2,4,6-Trinitrotoluene

CAS RN:118-96-7

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), an average Koc value of 1,600(2) indicates that 2,4,6-trinitrotoluene is expected to have low mobility in soil(SRC). Volatilization of 2,4,6-trinitrotoluene from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 2.1X10-8 atm-cu m/mole(SRC), derived from its vapor pressure of 8.02X10-6 mm Hg(3) and water solubility of 115 mg/L(4). 2,4,6-Trinitrotoluene is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(3). Biodegradation of 2,4,6-trinitrotoluene in soil will be of minor importance; however 2,4,6-trinitrotoluene is readily reduced under anaerobic conditions(5). Microbial transformation of 2,4,6-trinitrotoluene leads to a variety of reduction products, including 2-amino and 4-amino dinitrotoluene and azoxydimers(3,5,7). Limited information regarding photolytic processes in soil suggest that 2,4,6-trinitrotoluene in surface layers is photolyzed to trinitrobenzene and trinitrobenzaldehyde(8). Gas chromatography-electron capture measurements demonstrated that a sea water solution at a pH of 8.1 with 95 ppm 2,4,6-trinitrotoluene underwent no change in concn after 108 days(7), thus evidencing the stability of 2,4,6-trinitrotoluene against hydrolysis in water under neutral conditions(9).
TERRESTRIAL FATE: Phytoremediation of 2,4,6-trinitrotoluene has shown that metabolism takes place in three stages; transformation (formation of 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene), conjugation, and sequestration (formation of bound residues within the plant)(1). Hybrid poplar trees planted in 2,4,6-trinitrotoluene contaminated soil from Iowa Army Ammunition Plant showed an uptake of 25% 2,4,6-trinitrotoluene in 20 days(2). 75% of the 2,4,6-trinitrobenzene was found in the roots, 17% in the stems and 6% in the leaves(2).
AQUATIC FATE: Based on a classification scheme(1), an average Koc value of 1,600(2) indicates that 2,4,6-trinitrotoluene is expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 2.1X10-8 atm-cu m/mole(SRC), derived from its vapor pressure of 8.02X10-6 mm Hg(4) and water solubility of 115 mg/L(5). According to a classification scheme(6), an estimated BCF of 3.4(SRC), from its log Kow of 1.60(7) and a regression-derived equation(8), suggests the potential for bioconcentration in aquatic organisms is low(SRC). The capability of microorganisms to biotransform 2,4,6-trinitrotoluene seems well established(2,9-11); however, reduction rates under aerobic conditions are very slow. Photolysis studies comparing river waters and distilled water have shown that the rate of 2,4,6-trinitrotoluene photolysis is directly related to increases in pH(10-11) and organic matter content(2). In the presence of oxygen, 10 ppm of 2,4,6-trinitrotoluene added to a freshwater bay sample remained unchanged for 20 days then following first order kinetics with an estimated half-life of 25 days and dropped to 3 ppm within 64 days(2). 2,4,6-Trinitrotoluene at an initial concn of 20 ppm within the dark control bottle of a river die away study underwent a 90% reduction within 30 days(11). However biotransformation was identified to be 100-1000 times slower than photolytic processes(2,11). Gas chromatography-electron capture measurements demonstrated that a sea water solution at a pH of 8.1 with 95 ppm 2,4,6-trinitrotoluene underwent no change in concn after 108 days(12), thus evidencing the stability of 2,4,6-trinitrotoluene against hydrolysis in water under neutral conditions(13).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 2,4,6-trinitrotoluene, which has a vapor pressure of 8.02X10-6 mm Hg at 25 deg C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase 2,4,6-trinitrotoluene is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 120 days(SRC), calculated from its rate constant of 1.4X10-13 cu cm/molecule-sec at 25 deg C(SRC) that was derived using a structure estimation method(3). Particulate-phase 2,4,6-trinitrotoluene may be removed from the air by wet or dry deposition(SRC). The rate constants for river water, seawater, pond water and distilled water were 1.2X10-3, 1.5X10-4, 5.8X10-4 and 1.7X10-5/sec, respectively, which correspond to half-lives of about 10 min, 1.3 hrs, 20 min and 11.3 hrs(4).
Lab scale compost systems can be used for the estimation of the degradation rates of hazardous materials in a compost and to identify the degradation products. Composting /consisted of/ chopped alfalfa hay 45, horse feed 45, and soil 10% contaminated with explosives ... TNT was rapidly transformed into nonextractable cmpd which resembled humus matrials. ... TNT showed no ring degradation. The amount of leachable TNT declined with its increasing biotransformation.
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