Seasonal study of stable carbon and nitrogen isotopic composition in fine aerosols at a Central European rural background station
Seasonal study of stable carbon and nitrogen isotopic composition in fine aerosols at a Central European rural background station
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DOI：
10.5194/acp-19-3463-2019
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发表时间：
2018-09
影响因子：
6.3
通讯作者：
P. Vodička;K. Kawamura;J. Schwarz;B. Kunwar;V. Ždímal
中科院分区：
文献类型：
--
作者：
P. Vodička;K. Kawamura;J. Schwarz;B. Kunwar;V. Ždímal
抽象的。2013年9月27日至2014年8月9日，在Košetice（中欧）的一个农村背景站点（n=146），对细气溶胶颗粒（PM 1）的总碳（TC）的稳定碳同位素比（δ 13 C）和总氮（TN）的氮同位素比（δ 15 N）进行了研究，每2天进行一次，采样周期为24 h。结果表明，δ 13 C和δ 15 N均存在明显的季节变化。δ 15 N的季节变化表现为冬季低（13.1±4.5 ‰），夏季高（25.0±1.6 ‰）。秋季和春季是过渡时期，同位素组成逐渐变化，由于不断变化的来源和环境温度。δ 13 C的季节变化不太明显，但夏季（-27.8 ‰）比冬季（-26.7 ‰）亏损更严重。对水溶性离子、有机碳、元素碳、痕量气体和气象参数（主要是环境温度）的比较分析表明，同位素组成与这些物质有着重大的关联，这为相应的过程提供了更多的知识和了解。δ 15 N与NO3-、NH 4+和有机氮（OrgN）的比较表明，NO3-含量越高，TN的δ 15 N值越低，而NH 4+和OrgN的δ 15 N值越高。硝酸盐浓度最高，主要以NH 4 NO3为主，与生物质燃烧排放有关，导致冬季TN的δ 15 N平均值为13.3 ‰。春季PM 1中NO3-的比例下降。15 N的富集可能是由气相和气溶胶相之间的平衡交换（NH3（g）参与NH 4+（p））驱动的，这是由环境温度升高支持的。当NH 4 +/SO 42-的摩尔比达到2时，这种平衡在初夏被抑制，并且由于环境温度的升高，气溶胶中的硝酸盐分配可以忽略不计。夏季δ 15 N值最高，表明硫酸铵和有机氮气溶胶的老化。这种老化的气溶胶可以被有机物覆盖，其中13 C富集通过光氧化过程发生。这一结果得到了δ 13 C与环境温度和臭氧的正相关性的支持，如在夏季观察到的。在冬季，我们观察到一个事件的最低δ 15 N和最高δ 13 C值。冬季事件发生在盛行的东南气团中。虽然较高的δ 13 C值可能来自生物质燃烧颗粒物，但最低的δ 15 N值可能与低温条件下（< 0 ℃）农业排放的NH3有关。
Abstract. A study of the stable carbon isotope ratios (δ13C) of total carbon (TC) and the nitrogen isotope ratios (δ15N) of total nitrogen (TN) was carried out for fine aerosol particles (PM1) and was undertaken every 2 days with a 24 h sampling period at a rural background site in Košetice (Central Europe) from 27 September 2013 to 9 August 2014 (n=146). We found a seasonal pattern for both δ13C and δ15N. The seasonal variation in δ15N was characterized by lower values (average of 13.1±4.5 ‰) in winter and higher values (25.0±1.6 ‰) in summer. Autumn and spring were transition periods when the isotopic composition gradually changed due to the changing sources and ambient temperature. The seasonal variation in δ13C was less pronounced but more depleted in 13C in summer (-27.8±0.4 ‰) as compared to winter (-26.7±0.5 ‰). A comparative analysis with water-soluble ions, organic carbon, elemental carbon, trace gases and meteorological parameters (mainly ambient temperature) has shown major associations with the isotopic compositions, which has provided greater knowledge and understanding of the corresponding processes. A comparison of δ15N with NO3-, NH4+ and organic nitrogen (OrgN) revealed that although a higher content of NO3- was associated with a decrease in the δ15N of TN, NH4+ and OrgN caused increases. The highest concentrations of nitrate, mainly represented by NH4NO3 related to the emissions from biomass burning leading to an average δ15N of TN (13.3 ‰) in winter. During spring, the percentage of NO3- in PM1 decreased. An enrichment of 15N was probably driven by the equilibrium exchange between the gas and aerosol phases (NH3(g) ↔ NH4+(p)), which is supported by the increased ambient temperature. This equilibrium was suppressed in early summer when the molar ratios of NH4+/SO42- reached 2, and the nitrate partitioning in aerosol was negligible due to the increased ambient temperature. Summertime δ15N values were among the highest, suggesting the aging of ammonium sulfate and OrgN aerosols. Such aged aerosols can be coated by organics in which 13C enrichment takes place by the photooxidation process. This result was supported by a positive correlation of δ13C with ambient temperature and ozone, as observed in the summer season. During winter, we observed an event with the lowest δ15N and highest δ13C values. The winter event occurred in prevailing southeast air masses. Although the higher δ13C values probably originated from biomass-burning particles, the lowest δ15N values were probably associated with agriculture emissions of NH3 under low-temperature conditions (< 0 ∘C).