Zinc and copper isotopes as tracers of anthropogenic contamination in a sediment core from an urban lake

Anita Thapalia, University of Texas at El Paso

Abstract

Concentration data alone are often insufficient to resolve metal sources. This study applies stable Zn and Cu isotopes to fingerprint and track the sources of these metals in a sediment core from Lake Ballinger near Seattle, Washington, USA. The base of the Lake Ballinger core pre-dates settlement in the region, while the upper sections record the impact of atmospheric emissions from the nearby Tacoma smelter, as well as Cu and Zn inputs from urban sources. δ66 Zn and δ65 Cu varied by 0.42[per thousand] and 0.29[per thousand], respectively, over the >300 year core record. Isotopic changes were correlated with the pre-smelter period (δ 66 Zn = +0.30[per thousand]; δ65 Cu = +0.77[per thousand]), a period of smelter operation (δ66 Zn = +0.14 ± 0.06[per thousand]; δ65 Cu = +0.94 ± 0.1[per thousand]), and a post-smelting/stable urban land use period (δ66 Zn = 0.00 ± 0.1[per thousand]; δ65 Cu = +0.82[per thousand]). Rapid urbanization in the mid 1900's did not significantly impact the δ 66 Zn and δ65 Cu smelter signatures, suggesting that increased metal loads during this time were derived mainly from mobilization of historically contaminated soils. Urban sources of Cu and Zn were dominant over the last 2 decades, and the δ66 Zn measured for tire samples suggests tire wear is a likely source of Zinc.

Recommended Citation

Anita Thapalia, "Zinc and copper isotopes as tracers of anthropogenic contamination in a sediment core from an urban lake" (January 1, 2009). ETD Collection for University of Texas, El Paso. Paper AAI1465276.
http://digitalcommons.utep.edu/dissertations/AAI1465276