NITRATE IN COAL WASTE ROCK DUMPS, ELK VALLEY, BRITISH COLUMBIA, CANADA
Date
2016-07-20
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-7375-276X
Type
Thesis
Degree Level
Masters
Abstract
Explosives used for blasting during mining operations contain nitrogen (N) compounds. The release of N from blasting residuals can result in elevated nitrate (NO₃ˉ) concentrations in freshly blasted waste rock, which can be subsequently leached from waste rock dumps. The distribution and leaching of NO₃ˉ through coal waste rock (rates and efficiencies) in the Elk Valley, British Columbia, Canada were studied using multiple datasets of NO₃ˉ, collected from pre-blast and fresh-blast rock, an unsaturated waste rock dump deposited between 1982 and 2012, and humidity cell (HC), and leach pad (LP) experiments. Chemical analyses showed NO₃ˉ concentrations in fresh-blast rock (27.6±47.4 mg/kg; n=36) to be greater than pre-blast rock (0.02±0.10 mg/kg; n=22). δ¹⁵N-NO₃ˉ and δ¹⁸O-NO₃ˉ analyses confirmed that the source of NO₃ˉ in the dump was the N used in the explosives. Laboratory aqueous leach tests on fresh-blast rocks showed the mass of N released from fresh waste rock equated to 3.4% N loss from the blasting residuals. δ¹⁵N-NO₃ˉ and δ¹⁸O-NO₃ˉ data suggested limited to no denitrification occurred in the unsaturated dump . Total NO₃ˉ-N mass released from humidity cells, leach pads, and boreholes indicated the leaching efficiency (EL) of NO₃ˉ to be scale dependent at about 20, 40 and 80%, respectively. Scale dependency of EL suggested that the findings from smaller scale experiments (HCs and LPs) are not applicable to the field-scale dump, but can be valuable for understanding the flushing mechanism of NO₃ˉ from the dump. Since 1982 the total NO₃ˉ-N mass flushed from the WLC dump was estimated to be about 1.1 × 10⁶ kg.
Description
Keywords
Nitrate, waste rock , Elk Valley, BC, Canada
Citation
Degree
Master of Science (M.Sc.)
Department
Geological Sciences
Program
Geology