Source apportionment to support air quality planning: Strengths and weaknesses of existing approaches

Abstract

Information on the origin of pollution constitutes an essential step of air quality management as it helps identifying measures to control air pollution. In this work, we review the most widely used source-apportionment methods for air quality management. Using theoretical and real-case datasets we study the differences among these methods and explain why they result in very different conclusions to support air quality planning. These differences are a consequence of the intrinsic assumptions that underpin the different methodologies and determine/limit their range of applicability. We show that ignoring their underlying assumptions is a risk for efficient/successful air quality management as these methods are sometimes used beyond their scope and range of applicability. The simplest approach based on increments (incremental approach) is often not suitable to support air quality planning. Contributions obtained through mass-transfer methods (receptor models or tagging approaches built in air quality models) are appropriate to support planning but only for specific pollutants. Impacts obtained via “brute-force” methods are the best suited but it is important to assess carefully their application range to make sure they reproduce correctly the prevailing chemical regimes.

Prediction of source contributions to urban background PM<sub>10</sub> concentrations in European cities: a case study for an episode in December 2016 using EMEP/MSC-W rv4.15 and LOTOS-EUROS v2.0 – Part 1: The country contributions

“…The layer on top of a 25 m surface layer follows the mixing layer height, which is obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) meteorological input data that are used to force the model. The horizontal advection of pollutants is calculated by applying a monotonic advection scheme developed by Walcek and Aleksic (1998).…”

Review of gmd-2019-296

“…Especially in the introduction (p2l11ff) 'contributions' and 'impacts' are mixed. With the 'direct' method only impacts can be calculated and only for linear species 'impact' equals 'contribution' (see e.g., Thunis et al, 2019). C4…”

Local fractions – a method for the calculation of local source contributions to air pollution, illustrated by examples using the EMEP MSC-W model (rv4_33)

“…Many different methods exist to extract information about the origin of air pollution (e.g., Thunis et al , 2019;Clappier et al, 2017). Some of them are based on measurements of the chemical composition of air masses in the region or interest (receptor region).…”