Non-Methane Hydrocarbon Emissions from Plants

自然来源的非甲烷碳氢化合物(NMHC)的排放早在二十多年前就已为人所知。主要来源被认为是植被。其他重要的自然来源是海洋藻类、土壤中的微生物活动、天然气渗漏、生物质燃烧。植物的天然碳氢化合物排放在对流层光化学氧化剂的产生中起着重要作用，但这些生物源化合物的区域和全球清单存在一些不确定性。许多不确定性的产生是因为缺乏将碳氢化合物排放与控制这种植物排放的关键环境变量联系起来的准确数据。此外，很大一部分生物成因碳氢化合物的化学鉴定存在不确定性，对植物碳氢化合物生产的生理或生物化学知之甚少。该项目将进行实验室研究，以a)准确测量控制植物中异戊二烯和相关NMHC生物发生的环境变量，b)提供排放的NMHC的新的化学鉴定，以及c)探索叶表面微生物作为NMHC汇或源的作用。在环境控制的气体交换室中的工厂排放的NMHC将通过气相色谱测量来表征，并通过气相色谱/质谱分析来识别碳氢化合物。通过使用代表主要植物群和生态系统的植物，NMHC的排放将与气温、光照强度、湿度和二氧化碳浓度有关，并将开发与这些参数相关的排放算法。将开发一个模型来解释植物如何以及为什么排放异戊二烯和相关的NMHC，并对此类排放的环境监管提出建议。

The emission of non-methane hydrocarbons (NMHC) from natural sources has been known for over two decades. The major source is thought to be vegetation. Other significant natural sources are marine algae, microbial activity in soils, natural gas seeps, the biomass burning. Natural hydrocarbon emissions from plants play an important role in the generation of photochemical oxidants in the troposphere, but there are a number of uncertainties in regional and global inventories of these biogenic compounds. Much of the uncertainty arises because there is a lack of precise data relating hydrocarbon emissions to key environmental variables that regulate such emissions from vegetation. In addition, there is uncertainty about the chemical identification of a large fraction of biogenic hydrocarbons, and very little is known of the physiology or biochemistry of plant hydrocarbon production. This project will conduct laboratory studies to a) measure accurately the environmental variables controlling the biogenesis of isoprene and related NMHC in plants, b) provide new, chemical identification of emitted NMHC, and c) explore the role of micro organisms on leaf surfaces as sinks or sources of NMHC. NMHC emissions form plants in environmentally controlled gas exchange chambers will be characterized by gas chromatography measurements, with identification of hydrocarbons by gas chromatography/mass spectrometry. By using plants representing major plant groups and ecosystems, NMHC emissions will be related to air temperature, light intensity, humidity, and carbon dioxide concentration, and algorithms relating emissions to these parameters will be developed. A model will be developed to explain how and why plants emit isoprene and related NMHC, and to suggest the environmental regulation of such emissions.