Measurement and interpretation of isoprene fluxes and isoprene, methacrolein, and methyl vinyl ketone mixing ratios at the PROPHET site during the 1998 Intensive
Measurement and interpretation of isoprene fluxes and isoprene, methacrolein, and methyl vinyl ketone mixing ratios at the PROPHET site during the 1998 Intensive
复制标题
DOI：
10.1029/2000jd000225
复制
发表时间：
2002-02-16
影响因子：
4.4
通讯作者：
Geron, CD
中科院分区：
文献类型：
--
作者：
Apel, EC;Riemer, DD;Geron, CD
[1]异戊二烯，甲基乙烯基酮（MVK），和甲基丙烯醛（MACR）的混合比连续测定在1998年夏天在一个农村森林位于密歇根大学生物站（UMBS）内的网站在8天的时间。这些测量结果是作为氧化剂研究计划的一部分获得的：光化学，排放和运输（PROPHET）研究。在附近的塔（AmeriFlux，位于PROPHET塔东北偏北132米处）同时测量异戊二烯的通量。在研究之后，使用森林密度估计值（生物源排放清单系统（BEIS 3）模型）得出了塔60公里半径范围内异戊二烯的1公里分辨率排放估计值。测量的异戊二烯通量在该网站相比，以及建模异戊二烯通量时，使用BEIS 3和详细的树叶凋落物数据集的树种从UMBS网站。异戊二烯、MACR和MVK的平均午间（1000-1400 LT）混合比分别为1.90 +/- 0.43、0.07 +/- 0.01和0.14 +/- 0.04 ppbv。这些化合物的中位午间混合比分别为1.96 +/- 0.26、0.06 +/- 0.02和0.10 +/- 0.02 ppbv。异戊二烯的氧化产物的异戊二烯的比例，了解这些化合物和一个简单的连续反应方案模型的背景下，以前的实验室和现场测量研究。模型的结果表明，研究的空气质量代表了相对新鲜的排放物，测量的异戊二烯的光化学年龄在3.6和18分钟之间，这明显小于异戊二烯的光化学寿命（在[OH] = 3.35 x 10（6）分子cm（-3）时τ = 45分钟）。因此，到达歧管的大部分异戊二烯没有时间与OH完全反应，产生低于基于未明确考虑这一点的模型计算的预期比率。日落后不久，异戊二烯混合比迅速下降，随后在整个晚上的休息时间缓慢衰减。排放图表明，异戊二烯通量是最高的塔附近相比，周围地区的网站。因此，从周围地区的垂直扩散和平流被假定为导致所观察到的初始快速减少异戊二烯在网站上。第二次异戊二烯衰变可能是由于化学和/或动力学，但这些影响不能与现有数据分开。
[1] Mixing ratios of isoprene, methyl vinyl ketone (MVK), and methacrolein (MACR) were determined continuously during an 8-day period in the summer of 1998 at a rural forested site located within the University of Michigan Biological Station (UMBS). The measurements were obtained as part of the Program for Research on Oxidants: Photochemistry, Emissions, and Transport (PROPHET) study. Fluxes of isoprene were concurrently measured at a nearby tower (AmeriFlux, located 132 m north-northeast of the PROPHET tower). Following the study, 1-km-resolution emission estimates were derived for isoprene within a 60-km radius of the tower using forest density estimates (Biogenic Emissions Inventory System (BEIS3) model). Measured isoprene fluxes at the site compared well with modeled isoprene fluxes when using BEIS3 and a detailed leaf litter-fall data set by tree species from the UMBS site. Mean midday (1000-1400 LT) mixing ratios for isoprene, MACR, and MVK were 1.90 +/- 0.43, 0.07 +/- 0.01, and 0.14 +/- 0.04 ppbv, respectively. Median midday mixing ratios of these compounds were 1.96 +/- 0.26, 0.06 +/- 0.02, and 0.10 +/- 0.02 ppbv, respectively. Ratios of the isoprene oxidation products to isoprene are understood in the context of previous laboratory and field measurement studies of these compounds and a simple consecutive reaction scheme model. Results of the model indicate that the air masses studied represented relatively fresh emissions with a photochemical age of measured isoprene between 3.6 and 18 min, which is significantly less than the photochemical ;lifetime of isoprene (tau = 45 min at [OH] = 3.35 x 10(6) molecules cm(-3)). Thus a large portion of the isoprene that reaches the manifold has not had time to react completely with OH, yielding lower than expected ratios based on model calculations that do not explicitly take this into account. A rapid decrease in isoprene mixing ratios was observed soon after sunset, followed by a slower decay throughout the rest of the night. Emission maps were generated indicating that isoprene fluxes are highest in the immediate vicinity of the tower compared to the surrounding area of the site. Thus vertical diffusion and advection from the surrounding region are postulated to cause the observed initial rapid decrease in isoprene at the site. The second isoprene decay may be due to chemistry and/or dynamics, but the effects cannot be separated with the available data.