On-site testing is at the forefront of technologies used to reduce uncertainty in Phase II Environmental Site Assessments (ESAs).
As part of the ESA process, areas of environmental concern are identified, as well as which contaminants are most likely to be found there during soil assessment. These “contaminants of concern” provide focus to potential screening tools which can analyse soil samples for those specific compounds.
While combustible gas meters like PIDs have been used for screening for volatile compounds for decades more recent developments in screening technologies has both increased the accuracy of detection and range of potential contaminants to include metals, and heavier end hydrocarbons.
|Field Tool||Contaminants of Concern|
|XRF||Metals – lead, arsenic, etc|
|UVF||Petroleum hydrocarbons, polyaromatic hydrocarbons|
|PID||Volatile organic compounds|
By example, contaminant levels on sites with suspected heavy end hydrocarbon impacts like diesel or poly aromatic hydrocarbons have always been difficult to quantify in the field because of the lack of volatility of the compounds. Olfactory or visual evidence is also unreliable as they do not correlate well with laboratory results. For the detection of these compounds ultraviolet fluorescence (UVF) is of benefit as they fluoresce well under ultraviolet light. By comparison of fluorescence signatures with known standards the assessor can also quantify contaminant levels and more accurately guide the investigation or remedial field work.
If heavy end PAH or PHC compounds are difficult to quantify in the field then metals are generally impossible to quantify since most metal impacts lack any reliable visible, olfactory or similar response. These restrictions are eliminated with the use of x-ray fluorescence (XRF) which can supply single digit ppm detection limit responses for most priority metals. XRF detects the unique fluorescent signature of individual elements as energy (in the form of x-rays) is applied to the sample yielding element specific results in minutes while in the field.
Some of the metals that can be detected with XRF include:
XRF is designed to non-destructively determine the chemistry of a soil sample (also can be used for plastics, building materials, paint, and more). This is made possible because every element has a unique x-ray signature.
Reproducible Results correlated to Laboratory Analyses
The importance of quality site screening data correlated to representative laboratory results cannot be over emphasized. AEL collects samples in a methodical way, uses industry standard quality control practices and non-repetitive barcode labelling of samples. In addition AEL follows a rigorous investigative protocol developed by the US EPA triad working group to ensure site specific action levels are developed based on AELs extensive comparative work with duplicate field screening and laboratory results.
What is the Value of Data from On-Site Testing?
On-site testing is a fast and cost-effective way to obtain data that can reduce uncertainty in site investigations. This is valuable to a site owner because it eliminates the guesswork for finding areas of contamination and allows the investigative team to zero in on the boundaries of the impacted areas in as little time as possible.
This saves time on site, bringing the cost of the investigation down. The other benefit of on-site testing is that the site visualization tools (maps with sampling results overlayed) can show clear trends and give information that would be otherwise unavailable. The confidence this brings to decision-making furthers the investigative and remedial goals for the site.