Development of an incoherent broadband cavity-enhanced absorption spectrometer for in situ measurements of HONO and NO<sub>2</sub>
<p>Gaseous nitrous acid (HONO) is an important source of OH radicals in the troposphere. However, its source, especially that during daytime hours remains unclear. We present an instrument for simultaneous unambiguous measurements of HONO and NO<sub>2</sub> with high time resolu...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-07-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/11/4531/2018/amt-11-4531-2018.pdf |
| Summary: | <p>Gaseous nitrous acid (HONO) is an important source of OH radicals in the
troposphere. However, its source, especially that during daytime hours
remains unclear. We present an instrument for simultaneous unambiguous
measurements of HONO and NO<sub>2</sub> with high time resolution based on
incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS). To
achieve robust performance and system stability under different environment
conditions, the current IBBCEAS instrument has been developed with
significant improvements in terms of efficient sampling as well as resistance
against vibration and temperature change, and the IBBCEAS instrument also has
low power consumption and a compact design that can be easily deployed on
different platforms powered by a high-capacity lithium ion battery. The
effective cavity length of the IBBCEAS was determined using the absorption of
O<sub>2</sub>-O<sub>2</sub> to account for the <q>shortening</q> effect caused by the
mirror purge flows. The wall loss for HONO was estimated to be 2.0 % via
a HONO standard generator. Measurement precisions (2<i>σ</i>) for HONO and
NO<sub>2</sub> are about 180 and 340 ppt in 30 s, respectively. A field
inter-comparison was carried out at a rural suburban site in Wangdu, Hebei
Province, China. The concentrations of HONO and NO<sub>2</sub> measured by
IBBCEAS were compared with a long optical path absorption photometer (LOPAP)
and a NO<sub><i>x</i></sub> analyzer (Thermo Fisher Electron Model 42i), and the
results showed very good agreement, with correlation coefficients (<i>R</i><sup>2</sup>)
of HONO and NO<sub>2</sub> being ∼ 0.89 and ∼ 0.95, respectively; in
addition, vehicle deployments were also tested to enable mobile measurements
of HONO and NO<sub>2</sub>, demonstrating the promising potential of using
IBBCEAS for in situ, sensitive, accurate and fast simultaneous measurements
of HONO and NO<sub>2</sub> in the future.</p> |
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| ISSN: | 1867-1381 1867-8548 |