Number crunching (again!)

An error in some of the plots of my data has forced me to do review all my data from scratch again. Somewhere in the process of transposing, copying & formatting my data an error occurred and some of my snow data ended up as air data.

I do not have tons of data, but enough to make things difficult, when it gets messed up. Since numbers are similar (though units are not) I did not easily recognise my mistake. Now everything should be fine again, but it took a while to re-calculate all concentrations (18 compounds, 7 days of monitoring, air & snow) and plot them again.

Here is, how things look like: Toluene concentrations in snow and air at Alert in May/June 2006! Note the depletion in snow and air on May 30, which I also observed for quite a few other compounds (though not for all). I currently investigate this event using my other data and model calculations.

Estimation of VOC concentration in air from snow data

I currently work on ways to estimate concentrations of selected VOCs in air from VOC concentrations obtained in snow. This would not only give me an idea of the impact of VOC stored in snow on their occurrence in air (for data with no air samples analysed) , but would also let me compare my air and snow results, where I have both available and how the data correlate with numerical calculations.

After looking around a bit in the literature I have done some calculations using Lei & Wania’s approach (2004) with sorption coefficients for selected species compiled by Roth et al. (2004). The parameter that I miss is the specific snow surface area (SSA), which I have not measured for the data set I currently work on. However, Legagneux et al. (2002) published an extensive list of SSA for different types of snow, which they describe using images and a verbal description.

Since I have the latter information available from my snow data (including checks with a light microscope on site) I am able to estimate the SSA for my snow samples. Uncertainty data is available as well. Now that the calculations are set-up, what I need to do is optimise the estimated parameter and compare calculated results with my own data and published studies.