Date of Award

Winter 2021

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

Thomas P Ballestero

Second Advisor

James Houle

Third Advisor

Alison Watts

Abstract

Recent studies have found that wetland ecosystems such as mangrove forests, tidal salt marshes, and seagrass beds serve as substantial carbon sinks. Carbon stored in the terrestrial environment rather than in the atmosphere has significant climate implications. Stormwater bioretention systems are intended to hydrologically manage urban runoff as well as reduce pollutant loading to receiving waters. In addition, bioretention systems may represent a significant sink of carbon. This secondary ecosystem service could be used as carbon credits to offset the global increase in carbon emissions. Soil samples were taken at varying depths and locations at 8 salt marsh and 21 stormwater bioretention sites. The samples were then subjected to the loss on ignition (LOI) ASTM test D2974-87. It was found that the top 0-10cm of bioretention soil has statistically similar carbon content to salt marsh soils at the same depth. It was also found that geographic site location may influence carbon content as well as carbon accumulation. Despite the magnitude difference in carbon content between bioretention sites, these constructed systems followed similar patterns with carbon content compared with depth. The upper soil layers of these systems have greater carbon content than the deeper layers. These findings indicate that carbon storage and accumulation differ across bioretention sites, but the top layers of these systems store carbon at a level comparable to natural salt marshes. This secondary benefit of these systems may make them more attractive in a more climate-conscious environment.

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