DETECTION OF METAL CONTAMINATION IN WILD ASPARAGUS NEAR A WASTE-DISPOSAL SITE

Estimating contaminant distributions in environmental media is necesar y to evaluate human and ecological hazards. Because of uncertainties i n release histories and transport, traditional sampling and statistica l techniques applicable to the experimental sciences may not be suitab le for exploratory studies at hazardous waste sites. An approach that relies on cluster analysis of principal components (PCA) was used to i dentify contaminated wild asparagus (Asparagus officinalis) growing in the vicinity of waste disposal sites along the Columbia River at the U.S. Department of Energy's Hanford Site in southeast Washington state . Metals in soil samples taken from the sites contained elevated level s of Ag, Al, Ba, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn, and V. Samples of asp aragus tissue were collected from the river near the waste site, from Hanford old fields abandoned 52 years ago, and from commercial fields in the neighboring communities. Dried tissues were analyzed for metals content by ICP-mass spectrometry, furnace AA, and cold vapor Ak Tissu e concentrations of elements varied over 5 orders of magnitude, from K at 46 900 ppm to As and Ag at maximum concentrations below 1 ppm. PCA produced four components that accounted for 66.2% of the metals varia nce. Subsequent cluster analysis using Ward's minimum variance separat ed the data into Columbia River and old-field groups, with the River g roup further divided into three clusters: plants primarily upriver fro m the waste sites, plants primarily downriver, and plants growing in o r near the waste sites. The clustering showed that the more soluble co mponents of the discharges (Ba and Ca) showed a pattern of distributio n in the asparagus plants consistent with the ground water flow patter n, in that these elements were found far downriver of the disposal sit es themselves. In contrast, the less mobile elements Al, Cd, Cr, Fe, M n, Tl, and Zn were elevated only near the most-recently used waste dis posal area. Asparagus from agricultural fields, including fields aband oned 50 years ago, contained higher concentrations of Fe, Cu, Pb, K, a nd Ni than did the wild riverine plants.