Water Resources Research Act Program

Details for Project ID 2011VT57B

Determining phosphorus release potential from eroding streambank sediments in the Lake Champlain Basin of Vermont

Institute: Vermont
Year Established: 2011 Start Date: 2011-03-01 End Date: 2012-02-28
Total Federal Funds: $19,989 Total Non-Federal Funds: $50,116

Principal Investigators: Donald Ross, Leslie Morrissey, Beverley Wemple

Abstract: Streambank erosion is a significant contributor of sediment and sediment-bound phosphorus (P) into Champlain Valley riverways and Lake Champlain, lowering water quality. Sediment and P load studies usually measure only total P (TP) and occasionally readily available P, such as Modified Morgan P (MM-P), yet neither concentration reflects the amount of P that will be released from sediments over time. Available P tests reflect the fraction of P immediately bioavailable while TP includes occluded P that will likely never be released. Oxalate-extractable P (Pox) has been shown to be more representative of P that is released over time in aquatic systems, measuring immediately available P as well as P complexed with Al and Fe oxides. In reduced environments such as lake sediments, Fe oxides readily release P that can be cycled into the water column. Recent work in the Lake Champlain Basin has shown that Pox/TP ratios were strongly correlated with soil texture and therefore bioavailable P may be modeled throughout riparian landscapes using textural analysis only. The objectives of this project are to: 1) quantify the slow-cycling P contribution (Pox) from eroding streambank sediments into Lake Champlain; 2) further develop the relationships among Pox, total P and soil texture; and 3) model TP, MM-P and Pox variation in the riparian landscape. To meet these objectives, 400 archived soil samples representative of study extent, texture, and drainage (stratified random sample) will be analyzed for Pox. These samples were collected as part of two past studies and an ongoing study and will have been analyzed for MM-P, TP, and texture. Soils were collected in the Basin along the corridors of seven streams in three Vermont counties. A strong correlation between Pox/TP and texture would support previous research, allowing bioavailable P to be predicted by texture throughout riparian corridors in the region and to be modeled spatially. The proposed research would allow for calculation of potentially bioavailable P loading rates in addition to the total P load. This would in turn inform better riparian corridor and aquatic system management by more clearly identifying actual sources of bioavailable P to the Lake.