Photo-transformation of aqueous nitroguanidine and 3-nitro-1,2,4-triazol-5-one: Emerging munitions compounds
| Autor: | Katerina Dontsova, Susan Taylor, Julie B. Becher, Dean E. Wilcox, Samuel A. Beal |
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| Rok vydání: | 2019 |
| Předmět: |
Environmental Engineering
Health Toxicology and Mutagenesis 0208 environmental biotechnology 02 engineering and technology 010501 environmental sciences 01 natural sciences Guanidines chemistry.chemical_compound Environmental Chemistry Ammonium Nitrite Insensitive munition 0105 earth and related environmental sciences Aqueous solution Photolysis Public Health Environmental and Occupational Health General Medicine General Chemistry Triazoles Nitro Compounds Pollution 020801 environmental engineering Nitroguanidine chemistry Nitro Urea Cyanamide Nuclear chemistry Environmental Monitoring |
| Zdroj: | Chemosphere. 228 |
| ISSN: | 1879-1298 |
| Popis: | Two major components of insensitive munition formulations, nitroguanidine (NQ) and 3-nitro-1,2,4-triazol-5-one (NTO), are highly water soluble and therefore likely to photo-transform while in solution in the environment. The ecotoxicities of NQ and NTO solutions are known to increase with UV exposure, but a detailed accounting of aqueous degradation rates, products, and pathways under different exposure wavelengths is currently lacking. Here, we irradiated aqueous solutions of NQ and NTO over a 32-h period at three ultraviolet wavelengths (254 nm, 300 nm, and 350 nm) and analyzed their degradation rates and transformation products. NQ was completely degraded by 30 min at 254 nm and by 4 h at 300 nm, but it was only 10% degraded after 32 h at 350 nm. Mass recoveries of NQ and its transformation products were ≥80% for all three wavelengths, and consisted of large amounts of guanidine, nitrate, and nitrite, and smaller amounts of cyanamide, cyanoguanidine, urea, and ammonium. NTO degradation was greatest at 300 nm with 3% remaining after 32 h, followed by 254 nm (7% remaining) and 350 nm (20% remaining). Mass recoveries of NTO and its transformation products were high for the first 8 h but decreased to 22–48% by 32 h, with the major aqueous products identified as ammonium, nitrate, nitrite, and a urazole intermediate. Environmental half-lives of NQ and NTO in pure water were estimated as 4 and 6 days, respectively. We propose photo-degradation pathways for NQ and NTO supported by observed and quantified degradation products and changes in solution pH. |
| Databáze: | OpenAIRE |
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