LQM is a specialist environmental consultancy based in Nottingham (UK) with an international reputation for assessing and managing the risks posed to human health and the environment by contaminants in soil. Increasingly this is being done within a context of sustainable development and specifically sustainable brownfield regeneration.
We provide consultancy, peer review and expert witness services, contract research and training courses on all aspects of the management of land contamination to problem holders, developers and local government.
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Quickly assess the potential source(s) of PAH contamination in soil samples . This can assist in clarifying the conceptual model for the site and hence the potential human health risks that may be posed by PAHs at your site.
A free trial version of the tool is available but has limited functionality. This full version offers a number of distinct benefits over the trial version, including:
Note: Use of the software represents acceptance of the Licence Agreement, which is also contained within the software. Please review the Licence Agreement prior to use. For organisations with multiple offices, a seperate copy of the software is required for each office.
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The ratios of certain pairs of PAH isomers (i.e. congeners with different structures but the same molecular mass) can also be used to infer the possible source of PAH mixtures found in environmental samples. By plotting each sample in terms of two such ratios, it is possible to tease apart mixtures with different PAH profiles and tentitively assign a possible source based on where these samples cluster within the plot. A range of possible ratios can be used and collectively these methods are referred to as "double ratio plots".
The LQM PAH Double Ratio Tool is a simple to use spreadsheet (Note: Microsoft Excel is required to use the tool) that calculates and plots three pairs of ratios and calculates a number of other indices that, collectively, can indicate the potential source(s) of PAH contamination, delineate different source terms and/or samples that may show different clustering. Simply paste in your PAH site data (EPA 16) to reveil possible/likely source(s) of the PAH contamination. This can assist in clarifying the conceptual model for the site and hence the potential human health risks that may be posed by PAHs.
If you want to know more, watch an hour-long recording of a webinar on double ratio plots, their strengths and weaknesses and the PAH Double Ratio Tool - click here.
The price includes personalisation of the tool with your company name or logo. Once the order has been received we will contact you (at the email address given in the account from which the order originated) with instructions on how to supply a suitable image file. We will replace the LQM logo (but not the copyright statement) on both charts with the image file you provide.
Once payment has been received the personalised tool will be delivered by email to the address given in the account from which the order originated.
Polyaromatic Hydrocarbon (PAH) mixtures are commonly encountered in urban and periurban soils. These PAHs can be associated with a diverse range of contaminative sources, including petrogenic (e.g. oil spills and coal storage), pyrolytic (e.g. ash, clinker, soot and atmosheric deposition of smoke, coal tars, etc) and phtyogenic (e.g. plant-derived peat, etc). Due to the prevailing chemical processes, the profile of PAH mixtures generated at high temperatures (i.e. pyrolytic sources) differ from those formed at more moderate temperatures (i.e. petrogenic sources). At many contaminated sites, different sources may dominate the PAH contamination in different areas. Understanding the possible/likely source(s) of the PAH contamination, and conditions of formation can assist in clarifying the conceptual model for the site and hence the potential human health risks that may be posed by PAHs.
The scientific literature reports a wide range of techniques that can help to identify the potential source of PAHs in the environment. Many of these involve sophisticated forensic methods (e.g. alkylated and non-alkylated PAH ratios or isotopic analysis) and/or complex statistical techniques (e.g. Principle Component Analysis). Such methods are not normally cost-effective for routine geoenvironmental investigations. Typically, site investigations only generate data relating to the concentrations of the US EPA16 PAH congeners within soil samples.
Authors, including Yunker et al. (2002) and Costa & Sauer (2005), have reported that the concentration ratios of certain of these PAH congeners can also be used to infer the possible source of PAH mixtures found in environmental samples, including soils and river or marine sediments. The ratios concerned usually involve pairs of isomers (i.e. congeners with different structures but the same molecular mass). By plotting each sample in terms of two such ratios, it is possible to tease apart mixtures with different PAH profiles and tentitively assign a possible source based on where these samples cluster within the plot. A range of possible ratios can be used and collectively these methods are referred to as "double ratio plots". Stogiannidis & Laane (2015) provide a useful review of the many different ratios and indices reported in the scientific literature and highlighted some of the large uncertainties in their use and the resulting potential for mis-identification of possible sources.
This spreadsheet tool allows a number of common double plots and ratios to be generated quickly and easily using your site-specific data, and these can help indicate the potential source(s) of PAH contamination, delineate different source terms and/or samples that may show different clustering. The ratios and plots included in the spreadsheet are restricted to those involving the US EPA 16 PAH congeners usually tested for during site investigation works in the UK.
However, there are a number of potential confounding factors to the use of double ratio plots. For example, mixtures of PAHs from two or more sources are likely to be wrongly attributed, as are mixtures that have undergone significant amounts of weathering or degradation since their release into the environment. Consequently, double ratio plots cannot definitively identify the source of PAH contamination, nor should they be used by themselves as the basis for making assumptions about the likely extent of human exposure (i.e. bioavailability assumptions must not be based on double ratio plots alone). The double ratio plots created by this tool are intended to indicate possible sources only. They could be used as one of the multiple lines of evidence needed to reach a robust conclusion regarding the source(s) of any PAHs, particularly if this has implications for the exposure assumptions applied in any risk assessment.
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