Climate factors influencing bacterial count in background air samples

Harrison, Roy M.; Jones, Alan M.; Biggins, Peter D. E.; Pomeroy, N.P.; Cox, C. S.; Kidd, Stephen P.; Hobman, Jon L.; Brown, Nigel L.; Beswick, Alan J

doi:10.1007/s00484-004-0225-3

Cited by 127 publications

(107 citation statements)

References 29 publications

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“…between 2 and 32 • C; see Caristi et al, 1991); and (2) the drying period after precipitation has fallen at the ground. Average concentrations of airborne bacteria were seen to increase exponentially with temperature in the UK by Harrison et al (2005), and to depend on average wind speed. Turbulence and convection in the planetary boundary layer (PBL) may influence emissions.…”

Section: Discussionmentioning

confidence: 99%

Potential impacts from biological aerosols on ensembles of continental clouds simulated numerically

et al. 2009

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Abstract. An aerosol-cloud modeling framework is described to simulate the activation of ice particles and droplets by biological aerosol particles, such as airborne icenucleation active (INA) bacteria. It includes the empirical parameterisation of heterogeneous ice nucleation and a semi-prognostic aerosol component, which have been incorporated into a cloud-system resolving model (CSRM) with double-moment bulk microphysics. The formation of cloud liquid by soluble material coated on these partially insoluble organic aerosols is represented. It determines their partial removal from deep convective clouds by accretion onto precipitation in the cloud model. This "aerosol-cloud model" is validated for diverse cases of deep convection with contrasting aerosol conditions, against satellite, ground-based and aircraft observations.Simulations are performed with the aerosol-cloud model for a month-long period of summertime convective activity over Oklahoma. It includes three cases of continental deep convection simulated previously by Phillips and . Elevated concentrations of insoluble organic aerosol, boosted by a factor of 100 beyond their usual values for this continental region, are found to influence significantly the following quantities: (1) the average numbers and sizes of ice crystals and droplets in the clouds; (2) the horizontal cloud coverage in the free troposphere; (3) preCorrespondence to: V. T. J. Phillips (vaughanp@hawaii.edu) cipitation at the ground; and (4) incident solar insolation at the surface. This factor of 100 is plausible for natural fluctuations of the concentration of insoluble organic aerosol, in view of variability of cell concentrations for airborne bacteria seen by Lindemann et al. (1982).In nature, such boosting of the insoluble organic aerosol loading could arise from enhanced emissions of biological aerosol particles from a land surface. Surface wetness and solar insolation at the ground are meteorological quantities known to influence rates of growth of certain biological particles (e.g. bacteria). Their rates of emission into the atmosphere must depend on these same quantities, in addition to surface wind speed, turbulence and convection. Finally, the present study is the first attempt at evaluating the impacts from biological aerosols on mesoscale cloud ensembles in the literature.

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Section: Discussionmentioning

confidence: 99%

Potential impacts from biological aerosols on ensembles of continental clouds simulated numerically

et al. 2009

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“…For example, Harrison et al estimated the average bacterial cell concentration in near-surface air over coastal ecosystems to be 7.6 × 10 4 cells m −3 (33). Bacterial cell concentration in the cloud-free, high-altitude sample collected during the GRIP campaign based on our microscopy-based counts is about twofold lower (it is also likely that the real difference is even greater because the methods used in the previous study are more comparable to our qPCR than the microscopy methods).…”

Section: Discussionmentioning

confidence: 99%

Microbiome of the upper troposphere: Species composition and prevalence, effects of tropical storms, and atmospheric implications

DeLeon-Rodriguez¹,

Lathem²,

Rodriguez-R³

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

376

304

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The composition and prevalence of microorganisms in the middle-toupper troposphere (8-15 km altitude) and their role in aerosol-cloudprecipitation interactions represent important, unresolved questions for biological and atmospheric science. In particular, airborne microorganisms above the oceans remain essentially uncharacterized, as most work to date is restricted to samples taken near the Earth's surface. Here we report on the microbiome of low-and high-altitude air masses sampled onboard the National Aeronautics and Space Administration DC-8 platform during the 2010 Genesis and Rapid Intensification Processes campaign in the Caribbean Sea. The samples were collected in cloudy and cloud-free air masses before, during, and after two major tropical hurricanes, Earl and Karl. Quantitative PCR and microscopy revealed that viable bacterial cells represented on average around 20% of the total particles in the 0.25-to 1-μm diameter range and were at least an order of magnitude more abundant than fungal cells, suggesting that bacteria represent an important and underestimated fraction of micrometer-sized atmospheric aerosols. The samples from the two hurricanes were characterized by significantly different bacterial communities, revealing that hurricanes aerosolize a large amount of new cells. Nonetheless, 17 bacterial taxa, including taxa that are known to use C1-C4 carbon compounds present in the atmosphere, were found in all samples, indicating that these organisms possess traits that allow survival in the troposphere. The findings presented here suggest that the microbiome is a dynamic and underappreciated aspect of the upper troposphere with potentially important impacts on the hydrological cycle, clouds, and climate.ice nucleation | cloud condensation nuclei | microbial community | pyrosequencing | biogeography

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“…The key issue with the method is the need for a minimum number of particles per sample (10 4 L −1 ; Gandolfi et al, 2013) and therefore an appropriate amount of sampled air. At rural sites, Bowers et al (2011) were able to employ epifluorescence sampling at 30 L min −1 for 1.5 h, while Harrison et al (2005) worked with high-volumetric sampling at 1000 L min −1 for 6 h at a time. Such timescales are not suitable for flux-gradient applications, for which fluctuations in concentrations must be resolvable on a timescale appropriate for the planetary boundary layer response time (≤ 1 h).…”

Section: Discussionmentioning

confidence: 99%

Measurements and modeling of surface–atmosphere exchange of microorganisms in Mediterranean grassland

et al. 2017

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Abstract. Microbial aerosols (mainly composed of bacterial and fungal cells) may constitute up to 74 % of the total aerosol volume. These biological aerosols are not only relevant to the dispersion of pathogens, but they also have geochemical implications. Some bacteria and fungi may, in fact, serve as cloud condensation or ice nuclei, potentially affecting cloud formation and precipitation and are active at higher temperatures compared to their inorganic counterparts. Simulations of the impact of microbial aerosols on climate are still hindered by the lack of information regarding their emissions from ground sources. This present work tackles this knowledge gap by (i) applying a rigorous micrometeorological approach to the estimation of microbial net fluxes above a Mediterranean grassland and (ii) developing a deterministic model (the PLAnET model) to estimate these emissions on the basis of a few meteorological parameters that are easy to obtain. The grassland is characterized by an abundance of positive net microbial fluxes and the model proves to be a promising tool capable of capturing the day-to-day variability in microbial fluxes with a relatively small bias and sufficient accuracy. PLAnET is still in its infancy and will benefit from future campaigns extending the available training dataset as well as the inclusion of ever more complex and critical phenomena triggering the emission of microbial aerosol (such as rainfall). The model itself is also adaptable as an emission module for dispersion and chemical transport models, allowing further exploration of the impact of landcover-driven microbial aerosols on the atmosphere and climate.

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Climate factors influencing bacterial count in background air samples

Cited by 127 publications

References 29 publications

Potential impacts from biological aerosols on ensembles of continental clouds simulated numerically

Potential impacts from biological aerosols on ensembles of continental clouds simulated numerically

Microbiome of the upper troposphere: Species composition and prevalence, effects of tropical storms, and atmospheric implications

Measurements and modeling of surface–atmosphere exchange of microorganisms in Mediterranean grassland

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