This report integrates and summarizes research on the fateand-transport properties of munition energetic compounds potentially migrating to groundwater. The goals of the report are to 1) review and summarize previous work; 2) identify data gaps; 3) provide research recommendations; and integrate conclusions from peer-reviewed research, results from investigations at military ranges, and consultations with explosives experts in the United States and Canada (Waterways Experiment Station, Army Environmental Center, Defence Research EstablishmentValcartier, and various universities) into a conceptual model for the transport of energetic compounds from the land surface to groundwater.

A routine procedure was established for determining soil water content by microwave drying. The procedure requires small, 20‐gram soil samples heated for a 20‐min period at full power (600 to 650 W) in a household‐type microwave oven. Using this procedure, consistent agreement (within 0.5 wt%) was obtained between microwave and electric oven drying for soil materials ranging from quartz sands to fine silts and clays, with water contents ranging from air‐dry to saturation and with organic matter ranging from 0 to > 20 wt%.

Irrigation is likely to increase water losses from hillslopes, particularly on loess-derived soils with impeded drainage. This is important as irrigation of these soils in New Zealand is increasing. A field site was established to measure runoff from a pasture hillslope irrigated by a centre-pivot in South Canterbury. Between November and March, 161 and 199 mm of irrigation was applied, with 23% more at the bottom of the slope. Runoff varied with position in the hillslope, with 3.5 times from the bottom plot (52 mm) compared to the top. Over the length of the slope (40 m) this represents a potential loss of 9% of precipitation, or 21% of the irrigation. Evidence for saturation excess and infiltration excess runoff was observed, with antecedent soil moisture conditions being a key factor. Pasture production and water use efficiency (WUE) also varied with slope, the least (4.6 t DM/ha or 12 kg DM/ha/mm) observed at middle and most at the top of the slope (10.1 t DM/ha or 23 kg DM/ha/mm). This was likely due to a combination of differences in radiation and soil conditions. There was indication that pasture growth was limited by water availability at the top and potentially excess at the bottom of the slope. Our results indicate potential for improving irrigation practices.

Laboratory experiments were performed to compare the effectiveness of limestone (CaC0 3) and hydrated lime [Ca(OH)2] for improving waste water quality through the neutralization of acidic uranium mill tailings liquor. The experiments were designed to also assess the effects of three proposed mechanisms-carbonate complexation, elevated pH, and colloidal particle adsorption-on the solubility of toxic contaminants found in a typical uranium mill waste solution. Of special interest were the effects each of these possible mechanisms had on the solution concentrations of trace metals such as Cd, Co, Mo, Zn, and U after neutralization. Results indicated that the neutralization of acidic tailings to a pH of 7.3 using hydrated lime provided the highest overall waste water quality. Both the presence of a carbonate source or elevating solution pH beyond pH= 7.3 resulted in a lowering of previously achieved water quality, while adsorption of contaminants onto colloidal particles was not found to affect the solution concentration of any constituent investigated. At solution pHs greater than pH = 6.3, carbonate complexation affects the solid phase control for uranium and perhaps zinc concentrations, while molybdenum concentrations were found to be a function of elevated solution pH. Arsenic, Cd, Cr, Pb, and V were effectively removed from solution at all solution pHs exceeding pH = 6.5, regardless of solution carbonate content. Cobalt removal is best at pH values above 7 .3, and copper removal may be enhanced in carbonate-bearing solutions. Selenium removal is only 50% for either reagent at all pH values studied. Uranium solution concentrations in the presence of excess carbonate reagents were significantly higher than in solutions created by hydrated lime-only neutralization, but all solutions were below U.S. Nuclear Regulatory Commission radiation protection limits. Molybdenum was effectively removed from solution at pH = 6.3 but was present at pH = 9.0 in concentrations corresponding to those found in the unneutralized tailings liquor. Aqueous speciation calculations with the computer code MINTEQ were used to clarify these observed results. Acidic untreated solid tailings from two mill sites and tailings neutralized with lime were leached with a simulated ground water for several pore displacement volumes. Analyses performed on the column effluents indicate that prior neutralization results in a significant reduction in the concentration of all pH-dependent constituents. In comparing the effluent data from the neutralized and untreated tailings, ions such as Al, As, Cd, Co, Cr, Cu, Fe, Si, Sr, V, and Zn displayed reduction of several orders of magnitude and, in most cases, were below detectable limits in the effluents generated from the neutralized tailings. It appears that more molybdenum leaches from the neutralized tailings column for the Lucky Me sample than for the untreated tailings column. Ions such as Ca, Mg, Na, Cl, and so 4 comprised the majority of the total dissolved solids content in the lime-treated tailings e...

Laboratory experiments were conducted to evaluate the performance of a two step neutralization scheme for treatment of acidic uranium mill tailings solutions. Tailings solutions from the Lucky Me Mill and Exxon Highland Mill, both in Wyoming, were initially neutralized with limestone, CaC03, to an intermediate pH of either 4.0 or 5.0, followed by lime, Ca(OH)2, neutralization to pH 7.3. On the basis of these combination limestone/lime treatment methods, CaC03 neutralization to pH 4 followed by further neutralization with Ca(OH)2 to pH 7.3 resulted in the highest quality effluent solution with respect to EPA 1 S water quality guidelines. Furthermore, this combination method is the most cost-effective treatment procedure tested in our studies over the last 2 yr. Neutralization experiments to evaluate the optimum solution pH for contaminant removal were performed on the same two tailings solutions utilizing only lime Ca(OH)2 as the neutralizing agent. The pH optimization data indicates solution neutralization above pH 7.3 does not significantly increase removal of pH dependent contaminants from solution. Column leaching experiments were performed on the neutralized sludge material (the precipitated solid material which forms as the acidic tailings solutions are neutralized to pH 4 or above). The sludges from Lucky Me and Exxon neutralized tailings solutions were packed into columns and then contacted with laboratory prepared synthetic ground water until several effluent pore volumes were collected. Effluent solutions were analyzed for macro ions, trace metals and radionuclides in an effort to evaluate the long term effectiveness of attenuating contaminants in sludges formed during solution neutralization. Neutralized sludge leaching experiments indicate that Ca, Na, Mg, Se, Cl, and S04 are the only constituents which show solution concentrations significantly higher than the synthetic ground water in the early pore volumes of long term leaching studies. Longer-term leaching studies are continuing.

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