Recently, there has been increased emphasis on combining chemical and flow data into a single metric to provide estimates of contaminant mass flux. This flux is the rate that a contaminant passes through a defined cross section in units of mass per time. The objective of this project was to develop an easy-to-use, free software tool for site personnel to determine the applicability of the mass flux approach and to easily apply it when appropriate. In particular, the software will enable users to compare different mass flux approaches, calculate mass flux from transect data, and apply mass flux to manage groundwater plumes.

Technology Description

The software tool includes a graphical user interface with pull-down menus, selection buttons, navigation buttons, and "help" features. The software, programmed in the Microsoft® Excel spreadsheet environment, provides the following tools to calculate and evaluate mass flux of contaminants in groundwater:

  • Calculation of Mass Flux - a module to calculate the total mass flux across one or more transects of a plume and plot mass flux vs. distance to show the effect of remediation/impact of natural attenuation processes. Three types of uncertainty analysis are included: uncertainty range due to interpolation; uncertainty due to the variability in the input data using a Monte-Carlo like analysis; and an uncertainty analysis that shows how dependent the mass flux estimate is on data from each monitoring point.
  • Impact of Mass Flux - a module allowing users to perform critical dilution calculations for plumes approaching production wells or streams. An additional feature calculates the capture zone of the supply well, directing the user to alter the transect dimensions if the transect does not encompass the capture zone.
  • Learn About Mass Flux - a module that provides a review of theory and methods of estimating mass flux.

Demonstration Results

The Mass Flux Toolkit is an easy-to-use, Microsoft® Excel-based software tool that enables users to calculate mass flux from transect data, apply mass flux values to manage groundwater plumes, and learn about different mass flux approaches. The Toolkit provides three options to analyze uncertainty in the total mass flux estimates derived from the transect method, which is a key issue in using mass flux as a metric. One option analyzes uncertainty in the actual concentration, hydraulic conductivity, and gradient measurements. With this tool, groundwater practitioners can estimate the accuracy of the hydrologic measurements that are being used for the mass flux calculation. The second option provides a tool for estimating the contribution of each individual observation to the total mass flux. The third option shows the uncertainty involved in the interpolation scheme that is used to calculate mass flux.

Implementation Issues

The Mass Flux Toolkit is applicable to any type of dissolved-phase constituent plume, including fuel hydrocarbons, chlorinated solvents, and metals. With this tool, site managers and consultants will be able to perform mass flux calculations more quickly and cheaply, permitting their inclusion in more evaluations of groundwater plumes. With the mass flux data, the progress of natural attenuation and remediation systems can be demonstrated more vividly and directly to regulators, making the remediation process clear, effective, and efficient. (Project Completed - 2006)