The extensive development of agriculture in urban and peri-urban wastelands polluted with several trace elements (TE) poses risks to human health through contaminated food products. The objective was to explore the accumulation of TE in the various parts of vegetable crop plants (tomato, French bean, radish, potato, spinach, and leek) intercropped with phytostabilizing plant species (ryegrass and white clover, respectively). Field studies were conducted in a multicontaminated French urban wasteland with Cd, Cu, Pb and Zn, and an alkaline soil pH. Analyses of the respective non-edible parts of monocultured vegetable crops showed accumulation of all TE, mostly Zn, then Pb and Cu, and finally Cd. The corresponding TE accumulation factors (soil to plant) were all below 0.25. In the edible parts, average concentrations for TE were above the limit values, according to European and Chinese standards. TE contents in the phytostabilizing species chosen were in the same orders of magnitude and the same ranking as described for vegetable crops and most accumulation was in the roots. Unexpectedly, the presence of the phytostabilizing plants had a very strong positive impact on the soil to plant accumulation factor. Moreover, the edible plant parts were poorly impacted by the co-cropping with phytostabilizing plants.

Arbuscular mycorrhizal fungi (AMF) hold a crucial role in ecosystems because they are involved in nutrient cycling between soil and plants. This work aimed at evaluating the impacts that atmospheric pollution by polycyclic aromatic hydrocarbons may have on infectivity of indigenous AMF in soils. Two agricultural soils (Maconcourt, La Bouzule) were exposed for 2 weeks to ambient air (control, C) or to atmospheric phenanthrene (PHE) deposition (180 μg m−3 air). After exposure, soils were divided into a top (0–1 cm) and a bottom (1–15 cm) layer fraction. AMF infectivities of soils were determined after 2 weeks of atmospheric exposition using leek (Allium porum) as bioassay plant. Atmospheric PHE was mainly recovered in the top layer of soil (500–1,350 μg kg−1) of both soils and did not readily diffuse into the depth. Atmospheric contamination led to decreases in AMF infectivities of the top layer in both soils and affected the growth of leeks. Our results not only report evidence that infectivity of indigenous AMF is sensitive to PHE in soils but also emphasize that AMF are primary affected by the soil layer regardless to the pollution level.

Agricultural soil is easily polluted by heavy metal and recently by metal-based nanoparticles, which has been synthesized in lab and discarded to environment. The uptake and accumulation of them by crops in polluted soil may pose high risks for human health. Here, we investigated the fate and the fixation effect of Fe₃O₄-GO nanocomposites (NCs) to lead ions in the soil-leek system during four harvest lifecycle. The results showed within 100 days, 600-mg/kg Fe₃O₄-GO significantly decreased Pb(II) concentrations in leaves by 37.89%, 39.10%, 73.86%, and 47.17% compared with controls. When Fe₃O₄-GO was added into Pb(II)-polluted soil, a significant fixation effect of Pb(II) was found, and the reduce percentages were 47.29%, 66.60%, 78.04%, and 39.16% for leaves, stem, storage roots, and absorbing roots compared with controls. The scanning electron microscope images showed that the overall appearance of Fe₃O₄-GO has not been destroyed during the interaction with soil. Graphical Abstract

Leaf vegetables serve as an important food for the local residents in China. This paper focuses on the uptake, accumulation, transfer, and mercury (Hg) sensitivity of leafy vegetables. Two types of soil (an alkaline Cambosol and an acid Ferrosol) and eleven species of leafy vegetable, namely, Spinach, Tung choy, Leek, Fennel, Coriander, Chinese flowering cabbage, Wuta-tsai, Pakchoi, Chicory, Crown daisy, and Lettuce, were selected to investigate their sensitivity to Hg accumulation in a greenhouse pot experiment. Three Hg concentration treatments were carried out as control (background values), low concentration (1.5 times standard value), and high concentration (2 times standard value) as adjusted by the soil pH. Hg concentrations of more than half vegetable samples grown in Cambosol (collected from Shandong Province) reached or exceeded the maximum permissible food safety levels (10 μg kg⁻¹) according to the General Standard of Contaminants in Food in China (GB 2762-2012), while only about 15% in Ferrosol (collected from Jiangxi Province). Meanwhile, Hg bio-concentration factors (BCF) in all treatments were < 1, while Hg translocation factors (TF) in most treatments were < 1. Correlation analysis among soil, root, and edible plant parts revealed that the principal source of Hg in leafy vegetables was most likely from Hg-contaminated soils. Species sensitivity distribution (SSD) models were constructed and their simulated curves indicated that sensitivity to Hg was highest in Pakchoi in low Hg-contaminated soils, and Chicory in highly Hg-contaminated soils. Therefore, Hg concentration is mostly accumulated in roots of leafy crops, which reduces the risk of Hg bioaccumulation in edible portion of vegetables, and (2) Brassicaceae vegetables are mostly less sensitive to soil Hg contamination. Our results provide effective guidance for the selection of leafy vegetables for cultivation and daily consumption that minimizes health risk.