Many types of man-made activities including combustion of fossil fuel, nonferrous metal fusion, and oil refining have been used to symbolize the grown of industrialization and civilization. In accordance with such development, the size of pollutant em...
Many types of man-made activities including combustion of fossil fuel, nonferrous metal fusion, and oil refining have been used to symbolize the grown of industrialization and civilization. In accordance with such development, the size of pollutant emission has also increased dramatically.
In view of atmospheric and environmental chemistry, reduced sulfur compounds(RSC) which is generally represented by H2S, CH3SH, DMS, DMDS, and others are often treated as key components of malodor issues. In this respect, the analytical techniques for RSC are highly valuable tool to diagnose the pollution status of RSC in a given environment. To learn more about RSC chemistry, we developed an analytical system based on gas chromatography/pulsed flame photometric detector (GC/PFPD) combined with air server/thermal desorber (AS/TD). As the first step of our study, laboratory-based experiments were conducted using gaseous standards of 4 RSCs (H₂S, CH₃SH, DMS, and DMDS). In an effort to develop the reliable measurement techniques for RSC, the recovery rate of thermal desorbing (TD) method was investigated initially in relation to sample concentration and loading volume of standard. In the next stage, the calibration properties of RSC were examined further by changing of sample loading time. In addition, a series of calibration experiments were conducted based on both internal and external calibration approaches.
The results of our laboratory-based study showed that calibration patterns of RSC became less stable, when the small quantities of standard are supplied at short loading time. The results derived at such condition exhibited reduced recovery rate, especially with light RSCs (H₂S and CH₃SH). On the other hand, at sufficiently high loading volume, the quantification of RSC was limited by the breakthrough of cold trap in TD which yields off-scale peaks (at a near 50 ng). The results of our experiments were also examined in terms of standard loading approaches between fixed standard volume (FSV) and fixed standard concentration (FSC) method. As the latter method tends to suffer from sensitivity variations more significantly than FSC, the former is recommended to maintain the consistency in the analysis of RSC. Thus, the optimization of TD based analysis should be considered as a prerequisite for ensuring the reliability of RSC analysis.
Based on the accumulated knowledge of sampling and analysis, this analytical technique for RSC analysis was employed to the different types of environmental samples. As the first step of such application, this technique was applied to measure odorants released during food decay. Based on this experiment, we were able to differentiate RSC emission patterns among Kimchi (KC), Fresh fish (FF), Salted fish (SF). As the next step, emission characteristics of major offensive odorants were also investigated using odor samples collected from two urban stormwater catch basins(SCB) under two types contrasting environmental conditions. According to our analysis, RSCs including CH₃SH, H₂S, and DMS tend to contribute to the highest odor strengths for both types of SCB environments. The overall results of our study suggest that the emissions of major offensive odorants from urban stormwater catch basins can be explained at least partially in relation with human activity.