Distinct basin-scale-distributions of aluminum, manganese, cobalt, and lead in the North Pacific Ocean

Abstract

Aluminum (Al), manganese (Mn), cobalt (Co), and lead (Pb) are key trace elements in seawater and thus significant in chemical oceanography research. However, although all of these elements are highly scavenged in the ocean, only a few studies focus on the intercomparison of their distributions. Here, we report the basin-scale and full-depth sectional distributions of these elements observed during three GEOTRACES Japan cruises in the North Pacific. We confirmed that a surface maximum of the dissolved (d) species is not a common feature for the four elements and that the d species have the lowest concentrations in the Pacific Deep Water (PDW) as compared to other oceans. The elements showed different speciations and distributions. The fraction of labile particulate (lp) species was calculated as the difference between the total dissolvable (td) species and d species. The lpM/tdM ratio, where M refers to an element, is highest for Al, at 0.66 ± 0.31 (average ± sd, n = 489), and lowest for Pb, at 0.02 ± 0.08 (n = 575). Further, the distribution of each element is uniquely related to ocean circulation. The tdAl concentration is high in the Equatorial Under Current (EUC), the North Equatorial Current (NEC), and the Lower Circumpolar Deep Water *Manuscript (LCDW). Manganese is supplied from reductive sources such as sediments on the continental shelves around the northern boundary. Cobalt is concentrated in the North Pacific Intermediate Water (NPIW) and in the Equatorial Pacific Intermediate Water (EqPIW) owing to the combined effects of supply from the continental shelves, biogeochemical cycling, and scavenging. Lead shows a subsurface maximum centered at ~35°N and ~200 m depth, implying an association with the formation of the Subtropical Mode Water (SMW) and the Central Mode Water (CMW). Although the subsurface Pb maximum in the Atlantic has diminished over the last three decades owing to the ban on leaded gasoline use, it has been sustained in the North Pacific through the growth of other anthropogenic sources in Asia and Russia. We propose that the enrichment factor of dM, defined as EF(dM) = (dM/dAl) seawater /(M/Al) upper crust , where (M/Al) upper crust is the molar ratio in upper crustal abundance, can be a good parameter for the sources. The median is 1.3  10 2 (n = 436) for EF(dMn), 3.2  10 2 (n = 430) for EF(dCo), and 1.2  10 3 (n = 413) for EF(dPb). The (dPb) found in this study is on the same order of magnitude as the EF values for aerosols found in the literature, suggesting that the deposition of aerosols is a major source for dPb. EFBecause EF(dMn) and EF(dCo) are ten to hundred times higher than the EF for aerosols, sources other than the aerosol deposition are more significant contributors to the concentrations of Mn and Co.

Shelf Inputs and Lateral Transport of Mn, Co, and Ce in the Western North Pacific Ocean

“…Another set of concurrently collected samples were analyzed in 2016-2017 (USM) for dissolved La, Ce, and Pr, as part of the entire suite of rare earth elements. A 14-mL aliquot of sample (Boyle et al, 2005), Boyle MP5 = station ALOHA, 1 July 2002 (Boyle et al, 2005) (Zheng et al, 2019). dCe -IOC2002 Stn 9 = this study, Frollje 24-February-11 = station ALOHA (Fröllje et al, 2016), Frollje 21-July-12 = station ALOHA (Fröllje et al, 2016), Frollje 27-Aug-12 = station ALOHA (Fröllje et al, 2016), Frollje 1-June-13 = station ALOHA (Fröllje et al, 2016), de Baar VERTEX IV = 28…”

“…Nishioka et al (2007) suggested that material in the western North Pacific could be swept even further into the open ocean by currents circulating in this region. A recent study of three Japanese GEOTRACES cruises established the importance of margin inputs and basin-wide intermediate water masses in the distributions of dissolved Mn and Co (Zheng et al, 2019).…”

A Lagrangian View of Trace Elements and Isotopes in the North Pacific

“…(Left) dissolved Mn depth profiles from KM1513 (July 2015) shown with the mean (long dash) and fifth and 95th percentile values (short dash) of numerous dMn measurements made at Station ALOHA (Boyle et al, 2005; Chen & Wu, 2019; Morton et al, 2019) as well as several other stations in the regional North Pacific including the VERTEX‐IV (July 1983), SAFe (May 2009) and KH05‐2‐9 and KH05‐2‐8 (April 2005) (Zheng et al, 2019). Additional station locations mentioned in the text for other elements are also plotted in the map on the right.…”

“…Note the KM1513 sample from 180 m appeared contaminated for Fe (0.758 nmol/kg) and is not plotted. (Zheng et al, 2019). Additional station locations mentioned in the text for other elements are also plotted in the map on the right.…”

“…The gray, long dashed line for each is the mean profile from all measurements made a station ALOHA between 1988 and 2017. The short dashed lines are the fifth and 95th percentiles of the values within binned depth zones of the 1988-2017 dataset.10.1029/2019JC015862Journal of Geophysical Research: Oceanscarried out along 160°W in 2005(Zheng et al, 2019). We explain our relatively lower lCo near Hawaii as either (1) a function of lCo-dCo differences in the presence of elevated shelf cobalt influences from the Hawaiian Islands or (2) a function of lower cobalt supply from the Hawaiian Islands due to the farther distance (and North Pacific eddy influence) of our KM1513 sampling site.…”