Agricultural Tile Drainage and PFAS Transport
Subsurface tile drainage systems—perforated pipes buried beneath agricultural fields to remove excess soil moisture—can intercept PFAS-contaminated groundwater or accelerate transport of PFAS from biosolid-amended soils to surface water. Tile drain water quality is increasingly recognized as a significant pathway for PFAS contamination of streams and rivers in agricultural regions.
PFAS in Biosolid-Amended Soil Tile Drainage
Fields receiving municipal biosolid applications accumulate PFAS in the soil profile. Subsequent rainfall events mobilize dissolved PFAS downward through the soil column, where tile drains intercept subsurface flow before it reaches natural groundwater. Tile drain monitoring in biosolid-amended fields shows PFAS concentrations substantially higher than background agricultural areas, confirming tile drainage as an active PFAS transport pathway.
Implications for Surface Water Quality
Tile drains discharge to surface ditches, streams, and rivers used as drinking water sources. PFAS transport via tile drainage contributes to surface water contamination that ultimately reaches water intake facilities. This pathway represents a relatively diffuse, persistent contamination source compared to point-source industrial discharges, making source control and treatment approaches different from conventional contamination scenarios.
Monitoring and Management
Watershed managers and water utilities in agricultural regions should incorporate tile drain PFAS monitoring in source water assessment programs. Cover crop systems and reduced-tillage practices that promote deeper soil infiltration may reduce tile drain PFAS transport. Targeted biosolid application restrictions in watersheds feeding drinking water intakes can reduce ongoing PFAS loading via this pathway