Abstract
We assessed the impacts of an innovative Hg water treatment system on a small,
industrially-contaminated stream in the southeastern United States. The treatment system, installed in
2007, removes Hg from wastewater using tin (Sn) (II) chloride followed by air stripping. Mercury concentrations
in the receiving stream, Tims Branch, decreased from >100 to 10 ng/L in the four years following
treatment, and Hg body burdens in redfin pickerel (Esox americanus) decreased by 70% at the most
contaminated site. Tin concentrations in water and fish increased significantly in the tributary leading
to Tims Branch, but concentrations remain below levels of concern for human health or ecological risks.
While other studies have shown that Sn may be environmentally methylated and methyltin can transfer
its methyl group to Hg, results from our field studies and sediment incubation experiments suggest that
the added Sn to the Tims Branch watershed is not contributing to methylmercury (MeHg) production or
bioaccumulation in this system. The stannous chloride treatment system installed at Tims Branch was
effective at removing Hg inputs and reducing Hg bioaccumulation in the stream, but future studies are
needed to assess longer term impacts of Sn on the environment.
