Steven L. Larson

Phytotreatment of TNT-Contaminated Groundwater

Phytoremediation is a viable technique for treating nitroaromatic compounds, particularly munitions. Continuous flow phyto-reactor studies were conducted at the following three influent concentrations of 2,4,6-trinitrotoluene (TNT): 1, 5, and 10u2009ppm. A control was also prepared with an influent TNT concentration of 5 ppm. Flow rates were systematically reduced to increase hydraulic retention times (HRT) which ranged from 12 to 76 days. Initially, the control reactor removed TNT as efficiently as the plant reactors. With time, however, the efficiency of the control became less than that of the plant reactors, suggesting that adsorption was initially the mechanism for removal. Up to 100% of the TNT was removed. Aminodinitrotoluene (ADNT) effluent concentration was higher for higher TNT influent concentrations. Increasing the retention time reduced ADNT concentration in the effluent. Supplementary batch studies confirmed that ADNT and diaminonitrotoluene (DANT) were phytodegraded. Preliminary batch studies w...

Sterilization of Plants for Phytoremediation Studies by Bleach Treatment

ABSTRACT Bleach treatment of plants was studied as a simple alternative to axenic tissue cultures for demonstrating phytodegradation of aqueous and gas-phase environmental contaminants. Parrotfeather (Myriophyllum aquaticum), spinach (Spinacia oleracea), and wheat (Triticum aestivum) were exposed to 0.525% NaC10 solutions for 15 s, then rinsed in deionized water. Plate counts indicated that 97 to 100% of viable bacteria were removed from parrotfeather and spinach. Transformation rates for 2,4,6-trinitrotoluene (TNT) by bleached and untreated parrotfeather were virtually identical. Similarly, treated and untreated spinach, wheat heads, and wheat leaves removed methyl bromide (MeBr) from air at the same rates. However, wheat root with attendant adhering soil was rendered inactive by bleach treatment. Parrotfeather roots examined by dissecting microscope and by electron microscope showed no significant damage caused by bleach treatment.

Corrosion and migration of zero-valent depleted uranium products in soil

Zero-valent metallic depleted uranium (DU) penetrators exposed in the environment after firing frequently undergo corrosion. Unlike previous field studies, this report evaluates metallic DU corrosion in a controlled laboratory setting using a 28 day wet–dry cycling method to simulate environmental corrosion. Carried out in construction-grade sand, the study evaluated the effect of three solutions: deionized (DI) water, 3.5% salt (NaCl) solution, and an acid solution. Two oxidation products in the reactors were noted at 14 days, both in the sand and on the penetrator. Oxidation product migrated to the sand media; the higher percentage of migration came from the corrosion fluid that produced the least amount of corrosion. Changes in mass percentages of uranium and oxygen correlated with density changes, as evidenced by relative brightness, to show differences in corrosion. Other elements (sodium, magnesium, iron, and calcium) increased in mass percentage with increasing corrosion. Five soil types were also used to corrode DU. Multiple soil physical and chemical characteristics appear to contribute to differences in the rates of corrosion, including soil pH, percentage of soil fines, and total organic carbon content. These studies suggest that limiting moisture and salt exposure could reduce corrosion of exposed DU and subsequent migration. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.

Development and characterization of small-scale washing systems for removal of depleted uranium oxides

Researchers from the Mississippi State University Institute for Clean Energy Technology (MSU-ICET) and the U.S. Army Engineer Research and Development Center (ERDC) have identified procedures and methodologies for identifying leaching solutions to assist in the removal of depleted uranium (DU) oxides from contaminated soils. They developed a benchscale leach system to optimize leaching procedures and methodologies. This study identified that a 2 molar (M) acetic-acid solution with a 15% (v/v) 0.3 M hydroxylamine hydrochloride solution could remove approximately 70% of the uranium in the soil sample. Pretreating the soil with 3 M hydrochloric acid improved leaching efficiency to approximately 90%. The MSU-ICET research team developed the preliminary design of a mobile leaching system based on the hydrochloric-acid pretreatment followed by 2 M acetic acid / 15% (v/v) 0.3 M hydroxylamine hydrochloride leaching method. The trailer heap leach system is designed to be used on-site, eliminating the need for additional transport of radioactive, contaminated soils. This will reduce the risk of radioactive exposure for personnel and will eliminate potentially serious transportation accidents. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.

Sustainable carbon dioxide sequestration as soil carbon to achieve carbon neutral status for DoD lands

Abstract : Sequestration of atmospheric carbon dioxide in soils is a promising alternative for mitigation of atmospheric carbon dioxide (CO2). The Department of Defense (DoD) owns significant land and water resources which can be managed to offset emissions. Accounting for this, sequestration could help DoD reach carbon neutrality. Many activities the DoD engages in for sustainable land management and training sustainment are conducive to soil carbon storage without even considering this as an important component; however, carbon storage could be greatly enhanced by increased understanding of optimal storage conditions and by making slight adjustments to existing practices. Land management techniques may require adjustments to maximize carbon storage while maintaining training and environmental quality. In order to achieve this, data gaps for estimating carbon fluxes need to be addressed so that accurate measurements can be taken. Unknown aspects of carbon storage as it relates to plant-soil-soil microbe interations need to be investigated to maximize carbon storage while maintaining land use requirements. Geo-engineering concepts require further refinement to increase carbon storage in soils. These knowledge gaps are not insurmountable and could be addressed through focused research to maximize and accurately quantify carbon storage on DoD lands.