A four carbon organonitrate as a significant product of secondary isoprene chemistry

Oxidation of isoprene by nitrate radicals (NO3) or by hydroxyl radicals (OH) under high NOx conditions forms a substantial amount of organonitrates (ONs). ONs impact NOx concentrations and consequently ozone formation while also contributing to secondary organic aerosol. Here we show that the ONs with the chemical formula C4H7NO5 are a significant fraction of isoprene-derived ONs, based on chamber experiments and ambient measurements from different sites around the globe. From chamber experiments we found that C4H7NO5 isomers contribute 5-17% of all ONs formed during nighttime and constitute more than 40% of the ONs after further daytime oxidation. In ambient measurements C4H7NO5 isomers usually dominate both nighttime and daytime, implying a long residence time compared to C5 ONs which are removed more rapidly. We propose potential nighttime sources and secondary formation pathways, and test them using a box model with an updated isoprene oxidation scheme. This dataset is based on oxidation experiments of isoprene + NO3 radicals at the atmospheric chamber SAPHIR, in Jülich, Germany and ambient data from five different locations. More specifically, this dataset is provided in order for users to be able to replicate the results from the Tsiligiannis et al. publication. It includes time-series of gaseous species. The files called I-CIMS contain compounds that measured using a chemical ionization mass spectrometer (CIMS) with iodide as the reagent ion. The files called Br-CIMS contain compounds that measured using a chemical ionization mass spectrometer (CIMS) with bromide as the reagent ion. The files called TD-CRDS contain the total alkyl nitrates measured using a thermal dissociation−cavity ring-down spectrometer. The chamber data are indicated by the date of the experiment (e.g. 9Aug). The ambient data are indicated by the location where they collected (e.g. Amazon). All the date & time data corresponds to local time. For each column, the naming e.g. "BrC4H7NO5_ncps" or "C4H7INO5_ppt", corresponds to the chemical formula of the compound (C4H7NO5) clustering with either bromide or iodide, and the measurement units (ncps=normalized counts per second) or (ppt=parts per trillion by volume). File delimiter is the tabstop. The data from the SOAS campaign can be found here: https://csl.noaa.gov/groups/csl7/measurements/2013senex/Ground/DataDownload/index.php?page=/groups/csl7/measurements/2013senex/Ground/DataDownload/在高氮氧化物（NOₓ）条件下，异戊二烯被硝酸根自由基（NO₃）或羟基自由基（OH）氧化，可生成大量有机硝酸酯（organonitrates, ONs）。有机硝酸酯会影响氮氧化物浓度，进而调控臭氧生成，同时还会参与二次有机气溶胶的形成。本研究基于全球不同站点的烟雾箱实验与环境观测数据，证实化学式为C₄H₇NO₅的有机硝酸酯是异戊二烯来源有机硝酸酯的重要组分。烟雾箱实验结果显示，C₄H₇NO₅异构体在夜间生成的全部有机硝酸酯中占比为5%~17%，在经过进一步日间氧化后的有机硝酸酯中占比超过40%。环境观测数据表明，C₄H₇NO₅异构体在日间与夜间均通常占据主导地位，这意味着相较于被更快去除的C₅有机硝酸酯，该类物质拥有更长的大气停留时间。我们提出了潜在的夜间来源与二次生成路径，并利用搭载更新后异戊二烯氧化机制的箱式模型（box model）对其进行了验证。 本数据集基于德国于利希市SAPHIR大气烟雾箱开展的异戊二烯+硝酸根自由基氧化实验，以及来自五个不同地点的环境观测数据构建。本数据集旨在帮助用户复现Tsiligiannis等人（Tsiligiannis et al.）发表论文中的研究结果，数据集包含气态物种的时间序列数据。 命名为I-CIMS的文件包含以碘离子作为试剂离子的化学电离质谱（chemical ionization mass spectrometer, CIMS）检测到的化合物；命名为Br-CIMS的文件包含以溴离子作为试剂离子的化学电离质谱检测到的化合物；命名为TD-CRDS的文件包含通过热解离-腔环降光谱仪（thermal dissociation−cavity ring-down spectrometer）测得的总烷基硝酸酯含量。 烟雾箱实验数据以实验日期标注（例如9Aug），环境观测数据以采样地点标注（例如Amazon）。 所有日期与时间数据均采用当地时间。对于每一列数据，其命名格式例如"BrC4H7NO5_ncps"或"C4H7INO5_ppt"，分别对应与溴离子或碘离子团簇的目标化合物化学式（C₄H₇NO₅），以及测量单位：ncps为每秒归一化计数（normalized counts per second），ppt为体积万亿分之一（parts per trillion by volume）。数据文件以制表符作为分隔符。 SOAS观测计划的相关数据可通过以下链接获取：https://csl.noaa.gov/groups/csl7/measurements/2013senex/Ground/DataDownload/index.php?page=/groups/csl7/measurements/2013senex/Ground/DataDownload/