Use of Receptor Models to Evaluate Sources of PAHs in Sediments

Letter commenting on “Primary sources and toxicity of PAHs in Milwaukee‐area streambed sediment”—To the editor

“…Given the variability in the PAH profiles of different categories of sources, minor differences in the statistical similarity ( X 2 ) between sediment samples and literature derived profiles does not support claims of causation. Technical issues concerning the non‐RTS source profiles used by Baldwin et al are described in detail elsewhere . Many of the profiles were derived from the work of Li et al , who had combined data from at least 22 different papers dating as far back as 1976.…”

“…The combined issues of variability within source types and the similarity of different source types can result in the failure of receptor models, such as CMB, to accurately estimate source contributions . Although the same source profiles have been used in other papers since 2010 , Van Metre and Mahler have presented no information that suggests any effort has been made to confirm their validity with new data.…”

In response to Bales (2014)

“…Subsequent articles positing RTS as a source of PAHs focus on use of the US Environmental Protection Agency's (USEPA) Chemical Mass Balance (CMB) model (Van Metre and Mahler ) to identify RTS as a significant source of PAHs in lake sediments. O'Reilly et al (; ) presented case studies illustrating the inappropriate use of CMB as a stand‐alone method of PAH source identification and apportionment by Van Metre and Mahler () and Crane (), respectively. Both the diagnostic ratio and subsequent CMB model forensic approaches have been criticized in the O'Reilly et al (; ) publications for relying on single source identification methods rather than taking multiple‐lines‐of‐evidence approaches.…”

“…A series of publications over the past decade, focused almost exclusively on RTS as a source of PAHs in the environment have attempted to attribute "about 90 percent-perhaps even 95 percent-of the PAH pollution in urban watersheds" (Scheibal 2005) (2014; 2015) presented case studies illustrating the inappropriate use of CMB as a stand-alone method of PAH source identification and apportionment by Van Metre and Mahler (2010) and Crane (2014), respectively. Both the diagnostic ratio and subsequent CMB model forensic approaches have been criticized in the O' Reilly et al (2014;2015) publications for relying on single source identification methods rather than taking multiple-lines-of-evidence approaches. Among the reasons PCTC filed a Freedom of Information Act (FOIA) action (PCTC v. USGS 2014) is that USGS-provided descriptions of files withheld (Table 1) from its response to PCTC's FOIA request seem to indicate that USEPA's UNMIX model and a mathematical method known as Positive Matrix Factorization (PMF) were, in fact, also used.…”

A Review of the Literature on Potential Effects of Runoff from Refined Coal‐Tar–Based Sealant Coating on Aquatic Organisms

“…In Mahler et al 2005 suggested that RCTS could be an important source of PAHs to some urban sediments. Although, the relative contribution of PAHs from RTCS to urban sediments has been the subject of debate (DeMott and Gauthier 2006;Van Metre et al 2009;DeMott et al 2010;Van Metre and Mahler 2010;O'Reilly et al 2012O'Reilly et al , 2014O'Reilly et al , 2015Crane 2014aCrane , 2014bGauthier and DeMott 2014;O'Reilly and Ahn 2017), concern regarding the potential for exposure of aquatic organisms to PAHs specifically derived from pavement sealers has continued (Mahler et al 2012;USGS 2016).…”