The uptake of nickel and chromium from irrigation water by potatoes, carrots and onions.

Heavy metals, in general, can migrate from polluted soil and/or irrigation water to tuber plants, leading, after chronic consumption, to health problems. The scope of this study was to investigate the uptake of chromium and nickel by carrots (Daucus carrota), onions (Allium cepa) and potatoes (Solanum tuberosum) in a greenhouse experiment simulating the open-field irrigation conditions in the two biggest tuber producing regions of Greece (Asopos river in Viotia and Messapia in Evia). The study included cultivation of tubers for a period of approximately 4 months in six irrigation lines, each one provided by a water solution containing different levels of Cr(VI) and Ni(II) ranging from 0µg/l (control) to 250µg/l. The soil used was obtained from a certified organic greenhouse. Uptake of Cr was observed in onion leaves between 0 and 10µg/l water concentrations (+109.2 percent, p=0.006), 0µg/l and 20µg/l (+47.5 percent, p=0.006), 0µg/l and 50µg/l (+202.8 percent, p=0.006), 0µg/l and 100µg/l (+89.9 percent, p=0.028), 0µg/l and 250µg/l (+61.3 percent, p=0.009). Uptake of Ni was observed: (a) in onion leaves between 0 and 250µg/l water concentrations (+90.2 percent, p=0.076), (b) in onion shoots between 0 and 10µg/l (+39.1 percent, p=0.045), 0 and 250µg/l (+55 percent, p=0.047) and (c) in potatoes between 0 and 20µg/l (+28.1 percent, p=0.083). Our results suggest that irrigation water containing Cr and Ni can cross-contaminate onions and potatoes cultivated in a soil never previously polluted, anthropogenically, with heavy metals. No such results were found for carrots.

Μetal Uptake by Sunflower (Helianthus annuus) Irrigated with Water Polluted with Chromium and Nickel.

The water aquifers of the regions of Asopos River in Viotia and Messapia in Evia (Greece) have been contaminated with hexavalent chromium (Cr (VI)) and bivalent nickel (Ni (II)). Given that these areas are the two biggest tuber producing regions of Greece, in our previous work, the cross-contamination of the food chain with these two heavy metals was quantified. In the present study, the potential of sunflower (Helianthus annuus) cultivation in these regions is evaluated. The scope of our study was to investigate the uptake of chromium and nickel by sunflower, in a greenhouse experiment. The study included two cultivation periods of plants in six irrigation lines with different levels of Cr (VI) and Ni (II) ranging from 0 µg/L (control) to 10,000 µg/L. In all plant parts, statistically significant increased levels of Cr (VI) and Ni (II) were found when compared to control ones. Also, a positive correlation, both for Cr and Ni, between levels of heavy metals in irrigation water and plants was observed. Following European Food Safety Authority recommendations, the obtained oil was evaluated as safe for consumption, therefore, sunflower cultivation could be a valid bioremediation solution for the Asopos and Messapia regions.

The bioaccumulation and physiological effects of heavy metals in carrots, onions, and potatoes and dietary implications for Cr and Ni: a review.

The bioaccumulation of heavy metals in food tubers (carrots, onions, and potatoes) as a result of polluted irrigation water has been studied in this review paper. Given that heavy metals can cause a considerable oxidative stress, the impact of these metals to the physiology of the plants has also been assessed. The consumption of vegetables cross-contaminated with heavy metals carries a considerable risk for humans (especially for children and pregnant women) and these dietary implications are discussed while European Food Safety Authority has been urged to look into this matter of concern.