Seasonal Influence on Phosphorus (P) Sorption Capacities in Streams and Ditches in Eagle Creek Watershed.
Candiss O. Williams, Brad Joern, Doug Smith, Laura Bowling, and Carol Lembi. Agronomy, Purdue University, 915 West State Street, West Lafayette, IN 47906
Internal P loading from sediments to waterbodies may be a significant source of P and may prevent the attainment of surface water nutrient criteria developed by the USEPA. Our objectives were to 1) relate surface water P concentrations to sediment P, 2) determine if differences in land use were related to ditch and stream water P concentrations and sediment P status and 3) determine if seasonal differences were associated with water and sediment P concentrations in the ditches and streams that contribute to a major drinking water reservoir for the city of Indianapolis, IN. Findings showed that there was often a relationship between sorption capacity of the sediment and water column P, but the relationship was not consistent. The potential mass of P that could be sorbed by the sediment before soluble P exceeded the proposed EPA nutrient criteria limit (0.076 mg P/L) was greatest for August samples. Extractable P (20 mM CaCl2) in sediment was consistently below the proposed EPA nutrient criteria for all samples and sampling months. This information is beneficial in quantifying P dynamics in different land use types.