HOW EFFECTIVE ARE NATURAL RIPARIAN BUFFERS AT FILTERING SEDIMENTS AND CONTAMINANTS FROM AGRICULTURAL FIELDS?
Due to the continued decline of water quality in the Chesapeake Bay and its major tributaries, we hypothesize that the standard 100’ forested riparian buffer is failing to completely trap sediments and contaminants derived from agricultural lands in Virginia. This study aims to quantify sediment, nitrogen, and phosphorous transport through riparian systems buffering tributaries to the lower James and York Rivers from agricultural fields. We analyze shallow and deep hydrologic transport pathways, by measuring sediment at the surface and dissolved nutrients in groundwater. In order to gauge the amount of sediment transport along hillslope transects, 137Cs is used as a tracer to quantify sediment loss and storage. Transects have two lateral sampling points in the O-Horizon, upper mineral soil, and lower mineral soil; care was taken to establish continuity between transects with a sampling point in the agricultural field, at the entrance to the riparian buffer, multiple points through the buffer, and at one meter from the stream. Multiple transects were taken from agricultural fields, and from control sites that have limited anthropogenic impacts. Control sites in preserved areas are used to determine the base level of 137Cs present in coastal plain soils, and to account for natural nutrient and sediment transport that occurs on forested hillslopes.