Distribution and stoichiometry of Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in the East China Sea
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ORIGINAL ARTICLE
Distribution and stoichiometry of Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in the East China Sea Yuzuru Nakaguchi1 · Yoshinori Ikeda2 · Atsushi Sakamoto2 · Linjie Zheng3 · Tomoharu Minami4 · Yoshiki Sohrin3 Received: 31 August 2020 / Revised: 26 October 2020 / Accepted: 27 October 2020 © The Oceanographic Society of Japan and Springer Nature Singapore Pte Ltd. 2020
Abstract The dissolved (d) and total dissolvable (td) trace metals were determined in seawater samples collected from the East China Sea (ECS). Labile particulate (lp) species was calculated as td minus d, and the sectional and vertical distributions of d and lp trace metals were evaluated. The surface concentrations of dAl, dCo, dNi, dCu, and dPb were higher in the continental shelf region than in the Kuroshio region. lpAl and lpFe were the dominant species below a depth of 400 m, and a strong positive correlation was observed between them in the Kuroshio region. The enrichment factor (EF) against crustal abundance was calculated for the purpose of estimating the origin of dMs in the ECS. The EF(dFe) was close to unity. These results suggest that both lpFe and dFe are dominated by crustal sources. The other elements had high EF, indicating significant contributions from other sources. EF(dPb) was close to the enrichment factor in aerosol, suggesting atmospheric input from anthropogenic sources. The dM/P ratios were calculated to investigate the validity of the extended Redfield ratio in the ECS. The Mn/P, Co/P, Cu/P, Zn/P, and Cd/P ratios in shallow water ( 400 m; those for AND 22 were 0.23 ± 0.27 (n = 9) at ≤ 400 m and 0.91 ± 0.05 (n = 6) at > 400 m; those for AND 26 were 0.57 ± 0.26 (n = 8) at ≤ 100 m; those for AND 31 were 0.08 ± 0.07 (n = 8) at ≤ 400 m and 0.85 ± 0.11 (n = 5)
Distribution and stoichiometry of Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in the East China Sea
at > 400 m; and those for AND 34 were 0.13 ± 0.07 (n = 9) at ≤ 400 m and 0.82 ± 0.05 (n = 8) at a depth of > 400 m. These results indicate that lpAl was the dominant species of Al at a depth of > 400 m at any of the sampling stations.
4.3 Mn The full-depth vertical profiles of dMn and lpMn are shown in Figs. 5b and 7b, respectively. The sectional distributions of dMn and lpMn are shown in Figs. 6b and 8b, respectively. The concentration ranges of dMn and lpMn at AND 26, in the continental shelf region, were 2.06–2.92 and 1.28–49.3 nmol/kg, respectively. These concentrations of Mn at AND 26 were substantially higher than those in the Kuroshio region in a similar manner to Al. The concentration ranges of dMn and lpMn in the Kuroshio
region (AND 06, 22, 31, and 34) were 0.30–7.48 and ND–11.9 nmol/kg, respectively. The vertical profiles of dMn exhibited a scavenging profile, which are similar to those observed in the North Pacific (Bruland et al 1994; Zheng et al. 2019) and the Atlantic Ocean (Saager et al. 1997). However, the concentrations of dMn and lpMn increased sharply at the bottom layer at AND 22 and 31. The sources of dMn may be attributed to manganese
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