Raman spectroscopic and microscopic monitoring of on-site and in-situ remediation dynamics in petroleum contaminated soil and groundwater

The mechanistic study of soil and groundwater remediation in petroleum contaminated lands significantly de-mands rapid qualitative and quantitative identification of petroleum substances. However, most traditional detection methods cannot provide the on-site or in-situ information of petroleum compositions and contents simultaneously even with multi-spot sampling and complex sample preparation. In this work, we developed a strategy for the on-site detection of petroleum compositions and in-situ monitoring of petroleum contents in soil and groundwater using dual-excitation Raman spectroscopy and microscopy. The detection time was 0.5 h for the Extraction-Raman spectroscopy method and one minute for the Fiber-Raman spectroscopy method. The limit of detection was 94 ppm for the soil samples and 0.46 ppm for the groundwater samples. Meanwhile, the pe-troleum changes at the soil-groundwater interface were successfully observed by Raman microscopy during the in-situ chemical oxidation remediation processes. The results revealed that hydrogen peroxide oxidation released petroleum from the interior to the surface of soil particles and then to groundwater during the remediation process, while persulfate oxidation only degraded petroleum on the soil surface and in groundwater. This Raman spectroscopic and microscopic method can shed light on the petroleum degradation mechanism in contaminated lands, and facilitate the selection of suitable soil and groundwater remediation plans.

Automated summary

The mechanistic study of soil and groundwater remediation in petroleum contaminated lands requires rapid qualitative and quantitative identification of petroleum substances. In this study, a strategy using dual-excitation Raman spectroscopy and microscopy was developed for on-site detection and in-situ monitoring of petroleum compositions and contents in soil and groundwater. The method provided detection times of 0.5 hours and one minute, and detection limits of 94 ppm and 0.46 ppm for soil and groundwater samples, respectively. Raman microscopy revealed the petroleum changes at the soil-groundwater interface during the remediation processes. This method can shed light on the petroleum degradation mechanism and facilitate the selection of suitable remediation plans.