R6 PM Bioavailability
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in 324-326

(HIL-1117-579256) Seasonal and source influences on labile metal distribution within the lower Willamette River, Oregon.

Hillwalker, W¹, Grove, R², Anderson, K¹, ¹ Oregon State University, Corvallis, OR, USA² USGS, Corvallis, OR, USA

ABSTRACT- The Willamette is a major river in Oregon utilized for transportation, recreation, subsistence fishing and aquatic organism habitat. The lower Willamette River is a typical urban and industrial lotic system with historical and current input of persistent organic pollutants and heavy metals. Though discrete sampling methods (e.g. grab water) are customarily required for assessment of pollutant risk to the principle users of an impacted site, this sampling methodology lacks the ability to capture time-integrated profiles and/or pulses of bioavailable contaminant fluxes in lotic systems. Diffusive gradients in thin film (DGT) is an in situ, time-integrated sampling device for the measurement of labile, cationic metal species in solutions at environmentally relevant concentration levels. DGT samplers were used to evaluate seasonal and spatial influences on the distribution of labile metals in the lower Willamette River, OR, during 2003 and 2004. The areas assessed include the Portland Harbor (RM 3.5 to 9.5) and the McCormick and Baxter (RM 7 east) Superfund sites. DGT were deployed for up to 21 days within the river near urban, industrial and undeveloped land use areas during a range of seasonal river conditions. Site-specific factors and metal-specific chemistry influenced the variability and distribution of labile metal concentrations seasonally and spatially within the lower Willamette River. The outcome of this study introduces uncertainty of interpreting grab water data and reevaluating the selection of sampling protocols when assessing contaminant risk within lotic systems.

Key words: metals, site variability, bioavailability, DGT