Uptake of Uranium by Lettuce (Lactuca sativa L.) in Natural Uranium Contaminated Soils in Order to Assess Chemical Risk for Consumers

Abstract

Uranium mining activity in Cunha Baixa (Portugal) village has left a legacy of polluted soils and irrigation water. A controlled field experiment was conducted with lettuce (Lactuca sativa L.) in an agricultural area nearby the abandoned mine in order to evaluate uranium uptake and distribution in roots and leaves as well as ascertain levels of uranium intake by the local inhabitants from plant consuming. Two soils with different average uranium content (38 and 106 mg/kg) were irrigated with non-contaminated and uranium contaminated water (<20 and >100 μg/l). A non-contaminated soil irrigated with local tap water (<1 μg/l uranium) was also used as a control. Uranium in lettuce tissues was positively correlated with soil uranium content, but non-significant differences were obtained from contaminated soils irrigated with different water quality. Uranium in plants (dry weight) growing in contaminated soils ranged from 0.95 to 6 mg/kg in roots and 0.32 to 2.6 mg/kg in leaves. Lettuce bioconcentration is more related to available uranium species in water than to its uranium concentration. Translocated uranium to lettuce leaves corresponds to 30% of the uranium uptake whatever the soil or irrigation water quality. A maximum uranium daily intake of 0.06 to 0.12 μg/kg bodyweight day was estimated for an adult assuming 30 to 60 g/day of lettuce is consumed. Although this value accounts for only 10% to 20% of the recommended Tolerable Daily Intake for ingested uranium, it still provides an additional source of the element in the local inhabitants' diet.

Estimation of the radiological background and dose assessment in areas with naturally occurring uranium geochemical anomalies—a case study in the Iberian Massif (Central Portugal)

“…The radioisotope activity data obtained in vegetables is in good agreement with previous work performed in similar geological settings (Bettencourt et al, 1988;Carvalho et al, 2009;Neves et al, 2008). The radionuclide uptake from the studied broadleaf plants (cabbage and turnip) is higher than in tubers; in the case of potatoes, analyzed with the peel, it is expected that the activity should be significantly lower if the analysis is performed without it, as it was also shown in previous studies (Neves et al, 2009).…”

Biogeochemistry of uranium in the soil-plant and water-plant systems in an old uranium mine

“…Uranium disposed into the environment can reach the top of the food chain and be ingested by humans (e.g., Anke et al, 2009;Craft et al, 2004;Neves et al, 2008Neves et al, , 2012Xie et al, 2008), causing health disorders such as kidney or liver diseases and even death (e.g., Craft et al, 2004;Xie et al, 2008). Thus, it is necessary to treat waste material containing U, as well as U-contaminated water, soil and sediment, in order to prevent its dispersion in the environment.…”

Are uranium-contaminated soil and irrigation water a risk for human vegetables consumers? A study case with Solanum tuberosum L., Phaseolus vulgaris L. and Lactuca sativa L.

“…In fact, during September to November (autumn season) 2005, an equal field experiment was carried out in the same Cunha Baixa soil and U concentration in lettuce was lower (100 ± 20 lg/kg FW) in soil plot irrigated with contaminated water (Neves et al 2008) than the observed in lettuce cultivated in 2006 summer season (this study). As soil conditions, namely U soil available fraction concentrations and irrigation water quality were similar, the differences in U plant leaves concentration can be explained by the lower frequency and lower amount of water irrigation used in autumn season (8 handling times, due to meteorological conditions), in opposition to 2006 summer season when plants were watered 3 and 11 times by handling and furrow, respectively (Table 1).…”

“…The soil (40 m 2 ) was divided in two plots (P1, P2) and both subdivided in four replicates each, as described in Neves et al (2008). Composite soil samples (0-20 cm) were taken at each replicate before plantation.…”

“…The implication of contamination to agricultural soils due to irrigation with U-contaminated water and the consequently phyto-accumulation in food crops associated with dietary exposure to U started to be studied recently in Cunha Baixa area (Neves et al 2008).…”