Toxicity of RDX, HMX, TNB, 2,4-DNT, and 2,6-DNT to the Earthworm, Eisenia Fetida, in a Sandy Loam Soil

Abstract : The U.S. Environmental Protection Agency is developing Ecological Soil Screening Levels (Eco-SSLs) for ecological risk assessment of soil contaminants at Superfund sites. Insufficient information existed to generate Eco-SSLs for explosives and related materials in soil. The earthworm (Eisenia fetida) reproduction test was conducted in Sassafras sandy loam soil amended with hexahydro-1,3 ,5-trinitro-1,3 5-triazine (RDX), octahydro-1 3,5,7-tetranitro-1,3 ,5,7-tetrazocine (HMX), 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), and 1,3,5-trinitrobenzene (TNB) to fill the data gaps. Tests were conducted in freshly amended and in amended soils subjected to a weathering/aging process to better reflect exposure conditions in field soils. The order of toxicity in freshly amended soils, based on EC(sub 20) values for E. fetida juvenile production derived from non-linear regression analysis, was HMX >RDX > 2,6-DNT> TNB > 2,4-DNT. The order of toxicity of weathered/aged energetic materials in amended soils was RDX > 2,6-DNT > TNB > 2,4-DNT> HMX. Correlation of soil concentration with toxicity did not change when toxicity data were regressed with water extractable concentrations compared to acetonitrile extractable concentrations. Study results will be provided to the Eco-SSL workgroup for review and inclusion in the Eco-SSL database, and for developing Eco-SSLs for RDX, HMX, 2,4-DNT, 2,6-DNT, and TNB.