Effects of particle composition on thorium scavenging in the North Atlantic

We find that model II appears to better describe the effect of particle composition on k1 than model I. Particle composition explains a larger fraction of the variance of k1 for the eastern stations (R2=0.60 for model I and 0.67 for model II) than for the western stations (R2=0.26 for model I and 0.39 for model II). When considering all stations, the variance of k1 explained by particle composition is intermediate (R2=0.50 for model I and 0.51 for model II). According to model II, the variance of k1 explained by particle composition is predominantly due to biogenic particles at the eastern stations and to Mn (oxyhydr)oxides at the western stations. Additionally, we find that particle composition does not explain a significantly different proportion of variance of k1 than particle concentration. It is thus concluded that, at our selected stations, (i) biogenic particles and Mn (oxyhydr)oxides more strongly influence Th scavenging than any other phases considered and (ii) particle composition and particle concentration have comparable effects on this process.