There has been a proliferation of inexpensive consumer-grade devices for monitoring air pollutants, including PM 2.5 and certain gasses. This study compared the performance of four consumer-grade devices-the Air Quality Egg 2 (AQE2), BlueAir Aware, Foobot, and Speck-that utilize optical sensors to measure the PM 2.5 concentration. The devices were collocated and operated for 7 days in each of three residences, and the PM 2.5 mass concentrations were compared with those measured by established optical sensing devices, viz., the personal DataRAM and DustTrak DRX, as well as the filter-based Personal Modular Impactor (PMI).Overall, the Foobot and BlueAir displayed the strongest correlations with the direct-reading reference instruments for both the hourly and daily PM 2.5 mass concentrations. Comparing the 1-hour averages obtained with the DustTrak DRX for all of the residences with those obtained with the Foobot, BlueAir, AQE2, and Speck, the Pearson's correlation coefficients (R's) were 0.80, 0.88, -0.028, and 0.60, respectively. Overall, the strength of the correlation depended on the specific residence, likely due to the differences in aerosol composition. The correlations with the PMI measurements were moderate, with R values of 0.44 and 0.56 for the BlueAir and Foobot, respectively. The correlation coefficients for the daily values obtained with the AQE2 and Speck were -0.59 and 0.70 compared to the PMI. According to a paired t-test, the average 24-h PM 2.5 concentration data obtained using the consumer-grade monitors were statistically different (p > 0.05) from the mass values measured by the gravimetric filters. Overall, this study demonstrates the ability of consumergrade air pollution monitors to report PM 2.5 trends accurately; however, for accurate mass concentration measurements, these monitors must be calibrated for a particular location and application. Further testing is needed to determine their suitability for long-term indoor field studies.
We characterized the composition, diversity, and potential bacterial aerosol sources in Athens’ urban air by DNA barcoding (analysis of 16S rRNA genes) during three seasons in 2019. Air samples were collected using the recently developed Rutgers Electrostatic Passive Sampler (REPS). It is the first field application of REPS to study bacterial aerosol diversity. REPS samplers captured a sufficient amount of biological material to demonstrate the diversity of airborne bacteria and their variability over time. Overall, in the air of Athens, we detected 793 operational taxonomic units (OTUs), which were fully classified into the six distinct taxonomic categories (Phylum, Class, Order, etc.). These OTUs belonged to Phyla Actinobacteria, Firmicutes, Proteobacteria, Bacteroidetes, Cyanobacteria, and Fusobacteria. We found a complex community of bacterial aerosols with several opportunistic or potential pathogens in Athens’ urban air. Referring to the available literature, we discuss the likely sources of observed airborne bacteria, including soil, plants, animals, and humans. Our results on bacterial diversity are comparable to earlier studies, even though the sampling sites are different or geographically distant. However, the exact functional and ecological role of bioaerosols and, even more importantly, their impact on public health and the ecosystem requires further air monitoring and analysis.
This study is the first attempt to describe the composition, diversity, and potential sources of bacterial aerosols in the urban air of Athens by DNA barcoding (analysis of 16S rRNA genes). It is also the first field application of the recently developed Rutgers Electrostatic Passive Sampler (REPS) to study the microbial diversity of aerosols. Three sampling campaigns 6–10 days in duration were conducted in the summer and fall of 2019. The completely passive REPS captured a sufficient amount of biological material to demonstrate the diversity of airborne bacteria and their variability over time. Overall, in the air of Athens, 793 OTUs were detected. Firmicutes, Proteobacteria, and Actinobacteria were the dominant Phyla, while the Cyanobacteria, Bacteroidetes, and Fusobacteria were the minor Phyla. The observed Phyla were further classified into 54 families. The families with high prevalence across our samples contained genera known to have pathogenic species, e.g., Streptococcus, Corynebacterium, Gemella, Pseudomonas, Staphylococcus, Neisseria; many species belonging to human or animal commensal microbiota were also detected. The paper discusses the likely sources of observed airborne bacteria, including soil, plants, animals, humans. Given the variability in bacterial composition over time, it is obvious that the contribution of those sources to airborne microbiota is dynamic. However, a more accurate linkage between the sources and airborne bacteria requires further study. Also, the exact functional and ecological role and, even more importantly, the impact of observed bacterial aerosols on public health and the ecosystem is still unknown and required further analysis.
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