Study of high-resolution site characterization technologies for the improvement of the conceptual site model — case study: Duque de Caxias (RJ), Brazil

ABSTRACT

This paper presents the results of two high-resolution site characterization (HRSC) techniques: passive investigation of soil vapors and investigation using Membrane Interface Probe (MIP), in an area contaminated by petroleum hydrocarbon, located in the municipality of Duque de Caxias, Rio de Janeiro. The environmental management process in the area began in 2012 and contemplated the stages recommended by the current legislation. The results obtained from the traditional investigations were insufficient for the understanding of the physical and geochemical aspects for the success of the diagnostic phases and, consequently, the remediation phase. Therefore, it was conducted two high-resolution investigations with the objective of improving the conceptual model in order to comply adequately with CONAMA Resolution 420/09 and CONEMA Resolution 44/12, allowing future actions more efficient. The soil gas passive investigation used samplers composed of granular adsorbent materials, encapsulated in a hydrophobic and chemically inert microporous membrane that allows the diffusion of the vapors present in the media. The results qualitatively represent the presence of contamination in the subsoil. MIP is a direct push tool with real-time measurement, which detect the presence of contamination in both unsaturated and saturated media. From the integrated results, it was possible to verify that the distribution of volatile organic compounds (VOCs) in groundwater occurs in a discontinuous way throughout the area. It was possible to identify five distinct hotspots and their different source areas, including a region with the presence of free-phase.

Keywords:
high-resolution site characterization; contaminated areas; petroleum hydrocarbons; conceptual site model