Particulate fluxes of 230Th, 231Pa, and 10Be in the northeastern Pacific Ocean

Transport and burial rates of10Be and231Pa in the Pacific Ocean during the Holocene period

“…The results of previous studies [9,10] and our work [23][24][25] have shown that l°Be is also preferentially removed from the oceans in some margin areas. In order to evaluate the source of l°Be, and to understand its transport within the oceans, we need to conduct an ocean-wide study: (1) to estimate the extent to which l°Be deposition is enhanced in different ocean margin regions; and (2) to examine what factors influence the scavenging of l°Be from seawater to sediments.…”

“…The techniques used for analyses of the radionuclides have been described in detail elsewhere [24]. The initial (i.e., decay corrected) unsupported concentrations of 23°Th and 231pa (des-230 231~ ignated as xs Tho and xs rao, respectively; Table 2), were calculated based methods described previously [23,24].…”

“…The initial (i.e., decay corrected) unsupported concentrations of 23°Th and 231pa (des-230 231~ ignated as xs Tho and xs rao, respectively; Table 2), were calculated based methods described previously [23,24]. The basic principle of our approach is to use 23°Th, a nuclide that is produced uniformly throughout the ocean by decay of dissolved 234U and deposited to the sea floor at a rate nearly equal to its production rate in the overlying water column, as a tracer against which 231pa and l°Be are normalized so that 231pa/Ea°Th and l°Be/23°Th ratios in the sediments can be used as indicators of the intensity of scavenging of 231pa and l°Be (see [23] for a description of the normalization and the assumptions implicit therein; and also discussions in Section 3 below).…”

“…Since the rate of removal of 23°Th from seawater is relatively uniform throughout the ocean [18,19,22], a Pa/Th ratio in the sediment greater than the production ratio of 0.093 indicates that the site is a sink for 231pa (relative to 23°Th), receiving an extra amount of 231pa in addition to the 23apa produced in the overlying water column. Conversely, if the ratio is less than the production ratio, the site acts as a source with a certain fraction of 231pa produced in the overlying water column being laterally exported (relative to 230Th) to other area(s) in the ocean [23,24].…”

Opal burial in the equatorial Atlantic Ocean over the last 30 ka: Implications for glacial‐interglacial changes in the ocean silicon cycle

“…Protactinium has a longer residence time than thorium, however [Anderson et al, 1983a[Anderson et al, , 1983b, so it can be transported over basin-scale distances before being removed. Therefore Pa tends to be removed in areas of higher scavenging, or areas with higher particle flux [Taguchi et al, 1989;Lao et al, 1992Lao et al, , 1993, and the 231 Pa/ 230 Th ratio on particles and in sediments tends to increase with increasing particle flux. Protactinium also has a particular affinity for sorption to opal over other particle compositions [Anderson et al, 1983a], and it seems that sedimentary 231 Pa/ 230 Th ratios in open ocean regions with low fluxes of particulate lithogenic material are primarily dictated by the opal/CaCO 3 ratio of the particulate matter, with total particle flux being a secondary contributor [Chase et al, 2002].…”