Formatted Title
High-Resolution Investigation of a Mercury-Impacted Site with the Use of a Field Laboratory
Background/Objectives
According to the 2002 report from the Brazilian Association of Chlor-Alkali and Derivatives Industry (ABICLOR), the chlor-alkali industries report losses of 15.25 g of mercury (Hg) for every ton of chlorine produced, along with an atmospheric loss of 3.22 g of Hg for every ton of chlorine produced. When considering the maximum capacity of the chlor-alkali plant, which is the focus of this study, it is conceivable that there may have been a loss of up to 8,000 tons of mercury over slightly more than 40 years of production at the plant.
During Phase I, conducted at the site, 11 contaminated areas, nine areas with suspected contamination, and 32 areas with potential contamination were identified. Subsequently, a Phase II work plan was developed based on the Phase I findings.
Approach/Activities
One of the primary objectives of the Phase II investigation was to evaluate the presence of mercury in both surface and subsurface soil by comparing the analytical results with the standards set by the relevant environmental authority. The study also aimed to collect data for characterizing the physical environment.
The Phase II investigation employed an innovative environmental diagnostic optimization methodology, named "Optimizing Investigation by Applying On-Site Analyses" (OITSC). This methodology involved conducting on-site analyses using various equipment to expedite analytical results (within 1 to 2 days), enabling real-time decision-making. This approach effectively reduced laboratory analytical costs by operating on a daily cost basis for on-site laboratory operations, encouraging the collection of comprehensive data for immediate decisions, as opposed to a per-sample cost basis, which often limits data availability.
Advanced contamination characterization techniques were employed, including the utilization of a surface plasmon resonance (LPR)-based mercury vapor monitor and an X-ray fluorescence (XRF) detector, which enhanced the accuracy and efficiency of the assessment.
Results/Lessons Learned
A total of 339 reconnaissance boreholes were executed for soil sample collection and detailed lithological descriptions of the drilled soil. In total, 2,786 soil samples were processed to quantify Hg concentrations using the XRF analyzer. The use of the field laboratory allowed for the immediate identification and resolution of data gaps and conflicts, eliminating the need to wait for extended laboratory results. This approach prevented delays and disruptions in fieldwork and facilitated the updating of the site's conceptual model, ultimately enhancing the efficiency of future soil excavation activities.