EVALUATING TEMPORAL PB ISOTOPE RECORD OF METAL DEPOSITION DOWNWIND OF A ZN AND PB SMELTER

Elevated lead (Pb) and other heavy metal concentrations have been detected in the Upper Columbia River Basin (UCRB) and are hypothesized to have originated from regional anthropogenic activity, including from Teck’s integrated zinc (Zn) and Pb smelting and refining complex in Trail, BC. Metal concentrations in epiphytic lichens provide evidence of the spatial extent of modern smelter emissions. However, temporal trends of atmospheric metal deposition in the UCRB are not well characterized. Sediment cores were collected from five lakes in the UCRB in both Washington and British Columbia to reconstruct the regional temporal trends of metal deposition. Pb isotopes can be measured within the cores in order to fingerprint the relative contribution of multiple emission sources over time.

Here we will present the first temporal reconstruction of Pb isotope ratios and metal concentrations from Middle Champion Lake, located 11.6 km NE of the Teck Trail facility. Age control for the sediment core is provided by ²¹⁰Pb dating and ¹³⁷Cs measurements. Lichens collected at each of the sampled lakes display metal concentrations above background with ranges of Pb (7.47 to 42.64 ppm), Cd (0.46 to 1.48 ppm), Zn (58.2 to 163.39 ppm), In (0.01 to 0.13 ppm), and Bi (0.03 to 0.38 ppm). Pb isotope results from lichens collected 13km south of Champions Lake (²⁰⁸Pb/²⁰⁴Pb=37.5304 ± 0.0028 and ²⁰⁶Pb/²⁰⁴Pb=17.7410 ± 0.0012) suggest that modern Pb deposition primarily originates from the Red Dog (²⁰⁸Pb/²⁰⁴Pb =36.174 ± 0.031 and ²⁰⁶Pb/²⁰⁴Pb =16.526 ± 0.045) and Sullivan (²⁰⁸Pb/²⁰⁴Pb =38.262 ±0.0007 and ²⁰⁶Pb/²⁰⁴Pb =18.4161±0.0008) ores that are processed at the Teck Smelter. These results are consistent with Pb isotopes measured at other sites in the region. Pb isotopic composition in the top section of the Champion Lakes core is expected to exhibit an isotopic signature similar to the lichens, while isotope ratios in lower sections of the core are expected to reflect the history of the ores processed, production changes, and controls on emission technologies at the Teck facility. Pb isotopic signatures will also identify other important sources of Pb into the region, such as the historic use of leaded gasoline.