Mass flux: The key to smarter PFAS site management

Organizations continue to be under pressure to manage environmental liabilities associated with PFAS. Traditionally, success was measured by whether contaminant concentrations met compliance standards, but PFAS presents a particular challenge when it comes to organic contaminants. Our team has observed that a little PFAS in soil can go a long way in water. This results in the traditional success measure not providing a pragmatic basis for success in a field of evolving science, engineering, risk assessment and evolving compliance concentration targets. The key to smarter, more defensible decisions lies not just in measuring contamination, but in understanding how much and where the PFAS moves. That is where mass flux comes in. 

Mass flux is a measure of how much contaminant mass moves through a unit area of subsurface over time, typically expressed in grams per square meter or square foot per day. Unlike concentration alone, mass flux captures both the amount and the rate at which contaminants travel, revealing the true dynamics of subsurface transport. 

Why is this important? Because concentration data alone can be misleading, especially in layered soils where hydraulic conductivity varies. Two zones with identical contaminant concentrations may pose very different risks if one allows water and contaminants to move more freely. Mass flux highlights these nuances, helping practitioners prioritize remediation, design effective monitoring strategies and communicate risk more clearly to stakeholders. 

For PFAS, mass flux is especially valuable. PFAS is persistent, resistant to breakdown and subject to evolving regulatory standards. Mass-based approaches provide a stable platform for assessing remediation success, even as concentration criteria shift.

By shifting the focus from contaminant concentrations to understanding the amount and movement of PFAS, mass flux enables targeted risk reduction, supports transparent communication with stakeholders and aligns environmental performance with business objectives. The following benefits illustrate how mass flux assessment can drive smarter interventions, build community trust and deliver commercial value. 

Reducing risk by identifying high-impact zones 
Mass flux measures the amount of contaminant moving through a specific area over time. Unlike concentration alone, mass flux reveals which zones and pathways are contributing most to contaminant movement. This allows organizations to pinpoint high-impact areas for intervention, focusing resources where they will make the greatest difference. By targeting remediation efforts based on mass flux data, risk to human health and the environment can be reduced more efficiently and effectively. 

Supporting community knowledge through transparent, data-driven storytelling 
Mass flux provides a clear, quantitative picture of how contaminants travel through a site. This transparency supports better communication with regulators, stakeholders and the community. Instead of relying on complex concentration maps, organizations can use mass flux data to tell a straightforward story: where the PFAS is coming from, how much is moving and what is being done to address it. This data-driven approach builds trust and supports informed decision-making, helping communities understand both the challenges and the progress being made. 

Driving commercial success by aligning environmental performance with business goals 

Integrating mass flux into your conceptual site model and remediation plans isn’t just good science, it’s good business. By focusing on the zones that matter most, organizations can optimize remediation budgets and demonstrate measurable progress toward regulatory compliance. Mass flux metrics provide a stable basis for tracking performance, even as regulatory targets evolve. This alignment between environmental outcomes and business objectives helps organizations manage liabilities, protect reputation and achieve commercial success.

Mass flux is more than a technical calculation, it’s a strategic tool for risk reduction, liability management, transparent communication and commercial performance. By integrating mass flux into site models and remediation plans, organizations can make smarter, more defensible decisions in managing PFAS and other persistent contaminants.

As part of our Navigating PFAS webinar series, we sat down to talk about mass flux and how to unlock the power of mass flux assessments. For more insight on mass flux including real-life examples and a more technical approach to the topic, you can watch this webinar on-demand.