High Relative Humidity as a Trigger for Widespread Release of Ice Nuclei

Wright, Timothy P.; Hader, John D.; McMeeking, G. R.; Petters, M. D.

doi:10.1080/02786826.2014.968244

Cited by 71 publications

(81 citation statements)

References 47 publications

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“…For the study reported here, only the FP3 definition was used for comparison, because Wright et al (2014) postulated the category as being enriched with fungal spores during their ambient study and because they observed that these particles scaled more tightly with observed ice nucleating particles. The authors classified a particle in the FP3 category if the fluorescence intensity in FL1 > 1900 arbitrary units (a.u.…”

Section: Wibs Data Analysismentioning

confidence: 99%

“…Stacked particle type size distributions for representative particle classes shown using four separate thresholding strategies. NF+ particle type (right-most column) represents particles that exceed the FL2 and/or FL3 upper bound of the Wright et al (2014) FP3 definition and that are therefore considered as one set of "non-fluorescent" particles by that definition. Legend above top rows indicate threshold definition used.…”

Section: Fluorescence Threshold Defines Particle Typementioning

confidence: 99%

“…For example, Wright et al (2014) used set fluorescence intensity value boundaries rather than using the standard Gabey et al (2010) definition that applies a threshold as a function of observed background fluorescence. The Wright et al (2014) study proposed five separate categories of fluorescent particles (FP1 through FP5). Each definition was determined by selecting criteria for excitation-emission boundaries and observing the empirical distribution of particles in a three-dimensional space (FL1 vs. FL2 vs. FL3).…”

Section: Wibs Data Analysismentioning

confidence: 99%

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Systematic characterization and fluorescence threshold strategies for the wideband integrated bioaerosol sensor (WIBS) using size-resolved biological and interfering particles

et al. 2017

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Abstract. Atmospheric particles of biological origin, also referred to as bioaerosols or primary biological aerosol particles (PBAP), are important to various human health and environmental systems. There has been a recent steep increase in the frequency of published studies utilizing commercial instrumentation based on ultraviolet laser/light-induced fluorescence (UV-LIF), such as the WIBS (wideband integrated bioaerosol sensor) or UV-APS (ultraviolet aerodynamic particle sizer), for bioaerosol detection both outdoors and in the built environment. Significant work over several decades supported the development of the general technologies, but efforts to systematically characterize the operation of new commercial sensors have remained lacking. Specifically, there have been gaps in the understanding of how different classes of biological and non-biological particles can influence the detection ability of LIF instrumentation. Here we present a systematic characterization of the WIBS-4A instrument using 69 types of aerosol materials, including a representative list of pollen, fungal spores, and bacteria as well as the most important groups of non-biological materials reported to exhibit interfering fluorescent properties. Broad separation can be seen between the biological and non-biological particles directly using the five WIBS output parameters and by taking advantage of the particle classification analysis introduced by Perring et al. (2015). We highlight the importance that particle size plays on observed fluorescence properties and thus in the Perring-style particle classification. We also discuss several particle analysis strategies, including the commonly used fluorescence threshold defined as the mean instrument background (forced trigger; FT) plus 3 standard deviations (σ ) of the measurement. Changing the particle fluorescence threshold was shown to have a significant impact on fluorescence fraction and particle type classification. We conclude that raising the fluorescence threshold from FT + 3σ to FT + 9σ does little to reduce the relative fraction of biological material considered fluorescent but can significantly reduce the interference from mineral dust and other non-biological aerosols. We discuss examples of highly fluorescent interfering particles, such as brown carbon, diesel soot, and cotton fibers, and how these may impact WIBS analysis and data interpretation in various indoor and outdoor environments. The performance of the particle asymmetry factor (AF) reported by the instrument was assessed across particle types as a function of particle size, and comments on the reliability of this parameter are given. A comprehensive online supplement is provided, which includes size distributions broken down by fluorescent particle type for all 69 aerosol materials and comparing threshold strategies. Lastly, the study was designed to propose analysis strategies that may be useful to the broader community of UV-LIF instrumentation users in order to promote deeper discussions about how best to continue i...

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Section: Wibs Data Analysismentioning

confidence: 99%

Section: Fluorescence Threshold Defines Particle Typementioning

confidence: 99%

Section: Wibs Data Analysismentioning

confidence: 99%

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Systematic characterization and fluorescence threshold strategies for the wideband integrated bioaerosol sensor (WIBS) using size-resolved biological and interfering particles

et al. 2017

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“…Recently there has been a resurgence of related research, with the general aims of correlating abundances of organic INPs in the boundary layer with local ecotypes (Prenni et al, 2009;Bowers et al, 2010;Garcia et al, 2012;Tobo et al, 2013;Mason et al, 2015), gauging the stimulation of their release by humidity, rainfall, and harvesting (Garcia et al, 2012;Huffman et al, 2013;Prenni et al, 2013;Wright et al, 2014;Bigg et al, 2015), and measuring organic INP abundance in clouds and precipitation (Christner et al, 2008;Delort et al, 2010;Joly et al, 2014;Monteil et al, 2014;Morris et al, 2008;Petters and Wright, 2015;Šantl-Temkiv et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Sources of organic ice nucleating particles in soils

et al. 2016

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Abstract. Soil organic matter (SOM) may be a significant source of atmospheric ice nucleating particles (INPs), especially of those active > −15 • C. However, due to both a lack of investigations and the complexity of the SOM itself, the identities of these INPs remain unknown. To more comprehensively characterize organic INPs we tested locally representative soils in Wyoming and Colorado for total organic By contrast, lysozyme, which digests bacterial cell walls, only reduced INPs active at ≥ −7.5 or ≥ −6 • C, depending on the soil. The known IN bacteria were not detected in any soil, using PCR for the ina gene that codes for the active protein. We directly isolated and photographed two INPs from soil, using repeated cycles of freeze testing and subdivision of droplets of dilute soil suspensions; they were complex and apparently organic entities. Ice nucleation activity was not affected by digestion of Proteinase K-susceptible proteins or the removal of entities composed of fulvic and humic acids, sterols, or aliphatic alcohol monolayers. Organic INPs active colder than −10 to −12 • C were resistant to all investigations other than heat, oxidation with H 2 O 2 , and, for some, digestion with papain. They may originate from decomposing plant material, microbial biomass, and/or the humin component of the SOM. In the case of the latter then they are most likely to be a carbohydrate. Reflecting the diversity of the SOM itself, soil INPs have a range of sources which occur with differing relative abundances.

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“…Several recent studies have employed a binary yes-no classification of fluorescence above a threshold (e.g., Gabey et al, 2010;Perring et al, 2015), essentially ignoring the fluorescence magnitude beyond the threshold. Fluorescence magnitudes have been used as input variables in automated particle-clustering analyses (Robinson et al, 2013;Crawford et al, 2015) and to manually sort sampled particles into groupings (Wright et al, 2014). Particles emitting so much fluorescence as to saturate detectors are sometimes excluded from analysis (e.g., Toprak and Schnaiter, 2013), and relatively weak fluorescence has been proposed as a possible discriminator of interfering nonbiological particles (Hill et al, 1999;Crawford et al, 2014Crawford et al, , 2016Yu et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Fluorescence calibration method for single-particle aerosol fluorescence instruments

et al. 2017

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Abstract. Real-time, single-particle fluorescence instruments used to detect atmospheric bioaerosol particles are increasingly common, yet no standard fluorescence calibration method exists for this technique. This gap limits the utility of these instruments as quantitative tools and complicates comparisons between different measurement campaigns. To address this need, we have developed a method to produce size-selected particles with a known mass of fluorophore, which we use to calibrate the fluorescence detection of a Wideband Integrated Bioaerosol Sensor (WIBS-4A). We use mixed tryptophan-ammonium sulfate particles to calibrate one detector (FL1; excitation = 280 nm, emission = 310-400 nm) and pure quinine particles to calibrate the other (FL2; excitation = 280 nm, emission = 420-650 nm). The relationship between fluorescence and mass for the mixed tryptophan-ammonium sulfate particles is linear, while that for the pure quinine particles is nonlinear, likely indicating that not all of the quinine mass contributes to the observed fluorescence. Nonetheless, both materials produce a repeatable response between observed fluorescence and particle mass. This procedure allows users to set the detector gains to achieve a known absolute response, calculate the limits of detection for a given instrument, improve the repeatability of the instrumental setup, and facilitate intercomparisons between different instruments. We recommend calibration of single-particle fluorescence instruments using these methods.

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High Relative Humidity as a Trigger for Widespread Release of Ice Nuclei

Cited by 71 publications

References 47 publications

Systematic characterization and fluorescence threshold strategies for the wideband integrated bioaerosol sensor (WIBS) using size-resolved biological and interfering particles

Systematic characterization and fluorescence threshold strategies for the wideband integrated bioaerosol sensor (WIBS) using size-resolved biological and interfering particles

Sources of organic ice nucleating particles in soils

Fluorescence calibration method for single-particle aerosol fluorescence instruments

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