GEOL Thesis Defense - William SchroerFriday, July 7, 2017 - 10:00am
Drivers of sediment accumulation and nutrient burial in residential stormwater detention ponds
Stormwater detention ponds are widely utilized as control structures to manage runoff waters during storm events. These sediments also represent significant sites of organic carbon and nutrient burial. Here, carbon (C) and nutrient sources and burial rates are determined in 14 residential stormwater detention ponds throughout coastal counties of South Carolina. Bulk sediment accumulation is directly correlated with catchment impervious surface coverage (R2 = 0.90). However rates of sediment accumulation are lower than expected and range from 0.06 to 0.50 cm y-1, indicating that required maintenance dredging could be reassessed. Strong, positive correlations between the Terrestrial Aquatic Ratio biomarker index and sediment accumulation rate (R2 = 0.77), in conjunction with high C:N ratios (16 – 33), suggests that terrestrial biomass drives this sediment accumulation. Our results further argue that high rates of preferential remineralization of algal derived biomass occur prior to burial in sediments. Carbon and nutrient concentrations were relatively stable between ponds and burial rates were driven by rates of bulk sediment accumulation. Rates of carbon and nutrient burial (C: 0.7 – 13 mol m-2 y-1, N: 0. 5 – 0.46 mol m-2 y-1, P: 0.008 – 0.133 mol m-2 y-1) are similar to those observed in natural lake systems, but generally less than those observed in reservoirs or impoundments. Though individual ponds are small in area (930 – 41,000 m2), they are regionally abundant and could therefore represent a significant if understudied sink in global nutrient cycles.