(a)–(e) Circle charts from each sampling event with the area of the circle representing the samples' corresponding EC concentration
Figure 1. (a)–(e) Circle charts from each sampling event with the area of the circle representing the samples' corresponding EC concentration. The area of the circles are relative as Pallas concentrations are much lower than Tyresta (see table 1). Ordinate and coordinate scales are in metres. Crosses from Pallas 7 May 2010 correspond to samples below the detection limit.
Surface snow investigated for its elemental carbon (EC) concentration, based on a thermal–optical method, at two different sites during winter and spring of 2010 demonstrates metre scale horizontal variability in concentration. Based on the two sites sampled, a clean and a polluted site, the clean site (Arctic Finland) presents the greatest variability. In side-by-side ratios between neighbouring samples, 5 m apart, a ratio of around two was observed for the clean site. The median for the polluted site had a ratio of 1.2 between neighbouring samples. The results suggest that regions exposed to snowdrift may be more sensitive to horizontal variability in EC concentration. Furthermore, these results highlight the importance of carefully choosing sampling sites and timing, as each parameter will have some effect on EC variability. They also emphasize the importance of gathering multiple samples from a site to obtain a representative value for the area.