Results and discussion

All computations have been performed on a 2.5$^\circ \times$2.5$^\circ$ grid consistent with the meteorological grid. First, we have applied the two methods to the fine sulphur concentration time series measured at the four sites (Table 1). The analysis of trajectories has revealed that there is no predominant pathway for transport to Sevettijärvi; however, there is a slight preference for transport from the Norwegian Sea. For the two sites in Southern Norway, air masses arrive predominantly from over the North Sea and the Atlantic Ocean, while at Sde Boker, Israel, transport occurs mainly from South East Europe. One would therefore expect, taking into account the geographical distribution of the sources, that fine sulphur concentrations measured at Sde Boker should be higher than for the other three sites. Indeed, Table 1 shows that the median concentration for fine sulphur at Sde Boker is almost one order of magnitude higher that at the three other sites.