Rural Environment Protection Engineering & Technology Center of Sichuan Province, College of Environment, Sichuan Agricultural University, Chengdu 611130, China.
Rural Environment Protection Engineering & Technology Center of Sichuan Province, College of Environment, Sichuan Agricultural University, Chengdu 611130, China.
Sci Total Environ. 2019 Aug 15;678:780-792. doi: 10.1016/j.scitotenv.2019.04.432. Epub 2019 Apr 30.
Isoprene is the most abundant non-methane hydrocarbons (NMHCs) in the troposphere and is released predominantly by vegetation. The δC values of atmospheric isoprene vary with different plant types (e.g. C and C plants). In this work, aerosol samples were collected in four forest areas in Sichuan Province, China, i.e., the Baima Spring Scenic Area (BM), the Panzhihua Cycas Nature Reserve (PZ), the Gongga Mountain National Nature Reserve (GG) and the Wolong National Nature Reserve (WL) during the summers of 2010-2012. The stable carbon isotopic compositions of 2-methyltetrols, the stable products of isoprene oxidation by OH, were measured using a GC/C/IRMS (gas chromatography/combustion/isotopic ratio mass spectrometry) with methylboronic acid derivatization. The stable carbon isotopic fractionation coefficient of isoprene oxidized by OH (ε) was derived in laboratory. With the δC values of 2-methyltetrols, ε and meteorological parameters, the δC values of atmospheric isoprene were calculated. The results show that forests can remarkably change the δC values of isoprene in the regional scales, making significant contributions to isoprene emissions. Moreover, C/C proportions of shrubs and grasses depend on altitudes. The average δC values of atmospheric isoprene are -24.18 ± 1.72‰, -25.81 ± 1.36‰, -24.96 ± 0.94‰, -25.89 ± 1.35‰ for BM, PZ, GG and WL, respectively. The average δC value of atmospheric isoprene in SW China and the surrounding areas was -25.23 ± 1.44‰. C plants emitted 26.9 ± 10.3% of isoprene in the research atmosphere.
异戊二烯是对流层中含量最丰富的非甲烷碳氢化合物（NMHCs），主要由植被释放。大气中异戊二烯的 δC 值随不同植物类型（如 C 和 C 植物）而变化。在这项工作中，于 2010-2012 年夏季，在四川省的四个森林地区（白马泉风景区（BM）、攀枝花苏铁自然保护区（PZ）、贡嘎山国家级自然保护区（GG）和卧龙国家级自然保护区（WL））采集了气溶胶样本。采用 GC/C/IRMS（气相色谱/燃烧/同位素比质谱）和甲基硼酸衍生化，测量了羟基氧化异戊二烯的稳定碳同位素组成，即 2-甲基四醇，其是异戊二烯氧化的稳定产物。在实验室中推导出羟基氧化的异戊二烯稳定碳同位素分馏系数（ε）。利用 2-甲基四醇的 δC 值、ε 和气象参数，计算出大气中异戊二烯的 δC 值。结果表明，森林可以显著改变区域尺度上异戊二烯的 δC 值，对异戊二烯排放有重要贡献。此外，灌木和草本植物的 C/C 比例取决于海拔。大气中异戊二烯的平均 δC 值分别为 BM、PZ、GG 和 WL 的-24.18 ± 1.72‰、-25.81 ± 1.36‰、-24.96 ± 0.94‰、-25.89 ± 1.35‰。中国西南部及周边地区大气中异戊二烯的平均 δC 值为-25.23 ± 1.44‰。在研究的大气中，C 植物排放了 26.9 ± 10.3%的异戊二烯。
