Metabolism and Photolysis of 2,4-Dinitroanisole in Arabidopsis.

New insensitive munitions explosives, including 2,4-dinitroanisole (DNAN), are replacing traditional explosive compounds to protect soldiers and simplify transport logistics. Despite the occupational safety benefits of these new explosives, feasible strategies for cleaning up DNAN from soil and water have not been developed. Here, we evaluate the metabolism of DNAN by the model plant Arabidopsis to determine whether phytoremediation can be used to clean up contaminated sites. Furthermore, we evaluate the role of photodegradation of DNAN and its plant metabolites within Arabidopsis leaves to determine the potential impact of photolysis on the phytoremediation of contaminants. When exposed to DNAN for three days, Arabidopsis took up and metabolized 67% of the DNAN in hydroponic solution. We used high resolution and tandem mass spectrometry in combination with stable-isotope labeled DNAN to confirm ten phase II DNAN metabolites in Arabidopsis. The plants separately reduced both the para- and ortho-nitro groups and produced glycosylated products that accumulated within plant tissues. Both DNAN and a glycosylated metabolite were subsequently photolyzed within leaf tissue under simulated sunlight, and [15N2]DNAN yielded 15NO2- in leaves. Therefore, photolysis inside leaves may be an important, yet under-explored, phytoremediation mechanism.

Biotransformation of 2,4-dinitroanisole by a fungal Penicillium sp.

Insensitive munitions explosives are new formulations that are less prone to unintended detonation compared to traditional explosives. While these formulations have safety benefits, the individual constituents, such as 2,4-dinitroanisole (DNAN), have an unknown ecosystem fate with potentially toxic impacts to flora and fauna exposed to DNAN and/or its metabolites. Fungi may be useful in remediation and have been shown to degrade traditional nitroaromatic explosives, such as 2,4,6-trinitrotoluene and 2,4-dinitrotoluene, that are structurally similar to DNAN. In this study, a fungal Penicillium sp., isolated from willow trees and designated strain KH1, was shown to degrade DNAN in solution within 14 days. Stable-isotope labeled DNAN and an untargeted metabolomics approach were used to discover 13 novel transformation products. Penicillium sp. KH1 produced DNAN metabolites resulting from ortho- and para-nitroreduction, demethylation, acetylation, hydroxylation, malonylation, and sulfation. Incubations with intermediate metabolites such as 2-amino-4-nitroanisole and 4-amino-2-nitroanisole as the primary substrates confirmed putative metabolite isomerism and pathways. No ring-cleavage products were observed, consistent with other reports that mineralization of DNAN is an uncommon metabolic outcome. The production of metabolites with unknown persistence and toxicity suggests further study will be needed to implement remediation with Penicillium sp. KH1. To our knowledge, this is the first report on the biotransformation of DNAN by a fungus.

Feature Engineering and Supervised Machine Learning to Forecast Biogas Production during Municipal Anaerobic Co-Digestion.

Municipalities with excess anaerobic digestion capacity accept offsite wastes for co-digestion to meet sustainability goals and create more biogas. Despite the benefits inherent to co-digestion, the temporal and compositional heterogeneity of external waste streams creates operational challenges that lead to upsets or conservative co-digestion. Given the complex microbial bioprocesses occurring during anaerobic digestion, prediction and modeling of the outcomes can be challenging, and machine learning has the potential to improve understanding and control of co-digestion processes. Biogas flows are a surrogate for process health, and here, we predicted biogas production from historical data collected by a water resource recovery facility (WRRF) during normal operation. We tested a daily lab and operational data set (n = 1089 after cleaning) and a minute-by-minute supervisory control and data acquisition (SCADA) operational data set (n = 491,761 after cleaning) to determine if forecasting biogas flow for a 24 h time horizon is feasible without collecting additional data. We found that a multilayer perceptron (MLP) neural network model outperformed tree-based and multiple linear regression models. Using a high-resolution SCADA data set for the first time, we showed that MLP neural networks could predict biogas production with an adjusted coefficient of determination (R2) of 0.78 and a mean absolute percentage error of 13.4% on a holdout test set. Adding daily laboratory analyses to the model did not appreciably improve the prediction of biogas flows. Feature engineering was essential to an accurate prediction, and 11 of the 15 most important features in the SCADA model were calculated from raw SCADA outputs. In summary, this paper demonstrates that minute-scale SCADA information collected at a municipal co-digestion facility can forecast biogas production, as a first step toward a digital twin model, without additional data collection.

Photolysis of 3-Nitro-1,2,4-triazol-5-one: Mechanisms and Products.

Insensitive munitions formulations that include 3-nitro-1,2,4-triazol-5-one (NTO) are replacing traditional explosive compounds. While these new formulations have superior safety characteristics, the compounds have greater environmental mobility, raising concern over potential contamination and cleanup of training and manufacturing facilities. Here, we examine the mechanisms and products of NTO photolysis in simulated sunlight to further inform NTO degradation in sunlit surface waters. We demonstrate that NTO produces singlet oxygen and that dissolved oxygen increases the NTO photolysis rate in deionized water. The rate of NTO photolysis is independent of concentration and decreases slightly in the presence of Suwannee River Natural Organic Matter. The apparent quantum yield of NTO generally decreases as pH increases, ranging from 2.0 × 10-5 at pH 12 to 1.3 × 10-3 at pH 2. Bimolecular reaction rate constants for NTO with singlet oxygen and hydroxyl radical were measured to be (1.95 ± 0.15) × 106 and (3.28 ± 0.23) × 1010 M-1 s-1, respectively. Major photolysis reaction products were ammonium, nitrite, and nitrate, with nitrite produced in nearly stoichiometric yield upon the reaction of NTO with singlet oxygen. Environmental half-lives are predicted to span from 1.1 to 5.7 days. Taken together, these data enhance our understanding of NTO photolysis under environmentally relevant conditions.