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Ranked by formulaVerdict: NotablePM2.5 Composition and Organic Matter Sources in Pretoria, South Africa Employing Fourier Transform-Infrared Spectroscopy
The World Health Organization (WHO) estimates that about 91% of the global population live in regions with polluted air - resulting in approximately 7 million premature deaths annually.
Key numbers
- 91% of the global population
- 50% of the days exceeding
VerdictWorth a reader's time today.
Abstract
The World Health Organization (WHO) estimates that about 91% of the global population live in regions with polluted air – resulting in approximately 7 million premature deaths annually. These deaths occur primarily in Low- and Middle-Income Countries (LMICs). Organic Matter (OM) often dominates PM2.5 mass, warranting its quantification, particularly in LMICs having limited PM measurements. In this study, we demonstrate the capability of Fourier Transform-Infrared Spectroscopy (FT-IR) method for providing OM quantification and characterization in Pretoria, South Africa (LMIC) at a Surface Particulate Matter Network (SPARTAN) site. Polytetrafluoroethylene (PTFE) filters were collected with an AirPhoton SS5 Sampler every third day for 24-hour intervals from April 2021 to Dec 2022. The collected samples were analyzed for mass concentration, elemental carbon (EC), functional groups and organic matter (OM), inorganic ions, elements, and light absorption. The FT-IR spectra affected by the Christiansen peak effect (scattering effect) were identified, and a revised algorithm was employed to measure the affected functional groups. The mean concentration of PM2.5 was 16.8 µg/m3, with around 50% of the days exceeding the WHO guideline. We present the daily, seasonal, and overall variation of the chemical composition of collected PM2.5. Organic matter source classes and their geographical origins were determined through the Positive Matrix Factorization (PMF) model, using the baseline-corrected FT-IR spectra. The source classes were validated through pollution roses, back-trajectory analysis, correlation plots with inorganic species, and fire data products. Seven factors were identified that later were combined into two broad source classes: biomass burning (BB)/ biogenic SOA and fossil fuel combustion (FFC). BB/ biogenic SOA was the dominant source in the winter and early spring, while the FFC was ubiquitous with the dominant contribution in summer. Further investigation of the BB/ biogenic SOA factor identified three individual factors: biogenic SOA, biomass burning, and industrial & vehicular emissions mixed source. The findings of the study will help inform model validation of simulated SOA species, while also potentially identifying gaps in biogenic SOA, BB, and FFC emissions quantification in Pretoria, South Africa. In Pretoria, South Africa, from April 2021 to December 2022 approximately half of the PM2.5 was composed of organic matter (OM). Ammonium sulfate (30%), EC (13%), and dust (10%) also contributed to PM2.5 in notable fractions. OM is composed of organic functional groups. Higher fractions of oxygenated functional groups including alcohol, carboxylic acid and non-acid carbonyl were observed in the winter and spring while carbon-hydrogen functional groups dominated in the summer. Two major sources of OM were identified: (1) biomass burning and biogenic secondary organic aerosol (SOA) (BB/biogenic SOA), and (2) fossil fuel combustion (FFC). BB/biogenic SOA was dominant source in spring and winter (~ 65%) while the FFC was ubiquitous with the dominant contribution in summer (92%). BB/biogenic SOA was further separated into three sources: pure biomass burning source, a biogenic SOA component and a mixed (burning and industrial) source. Mixed source dominated the BB/biogenic SOA during the autumn, and pure biomass burning source dominated the winter and spring while the biogenic SOA dominated in summer only.
The editor's rubric
| Dimension | Level | Weight | What that level means |
|---|---|---|---|
| Leverage | ███░░ 3 | 16% | A method or resource many groups across the field will adopt within a year. |
| Magnitude | ███░░ 3 | 20% | Large gain: roughly 2x, or a clear new state of the art on a hard, unsaturated problem. |
| Evidence | ███░░ 3 | 20% | Solid: multiple benchmarks or cohorts, ablations, fair baselines, released code or data. |
| Novelty | ██░░░ 2 | 10% | A new combination of known ideas. |
| Trajectory | ██░░░ 2 | 14% | Some room to improve with obvious engineering. |
| Stakes | ███░░ 3 | 20% | Meaningful benefit to many people within a few years. |
Editor’s rationale
Heuristic triage from title and abstract text only, not a reading of the paper. Cues found: method (we propose, we report); gains (outperforms); verification (experimental validation); stakes (global scale, energy, climate).
How the score was computed
- Merit
- 5.5 / 10
- Adjusted merit
- 4.7 / 10
- Attention
- 0%
- Freshness
- 79%
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