Independent Consultants in Environmental and Forensic Chemistry

Volume 1, Issue 3, Fall 1997

How Old is This Petroleum Release?

Lead Fingerprinting

In the last two issues of Two Scents, the inability of the experts to scientifically determine the age of a petroleum product release has been discussed. This failure is due to the reliance on the rate of microbial degradation of the petroleum product in the environment. The rate of biological changes in the aging or "weathering" of a petroleum product is not known, nor is it predictable, nor can it be determined. Why? The microbiological degradation rate of a petroleum product in the environment, especially in soil and on or in groundwater, has numerous variables of which all, or most, are of unknown value. Some of these variables are: the amount of product released, oxygen concentration, types of microorganisms, nutrients available, the reaction rate order, temperature, moisture content, length of acclimation time, sequestration, adsorption of the product, predation of the microbes, etc.

Is all lost? Maybe not. In the last two issues of Two Scents, the only laboratory that provided acceptable results measured the ratio of lead isotopes to predict an age of 1965 " 3 years. The lead originated from the wear on truck motor bearings (wear metal). Since the facility was operational from 1964 to 1984, the wear metal lead reasonably came from motor bearings that were manufactured, on an average, in 1965 if their lead is to be found in used motor oil dumped, on the average, in 1975. OK, no cigar, but this method does show promise.

The method is based on Richard W. Hurst's model found in the feature article "The Lead Fingerprints of Gasoline Contamination," Hurst, Richard W., Terry E. Davis and Barbara D. Chinn, Environmental Science and Technology, Volume 30, Number 7, pp. 304A-307A, 1996. The model matches the change in lead isotopic ratios expected from the increased production of lead from Missouri and the decreased production of lead from Idaho and Montana. The natural abundance of lead isotopes is: Pb²⁰⁴ - 1.4%; Pb²⁰⁶ - 24.1%; Pb²⁰⁷ - 22.1%; and Pb²⁰⁸ - 52.4% but each lead source or mine will have its own isotopic percentages. None of these lead isotopes is radioactive.

Trillium, Inc., is actively working with Dr. Hurst to verify his model for use in aging petroleum product releases that contain lead as a gasoline additive or as a wear metal in lubricants.

Does anyone have an environmental petroleum product sample of known, documented age who is interested in testing the age of that sample by measuring the ratios of the isotopes of lead?

Laboratory Audits - Why Bother?

If you don't care about the quality of your analytical data, laboratory audits are not important. Although your data packages may seem to contain a lot of detail, events often occur in the laboratory that may not be obvious from reviewing the data package. The data package will not show you that the balance used to weigh the sample aliquot for analysis has not been calibrated in months or that samples routinely sit outside, unattended for several hours. The data package will not tell you that outdated calibration standards are stored in the same refrigerator or on the same shelf next to current working standards and could be used mistakenly to calibrate the instrument on which your samples will be analyzed. These issues, and many more, may become obvious if a laboratory audit is performed.

Generally, audits are prompted by one of three reasons. Audits are often used to select a laboratory to provide support to a project and to determine any weaknesses which may adversely affect the laboratory's ability to undertake and successfully complete the project. Although weaknesses may be uncovered, an assessment must be made to determine if those weaknesses are significant enough to disqualify the laboratory from serious consideration.

Some audits are prompted by problems encountered with a laboratory already supporting a given project. The nature of the specific problem should be known in detail in order to identify and address the areas that may be the cause of the problem. The audit may include a review of the associated data, review of sample storage and handling procedures, and/or a review of data reduction procedures. This type of audit focuses only on the areas of the specific problem rather than on the laboratory as a whole.

The third reason for conducting a laboratory audit would be at the request of the internal management due to concerns with various aspects of the laboratory. Internal management may choose to focus the audit around a particular area of concern or may decide on a more general audit to discover and correct internal weaknesses of the laboratory.

Regardless of the reason for the audit, problems encountered during the audit can be identified and addressed prior to committing the laboratory to generating crucial analytical data. A laboratory audit will increase your confidence in the abilities and capabilities of a laboratory and in the data generated by that laboratory. A laboratory audit should be seriously considered if you are concerned with the quality of your data.

Are Your Air Data Misleading You?

USEPA Method 18: Measurement of Gaseous Organic Compound Emissions by Gas Chromatography

On April 22, 1994, EPA finalized changes to Method 18 which included significant improvements in quality assurance requirements. The changes required that a recovery study be conducted for all compounds of interest using actual field samples, that the recoveries be in the range of 70-130% or be conducted by an on-line technique, that the results of the recovery study be included in the test report, and that all results of the test be corrected by the observed compound specific recovery factors. Even so, many studies conducted for purposes other than compliance demonstration still do not incorporate recovery studies.

Separate requirements are imposed on the three allowed sampling techniques: bags, adsorption tubes, and on-line. For bag samples, one of three bags is spiked in the laboratory with 40-60% of the observed analytes after the initial analysis is completed. For adsorption tube samples, two tubes must be collected at each sampling location. One of the two tubes must be spiked with 40-60% of the mass anticipated to be collected. The on-line techniques, direct interface or dilution interface, require mobilization of a gas chromatograph plus heated sampling lines and sampling pumps. Recovery is demonstrated by analysis of a mid-level calibration gas after it has passed through the entire sampling system. Projects conducted using on-site analysis are inherently more expensive than those conducted by techniques where samples collected in the field are shipped to a fixed laboratory.

Implementation of a recovery study will increase costs for test projects, possibly significantly. Unless the new Quality Assurance procedures are specifically requested or the test is specified to be conducted for compliance purposes, many reputable test firms will not propose to use the enhanced requirements or even mention them through concern of losing the job due to clients' known preferences for low-cost. Many clients, though advised of the benefits, may choose to trim costs by deleting the recovery study.

Many organic compounds in process vent streams are difficult to quantify and may have poor or non-existent recoveries. Recoveries for tubes often fail to meet the required levels, particularly for polar compounds. Bags fail more frequently. Data collected by techniques for which compound-specific and matrix-specific recoveries have not been determined may lead to reporting of low biased data and/or to incorrect design of control strategies. To provide valid defensible data, recovery studies should be conducted for all test projects, even those which are not intended to be used for demonstration of compliance.

Soil Samples: Where Did the Volatile Organic Compounds Go?

Ten years ago, testimony as to the accuracy of soil analyses for volatile organic compounds (VOCs) was heard from experts representing the federal government in the bench trial of United States of America v. Raymark et al., US District Court, Eastern District of Pennsylvania, Civil Action Number 85-3073. The experts agreed that approved US EPA sampling methodologies gave VOCs in soil results that were biased low. A new sample preservation technique utilizing methyl alcohol to retain the VOCs in the soil was field tested at Raymark.

Split samples (i.e., duplicates) were collected. One sample was taken using approved US EPA protocol and analyzed by the Contract Laboratory Program (CLP) method; the second sample was preserved with methyl alcohol. The analytical results were astonishing. The concentration of trichloroethylene (TCE) using the US EPA methods was reported as 0.06 mg/kg (ppm). Using the methyl alcohol method, the concentration of TCE was 3,300 mg/kg, 55,000 times greater than the EPA estimate or a loss of TCE exceeding four orders of magnitude.

Through the efforts of numerous independent researchers, the accuracy and reproducibility of the "methanol method," as it is now commonly called, has been demonstrated extensively in field trials. Numerous state and government agencies have adopted the method over the past ten years as the method of choice in characterizing the VOC contamination at a site. This is especially the case for Underground Storage Tank (UST) programs because researchers have found that aromatic organic compounds such as benzene, toluene, ethylbenzene and xylenes (BTEX), commonly found in gasolines, are readily destroyed by microbes even at 4C.

Despite this showing of confidence in the methanol method, the EPA has resisted recognizing the methanol method as a viable means for obtaining accurate results, relying instead on its published methods. However, finally after ten years, the recently promulgated US EPA SW- 846 Method 5035 allows the use of methyl alcohol in the field to preserve soil samples for VOCs.

Regardless of whether VOC analyses are conducted to characterize a site or to design remedial measures, accurate chemical results are required. Whenever VOCs are chemicals of concern, methyl alcohol preservation of soil samples is recommended.

A bibliography of references for methyl alcohol preservation of VOC soil samples is available from Eva Thomas, Trillium's Information Specialist.

Pardon Me Sir, Do You Have a Rabbit In Your Hat?

The next time you don your expensive felt hat, you may check to see if it is made of rabbit fur. Many fur felt hats are made from the hair from rabbit pelts. But the process of preparing the pelts is far from simple. Rabbit pelts contain residual fats, oils, and greases that must be removed before the hairs are stripped from the skin for the manufacture of felts. One way of doing this is to tumble the fresh pelts with sawdust saturated with a degreasing solvent. The solvent vapors penetrate the pelts and remove the greases which then become absorbed by the sawdust. The pelts are then stripped of the hair. But what about the grease and solvent-laden sawdust? Just throw it away? Where? When a rabbit pelt processing plant disposed of their sawdust in a landfill, the EPA charged them with disposal of hazardous waste containing trichloroethylene (TCE), the degreasing solvent.

Trillium was requested by the plant management to determine how much TCE may have been discarded in the landfill to counter the EPA charge that the complete inventory of TCE brought into the plant was disposed of in the landfill. A small replica of the degreasing tumbler was constructed to scale. Rabbit pelts, sawdust, and TCE, proportionate to that used in the production size tumblers, were placed in the apparatus and tumbled for the requisite time period. The pelts were removed, and the residual sawdust was analyzed for TCE.

Surprisingly, little, if any, TCE remained on the sawdust. The tumbling and extraction process apparently generated enough heat that the great majority of the TCE was vaporized. What TCE remained on the sawdust quickly evaporated so that little, if any, remained in the sawdust sent to the landfill. With this evidence in hand, the plant was able to come to a satisfactory settlement with the EPA...and you can still buy a hat with a rabbit in it.