Performance evaluation of light weight gas sensor system suitable for airborne applications against co-location gas analysers over Delhi

In the present work, we discuss the light-weight gas sensor system (LWGSS) [350 g, 7″ ∗ 3″] originally developed at CSIR-National Physical Laboratory. This instrument is equipped with low-cost electrolytic gas sensors for quantifying major gaseous pollutants present in the atmosphere. Alphasense electrochemical gas sensors were used to measure gas pollutant species such as CO, SO₂, NO₂, O₃ and H₂S. In our experiment, we focus on the observation of CO, SO₂, NO₂, O₃ using this system. LWGSS has been designed for vertical observations using balloons or unmanned aerial vehicles (UAVs) to study the gaseous concentration in the atmospheric boundary layer (ABL). But, before using such instruments in field campaigns, there is a strong need for the inter-comparison of these instruments with that of the collocated high-end gas analysers. Thus, the inter-comparisons were performed between LWGSS and other high-end analysers during 6–7, March 2017 and 26–27, April 2017. The LWGSS system comprising all the sensors was compared against high-end analyser present at CSIR-NPL for ozone and other gas analysers present at IMD, New Delhi. The ozone sensor deployed in LWGSS showed good correlation (i.e. R² = 0.83, slope = 0.93) against the high-end ozone gas analyser, which was calibrated with primary ozone facility (SRP43) available at CSIR-NPL. Inter-comparisons performed for NO₂, SO₂ and CO showed different results. While the NO₂ gas sensor showed medium correlation (R² = 0.75; slope = 0.49), the SO₂ and CO gas sensor showed a poor correlation (and R² = 0.44; slope = 0.98; R² = 0.28, slope = 0.79) respectively, when compared with co-location gas analysers present at IMD, New Delhi. Comparisons were performed for LWGSS data during 1–28 February 2018 with data collected at CPCB station (Shadipur, Delhi) and IMD station (Pusa, Delhi). The comparison results showed variations in LWGSS CO and SO₂ data whereas LWGSS O₃ and NO₂ results were in accordance with data collected at aforementioned monitoring stations.