Estimating initial contaminant mass based on fitting mass-depletion functions to contaminant mass discharge data:...

Area of Science:

• Environmental Science
• Geotechnical Engineering
• Risk Assessment

Background:

• Accurate estimation of contaminant mass in source zones is crucial for site risk assessment and remediation.
• Initial contaminant mass is often unknown and difficult to determine precisely.
• Soil vapor extraction (SVE) is a common remediation technique for contaminated sites.

Purpose of the Study:

• To evaluate the effectiveness of fitting mass-depletion functions to temporal contaminant mass discharge (CMD) data for estimating initial contaminant mass.
• To assess the impact of using early-time data versus full data sets on the accuracy of initial mass estimation.
• To determine the suitability of this method for planning and evaluating remediation efforts.

Main Methods:

• Applied exponential and power mass-depletion functions to historical SVE CMD data from 11 contaminated sites.
• Analyzed both the entire data set and the initial one-third of the data for each site.
• Conducted a differential-time analysis to investigate the performance with limited data.

Main Results:

• Mass estimates using full data sets showed reasonable agreement with total masses removed (13-15% mean error).
• Using early-time data yielded a 17% mean error for the exponential function but a significantly higher 51% error for the power function.
• The method demonstrates potential for providing useful initial mass estimates, especially when applied to the full dataset.

Conclusions:

• Fitting mass-depletion functions to CMD data is a viable approach for estimating initial contaminant mass.
• The method provides reasonable estimates, particularly when applied to comprehensive datasets.
• This technique can support informed decision-making in contaminated site management and remediation.