ORCID Profile
0000-0002-6908-5829
Current Organisation
York University
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Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1EM00187F
Abstract: Comparison of diurnally-average NO x pre- and during phase-I lockdown in two Indian cities. This work highlights that ambient levels post-lockdown were a complex interaction between emissions, meteorology, and chemistry.
Publisher: Copernicus GmbH
Date: 16-06-2020
Publisher: Copernicus GmbH
Date: 17-01-2023
Abstract: Abstract. Total gaseous chlorine (TClg) measurements can improve our understanding of unknown sources of Cl in the atmosphere. Existing techniques for measuring TClg have been limited to offline analysis of extracted filters and do not provide suitable temporal information on fast atmospheric processes. We describe high-time-resolution in situ measurements of TClg by thermolyzing air over a heated platinum (Pt) substrate coupled to a cavity ring-down spectrometer (CRDS). The method relies on the complete decomposition of TClg to release Cl atoms that react to form HCl, for which detection by CRDS has previously been shown to be fast and reliable. The method was validated using custom organochlorine permeation devices (PDs) that generated gas-phase dichloromethane (DCM), 1-chlorobutane (CB), and 1,3-dichloropropene (DCP). The optimal conversion temperature and residence time through the high-temperature furnace was 825 ∘C and 1.5 s, respectively. Complete conversion was observed for six organochlorine compounds, including alkyl, allyl, and aryl C–Cl bonds, which are amongst the strongest Cl-containing bonds. The quantitative conversion of these strong C–Cl bonds suggests complete conversion of similar or weaker bonds that characterize all other TClg. We applied this technique to both outdoor and indoor environments and found reasonable agreements in ambient background mixing ratios with the sum of expected HCl from known long-lived Cl species. We measured the converted TClg in an indoor environment during cleaning activities and observed varying levels of TClg comparable to previous studies. The method validated here is capable of measuring in situ TClg and has a broad range of potential applications.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1EN00277E
Abstract: Sub-micron aerosol filtration of non-woven materials and fabric treatments were investigated. Select low-cost, readily available and easily cut non-woven materials were identified as suitable filter inserts for cloth-based masks.
Publisher: Copernicus GmbH
Date: 16-06-2020
DOI: 10.5194/AMT-2020-209
Abstract: Abstract. Atmospheric HONO mixing ratios in indoor and outdoor environments span a range of less than a few parts per trillion by volume (pptv) up to tens of parts per billion by volume (ppbv) in combustion plumes. Previous HONO calibration sources have utilized proton transfer acid displacement from nitrite salts or solutions, with output that ranges from tens to thousands of ppbv. Instrument calibrations have thus required large dilution flows to obtain atmospherically relevant mixing ratios. Here we present a simple universal source to reach very low HONO calibration mixing ratios using a nitrite-coated reaction device with the addition of humid air and/or HCl from a permeation device. The calibration source developed in this work can generate HONO across the atmospherically relevant range and has high purity (90–99 %), reproducibility, and tunability. Mixing ratios at the tens of pptv level are easily reached with reasonable dilution flows. The calibration source can be assembled to start producing stable HONO mixing ratios (RSE ≤ 2 %) within two hours, with output concentrations varying ≤ 25 % following simulated transport or complete disassembly of the instrument, and ≤ 10 % under ideal conditions. The simplicity of this source makes it highly versatile for field and lab experiments. The platform facilitates a new level of accuracy in established instrumentation, as well as intercomparison studies to identify systematic HONO measurement bias and interferences.
Publisher: Copernicus GmbH
Date: 06-11-2020
Abstract: Abstract. Atmospheric HONO mixing ratios in indoor and outdoor environments span a range of less than a few parts per trillion by volume (pptv) up to tens of parts per billion by volume (ppbv) in combustion plumes. Previous HONO calibration sources have utilized proton transfer acid displacement from nitrite salts or solutions, with output that ranges from tens to thousands of ppbv. Instrument calibrations have thus required large dilution flows to obtain atmospherically relevant mixing ratios. Here we present a simple universal source to reach very low HONO calibration mixing ratios using a nitrite-coated reaction device with the addition of humid air and/or HCl from a permeation device. The calibration source developed in this work can generate HONO across the atmospherically relevant range and has high purity ( 90 %), reproducibility, and tunability. Mixing ratios at the tens of pptv level are easily reached with reasonable dilution flows. The calibration source can be assembled to start producing stable HONO mixing ratios (relative standard error, RSE ≤ 2 %) within 2 h, with output concentrations varying ≤ 25 % following simulated transport or complete disassembly of the instrument and with ≤ 10 % under ideal conditions. The simplicity of this source makes it highly versatile for field and lab experiments. The platform facilitates a new level of accuracy in established instrumentation, as well as intercomparison studies to identify systematic HONO measurement bias and interferences.
Location: United States of America
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