Development of a tagged species source apportionment algorithm to characterize three‐dimensional transport and transformation of precursors and secondary pollutants

Abstract

[1] We developed a new tagged species source apportionment (TSSA) algorithm for tracking the direct mass contributions of selected emissions sources to the formation of particulates such as aerosol sulfate, nitrate, ammonium, elemental carbon, and secondary organic aerosols in the U.S. EPA Community Multiscale Air Quality Model (CMAQ). The focus of this paper is on sulfate, nitrate, and elemental carbon. The objective of the TSSA algorithm is to provide useful results in modeling studies for identifying important emissions categories and identifying possible emissions reduction strategies to attain particulate matter (PM) air quality goals. TSSA differs from model sensitivity approaches because it tracks direct mass contributions from specific emissions sources to the total PM concentration at selected receptor sites, while results from sensitivity approaches are affected by nonlinear chemistry that can change the concentration of sulfate, nitrate, and organic carbon secondary particulates. We evaluated the algorithm by comparing CMAQ/TSSA results with results from zero-out CMAQ sensitivity simulations. As expected, TSSA results were almost identical to the CMAQ sensitivity results for chemical species that do not undergo nonlinear chemical reactions. For chemical species with nonlinear chemical reaction, the TSSA results are expected to differ from model sensitivity results, but for small emissions changes the results are similar in the two approaches. We also compared CMAQ/TSSA to CAMx/PSAT. Because there are significant differences in the CMAQ and CAMx model predicted concentrations, the source attribution results differed for TSSA and PSAT; however, the rank order of emissions sources were similar for the two approaches at most receptor sites.Citation: Wang, Z. S., C.-J. Chien, and G. S. Tonnesen (2009), Development of a tagged species source apportionment algorithm to characterize three-dimensional transport and transformation of precursors and secondary pollutants,

A generalized tagging method

“…However, it was shown that this perturbation approach does not provide a reliable estimate of the contribution of these emissions to ozone and climate change (Wang et al, 2009;Grewe et al, 2010Grewe et al, , 2012Emmons et al, 2012). For example, when ozone production is saturated, i.e.…”

“…It is widely used in atmospheric chemistry, but only recently well documented (Grewe, 2004(Grewe, , 2012Wang et al, 2009;Gromov et al, 2010;Grewe et al, 2010;Butler et al, 2011;Emmons et al, 2012). In most applications, a subset of species is regarded and tagged without non-linear interaction between the individual species.…”

On the attribution of contributions of atmospheric trace gases to emissions in atmospheric model applications

“…Recently, EU-projects like QUANTIFY and ATTICA aimed at identifying the impact of transport sectors on climate (Fuglestvedt et al, 2009;Hoor et al, 2009;Lee et al, 2010). Wang et al (2009) pointed out that there is a difference in the nature of the two key topics (1) attribution of climate change to sectoral emissions and (2) evaluation of emission control scenarios, which also requires different methodologies. The attribution of concentrations to emissions is important to attribute climate change, which depends on absolute contributions, to sectoral emissions.…”

“…Wang et al, 2009). The tagging methodologies are differently designed and implemented, but they have in common that additional "tagged species" are included in the models, to which specific emissions are assigned and which undergo the same loss processes as the respective un-tagged species.…”

“…Generally, as pointed out by Wang et al (2009), it is important to differentiate between the two questions concerning attribution and emission control scenarios and to concede that the answers to these questions require two different methodologies. The attribution of atmospheric concentrations to emissions (and sources in general) in a numerical simulation framework can be obtained by a tagging methodology, whereas developing effective emission control scenarios is also obtained by sensitivity methods.…”