Fine aerosols concentrations at Rwanda Climate Observatory and source apportionment of black carbon aerosols, 2014 – 2016

Leonard Kirago, Örjan Gustafsson, Samuel M. Gaita, Sophie L. Haslett, H. Langley deWitt, Jimmy Gasore, Katherine E. Potter, Ronald G. Prinn, Maheswar Rupakheti, Jean de Dieu Ndikubwimana, Bonfils Safari, August Andersson

The dataset contains bi-annual measurements of fine aerosols at the Rwanda climate Observatory, a mountaintop site and part of the Advanced Global Atmospheric Gases Experiment network.

Large-scale biomass fires in Africa emit vast amounts of aerosols and gases into the atmosphere, perturbing the regional climate. This dataset addresses the large uncertainties related to the climate impact of key climate-warming components from these emissions.

The filter-based PM2.5 samples, collected between May 2014 and April 2016, were analysed for carbonaceous aerosols (Organic matter and black carbon), water-soluble inorganics, and carbon isotopes (Δ¹⁴C and ẟ¹³C) for the black carbon fraction calculations. The dual-carbon isotope signatures were used to quantify the relative contribution of black carbon to the emissions and the relative contribution of liquid fossil C4 plants and C3 plants.

Citation

Leonard Kirago, Örjan Gustafsson, Samuel M. Gaita, Sophie L. Haslett, H. Langley deWitt, Jimmy Gasore, Katherine E. Potter, Ronald G. Prinn, Maheswar Rupakheti, Jean de Dieu Ndikubwimana, Bonfils Safari, August Andersson (2024) Fine aerosols concentrations at Rwanda Climate Observatory and source apportionment of black carbon aerosols, 2014 – 2016. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/kirago-2024-fine-aerosols-1

References

Kirago, L., Gustafsson, Ö., Gaita, S. M., Haslett, S. L., deWitt, H. L., Gasore, J., Potter, K. E., Prinn, R. G., Rupakheti, M., Ndikubwimana, J. de D., Safari, B., & Andersson, A. (2022). Atmospheric Black Carbon Loadings and Sources over Eastern Sub-Saharan Africa Are Governed by the Regional Savanna Fires. Environmental Science & Technology (Vol. 56, Issue 22). American Chemical Society (ACS). https://doi.org/10.1021/acs.est.2c05837

Data description

The data is provided as a .xlsx file with two sheets. The first sheet Meta-Data contains a ReadMe to the data. The second sheet Mugogo_Data contains information on concentrations of different aerosol species.

Column names:

1. filter_id Filter ID
2. day_start Day the measurements were started
3. month_start Month the measurements were started
4. year_start Year the measurements were started
5. day_end Day the measurements were stopped
6. month_end Month the measurements were stopped
7. year_end Year the measurements were stopped
8. time_collected Time the air was collected
9. v_air Volume of the air that was collected
10. oc Organic carbon in μg m⁻²
11. bc Black carbon in μg m⁻²
12. bc_cubic Black carbon in μg m⁻³
13. oc_cubic Organic carbon in μg m⁻³
14. nh4 Ammonium concentration in μg m⁻³
15. k Potassium concentration in μg m⁻³
16. so4 Sulfate concentration in μg m⁻³
17. no3 Nitrate concentration in μg m⁻³
18. mg0 Magnesium concentration in μg m⁻³
19. ca Calcium concentration in μg m⁻³
20. cl Chlorine concentration in μg m⁻³
21. oc/bc Mass ratio of organic carbon to black carbon
22. nh4/bc Mass ratio of ammonium concentration to black carbon
23. so4/bc Mass ratio of sulfate concentration to black carbon
24. k/bc Mass ratio of potassium concentration to black carbon
25. no3/bc Mass ratio of nitrate concentration to black carbon
26. rainfall Rainfall in mm
27. delta13_c carbon-13 isotope signatures of black carbon in per mille (‰)
28. delta14_c carbon-14 isotope signatures of black carbon in per mille (‰)
29. bc_c3 Fractional contribution of C3 plants burning to black carbon loadings
30. bc_c4 Fractional contribution of C4 plants burning to black carbon loadings
31. bc_fossil Fractional contribution of fossil fuels combustion to black carbon loadings

Comments

This dataset is part of the Advanced Global Atmospheric Gases Experiment. Carbonaceous aerosol concentrations were obtained by thermal optical transmission analysis (TOT; Sunset Laboratory, Tigard, Oregon) using NIOSH 5040 protocol, for each of the collected PM2.5 samples. Anion and cations were analysed using Dionex Aquion ion chromatography instrument (Thermo Finnigan LLC). Twenty samples over the two-year study period, mostly during high black carbon (BC) loading events in the dry season, were selected for isotope analysis of the BC isolate. Here, the BC fraction of the carbonaceous aerosols was isolated, cyro-trapped and shipped to Tandem Laboratory in Uppsala University and analyzed for dual carbon isotopes. The ẟ¹³C signatures were measured using an isotope ratio mass spectrometer (IRMS), while radiocarbon signatures were measured using accelerator mass spectrometry (AMS). The source fractions and their uncertainties were estimated through Markov chain Monte Carlo (MCMC) simulations, implemented in Matlab 2019b (1000 000 iterations; 10 000 burn-in; 100 data thinning).