Abstract
Nitrous acid (HONO) is the major source of OH radicals in polluted regions and plays a key role in the nitrogen cycle of the atmosphere. Therefore, accurate measurements of HONO in the atmosphere is important. Long Path Absorption Photometer (LOPAP) is a common and highly sensitive method used for ambient HONO measurements. Incoherent Broadband Cavity Enhanced Absorption Spectroscopy (IBBCEAS) is a recent alternative for the detection of HONO with high temporal and spatial resolutions, which has shown a detection limit of 0.76 ppbv at a sampling average of 180 s. In this study, LOPAP and IBBCEAS-HONO instruments were deployed in a Shanghai Urban Site (Shanghai Academy of Environmental Sciences) and simultaneously recorded the data from both instruments for a quantitative intercomparison of the measured atmospheric HONO for four days from 30 December 2017–2 January 2018. The HONO concentration measured by IBBCEAS and LOPAP were well matched. The campaign average concentrations measured by IBBCEAS and LOPAP were 1.28 and 1.20 ppbv, respectively. The intercomparison results demonstrated that both the IBBCEAS-HONO instrument and LOPAP-HONO instrument are suitable for ambient monitoring of HONO in a polluted urban environment.
Highlights
The Incoherent Broadband Cavity Enhanced Absorption Spectroscopy (IBBCEAS) and Long Path Absorption Photometer (LOPAP) setup used in this work were developed in house
The saturated gaseous nitrophenol has strong absorption at near-UV [29]. It was injected into the sampling port of IBBCEAS setup by a micro-injector, and the sampling flow rate was controlled by an MFC
This excellent agreement in the results demonstrated the feasibility of IBBCEAS as an alternative method for HONO measurements
Summary
The IBBCEAS and LOPAP setup used in this work were developed in house. To ensure the reliability of the instruments, a series of performance characterizations: detection limits, residence times, calibrations, and stability, were carried out before field deployment in the laboratory of SAES. The nitrite concentrations proportioned during the calibration process of the device are 0. Long Path Absorption Photometer (LOPAP) is a detection technology based on a the N2 and replace the absorption solution (R1) with the configured standard solution. After the standard solution entering the system reacts with the reaction solution, the linear combines a chemical method with optical measurements to quantitatively measure HONO relationship between absorbance and liquid nitrite is obtained. 2 of the calibration plot is 0.9982, indicating that the instrument is currently in good conRtechniques adopted in this study, we established our LOPAP setup. The reasons affecting the calibration curve include the configuration of absorption provements were made to enhance the equipment performance as well as the operational solution and reaction solution, the configuration of standard solution, the cleaning of in-in and maintenance convenience.
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