Uncharacterised microbial pathways are key to understanding large fluxes of biogenic reactive nitrogen gases from agronomic soils

未知的微生物途径是了解农业土壤中大量生物活性氮气的关键

• 批准号: BB/X002187/1
• 负责人: Ryan Mushinski
• 金额: $ 71.18万
• 依托单位: University of Warwick
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FX002187%2F1
• 关键词: Uncharacterised; microbial; pathways; key; understanding

Atmospheric reactive nitrogen oxide gases (NOy = NO + NO2 + HONO + ...) are coupled to Earth's nitrogen cycle through an intricate network of interactions between anthropogenic activity (primarily combustion), soil nitrogen, and soil microbial activity. The biogeochemistry of soil nitrogen emissions is traditionally thought to be dominated by nitrogen gas (N2) and nitrous oxide (N2O); however, satellite, modelling, and laboratory studies show NOy emissions from soil can be of greater magnitude than these more commonly measured nitrogen gases. NOy are important in atmospheric chemistry as precursors to ozone (O3) and play a key role in the formation of acid rain. NOy are also considered secondary air pollutants - known to worsen asthma and bronchitis, especially in adolescent and geriatric populations. In addition to anthropogenic sources, NOy gases are produced from natural non-point sources including soil (24% of total NOy emissions), wildfires (19%), and lightning (13%). However, very little is known about NOy fluxes from these natural sources even though they account for 50% of all atmospheric NOy - with this percentage increasing as vehicle and industry emissions continue to decline. Importantly, there is a critical lack of information regarding biogenic (microbiologically derived) production mechanisms, resulting in inaccurate NOy-coupled climate model projections. This can be primarily attributed to a lack of understanding regarding the formation of major NOy species, such as nitrogen dioxide (NO2) and nitrous acid (HONO). We suspect there are yet undiscovered NOy-producing pathways, catalysed by a vast array of microbes from all three domains of life. Our hypothesised mechanisms are derived from human physiology, where NOy species are known to be important signalling molecules. We will explore these mechanisms in agronomic soils, as soils are the largest natural source of NOy gases, and within an agronomic context as our preliminary work has shown that these soils produce significantly more NOy than other terrestrial systems such as grasslands and woodlands. We will further define agronomic-NOy with field trials of a major UK commercial crop (Triticum), including four cultivars with differing above- and belowground traits. It will be crucial to define NOy soil emissions from these different cultivars, as varying plant traits, such as specific root length, can influence the soil N-cycle microbiome - which will inevitably influence NOy emissions. Other important variables will also be explored, including fertiliser application and spatial variability of NOy flux. Importantly, we will also attempt to determine the role of soil iron and iron speciation on N-cycle community composition and NOy fluxes. Soil iron is an important aspect of our theoretical NOy mechanism - stimulating the production of reactive oxygen species, which is a key reactant in the production of NOy. We will source soil with differing iron content from various farms throughout England to be used in wheat mesocosms studies. Soil NOy fluxes will be measured and connected to mineralogical characteristics and the N-cycle community size. Overall, this project will determine fundamental knowledge on the biogenic production mechanisms of major NOy species, provide direct soil NOy flux measurements from a major global crop, and lead to a better understanding of coupled carbon-nutrient-mineral cycling in soil. Furthermore, this work represents a major step change in the understanding of soil nitrogen dynamics, will be one of the first to couple shotgun metagenomics and culture-dependent methods to atmospheric chemistry processes, and will represent a major advancement in atmospheric accounting of NOy.

大气反应性氮氧化物气体（NOy = NO + NO2 + HONO + ...）通过人类活动（主要是燃烧）、土壤氮和土壤微生物活动之间复杂的相互作用网络与地球的氮循环耦合。传统上认为土壤氮排放的生物地球化学以氮气（N2）和一氧化二氮（N2O）为主；然而，卫星、模型和实验室研究表明，土壤中 NOy 的排放量可能比这些更常见的测量氮气的排放量更大。 NOy 在大气化学中非常重要，是臭氧 (O3) 的前体，并且在酸雨的形成中发挥着关键作用。 NOy 也被认为是二次空气污染物 - 已知会加重哮喘和支气管炎，尤其是在青少年和老年人群中。除人为来源外，NOy 气体还由自然非点源产生，包括土壤（占 NOy 总排放量的 24%）、野火（19%）和闪电（13%）。然而，尽管这些自然资源占所有大气 NOy 的 50%，但人们对这些自然资源的 NOy 通量知之甚少，并且随着车辆和工业排放量的持续下降，这一比例还在增加。重要的是，关于生物（微生物衍生）生产机制的信息严重缺乏，导致 NOy 耦合气候模型预测不准确。这主要归因于对主要 NOy 物种的形成缺乏了解，例如二氧化氮 (NO2) 和亚硝酸 (HONO)。我们怀疑尚有尚未发现的 NOy 产生途径，由来自所有三个生命领域的大量微生物催化。我们假设的机制源自人类生理学，其中 NOy 物种被认为是重要的信号分子。我们将在农艺土壤中探索这些机制，因为土壤是 NOy 气体的最大天然来源，并且在农艺背景下，因为我们的初步工作表明这些土壤比其他陆地系统（例如草地和林地）产生更多的 NOy。我们将通过对英国主要经济作物（小麦）的田间试验进一步定义农艺 NOy，其中包括具有不同地上和地下性状的四个品种。定义这些不同品种的 NOy 土壤排放量至关重要，因为不同的植物性状（例如特定的根长度）会影响土壤氮循环微生物群，从而不可避免地影响 NOy 排放量。还将探讨其他重要变量，包括肥料施用和 NOy 通量的空间变异性。重要的是，我们还将尝试确定土壤铁和铁形态对氮循环群落组成和 NOy 通量的作用。土壤铁是我们理论 NOy 机制的一个重要方面——刺激活性氧的产生，活性氧是 NOy 产生的关键反应物。我们将从英格兰各地的各个农场采购具有不同铁含量的土壤，用于小麦中生态系统研究。将测量土壤 NOy 通量并将其与矿物学特征和氮循环群落规模联系起来。总体而言，该项目将确定主要 NOy 物种的生物产生机制的基础知识，提供全球主要作物的直接土壤 NOy 通量测量，并更好地了解土壤中碳-养分-矿物质耦合循环。此外，这项工作代表了对土壤氮动态的理解的重大一步变化，将是第一个将鸟枪法宏基因组学和依赖于培养的方法与大气化学过程结合起来的工作之一，并将代表 NOy 大气核算的重大进步。