Transformations of snow chemistry in the boreal forest: accumulation and volatilization

Impacts of anthropogenic emissions and cold air pools on urban to montane gradients of snowpack ion concentrations in the Wasatch Mountains, Utah

“…These differences may reflect the partial success of emissions regulations in decreasing atmospheric particulates over this time period (Whiteman et al, 2014). Low particulate matter concentrations characteristic of remote montane regions may explain the absence of measurable dry ionic snowpack deposition reported in previous studies (Williams and Melack, 1991;Pomeroy et al, 1999;Williams et al, 2009). It is important to note that although our surface snow measurements focused on sites in close proximity to urban Salt Lake City, high concentrations of urban-derived particulate matter extended into significant portions of adjacent montane canyons (Fig.…”

“…In particular, nitrogen (N) inputs from atmospheric deposition can contribute to undesired increases in productivity, species changes, and aquatic eutrophication, especially in seasonally snow-covered environments where nutrients rapidly elute during melting (Jeffries, 1990;Williams and Tonnessen, 2000;Baron et al, 2011). Many studies of snow chemical composition over the past three decades have explicitly avoided measurements of urban emission hot-spots (Jeffries, 1990;Nickus et al, 1997), instead focusing on remote wilderness sites (Williams and Melack, 1991;Pomeroy et al, 1999;Kang et al, 2004;Williams et al, 2009). Cities often exhibit higher ion concentrations and fluxes in rainfall and dry deposition relative to adjacent areas, with trends varying among chemical species (e.g.…”

“…Dry and fog deposition of gases and particles to snowcovered surfaces have previously been shown to comprise relatively minor sources of ions in comparison with snowfall (Bergin et al, 1995;Bj€ orkman et al, 2013). Rather, net losses of NO 3 À from the snowpack between precipitation events can be significant (Williams and Melack, 1991;Pomeroy et al, 1999;Williams et al, 2009). However, this subject has received little attention in urban environments, where elevated aerosol concentrations during cold air pools could enhance dry or cloud deposition in addition to wet deposition, and yield ecologically significant fluxes of ions to the snowpack.…”

Snow physics as relevant to snow photochemistry

“…It therefore appears likely that the multi-phase photochemical activity of soils will be severely limited by their efolding depth, while that of forests will be limited by the low LAI values, except perhaps when snow is present on trees (Pomeroy et al, 1999). Snowpacks have intermediate permeability, SAI and e-folding depth values and therefore appear good candidates to be efficient multi-phase photochemical reactors.…”

Variability of black carbon deposition to the East Antarctic Plateau, 1800–2000 AD

“…Comparison of the records at annual resolution revealed no significant cross-correlations, including for sites 08-4 and 08-5, which were within 17 km of each other. We conclude that surface processes (accumulation rate variability, sastrugi, blowing snow, and snow sublimation) prevent the analysis of rBC signal at annual time scales and restrain the resolution to interannual/decadalscales (Pomeroy et al, 1999). Decadal-scale variability was investigated using singular spectrum analysis non-linear trend reconstruction (Ghil et al, 2002).…”