上甸子区域大气本底站NO 2柱浓度光谱反演及其变化特征

Spectral Inversion and Characteristics of NO_2 Column Density at Shangdianzi Regional Atmospheric Background Station

为了探究京津冀本底浓度地区NO_2 这一重要空气污染物的变化特征,采用多轴差分吸收光谱技术(MAX-DOAS)在上甸子区域大气本底站开展了太阳散射光谱观测以及NO_2 柱浓度反演研究。在NO_2 的405～430nm特征谱段进行了定量光谱解析,并通过几何近似法计算了2009年7～9月NO_2 对流层垂直柱浓度(VCD_(trop))。观测期间NO_2 VCD_(trop)平均值和最大值分别为5.43×10^(15)和7.15×10^(16) molec·cm^(-2)。NO_2 VCD_(trop)日均值浓度水平较低,但总体上有上升趋势。NO_2 VCD_(trop)变化过程与风速风向关系密切:西南风时风速越小NO_2 VCD_(trop)越低,东北风对NO_2 VCD_(trop)有扩散稀释作用。NO_2 VCD_(trop)日变化形态总体上呈现为中午时段低、早晚较高的特征,并且傍晚峰值比早间峰值略高。上甸子站NO_2 VCD_(trop)浓度水平和日变化幅度相比北京城区同期观测结果明显偏小。NO_2 VCD_(trop)变化特征与河北香河和固城等污染相对较轻站点观测到的变化特征相一致。总之,MAX-DOAS能够有效监测区域本底大气的NO_2 VCD_(trop),其变化特征与工业和交通排放、大气光化学过程、大气传输等复杂因素有关,还需积累更多数据和深入研究。

In order to explore the variation characteristics of significant air pollutant N O 2 in the Beijing-Tianjin-Hebei background region,the Multi Axis Different ial Optical Absorption Spectroscopy(MAX-DOAS)was used to record solar scatter ing spectra at Shangdianzi regional atmospheric background station and retrieve the NO 2 column densities.Quantitative spectral analysis was carried out in t he characteristic wavelength of NO 2 405~430 nm.The NO 2 tropospheric verti cal column densities(VCD trop)from July 2009 to September 2009 were calc ulated through geometric approximation.The mean and maximum value of NO 2 VCD tr op were 5.43×10 15 and 7.15×10 16 molec·cm-2 during the observation period,respectively.The daily NO 2 VCD trop was lower,bu t there was an upward trend as a whole.The variation of NO 2 VCD trop wa s closely related to wind speed and direction:NO 2 VCD trop concentratio n was lower when southwesterly wind was weaker,and the northeasterly wind was conducive to the NO 2 diffusion.Generally,diurnal variations of NO 2 VC D trop showed the characteristics of being low at noon and high in the mo rning and evening,and the evening peak was slightly higher than the morning on e.The level and diurnal range of NO 2 VCD trop at Shangdianzi station we re significantly smaller than the results in the Beijing city over the same peri od.These variation characteristics were consistent with the ones at the mild p ollution stations of Xianghe and Gucheng in Hebei.In a word,reginal backgroun d atmospheric NO 2 VCD trop can be effectively monitored by MAX-DOAS,al though the characteristics were related to complex factors such as industrial an d traffic emission,photochemical reaction and atmospheric transport.More data a re necessary for further study.