Heavy Metal Transport and Behavior in the Lower Columbia river, USA |
| |
Authors: | Vernon G Johnson Robert E Peterson Khris B Olsen |
| |
Institution: | (1) Fluor Hanford Company, MSIN: E6-35, Richland, Washington, U.S.A.;(2) Pacific Northwest National Laboratory, MSIN: K6-96, Richland, Washington, U.S.A. |
| |
Abstract: | The primary objective of this study was to evaluate temporal changes in heavy metal content of lower Columbia River sediment
following terminated or reduced soluble heavy metal loading from the world's largest lead-zinc refinery and mining districts
in the USA and Canada. Sediment cores were collected from two fine sediment depositional sites (∼600 km downstream) in August
1999 and were analyzed for total metal content, texture, and age/dating parameters. Zinc, cadmium and lead contents in 1999
declined by only a factor of two over their depth profile maxima (dated as between 1970 and 1980). In sharp contrast, more
than a 10-fold decrease in dissolved metal loading occurred during this same period. Zinc in filtered Columbia River water
at downstream locations also declined by > 10-fold, consistent with the reduced upper river solute-metal loading. Once soluble
metal releases are reduced or terminated, the solute half-time in Columbia River water is months versus ∼20 yr for adsorbed
metals on surficial (or resuspended) bed sediments. The much slower rate of decline for sediment, as compared to the solute
phase, is attributed to resuspension, transport and redeposition of irreversibly bound metals from upstream sedimentary deposits.
This implies downstream exposure of benthic or particle-ingesting biota can continue for years following source remediation
and/or termination of soluble metal releases. Accordingly, contaminant contents of both particulate and solute phases of river
water, as well as sediment core sections, are suggested for assessing long-term biotic exposure/response to mitigation activities
in the Columbia River and similar fluvial ecosystems. |
| |
Keywords: | sediments Columbia River heavy metal transport and behavior |
本文献已被 PubMed SpringerLink 等数据库收录! |
|