Fiber optic/cone penetrometer system for subsurface heavy metal detection

摘要

Science and Engineering Associates (SEA) developed a prototype subsurface soil211u001echaracterization tool for the evaluation of heavy metals. The system, based on 211u001eLaser-Induced Breakdown Spectroscopy (LIBS), is deployed using a cone 211u001epenetrometer. The LIBS system consists of a laser source to produce the plasma, a 211u001enovel hollow waveguide method of delivering the laser source to the subsurface, a 211u001esmall penetrometer probe for focusing the laser light to create a spark and 211u001ereturn the light emission for analysis, a spectrometer to spectrally resolve the 211u001eemission spectrum, an array detector for simultaneous measurements of emission 211u001eintensities over a range of wavelengths and a computer to conduct equipment 211u001econtrol, data acquisition, and data analysis. Under this two phase effort, the 211u001esystem was designed, fabricated and tested, culminating in a successful field 211u001edemonstration at the DOE Sandia Chemical Waste Landfill for the evaluation of 211u001echromium contamination. During this CPT/LIBS test, six penetrations were 211u001econducted and the data obtained with the system was used to generate graphs 211u001edepicting the concentration of chromium as a function of depth to approximately 211u001e15 feet, with a range of concentrations from background (approx. 30 ppm) to about 211u001e1200 ppm. In addition, prototype LIBS instruments, developed by DOE LANL 211u001epersonnel, were successfully field deployed by SEA at a Formerly Utilized 211u001eRemedial Action Plan (FUSRAP) site for the detection of beryllium. This 6 week 211u001efield effort generated a high density surface contour plot of the beryllium 211u001econcentration over a 40 acre site. Utilizing both van-mounted and backpack 211u001esystems, SEA evaluated 1664 samples at the site. This was the first full scale 211u001efield deployment of the portable LIBS instruments and the beryllium concentration 211u001edata was used successfully for real-time decision-making during the site 211u001echaracterization and for the development of additional plans for subsurface 211u001eanalysis.