Soluble, light-absorbing species in snow at Barrow, Alaska

For light absorption in the photochemically active region (300-450 nm) of surface snows, H₂O₂ and NO₃⁻ make minor contributions (combined < 9% typically), while HUmic LIke Substances (HULIS) and unknown chromophores each account for approximately half of the total absorption.

We have identified four main sources for our residual chromophores (i.e., species other than H₂O₂ or NO₃⁻): (1) vegetation and organic debris impact mostly the lowest 20 cm of the snowpack, (2) marine inputs, which are identified by high Cl⁻ and SO₄²⁻ contents, (3) deposition of diamond dust to surface snow, and (4) gas-phase exchange between the atmosphere and surface snow layers. The snow surfaces, and accompanying chromophore concentrations, are strongly modulated by winds and snowfall at Barrow.