U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, Robert S. Kerr Environmental Research Center, 919 Kerr Lab Dr., Ada, OK, 74820, USA.
National Research Council, R.S. Kerr Environmental Research Center, 919 Kerr Lab Dr., Ada, OK 74821, USA.
Sci Total Environ. 2018 Dec 10;644:567-575. doi: 10.1016/j.scitotenv.2018.06.397. Epub 2018 Jul 11.
Hydroxylamine (NHOH) undergoes biotic and abiotic transformation processes in soil, producing nitrous oxide gas (NO(g)). Little is known about the magnitude of the abiotic chemical processes in the global N cycle, and the role of abiotic nitrification is still neglected in most current nitrogen trace gas studies. The abiotic fate of NHOH in soil systems is often focused on transition metals including manganese (Mn) and iron (Fe), and empirical correlations of nitrogen residual species including nitrite (NO), nitrate (NO), and NO(g). In this study, abiotic NHOH nitrification by well-characterized manganese (Mn)- and iron (Fe)-bearing minerals (pyrolusite, amorphous MnO(s), goethite, amorphous FeOOH(s)) was investigated. A nitrogen mass balance analysis involving NHOH, and the abiotic nitrification residuals, NO(g), NO(aq), NO, NO, was used, and specific reactions and mechanisms were investigated. Rapid and complete NHOH nitrification occurred (4-5 h) in the presence of pyrolusite and amorphous MnO(s), achieving a 95-96% mass balance of N byproducts. Conversely, NHOH nitrification was considerably slower by amorphous FeOOH(s) (14.5%) and goethite (1.1%). Direct reactions between the Mn- and Fe-bearing mineral species and NO and NO were not detected. Brunauer-Emmett-Teller surface area and energy dispersive X-ray measurements for elemental composition were used to determine the specific concentrations of Mn and Fe. Despite similar specific concentrations of Mn and Fe in crystalline and amorphous minerals, the rate of NHOH nitrification was much greater in the Mn-bearing minerals. Results underscore the intrinsically faster NHOH nitrification by Mn minerals than Fe minerals.
羟胺（NHOH）在土壤中经历生物和非生物转化过程，产生一氧化二氮气体（NO(g)）。人们对全球氮循环中非生物化学过程的规模知之甚少，而且大多数当前的氮痕量气体研究仍然忽视了非生物硝化作用的作用。土壤系统中 NHOH 的非生物命运通常集中在过渡金属上，包括锰（Mn）和铁（Fe），以及包括亚硝酸盐（NO）、硝酸盐（NO）和 NO(g)在内的氮残留物种的经验相关性。在这项研究中，研究了经过良好表征的含锰（Mn）和铁（Fe）矿物（软锰矿、无定形 MnO(s)、针铁矿、无定形 FeOOH(s)）对 NHOH 的非生物硝化作用。涉及 NHOH 和非生物硝化残留物、NO(g)、NO(aq)、NO、NO 的氮质量平衡分析被用于研究特定的反应和机制。在软锰矿和无定形 MnO(s)的存在下，NHOH 发生快速且完全的硝化作用（4-5 h），通过副产物实现 95-96%的氮质量平衡。相比之下，无定形 FeOOH(s)（14.5%）和针铁矿（1.1%）的 NHOH 硝化作用要慢得多。未检测到 Mn 和 Fe 矿物物种与 NO 和 NO 之间的直接反应。使用比表面积和能量色散 X 射线测量元素组成的 Brunauer-Emmett-Teller 测量来确定 Mn 和 Fe 的特定浓度。尽管结晶和无定形矿物中 Mn 和 Fe 的特定浓度相似，但 NHOH 的硝化作用在含 Mn 矿物中要快得多。结果强调了 Mn 矿物比 Fe 矿物更快的内在 NHOH 硝化作用。
