Contrasting distributions of dissolved gaseous mercury concentration and evasion in the North Pacific Subarctic Gyre and the Subarctic Front

2022-03-24T07:11:22Z

Title: Contrasting distributions of dissolved gaseous mercury concentration and evasion in the North Pacific Subarctic Gyre and the Subarctic Front Authors: Kim, Hyunji; Han, Seunghee; Yang, Jisook; Hwang, Chung Yeon; Hahm, Doshick; Rhee, Tae Siek Abstract: Dissolved gaseous mercury (DGM) and methylmercury (MeHg) produced in the oceanic water column is an important inorganic Hg(II) transformation process involving atmosphere-water interactions and food web bioaccumulations, respectively. Although oxygen utilization has been reported to contribute significantly to MeHg variation, its contribution to the DGM variation is largely unknown. Here, we investigated DGM and MeHg distributions in relation to oxygen utilization in the Western Subarctic Gyre (WSG). We observed subsurface peaks of DGM (203？878 fM) and MeHg (274？750 fM) at a water depth of 200 or 300 m with a minimum oxygen concentration of 60？86 μmol kg？1. The apparent oxygen utilization of WSG water was positively and linearly associated with DGM (r2=0.83) and MeHg (r2=0.93), which might be a consequence of particulate organic carbon remineralization over a period of years (< 25 yrs). The DGM concentration was typically lower in the Subarctic Front than the other sites in relation to the dissolved oxygen and nutrient concentrations, while MeHg concentration was not. It might be attributable to increases in kox/kred, associated with isopycnal mixing between Kuroshio and Oyashio waters. The DGM and MeHg input from suboxic water should be placed in context with in situ production at the surface to better understand the biogeochemical cycles of Hg in ocean water.

Oceanic source strength of carbon monoxide on the basis of basin-wide observations in the Atlantic

2022-03-24T07:11:20Z

Title: Oceanic source strength of carbon monoxide on the basis of basin-wide observations in the Atlantic Authors: Park, Kihong; Rhee, Tae Siek Abstract: We measured the carbon monoxide (CO) concentrations in the marine boundary layer and the surface waters of the Atlantic Ocean from 50°N to 50°S during the UK Atlantic Meridional Transect expedition (AMT-7) in October 1998, covering the open ocean and coastal regions. Throughout the cruise track, atmospheric CO concentrations continually decreased southwards in the northern hemisphere with sporadic low and high concentrations encountered. South to the intertropical convergence zone (ITCZ) atmospheric CO was enhanced by ~10 ppb compared to north to ITCZ due likely to biomass burning emissions prevailed in the tropical continents. The remainder of the southern hemisphere reveals nearly invariable except for the vicinity of Rio de la Plata. The surface seawater was supersaturated everywhere along the track. The saturation anomaly of dissolved CO rose up to 90 with exhibiting a strong diurnal cycle. Maximal dissolved CO concentration in the diurnal cycle appeared 2 ？ 5 hours behind local maximum of solar insolation in the open ocean and the time lag further increased in the coastal region. The global ocean flux of CO to the atmosphere was estimated as 14 Tg(CO) a-1 with ranges of 4 ？ 24 Tg(CO) a-1. This is within uncertainty almost identical to what was estimated on the basis of the basin-wide observations in the Pacific and the Atlantic, but more than ~4 times lower than the values appeared in the Intergovernmental Panel on Climate Change (IPCC) reports.

DSpace Collection:

Contrasting distributions of dissolved gaseous mercury concentration and evasion in the North Pacific Subarctic Gyre and the Subarctic Front

Oceanic source strength of carbon monoxide on the basis of basin-wide observations in the Atlantic