کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4443495 | 1311195 | 2007 | 10 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Light penetration in the snowpack at Summit, Greenland: Part 2 Nitrate photolysis Light penetration in the snowpack at Summit, Greenland: Part 2 Nitrate photolysis](/preview/png/4443495.png)
Rates of photochemical reactions within the snowpack, both on snow grains and in the firn air, depend on how actinic flux is attenuated as a function of depth. This snowpack photon flux can either be measured directly (e.g., with spectral radiometers in the snow) or indirectly (e.g., by chemical actinometry where the rate of a photochemical reaction is measured). In this work we use both techniques to measure the rate constant for nitrate photolysis on water–ice, j(NO3-), on the snowpack surface and beneath at Summit, Greenland during spring and summer. The surface measurements from these two methods are generally similar ((1−2)×10–7 s−1 during midday near the summer solstice) and follow expected diurnal and annual trends. In addition, both methods show a similar effect of snow albedo on photolysis at the surface: rate constants measured on the surface snow were approximately 45% higher than values predicted for the surface based on regressions of in-snow rate constants. Average (±σσ) j(NO3-)e-folding depths (the depth along which the rate constant decreases by a factor of e) during the 2 field seasons are 10.3(±2.8) cm from actinometry tubes and 8.4(±2.4) cm from in-snow spectral radiometers.
Journal: Atmospheric Environment - Volume 41, Issue 24, August 2007, Pages 5091–5100