Geochemical behavior of dissolved manganese in the East China Sea: Seasonal variation, estuarine removal, and regeneration under suboxic conditions

Abstract

To better understand the geochemical cycle of dissolved manganese (Mn) in the East China Sea (ECS), the distribution of dissolved Mn across the ECS was investigated during three field studies in 2011 (May, August, and November). The concentration of dissolved Mn decreased across the ECS with distance from the coast. Mn‐rich ECS shelf waters could export to the Kuroshio Waters, and had the potential to influence the northwest Pacific Ocean as well as the Japan Sea. The Kuroshio Waters were devoid of dissolved Mn, so its incursion could be tracked as it entered the ECS continental shelf region (approximately 50 m isobath). Seasonal variations of dissolved Mn in the ECS were significant, with the highest concentrations occurring in summer. Dissolved Mn in the Changjiang Estuary was nonconservative, and significant quantities were removed by net sorption onto suspended particulate matter. A model describing the sorption processes was applied to data for the Changjiang Estuary. Regeneration of dissolved Mn took place in near‐bottom waters of the suboxic zone in August 2011, following extensive consumption of oxygen. The benthic flux of dissolved Mn was estimated based on Mn concentrations in the overlying waters and the near‐bottom waters. A preliminary box model was established to develop a dissolved Mn budget for the ECS. Based on the dissolved Mn content in the ECS and the total input flux, a residence time of 76–350 days for dissolved Mn in the ECS was inferred.

Dissolved trace metal (Cu, Cd, Co, Ni, and Ag) distribution and Cu speciation in the southern Yellow Sea and Bohai Sea, China

“…The nitrate concentration and fluxes increased by about tenfold from 1968 to 1997 [ Yan et al ., ; Duan et al ., ]. This agrees with the high nutrient concentration found around the Yangtze River estuary, and this distribution pattern has been observed repeatedly [ Liu et al ., ; Wei et al ., ]. However, the low level of dissolved metals around the Yangtze River estuary indicates that, although highly polluted, the Yangtze River is not a significant source for dissolved trace metals.…”

“…With the building of trace metal clean laboratories, and use of Teflon and LDPE containers and labware, trace metal clean sampling and analytical protocols can be applied, and more credible data have been reported. Dissolved Al and Mn distribution in the Yellow Sea (YS) and East China Sea have been studied by Ren et al [2011] and Wang et al [2016]. Wang et al [2012] have examined the behavior of several dissolved metals (Cu, Cd, and Mn) in the Pearl River estuary.…”

Anthropogenic Asian aerosols provide Fe to the North Pacific Ocean

“…The vertical distribution of Mn also excludes a sedimentary source of Fe to the surface ocean at 35°N. Both Mn and Fe are released from reductive sediments (29,30), so the marked differences between the vertical (Fig. 4) and surface (Fig.…”

“…4) and surface (Fig. 1) distributions of Fe and Mn indicate independent sources, even accounting for their different redox behavior, biological removal, and cycling (29)(30)(31). Thus, based on these multiple lines of evidence we attribute the elevated Fe concentrations observed between 35°N and 40°N to recent aerosol deposition.…”

Dissolved Lead in the East China Sea With Implications for Impacts of Marginal Seas on the Open Ocean Through Cross‐Shelf Exchange

“…The Fe‐Mn fraction is the most Pb‐reactive particulate phase, and the decrease in the oxidation‐reduction potential of sediment leads to a solubilization of Pb associated with Fe‐Mn oxides; part of it precipitates immediately, while the other part diffuses to the overlying water (Elbaz‐Poulichet et al, ). Studies of dissolved Mn in this area revealed an increased factor of 2–11 during the low‐oxygen cruise in 2011 (Wang et al, ), while the release of DPb was not as significant. Moreover, the bottom of Station A3 suffers high salinity intrusion, and there was no significant increase in DPb compared with same water masses.…”