Dataset Information

Sequential anaerobic-aerobic biodegradation of emerging insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO).

ABSTRACT: Insensitive munitions, such as 3-nitro-1,2,4-triazol-5-one (NTO), are being considered by the U.S. Army as replacements for conventional explosives. Environmental emissions of NTO are expected to increase as its use becomes widespread; but only a few studies have considered the remediation of NTO-contaminated sites. In this study, sequential anaerobic-aerobic biodegradation of NTO was investigated in bioreactors using soil as inoculum. Batch bioassays confirmed microbial reduction of NTO under anaerobic conditions to 3-amino-1,2,4-triazol-5-one (ATO) using pyruvate as electron-donating cosubstrate. However, ATO biodegradation was only observed after the redox condition was switched to aerobic. This study also demonstrated that the high-rate removal of NTO in contaminated water can be attained in a continuous-flow aerated bioreactor. The reactor was first fed ATO as sole energy and nitrogen source prior to NTO addition. After few days, ATO was removed in a sustained fashion by 100%. When NTO was introduced together with electron-donor (pyruvate), NTO degradation increased progressively, reaching a removal efficiency of 93.5%. Mineralization of NTO was evidenced by the partial release of inorganic nitrogen species in the effluent, and lack of ATO accumulation. A plausible hypothesis for these findings is that NTO reduction occurred in anaerobic zones of the biofilm whereas ATO was mineralized in the bulk aerobic zones of the reactor.

SUBMITTER: Madeira CL

PROVIDER: S-EPMC5605804 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Sequential anaerobic-aerobic biodegradation of emerging insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO).

Madeira Camila L CL Speet Samuel A SA Nieto Cristina A CA Abrell Leif L Chorover Jon J Sierra-Alvarez Reyes R Field Jim A JA

Chemosphere 20161015

Insensitive munitions, such as 3-nitro-1,2,4-triazol-5-one (NTO), are being considered by the U.S. Army as replacements for conventional explosives. Environmental emissions of NTO are expected to increase as its use becomes widespread; but only a few studies have considered the remediation of NTO-contaminated sites. In this study, sequential anaerobic-aerobic biodegradation of NTO was investigated in bioreactors using soil as inoculum. Batch bioassays confirmed microbial reduction of NTO under a ...[more]

PMID: 27750172

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Project description:Abstract — Previous toxicological investigations of the insensitive munition (IM), 3-nitro-1,2,4-triazol-5-one (NTO), demonstrated histopathological and physiological impacts in mammalian testes. The implications of these findings for fish was unknown, therefore we investigated the effects of chronic (21 day) exposures to NTO and an NTO-containing IM formulation called IMX-101 (composed of 2,4-dinitroanisole (DNAN), nitroguanidine (NQ), and NTO) in adult male fathead minnows to assess if impacts on testes were conserved. The NTO exposure caused no significant mortality through the maximum exposure concentration (720 mg/L, measured), however NTO elicited testicular impacts causing significant asynchrony in spermatogenesis and necrosis in secondary spermatocytes at the two highest exposure concentrations (383 mg/L and 720 mg/L) and testicular degeneration at the highest exposure. Microarray-based transcriptomics analysis identified significant enrichment of steroid metabolism pathways and mTORC-signal control of spermatogonia differentiation in NTO exposures each having logical connections to observed asynchronous spermatogenesis. Additionally, NTO impaired transcriptional expression for genes supporting sperm structural and flagellar development including sperm-associated antigen 6 (Spag6). These functional transcriptomic responses are logical contributors underlying impacted reproductive physiology in NTO exposures that ultimately lead to reductions in spermatozoa. In contrast to NTO, the IMX-101 formulation elicited significant mortality at the two highest exposure concentrations of 25.2 and 50.9 mg/L (DNAN nominal + NTO measured + NQ measured). Unlike NTO and NQ, the DNAN component of the IMX-101 formulation underwent significant transformation in the 21d exposure. From previous investigations, neither NTO or NQ caused mortality in fish at >1000 mg/L suggesting that mortality in the present study arose from DNAN / DNAN-attributable transformation products. The 12.6 mg/L IMX-101 exposure caused significant sublethal impacts on testes including sperm necrosis, interstitial fibrosis, and Sertoli-like cell hyperplasia. Transcriptional profiles for IMX-101 indicated significant enrichment on multiple signaling pathways supporting spermatogenesis, mitosis / meiosis, and flagellar structure, all logically connected to observed sperm necrosis. Additionally, pronounced transcriptional increases within the PPARα-RXRα pathway, a known DNAN target, has been hypothesized to correspond to Sertoli cell hyperplasia, presumably as a compensatory response to fulfill the nurse-function of Sertoli cells during spermatogenesis. Overall, the transcriptional results indicated unique molecular responses for NTO and IMX-101. Regarding chemical hazard, NTO impacted testes and impaired spermatogenesis, but at high exposure concentrations (≥ 192 mg/L), whereas the IMX-101 formulation, elicited mortality and impacts on reproductive physiology likely caused by DNAN and its transformation products present at concentrations well below the NTO-component concentration within the IMX-101 mixture formulation. see previous row.

Project description:Halogenated organic solvents such as chlorobenzenes (CBs) are frequent groundwater contaminants due to legacy spills. When contaminated anaerobic groundwater discharges into surface water through wetlands and other transition zones, aeration can occur from various physical and biological processes at shallow depths, resulting in oxic-anoxic interfaces (OAIs). This study investigated the potential for 1,2,4-trichlorobenzene (1,2,4-TCB) biodegradation at OAIs. A novel upflow column system was developed to create stable anaerobic and aerobic zones, simulating a natural groundwater OAI. Two columns containing (1) sand and (2) a mixture of wetland sediment and sand were operated continuously for 295 days with varied doses of 0.14-1.4 mM sodium lactate (NaLac) as a model electron donor. Both column matrices supported anaerobic reductive dechlorination and aerobic degradation of 1,2,4-TCB spatially separated between anaerobic and aerobic zones. Reductive dechlorination produced a mixture of di- and monochlorobenzene daughter products, with estimated zero-order dechlorination rates up to 31.3 μM/h. Aerobic CB degradation, limited by available dissolved oxygen, occurred for 1,2,4-TCB and all dechlorinated daughter products. Initial reductive dechlorination did not enhance the overall observed extent or rate of subsequent aerobic CB degradation. Increasing NaLac dose increased the extent of reductive dechlorination, but suppressed aerobic CB degradation at 1.4 mM NaLac due to increased oxygen demand. 16S-rRNA sequencing of biofilm microbial communities revealed strong stratification of functional anaerobic and aerobic organisms between redox zones including the sole putative reductive dechlorinator detected in the columns, Dehalobacter. The sediment mixture column supported enhanced reductive dechlorination compared to the sand column at all tested NaLac doses and growth of Dehalobacter populations up to 4.1 × 108 copies/g (51% relative abundance), highlighting the potential benefit of sediments in reductive dechlorination processes. Results from these model systems suggest both substantial anaerobic and aerobic CB degradation can co-occur along the OAI at contaminated sites where bioavailable electron donors and oxygen are both present.

Dataset Information

Sequential anaerobic-aerobic biodegradation of emerging insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO).

Publications

Sequential anaerobic-aerobic biodegradation of emerging insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO).

Similar Datasets

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