The best meaning of the word "assimilate" as used in the passage is:
A. absorb as nourishment
1. In this context, "assimilate" means that the maize and canola plants are absorbing or taking in the mercury and gold that are present in the soil.
2. Just like how our bodies assimilate nutrients from food for nourishment, the plants are absorbing these elements from the soil around the farms.
3. Therefore, in the passage, "assimilate" refers to the process of absorbing or taking in the mercury and gold as nourishment for the plants.