Weathering and aging of 2,4,6‐trinitrotoluene in soil increases toxicity to potworm Enchytraeus crypticus

Abstract

Energetic materials are employed in a wide range of commercial and military activities and often are released into the environment. Scientifically based ecological soil-screening levels (Eco-SSLs) are needed to identify contaminant explosive levels in soil that present an acceptable ecological risk. Insufficient information for 2,4,6-trinitrotoluene (TNT) to generate Eco-SSLs for soil invertebrates necessitated toxicity testing. We adapted the standardized Enchytraeid Reproduction Test and selected Enchytraeus crypticus for these studies. Tests were conducted in Sassafras sandy loam soil, which supports relatively high bioavailability of TNT. Weathering and aging procedures for TNT amended to test soil were incorporated into the study design to produce toxicity data that better reflect the soil exposure conditions in the field compared with toxicity in freshly amended soils. This included exposing hydrated TNT-amended soils in open glass containers in the greenhouse to alternating wetting and drying cycles. Definitive tests showed that toxicity for E. crypticus adult survival and juvenile production was increased significantly in weathered and aged soil treatments compared with toxicity in freshly amended soil based on 95% confidence intervals. The median effect concentration and 20% effective concentration for reproduction were 98 and 77 mg/kg, respectively, for TNT freshly amended into soil and 48 and 37 mg/kg, respectively, for weathered and aged TNT soil treatments. These findings of increased toxicity to E. crypticus in weathered and aged TNT soil treatments compared with exposures in freshly amended soils show that future investigations should include a weathering and aging component to generate toxicity data that provide more complete information on ecotoxicological effects of energetic contaminants in soil.

Selenium toxicity to survival and reproduction of Collembola and Enchytraeids in a sandy loam soil

“…Juvenile production was the more sensitive measurement endpoint for assessing Se toxicity to E. crypticus compared with adult survival, which comports with results of our previous studies [21][22][23][25][26][27]. Adult survival was significantly (p < 0.0001) decreased at the 11.35 mg/kg (bounded LOEC) treatment compared with the negative control.…”

“…These procedures allowed us to more accurately approximate the exposure conditions for soil biota in the field, compared with tests conducted with freshly amended chemicals or tests conducted following a short equilibration period (e.g., 24 h) [22][23][24][25][26]28]. The range-finding tests were conducted to determine Se concentrations for the definitive toxicity testing.…”

Toxicity of 2,4-dinitrotoluene to terrestrial plants in natural soils

“…An experimental method for soil WHC (Earl, 2003) was modified to include evaporation and drainage, using three sub-samples of soil below the surface at depth-midpoints within free drainage containers (conventional 8″ pots; nominal 20 cm diameter, and height) as a function of time (days); soil moisture content was gravimetrically determined (FAO, 2007), and the WHC reported as the average of the resulting steady state soil moisture contents. Amended soils were subjected to natural light conditions, and wetting and drying cycles in a greenhouse for 13 weeks, as described in Rocheleau et al (2006) and Kuperman et al (2005),t oa p p r o x i m a t efield exposure conditions for plants in terms of bioavailability, transformation and degradation of 2,4-DNT prior to toxicity testing. At the end of the 13-week weathering-and-aging period, each soil batch was hydrated with ASTM type I water to 75% of the WHC prior to the initiation of the plant toxicity tests.…”

Phytotoxicity and uptake of nitroglycerin in a natural sandy loam soil

“…The procedure for weathering-and-aging organic energetic chemicals in soil has been described elsewhere (Kuperman et al, 2005;Rocheleau et al, 2006). Briefly, weathering-and-aging of NG in soil included exposing individual hydrated soil batches in open glass containers at ambient temperatures in the greenhouse to alternating moistening-and-drying cycles for 1 month.…”