氨在大气酸沉降和气溶胶二次来源中扮演了重要角色。 城市大气NH3的测量对于研究NH3的大气化学显得尤为必要。 该文研究了差分吸收光谱技术应用于大气NH3测量时的影响因素； 根据NH3在短波紫外的吸收光谱特征, 确定了NH3浓度的反演波段和干扰扣除方法。 估算了应用于NH3测量的开放光路DOAS系统在228 m光程下的探测下限为0.27 μg·m-3, 并在广州市城区开展了大气NH3的外场测量, NH3表现出明显的日变化规律, 白天浓度较低, 夜间浓度高。 测量阶段中NH3最小值和最大值分别为0.83和3.11 μg·m-3, 平均浓度约为1.59 μg·m-3。 该系统的测量精度在10%以内, 对测量误差来源进行了分析。

As a key role in the acid-deposition and the generation of secondary particle matter (PM), measurement of the concentration of atmospheric ammonia in urban area has been attracting the scientists’ interests nowadays. After studying the special absorption features of ammonia in short UV wavelength range, detailed concernful issues were put forward in the present paper. The decision of using xenon lamp as the light source was made after the evaluation of measurement of light spectroscopy. Retrieval wavelength band for NH3 was fixed from 204 to 214 nm and optimal method of deducting other interferential gases was also shown. A home-made open-path DOAS (OP-DOAS) system was set up for the measurement of the concentration of atmospheric NH3. The detection limit of such system was calculated with the typical noise level as low as 0.33 μg·m-3 with the optical path 228 m. Through field experiment in Guangzhou city, such a system can be competent for the online and high time-resolution monitoring of the concentration of atmospheric ammonia. With a significant diurnal variation, the atmospheric ammonia changed from 0.83 to 3.11 μg·m-3 with the mean value 1.59 μg·m-3. The representative character of the diurnal variation is that the concentration of NH3 peaks during night while drops to bottom in the daytime. After the error analysis procedure, typical measurement accuracy of such OP-DOAS system was within 10%.