3.3 Seasonal changes of TE export
The individual TE fluxes varied by almost 7 orders of magnitude (Figure 5). The highest flux was recorded for Al with a maximum of 160 µmol m-2 d-1 and the lowest for Th with a minimum of 3.5 x 10-2 nmol m-2d-1. Examination of the seasonal changes revealed two qualitatively different temporal patterns. High export fluxes of P, Cd, Ba, Mo, Cu, Ni and V were associated with one or both of the main export events described in the previous section. For most of these elements, the export fluxes were higher during the first than during the second event, but more subtle differences appear. For example, the flux of Cd export was much more pronounced during the first than the second event, whereas for V the fluxes were almost identical during both events. For the other elements (Y, Mn, Zr, Co, Ti, Cr, Th, Fe and Al) the highest fluxes were measured in the first cups (#1 to #5) and the lowest in the remaining cups (#6 to #12).
For TE fluxes, a PCA confirms the partitioning between the two main groups mentioned in the previous section based on the qualitative analysis of the seasonal changes (Figure 6). The two first components of the PCA explain 98.2 % of the seasonal variation of the TE export. For PC1, positive scores correspond to the beginning of the season (#1 to #5) and negative scores to the remaining cups (#6 to #12). The highest positive scores for the PC2 are typical of cups corresponding to the two export events (#4 #5 and #9 #10). Within the group of elements characterised by two marked peaks of export (P, Cd, Ba, Mo, Cu, Ni and V), the PCA shows three possible subgroups where seasonal variations of these elements are highly correlated. These consist of P, Cd and Ba, then Mo and Cu, and finally Ni and V (Figure S2).