講演情報
[AAS08-P27]A 3-kg payload IBBCEAS instrument for 4-D mapping of the NO3 Radical
*Shogo Saito1、Mixtli Campos-Pineda1、Albert Ruth1 (1.University College Cork)
キーワード：
Nitrate radical / NO3、IBBCEAS、nighttime chemistry、residual layer、UAV payload、vertical profiling
The nitrate radical, NO3, is the dominant oxidizing species in the nocturnal atmosphere [1] and plays an important role in many tropospheric reaction mechanisms. It reacts with biogenic [2,3] and anthropogenic [4] volatile organic compounds (VOCs) and is therefore responsible for the chemical transformation and eventual removal of many species from the troposphere at night-time. The reactions of NO3 with VOCs are also believed to be a night-time source of OH radicals. Many of the reactions of NO3 produce nitric acid and thus contribute to acid deposition in the environment. Furthermore, the reactions of NO3 with certain hydrocarbons, such as phenols, can lead to secondary organic aerosol (SOA) formation [5]. [AR1]
The spatial distribution of NO3 in the night-time planetary boundary layer strongly depends on the presence of NO and its transport within the planetary boundary layer, because NO efficiently destroys NO3 to form NO2. Since most NO sources are at ground level, and owing to the inefficient mixing of air masses during night-time (due to a lack of convection currents), NO3 generally exhibits positive vertical concentration gradients and can be highly stratified within the first few hundred meters [6]. Concentrations measurements as a function of altitude have been mostly performed on meteorological towers, with limited vertical resolution, no spatial flexibility (location is pre-set) and high operational costs.
To avoid these experimental difficulties and improve the observational capabilities for NO3, we have developed a compact (75 cm × 25 cm × 20 cm), low-power (~20 W), and lightweight (~3 kg) extractive instrument based on Incoherent Broadband Cavity-Enhanced Absorption Spectroscopy (IBBCEAS) [7]. The strong absorption at 662 nm is used for NO3 detection, and a 3s detection limit has achieved 8×10-9 cm-1Hz-1/2. A 24 V battery powers the instrument and allows for a 2 h operation. With a total weight of ~3 kg it can in principle be deployed on an Unmanned Aerial Vehicle (UAV) that can handle this payload, allowing for a 4D-mapping (space and time) of NO3 at any location.
In this contribution, we will present experiments to characterize the performance of the instrument using the Irish Atmospheric Simulation Chamber (IASC) at University College Cork (UCC). The instrument’s stability will be reported, and its inlet losses examined in comparison with an established open-path IBBCEAS instrument. Validation measurements and data retrieval will be discussed for several simulated environmental conditions: (a) under humid conditions, (b) in the presence of particles, (c) in the presence of atmospherically relevant molecules (e.g. VOCs). Finally we discuss the potential for this platform to perform high-resolution ground-based measurements and deployment on UAVs.
Grant acknowledgement: Research Ireland/FFP-A-8973 (AtmoTrace)
[1] S.S. Brown, J. Stutz, Nighttime radical observations and chemistry, Chem. Soc. Rev. 41 (2012) 6405-6447.
[2] N.L. Ng, et al., Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic aerosol Atmos. Chem. Phys. 17 (2017) 2103-2162.
[3] J. Laothawornkitkul, et al., Biogenic volatile organic compounds in the Earth system, New Phytologist, 183 (2009) 27-51.
[4] R. Friedrich, A. Obermeier, Chapter 1 - Anthropogenic Emissions of Volatile Organic Compounds, Ed. C.N. Hewitt, Reactive Hydrocarbons in the Atmosphere, Academic Press, New York, (1999) 1-39.
[5] H. Gong, et al., Products and Mechanism of Secondary Organic Aerosol Formation from Reactions of Linear Alkenes with NO3 Radicals, J. Phys. Chem. A 109 (2005) 4312-4324.
[6] A. K. Benton, et al., Night-time chemistry above London: measurements of NO3 and
N2O5 from the BT Tower, Atmos. Chem. Phys. 10 (2010) 9781-9795.
[7] S.E. Fiedler, et al., Incoherent broad-band cavity-enhanced absorption spectroscopy, Chem. Phys. Lett. 371 (2003) 284-294.
The spatial distribution of NO3 in the night-time planetary boundary layer strongly depends on the presence of NO and its transport within the planetary boundary layer, because NO efficiently destroys NO3 to form NO2. Since most NO sources are at ground level, and owing to the inefficient mixing of air masses during night-time (due to a lack of convection currents), NO3 generally exhibits positive vertical concentration gradients and can be highly stratified within the first few hundred meters [6]. Concentrations measurements as a function of altitude have been mostly performed on meteorological towers, with limited vertical resolution, no spatial flexibility (location is pre-set) and high operational costs.
To avoid these experimental difficulties and improve the observational capabilities for NO3, we have developed a compact (75 cm × 25 cm × 20 cm), low-power (~20 W), and lightweight (~3 kg) extractive instrument based on Incoherent Broadband Cavity-Enhanced Absorption Spectroscopy (IBBCEAS) [7]. The strong absorption at 662 nm is used for NO3 detection, and a 3s detection limit has achieved 8×10-9 cm-1Hz-1/2. A 24 V battery powers the instrument and allows for a 2 h operation. With a total weight of ~3 kg it can in principle be deployed on an Unmanned Aerial Vehicle (UAV) that can handle this payload, allowing for a 4D-mapping (space and time) of NO3 at any location.
In this contribution, we will present experiments to characterize the performance of the instrument using the Irish Atmospheric Simulation Chamber (IASC) at University College Cork (UCC). The instrument’s stability will be reported, and its inlet losses examined in comparison with an established open-path IBBCEAS instrument. Validation measurements and data retrieval will be discussed for several simulated environmental conditions: (a) under humid conditions, (b) in the presence of particles, (c) in the presence of atmospherically relevant molecules (e.g. VOCs). Finally we discuss the potential for this platform to perform high-resolution ground-based measurements and deployment on UAVs.
Grant acknowledgement: Research Ireland/FFP-A-8973 (AtmoTrace)
[1] S.S. Brown, J. Stutz, Nighttime radical observations and chemistry, Chem. Soc. Rev. 41 (2012) 6405-6447.
[2] N.L. Ng, et al., Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic aerosol Atmos. Chem. Phys. 17 (2017) 2103-2162.
[3] J. Laothawornkitkul, et al., Biogenic volatile organic compounds in the Earth system, New Phytologist, 183 (2009) 27-51.
[4] R. Friedrich, A. Obermeier, Chapter 1 - Anthropogenic Emissions of Volatile Organic Compounds, Ed. C.N. Hewitt, Reactive Hydrocarbons in the Atmosphere, Academic Press, New York, (1999) 1-39.
[5] H. Gong, et al., Products and Mechanism of Secondary Organic Aerosol Formation from Reactions of Linear Alkenes with NO3 Radicals, J. Phys. Chem. A 109 (2005) 4312-4324.
[6] A. K. Benton, et al., Night-time chemistry above London: measurements of NO3 and
N2O5 from the BT Tower, Atmos. Chem. Phys. 10 (2010) 9781-9795.
[7] S.E. Fiedler, et al., Incoherent broad-band cavity-enhanced absorption spectroscopy, Chem. Phys. Lett. 371 (2003) 284-294.