Diurnal and seasonal variations of iodocarbons (CH2ClI, CH2I2, CH3I, and C2H5I) in the marine atmosphere
Diurnal and seasonal variations of iodocarbons (CH2ClI, CH2I2, CH3I, and C2H5I) in the marine atmosphere
复制标题
DOI：
10.1029/2010jd015252
复制
发表时间：
2011-03
影响因子：
--
通讯作者：
Y. Yokouchi;Takuya Saito;A. Ooki;H. Mukai
中科院分区：
文献类型：
--
作者：
Y. Yokouchi;Takuya Saito;A. Ooki;H. Mukai
[1]用自动预浓缩气相色谱-质谱联用系统测定了八照间岛两个偏远海域的四种碘代烃，即氯碘甲烷（CH_2ClI）、二碘甲烷（CH_2I_2）、碘甲烷（CH_3I）和碘乙烷（C_2H_5I（24.05°N，123.8°E）和北海道东海岸的落石角（43.15°N，145.5°E）的17个月的数据，首次获得了所有这些化合物的全年高频数据集。CH 2ClI和CH 2 I2是高度光解的，在所有季节都表现出明显的日变化，白天浓度较低，而CH 3 I和C2 H5 I没有表现出明显的日变化。在大石角，所有的碘碳都表现出明显的季节性变化，夏季和秋季最高，这两个季节的特点是邻近海洋的藻类大量繁殖。在被亚热带贫营养沃茨包围的波照间岛，C2 H5 I和CH 2 I2的季节变化不显著，但夏季混合比较低。夜间混合比的CH 2ClI是强烈的，正相关的风速在整个观测期间在Hateruma岛，这表明无处不在的存在CH 2ClI源，可能是非生物的，在亚热带海洋。CH 3 I和C2 H5 I的混合比偶尔增加在Hateruma岛同时从亚洲大陆的冬季和春季污染事件，表明可能的大陆人为源或排放的海水离开大陆海岸。在Hateruma岛也观察到了CH 3 I基线混合比的上升，与较早的东风源区相比，当气团起源变得更偏南时，表明赤道地区的浓度更高。
[1] Four iodocarbons, chloroiodomethane (CH2ClI), diiodomethane (CH2I2), methyl iodide (CH3I), and ethyl iodide (C2H5I), were measured with an automated preconcentration gas chromatography–mass spectrometry system at two remote marine sites, Hateruma Island (24.05°N, 123.8°E) in the East China Sea and Cape Ochiishi (43.15°N, 145.5°E) on the eastern coast of Hokkaido, for 17 months, giving the first full-year high-frequency data sets for all these compounds. CH2ClI and CH2I2, which are highly photolyzed, showed remarkable diurnal variation in all seasons, with lower concentrations in the daytime, whereas CH3I and C2H5I showed no significant diurnal changes. At Cape Ochiishi, all of the iodocarbons showed clear seasonal variations and were highest in summer and autumn, which are characterized by algal blooms in the adjacent ocean. At Hateruma Island, which is surrounded by subtropical oligotrophic waters, the seasonal variations were not significant, but C2H5I and CH2I2 showed lower mixing ratios in summer. The nighttime mixing ratio of CH2ClI was strongly and positively correlated with wind speed throughout the observation period at Hateruma Island, suggesting the ubiquitous presence of CH2ClI sources, probably nonbiogenic, in the subtropical ocean. CH3I and C2H5I mixing ratios occasionally increased at Hateruma Island concurrently with winter and spring pollution events from the Asian continent, indicating possible continental anthropogenic sources or emissions from seawater off the continental coast. A rise in the CH3I baseline mixing ratio was also observed at Hateruma Island, when the air mass origin became more southerly, compared with the earlier, easterly source area, suggesting higher concentrations in equatorial regions.