Kagoshima Bay is located on the south coast of the island of Kyushu,Japan.Shallow hydrothermal vents present in the northern portion of the Bay have been identified as a natural source of mercury(Hg)adjacent to a densely populated area.The aim of the present work is to study the spatial distribution of Hg in bottom sediments of the Bay and its relationship with some major physicochemical properties that might affect its transport and distribution.For this reason,sediment core samples were collected in the north and central areas of the Bay at 14 locations,in surveys carried out during 2011 and 2013.The individual core samples were sliced and processed for the analysis of total mercury(T-Hg),elemental composition,total organic carbon(TOC),particle size and magnetic susceptibility(MS).Horizontal distribution of Hg shows that submarine hydrothermal vents are the main source of Hg in the area since average concentration of T-Hg is high near the fumaroles(1.2 ± 0.6 mg/Kg)and decreases sharply with the distance(0.09 ± 0.01 mg/Kg at the central area).It was also found that bottom features might influence the way Hg emitted from the vents distributes along the Bay.Results suggest that Hg is associated predominantly to TOC in the northern part of the bay,indicating a key role of organic matter binding emitted Hg.In the area at the east of the fumaroles,the relationship between Hg and TOC is characterized by presenting two different linear trends matching the upper and lower sections of the cores; possibly reflecting a change in the depositional conditions that occurred in the past.In the central portion of the Bay,which is at a considerable distance from the fumaroles,low levels of mercury and no significant correlation with TOC was found,evidencing background levels.Magnetic susceptibility profiles reveal similar depositional environments in areas with analogous T-Hg and TOC relationships,indicating a change in the sediment composition and probably the sedimentation regime.Vertical distribution of particle size and elemental composition could not be linked directly to T-Hg profiles.However,distribution of these parameters shows that diverse mechanisms,both physical and chemical,control the composition of the sediments and therefore its ability to influence the distribution of Hg in this aquatic environment.