The effects of nutrient additions on the sedimentation of surface water contaminants in a uranium mined pit-lake

Description

<p><p>I investigated the usefulness of phytoplankton for the removal of surface water
contaminants. Three experiments, consisting of nine large mesocosms (92.2 m³) were
suspended in the flooded DJX uranium pit at Cluff Lake (Saskatchewan, Canada), and
filled with contaminated mine water. During the summer of 2003, each mesocosm was
fertilized with a different amount of phosphorus throughout the 35 day experiment to
stimulate phytoplankton growth, and to create a range in phosphorus load (g) to examine
how contaminants may be affected by different nutrient regimes. Algal growth was
rapid in fertilized mesocosms as demonstrated by chlorophyll a profiles. As phosphorus
loads increased there were significant declines in the surface water concentrations of As,
Co, Cu, Mn, Ni, and Zn. This decline was near significant for uranium. The surface
water concentrations of Ra²²⁶, Mo, and Se showed no relationship to phosphorus load.
Contaminant concentrations in sediment traps suspended at the bottom of each
mesocosm generally showed the opposite trend to that observed in the surface water,
with most contaminants (As, Co, Cu, Mn, Ni, Ra²²⁶, U, and Zn) exhibiting a significant positive relationship (<i>P</i> < 0.05) with phosphorus load. Sediment trap concentration of Se
and Mo did not respond to nutrient treatments.</p>
<p>Similar experiments were repeated during the mid- and late-summer of 2004,
with 5 mesocosms being fertilized with phosphorus, and another 4 with both phosphorus
and ammonium to create different nutrient gradients. Results from these experiments
were much more variable than those seen in the experiment conducted in 2003, and small samples (<i>n</i> = 5 for phosphorus treatments and <i>n</i> = 4 for both phosphorus and
ammonium treatments) yielded insufficient statistical power to effectively determine
statistically significant trends. However, contaminant sedimentation tended to respond to
phosphorus treatments in a similar manner as results from 2003; phosphorus-with-ammonium
treatments had little positive effect on contaminant sedimentation rates.</p>
<p>My results suggest that phytoremediation has the potential to lower many surface
water contaminants through the sedimentation of phytoplankton. Based on our results
from 2003, we estimate that the Saskatchewan Surface Water Quality Objectives
(SSWQO) for the DJX pit would be met in approximately 45 weeks for Co, 65 weeks
for Ni, 15 weeks for U, and 5 weeks for Zn if treated using phytoremediation.</p><p>Note:</p><p>Appendix A content (pages 92-95) contains copyrighted material which has been removed. It can be viewed in the original thesis upon request.</p>

Tags

Open-pit

Metals

Uranium

Pit-lakes

Contaminants

Nutrients

Phosphorus

Nitrogen

Phytoplankton

Mining

Bioremediation

Sedimentation

Additional Fields

Identifer	oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-05282012-111234
Date	28 May 2012
Creators	Dessouki, Tarik C.E.
Contributors	Neal, Brian R., Sheard, J.W., Hudson, Jeffrey James
Publisher	University of Saskatchewan
Source Sets	Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada
Language	English
Detected Language	English
Type	text
Format	application/pdf
Source	http://library.usask.ca/theses/available/etd-05282012-111234/
Rights	unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.