PNNL

Abstract

ABSTRACT: An automated groundwater monitoring system for the detection of uranyl ion in groundwater was deployed at the 300 Area Industrial Complex, Hanford Site, Washington. The research was conducted to determine if at-site, automated monitoring of contaminant movement in the subsurface is a viable alternative to the baseline manual sampling and analytical laboratory assay methods currently employed. The monitoring system used Arsenazo III, a colorimetric chelating compound, for the detection of the uranyl ion. The analytical system had a limit of quantification of approximately 10 parts per billion (ppb, µg/L). The EPA’s drinking water maximum contaminant level (MCL) is 30 ppb[1]. In addition to the uranyl ion assay, the system was capable of acquiring temperature, conductivity, and river level data. The system was fully automated and could be operated remotely. The system was capable of collecting water samples from four sampling sources, quantifying the uranyl ion, and periodically performing a calibration of the analytical cell. The system communications were accomplished by way of cellular data link with the information transmitted through the internet. Four sampling locations were selected for the investigation: one location sampled Columbia River water, and the remaining three sampling locations were from aquifer tubes in a vertical array, penetrating into the Columbia River bed near the shore. The typical sampling schedule was to sample the four locations twice per day with one calibration check per day. This paper outlines the instrumentation employed, the operation of the instrumentation and analytical results for a period of time between July and August, 2012. We will present the uranyl ion concentration and conductivity results of the automated sampling/analysis system, and will present a comparison between the automated monitor’s analytical performance and an independent laboratory analysis. The application of the instrumentation may have two primary benefits: • Replacement of the current manual sampling and analysis protocols that are labor intensive and expensive • The reduced cost of acquiring samples will allow for more frequent collection of samples that may be automatically introduced into real-time graphical flux programs allowing site managers to observe the changes in contaminant concentrations during remediation projects and across discrete river stage events.