UNS: Oligomers Derived from Emerging Nitroaromatic Pollutants in Anaerobic Environments: Mechanisms, Fate and Toxicity

UNS：厌氧环境中新兴硝基芳香族污染物衍生的低聚物：机制、归宿和毒性

• 批准号: 1510698
• 负责人: Jim Field
• 金额: $ 33万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1510698&HistoricalAwards=false
• 关键词: UNS; Oligomers; Derived; Emerging; Nitroaromatic

1510698FieldNumerous organic compounds that are used as explosives, pesticides, and pharmaceuticals involve the use of nitrogen substitute aromatic compounds. These compounds can enter into aquatic environments after use in agriculture and firing ranges or from industrial and household discharges. It is known that these compounds may form polymers in waters reactive in the presence of oxygen. The current paradigm is that the polymerization of these compounds only occurs under conditions with oxygen dissolved in the aqueous waters. However, preliminary evidence has shown coupling reactions can also occur in the absence of oxygen which may have important implications to their toxicity in ground waters and other waters with low oxygen concentrations. The main focus of this project is to provide a mechanistic basis for the anaerobic coupling reactions between reactive intermediates derived from the microbial reduction of nitroaromatic pollutants. In anaerobic environments, the nitroaromatic compounds will undergo reductive (bio)transformation to aromatic amines via nitroso- and hydroxylamine-intermediates. The research will explore whether certain taxonomic groups of anaerobic microorganisms with nitroreductase genes become enriched as a consequence of the bioreduction of nitroaromatic compounds. Next the project will test three hypothesized mechanisms of coupling. The first two involve nucleophilic attacks on nitrosobenzene intermediates by either aromatic hydroxylamines or amines, forming azoxy (Ar-N+(O-)=N-Ar) or azo bonds (Ar-N=N-Ar), respectively. The third hypothesis is the coupling of radicals formed from the oxidation of aromatic amines by metals. The extent of the coupling reactions is expected to depend on the nitroaromatic structure. Coupling of compounds with just one nitro group may be limited to dimers; whereas, structures with multiple nitro groups can continue coupling to form large polymers. Extensive coupling reactions are also expected with a continuous supply of nitroaromatic pollutants which would allow for a continuous production of reactive intermediates. Isotopically labeled model compounds (15N, 13C and 14C) will be used to help elucidate the structure of humic-like substances formed in the absence of O2. Preliminary data indicate that dimers have an increased toxicity compared to the original nitroaromatic compounds justifying a detailed evaluation of their microbial and aquatic toxicity in this project. The project will have impacts on risk assessment, green synthesis, high school STEM education, inclusion of minorities in the scientific and educational enterprises, and the long term goals of the research group. Azo dyes lend themselves nicely to STEM projects because concentration is visually observable.

1510698领域许多用作炸药、杀虫剂和药物的有机化合物涉及使用氮取代芳族化合物。这些化合物在农业和射击场使用后或从工业和家庭排放物中进入水生环境。已知这些化合物可在氧气存在下在反应性沃茨形成聚合物。目前的范例是这些化合物的聚合仅在氧溶解在水性沃茨中的条件下发生。然而，初步证据表明，偶联反应也可能在无氧条件下发生，这可能对它们在地下沃茨和其他低氧浓度沃茨中的毒性产生重要影响。本项目的主要重点是为微生物还原硝基芳烃污染物的反应中间体之间的厌氧偶联反应提供机理基础。在厌氧环境中，硝基芳族化合物将通过亚硝基和羟胺中间体进行还原（生物）转化为芳族胺。这项研究将探讨是否某些分类组的厌氧微生物与硝基还原酶基因成为丰富的硝基芳香化合物的生物还原的结果。接下来，该项目将测试三种假设的耦合机制。前两种反应涉及芳族羟胺或芳族胺对亚硝基苯中间体的亲核攻击，分别形成偶氮氧（Ar-N+（O-）=N-Ar）或偶氮键（Ar-N=N-Ar）。第三种假设是由金属氧化芳香胺形成的自由基的偶联。预计偶联反应的程度取决于硝基芳族结构。仅具有一个硝基的化合物的偶联可能限于二聚体;而具有多个硝基的结构可以继续偶联以形成大的聚合物。广泛的偶联反应也预计与硝基芳香族污染物的连续供应，这将允许连续生产的活性中间体。同位素标记的模型化合物（15 N，13 C和14 C）将被用来帮助阐明在没有O2的情况下形成的腐殖类物质的结构。初步数据表明，与原始硝基芳香族化合物相比，二聚体具有更高的毒性，证明在本项目中对其微生物和水生物毒性进行详细评价是合理的。该项目将对风险评估、绿色合成、高中STEM教育、少数民族参与科学和教育企业以及研究小组的长期目标产生影响。偶氮染料很适合STEM项目，因为浓度是肉眼可见的。