The fate of particulate nitrogen in fluvial systems
Date
2018
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Large storms can erode, transport, and deposit large amounts of allochthonous
particulate organic matter (POM) and particulate nitrogen (PN) to the fluvial network.
The role of storm-driven POM in the processing of fluvial C and N and its impact on
water quality is still poorly understood. This study investigates the fate of C and N from
storm-driven POM deposition using a 56-day incubation experiment of five known
POM sources from a 79-ha forested watershed. Incubation columns were treated with
one of two moisture treatments; Moisture Regime 1: sediment subjected to frequent
rewetting treatments, Moisture Regime 2: sediments subjected to dry-wet cycles.
Sediment and porewater samples were collected throughout the incubation and analyzed
to characterize and compare the solid and solution pool chemistries and the abundances
of nitrifying and denitrifying microbial populations. Key findings from this study are:
(1) C and N rich sources experienced decomposition, mineralization, and nitrification
and released large amounts of dissolved N, but the amount of N released varied by
POM source and moisture regime. Drying and rewetting stimulated nitrification and
suppressed denitrification in most POM sources. (2) Fluvial Storm Deposits released
large amounts of porewater N regardless of the moisture conditions, indicating that they
can readily act as N sources under a variety of conditions. (3) Forest Floor Humus was
the only POM source to exhibit mineralization and denitrification when frequently
rewetted. Under these conditions, this POM source acted as the strongest source of
dissolved organic nitrogen. Under the drying and rewetting moisture conditions, Forest
Floor Humus became a N source, specifically exhibiting intense
decomposition, mineralization, and nitrification, resulting the release of large amounts
porewater nitrate. The inputs and processing of large storm-driven PN inputs becomes
increasingly more important as the frequency and intensity of these large storms are
predicted to increase due to global climate change. Gaining a better understanding of
the fate of the N derived from particulate materials is critical to the development and
implementation of effective management practices for controlling water pollution and
maintaining healthy waterways.
Description
Keywords
Health and environmental sciences, Earth sciences, Drying and rewetting, Nitrogen leaching, Particulate nitrogen, Particulate organic matter, Storm transport