Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1850:p23
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1850 (pt 23/117)
Character Range: 409900–413034

they are capable of detecting relevant contaminants
    * adequate understanding of the methods of use for the particular instrument, its limitations and site conditions that may affect the results
    * appropriate calibration (and recording of the calibration data) for the substances being measured
    * an appraisal of site conditions that may affect the results, e.g. high soil moisture may result in artificially high PID results for benzene.
Further information on field characterisation techniques may be found on the US EPA CLU-IN website at www.clu-in.org/characterization/.

    7.4.1          Gas detector tubes
Detector tubes have been developed that measure volatile gases including individual compounds, for example, hydrogen sulphide, or groups of compounds, for example, petroleum hydrocarbons. They can provide a direct measure of the analyte in ambient air or an indirect measurement of soil and groundwater contaminant concentration when used in field test kits for measurement of soil vapour and headspace for liquids. The reagents in the tubes may react with compounds of similar chemical properties; consequently, false positives and inaccurate results are possible and should be identified in the DQO process.

    7.4.2          Colorimetric test kits
Colorimetric tests rely on the chemical reactions of indicator compounds with individual compounds or classes of compounds. Tests are generally performed by mixing reagents in specified amounts with the soil sample to be tested and comparing the resultant colour change with a colour chart or using a field colorimeter to determine concentration.

Colorimetric tests have been developed for a wide range of substances including BTEX, total PAHs, chlorinated hydrocarbons, PCBs and various individual pesticides and classes of pesticide. The detection limits in soil are generally in the low ppm range (lower detection limits are achievable in water as no extraction stage is necessary). Although these tests are relatively simple to perform, depending on the kit, they can suffer from interferences from other co-contaminants or naturally occurring materials or organic matter. Their usefulness for specific site-characterisation purposes can be evaluated by comparison of field colorimetric results with laboratory results over a range of analyte concentrations.

    7.4.3          Headspace testing using photo-ionisation and flame ionisation detectors
Field headspace testing is a commonly used method for screening soil samples for volatile and semi-volatile organic compounds. The procedure involves partially filling an airtight container with a fresh soil sample and then analysing the headspace vapour using an appropriately calibrated portable instrument, typically a PID or FID.

A FID uses a hydrogen flame to ionise the organic vapours whereas a PID uses an ultraviolet lamp to ionise the vapours. The instrument response is related to the electric current generated by the ionised compounds. FIDs are most sensitive to aliphatic hydrocarbons as these compounds burn more efficiently than aromatic compounds. PID instruments are most sensitive