Ubiquity of Biological Ice Nucleators in Snowfall

Abstract

Despite the integral role of ice nucleators (IN) in atmospheric processes leading to precipitation, their sources and distributions have not been well established. We examined IN in snowfall from mid- and high-latitude locations and found that the most active were biological in origin. Of the IN larger than 0.2 micrometer that were active at temperatures warmer than -7 degrees C, 69 to 100% were biological, and a substantial fraction were bacteria. Our results indicate that the biosphere is a source of highly active IN and suggest that these biological particles may affect the precipitation cycle and/or their own precipitation during atmospheric transport.

Immersion freezing of ice nucleation active protein complexes

“…However, even data concerning the number of ice nucleating bacteria per droplet or volume of precipitation is still sparse as already mentioned in the Introduction. Looking into densities of total bacterial IN larger than 0.2 µm in precipitation, Christner et al (2008) found between 4 and 120 bacterial IN per litre of precipitation. Also in precipitation, two studies have found that between 2 % and 19 % of bacteria, which could be cultivated under laboratory conditions, were INA (Stephanie and Waturangi, 2011;Šantl-Temkiv et al, 2013).…”

“…However, species belonging to Pseudomonas have often been found dominant among bacteria from fog and cloud water (Fuzzi et al, 1997;Amato et al, 2006;Ahern et al, 2007). Christner et al (2008) reported that about 0.4 % of bacterial cells in snowfall were ice nucleating active between −4 • C and −7 • C. Morris et al (2008) found that P. syringae was ubiquitously present in precipitation and freshwater and has suggested that INA bacteria are being disseminated as part of the water cycle. And most recently, DeLeon-Rodriguez et al (2013) found that in particle samples from the middle to upper troposphere around 20% of the total particles in the diameter range from 250 nm to 1 µm were viable bacterial cells, and based on that they claim that bacteria are an important and underestimated fraction of micrometer-sized atmospheric aerosol particles.…”

The accurate calculation of the band gap of liquid water by means of GW corrections applied to plane-wave density functional theory molecular dynamics simulations

“…5 The variations of OÁ Á ÁH ordering in the tetragonal coordination create dozens of ice phases, which at present are still under discussion. [5][6][7][8][9][10][11][12] Obviously, there is no long-range ordering in liquid water. However, at short-range the structure of water is topologically the same as those of ice, but with flexible bond-lengths and angles of H 2 O tetragons.…”

“…From the measured real and imaginary parts of the index of refraction and dielectric constant, the authors suggested an exciton transition at 8.3 eV, an interband transition at 9.6 eV, and an electronic band gap of 9.0 eV. 16 Other measurements of photoemission spectra provide a range of values for the band gap of water; 6.9 eV, 21,22 7.0, 23 8.7 eV, 24 8.9 eV 25 and 9.0 eV. 16 As reviewed by Winter and co-workers, such a variance in experimental data for the insulating ice phases and water is caused by many factors, such as electric charging, work functions, surface sensitivity (electron escape depths are typically B10-20 Å), vapour-solid or vapour-liquid mixing, impurities, etc.…”

Fungi diversity in PM<sub>2. 5</sub> and PM<sub>1</sub> at the summit of Mt. Tai: abundance, size distribution, and seasonal variation

“…They can actively metabolize in the atmosphere with their mass concentrations ranging from 5.49 to 102 ng m −3 (Zhong et al, 2016). Furthermore, they play an important role in agriculture, the biosphere, cloud formation, global climate, and atmospheric dynamics (Brodie et al, 2007;Despres et al, 2012;Christner et al, 2008;Zhou et al, 2014;Jaenicke et al, 2005). Fungi, the primary group of PBAPs, include 1.5 million unique species, distributed across rural and urban environments (Hawksworth et al, 2001).…”