光腔衰荡光谱(CRDS)法观测我国4个本底站大气CO2

利用基于光腔衰荡光谱(CRDS)技术自组装的大气CO2在线观测系统,于2009年在青海瓦里关、浙江临安、北京上甸子和黑龙江龙风山4个世界气象组织全球大气观测网(WMO/GAW)大气本底站对大气CO2进行了在线观测.初步分析结果表明,4站全年大气CO2体积分数最低值出现在7～8月,夏季临安、龙风山和上甸子站CO2平均体积...     

Characterization of aerosol optical properties, chemical composition and mixing states in the winter season in Shanghai, China

Physical and chemical properties of ambient aerosols at the single particle level were studied in Shanghai from December 22 to 28, 2009. A Cavity-Ring-Down Aerosol Extinction Spectrometer（CRD-AES） and a nephelometer were deployed to measure aerosol light extinction and scattering properties, respectively. An Aerosol Time-of-Flight Mass Spectrometer（ATOFMS）was used to detect single particle sizes and chemical composition. Seven particle types were detected. Air parcels arrived at the sampling site from the vicinity of Shanghai until mid-day of December 25, when they started to originate from North China. The aerosol extinction,scattering, and absorption coefficients all dropped sharply when this cold, clean air arrived.Aerosol particles changed from a highly aged type before this meteorological shift to a relatively fresh type afterwards. The aerosol optical properties were dependent on the wind direction.Aerosols with high extinction coefficient and scattering Angstrom exponent（SAE） were observed when the wind blew from the west and northwest, indicating that they were predominantly fine particles. Nitrate and ammonium correlated most strongly with the change in aerosol optical properties. In the elemental carbon/organic carbon（ECOC） particle type, the diurnal trends of single scattering albedo（SSA） and elemental carbon（EC） signal intensity had a negative correlation. We also found a negative correlation（r =-0.87） between high mass-OC particle number fraction and the SSA in a relatively clean period, suggesting that particulate aromatic components might play an important role in light absorption in urban areas.     

Nocturnal atmospheric chemistry of NO3 and N2O5 over Changzhou in the Yangtze River Delta in China

Comprehensive observations of the nocturnal atmospheric oxidation of NO₃ and N₂O₅ were conducted at a suburban site in Changzhou in the YRD using cavity ring-down spectroscopy (CRDS) from 27 May to 24 June, 2019. High concentrations of NO₃ precursors were observed, and the nocturnal production rate of NO₃ was determined to be 1.7 ± 1.2 ppbv/hr. However, the nighttime NO₃ and N₂O₅ concentrations were relatively low, with maximum values of 17.7 and 304.7 pptv, respectively, illustrating the rapid loss of NO₃ and N₂O₅. It was found that NO₃ dominated the nighttime atmospheric oxidation, accounting for 50.7%, while O₃ and OH only contributed 34.1% and 15.2%, respectively. For the reactions of NO₃ with volatile organic compounds (VOCs), styrene was found to account for 60.3%, highlighting its dominant role in the NO₃ reactivity. In general, the contributions of the reactions between NO₃ and VOCs and the N₂O₅ uptake to NO₃ loss were found to be about 39.5% and 60.5%, respectively, indicating that N₂O₅ uptake also played an important role in the loss of NO₃ and N₂O₅, especially under the high humidity conditions in China. The formation of nitrate at night mainly originated from N₂O₅ uptake, and the maximum production rate of NO₃⁻ reached 6.5 ppbv/hr. The average NO_x consumption rate via NO₃ and N₂O₅ chemistry was found to be 0.4 ppbv/h, accounting for 47.9% of the total NO_x removal. The predominant roles of NO₃ and N₂O₅ in nitrate formation and NOx removal in the YRD region was highlighted in this study.     

近红外光腔衰荡光谱系统设计及研究

目的搭建一套近红外光腔衰荡光谱测量系统,实现水汽吸收的探测。方法通过测量有无样品存在时的衰荡时间,实现腔内介质吸收的探测。通过测量空腔衰荡时间,计算腔镜反射率。通过测量不同浓度的水汽吸收,验证系统是否可用于分子吸收的测量。结果该装置的空腔衰荡时间约为3.75μs,对应的腔镜反射率为99.982%,有效吸收光程为1.1 km。测量了6627.7 cm~(-1)处水汽的吸收,结果与HITRAN数据库一致。结合文献报道结果和HITRAN数据库吸收谱线,模拟得到了NH_3、C_2H_2、HO_2自由基在6625～6626 cm~(-1)范围内的吸收系数。结论该装置实现了水汽吸收的探测,在该装置的激光器工作波长范围内,可应用于NH_3、C_2H_2、HO_2自由基的实时探测。