Methods
Materials Aqcuisition
Prior to starting any experiments, materials acquisition was necessary. While most materials/equipment could be obtained from a hardware store, the rock amendments, pea seeds, and soils were externally sourced. This involved some fieldwork in BC, and Ontario, as well as the provision of materials from academic and industry collaborators.
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Figure 1. Material source locations map.
Material Preparation
Following the acquisition of the rocks and soil, they needed to be prepared for the growth chamber trials. This involved the homogenization of the soil using a cement mixer, as well as the comminution of the rock samples into a fine powder (diameter P90 ~100 um) using a rock saw, sledgehammer, and ring mill.
Figure 2. Soil homogenization.
Experimental Setup
With all necessary materials acquired and characterized, the growth chamber trials could begin. This involved the filling of 63 soil pots, 3 control pots, and 3 pots per amendment rate/amendment type combination (4 spreading rates, 5 amendment types). Next, the pea seeds were added and inoculated (with B. japonicum). Following this, the leachate collection system was installed under each pot. Once everything was set up, the plants were then watered twice each week until they completed their growth cycle.
Figure 3. Growth chamber set up.
Figure 4. Layout of pots in growth chamber apparatus. Unfortunately blocking was not considered at the time of experimental setup.
Sample Collection
Throughout the extent of the growth chamber trials, leachates from each pot were collected every two weeks. They were then filtered to remove all organic materials, and preserved for analysis with HNO3 to prevent precipitate formation.
Figure 5. Leachate collection system.
Sample Analysis
The preserved leachates were analyzed for potential nickel contamination using inductively coupled plasma optical emission spectroscopy. Further they were analyzed for alkalinity (as a proxy for carbon dioxide removal) using a HACH spectrophotometer.
Figure 6. Bromophenol blue indicator used to test for alkalinity in collected leachates.