We investigate the composition of 63 C2-C10 nonmethane hydrocarbons (NMHCs), methane (CH4) and carbon monoxide (CO), in Jeddah, Mecca, and Madina (Saudi Arabia), in Lahore, (Pakistan), and in Singapore. We established a database with which to compare and contrast NMHCs in regions where ambient levels and emissions are poorly characterized, but where conditions are favorable to the formation of tropospheric ozone, and where measurements are essential for improving emission inventories and modeling. This dataset will also serve as a base for further analysis of air pollution in Western Saudi Arabia including, but not limited to, the estimation of urban emissions and long range pollution transport from these regions. The measured species showed enhanced levels in all Saudi Arabian cities compared to the local background but were generally much lower than in Lahore. In Madina, vehicle exhaust was the dominant NMHC source, as indicated by enhanced levels of combustion products and by the good correlation between NMHCs and CO, while in Jeddah and Mecca a combination of sources needs to be considered. Very high NMHC levels were measured in Lahore, and elevated levels of CH4 in Lahore were attributed to natural gas. When we compared our results with 2010 emissions from the MACCity global inventory, we found discrepancies in the relative contribution of NMHCs between the measurements and the inventory. In all cities, alkenes (especially ethene and propene) dominated the hydroxyl radical (OH) reactivity (kOH) because of their great abundance and their relatively fast reaction rates with OH.

中文翻译：

---

沙特阿拉伯和巴基斯坦等新兴城市以及新加坡的一氧化碳、甲烷和非甲烷碳氢化合物的表征

我们调查了吉达、麦加和麦地那（沙特阿拉伯）、拉合尔（巴基斯坦）和新加坡的 63 种 C2-C10 非甲烷碳氢化合物 (NMHC)、甲烷 (CH4) 和一氧化碳 (CO) 的组成。我们建立了一个数据库，用于比较和对比环境水平和排放特征较差但条件有利于对流层臭氧形成的地区的 NMHC，在这些地区，测量对于改进排放清单和建模至关重要。该数据集还将作为进一步分析沙特阿拉伯西部空气污染的基础，包括但不限于这些地区的城市排放和远距离污染传输的估计。与当地背景相比，所有沙特阿拉伯城市的测量物种水平均有所提高，但通常远低于拉合尔。在麦地那，汽车尾气是主要的 NMHC 来源，这从燃烧产物水平的提高以及 NMHC 与 CO 之间的良好相关性可以看出，而在吉达和麦加，需要考虑多种来源的组合。在拉合尔测量到非常高的 NMHC 水平，拉合尔的 CH4 水平升高归因于天然气。当我们将我们的结果与 MACCity 全球清单的 2010 年排放量进行比较时，我们发现测量值和清单之间 NMHC 的相对贡献存在差异。在所有城市，