Sources of Nitrous Acid in the Atmospheric Boundary Layer

大气边界层中亚硝酸的来源

• 批准号: NE/M010554/1
• 负责人: Stephen Ball
• 金额: $ 18.77万
• 依托单位: University of Leicester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2015
• 资助国家: 英国
• 起止时间: 2015 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FM010554%2F1
• 关键词: Sources; Nitrous; Acid; Atmospheric; Boundary; Sources; Nitrous; Acid; Atmospheric; Boundary

Atmospheric chemical processing drives the removal of emitted pollutants, and leads to the formation of ozone and secondary aerosol, which are harmful to human and environmental health, and contribute to climate forcing. Reaction with the OH radical is the primary driver of these oxidation processes; OH abundance must be quantitatively understood in order to accurately predict such effects. In the free troposphere, ozone photolysis is the principal net OH source (neglecting NO-driven HOx cycling); however in the boundary layer a large body of evidence shows that nitrous acid (HONO) is an important, and sometimes the dominant, net OH precursor.Well-understood gas-phase HONO chemistry is not able to explain observed levels of HONO in the boundary layer: large additional sources, forming up to an order of magnitude more HONO, are required - however their identity remains elusive. Recent laboratory work (Su et al., Science 2011; Oswald et al., Science 2013) has identified soils as a globally significant source of HONO - driven, in part, by microbial action (analogous to the well known NO, N2O production), alongside surface NO2-to-HONO conversion mechanisms - but this microbial source has not been explored in the real environment. In urban areas, there is also increasing evidence, from field and chamber studies, that vehicles dominate HONO production - yet no data on HONO production from the UK vehicle fleet exist. Past studies have attempted to constrain HONO production through steady-state approaches, applied to co-located point measurements of OH, NO and HONO. Such analyses are however potentially hampered by the very different atmospheric lifetimes of these species, which dictates that they may not be in equilibrium in complex (spatially heterogeneous) environments. There is an urgent need for robust quantification of HONO sources, in order to quantitatively predict boundary layer HONO and OH abundance, and atmospheric chemical processing affecting air quality.Within SNAABL, we will directly measure HONO production from (1) natural ground surfaces (including soil production), and (2) road traffic emissions. Our approach will focus upon real-world environmental behaviour, and will avoid the uncertainties associated with analyses of ambient HONO concentrations. (1) Natural Ground Surfaces. We will measure surface HONO fluxes from contrasting agricultural and unmanaged environments, and relate these to NOx and N2O fluxes and physical, chemical atmospheric and soil parameters. Fertiliser manipulation experiments will assess the impact of nutrient addition at a unique field location permitting simultaneous measurement of perturbed- and control systems. We will also perform laboratory studies of natural surface HONO production, using soil cores from our field sites and other UK locations. Through manipulation and selective sterilisation, we will isolate and characterise the potential abiotic and microbial HONO production mechanism(s), including surface processes. (2) Traffic Emissions. We will directly determine HONO production from traffic, through measurement of HONO, NOx and CO2 in a road tunnel, an approach which provides a single, well characterised (video monitoring) source term, and removes the confounding factors of multiple sources, dispersion and photochemistry found in the ambient atmosphere. This approach will reflect the real-world fleet emissions, rather than potentially artificial results from dynamometer driving cycles. We will use our data to parameterise the resulting HONO source terms, and assess their accuracy, and implications for boundary layer air quality, using photochemical box and regional chemistry-transport modelling. SNAABL will deliver quantitative understanding of HONO production from natural surfaces and vehicle traffic, and so substantially improve the accuracy of predictions of boundary layer atmospheric chemical processing.

大气化学加工驱动去除发射污染物，并导致形成对人类和环境健康有害的臭氧和二次气溶胶，并导致气候强迫。与OH自由基的反应是这些氧化过程的主要驱动力。必须对OH丰度进行定量理解，以便准确预测这种影响。在自由对流层中，臭氧光解是主要的净OH来源（忽略了无驱动的HOX循环）。然而，在边界层中，大量证据表明，一亚硝酸（Hono）是一个重要的，有时是主要的，净OH前体。理解的气相HONO化学无法解释边界层中观察到的Hono水平：大型其他来源，形成大量的数量级，但需要更大的hono，但它们的身份仍然是相当的。最近的实验室工作（Su等，Science 2011; Oswald等人，Science 2013）已将土壤确定为全球重要的Hono驱动的来源，部分原因是微生物的作用（类似于已知的NO，N2O生产，N2O生产），以及Surface No2 -to -to -to -hono转换机制，但是这种微生物的来源尚未在现实​​环境中探索。在城市地区，从现场和商会研究中，有越来越多的证据表明，车辆主导了Hono的生产 - 但英国车队的HONO生产没有数据。过去的研究试图通过稳态方法来限制HONO生产，并应用于OH，NO和HONO的共同确定点测量。然而，这些分析可能会受到这些物种的大气寿命截然不同的阻碍，这表明它们可能在复杂（空间异质性）环境中不处于平衡状态。迫切需要对HONO来源进行强有力的量化，以定量预测边界层HONO和OH丰度，以及影响空气质量的大气化学加工。我们将直接从（1）自然地面表面（包括土壤产量）和（2）道路交通发电中直接测量HONO生产。我们的方法将集中在现实世界的环境行为上，并避免与环境HONO浓度分析相关的不确定性。 （1）自然地面表面。我们将从对比的农业和非托管环境中测量表面霍诺通量，并将其与NOX和N2O通量以及物理，化学大气和土壤参数相关联。肥料操纵实验将评估添加营养物质在独特的现场位置的影响，允许同时测量扰动和控制系统。我们还将使用来自我们的现场和其他英国地点的土壤核心进行自然表面HONO生产的实验室研究。通过操纵和选择性灭菌，我们将分离并表征潜在的非生物和微生物HONO生产机制，包括表面过程。 （2）交通排放。我们将直接通过在道路隧道中的HONO，NOX和CO2进行测量，从交通中直接确定HONO生产，该方法提供了一种具有良好特征的（视频监视）源术语，并消除了在环境气氛中发现的多种来源，分散和光化学的混杂因素。这种方法将反映现实世界中的车队排放，而不是因测功机驱动周期而产生的人为的结果。我们将使用我们的数据来参数最终的HONO源术语，并使用光化学框和区域化学框和区域化学转移建模来评估其准确性以及对边界层空气质量的影响。 Snaabl将对自然表面和车辆交通的HONO生产提供定量理解，从而实质上提高了边界层大气化学加工预测的准确性。