PRD Tech, Inc.
Rakesh Govind
1776 Mentor Avenue
Cincinnati, Ohio, 45212, United States
Description
Determining concentrations of contaminants in ambient air is a challenge especially when there are multiple contaminants, and their concentrations vary with time and location. One such application is determining the release of volatile organics during excavation of contaminated Manufactured Gas Plant (MGP) sites. Currently, there are several thousand MGP sites that need to be excavated in the US to prevent ground water contamination, and most of these sites are located near high population density areas. During excavation of these sites, several volatile organics, typically organics, such as benzene, toluene, xylenes, naphthalenes, thiophenes and several others are emitted into the air resulting in odor complaints and possible hazardous exposures. Determining the concentration of this multi-pollutant release in ambient air during excavation is critical for safeguarding the surrounding population.
Current methods of determining ambient air concentrations are limited to using specialty analyzers, that measure a specific compound, or a detector that gives a quantitative measure of the total compound concentrations, without giving any breakdown of the specific compounds, or taking air samples and sending them to a laboratory for detailed analysis.
In this project, an advanced adsorbent based Sequential Automatic Tube Sampler (SATS) system has been developed, which uses 24 adsorbent tubes with a single sampling pump to adsorb a wide variety of volatile MGP site contaminants. These adsorbent tubes can be stored, transported easily and then analyzed using a thermal desorber coupled to a Gas Chromatograph (GC) or a Gas Chromatograph/Mass Spectrometer (GC/MS) to determine the concentrations of each of the contaminants.
Another application of the SATS system is to determine soil gas concentrations for quantifying in-situ biodegradation rates responsible for natural attenuation of contaminants at MGP sites. Soil-gas technology is most effective in detecting compounds having low molecular weights, high vapor pressures, and low aqueous solubilities. These compounds volatilize readily and diffuse vertically and horizontally through the soil toward zones of lower concentration.
The main advantages of using the SATS system are: (1) Compact system that can be located in the field using the battery; (2) Samples the air for 24 hours or more; (3) Stores sample in adsorbent tube, which can be easily stored indefinitely (once capped) with no loss of sample, unlike canisters or tedlar bags, in which condensation and sample losses can occur; (4) The stored samples in the adsorbent tubes can be transported in compact containers; (5) Thermal desorption allows for greater recovery of the sample from the adsorbent; (6) Use of high surface area adsorbents increases accuracy of the sample analysis, especially when the air concentrations are low; and (7) The system can be applied for monitoring volatile emissions from contaminated sites, soil gas analysis, determining field in-situ biodegradation rates for contaminants for natural attenuation, and in many other applications.