AQESHOW 2018 - Abstract

Abstract Title: Is your air monitoring equipment over-reporting NO2 emissions?
Presenter Name: Charles A. Odame-Ankrah
Company/Organisation: Global Analyzer Systems Ltd
Country: Canada

Abstract Information :

Nitrogen dioxide, NO2, is an air pollutant linked with negative impacts on human health, ecosystem health, and ozone production in the troposphere. The ozone made is equally toxic to the environment as well. Because of these known effects, NO2 is regulated and classified as a criteria pollutant by the US-EPA under the Clean Air Act. NO2 is also central in the processing of nitrogen oxide species in the troposphere to form other highly oxidized species such as peroxyacetyl nitrates (PANs), multifunctional organic nitrates (RONO2), nitric acid (HNO3), and particulate nitrate (pNO3-). All these species together with ozone production and/or destruction can deposit to ecosystems and can adversely affect acid sensitive ecosystems, smog formation, etc. The effects of NO2 listed above are the underlying reasons for the need for accurate quantification of this species to better understand its chemical processing in ambient air and the need to control it. Recent studies published clearly show that heated Molybdenum NO2 converters inside chemiluminescence NOX analyzers routinely lead to overestimation of NO2. This error can be addressed using an alternative 'true' NO2 converter which selectively converts NO2 to NO as published in literature. There are commercial photolysis based NOx analyzers available which have been approved as a federal equivalent method (FEM) for 'true' NO2 measurement by the US-EPA, but the question of what happens to the plethora of existing heated catalyst-based NOX analyzers in use today remains. In this presentation, it is shown that a new photolytic NO2 converter can be used as a simple add-on to existing chemiluminescence analyzers enabling them to operate as 'true' NO2 and NO measurement devices. It has been proven through laboratory and field trials, and was tested as a direct replacement, or retrofit, of a heated Molybdenum NO2 converter. Experiments were conducted at reduced pressure (200 mmHg), and over a wide linear dynamic range (tested from 0.03 to 37.30 ppm) with a converter efficiency greater than 96%, which shows results that have surpassed the performance of any known photolytic NO2 converter. A case study of device implementation in an ambient application side-by-side with an analyzer using a heated metal catalyst is presented and discussed.