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required that the sample be filtered and acidified to pH <_1.5 with Ultrex II ultrapure HNO,. Maximum hold <br />time for the sample was 180 days. <br />NAP Analyses <br />NAP (net-acid production), sometimes referred to as "net-acidity," was determined for all 13 <br />mine-waste composites using a modification of the technique described by Lapakko and Lawrence (1993). <br />This procedure is carried out on 1.00-g split of finely ground (-200 mesh) material taken from each <2-mm <br />mine-waste composite sample. Results are given in kg CaCO, per metric ton (parts per thousand). <br />Sulfate Analyses <br />Sulfate was determined by ICP-MS (Lamothe and others, 1999). This method required that the <br />sample be filtered and acidified with HNO, as described above. Maximum hold time was 180 days. <br />Mercury Analyses <br />Leachate mercury concentrations were determined by cold vapor-atomic fluorescence <br />spectrometry (CV-AFS) (Hageman, 2002). For this method, the filtrate was acidified/preserved with a 1- <br />percent sodium dichromate/concentrated HNO3 solution in a ratio of 1:19 (one part sodium <br />dichromate/HNO3 solution to 19 parts leachate sample). Leachate samples were collected in nitric-acid- <br />washed flint-glass bottles with Teflon-lined lids. <br />Results and Discussion <br />In this report, leachate geochemical comparisons are made (5-minute USGS field leach test vs. 18- <br />hour leach test) for all 13 mine-waste composite samples. Complete leachate geochemical data for all sites <br />are given in tabular form in Appendix 1. NAP results for solid mine-waste samples are given in Appendix <br />2. Data plots comparing leachate pH, specific conductance, and sulfate for all 13 mine-wastes are presented <br />(figs. 2 and 3) and discussed. In addition to comparing relative trends for all sites, plots detailing leachate <br />geochemical data and trends for individual mine-wastes are presented in figures 4-16. Leachate <br />geochemical summaries for individual mine-wastes are presented in Appendix 3. Data in the summaries <br />include: site location, host rock, leachate pH, specific-conductance trends, , sulfate, selected major-element <br />trends, selected trace-element trends, and NAP on the solids. Finally, this paper presents, describes, and <br />discusses three mine-waste-ranking schemes. <br />Data <br />Important note.-Concentrations presented in this paper are leachate concentrations. All samples <br />were leached at 20:1 ratio (20 parts deionized water to I part solid), except for NAP, which was measured <br />from a split of the mine-waste composite <2-mm solid material. <br />Hageman_SIR_2508.doc 6 7/21/2004 2:50 PM