Fig. 2.
Hydrogeographic characteristics of the Eurasian Arctic rivers (A) and contrasting radiocarbon contents (expressed as Δ14C and conventional 14C age) of terrestrial markers compared with bulk OC in the estuarine surface sediments (B). Runoff rate = discharge/basin area. Detailed hydrogeographic data are listed in Table S1 [compiled from refs. 6, 9, 27, 52 and “watersheds of the world” (http://www.wri.org/publications)]. The ∆14C values of terrestrial markers represent concentration-weighted averages with the SEs of analytical measurement propagated. Lignin phenols refer to vanillyl and syringyl phenols (detailed data are provided in Fig. S1). Hydroxy phenols refer to p-hydroxybenzaldehyde, p-hydroxyacetophenone, and p-hydroxybenzoic acid. Plant wax lipids constitute n-alkanes (C27,29,31) and n-alkanoic acids (C24,26,28) (6).