Title A solid-phase chemical actinometer film for measurement of solar UV penetration into snowpack
Author Rowland, G.A.; Grannas, A.M.
Author Affil Rowland, G.A., Villanova University, Department of Chemistry, Villanova, PA
Source Cold Regions Science and Technology, 66(2-3), p.75-83, . Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0165- 232X
Publication Date May 2011
Notes In English. Based on Publisher- supplied data GeoRef Acc. No: 309725
Index Terms films; instruments; measuring instruments; measurement; penetration; solid phases; temperature; ultraviolet radiation; actinometer; depth; electromagnetic radiation; intensity; photochemistry; snowpack; solid phase
Abstract A solid-phase actinometer system suitable for measuring 295-400 nm solar light intensity and penetration into snowpack has been developed and field-tested. Snow and atmospheric chemists are concerned with ultraviolet light irradiance as this spectral range has been linked to NOx and OH radical formation within snowpack. The actinometer, prepared as thin films, consists of 2- nitrobenzaldehyde (2NB) dispersed in a polymethylmethacrylate (PMMA) matrix. The concentration of 2NB at the film surface decreases due to ultraviolet light exposure and is quantified using attenuated total reflectance infrared spectroscopy (ATR-IR); either relative or absolute light intensity can be determined. The films are inexpensive, physically robust and can be easily deployed in cold-weather environments that are inhospitable to electronic instrumentation or liquid actinometer systems. Measurements of light penetration into seasonal snowpack near Barrow, Alaska, were made in 2007 and 2008. E- folding depths of 8-26 cm were observed, depending on snow conditions; alternatively, the depth of snow required to attenuate 75% of solar UV-A incident on the snowpack surface was found to range from 5 cm for aged snowpack to 15 cm for snowpacks undergoing annual melting. The variation in penetration depth is dependent on the recent history of the snowpack and is likely to determine the extent of photochemical transformations occurring within the snowpack.
URL http://hdl.handle.net/10.1016/j.coldregions.2011.01.009
Publication Type journal article
Record ID 65006376