Toxicity and bioaccumulation of reduced TNT metabolites in the earthworm Eisenia andrei exposed to amended forest soil

Soils contaminated with 2,4,6-trinitrotoluene (TNT) and TNT primary reduction products have been found to be toxic to certain soil invertebrates, such as earthworms. The mechanism of toxicity of TNT and of its by-products is still not known. To ascertain if one of the TNT reduction products underlies TNT toxicity, we tested the toxicity and bioaccumulation of TNT reduction products. 2-Amino-4,6-dinitrotoluene (2-ADNT), 4-amino-2,6-dinitrotoluene (4-ADNT), 2,4-diamino-6-nitrotoluene (2,4-DANT) and 2,6-diamino-4-nitrotoluene (2,6-DANT) were tested separately in adult earthworms (Eisenia andrei) following a 14-d exposure to amended sandy loam forest soil. TNT, 4-ADNT, and 2-ADNT were lethal to earthworms (14-d LC50 were: 580, 531 and 1088 mumol kg-1, or 132, 105 and 215 mg kg-1 dry soil, respectively) and gave the following order of toxicity: 4-ADNT > TNT > 2-ADNT. Exposure to 2,4-DANT and to 2,6-DANT caused no mortality at 600 mumol kg-1 or 100 mg kg-1 dry soil. We found that all four TNT reduction products accumulated in earthworm tissues and 2-ADNT reached the highest levels at 3.0 +/- 0.3 mumol g-1 tissue. The 14-d bioaccumulation factors were 5.1, 6.4, 5.1 and 3.2 for 2-ADNT, 4-ADNT, 2,4-DANT and 2,6-DANT, respectively. Results also suggest that some TNT metabolites are at least as toxic as TNT and should be considered when evaluating the overall toxicity of TNT-contaminated soil to earthworms. Crown Copyright Copyright 2003 Published by Elsevier Ltd. All rights reserved.No de contr\ufffdle 93189765NRC publication: Ye

Reproductive and behavioral responses of earthworms exposed to nano-sized titanium dioxide in soil

Nanometer-sized titanium dioxide (nano-TiO2) is found in a number of commercial products; however, its effects on soil biota are largely unknown. In the present study, earthworms (Eisenia andrei and Eisenia fetida) were exposed to three types of commercially available, uncoated TiO2 nanomaterials with nominal diameters of 5, 10, and 21\u2009nm. Nanomaterials were characterized for particle size, agglomeration, surface charge, chemical composition, and purity. Standard lethality, reproduction, and avoidance tests, as well as a juvenile growth test, were conducted in artificial soil or field soil amended with nano-TiO2 by two methods, liquid dispersion and dry powder mixing. All studies included a micrometer-sized TiO2 control. Exposure to field and artificial soil containing between 200 and 10,000\u2009mg nano-TiO2 per kilogram of dry soil (mg/kg) had no significant effect (p\u2009>\u20090.05) on juvenile survival and growth, adult earthworm survival, cocoon production, cocoon viability, or total number of juveniles hatched from these cocoons. However, earthworms avoided artificial soils amended with nano-TiO2. The lowest concentration at which avoidance was observed was between 1,000 and 5,000\u2009mg nano-TiO2 per kilogram of soil, depending on the TiO2 nanomaterial applied. Furthermore, earthworms differentiated between soils amended with 10,000\u2009mg/kg nano-TiO2 and micrometer-sized TiO2. A positive relationship between earthworm avoidance and TiO2 specific surface area was observed, but the relationship between avoidance and primary particle size was not determined because of the agglomeration and aggregation of nano-TiO2 materials. Biological mechanisms that may explain earthworm avoidance of nano-TiO2 are discussed. Results of the present study indicate that earthworms can detect nano-TiO2 in soil, although exposure has no apparent effect on survival or standard reproductive parameters.Peer reviewed: YesNRC publication: Ye

Assessment of a sewage sludge treatment on cadmium, copper and zinc bioavailability in barley, ryegrass and earthworms

The toxicity and bioavailability of metals were assessed to verify the efficiency of a new chemical leaching process (METIX-AC) to minimizethe risk of metals found in municipal sewage sludge. For this purpose, sludge samples were spiked with cadmium, copper and/or zincbefore being treated using METIX-AC. The sludge decontamination resulted in a removal of spiked metals (79e89%), in a decrease of themore labile fractions, and in a corresponding increase of the residual fraction. The toxicity observed after exposure of two plant species, barley(Hordeum vulgare) and ryegrass (Lolium perenne), and a terrestrial invertebrate, Eisenia andrei, to sludge-soil mixtures, disappeared after treatment, although the adverse effects were minor before treatment. The sludge treatment also significantly decreased the bioaccumulation of cadmium, copper, and zinc in the exposed species. For cadmium, maximum tissue concentrations of 0.45 0.08 mg/kg in barley, 0.79 0.27 mg/kg in ryegrass, and 21.82 1.85 mg/kg in earthworm exposed to sludge before treatment decreased after treatment to values similar to thoseobserved with negative controls.NRC publication: Ye

Ecotoxicological assessment of a high energetic and insensitive munitions compound : 2,4-Dinitroanisole (DNAN)

The high explosive nitroaromatic 2,4-dinitroanisole (DNAN) is less shock sensitive than 2,4,6-trinitrotoluene (TNT), and is proposed as a TNT replacement for melt-cast formulations. Before using DNAN in munitions and potentially leading to environmental impact, the present study examines the ecotoxicity of DNAN using selected organisms. In water, DNAN decreased green algae Pseudokirchneriella subcapitata growth (EC50=4.0mg/L), and bacteria Vibrio fischeri bioluminescence (Microtox, EC50=60.3mg/L). In soil, DNAN decreased perennial ryegrass Lolium perenne growth (EC50=7mg/kg), and is lethal to earthworms Eisenia andrei (LC50=47mg/kg). At sub-lethal concentrations, DNAN caused an avoidance response (EC50=31mg/kg) by earthworms. The presence of DNAN and 2-amino-4-nitroanisole in earthworms and plants suggested a role of these compounds in DNAN toxicity. Toxicity of DNAN was compared to TNT, tested under the same experimental conditions. These analyses showed that DNAN was equally, or even less deleterious to organism health than TNT, depending on the species and toxicity test. The present studies provide baseline toxicity data to increase the understanding of the environmental impact of DNAN, and assist science-based decision makers for improved management of potential DNAN contaminated sites. \ua9 2013.Peer reviewed: YesNRC publication: Ye

Role of soil interstitial water in the accumulation of hexahydro-1,3,5-trinitro-1,3,5-triazine in the earthworm Eisenia andrei

The uptake of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) from soil by the earthworm Eisenia andrei was examined by using the equilibrium partitioning (EqP) theory and a three-compartment model including soil (S), interstitial water (IW), and earthworms (E). The RDX concentrations were measured using U.S. Environmental Protection Agency (U.S. EPA) Method 8330A and high-performance liquid chromatography (HPLC). The S-IW studies were conducted using four natural soils with contrasting physicochemical properties that were hypothesized to affect the bioavailability of RDX. Each soil was amended with nominal RDX concentrations ranging from 1 to 10,000 mg/kg. The HPLC analysis showed that the IW extracted from soil was saturated with RDX at 80 mg/kg or greater soil concentrations. The calculated S-IW coefficient (Kp) values for RDX ranged from 0.4 to 1.8 ml/g soil, depending on the soil type, and were influenced by the organic matter content. In the IW-E studies, earthworms were exposed to nonlethal RDX concentrations in aqueous media. The uptake of RDX by the earthworms correlated well (r\ub2 = 0.99) with the dissolved RDX concentrations. For the E-S studies, earthworms were exposed to RDX-amended soils used in the S-IW studies. The bioconcentration factors (BCF; ratios of E-to-IW RDX concentrations) were relatively constant (~5) up to 80 mg/kg soil RDX concentrations, which encompass the RDX saturation limit in the interstitial water of the tested soils. At this concentration range, the RDX uptake from interstitial water was likely dominated by passive diffusion and could be used as an indicator of bioavailability. Other mechanisms may be involved at greater RDX soil concentrations.Peer reviewed: YesNRC publication: Ye

Enhanced biodegradation of petroleum hydrocarbons in contaminated soil

Soil samples taken from a contaminated site in Northern Quebec, Canada, exhibited a low capacity for biodegradation of total petroleum hydrocarbons (TPH), despite a high capacity for the mineralization of aromatic hydrocarbons and a low toxicity of soil leachates as measured by Microtox assay. Toxicity assays directly performed on surface soil, including earthworm mortality and barley seedling emergence, indicated moderate to high levels of toxicity. Soil biostimulation did not improve the removal of petroleum hydrocarbons, while bioaugmentation of soil with a developed enrichment culture increased the efficiency of hydrocarbon removal from 20.4% to 49.2%. A considerable increase in the removal of TPH was obtained in a bioslurry process, enhancing the mass transfer of hydrocarbons from soil to the aqueous phase and increasing the efficiency of hydrocarbon removal to over 70% after 45 days of incubation. The addition of ionic or nonionic surfactants did not have a significant impact on biodegradation of hydrocarbons. The extent of hydrocarbon mineralization during the bioslurry process after 45 days of incubation ranged from 41.3% to 58.9%, indicating that 62.7% to 83.1% of the eliminated TPH were transformed into CO\u2082 and water.NRC publication: Ye

Ecotoxicity of canola and tallow biodiesel blends to selected soil organisms

In view of depleting fossil fuel resources and environmental concern, biodiesel couldpotentially replace petroleum-derived diesel. Aquatic toxicity of diesel and biodiesel has beenextensively studied over the past decades but little is still known about their toxicity in soilenvironment. The scope of this study was to evaluate the environmental impact of biodiesel,biodiesel blends and petroleum diesel in soil using direct contact toxicity assays. The selectedbiodiesels included canola-source biodiesel (B100 and B20). and tallow-source biodiesel (B100and B20), which were compared to petroleum ultra-low-sulfur based diesel (ULSD). Selectedstandard terrestrial toxicity tests included ryegrass Lolium perenne seedling emergence andgrowth, earthworm Eisenia fetida survival, and soil microbial dehydrogenase activity. Soilcharacterization included the quantification of total extractable materials (corresponding to the n-alkane range of C10-C34). Preliminary results indicate that: 1) canola and tallow B20 biodieselblends were less toxic to earthworm than ULSD; 2) canola and tallow B20 blends had similartoxic effects to ryegrass as ULSD; and 3) petroleum ULSD inhibited the DHA activity at allconcentrations tested, and B20 canola biodiesel had a deleterious effect on the DHA activity atthe lowest nominal loadings tested (1 and 10 ml/kg dry soil). Therefore, this study providesuseful toxicological data for the evaluation of potential adverse impact of biodiesel in theenvironment, such as an accidental release or spill. This project was funded by EnvironmentCanada and Natural Resources Canada and is part of the Advanced Fuels and Technologies forEmissions Reduction (AFTER) Program for energy research and development (PERD).NRC publication: Ye

Toxicity assessment of contaminated soils from an antitank firing range

Explosives are released into the environment at production and processing facilities, as well as through field use. These compounds may be toxic at relatively low concentrations to a number of ecological receptors. A toxicity assessment was carried out on soils from an explosive-contaminated site at a Canadian Forces Area Training Center. Toxicity studies on soil organisms using endpoints such as microbial processes (potential nitrification activity, dehydrogenase activity, substrate-induced respiration, basal respiration), plant seedling and growth (Lactuca sativa and Hordeum vulgare), and earthworm (Eisenia andrei) growth and reproduction were carried out. Results showed that 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) was the principal polynitroorganic compound measured in soils. Soils from the contaminated site decreased microbial processes and earthworm reproduction; whereas plant growth was not significantly reduced. Toxicity to aquatic organisms and genotoxicity were also assessed on soil elutriates using Microtox (Vibrio fischeri), growth inhibition of algae (Selenastrum capricornutum), and SOS Chromotest (Escherichia coli). Results indicated that soil elutriates were generally not toxic to bacteria (Microtox) and algae. However, genotoxicity was found in a number of soil elutriate samples. Thus, the explosive-contaminated soils from the antitank firing range may represent a hazard for the soil organisms. Nevertheless, the global toxicity might have partially resulted from HMX as well as from other (not identified) contaminants such as heavy metals. Crown Copyright Copyright 2003 Published by Elsevier Inc. All rights reserved.NRC publication: Ye

Caucasus sensitivity analysis MCC tree

Maximum clade credibility (MCC) tree from country of origin phylogeographic Caucasus sensitivity analysis. The Caucasus mountain countries Armenia, Azerbaijan, and Georgia are combined into a single geographic location