Comparison of Heavy Metal Intake by Different Species of the Genus Allium L

Heavy metals in onion (Allium cepa L.) and environmental and health risks

This study aimed to determine heavy metal content in soil and selected cultivars of onion. Cd content in soil exceeded the limit 2.43 times. Bioavailable forms of Pb and Cd in soil exceeded the critical value 5.9 times and 1.9 times, respectively. Analysed cultivars were not bioaccumulators of monitored heavy metals. However, Pb and Cd content in cultivars Nanas F1, Kappa and Daytona F1 exceeded the maximum limit set by the EU regulation. For Pb this was also the case for the Spirith cultivar. Based on health risk assessment it could be concluded that moderate consumption of onions from the studied localities does not pose a risk to consumers.

The Design of Experiment as a Tool to Model Plant Trace-Metal Bioindication Abilities

Bioindicator plants are species that have the capacity to linearly uptake some elements (metal and metalloids) from the growing substrate, thus reflecting their concentration in the soil. Many factors can influence the uptake of these elements by plants, among which is the simultaneous presence of several metals, a common situation in contaminated or natural soils. A novel approach that can be used to validate the bioindication ability of a species growing on a polymetallic substrate is the design of experiment (DoE) approach. The aim of the present study was to apply the DoE in full factorial mode to model the Cu, Cd, Pb, Zn, and Cr bioindication capacity of Polygonum aviculare, used as the model plant. The results showed that P. aviculare has the ability to bioindicate Cd and Cr with a linear uptake (from 0.35 to 6.66, and 0.1 to 3.4 mg kg-1, respectively) unaffected by the presence of other metals. Conversely, the uptake of Pb, Cu, and Zn is strongly influenced by the presence of all the studied metals, making their concentration in the plant shoot not proportional to that of the soil. In conclusion, these preliminary results confirmed that the DoE can be used to predict the bioindicator abilities of a plant for several elements at the same time and to evaluate the interactions that can be established between variables in the growing medium and in the plant itself. However, more studies including other plant species are needed to confirm the effectiveness of this method.