Characterization and Monitoring Technology Descriptions for Cleaning Up Contaminated Sites
Below are descriptions of technologies used to characterize and/or monitor a site before, during or after remediation work.
Fiber Optic Chemical Sensors (FOCS) operate by transporting light by wavelength or intensity to provide information about analytes in the environment surrounding the sensor. The environment surrounding a FOCS is usually air or water.
Gas Chromatography (GC) is the most widely used chromatographic technique for environmental analyses, and is used onsite in field investigations and by offsite reference laboratories. Chromatography uses a diverse group of methods to separate closely related components of complex mixtures. Field GC can provide real-time, or near real-time data, facilitating decision making and reducing the length of field mobilization.
High-Resolution Site Characterization (HRSC) strategies and techniques use scale-appropriate measurement and sample density to define contaminant distributions, and the physical context in which they reside, with greater certainty, supporting faster and more effective site cleanup.
Immunoassay technologies use antibodies to identify and quantify organic compounds and a limited number of metallic analytes. The technology is used widely for environmental field analysis because the antibodies can be highly specific to the target compound or group of compounds, and immunoassay kits are relatively quick and simple to use.
Infrared Spectroscopy has been an established benchtop laboratory analytical technique for many years. It identifies and quantitates compounds through the use of their infrared absorption spectra. Another use of the infrared spectra is found with video cameras that use infrared absorption to image the absorbing compounds on a video tape.
Laser-induced Fluorescence is a method for real-time, in situ field screening of residual and non-aqueous phase hydrocarbons in undisturbed vadose, capillary fringe and saturated subsurface soils and groundwater. The technology is intended to provide highly detailed, qualitative to semiquantitative information about the distribution of subsurface petroleum contamination containing polycyclic aromatic hydrocarbons (PAHs).
Mass discharge and flux estimates quantify source or plume strength at a given time and location. Consideration of the strength of a source or solute plume improves evaluation of natural attenuation and assessment of risks posed by contamination to downgradient receptors, such as supply wells or surface water bodies.
Mass Spectrometry is an established analytical technique that identifies organic compounds by measuring the mass of the compound's molecule. Although mass spectrometry can be used for the analysis of metals, non-metallic elements and radionuclides, it is most generally used for organic analysis as a field analytical technique.
Test Kits are self-contained analytical kits that generally use a chemical reaction that produces color to identify contaminants, both qualitatively and quantitatively. Numerous different kits are used in the environmental field. Test kits also can be used after an initial site characterization phase to monitor the conditions of a remediation system or to confirm that contaminated soils have been removed.
X-Ray Fluorescence instruments are field-portable or handheld devices for simultaneously measuring metals and other elements in various media. The handheld or field-portable units use techniques that have been developed for analysis of numerous environmental contaminants in soil and sediment. They provide data in the field that can be used to identify and characterize contaminated sites and guide remedial work, among other applications.
Direct-Push Platforms use hydraulic pressure to advance sampling devices and geotechnical and analytical sensors into the subsurface. There are two sampling modes. One uses a specific tool string that either performs downhole measurements or gathers a soil or water sample at a specific depth. In the other mode, a dual tube arrangement is used to take continuous soil samples for evaluation at the surface.
Direct-Push Geotechnical Sensors can provide information about the physical properties of the subsurface environment, for example, density, competence and thickness of layers of soil or sediment. Sensors can provide information about stratigraphy, estimate depth to groundwater or approximate hydraulic conductivity.
The relatively low cost of Direct-Push Groundwater Samplers allows the collection of a larger number of samples both horizontally and vertically than could be done using conventional rigs. This density of sample taking provides a better idea of source zone locations and contaminant plume architecture, which maximizes monitoring well placement efficiency and remedy design.
Direct-Push Membrane Interface Probes are semi-quantitative, field-screening devices that can detect volatile organic compounds (VOCs) in soil and sediment. They are used in conjunction with a direct-push platform to collect samples of vaporized compounds.
Direct-Push Soil and Soil-Gas Samplers have been developed to collect samples of unconsolidated material and vadose-zone gases from a range of depths, without generating large volumes of cuttings. Soil-gas sampling systems analyze vadose-zone gases at the surface or permit real-time chemical monitoring of soil gases in conjunction with direct-push analytical sensors.
Explosives behave differently than most other organic contaminants and pose an immediate safety hazard when present in large quantities or within unexploded ordnance (UXO). Energetic materials include chemicals that are used by the military as propellants, explosives and pyrotechnics. To assess the extent of explosive contamination, it is necessary to detect and identify explosives and their degradation products in soil and groundwater.
Ground Penetrating Radar (GPR) is a geophysical method that has been developed for shallow, high-resolution, subsurface investigations of the earth. GPR uses high frequency pulsed electromagnetic waves to acquire subsurface information. As with most geophysical techniques, the results should be compared with direct physical evidence.
Magnetics for Environmental Applications are used to locate subsurface iron, nickel, cobalt and their alloys which are typically referred to as ferrous materials. The technology has been widely used for quickly locating buried or subsurface cultural ferrous objects that could pose a potential threat to the environment or by assisting remediation efforts.
Open Path Technologies: Ultra Violet-Differential Optical Absorption Spectroscopy (UV-DOAS) uses the unique absorption of specific electromagnetic energy wave lengths by chemicals in the ultra violet, visible and near infrared spectrum to identify and quantify individual chemicals.
Open Path Technologies: Open Path Fourier Transform Infrared (OP-FTIR) spectroscopy is a versatile technology that can measure the presence of many chemicals in air simultaneously and achieve relatively low detection limits. FTIR open path measurements can be made using an active or passive approach.
Open Path Technologies: LIDAR operates on the same principles as radar except that it uses light rather than radio waves to collect information. There are three generic types of LIDAR:
- Range finders are used to determine the distance to a solid or hard target.
- Differential absorption LIDAR (DIAL) is used to measure chemical concentrations in the atmosphere (open air).
- Doppler LIDAR is used to measure the velocity of a moving target.
Open Path Technologies: Raman Spectroscopy sensors can identify chemicals, and provide an average concentration over the distance measured or at specified distances when a lidar configuration is used. The instrument uses an intense monochromatic light source and detectors to measure a portion of the light that is scattered inelastically from the analyte molecule.
Open Path Technologies: Tunable Diode Lasers (TDLs) are designed to focus on single absorption wavelengths specific to a compound of concern in the gaseous form. They are capable of achieving low detection limits and are virtually interferent-free. Open path TDLs are used in atmospheric pollutant studies, fenceline monitoring, process line/tank leak detection, industrial gas-purity applications and monitoring and control of combustion processes.
Passive (no purge) Samplers use methods based on the free flow of contaminant molecules from the sampled media to a receiving phase in a sampling device. Depending upon the sampler, the receiving phase can be a solvent, chemical reagent or porous adsorbent. They are deployed down a well to the desired depth within the screened interval or open borehole to obtain a discrete sample without using pumping or a purging technique.