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<br />2016 <br /> <br />. <br /> <br />Figure 7 near here. <br /> <br />Over 90 percent of the dissolved Pb was complexed as the PbC03 species at all locations and during all <br /> <br />flow regimes (Figure 8). The highest median activity of PbC03 was predicted for samples collected below Empire <br /> <br />Gulch. The maximwn predicted Pb+2 activity represented 19 percent of the dissolved Pb for a sample collected at <br /> <br />Buena Vista during snowmelt runoff, although the average Pb+2 activity at Buena Vista represented only 5 percent <br /> <br />of the dissolved Pb. The maximum Pb+2 and Pbe03 activities were predicted for samples collected during <br /> <br />snowmelt runoff. During snowmelt runoff, Pb+2 accounted for about 4 percent of the dissolved Pb species at most <br /> <br />sites. <br /> <br />Figure 8 near here. <br /> <br />The highest median activities of 20+2, 2nC03, and 2o(OH}z were predicted for samples collected from the <br /> <br /> <br />. Arkansas River below Empire Gulch (Figure 9). Although the median activities of Zn+2, 2oc03, and Zn(OH}z <br /> <br /> <br />tend to decrease downstream from Empire Gulch, the percentage of dissolved 20 represented by 20+2 tended to <br /> <br />increase at several downstream sites. At Buena Vista, the free cation 20+2 represented on average about 67 percent <br /> <br />of the dissolved Zn species. Over 90 percent of the dissolved zinc was predicted as 20+2 for one sample collected <br /> <br />at Buena Vista. Low complexing capabilities of water input from Lake Creek, in addition to a lower median pH <br /> <br />than for the other mainstem sites, contributed to the dominance of the Zn+2 species at Buena Vista. Downstream <br /> <br />from Nathrop, Zn complexes were predominate over the free cation. On average, about 80 percent of the dissolved <br /> <br />zinc was predicted to occur as complexed species at Portland. <br /> <br />The highest median activities for 20+2, 2oC03' and 2o(OH}z were predicted for samples collected during <br /> <br />pre-snowmelt runoff, although the snowmelt-runoff samples had on average the highest percentage (64%) of the <br /> <br />free cation, 20+2 (Figure 9). Low-complexing capabilities of water input during snowmelt, in addition to a lower <br /> <br />.median pH than for the other flow regimes contributes to the dominance of Zn +2 during snowmelt runoff. During <br /> <br />15 <br />