Ultraviolet germicidal irradiation of melted snow and ice samples: inactivation of microorganisms and effects on insoluble microparticles

Fumio Nakazawa,Kumiko Goto-Azuma

doi:10.1017/jog.2021.78

Abstract

AbstractThe long-term refrigerated storage of melted snow and/or ice samples for analyses of insoluble microparticles (hereafter, microparticles) may be limited by increases in the biological particle concentration caused by microbial growth after ~1–2 weeks. In this study, we examined an ultraviolet (UV) disinfection method for the storage of melted snow and/or ice samples and determined the effects of this method on microparticles. Surface snow obtained from Glacier No. 31 in the Suntar-Khayata Range, eastern Siberia, Russia was divided into two portions for UV treatment and untreated controls. Microparticle concentrations and size distributions (in the range of 0.52–12.0 μm) in the samples were measured using a Coulter counter. Whereas the microparticle concentration in untreated samples increased, no obvious increase was observed over 53 d in the samples subjected to UV treatment. Microbial growth was detected in only untreated samples using a viable particle counter. In addition, the original microparticle concentrations and size distributions were unaffected by UV treatment. Our results demonstrated that the microparticle size distribution in untreated melted water samples reflects the growth, decomposition and succession of microorganisms over time and further indicate that UV irradiation is effective for long-term storage for microparticle analysis.

Highlights

Insoluble microparticles in polar ice cores are predominantly dust transported over long distances from terrestrial regions to the polar ice sheets and have been analyzed as a proxy for terrestrial environmental changes in ice core studies (e.g. Petit and others, 1981, 1999; Thompson and Mosley-Thompson, 1981; Fujii and others, 2003; Lambert and others, 2008)
In our laboratory, counting and size analysis of microparticles in snow and ice-core samples are carried out using a laser particle counter (Model-211; Met One Inc., Grand Pass, OR, USA), which is a type of light-scattering liquid-borne particle counter (LSLPC), and a Coulter counter (Multisizer 4e; Beckman Coulter, Brea, CA, USA)
UV disinfection was evaluated for the long-term storage of melted snow and ice samples from glaciers in a refrigerator

Summary

Introduction

Insoluble microparticles (hereafter, microparticles) in polar ice cores are predominantly dust transported over long distances from terrestrial regions to the polar ice sheets and have been analyzed as a proxy for terrestrial environmental changes in ice core studies (e.g. Petit and others, 1981, 1999; Thompson and Mosley-Thompson, 1981; Fujii and others, 2003; Lambert and others, 2008). This storage protocol is based on a study by Miyake and others (2014), who compared various procedures for preservation and microparticle analyses They found that melted water samples from the Dome Fuji ice core (Antarctica) stored in a glass bottle and refrigerated for 1 year showed no obvious change in microparticle concentration measured using a laser particle counter. The purposes of this study were (1) to confirm the effect of UV disinfection and investigate its influence on the number and size distribution of microparticles in melted snow and ice samples, (2) to evaluate temporal variation in the size distribution of microparticles, reflecting the activity of microorganisms, in untreated samples, and (3) to compare the use of LSLPC and Coulter counter for analyses of biological particles in samples

Study area and methods

Changes in the microparticle concentration

Changes in the microparticle size distribution

Measurement with a viable particle counter

Conclusion