Pilot-scale treatment of RDX-contaminated soil with zerovalent iron

Soils in Technical Area 16 at Los Alamos National Laboratory (LANL) are severely contaminated from past explosives testing and research. Our objective was to conduct laboratory and pilot-scale experiments to determine if zerovalent iron (Fe(0)) could effectively transform RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) in two LANL soils that differed in physicochemical properties (Soils A and B). Laboratory tests indicated that Soil A was highly alkaline and needed to be acidified [with H2SO4, Al2(SO4)3, or CH3COOH] before Fe(0) could transform RDX. Pilot-scale experiments were performed by mixing Fe(0) and contaminated soil (70 kg), and acidifying amendments with a high-speed mixer that was a one-sixth replica of a field-scale unit. Soils were kept unsaturated (soil water content = 0.30-0.34 kg kg(-1)) and sampled with time (0-120 d). While adding CH3COOH improved the effectiveness of Fe(0) to remove RDX in Soil A (98% destruction), CH3COOH had a negative effect in Soil B. We believe that this difference is a result of high concentrations of organic matter and Ba. Adding CH3COOH to Soil B lowered pH and facilitated Ba release from BaSO4 or BaCO3, which decreased Fe(0) performance by promoting flocculation of humic material on the iron. Despite problems encountered with CH3COOH, pilot-scale treatment of Soil B (12 100 mg RDX kg(-1)) with Fe(0) or Fe(0) + Al2(SO4)3 showed high RDX destruction (96-98%). This indicates that RDX-contaminated soil can be remediated at the field scale with Fe(0) and soil-specific problems (i.e., alkalinity, high organic matter or Ba) can be overcome by adjustments to the Fe(0) treatment.     

Biotic and abiotic degradation of CL-20 and RDX in soils

The caged cyclic nitramine 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is a new explosive that has the potential to replace existing military explosives, but little is known about its environmental toxicity, transport, and fate. We quantified and compared the aerobic environmental fate of CL-20 to the widely used cyclic nitramine explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in surface and subsurface soil microcosms. Soil-free controls and biologically attenuated soil controls were used to separate abiotic processes from biologically mediated processes. Both abiotic and biological processes significantly degraded CL-20 in all soils examined. Apparent abiotic, first-order degradation rates (k) for CL-20 were not significantly different between soil-free controls (0.018 < k < 0.030 d(-1)) and biologically attenuated soil controls (0.003 < k < 0.277 d(-1)). The addition of glucose to biologically active soil microcosms significantly increased CL-20 degradation rates (0.068 < k < 1.22 d(-1)). Extents of mineralization of (14)C-CL-20 to (14)CO(2) in biologically active soil microcosms were 41.1 to 55.7%, indicating that the CL-20 cage was broken, since all carbons are part of the heterocyclic cage. Under aerobic conditions, abiotic degradation rates of RDX were generally slower (0 < k < 0.032 d(-1)) than abiotic CL-20 degradation rates. In biologically active soil microcosms amended with glucose aerobic RDX degradation rates varied between 0.010 and 0.474 d(-1). Biodegradation was a key factor in determining the environmental fate of RDX, while a combination of biotic and abiotic processes was important with CL-20. Our data suggest that CL-20 should be less recalcitrant than RDX in aerobic soils.     

Dissolution and transport of TNT, RDX, and composition B in saturated soil columns

Low-order detonations and blow-in-place procedures on military training ranges can result in residual solid explosive formulations to serve as distributed point sources for ground water contamination. This study was conducted to determine if distribution coefficients from batch studies and transport parameters of pure compounds in solution adequately describe explosive transport where compounds are present as solid particles in formulations. Saturated column transport experiments were conducted with 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and the explosive formulation, Composition B (Comp B) (59.5 +/- 2.0% RDX, 39.5 +/- 2.3% TNT, and 1% wax) in solid and dissolved forms. The two soils used were Plymouth loamy sand (mesic, coated Typic Quartzipsamments) from Camp Edwards, MA and Adler silt loam (coarse-silty, mixed, superactive, thermic Fluvaquentic Eutrudepts) from Vicksburg, MS. Interrupted flow experiments were used to determine if explosives were at equilibrium distribution between soil and solution phases. The HYDRUS-1D code was used to determine fate and transport parameters. Results indicated that sorption of high explosives was rate limited. The behavior of dissolved Comp B was similar to the behavior of pure TNT and RDX. Behavior of solid Comp B was controlled by dissolution that depended on physical properties of the Comp B sample. Adsorption coefficients determined by HYDRUS-1D were different from those determined in batch tests for the same soils. Use of parameters specific to formulations will improve fate and transport predictions.     

Remediating munitions-contaminated soil with zerovalent iron and cationic surfactants

Soils contaminated from military operations often contain mixtures of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), and TNT (2,4,6-trinitrotoluene) rather than a single explosive. Differences among explosives in solubility and reactivity make developing a single remediation treatment difficult. When Fe(0) was used to treat a munitions-contaminated soil, we observed high rates of destruction for RDX and TNT (98%) but not HMX. Our objective was to determine if HMX destruction by Fe(0) could be enhanced by increasing HMX solubility by physical (temperature) or chemical (surfactants) means. To determine electron acceptor preference, we treated RDX and HMX with Fe(0) in homogeneous solutions and binary mixtures. Increasing aqueous temperature (20 to 55 degrees C) increased HMX solubility (2 to 22 mg L(-1)) but did not increase destruction by Fe(0) in a contaminated soil slurry that also contained RDX and TNT. Batch experiments using equal molar concentrations of RDX and HMX demonstrated that RDX was preferentially reduced over HMX by Fe(0). By testing various surfactants, we found that the cationic surfactants (HDTMA [hexadecyltrimethylammonium bromide], didecyl, and didodecyl) were most effective in increasing HMX concentration in solution. Didecyl and HDTMA were also found to be highly effective in facilitating the transformation of HMX by Fe(0). Using HDTMA or didecyl solutions (3%, w/v) containing solid-phase HMX, we observed that 100% of the added HMX was transformed by Fe(0) in the didecyl matrix and 60% in the HDTMA matrix. These results indicate that cationic surfactants can increase HMX solubility and facilitate Fe(0)-mediated transformation kinetics but HMX destruction rates will be slowed when RDX is present.     

Soil mixing to decrease surface stratification of phosphorus in manured soils

Continual applications of fertilizer and manure to permanent grassland or no-till soils can lead to an accumulation of P at the surface, which in turn increases the potential for P loss in overland flow. To investigate the feasibility of redistributing surface stratified P within the soil profile by plowing, Mehlich-3 P rich surface soils (128-961 mg kg(-) in 0-5 cm) were incubated with lower-P subsoil (16-119 mg kg(-1) in 5-20 cm) for 18 manured soils from Oklahoma and Pennsylvania that had received long-term manure applications (60-150 kg P ha(-1) yr(-1) as dairy, poultry, or swine manure for up to 20 yr). After incubating a mixture of 5 g surface soil (0- to 5-cm depth) and 15 g subsoil (5- to 20-cm depth) for 28 d, Mehlich-3 P decreased 66 to 90% as a function of the weighted mean Mehlich-3 P of surface and subsoil (i.e.. 1:3 ratio) (r2 = 0.87). At Klingerstown, Northumberland County, south central Pennsylvania, a P-stratified Berks soil (Typic Dystrochrept) (495 mg kg(-1) Mehlich-3 P in 0- to 5-cm depth) was chisel plowed to about 25 cm and orchardgrass (Dactylis glomerata L.) planted. Once grass was established and erosion minimized (about 20 wk after plowing and planting), total P concentration in overland flow during a 30-min rainfall (6.5 cm h(-1)) was 1.79 mg L(-1) compared with 3.4 mg L(-1) before plowing, with dissolved P reduced from 2.9 to 0.3 mg L(-1). Plowing P-stratified soils has the potential to decrease P loss in overland flow, as long as plowing-induced erosion is minimized.     

Remediating RDX-contaminated ground water with permanganate: laboratory investigations for the Pantex perched aquifer

Ground water beneath the U.S. Department of Energy Pantex Plant is contaminated with the high explosive RDX (hexahydro-1,3,5-trinitro-1,3,5 triazine). The USDOE Innovative Treatment and Remediation Demonstration (ITRD) program identified in situ oxidation by permanganate as a technology fit for further investigation. We evaluated the efficacy of KMnO(4) to transform and mineralize RDX by determining degradation kinetics and carbon mass balances using (14)C-RDX. Aqueous RDX solutions (2-5 mg L(-1)) and RDX-contaminated slurries (50% solids, w/v) were treated with KMnO(4) at 1000, 2000, 4000, and 20000 mg L(-1). Treating an aqueous RDX solution of 2.8 mg L(-1) with 20000 mg KMnO(4) L(-1) decreased RDX to 0.1 mg L(-1) within 11 d while cumulative mineralization proceeded for 14 d until 87% of the labeled carbon was trapped as (14)CO(2). Similar cumulative mineralization was obtained when Pantex aquifer material was included in the solution matrix. Other experiments using 4000 mg KMnO(4) L(-1) showed that initial RDX concentrations (1.3-10.4 mg L(-1)) or initial pH (4-11) had little effect on reaction rates. Attempts to identify RDX degradates and reaction products showed that N(2)O was a product of permanganate oxidation and constituted 20 to 30% of the N balance. Time-course measurements of a (14)C-RDX solution treated with KMnO(4) revealed few (14)C-labeled degradates but through liquid chromatography-mass spectrometry (LC-MS) analysis, we present evidence that 4-nitro-2,4-diaza-butanol is formed. Aquifer microcosm studies confirmed that the transformation products not mineralized by KMnO(4) were much more biodegradable than parent RDX. These results indicate permanganate can effectively transform and mineralize RDX in the presence of aquifer material and support its use as an in situ chemical oxidation treatment for the Pantex perched aquifer.     

Nitrate removal in a riparian wetland of the Appalachian Valley and Ridge physiographic province

Riparian zones within the Appalachian Valley and Ridge physiographic province are often characterized by localized variability in soil moisture and organic carbon content, as well as variability in the distribution of soils formed from alluvial and colluvial processes. These sources of variability may significantly influence denitrification rates. This investigation studied the attenuation of nitrate (NO3- -N) as wastewater effluent flowed through the shallow ground water of a forested headwater riparian zone within the Appalachian Valley and Ridge physiographic province. Ground water flow and NO3- -N measurements indicated that NO3- -N discharged to the riparian zone preferentially flowed through the A and B horizons of depressional wetlands located in relic meander scars, with NO3- -N decreasing from > 12 to < 0.5 mg L(-1). Denitrification enzyme activity (DEA) attributable to riparian zone location, soil horizon, and NO3- -N amendments was also determined. Mean DEA in saturated soils attained values as high as 210 microg N kg(-1) h(-1), and was significantly higher than in unsaturated soils, regardless of horizon (p < 0.001). Denitrification enzyme activity in the shallow A horizon of wetland soils was significantly higher (p < 0.001) than in deeper soils. Significant stimulation of DEA (p = 0.027) by N03- -N amendments occurred only in the meander scar soils receiving low NO3- -N (<3.6 mg L(-1)) concentrations. Significant denitrification of high NO3- -N ground water can occur in riparian wetland soils, but DEA is dependent upon localized differences in the degree of soil saturation and organic carbon content.     

Effects of arsenic concentrations and forms on arsenic uptake by the hyperaccumulator ladder brake

Ladder brake (Pteris vittata L.) is a newly discovered arsenic hyperaccumulator. No information is available about arsenic effects on ladder brake. This study determined the effects of different arsenic concentrations (50 to 1000 mg kg(-1)) or forms (organic vs. inorganic and arsenite vs. arsenate) applied to soils on growth and arsenic uptake by ladder brake. Young plants were grown in a greenhouse for 12 or 18 wk. Ladder brake was highly tolerant of arsenic and survived in soil containing up to 500 mg As kg(-1). The fact that addition of arsenate up to 100 mg As kg(-1) increased fern biomass by 64 to 107%, coupled with higher arsenic concentration in younger fronds at low soil arsenic concentrations and older fronds at high soil arsenic concentrations, implies that arsenic may be beneficial for fern growth. Addition of 50 mg As kg(-1) was best for fern growth and arsenic accumulation, resulting in the highest fern biomass (3.9 g plant(-1)), bioconcentration factor (up to 63), and translocation factor (up to 25). With an exception of FeAsO4 and AlAsO4, which had the lowest effects due to their low solubility, little difference was observed among other arsenic forms mainly because of arsenic conversion in soil. Aboveground biomass was mostly responsible for accumulation of arsenic by plant (75-99%). Up to 26% of the added arsenic was removed by ladder brake, showing the high efficiency of ladder brake in arsenic removal. The results suggest that ladder brake may be a good candidate to remediate arsenic-contaminated soils.     

Effect of mineral and manure phosphorus sources on runoff phosphorus

Concern over nonpoint-source phosphorus (P) losses from agricultural lands to surface waters has resulted in scrutiny of factors affecting P loss potential. A rainfall simulation study was conducted to quantify the effects of alternative P sources (dairy manure, poultry manure, swine slurry, and diammonium phosphate), application methods, and initial soil P concentrations on runoff P losses from three acidic soils (Buchanan-Hartleton, Hagerstown, and Lewbeach). Low P (12 to 26 mg kg(-1) Mehlich-3 P) and high P (396 to 415 mg kg(-1) Mehlich-3 P) members of each soil were amended with 100 kg total P ha(-1) from each of the four P sources either by surface application or mixing, and subjected to simulated rainfall (70 mm h(-1) to produce 30 min runoff). Phosphorus losses from fertilizer and manure applied to the soil surface differed significantly by source, with dissolved reactive phosphorus (DRP) accounting for 64% of total phosphorus (TP) (versus 9% for the unamended soils). For manure amended soils, these losses were linearly related to water-soluble P concentration of manure (r2 = 0.86 for DRP, r2 = 0.78 for TP). Mixing the P sources into the soil significantly decreased P losses relative to surface P application, such that DRP losses from amended, mixed soils were not significantly different from the unamended soil. Results of this study can be applied to site assessment indices to quantify the potential for P loss from recently manured soils.     

Degree of phosphorus saturation thresholds in manure-amended soils of alberta

The risk of P losses from agricultural land to surface and ground water generally increases as the degree of soil P saturation increases. A single-point soil P sorption index (PSI) was validated with adsorption isotherm data for determination of the P sorption status of Alberta soils. Soil P thresholds (change points) were then examined for two agricultural soils after eight annual applications of different rates of cattle manure and for three agricultural soils after one application of different rates of cattle manure. Linear relationships were found between soil-test P (STP) levels up to 1000 mg kg(-1) and desorbed P in the five Alberta soils. Weak linear relationships were also found between STP and runoff dissolved reactive phosphorus (DRP) in three of these soils. Change points for the degree of P saturation (DPS) were detected in four of the five soils at 3 to 44% for water-extractable P (WEP) and at 11 to 51% for CaCl(2)-extractable P (CaCl(2)-P). Change points were not found for DPS or runoff DRP. Overall DPS thresholds for the five soils combined were 27% for WEP and 44% for CaCl(2)-P at a critical desorbable-P value of 1 mg L(-1). The corresponding STP levels (44 mg kg(-1) for WEP and 71 mg kg(-1) for CaCl(2)-P) are similar to agronomic thresholds for crops grown on Alberta soils. Soluble P losses in overland flow and leaching may be greater in soils with DPS values that exceed these thresholds than in soils with lower DPS values.     

Dissolution of trace element contaminants from two coastal plain soils as affected by pH

Trace element mobility in soils depends on contaminant concentration, chemical speciation, water movement, and soil matrix properties such as mineralogy, pH, and redox potential. Our objective was to characterize trace element dissolution in response to acidification of soil samples from two abandoned incinerators in the North Carolina Coastal Plain. Trace element concentrations in 11 soil samples from both sites ranged from 2 to 46 mg Cu kg(-1), 3 to 105 mg Pb kg(-1), 1 to 102 mg Zn kg(-1), 3 to 11 mg Cr kg(-1), < 0.1 to 10 mg As kg(-1), and < 0.01 to 0.9 mg Cd kg(-1). Acidified CaCl2 solutions were passed through soil columns to bring the effluent solution to approximately pH 4 during a 280-h flow period. Maximum concentrations of dissolved Cu, Pb, and Zn at the lowest pH of an experiment (pH 3.8-4.1) were 0.32 mg Cu L(-1), 0.11 mg Pb L(-1), and 1.3 mg Zn L(-1) for samples from the site with well-drained soils, and 0.25 mg Cu L(-1), 1.2 mg Pb L(-1), and 1.4 mg Zn L(-1) for samples from the site with more poorly drained soils. Dissolved Cu concentration at pH 4 increased linearly with increasing soil Cu concentration, but no such relationship was found for Zn. Dissolved concentrations of other trace elements were below our analytical detection limits. Synchrotron X-ray absorption near edge structure (XANES) spectroscopy showed that Cr and As were in their less mobile Cr(III) and As(V) oxidation states. XANES analysis of Cu and Zn on selected samples indicated an association of Cu(II) with soil organic matter and Zn(II) with Al- and Fe-oxides or franklinite.     

Occurrence of metals in soil and ground water near chromated copper arsenate-treated utility poles

To thoroughly investigate the metal contamination around chromated copper arsenate (CCA)/polyethylene glycol (PEG)-treated utility poles, a total of 189 soil samples obtained from different depths and distances near six treated poles in the Montreal area (Canada) were analyzed for Cu, Cr, and As content. Various soil physicochemical properties were also determined. Ground water samples collected below the poles were analyzed for metals and bioassays with Daphnia magna were conducted. Generally, sandy soils had lower contaminant levels than clayey and organic soils. Copper concentrations in soil were highest followed by As and Cr. The highest Cu (1460 +/- 677 mg kg(-1)), As (410 +/- 150 mg kg(-1)), and Cr (287 +/- 32 mg kg(-1)) concentrations were found at the ground line and immediately adjacent to the pole. Contaminant levels then decreased with distance, approaching background levels within 0.1 m from the pole for Cr and 0.5 m for Cu and As. Chromium and Cu levels generally approached background levels at a depth of 0.5 m. Average As content near the pole on all study sites was three to eight times higher than Quebec's Level C criterion (50 mg kg(-1)), although it dropped to 31 mg kg(-1) at 0.1 m. Results also showed that As persisted up to 1 m in soil depth (17-54 mg kg(-1)). Copper and Cr concentrations in ground water samples were always <1.000 mg L(-1) and <0.05 mg L(-1), respectively and Cr(VI) was <0.02 mg L(-1). One sample contained an As concentration >0.025 mg L(-1) but bioassays showed that, overall, ground water had a low ecotoxic potential.     

Transport of di(2-ethylhexyl)phthalate (DEHP) applied with sewage sludge to undisturbed and repacked soil columns

Municipal sewage sludge is often used on arable soils as a source of nitrogen and phosphorus, but it also contains organic contaminants that may be leached to the ground water. Di(2-ethylhexyl)phthalate (DEHP) is a priority pollutant that is present in sewage sludge in ubiquitous amounts. Column experiments were performed on undisturbed soil cores (20-cm depth x 20-cm diameter) with three different soil types: a sand, a loamy sand, and a sandy loam soil. Dewatered sewage sludge was spiked with 14C-labeled DEHP (60 mg kg(-1)) and bromide (5 g kg(-1)). Sludge was applied to the soil columns either as five aggregates, or homogeneously mixed with the surface layer. Also, two leaching experiments were performed with repacked soil columns (loamy sand and sandy loam soil). The DEHP concentrations in the effluent did not exceed 1.0 microg L(-1), and after 200 mm of outflow less than 0.5% of the applied amount was recovered in the leachate in all soils but the sandy loam soil with homogeneous sludge application (up to 3.4% of the applied amount recovered). In the absence of macropore flow, DEHP in the leachate was primarily sorbed to mobilized dissolved organic macromolecules (DOM, 30.3 to 81.3%), while 2.4 to 23.6% was sorbed to mobilized mineral particles. When macropore flow occurred, this changed to 16.5 to 37.4% (DOM) and 36.9 to 40.6% (mineral particles), respectively. The critical combination for leaching of considerable amounts of DEHP was homogeneous sludge application and a continuous macropore structure.     

Contribution of hydrolysis in the abiotic attenuation of RDX and HMX in coastal waters

Sinking of military ships, dumping of munitions during the two World Wars, and military training have resulted in the undersea deposition of numerous unexploded ordnances (UXOs). Leaching of energetic compounds such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) from these UXOs may cause adverse ecological effects so that the long-term fate of these chemicals in the sea should be known. The present study assesses the contribution of alkaline hydrolysis into the natural attenuation of RDX and HMX in coastal waters. Alkaline hydrolysis rates were shown to be unaffected by the presence of sodium chloride, the most common component in marine waters. Kinetic parameters (E(a), ln A, k(2)) quantified for the alkaline hydrolysis of RDX and HMX in deionized water (30-50 degrees C, pH 10-12) agreed relatively well with abiotic degradation rates determined in sterilized natural coastal waters (50 and 60 degrees C, variable salinity) even if the latter were generally slightly faster than the former. Furthermore, similar products (HCHO, NO(2)(-), O(2)NNHCH(2)NHCHO) were obtained on alkaline hydrolysis in deionized water and abiotic degradation in coastal waters. These two findings suggested that degradation of nitramines in sterilized natural coastal waters, away from light, was mainly governed by alkaline hydrolysis. Kinetic calculations using the present parameters showed that alkaline hydrolysis of RDX and HMX in marine waters at 10 degrees C would respectively take 112 +/- 10 and 2408 +/- 217 yr to be completed (99.0%). We concluded that under natural conditions hydrolysis should not contribute significantly to the natural attenuation of HMX in coastal waters whereas it could play an active role in the natural attenuation of RDX.     

Infiltration and adsorption of dissolved atrazine and atrazine metabolites in buffalograss filter strips

Vegetated filter strips (VFS) potentially reduce the off-site movement of herbicides from adjacent agricultural fields by increasing herbicide mass infiltrated (Minf) and mass adsorbed (Mas) compared with bare field soil. However, there are conflicting reports in the literature concerning the contribution of Mas to the VFS herbicide trapping efficiency (TE). Moreover, no study has evaluated TE among atrazine (6-chloro-N-ethyl-N'-isopropyl-[1,3,5]triazine-2,4-diamine) and atrazine metabolites. This study was conducted to compare TE, Minf, and Mas among atrazine, diaminoatrazine (DA, 6-chloro[1,3,5]triazine-2,4-diamine), deisopropylatrazine (DIA, 6-chloro-N-ethyl-[1,3,5]triazine-2,4-diamine), desethylatrazine (DEA, 6-chloro-N-isopropyl-[1,3,5]triazine-2,4-diamine), and hydroxyatrazine (HA, 6-hydroxy-N-ethyl-N'-isopropyl-[1,3,5]triazine-2,4-diamine) in a buffalograss VFS. Runoff was applied as a point source upslope of a 1- x 3-m microwatershed plot at a rate of 750 L h(-1). The point source was fortified at 0.1 microg mL(-1) atrazine, DA, DIA, DEA, and HA. After crossing the length of the plot, water samples were collected at 5-min intervals. Water samples were extracted by solid phase extraction and analyzed by high performance liquid chromatography (HPLC) photodiode array detection. During the 60-min simulation, TE was significantly greater for atrazine (22.2%) compared with atrazine metabolites (19.0%). Approximately 67 and 33% of the TE was attributed to Minf and Mas, respectively. These results demonstrate that herbicide adsorption to the VFS grass, grass thatch, and/or soil surface is an important retention mechanism, especially under saturated conditions. Values for Mas were significantly higher for atrazine compared with atrazine's metabolites. The Mas data indicate that atrazine was preferentially retained by the VFS grass, grass thatch, and/or soil surface compared with atrazine's metabolites.     

Degradation of N,N'-dibutylurea (DBU) in soils treated with only DBU and DBU-fortified benlate fungicides

N,N'-dibutylurea (DBU) is a breakdown product of benomyl [methyl 1-(butylcarbamoyl)-2-benzimidazole carbamate], the active ingredient in Benlate fungicides, and has been proposed to cause crop damage after the use of Benlate 50 DF fungicide (DuPont, Wilmington, DE). Our research focused on DBU persistence after application into soil. We assessed DBU persistence on direct application of DBU (carbonyl-(14)C) at two concentrations (0.08 and 0.8 microg DBU kg(-1)) to seven soils and two potting mixes in soil microcosms incubated at various combinations of soil water potential (-0.03 or -0.1 MPa) and temperature (23, 33, 44 degrees C). For two soils at a subset of treatment variables we assessed DBU persistence in the presence of Benlate DF and SP fungicide formulations. Parent compounds, metabolites, and (14)CO(2) were tracked using chromatographic analysis with radioassay and UV detection, liquid scintillation counting, and post-extraction oxidation of the soil. DBU degradation was primarily microbial and for most soil-treatment combinations, half-lives were less than 2 wk. DBU degradation was retarded at the lower soil water potential and enhanced at 33 degrees C. In the presence of the formulation, DBU degradation was slower for one soil type. The longest half-life observed in any case was less than 7 wk; therefore, long-term persistence of DBU applied to soils through a Benlate application is very unlikely.     

Environmental impacts of training activities at an air weapons range

Within Canada, it has been recognized in the last decade that military training activities may have impacts on the environmental quality of training ranges. However, impacts of activities specific to Air Force Bases have not yet been intensely documented. A hydrogeological study was accomplished at the Cold Lake Air Weapons Range, Alberta, to evaluate the environmental impacts of using bombs, rockets, strafing, and open burning/open detonation (OB/OD) on the quality of soil, ground water, surface water, and lake sediments. Samples were analyzed for metals, anions, ammonium perchlorate (NH(4)ClO(4)), and energetic materials (EM). It was found that training activities did not result in measured values being exceeded on the basis of guidance values for surface water and lake sediments. Contamination by metals was mostly limited to soils, and some metals may be related to the use of bombs (Cd, Cu, Pb), strafe (Cu), and rockets (As, Ba, Cd, Cr, Cu, Fe, Ni, Pb, U, V, Zn). TNT (2,4,6-trinitrotoluene) was the main EM found in soils, while RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) was more common in ground water. Both are related to live bombing, while nitroglycerine (NG) is related to rocket use and was detected in soils only. Aluminum, nitrate, and ammonium perchlorate detected in ground water may be related to live bombing or rockets. OB/OD operations resulted in the presence of various EM in soils, and of perchlorate and nitrate in ground water. Contamination by metals and explosives in soils was localized around the targets and varied significantly in time; however, in ground water it was more constant and may persist for a period of several years after a target has been removed.     

Fungal inoculum properties: extracellular enzyme expression and pentachlorophenol removal in highly contaminated field soils

This study was conducted to improve the pentachlorophenol (PCP) bioremediation ability of white-rot fungi in highly contaminated field soils by manipulating bioaugmentation variables. These were the dry weight percentage of fungal inoculum addition (31-175 g kg(-1)), PCP concentration (100-2137 mg kg(-1) PCP), fungal inoculum formulation, and time (1-7 wk). Five fungal isolates were used: the New Zealand isolates Trametes versicolor (L.: Fr.) HR131 and Trametes sp. HR577; the North American isolates Phanerochaete chrysosporium Burds. (two isolates) and Phanerochaete sordida (Karst.) Erikss. & Ryv. Pentachlorophenol removal, manganese peroxidase, and laccase activity, and the formation of chloroanisoles in the contaminated field soils were measured. The majority of PCP removed by the Trametes isolates was in the first week after bioaugmentation. The maximum PCP removal by the fungi varied from 50 to 65% from a 1065 mg kg(-1) PCP contaminated field soil. Pentachlorophenol was preferentially converted to pentachloroanisole (PCA) by the Phanerochaete isolates (>60%), while 2 to 9% of the PCP removed by two Trametes isolates was converted to PCA. A pH increase was measured following bioaugmentation that was dependent on PCP concentration, fungal inoculum addition, and formulation. This, together with rapid initial PCP removal, possibly changed the bioavailability of the remaining PCP to the fungi and significantly decreased the sequestering of PCP in the contaminated field soils. The research supports the conclusion that New Zealand Trametes spp. can rapidly remove PCP in contaminated field soils. Bioavailability and extractability of PCP in the contaminated field soil may significantly increase after bioaugmentation.     

Organic agriculture and nitrous oxide emissions at sub-zero soil temperatures

In the Red River Valley of the upper midwestern United States, soil temperatures often remain below freezing during winter and N2O emissions from frozen cropland soils is assumed to be negligible. This study was conducted to determine the strength of N2O emissions and denitrification when soil temperatures were below zero for a manure-amended, certified organic field (T2O) compared with an unamended, conventionally managed field (T2C). Before manure application, both fields were similar with respect to autotrophic and heterotrophic N2O production and N2O flux at the soil surface (0.15+/-0.05 mg N2O-N m-2 d-1 for T2O and 0.12+/-0.06 mg N2O-N m-2 d-1 for T2C). After application of pelletized, dehydrated manure, average daily flux (based on time-integrated fluxes from 20 November to 8 April), was 1.19+/-0.34 mg N2O-N m-2 d-1 for T2O and 0.47+/-0.37 mg N2O-N m-2 d-1 for T2C. Denitrification for intact cores measured in the laboratory at -2.5 degrees C was greater for organically managed soils, although only marginally significant (p<0.1). Cumulative emissions for all winter measurements (from 16 November to 8 April) averaged 1.63 kg N2O-N ha-1 for T2O and 0.64 kg N2O-N ha-1 for T2C. Biological N2O production was evident at sub-zero soil temperatures, with winter emissions exceeding those measured in late summer. Late autumn manure application enhanced cumulative N2O-N emissions by 0.9 kg ha-1.     

An alum-based water treatment residual can reduce extractable phosphorus concentrations in three phosphorus-enriched coastal plain soils

The accumulation of excess soil phosphorus (P) in watersheds under intensive animal production has been linked to increases in dissolved P concentrations in rivers and streams draining these watersheds. Reductions in water dissolved P concentrations through very strong P sorption reactions may be obtainable after land application of alum-based drinking water treatment residuals (WTRs). Our objectives were to (i) evaluate the ability of an alum-based WTR to reduce Mehlich-3 phosphorus (M3P) and water-soluble phosphorus (WSP) concentrations in three P-enriched Coastal Plain soils, (ii) estimate WTR application rates necessary to lower soil M3P levels to a target 150 mg kg(-1) soil M3P concentration threshold level, and (iii) determine the effects on soil pH and electrical conductivity (EC). Three soils containing elevated M3P (145-371 mg kg(-1)) and WSP (12.3-23.5 mg kg(-1)) concentrations were laboratory incubated with between 0 and 6% WTR (w w(-1)) for 84 d. Incorporation of WTR into the three soils caused a near linear and significant reduction in soil M3P and WSP concentrations. In two soils, 6% WTR application caused a soil M3P concentration decrease to below the soil P threshold level. An additional incubation on the third soil using higher WTR to soil treatments (10-15%) was required to reduce the mean soil M3P concentration to 178 mg kg(-1). After incubation, most treatments had less than a half pH unit decline and a slight increase in soil EC values suggesting a minimal impact on soil quality properties. The results showed that WTR incorporation into soils with high P concentrations caused larger relative reductions in extractable WSP than M3P concentrations. The larger relative reductions in the extractable WSP fraction suggest that WTR can be more effective at reducing potential runoff P losses than usage as an amendment to lower M3P concentrations.