Formaldehyde in Arctic snow. Incorporation into ice particles and evolution in the snowpack

Formaldehyde was measured in the seasonal snowpack near Alert (Ellesmere Island 82.5°N, 62.3°W) during both winter and spring campaigns of ALERT2000. The time evolution of formaldehyde (HCHO) concentrations in fresh snow was monitored. Since snow metamorphism induces evaporation and condensation of both ice and its solutes, the evolution of snow microphysics was also studied. Simultaneous monitoring of the partial pressures of HCHO allowed the estimation of the partitioning of HCHO between the snowpack and the atmosphere. Assuming exchange layer thicknesses of 300 and 14 m during winter and spring, respectively, we calculated that over 80% of the total amount of HCHO in the (exchange layer+snow) system was in the snowpack. Snow is thus an important potential source of HCHO to the atmosphere. The mechanism of incorporation of HCHO in snow crystals must be known to understand its kinetics of exchange with the atmosphere. Tests were performed to determine whether HCHO was adsorbed on the ice surface, or dissolved in the ice crystalline lattice.