Lori Wrye


B.Sc. (Honours) Thesis

Suspended Sediment Concentrations and Disaggregated Inorganic Grain Sizes (DIGS) Analysis of Lake Charles and Lake Micmac Dartmouth, Nova Scotia

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Power Point Presentation

In the of fall 2005, a study in Dartmouth, Nova Scotia was performed on the concentration and grain size distribution of suspended particulate mass (SPM) that entered Lake Charles, the Shubenacadie Canal Park and Lake Micmac, during heavy rainfall events. The study area had a history of increased SPM concentrations due to urban development since the early 1970's. New constructions began in the spring and summer of 2005, west of the study site and public concern was raised as the sites were not required to perform provincial or federal environmental impact assessments. Spring storms provided an indication that SPM should be considered a significant problem, however, it was not resolved. In the fall of 2005 large rainfall events, again resulted in SPM entering the lakes system. Weekly sampling was carried out to determine background concentrations in the region, and event sampling was performed during heavy rainfalls. One example of a large rainfall event during the October 7th-10th weekend when Dartmouth received over 150 mm of rain. Sampled water was highly discoloured and the resulting SPM concentrations ranging between 0.2-100 mg L-1. During the peak of the Thanksgiving Storm SPM concentrations exceeded water quality guidelines set by the Canadian Counsel of Resource and Environment Ministers. SPM concentrations were in the higher range in the northern Canal and Grassy Brook. Measurements of the sediment grain size entering the lakes, using the Coulter Multisizer IIe showed that the sediments were clay/silt sized (ranging from 10 to less than 63 μm). Storm samples and background samples showed different DIGS distributions indicating the source of sediment were not the same. After the Thanksgiving Storm, SPM concentrations were reduced as the methods of water retention at both construction sites were improved. After the initial Thanksgiving SPM overflow, the concentrations of sediments entering the lake system during subsequent rainfall events were reduced.

Pages: 124
Supervisor: Paul Hill (Oceanography)