AFTER THE FLOOD: POTENTIAL LEACHING OF CARBON AND NITROGEN FROM SEDIMENTS

Large storm events, such as hurricanes and tropical storms, can erode, transport and subsequently deposit sediments in aquatic systems. In sediments, particulate organic matter (POM), including nutrients such as carbon (C) and nitrogen (N), leaches into the water system following sediment deposition. This organic matter has the potential to alter water quality, the aquatic metabolism of the system, and nutrient cycling. Our study sought to evaluate the POM quantity and quality for sediments in 1-2^nd order streams in a forested watershed located in the Piedmont region of eastern Maryland.

Source sediment samples (21 locations in and around the fluvial network) and bed sediment samples (eight locations along a 1-2^nd order stream) were collected throughout the watershed after a large storm event in July. The dried samples were then sieved into three particle grain sizes of coarse (2mm-1mm), medium (1mm-250µm) and fine (<250µm). Each particle class was extracted using DI water. Extracts were analyzed for concentrations of dissolved organic carbon (DOC) and nitrogen. Organic matter quality was determined using UV and fluorescence techniques.

Labile organic matter (high POM quality) is defined by low C:N ratios, high “protein-like” percentages, and low “humic-like” percentages. Coarse particles and sediment from the forest floor O horizon were found to have the highest POM quantity. POM quality was found to increase with grain size. Therefore, coarse particles had the most organic matter and were the most labile, while fine particles were the most refractory.

This research is vital to our future due to climate change, which may potentially increase the amount of large storms in the northeastern region of the Unites States. This, potentially, could cause an increase in the mobilization and deposition of sediment and intensify alterations of water quality, aquatic metabolism, and nutrient cycling.