title: Data Verification Tools for Minimizing Management Costs of Dense Air-Quality Monitoring Networks.
abstract: Aiming at minimizing the costs, both of capital expenditure and maintenance, of an extensive air-quality measurement network, we present simple statistical methods that do not require extensive training data sets for automated real-time verification of the reliability of data delivered by a spatially dense hybrid network of both low-cost and reference ozone measurement instruments. Ozone is a pollutant that has a relatively smooth spatial spread over a large scale although there can be significant small-scale variations. We take advantage of these characteristics and demonstrate detection of instrument calibration drift within a few days using a rolling 72 h comparison of hourly averaged data from the test instrument with that from suitably defined proxies. We define the required characteristics of the proxy measurements by working from a definition of the network purpose and specification, in this case reliable determination of the proportion of hourly averaged ozone measurements that are above a threshold in any given day, and detection of calibration drift of greater than ±30% in slope or ±5 parts-per-billion in offset. By analyzing results of a study of an extensive deployment of low-cost instruments in the Lower Fraser Valley, we demonstrate that proxies can be established using land-use criteria and that simple statistical comparisons can identify low-cost instruments that are not stable and therefore need replacing. We propose that a minimal set of compliant reference instruments can be used to verify the reliability of data from a much more extensive network of low-cost devices.
authors.affiliation: School of Environment, Faculty of Science, University of Auckland , Auckland 1142, New Zealand.|MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical Sciences, Faculty of Science, University of Auckland , Auckland 1142, New Zealand.
authors.forename: Georgia
authors.initials: G
authors.lastname: Miskell
authors.affiliation: School of Environment, Faculty of Science, University of Auckland , Auckland 1142, New Zealand.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Salmond
authors.affiliation: MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical Sciences, Faculty of Science, University of Auckland , Auckland 1142, New Zealand.|Department of Mathematics, Faculty of Science, University of Auckland 1142, Auckland, New Zealand.
authors.forename: Maryam
authors.initials: M
authors.lastname: Alavi-Shoshtari
authors.affiliation: Air Quality Ltd, 40A George Street, Mt Eden, Auckland 1024, New Zealand.
authors.forename: Mark
authors.initials: M
authors.lastname: Bart
authors.affiliation: Meteorological Services of Canada, Environment Canada, Vancouver V1V 1V7, Canada.
authors.forename: Bruce
authors.initials: B
authors.lastname: Ainslie
authors.affiliation: School of Environment, Faculty of Science, University of Auckland , Auckland 1142, New Zealand.|MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical Sciences, Faculty of Science, University of Auckland , Auckland 1142, New Zealand.
authors.forename: Stuart
authors.initials: S
authors.lastname: Grange
authors.affiliation: Department of Geography, The University of British Columbia , Vancouver V6T 1ZU, Canada.
authors.forename: Ian G
authors.initials: IG
authors.lastname: McKendry
authors.affiliation: Aeroqual Ltd, 109 Valley Road, Mt Eden, Auckland 1024, New Zealand.
authors.forename: Geoff S
authors.initials: GS
authors.lastname: Henshaw
authors.affiliation: MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical Sciences, Faculty of Science, University of Auckland , Auckland 1142, New Zealand.
authors.forename: David E
authors.initials: DE
authors.lastname: Williams
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D003365:Costs and Cost Analysis; D004784:Environmental Monitoring / Q000191:economics / Q000592:standards*; D006801:Humans; D010126:Ozone / Q000032:analysis*; D012015:Reference Standards; D015203:Reproducibility of Results
chemical_list: D000393:Air Pollutants; D010126:Ozone