POM Pulses: Characterizing the physical and chemical properties of particulate organic matter (POM) mobilized by large storm events and its influence on receiving fluvial systems

Monday, 23 January 2017
Ballroom II (San Juan Marriott)
Erin R Johnson1, Shreeram P Inamdar2, Jinjun Kan3 and Rodrigo Vargas2, (1)University of Delaware, Water Science and Policy, Newark, DE, United States, (2)University of Delaware, Newark, DE, United States, (3)Stroud Water Research Center, Avondale, PA, United States
Abstract:
Extreme storm events have tremendous erosive energy which is capable of mobilizing vast amounts of material from watershed sources into fluvial systems. This complex mixture of sediment and particulate organic matter (POM) is a nutrient source that could impact downstream water quality. The impact of POM on receiving aquatic systems is not only driven by the amount mobilized but also by the quality of organic matter contributed by the different POM sources. This study will investigate the composition of POM sources and within-event POM by: (1) determining the amount and quality (fluorescent properties) of dissolved organic matter (DOM) that can be leached from the material; (2) assessing the C and N content of solid state POM and its isotopic character (13C and 15N); and (3) coupling the physical (e.g., particle size) and chemical properties of the material to evaluate storm event POM influence on stream water.

Storm event POM samples and source sediments were collected from a forested headwater catchment (second order stream) in the Piedmont region of Maryland. Stream water extractions were performed for three particle class sizes and bulk source material and the resulting fluorescent organic matter was analyzed. Carbon (C) and Nitrogen (N) amount, C:N ratio, and isotopic analysis of 13C and 15N were performed on solid state event and source material. Future work will include an examination of microbial communities associated with POM.

Large storm events in this watershed transport different proportions of each POM source; dominant among them are the forest floor litter layer, wetlands, and stream bed material. Potentially most influential, the forest floor litter: (1) leaches the most C and N into the surrounding water, (2) contributes the highest percent protein-like fluorescence, an indicator of bioavailability, and (3) has significantly higher C and N in its solid state than all other sources. A high contribution from this or similar sources containing large stores of C, N, and bioavailable components could contribute a disproportionate amount of nutrients to receiving waterways as a result of extreme storm events.

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