–12.83 | NA | 2013–2014 |
Embalenhle | 0.56–0.73 | 16.48–22.18 | 11.34–14.69 | NA | NA | NA | 0.59–0.73 | 13.31–22.18 | 11.03–17.86 | NA | 2012,2014,2016–2017 |
Verkykkop | 0.44–0.49 | 6.63–9.71 | 5.53–7.88 | NA | NA | NA | 0.47–0.48 | 6.56–9.49 | 5.33–7.72 | NA | 2013,2016–2017 |
Randwater | 0.32–0.73 | 12.99–15.99 | 9.82–15.83 | NA | NA | NA | 0.36–0.75 | 12.08–15.63 | 9.57–12.19 | NA | 2013–2017 |
Esikhaweni | 0.43–0.58 | 9.07.9.45 | 7.36–7.4 | NA | NA | NA | 0.44–0.60 | 8.95–9.35 | 7.17 | NA | 2016–2017 |
Chicken Farm | 0.44 | 13.14 | 10.44 | NA | NA | NA | 0.48 | 12.71 | 10.21 | NA | 2017 |
Kwazamokuhle | 0.65 | 18.10 | 14.44 | NA | NA | NA | 0.67 | 17.10 | 13.84 | NA | 2017 |
Kriel Village | 0.62 | 17.27 | 13.55 | NA | NA | NA | 0.66 | 16.89 | 13.41 | NA | 2017 |
Bosjesspruit | 0.51 | 13.05 | 10.44 | NA | NA | NA | 0.55 | 12.58 | 10.27 | NA | 2017 |
Province | Mean | SD | Percentiles | |||||
---|---|---|---|---|---|---|---|---|
µg/m3 | µg/m3 | 5 | 25 | 50 | 75 | 95 | ||
Mpumalanga | Observed | 35.70–50.90 | 17.70–29.10 | 9.30–15.30 | 21.40–30.30 | 32.90–46.20 | 47.70–71.20 | 68.20–102.80 |
National | 34.60–48.60 | 6.30–11.10 | 23.70–34.20 | 29.20–41.10 | 34.30–47.80 | 39.50–56.80 | 45.70–66.50 | |
Provincial | 34.20–46.30 | 10.40–17.40 | 17.10–24.70 | 24.90–33.60 | 32.20–44.30 | 42.30–60.40 | 53.00–75.80 | |
Site-specific | 35.70–52.00 | 11.40–19.50 | 18.60–26.10 | 26.80–37.10 | 34.30–49.80 | 43.30–66.90 | 55.50–85.40 | |
Gauteng | Observed | 53.40–58.30 | 28.40–31.30 | 16.20–20.30 | 31.10–35.20 | 47.50–52.10 | 71.10–77.10 | 107.60–115.00 |
National | 36.30–41.60 | 10.20–12.90 | 21.30–24.40 | 27.00–31.00 | 34.80–40.70 | 44.60–52.00 | 54.00–62.40 | |
Provincial | 52.90–59.40 | 16.90–17.90 | 30.80–35.50 | 40.30–45.40 | 50.20–56.50 | 66.10–73.30 | 81.20–90.00 | |
Site-specific | 53.00–58.40 | 17.40–19.70 | 29.30–33.50 | 37.90–43.10 | 49.70–54.80 | 65.60–72.30 | 84.70–93.20 | |
Western Cape | Observed | 19.50–26.70 | 8.10–11.60 | 8.50–12.70 | 13.40–18.70 | 18.50–25.20 | 24.30–33.30 | 35.00–48.10 |
National | 31.90–49.10 | 7.10–11.20 | 22.00–35.90 | 26.00–41.00 | 29.90–46.80 | 36.60–55.40 | 45.20–71.60 | |
Provincial | 20.00–28.00 | 39.00–5.50 | 13.50–20.40 | 16.70–24.10 | 20.00–28.00 | 22.70–31.80 | 26.90–37.10 | |
Site-specific | 19.50–26.70 | 4.80–6.60 | 11.80–17.90 | 15.90–21.80 | 18.80–26.20 | 22.40–30.70 | 28.00–38.40 | |
KwaZulu-Natal | Observed | 24.20–29.80 | 11.01–14.01 | 9.50–13.50 | 15.90–20.01 | 22.10–26.60 | 30.70–37.10 | 45.70–56.60 |
National | 31.60–43.80 | 8.20–12.90 | 21.10–28.40 | 24.50–33.40 | 29.00–40.40 | 37.60–53.00 | 47.60–66.00 | |
Provincial | 23.90–32.90 | 5.20–9.50 | 15.60–21.60 | 19.20–25.90 | 22.50–31.60 | 27.10–39.40 | 35.40–49.50 | |
Site-specific | 24.20–30.50 | 6.01–10.02 | 15.30–19.70 | 19.10–23.30 | 23.00–28.30 | 28.00–36.00 | 36.00–50.80 |
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Arowosegbe, O.O.; Röösli, M.; Künzli, N.; Saucy, A.; Adebayo-Ojo, T.C.; Jeebhay, M.F.; Dalvie, M.A.; de Hoogh, K. Comparing Methods to Impute Missing Daily Ground-Level PM10 Concentrations between 2010–2017 in South Africa. Int. J. Environ. Res. Public Health 2021, 18, 3374. https://doi.org/10.3390/ijerph18073374
Arowosegbe OO, Röösli M, Künzli N, Saucy A, Adebayo-Ojo TC, Jeebhay MF, Dalvie MA, de Hoogh K. Comparing Methods to Impute Missing Daily Ground-Level PM10 Concentrations between 2010–2017 in South Africa. International Journal of Environmental Research and Public Health. 2021; 18(7):3374. https://doi.org/10.3390/ijerph18073374
Chicago/Turabian StyleArowosegbe, Oluwaseyi Olalekan, Martin Röösli, Nino Künzli, Apolline Saucy, Temitope Christina Adebayo-Ojo, Mohamed F. Jeebhay, Mohammed Aqiel Dalvie, and Kees de Hoogh. 2021. "Comparing Methods to Impute Missing Daily Ground-Level PM10 Concentrations between 2010–2017 in South Africa" International Journal of Environmental Research and Public Health 18, no. 7: 3374. https://doi.org/10.3390/ijerph18073374