Severn Trent Laboratories, Inc. (STL) is offering new approaches to identify the bioavailable concentrations of contaminants in soils and sediments. The bioavailable concentrations are defined as those that become freely dissolved in the local environment. Traditional methods for estimating the bioavailable concentrations have proved deficient in predicting toxicity to sediment-dwelling organisms. Breakthrough advances in the measurement of soot carbon content, and direct measurement of analytes in the freely dissolved phase have significantly improved the data available to assess this type of toxicity.

STL has implemented a quantitative method for determining soot carbon content based on the analytical approach developed by Professor Örjan Gustaffson at MIT. When soot carbon is present the bioavailable fraction is significantly reduced and measurement of total organic carbon (TOC) by itself will not predict contaminant binding in sediments and soils. Determination of both TOC and soot carbon content dramatically improves the assessment of bioavailable carbon.

Another new technique is called isotope dilution solid phase microextraction (ID-SPME) and is based on work by Dr. Upal Ghosh at the University of Maryland and Dr. Steven Hawthorne at the University of North Dakota. It is designed to directly measure only the bioavailable contaminants in pore water after removal of particulates and colloids, and can accommodate very small sample sizes. STL was selected to participate in a Proof-of-Concept study provided to the USEPA, and is participating in an interlaboratory validation scheduled for completion in March 2007. STL is also contributing to an ASTM version of the method focused on polyaromatic hydrocarbons (PAHs).

When used in concert, the new techniques can help provide the chemical data necessary to more accurately predict bioavailability. STL expects that this will enable its clients to provide more accurate modeling and risk analysis, and more highly informed decision making and policies

About STL

Severn Trent Laboratories, Inc. (STL) is the industry's leading environmental testing company. Operations in the United States include 32 laboratories, 16 Service Centers and QED Environmental Systems, Inc., the leading supplier of groundwater sampling equipment and remediation pumping systems. STL affiliates include the Aerotech P&K team, which brings together the capabilities of Aerotech Laboratories, Inc. and P&K Microbiology Services, Inc. STL employs over 2,100 people and has revenues of $245 million in the United States.

For more information, contact:
Jim Miller
Vice President Business Development
Severn Trent Laboratories, Inc.
716-691-2600
Visit our website @ www.stl-inc.com