Gaseous elemental mercury (GEM) and reactive gaseous mercury (RGM) were measured over two-week seasonal field campaigns near Salmon Falls Creek Reservoir in south-central Idaho from the summer of 2005 through the fall of 2006 and over the entire summer of 2006 using automated Tekran mercury analyzers. GEM, RGM, and particulate mercury (HgP) were also measured at a secondary site 90 km to the west in southwestern Idaho during the summer of 2006. The study was performed to characterize mercury air concentrations in the southern Idaho area for the first time, estimate mercury dry deposition rates, and investigate the source of observed elevated concentrations. High seasonal variability was observed with the highest GEM (1.91 ± 0.9 ng m -3 ) and RGM (8.1 ± 5.6 pg m -3 ) concentrations occurring in the summer and lower values in the winter (1.32 ± 0.3 ng m -3 , 3.2 ± 2.9 pg m -3 for GEM, RGM respectively). The summer-average HgP concentrations were generally below detection limit (0.6 ± 1 pg m -3 ). Seasonally-averaged deposition velocities calculated using a resistance model were 0.034 ± 0.032, 0.043 ± 0.040, 0.00084 ± 0.0017 and 0.00036 ± 0.0011 cm s -1 for GEM (spring, summer, fall, and winter, respectively) and 0.50 ± 0.39, 0.40 ± 0.31, 0.51 ± 0.43 and 0.76 ± 0.57 cm s -1 for RGM. The total annual RGM + GEM dry deposition estimate was calculated to be 11.9 ± 3.3 μg m -2 , or about 2/3 of the total (wet + dry) deposition estimate for the area. Periodic elevated short-term GEM (2.2 -12 ng m -3 ) and RGM (50 -150 pg m -3 ) events were observed primarily during the warm seasons. Back-trajectory modeling and PSCF analysis indicated predominant source directions from the southeast (western Utah, northeastern Nevada) through the southwest (north-central Nevada) with fewer inputs from the northwest (southeastern Oregon and southwestern Idaho). v vi ACKNOWLEDGMENTSWe are indebted to Sage Aslet for allowing us to do our air sampling on his ranch at House

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This document presents methods and results of benchmark testing (i.e., code-to-code. comparisons) and partial validation testing (i.e., tests which compare field data to the computer generated solutions) of the FLASH computer code, Version 3.0, which were conducted to determine if the code is ready for performance assessment studies of the Radioactive Waste Management Complex. Three test problems are presented that were designed to check computational efficiency, accuracy of the numerical algorithms, and the capability of the code to simulate diverse hydrological conditions. These test problems were designed to specifically test the code's ability to simulate, (a) seasonal infiltration in response to meteorological conditions, C o) changing watertable elevations due to a transient areal source of water, (i.e. influx from " spreading basins), and (c) infiltration into fractured basalt as a result of seasonal water in drainage ditches. ",it The FLASH simulations generally compared well with the benchmark codes, indicating good stability and acceptable computational efficiency while simulating a wide range of conditions. The code appears operational for modeling both unsaturated and saturated flow in fractured, heterogeneous porous media. However, the code failed to converge when a unsaturated to saturated transition occurred. Consequently, the code should not be used when this condition occurs or is expected to occur, i.e. when perched water is present or when infiltration rates exceed the saturated conductivity of the soil.

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