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适用范围：<p>Direct push LIF is used for site investigations where the delineation of petroleum hydrocarbons and other fluorophores is necessary. Generic terms for these investigations are site assessments and hazardous waste site investigations. Continuous LIF is used to provide information on the relative amounts of contamination and to provide a lithological detail of the subsurface strata. These investigations are frequently required in the characterization of hazardous waste sites.</p> <p>This technology provides preliminary results within minutes following the completion of each test. This allows the number, locations, and depths of subsequent tests to be adjusted in the field. Field adjustment may increase the efficiency of the investigation program.</p> <p>The rapid fluorescence data gathering provided by direct push LIF provides information necessary to assess the presence of contamination in soils and associated pore fluids in the field. This method allows for immediate determination of relative amounts of contamination. This allows the number, locations, and depths of subsequent activities to be adjusted in the field. Field adjustment may increase the efficiency of the investigation program.</p> <p>With appropriate sensors, the direct-push investigation program can provide information on soil stratigraphy and the distribution of petroleum and other fluorophores in the subsurface. This method results in minimum site disturbance and generates no cuttings that might require disposal <span class="bold">(1)</span>. </p> <p>This practice is confirmed using soil samples collected at given depths to confirm the fluorescence readings using a field deployed EPA Method 418.1 <span class="bold">(2)</span>, EPA method 8015-modified, and a modified EPA 8270 Method <span class="bold">(3)</span>, or equivalent methodologies, as compared to the fluorescence reading from the same depth from the sensor to verify that the fluorescence correlates with the contamination. The collected samples are also tested on the probe window in the truck to ensure the sample collected is representative of the region tested in situ.</p> <p>This practice may not be the correct method for preliminary or supplemental investigations in all cases. Chemical and physical properties of site specific soil matrices may have an effect on site specific detection limits. Subsurface conditions affect the performance of the equipment and methods associated with the direct push method. Direct push methods are not effective in pushing in solid bedrock and are marginally effective in pushing in weathered formations. Dense gravelly tills where boulders and cobbles are present, stiff and hard clays, and cemented soil zones may cause refusal and potential probe breakage. Certain cohesive soils, depending on their moisture content, can create friction on the cone penetrometer probes which can eventually equal or exceed the static reaction force and/or the impact energy being applied. As with all direct push methods, precautions must be taken to prevent cross contamination of aquifers through migration of contaminants up or down the cone penetrometer hole.</p> <p>The practicing of direct push techniques may be controlled by various government regulations governing subsurface explorations. Certification or licensing regulations, or both, may in some cases be considered in establishing performance criteria. For additional information see (<span class="bold">4-15)</span></p><p id="s00002">1.1 This practice covers the method for delineating the subsurface presence of petroleum hydrocarbons and other hydrocarbons using a fiber optic based nitrogen laser-induced fluorescence sensor system.</p> <p id="s00003">1.2 The petroleum hydrocarbon sensing scheme utilizes a fluorescence technique in which a nitrogen laser emits pulsed ultraviolet light. The laser, mounted on the cone penetrometer platform, is linked via fiber optic cables to a window moun......