UV light device for vertical screening of soil samples contaminated with LNAPL

Abstract

Petroleum hydrocarbons in light nonaqueous-phase liquid (LNAPL) can cause significant contamination when released into the environment. The identification, delineation, and understanding of their interactions with hydrostratigraphic media are essential for geoenvironmental site characterizations. Investigations of LNAPL-contaminated sites in Brazil are mostly conducted using monitoring wells, which have limitations in identifying LNAPL. Site characterization techniques based on ultraviolet light (UV) emissions, which are commercially known as Ultraviolet Optical Screening Tool (UVOST) and Optical Image Profiler (OIP), are more effective in identifying and providing qualitative LNAPL data. A bench testing campaign was conducted to evaluate the performance of an alternative, low-cost UV light device for determining the presence of LNAPL contamination in soil samples. This device creates a dark environment and uses UV light at different wavelengths combined with filters with different colors. Three different soils (e.g., organic, fine-medium sand, and well-sorted medium sand), three petroleum hydrocarbon products (e.g., lubricating oil, gasoline, and diesel) and deionized water were used. A total of 54 bench tests were conducted for hydrocarbon detection to assess the applicability of the alternative, low-cost UV light device. A UV-C light with a red filter produced the best results for identifying soil contamination. It was found that the UV light device is more efficient when using different wavelengths that are associated with more than one color filter. The application of this system has been broadened as it has now become more efficient when used with different combinations of soil types and LNAPL sources.