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Leaching Parameters <br />The <2-mm mine-waste composite samples were leached using the simplified USGS field leach <br />test described in Hageman and Briggs (2000), followed by an 18-hour end-over-end leaching test. In the <br />USGS field leach test, 100.0 g of the <2-mm fraction of the composite sample was put in a plastic bottle <br />and 2.0 L of deionized water was slowly added. The container was capped and shaken vigorously for 5 <br />minutes. After shaking, the mixture was allowed to settle for -10 minutes. Leachates produced from these <br />tests were measured for pH and specific conductance and then syringe-filtered (0.45-µm pore-size <br />nitrocellulose capsule filters). Portions of the filtrate were taken and preserved for analysis by inductively <br />coupled plasma-atomic emission spectroscopy, inductively coupled plasma-mass spectroscopy, ion <br />chromatography, and for mercury analysis. The containers were then recapped and placed on an end-over- <br />end rotator for 18 hours. After rotation for 18 hours, the leachates were allowed to settle. The leachate was <br />then sampled, measured, and preserved in the manner described above. <br />Analytical Methods and Procedures <br />Similar analytical methods and procedures were used for all samples. Following is a brief <br />explanation of analytical techniques and equipment used in this study. <br />pH <br />Laboratory pH measurements for unfiltered leachates were obtained using an Orion Model 230-A <br />pH meter and an Orion combination pH electrode. The meter was calibrated prior to each set of <br />measurements, and calibration checks were obtained on mid-range buffers between readings. For <br />calibration to be successful, buffers must not exceed known concentration by ±0.02 pH units. The analysis <br />of pH required no sample treatment, and the sample was analyzed immediately. <br />Specific Conductance <br />Laboratory measurements were made on unfiltered leachate using a Myron L portable <br />conductivity meter (Model DC4). Prior to initial use, the meter was calibrated with'commercially obtained <br />conductivity standards. Prior to each set of observations, aliquots of commercially obtained 100-gS/cm and <br />1,000-µS/cm standards were checked and their values recorded. Conductivity analysis required no sample <br />treatment, and samples were analyzed immediately. <br />Metals Analyses <br />Concentrations of metals were determined by the following methods: inductively coupled plasma- <br />atomic emission spectroscopy (ICP-AES) (Meier and others, 1994), and inductively coupled plasma-mass <br />spectroscopy (ICP-MS) (Lamothe and others, 1999). Preservation of the samples for metals analysis <br />Hageman_SIR_2508.doc 5 7/21/2004 2:50 PM