CHEMICAL AND LEAD ISOTOPE CONSTRAINTS ON SOURCES OF POLLUTION IN TREE BARK IN SOUTHWEST OHIO

Atmospheric particulates containing heavy metals are hazardous to human health and the environment, and can originate from a wide variety of anthropogenic sources. Within the Ross-Hamilton townships (OH) there are several potential sources of such contaminants, including the Hamilton Municipal Electric Plant (HMEP), which combusts coal to produce electricity; former and current steel manufacturing plants including the Armco Hamilton superfund site; and the former Fernald Feed Materials Production Center (FFMPC) in Ross, which was established to process high purity uranium (U) products from U ore. We performed trace element and Pb isotopic analysis of tree bark in a transect from Hamilton (industrial) to Ross (rural) in order to investigate the relative contributions of atmospheric pollutants from Hamilton-based industries and the FFMPC site. With the exception of U, most heavy metals are found in concentrations significantly above background levels in Hamilton area tree bark. Tungsten (W) concentrations increase progressively towards Hamilton, reaching concentrations of 8x times background levels, with elevated concentrations persisting up to 17 km from Hamilton. Elevated W may be attributed to abrasion of W-carbide in the coal plant stacks, consistent with W-rich particulates in street sediment that lack other heavy metals characteristic of steel [1]. U concentrations in tree bark are highest near the FFMPC site, reaching concentrations 30x background levels within 1 km of the FFMPC, and >4x background levels up to 8 km away. These data demonstrate widespread environmental U contamination from the FFMPC, consistent with non-natural U isotopic signatures in pond sediment and tree bark near the FFMPC [2,3]. In contrast, lead (Pb) concentrations in the tree bark vary 30-fold, but do not show any clear geographic pattern. Lead isotopes suggest >50% contaminant Pb in some samples, consistent with combustion of fossil fuels, e.g. coal and leaded gasoline. However, there is no indication of any contribution of uranogenic Pb from U ore processing at the FFMPC.

[1] LeGalley, E. and Krekeler, M.P.S., 2013. Environmental Pollution 176, 26-35.

[2] Tortorello et al., 2013. J. Environmental Radioactivity 124, 287-300.

[3] Widom, E. and Kuentz, D.C., 2010. GSA abstract, Denver.