• Thallium accumulates readily in lettuce in a concentration-dependent manner • Rare earth elements show moderate and concentration-dependent uptake • Gallium uptake by lettuce is low but rises sharply at high soil concentrations • Neodymium reduces seed germination, affecting crop productivity The increasing use of Technology-critical elements (TCEs) in modern technologies is expected to raise their concentrations in soils of many areas, prompting concerns about their mobility and entry into the food chain. This study examines pore water availability and plant uptake of gallium (Ga), thallium (Tl), and the rare earth elements gadolinium (Gd), neodymium (Nd), and ytterbium (Yb). Lettuce ( Lactuca sativa ) was grown under controlled greenhouse conditions in a native agricultural soil from Sweden, both at the baseline concentrations of the elements and after spiking in a concentration series in which the highest level corresponded to a 40-fold enrichment of the original concentrations. Our findings indicate that Tl poses the greatest risk among the investigated TCEs, as it was readily taken up by lettuce even at moderate concentrations in the soil, with a clear dose-dependent increase in accumulation (Bioconcentration factor, BCF = 0.084–1.5). Gallium demonstrated a low concentration in pore water and limited accumulation in lettuce (BCF = 0.00010–0.00066), suggesting a low immediate concern. However, the Ga uptake increased substantially at the highest contamination level, indicating a potential risk threshold. Relative to Ga and Tl, the REEs demonstrated intermediate levels of both pore water availability and lettuce uptake, although the uptake increased with rising soil concentrations (BCF = 0.0013–0.0071, 0.0013–0.012, and 0.0011–0.0020, for Gd, Nd, and Yb respectively). Notably, Nd was also found to negatively affect seed germination, suggesting a possible risk to crop productivity. Together, our findings highlight the need for targeted risk assessments of specific TCEs, as these elements may increasingly find their way onto our plates through soil-to-plant transfer under potential future soil contamination.
Qvarforth et al. (Sun,) studied this question.