Snow‐borne nanosized particles: Abundance, distribution, composition, and significance in ice nucleation processes

Abstract

Physicochemical processes of nucleation constitute a major uncertainty in understanding aerosol‐cloud interactions. To improve the knowledge of the ice nucleation process, we characterized physical, chemical, and biological properties of fresh snow using a suite of state‐of‐the‐art techniques based on mass spectrometry, electron microscopy, chromatography, and optical particle sizing. Samples were collected at two North American Arctic sites, as part of international campaigns (2006 and 2009), and in the city of Montreal, Canada, over the last decade. Particle size distribution analyses, in the range of 3 nm to 10 µm, showed that nanosized particles are the most numerous (38–71%) in fresh snow, with a significant portion (11 to 19%) less than 100 nm in size. Particles with diameters less than 200 nm consistently exhibited relatively high ice‐nucleating properties (on average ranged from −19.6 ± 2.4 to −8.1 ± 2.6°C). Chemical analysis of the nanosized fraction suggests that they contain bioorganic materials, such as amino acids, as well as inorganic compounds with similar characteristics to mineral dust. The implication of nanoparticle ubiquity and abundance in diverse snow ecosystems are discussed in the context of their importance in understanding atmospheric nucleation processes.

Abundance of Biological Ice Nucleating Particles in the Mississippi and Its Major Tributaries

“…It can also be seen that the warmer-temperature-active INPs are more heat sensitive and that the effect is lost around −12 • C (Figure 2 and Figure S1); presumably, at colder temperatures INPs are a mix of heat-resistant organic and mineral INPs [12]. The size observations agree with previous work on freshwater INPs in Wales [31], marine INPs [17,20], precipitation [35][36][37], and recent studies showing that ice nucleating fungi and pollen release copious numbers of small (e.g., <15 nm) cell-free INPs [38][39][40]. (Figure 1).…”

Perspectives on the Future of Ice Nucleation Research: Research Needs and Unanswered Questions Identified from Two International Workshops

“…Similar observations are reported by Augustin-Bauditz et al [145], who investigated the ice nucleation behavior of particles consisting of a mixture of illite-NX and biological material washed of birch pollen grains. Nanometer-sized particles of biological and inorganic origin were found to be the most abundant particles in snow samples from different ecosystems [146].…”

Evidence for a missing source of efficient ice nuclei

“…We used relatively simple tests such as filtration, heat treatment, and DNA analysis as well as droplet-freezing experiments for rapid screening of biogenic submicroscale-INPs in natural rainwater samples. Rangel-Alvarado et al 21. investigated the nanosized particles present in North American snow, an important form of precipitation, and characterized their physical, chemical, and biological properties using a suite of modern laboratory techniques.…”

“…Their results illustrated that particles smaller than 200 nm are dominant and account for 38–71% all snow-borne particles. Such particles have relatively high freezing temperature, ranging on average from −19.6 ± 2.4 to −8.1 ± 2.6 °C with a mean freezing temperature of −17.2 ± 7.1 °C21. The results of chemical analysis of the nanosized fraction showed that they are mainly composed of amino acids, monomers and peptides.…”

“…However, as the atmospheric importance of INA bacteria is questionable1819, their role in the formation of clouds and precipitation in the real atmosphere has been debated. Recently, several works have attempted to investigate the quantities of INA genes20, submicroscale INA bacterial fragments16 and even nanoscale biological IN212223 to demonstrate that biological ice nuclei (IN), especially the best-known efficient IN species from the genera Pseudomonas, Erwinia, Xanthomonas and Fusarium, are widespread in the atmosphere. However, to date, the apparent contradiction between the low ratio of biological to inorganic IN and the importance of their function has not been settled.…”