The Effect of Immobilizing Agents on Zn and Cu Availability for Plants in Relation to Their Potential Health Risks

Soil contamination with heavy metals is one of the most important threats to the environment because they are easily incorporated into the food chain, threatening the health of plants, animals, and humans. In this study, the effectiveness of the introduced substances (compost and fly ash) was assessed in terms of its influence on the content of Cu and Zn in the soil, potential accumulation of these metals in the cultivated plants (camelina and oat), and thus in food products prepared from these plants. Therefore, the following indicators were used: bioconcentration factors calculated for the total amount (BCFT) and bioavailable amount of metals (BCFB) as well as gender-estimated daily intake (EDI) and health risk index (HRI). Regardless of gender, the EDI values ranged from 0.31 µg·kg−1 to 0.49 µg·kg−1 for Cu and from 0.9 µg·kg−1 to 1.8 µg·kg−1 for Zn in oat. For camelina, the calculated values were as follows: 4.1–8.5 µg·kg−1 for Cu and 7.1–12.1 µg·kg−1 for Zn. The HRI values were very low (in general 0.03–0.2), indicating no health risk connected with potential consumption of oat or camelina food products. The amounts of Cu and Zn in the crops grown on the soil amended with compost or fly ash were significantly lower (by 21–37% for oat and 14–34% for camelina) compared to the content of these metals in the control plants. Moreover, the levels of bioavailable metals decreased in soil as a result of the applied immobilizing agents. The study showed that the immobilization efficiency of compost and fly ash was comparable, and therefore the choice of either of these substances for the chemical remediation of soil contaminated with heavy metals is justified.