Screening of methyl chloride emitting plants in the sub-tropics and a study on the controlling factors of methyl chloride emission.

亚热带氯甲烷排放植物筛选及氯甲烷排放控制因素研究

• 批准号: 16340175
• 负责人: YOKOUCHI Yoko
• 金额: $ 6.14万
• 依托单位: National Institute for Environmental Studies
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16340175/
• 关键词: methyl chloride; subtropical plants; emission; Iriomote Island; tree fern; 放出量; 大気; 熱帯植物; 症物起源有機化合物; 放出機構

(1)Screening of methyl chloride emitting plantsIn order to find methyl chloride emitting plants, we put one or multiple leaves detached from a plant into a 40 ml-vial, and measured methyl chloride concentration in it after a few days. Two hundred and fourteen species of subtropical plants were collected in Iriomote Island. Thirty-two species among them were found to emit methyl chloride with average emission rate of 0.11〜0.51μg・(g dry wt)^<-1>・hr^<-1>.(2)Measurements of atmospheric methyl chloride in Iriomote IslandAir samples were collected at 5 sites in August and at 6 sites in February, and were analyzed for methyl chloride. Highest concentration, 2750 ppt, was observed at a forestal site. In the samples collected at coastal sites, 40〜50 ppt difference was found between the upwind sample and the downwind sample, suggesting accumulation of methyl chloride during the transport over the island covered by tropical forests. Based on the wind velocity and assumed mixing height, the emission rate of methyl chloride from the forest was calculated to be 5〜100μg・m^<-2>・h^<-1>, which would correspond to annual total emission of 10〜250 metric ton from the whole island.(3)Factors affecting methyl chloride emission from plantsFoliar emission rates of methyl chloride from tropical tree ferns were investigated using a bag enclosure method. Cyateha lepifera showed a midday decline in emission rates, whereas Cyathea podophyla showed a midday maximum. However, both of the ferns had a midday minimum in their methyl chloride emission in the experiment using a dynamic mass balance chamber. Increased ambient temperature enhanced methyl chloride emission from Cyathea podophylla, but suppressed the emission from Cyateha lepifera.

(1)甲基氯排放植物的筛选为了寻找甲基氯排放植物，我们把从植物上取下来的一片或多片叶子放入一个40毫升的瓶子里，几天后测量里面的氯甲烷浓度。在伊里奥莫特岛采集到亚热带植物214种。其中32种污染物的平均排放速率为0.11~0.5 1μg·(g干重)；-1；在森林地点观测到的最高浓度为2750ppt。在沿海采集的样品中，上风样品和下风样品之间存在40~50ppt的差异，这表明在热带森林覆盖的海岛上空输送过程中甲基氯的积累。根据风速和假定的混合高度，计算出森林中甲基氯的排放量为5~100μg·m~(-2)·h；~(-1)，相当于全岛年总排放量为10~250t；(3)影响植物甲基氯排放量的因素。蓝藻的排放速率在中午出现下降，而鬼臼苏铁的排放速率在中午出现最大值。然而，在使用动态质量平衡箱的实验中，这两种蕨类植物的甲基氯排放量在中午都达到了最低值。环境温度的升高增加了白背蓝藻的甲基氯排放，但抑制了蓝藻的甲基氯排放。