山地城市大气NOx传输对周边植被茂密区域大气臭氧的影响研究

Nitrogen oxides(NOx) and volatile organic compounds(VOCs) are the key materials of atmospheric photochemical smoke pollution. The contact regions between mountainous cities and dense plants areas exist a large of anthropogenic emission of NOx and biogenic VOCs emissions, which implies there is a strong potential for ozone formation. High ozone level is a potential threat for the neighboring and the region crowd, crops and ecological system, but there is no system study.The atmospheric environment in the suburban contact is the research object of this proposal, and the transmission ways of anthropogenic emission of NOx in mountainous cities and the impact on ozone formation in the suburban contact are planned to do detailed researches. The research contents include: (1)To study air and atmospheric pollutants transmission paths in the ecological mountain city by wind tunnel simulation, and calculate the NOx transmission flux;(2) Analyse characteristics of volatile organic compounds emissions in alpine vegetation cover areas surrounding the cities. (3) Through the observation the concentrations of atmospheric nitrogen oxides, volatile organic compounds and ozone on the contact region, analysis the contribution of anthropogenic NOx emission and transmission for ozone formation .The purpose of the proposal is to know the spatial and temportal variations of anthropogenic NOx emission and transmission and their contribution on ozone formation in the contact region. This study can provide some scientific basis for reasonable control ozone pollution.

氮氧化物（NOx）和挥发性有机物（VOCs）是大气光化学烟雾污染形成的首要物质。四面环山的高原生态山地城市周边既存在大量人为排放的NOx又存在植物排放的挥发性有机物，具有较强的臭氧生成潜势，对城市周边人群、农作物及生态植被都构成严重威胁，但目前尚无系统研究。本项目以城郊接触带植被茂密区域大气环境为研究对象，针对城市人为源NOx传输途径及周边高地植被茂密区域臭氧生成贡献进行研究。研究内容包括：（1）通过风洞模拟及扩散模型分析山地城市NOx传输扩散分布特征；（2）研究生态山地城市周边植被茂密区域挥发性有机物排放特征。（3）通过观测城市与生态山地接触带大气环境中NOx、挥发性有机物和臭氧浓度，分析城市人为源NOx排放传输对区域臭氧生成的贡献。本项目旨在认识具有复杂下垫面的高原生态山地城市大气NOx传输机制及对周边植被茂密区域大气臭氧的影响，为合理控制臭氧污染提供科学依据。

近年来，城市大气臭氧污染及其生产机制受到广泛关注。本研究基于大气氮氧化物和挥发性有机化合物在太阳辐射条件下生成臭氧这一反应原理，开展城郊大气臭氧生成研究。基于臭氧敏感性分析方法，于2017-2018年在昆明城区和城郊选取3个观测点监测大气O3、NOx、VOCs和气象条件，研究了O3、NOx、VOCs的浓度分布特征及受气象条件的影响，并结合风洞及数值模拟方法分析城区中NOx在主导风向下传输，在周边区域形成的浓度分布特征。研究结果表明，主导风向上风向的人类活动与植被茂密区域接触带的NOx浓度远低于下风向接触带。AREMOD模拟显示城区大气污染物易在下风向区域因地形阻滞出现累积。城区VOCs浓度较高，甲苯、1,3,5-三甲基苯、对,间二甲苯等人为源标识物对臭氧生成潜势较大；城郊人类活动-生态系统接触带中，主要体现在自然源标识物异戊二烯浓度较高，其对臭氧的生成贡献最大，且人为源标识物甲苯和丙烷亦有较大贡献。臭氧敏感性分析显示，该区域NOx是O3生成最敏感的前体物，作为下风向处的接触带，其NOx浓度高显然是受上风向市区的人为排放NOx传输的影响。