Alkylated PAHs and the Benthic Organisms that Eat Them
October 20, 2009

Q:           What is an alkylated PAH?

A:            {engineers response} Gazuntite!

                {geologists response} Isn’t that a PAH that was created during a fire from the Archaean period?

                {chemists response} Aromatic ring structures in petroleum products range from one- to five-ring combinations. Two or more five or six-member carbon rings are fused together to form polyaromatic hydrocarbons (PAH). These petroleum PAHs have abundant alkyl group substitution on their ring structures. The alkyl groups generally have one to four saturated carbon atoms, and thus can produce many different structural isomers and homologs for each aromatic hydrocarbon family. The most abundant aromatic hydrocarbon families have two or three fused rings with one to four carbon atom alkyl group substitutions (denoted C1-, C2-, C3-, and C4- by GC/MS/SIM expanded scans). It is important to point out that crude oils contain primarily the alkyl homologs of aromatic compounds and relatively small quantities of the unsubstituted "parent" aromatic structures. {NPS 1997}

In short, alkylated PAHs are homolog groups of PAHs that are more abundant, more persistent, and in some cases more toxic (than the parent cPAHs). They are particularly of interest to the environmental community during sediment forensics and ecotoxicity studies when you have, for example, crude oil contamination of sensitive estuarine environments or when investigating MGP site sediments. Since this author is an engineer, I will not attempt to articulate further on the science or chemistry of alkylated PAHs. However, ECCS has seen an increased demand in testing for alkylated PAHs and responded in 2008 with the development and validation of a method using GC/MS SIM that we have since delivered in both a fixed and mobile laboratory setting.

ECCS has supported the cleanup of over 1,000 EPA, DoD, state and local sites over the past two decades. But the cleanup that brings us the greatest satisfaction is the cleanup of a 2-mile stretch of local community highway just south of our office. Most of our project work in one of our 12 mobile laboratories actually occurs outside of the state of Wisconsin, and almost none occurs here in Madison. So it is even more so imperative for us to live the mantra “Think Globally, Act Locally.” The Adopt-a-Highway (AAH) program allowed us to live that statement perfectly. This Fall, over half the office participated in the cleanup effort, and collectively we picked up over 10 bags of trash. It is both amazing and sad what some people discard along our roadways. Consider helping out YOUR local community by joining the nationwide AAH movement. It is both a team building exercise AND rewarding.