Journal of Aerosol Science最新文献

The exposure to air fine aerosols can cause health effects due to inhalations of alpha emitters such as ²²²Rn daughters. Lead-210 and ²¹⁰Po are mainly associated to aerosols with median aerodynamic diameter lower than 1 μm. The ²¹⁰Po is characterized by having a high radiotoxicity. The precise measurement of ²¹⁰Po in surface air aerosols is usually quite complex due to the significant contribution of the ²¹⁰Pb on their concentrations. Additionally, there is no possible means to manufacture a certified material to validate the measurements of ²¹⁰Pb and ²¹⁰Po concentrations in surface air aerosols. For these reasons, this study aims to develop a novel and comprehensive methodology to validate ²¹⁰Po measurements in surface air aerosols by preparing in our laboratory “standard samples” with known activities of both ²¹⁰Pb and ²¹⁰Po. A detailed sensitivity analysis on the precision of ²¹⁰Po concentration measurements has been carried out as a function of the involved variables such as sampling time, time elapsed between the sampling start and ²¹⁰Po self-deposition and the ²¹⁰Po/²¹⁰Pb activity ratio in surface air aerosols. This study is necessary to find the optimum conditions for a precise measurement of ²¹⁰Po in surface air aerosols. In addition, this methodology has been applied for the determination of ²¹⁰Po concentrations in 30 samplings campaigns of atmospheric aerosols carried out at the El Carmen campus (Huelva province) from March 25th to July 15th, 2022. The results obtained for ²¹⁰Pb and ²¹⁰Po concentrations and atmospheric aerosol residence times (via ²¹⁰Po/²¹⁰Pb activity ratio) were consistent with other previous works.

Bioaerosol generation, sampling, and cultivation-independent quantification of pathogenic bacteria play a crucial role in studying dose-response effects of Legionella pneumophila. Here, the Next Generation Impactor (NGI), initially created for pharmaceutical inhaling studies, was assessed for its potential to sample airborne bioaerosols and to separate size-dependent wet droplets by incrementally increasing the airflow speed. This stainless-steel sampler was shown in this study to be suitable for sampling prior to cultivation-independent analysis of pathogen-containing bioaerosols using washable cups. The applicability was studied by quantifying the total and intact cell count of L. pneumophila by flow cytometry after being dispersed into a droplet aerosol. Our results demonstrate a high total sampling efficiency of 95.5% ± 11.8% despite a lower biological sampling efficiency of 59.7% ± 16.5% for dry aerosols. However, by elevating the relative humidity (RH) to 100% in a liquid aerosolization unit, the biological sampling efficiency increased to over 90% for L. pneumophila. More than 50% of the cells were found in stage 1 using the liquid aerosolization unit. In comparison, 80% of the cells were sampled in stages 4–6 at 30% RH. Specifically, while at 100% RH, the droplet size mattered, at 30% RH, the size distribution of dry particles, in this case L. pneumophila, was relevant due to evaporation processes, which explains the size differences. These findings indicate the potential of the NGI for further exploration and application in studying other aerosol-borne pathogens, especially concerning the size distribution of wet droplets, viability, or effect-based bioanalysis.

Livestock farms are hotspots of antibiotic resistance due to the intensive use of antibiotics, in which the characteristics of air-borne and feces-borne antibiotic resistance genes (ARGs) and microbial communities are of great significance. This study delves into the distribution of ARGs and microbial communities across various livestock farms in China, and the correlation of microorganisms between livestock farms and other global environments was investigated. The concentrations of ARGs and mobile genetic elements (MGEs) in air samples were basically at the same level, but those in fecal samples collected from chicken farms were universally higher than those in pig and cattle farms. There was significant ability of ARGs to spread easily among different bacteria in all samples in livestock farms. Additionally, there may be more possible host bacteria of airborne ARGs in chicken farms. In the global-scale analysis of highly similar microbial communities, the database matching with the highest number of similarities to microbial communities collected from livestock farms is genes related to human sources (54.8%). This study advances our understanding of ARG dynamics in different livestock farms and contributes to the development of sustainable livestock management practices.

This study investigates the effects of beverage consumption on droplet production during coughing and speaking. Interferometric Mie imaging (IMI) measures particle size using the diffraction characteristics of light and was used to examine the particle size distribution and particle count concentration of exhaled droplets without water (WW), with still water (SW), and with carbonated water (CW). The parameters of the IMI technique were calibrated using glass beads and respiratory droplets were measured for 16 subjects, which showed that drinking beverages had a significant impact on the particle size distribution during coughing and speaking. Another important aspect of this study was the variability in particle emissions among individuals. The results showed that the consumption of SW and CW led to a significant increase in total particle count concentrations in the coughing condition when compared with WW, with no significant difference among beverage type. Individuals with relatively high particle emissions WW showed more particle generation when consuming SW and CW. When speaking, SW ingestion significantly increased the total particle count concentrations when compared with the WW condition, whereas CW consumption did not increase the total particle count concentrations to the same extent as that in the SW condition. These results emphasize that the consumption of beverages such as SW and CW have the potential to significantly increase particle production during respiratory activities, amplifying the potential risks associated with infection transmission.

Accurate measurements of cloud condensation nuclei (CCN) activity and hygroscopicity of black carbon (BC)-containing particles are particularly important because of the positive climate forcing from these particles. Such measurements are typically conducted on particles selected by a Differential Mobility Analyzer (DMA), which in addition to singly charged particles transmits multiply charged larger particles that have the same electrical mobility. These larger particles activate at lower supersaturations than the singly charged particles, biasing measurements and resulting in overestimation of CCN activity and hygroscopicity parameter (κ). Here, we measure the CCN activity and determine κ for different BC surrogates with electrical mobility diameters from 100 to 200 nm selected 1) only by electrical mobility with a DMA, and 2) by both electrical mobility and mass using a DMA and a Centrifugal Particle Mass Analyzer (CPMA), thus allowing selection of only singly charged particles. We demonstrate the use of the DMA-CPMA system in resolving biases caused by multiply charged particles, and we show that the effect of multiple charging on the CCN activity of the BC particles is strongly influenced by morphology dispersion, i.e., the variability due to the range of morphologies of particles that have the same electrical mobility and mass. Our findings show that electrical mobility-based methods alone are unlikely to lead to accurate results in measurements of CCN activation and hygroscopicity of BC particles, even for those with a more compact morphology.