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Beschreibungen/Notizen
Chemical actinometry was used to measure nitrate photolysis rate coefficients,
J
NO
3
−
, on and in snowpack at Summit, Greenland. Sealed glass tubes containing nitrate and a hydroxyl radical trapping system were buried in snow and exposed for between 2 and 24
h. Average
J
NO
3
−
values for 2-h midday exposures in early June on surface snow were 10–14×10
−7
s
−1. Averages over 24
h were 3.5–4.5×10
−7
s
−1. These values reflect the integrated photon flux and also any variation of the nitrate photolysis rate with temperature. Attenuation of
J
NO
3
−
within the firn was 0.03–0.04
cm
−1 for 24-h exposures and 0.08
cm
−1 for a 2-h exposure. Different attenuation coefficients may relate to differential light penetration due to changes in sun angle over the course of 24
h.