Mercury distribution and speciation in two lagoons with different pollution and eutrophication conditions in Taiwan

This study explored biogeochemical processes controlling the distribution of mercury (Hg) species in two lagoons with different pollution and eutrophication conditions in southwestern Taiwan. The eutrophication and pollution levels were higher in the Dapeng Bay than in the Chiku Lagoon, engendering a higher particulate Hg concentration and enrichment factor in the Dapeng Bay. The concentration range of total dissolved Hg (Hg_TD) and reactive Hg (Hg_R) was comparable between the lagoons, but the concentration of particulate Hg (Hg_P) was higher in the Dapeng Bay. Hg_R and Hg_TD abundance was primarily controlled by the availability of dissolved oxygen (DO) and biological absorption. In addition to pollution (which elevated Hg_P concentration), biological absorption and/or adsorption rather than lithogenic processes more likely regulated the Hg_P concentration. The effect of Hg pollution may superimpose on that of DO on the distributions of Hg_R and Hg_TD and may enhance Hg_P formation in the Dapeng Bay.