Methodology

Lysimeter design

The lysimeter was constructed by connecting five major parts:

(1) a collection chamber, (2) a bottom disc (3) a 10 μm pore size filter section, (4) an upper disc, and (5) a sampling tube.

The lysimeters work by extracting water through the porous section, via applied vacuum, without significantly altering the chemical composition of the sample.

All parts can be easily disassembled, and acid cleaned individually.

Fig. 2 Lysimeter design and parts.

Installation of Lysimeters

Four installation sites (Fig. 3) near Elmvale, Ontario were selected for the testing of the plastic lysimeters. Each site represents a “nest”, and each nest consists of lysimeters installed in various positions (1 to 3) and two different depths: shallow (0-15 cm) and deep (15-30 cm) (Fig. 4) .

The 0-15 cm depth represents the topsoil layer, where organic matter is highest, and most root activity occurs, influencing the availability and mobility of trace elements.
The 15-30 cm depth provides insights into the subsoil, which may reflect processes such as leaching, adsorption, and mineral interactions, offering a comparison to the surface layer.

Fig. 3. Location of installation sites.

Fig 4. Lysimeters installed at Nest 1.

Sampling of soil solutions

Soil solution samples from the lysimeters were collected during three sampling events between Jul to Sep 2023. Sampling was done during this period, as seasonal conditions during this period reflect typical agricultural and ecological processes, making the data relevant for understanding trace element behavior under natural environmental conditions.
Acid-cleaned polypropylene bottles (PP) were used to contain samples for ICP-MS, & ICP-OES.
The samples for "dissolved" trace elements were filtered through a 0.45 µm acid-cleaned PTFE filter.
The lysimeters were connected to a vacuum pump and suction was applied. A sampling tube with a syringe was then inserted into the lysimeters to collect the soil water samples and subsequently filtered and transferred to sample bottles (Fig. 5).

Fig. 5. Collecting soil solution samples from the lysimeters.

Fig. 6. The SWAMP Laboratory.

Trace element analyses at the S.W.A.M.P. Laboratory

All laboratory work were performed in the metal-free, ultraclean S.W.A.M.P. (Soil, Water, Air, Manures and Plant) laboratory at the University of Alberta, Edmonton, AB, Canada (Fig. 6).
The concentrations of trace elements in the soil solutions were measured using Inductively Coupled Plasma - Mass Spectroscopy (ICP-MS), as described in the study by Du et al., (2020).

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