Sediment Profile and Fluxes of Mercury and Methyl Mercury in Weihe Watershed in Henan, China.

Sediment core samples were collected from the Weihe River in February and August 2013. Cores were sectioned and analyzed for total Hg (THg) and methyl mercury (MeHg). THg in sediment cores ranged from 156 to 282 ng g(-1) in February, and from 172 to 300 ng g(-1) in August. MeHg concentrations ranged from 0.80 to 3.11 ng g(-1) in both seasons. Results showed that the diffusive fluxes were up to two orders of magnitude lower than the in situ benthic fluxes. Fluxes of MeHg measured in in situ experiments in August were positively correlated with [Formula: see text] (r = 0.930). THg and MeHg release were not strongly correlated with TOC in February. Patterns of MeHg flux differed greatly depending on oxidation-reduction potential (Eh) (r > 0.70) conditions in the two seasons.