Screening-level estimates of mass discharge uncertainty from point measurement methods

Area of Science:

• Environmental Science
• Hydrogeology
• Geochemistry

Background:

• Point-scale measurement techniques introduce uncertainty in mass discharge estimation.
• Accurate mass discharge assessment is crucial for contaminant transport modeling and remediation efforts.

Purpose of the Study:

• To derive analytical solutions for the coefficient of variation in mass discharge measurements.
• To investigate the uncertainty of mass discharge measurements using conceptual models.
• To develop methods for evaluating uncertainty based on sampling network design.

Main Methods:

• Developed two simplified conceptual models for groundwater flow and contaminant flux.
• Assumed depth-averaged flow and normal or bivariate normal contaminant flux distributions.
• Analyzed uncertainty as a function of control plane length, number of wells, and sample spacing.
• Introduced a dimensionless parameter Ω (ratio of maximum local flux to mass discharge and sample density).

Main Results:

• Derived simplified equations for uncertainty to aid screening-level evaluations.
• Expressed uncertainty in relation to sampling network parameters (e.g., control plane length, number of wells, sample spacing).
• Demonstrated the relationship between uncertainty, contaminant 'hot spots', mass discharge magnitude, distribution, and sampling density via parameter Ω.

Conclusions:

• The study provides analytical tools to quantify uncertainty in mass discharge measurements.
• Parameter Ω offers a practical way to link measurement uncertainty to site-specific conditions and sampling strategies.
• Findings facilitate optimized sampling network design for more reliable contaminant assessments.