上甸子区域大气本底站NO2柱浓度光谱反演及其变化特征

为了探究京津冀本底浓度地区NO₂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NO₂柱浓度反演研究。在NO₂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NO₂对流层垂直柱浓度（VCD_trop）。观测期间NO₂ VCD_trop平均值和最大值分别为5.43×1015和7.15×1016 molec·cm-2。NO₂ VCD_trop日均值浓度水平较低，但总体上有上升趋势。NO₂ VCD_trop变化过程与风速风向关系密切：西南风时风速越小NO₂ VCD_trop越低，东北风对NO₂ VCD_trop有扩散稀释作用。NO₂ 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NO₂ 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。NO₂ 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NO₂ 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。

Spectral Inversion and Characteristics of NO2 Column Density at Shangdianzi Regional Atmospheric Background Station

In order to explore the variation characteristics of significant air pollutant NO₂ in the Beijing-Tianjin-Hebei background region, the Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) was used to record solar scattering spectra at Shangdianzi regional atmospheric background station and retrieve the NO₂ column densities. Quantitative spectral analysis was carried out in the characteristic wavelength of NO₂ 405～430 nm. The NO₂ tropospheric vertical column densities (VCD_trop) from July 2009 to September 2009 were calculated through geometric approximation. The mean and maximum value of NO₂ VCD_trop were 5.43×1015 and 7.15×1016 molec·cm-2 during the observation period, respectively. The daily NO₂ VCD_trop was lower, but there was an upward trend as a whole. The variation of NO₂ VCD_trop was closely related to wind speed and direction: NO₂ VCD_trop concentration was lower when southwesterly wind was weaker, and the northeasterly wind was conducive to the NO₂ diffusion. Generally, diurnal variations of NO₂ VCD_trop showed the characteristics of being low at noon and high in the morning and evening, and the evening peak was slightly higher than the morning one. The level and diurnal range of NO₂ VCD_trop at Shangdianzi station were significantly smaller than the results in the Beijing city over the same period. These variation characteristics were consistent with the ones at the mild pollution stations of Xianghe and Gucheng in Hebei. In a word, reginal background atmospheric NO₂ VCD_trop can be effectively monitored by MAX-DOAS, although the characteristics were related to complex factors such as industrial and traffic emission, photochemical reaction and atmospheric transport. More data are necessary for further study.