上甸子本底站臭氧生成效率的观测研究

2008年3月26日～10月9日在北京上甸子大气本底站开展了O3、NOx、NOy、CO等气体的现场观测和VOCs采样观测.利用观测数据,首次取得该本底站臭氧生成效率(OPE),研究了OPE与NOx和VOCs的关系,探讨了HNO3干沉降对OPE的可能影响及订正方法.结果表明,观测期间逐日OPE值的变化范围为0.2～21.1,平均值为4.9±3.6;晴天的总体OPE值为4.3±1.5;OPE值随NOx浓度的变化基本符合抛物线关系,当NOx14×10-9时,OPE随NOx的增加而增加;当NOx14×10-9时,OPE随NOx的增加而减少;芳香烃和OVOCs与OPE存在密切的正相关关系.HNO3等NOx氧化产物的干沉降对计算的OPE有显著影响,导致计算结果偏高.利用北京市区和上甸子的NOy/CO值可以对观测期间的OPE值进行初步订正,但订正方法尚不够严谨,结果需要进一步验证.未订正的OPE计算值可认为是实际OPE的上限.

Observational Study of Ozone Production Efficiency at the Shangdianzi Regional Background Station

Ambient O₃, NO_x, NO_y, and CO were measured at the Shangdianzi regional background station from 26 March to 9 October 2008, and VOCs samples were taken and analyzed. This paper uses the data to obtain the ozone production efficiency (OPE) at Shangdianzi and studies the relationship of OPE with NO_x and VOCs. In addition, the potential impact from the dry deposition of NO_x oxidation products on the calculated OPE was estimated and tentatively corrected. Based on this study, the daily OPE varied in the range of 0.2-21.1, with an average of 4.9±3.6.An overall OPE average of 4.3±1.5 can be obtained. The dependence of OPE on the NO_x concentration can be described using an empirical parabolic function. If the concentration of NO_x is lower than 14×10^-9, OPE increases with NO_x; while if the concentration of NO_x is higher than 14×10^-9, OPE decreases with NO_x. The correlation analysis indicates that the concentrations of aromatics and OVOCs are positively correlated to OPE. Dry deposition of HNO₃ and other NO_x oxidation products may significantly impact the calculated OPE values, leading to overestimate. It is possible to correct such overestimate using the NO_y/CO ratios obtained at an urban site and at Shangdianzi. However, this correction is less rigorous and the corrected OPE data remain to be validated. The uncorrected data can be viewed as the upper limit of the real OPE.