| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 100 === In Taiwan most of gas stations have been used for more than 10 years, and may cause the oil contamination in soil and groundwater due to pipelines corrosion of storage tanks, changes in land subsidence, operation of mismanagement or other reasons. According to the reports, the petroleum hydrocarbons are the main pollutions of oil contamination being identified.
The preliminary method of detection of the oil contamination is to use the on-site carrier-detector, and its benefits are to reduce the time and cost of operation. However, the traditional analysis of BTEX (benzene, toluene, ethyl benzene, and xylene) and TPH were required to bring back to the laboratory after sampling, and its drawbacks include time-consuming, expensive, and analytical techniques of high technical threshold. The purpose of this study is to investigate differences in analysis of concentrations between the rapid-screen detection on site and traditional analysis in laboratory in order to understand whether further sampling and analysis in laboratory after the rapid-screen detection on site.
In this study, the detection values on site were detected by using photoionization detector (PID) and flame ionization detector (FID), and were compared with the laboratory method of BTEX. Samples collected from 39 gas stations (112 points) were analyzed in this study. Results indicated a PID value of 1000 ppm could fairly represent possible BTEX contamination on site. Meanwhile, when the PID value was close to 1500 ppm, possible benzene violation of control standard could be identified. Furthermore, when PID value was closed to 3500 ppm, and the TPH may have a 50 % possibility to violate the control standards. On the other hand, when FID measurement was below 5000 ppm, BTEX concentrations were found to below control standards. However, when FID at the concentration of 5000 to 150000ppm, there is still a 10 % possibility that no BTEX could be measured in the lab. Subsequently, Based on these findings, we suggest that a on-site FID value of 400ppm should be used as indication of further sampling for detailed lab analysis on TPH. Also, when relatively high or low FID values were identified on site, significant differences between FID values and lab TPH measurements could be found. Even though measurements conducted in this study could be affected by soil properties, moisture, content of organics etc, results from this study indicated that the FID method is not sensitive to detect BTEX, and PID method is more sensitive and representative.
|
|---|
