Background/Object. At the D firing range, located in Y City, Korea, contamination by2,4,6-trinitrotoluene (TNT), a nitroaromatic explosive, and Pb~(2+), Cu~(2+), Cd~(2+), and Zn~(2+),divalent cationic heavy metals, generated from unexploded ordinances (UXOs) is anemerging environmental issue. The main issue of the D firing range is solid runoff of thecontaminated soil to the H River, adjacent to the D firing range. However, active UXOremoval actions are not applicable as the removal actions may interrupt ongoing firingactivities. Onsite monopotassium phosphate (MKP) spreading technology, which doesnot interrupt firing activities, can be a promising technology that can reduce the leachabilityof both nitroaromatic explosives and divalent cationic heavy metals. To verifywhether MKP can be used to reduce leachability of both explosives and heavy metals,leach tests of the contaminated soils in the presence or absence of MKP was conducted.Approach/Activities. To conduct leach tests, two soil samples of 50 g each, collected inthe D firing range, were artificially contaminated with TNT, Pb~(2+), Cu~(2+), Cd~(2+), and Zn~(2+).The initial concentrations of TNT, Pb~(2+), Cu~(2+), Cd~(2+), and Zn~(2+) were 0.7, 4, 12, 0.2 and12 mmol/kg, respectively. One soil sample was given 2.5 g of MKP (5% of total mass),while the other soil sample was not treated. The moisture contents were maintained at 10%(60% of maximum water holding capacity) during the 7 d incubation period. The leachtest was conducted following the synthetic precipitation leach procedure (SPLP). Briefly,2.37 g of soils (2.15 g of soil particles and 0.215 g of water) were leached by 43 mL ofsynthetic precipitate (pH 4.2 of deionized water containing 60/40 weight percent mixtureof H2SO4 and HNO3) in 50 mL Teflon tubes for 18 hours. After the leach test, the tubeswere centrifuged, and the supernatants were collected for the contaminants concentrationanalysis in the leachates.Results/Lessons Learned. The leach test results showed that leachable fraction of bothTNT and heavy metals is reduced in the presence of MKP. In the absence of MKP, theleachable fractions of TNT, Pb~(2+), Cu~(2+), Cd~(2+), and Zn~(2+) were 94.5, 6.1, 16.9, 44.7, and42.9% of the initial concentrations, respectively. On the other hand, in the presence ofMKP, the leachable fractions of those contaminants were reduced to 56.4, 2.8, 0.9, 5.7,and 6.5%, respectively. Potassium ion in MKP enhances TNT sorption onto soil by enablingthe n-π interaction between TNT and clay minerals surface. In addition, phosphateion in MKP makes heavy metals less leachable by forming heavy metal phosphate, whichis rarely leachable in natural environment. Our preliminary sorption/ desorption test ofTNT revealed that the Freundlich sorption coefficient in the presence of MKP is aboutfour times higher than that in the absence of MKP. In addition, TNT desorbability is alsoreduced in the presence of MKP. The desorbed fraction of TNT in the presence or absenceof MKP was 30% and 58%, respectively. These data suggest that MKP spreading
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