The diffusive gradients in thin films (DGT) technique is recognized to have advantages over traditional techniques. For example, the passive measurement generally follows the principle of metal uptake by plants, and its result incorporates the influences of soil properties, which may make DGT a good protocol for improving soil quality guidelines (SQGs). However, DGT has rarely been applied to assess Cd phytoavailability in soils under greenhouse vegetable production (GVP) systems. In this study, 29 turnips (Raphanussativus L.), 21 eggplants (Solanum melongena L.) and their corresponding soils were collected from GVP systems in Dongtai and Shouguang, eastern China. Simple linear regression and stepwise regression were performed using the soil Cd content and soil properties to predict the vegetable Cd content. Soil thresholds were derived based on both total and available Cd concentrations. The results showed that total Cd, DGT-measured Cd (DGT-Cd), soil-solution Cd (Soln-Cd) and CaCl2-extractable Cd (CaCl2-Cd) were all significantly correlated with vegetable Cd. DGT-Cd had the best correlation with turnip Cd. The total Cd threshold values ranged from 4.87 (pH 6.5) to 5.18 (pH 7.5) mg kg−1 for turnips and 14.60 (pH 6.5) to 14.90 (pH 7.5) mg kg−1 for eggplants. These Cd thresholds were higher than the current SQGs. The predicted of turnip Cd by DGT-Cd was not improved significantly by further considering the soil properties. The calculated soil threshold of DGT-Cd was 5.35 μg L−1 for turnips. However, the predicted soil threshold of DGT-Cd for eggplant was improved by including SOM, with R2 values from 0.53 to 0.70. The DGT-Cd threshold was calculated as 1.81 μg L−1 for eggplant (30.0 g kg−1 SOM). In conclusion, whether DGT measurements are independent of soil properties and preferable for the evaluation of Cd phytoavailability and the generation of soil thresholds remains to be clarified in future research.

To better determine phytotoxicity thresholds for metals in the soil, studies should use actual field-contaminated soil samples rather than metal-spiked soil preparations. However, there are surprisingly few such data available for Cu phytotoxicity in field-contaminated soils. Moreover, these studies differ from each other with regards to soil characteristics and experimental setups. This study aimed at more accurately estimating Cu phytotoxicity thresholds using field-collected agricultural soils (Entisols) from areas exposed to contamination from Cu mining. For this purpose, the exposure to Cu was assessed by measuring total soil Cu, soluble Cu, free Cu2+ activity, and Cu in the plant aerial tissues. On the other hand, two bioassay durations (short-term and long-term), three plant species (Avena sativa L., Brassica rapa CrGC syn. Rbr, and Lolium perenne L.), and five biometric endpoints (shoot length and weight, root length and weight, and number of seed pods) were considered. Overall plant growth was best predicted by total Cu content of the soil. Despite some confounding factors, it was possible to determine EC10, EC25 and EC50 of total Cu in the soil. Brassica rapa was more sensitive than Avena sativa for all endpoints, while Lolium perenne was of intermediate sensitivity. For the short-term bioassay (21 days for all three species), the averaged EC10, EC25 and EC50 values of total soil Cu (in mg kg−1) were 356, 621, and 904, respectively. For the long-term bioassay (62 days for oat and 42 days for turnip), the averaged EC10, EC25 and EC50 values of total soil Cu (in mg kg−1) were 355, 513, and 688, respectively. The obtained results indicate that chronic test is a suitable method for assessing Cu phytotoxicity in field-contaminated soils.

In order to assess as to whether treated textile effluent could be safely used to irrigate some winter vegetables, growth room experiments were conducted. Varying levels of treated and untreated textile effluents were applied to germinating seeds of some winter vegetables and their effect was evaluated on germination and early growth stage using seed germination, growth, and biochemical attributes. From the results, it was obvious that textile effluent reduced seed germination and early growth of all vegetables. However, this effect was more pronounced at the highest concentration of textile effluent. Furthermore, treated textile effluent did not show any inhibitory effect on seed germination of all vegetables. Photosynthetic pigments such as chlorophyll a and b, and protein contents were higher in the leaves of all vegetable plants irrigated with treated textile effluent than those of supplied with untreated textile effluents. It has been observed that heavy metals were lower in concentration in treated textile effluent as compared with untreated textile effluent. However, germination and growth responses of all three vegetables were different to treated or untreated textile effluents. Furthermore, the Raphanus sativus ranked as tolerant followed by Brassica campastris and Brassica napus based on germination and growth responses. In conclusion, in view of shortage of water, textile effluent could safely be used for irrigation to vegetables after proper processing.

Food safety has often attracted attention worldwide. Few studies have investigated the heavy metal (HM) pollution and health risk assessment of crops and vegetables. The current work was conducted to evaluate the human risk assessment of HM (Cu, Cd, Cr, Pb, and Zn) in radish, lettuce, tomato, onion, turnip, squash, okra, sunflower, Jews mallow, and garden rocket cultivated in treated wastewater (TWW)-irrigated sites as compared with those cultivated in freshwater (FW)-irrigated sites. Irrigation water, soil, and different plants were collected from 6 farmlands irrigated with TWW and two agricultural sites irrigated with FW (Nile river). Heavy metal transfer factor (HMTF), chronic daily intake of metals (CDIM), health hazard risk (HR), and health hazard index (HI) were estimated. The results showed that the tested HM levels in FW and TWW were below the Food and Agriculture Organization (FAO) and Egyptian standards recommended for irrigation. In soil samples, HM levels were below the permissible limits for both tested sites. The HM in soil and plants grew in TWW-irrigated sites possessed multiple levels higher than those grown in FW-irrigated sites. Among different plants, HM levels in the edible parts of plants grown in TWW-irrigated sites followed in decreasing order: tomato > sunflower >Jew’s mallow = turnip = squash > lettuce > okra = radish > onion > garden rocket. The mean CDIM and HR values of plants irrigated using TWW were higher than those irrigated using FW. Furthermore, HR values for all plants grown in polluted and unpolluted sites were < 1 except Cd in plants grown in the TWW-irrigated farmlands. The mean HI for radish, lettuce, tomato, onion, turnip, squash, okra, sunflower, Jews mallow, and garden rocket grown in TWW-irrigated sites were 2.08, 2.39, 1.76, 1.53, 2.08, 1.80, 2.03, 1.91, 1.82, and 1.44 (for adult), and 2.39, 2.75, 2.71, 1.75, 2.38, 2.06, 2.33, 2.69, 2.10, and 1.65 (for children). Plants irrigated with TWW showed a higher HMTF than plants irrigated with FW. Jew’s mallow and okra irrigated with TWW had a maximum HMTF. Consequently, different practical measures can be taken to minimize the HM levels in agricultural foodstuffs. These measures include preventing the excessive application of pesticides and fertilizers for crop production and continuous monitoring of different foodstuffs in the market.

Phytoextraction is a phytoremediation technique used for remediating polluted soils and it greatly relies on the plants’ capacities to accumulate contaminants. Turnip is a high cadmium (Cd)-accumulating plant. We compared the Cd tolerance, growth, and Cd accumulation characteristics of two turnip landraces with three additional commonly known high Cd-accumulating species to systematically estimate its Cd phytoremediation potential. Results showed that the turnips could tolerate relatively lower Cd concentrations than other plants. Growth characteristics analyses indicated that the turnips initially grew rapidly and then gradually slowed down, and their photosynthetic parameters indicated that biomass accumulation was easily affected by light. However, the Cd uptake and translocation capacities of the two turnip landraces were higher than those of Phytolacca americana Linn. and Bidens pilosa Linn. but close to that of Brassica napus Linn.. Ultimately, large amounts of Cd accumulated in turnips during early growth and slightly increased as the fleshy roots increased in size. Based on these findings, the present turnip landraces have potential for soil remediation, but additional research is needed before these landraces can be practically used. Moreover, turnips are good candidates for studying the molecular mechanism of high Cd accumulation in plants.

A comprehensive study was conducted to appraise the concentrations of 30 endocrine disrupting pesticides (EDPs) in soil and vegetable samples collected from Khyber Pakhtunkhwa, Pakistan. The sum of 30 EDPs (Σ₃₀EDPs) ranged from 192 to 2148 μg kg⁻¹ in the collected soils. The selected EDP concentrations exceeded their respective limits in most of the tested soils and showed great variation from site to site. Similarly, high variations in Σ₃₀EDP concentrations were also observed in vegetables with the highest mean concentration in lettuce (28.9 μg kg⁻¹), followed by radish (26.6 μg kg⁻¹), spinach (25.7 μg kg⁻¹), onion (16.2 μg kg⁻¹), turnip (15.6 μg kg⁻¹), and garlic (14.7 μg kg⁻¹). However, EDP levels in all studied vegetables were within FAO/WHO limits. The mean bioconcentration factor values were observed < 1 for all the studied vegetables. The health risk assessment revealed that the incremental lifetime cancer risk (ILCR) of Σ₃₀EDPs associated with vegetable ingestion was below the acceptable risk level (1 × 10⁻⁶), showing no cancer risk to local inhabitants. However, exposure to endocrine disruptor and probable carcinogen heptachlor epoxide poses a potential non-cancer risk (hazard quotient (HQ > 1)) to children through vegetable consumption. The presence of banned EDPs in soils and vegetables of the study area indicates the stability of these legacy chemicals in the environment from over usage in the past or illegal current application for agricultural purposes. Graphical abstract

Pakistan is an agricultural country and due to the shortage of clean water, most of the irrigated area (32,500 ha) of Pakistan was supplied with wastewater (0.876 × 109 m³/year). Concentrations of heavy metals in radish (Raphanus sativus) and turnip (Brassica rapa) taken from vegetable fields in Sargodha, Pakistan, were measured. Untreated wastewater was used persistently for a long time to irrigate these vegetable fields. A control site was selected that had a history of fresh groundwater irrigation. Mean metal concentrations were found for irrigation water, soil, and vegetables. In irrigation water, concentrations of Mo and Pb at three sites and Se at sites II and III were higher than the recommended limits. In vegetables, concentrations of Mo and Pb were above the maximum permissible limits. High bioconcentration factor was observed for Zn (12.61 in R. sativus and 11.72 in B. rapa) at site I and high pollution load index was found for Pb (3.89 in R. sativus and 3.87 in B. rapa) at site II. The differences in metal concentrations found in samples depended upon different soil nature and assimilation capacities of vegetables at different sites which in turn depended upon different environmental cues. The entrance of metal and metalloids to human body may happen through different pathways; however, the food chain is the chief route through which metals are transferred from vegetables to individuals. Health risk index observed for metals, (Mo, As, Ni, Cu, and Pb) higher than 1 indicated high risk through consumption of these vegetables at three sites.

A sensitive and selective method was developed and validated for the determination of pyrethrin residues in turnips (turnip leaves, turnip tubers, and the whole of plant) and cultivated soil using gas chromatography coupled with mass spectrometry (GC-MS). Six major components of pyrethrins (pyrethrin I and II, cinerin I and II, and jasmolin I and II) were separated and identified. The method involving solid-phase extraction (SPE) cleanup led to satisfactory average recoveries (88.1–104%) with limits of quantification (LOQs) of 0.05 mg/kg. The dissipation and final residue of pyrethrins in six provinces (among these places, two experiments were conducted in greenhouse and other four experiments in open filed) in China were studied. The trial results suggested that the half-lives of pyrethrins in the whole of turnips and soil were 0.5–1.6 and 1.0–1.3 days, respectively, and the degradation of pyrethrins in the greenhouse was quicker than that in open fields. The final residues of pyrethrins in turnip leaves and tubers were all below the maximum residue limit (MRL) established by the EU (1.0 mg/kg). A pre-harvest interval of 2 days and MRL of 1.0 mg/kg are recommended to ensure food safety standards for pyrethrins in turnips. Long-term risk assessment and short-term risk assessment of turnip tubers were evaluated. Hazard quotient (HQ) and acute hazard index (aHI) were significantly less than 100%, indicating negligible risk for consumption of turnip tubers.