Iodine distribution and cycling in a beech (Fagus sylvatica) temperate forest

Atmospheric iodine, selenium and caesium depositions in France: I. Spatial and seasonal variations

“…Excluding these three sites, there was very little variation among rainfall I and Se fluxes according to climate (SI FigureS6; mean RF(I) = 13.7 ± 3.3, 11.9 ± 3.0, 8.8 ± 1.4 and 11.8 ± 1.7 g ha-1 yr-1; mean RF(Se) = 0.35 ± 0.08, 0.36 ± 0.13, 0.35 ± 0.07 and 0.33 ± 0.06; for oceanic, transition, continental and mountainous climates, respectively). Such values are in the same order of magnitude as those previously reported in Sweden and Denmark (3.4-15 g ha-1 yr-1 (2000-2006 period);Aldahan et al, 2009) and, in North-Eastern France (15.4 ± 1.7 g ha-1 yr-1 (2014-2016 period);Roulier et al, 2018) Aldahan et al (2009). also observed higher values at sites near coasts compared to inland ones.…”

Atmospheric iodine, selenium and caesium depositions in France: II. Influence of forest canopies

“…Focusing on functional types, no difference was detected between functional tree types for both CR(I) or CR(Se) (Wilcoxon test, p = 0.298 and 0.438, respectively). CR(I) values were in the same range as those found in the literature in European and Japanese forests (Neal et al, 2007;Roulier et al, 2018;Xu et al, 2016). Annual rainfall and throughfall fluxes of I varied respectively from 7.6 to 51.8 and from 8.1 to 38.1 g ha-1 yr-1 (Table 1).…”

“…Indeed, some selenium with tree canopy have been barely studied. Indeed, to date, only five publications reported measurements of stable iodine in throughfall in U.K. (Neal et al, 2007), France (Roulier et al, 2018), Germany (Epp et al, 2020) and Japan (Takeda et al, 2016;Xu et al, 2016). Similarly, studies on Se canopy exchanges are scarce (Di Tullo, 2015;Tyler and Olsson, 2006).…”

Iodine budget in forest soils: Influence of environmental conditions and soil physicochemical properties

“…On the whole, throughfall iodine fluxes were higher than corresponding rainfall iodine fluxes. This difference could be due to dry depositions as already observed (Roulier et al, 2018). Once iodine dry depositions leached by throughfall were taken into account, it appeared that iodine could be both absorbed and leached by leaves or needles.…”

“…In our previous study, we quantified annual iodine drainage flux about three times higher than total input one (i.e. throughfall + litterfall) in a beech forest (Roulier et al, 2018). In the current study, it is clear that iodine is retained in soils; however, it appears that the non-inclusion of iodine outputs from ecosystem relative to possible biomass exportation, drainage and volatilisation processes would lead to incorrect estimations (overestimation) about residence time of I in soils.…”