Coupling with triolein-embedded cellulose acetate membrane (TECAM) technique, hydroxypropyl β-cyclodextrins (HPCD) extraction method, and the greenhouse pot experiments, the influences of biochars on polychlorinated biphenyls (PCBs) bioavailability in soil to plant (Brassica chinensis L. and Daucus carota) were investigated. Addition of 2% biochars to soils significantly reduced the uptake of PCBs in plant, especially for di-, tri- and tetra-chlorobiphenyls. PCBs concentrations in the roots of B. chinensis and D. carota were reduced for 61.5–93.7%, and 12.7–62.4%, respectively in the presence of biochars. The kinetic study showed that in the soils amended with/without biochars, PCBs concentrations accumulated in TECAM, as well as in the HPCD extraction solution, followed significant linear relationships with those in plant roots. Application of biochars to soil is a potentially promising method to reduce PCBs bioavailability whereas TECAM technique can be a useful tool to predict the bioavailability of PCBs in soil.

Root crops, carrot and celeriac, were exposed to atmospheric deposition in a polluted versus reference area. An effect was observed on the As, Cd and Pb concentrations of the leaves and the storage organs. The concentrations in the whole storage organs correlated well with atmospheric deposition, which shows that they even could be used for biomonitoring. Nevertheless, leaves remain much more appropriate. The results revealed also a significant increase of the As and Cd concentration in the consumable part of the storage organs as a function of their atmospheric deposition. As such the experiments allowed deriving regression equations, useful for modeling the atmospheric impact of trace elements on the edible parts of root crops. For Pb, however, there was hardly any significant impact on the inner parts of the storage organs and as such the transfer of Pb in the food chain through root crops can be considered to be negligible.

Alternative methods are needed to replace chemical nematicides because they have the potential to damage beneficial soil microbial diversity. Therefore, the present work was done to elucidate the soil ameliorative, plant-growth-promoting, and nematicidal properties of fly ash. A random block-designed pot experiment was conducted during the period, December 2018–February 2019. Seeds of carrot (Daucus carota L.) were sown under natural conditions in clay pots containing a growth medium comprising of field soil amended with different levels of fly ash. Plants were inoculated with Meloidogyne incognita that were molecularly characterized using 18S and D2/D3 fragments of 28S rDNA and morphologically through perineal pattern arrangement. The results revealed that fly ash application improved the soil’s important physicochemical characteristics. The inoculation of M. incognita significantly reduced the plant growth, yield, and pigment content of carrot compared to the untreated uninoculated plants. Carrot grown in 15% fly ash (85:15 w/w field soil:fly ash) growth substrate had significantly (P ≤ 0.05) improved plant growth, yield, and pigment content as compared to the untreated inoculated plants. Moreover, the proline content and the activity of superoxide dismutase (SOD) and catalase (CAT) were enhanced by applying 15% fly ash. Fly ash amendment to the soil not only improved plant growth and yield but also reduced the gall index and egg mass index per root system of the carrot as well. Our results, therefore, suggest that 15% fly ash can be used in a sustainable way to improve the growth, yield, and resistance of carrot against the infection of M. incognita.

The ability of seven herbaceous species (Hypericum perforatum L., Dactylis glomerata L., Plantago lanceolata L., Verbascum thapsus L., Picris hieracioides L., Cichorium intybus L., Daucus carota L.) to accumulate heavy metals such as Cd, Cr, Cu, Ni, Pb, and Zn has been studied. The concentration of heavy metals was determined in roots, basal and cauline leaves, flowers, and stalks for each collected species. The species were selected according to their cosmopolitan characteristics, morphology, life cycle, and phenology. Soils and plants were collected from two sites: close to a high traffic road in the inner city of Rome and in a natural park north of Rome (Canale Monterano). The concentration of elements in soil in descending order were Zn>Pb>Cu>Ni>Cr>Cd, while the EDTA extractable element concentrations in the roots followed the sequence Zn>Cu≈Pb>Cd>Cr>Ni. The bioaccumulation factors (BF) and the transport factors (TF) were calculated for each plant species. Results showed a significant relationship between heavy metals content in soil and plant species. H. perforatum showed a high Pb accumulation capacity in the stalk (70.30 mg kg⁻¹) and roots (73.41 mg kg⁻¹); moreover, BF>1 for this species at urban site has been obtained. Plantago lanceolata and Dactlys glomerata have shown higher Cd absorption (BF=1.33 and 0.55 in rural and urban sites, respectively). Plantago lanceolata in general shows high heavy metal uptake. The distribution of metals within the plant strongly depends on the species; the main accumulation of Ni, Cd, and Cu was observed in the leaves, while the highest Cr concentration was observed in the flowers. Plant species can be effectively considered as valid bioindicators of heavy metals derived from human activities and can be used to monitor pollution changes in the environment.

Amendment with treated biosolids can increase soil fertility and plant nutrition to the soil, but the fertilization value compared with other commercial soil amendments on the soil ecosystem is poorly understood. The effects of different proportions (0%, 5%, 10%, and 15%) of thermal and pH-treated biosolid applications on the growth performance, nutrient contents, and toxicity performance of carrots (Daucus carota L.) and choy sum (Brassica chinensis var. parachinensis) were studied. Different commercial organic soil amendments, such as biochar, chicken manure (CM), and food waste compost (FWC), were also used as a comparison in the experiment to determine the feasibility of biosolid application on agricultural use. All four soil amendments resulted in similar growth trends for the carrots and choy sum, and this information can be applied in selecting the appropriate species of plants. Through thermal and pH treatments, the treated biosolids decreased environmental risks and resulted in higher amounts of N and P in comparison to the other soil amendments. The results showed that 10% biosolid-amended soil performed best in terms of plant growth, biomass, and nutrient content for both carrots and choy sum. Nutrient analysis (N, P, and K) and heavy metal analysis (As, Cd, and Pb) on both soil and plants were conducted. It was proven that biosolid application was as functional as CM application and could be used as organic fertilizer to replace biochar and FWC for agricultural use. No heavy metals were found in the pure biosolids, which were safe to use as fertilizers. Utilizing biosolids as fertilizers could be an effective way to address the problem of waste disposal and landfill loading for the environment.

The main objective of the present study was to determine the optimum C/N ratio for converting waste paper and chicken manure to nutrient-rich manure with minimum toxicity. Six treatments of C/N ratio 20, 30, 40, 50, 60, and 70 (T1, T2, T3, T4, T5, and T6, respectively) achieved by mixing chicken manure with shredded paper were used. The study involved a composting stage for 20 days followed by vermicomposting with Eisenia fetida for 7 weeks. The results revealed that 20 days of composting considerably degraded the organic waste mixtures from all treatments and a further 7 weeks of vermiculture significantly improved the bioconversion and nutrient value of all treatments. The C/N ratio of 40 (T3) resulted in the best quality vermicompost compared to the other treatments. Earthworm biomass was highest at T3 and T4 possibly due to a greater reduction of toxic substances in these waste mixtures. The total N, total P, and total K concentrations increased with time while total carbon, C/N ratio, electrical conductivity (EC), and heavy metal content gradually decreased with time during the vermicomposting process. Scanning electron microscopy (SEM) revealed the intrastructural degradation of the chicken manure and shredded paper matrix which confirmed the extent of biodegradation of treatment mixtures as result of the composting and vermicomposting processes. Phytotoxicity evaluation of final vermicomposts using tomato (Lycopersicon esculentum), radish (Raphanus sativus), carrot (Daucus carota), and onion (Allium cepa) as test crops showed the non-phytotoxicity of the vermicomposts to be in the order T3 > T4 > T2 > T1 > T5 > T6. Generally, the results indicated that the combination of composting and vermicomposting processes is a good strategy for the management of chicken manure/paper waste mixtures and that the ideal C/N ratio of the waste mixture is 40 (T3).

Soil contamination represents a serious and significant issue, especially when it comes to soil used in agricultural practices. This research was carried out in order to investigate the accumulation level of potentially toxic trace elements (Cr, Cd, Cu, Mn, Ni, Pb and Zn) in soil and vegetables (Solanum lycopersicum and Daucus carota). The transfer of the trace elements from soil to vegetables and the potential risk assessment were studied as well. Results indicated relatively high levels of heavy metals. Cd, Cu and Pb exceeded the alert limits established by the Romanian legislation. Zn was high as well. Positive correlations between the Cr, Cu and Pb indicated similar source of pollution, possibly related to the activities occurred in the non-metallic facility, nearby the study area. The heavy metals determined in the Solanum lycopersicum fruits and Daucus carota roots were below the maximum allowable concentrations, according to the WHO/FAO guideline. Slightly higher amounts of Cr and Cu were measured in tomatoes, compared to the carrots. Nevertheless, carrots were richer in Ni and Mn. The applied pollution indices indicated a contamination with heavy metals in 90% of the soil samples, with 9% probability of toxicity, the remaining 10% being classified into the precaution domain category. The plant bioconcentration of heavy metals into the Solanum lycopersicum fruits and Daucus carota roots is characterized using transfer factors. Generally, the results indicate that Daucus carota was the most susceptible to uptake Cu and Mn, while Solanum lycopersicum would rather uptake Cd and Zn. The estimated non-carcinogenic risk, based on the human health risk indices, indicates that the studied vegetables are safe for consumption with no impact on the human health. The results are lower than the critical value. Similarly, the carcinogenic risk indices results showed acceptable risks of cancer developing. It is important to assess and monitor the heavy metals levels in soil and in the vegetables intended to be consumed, in order to prevent contamination and potential negative effects on the environment and implicitly on the human health. The obtained data can be used in remediation techniques, as well as in implementing control measures of heavy metal contamination in soil and vegetables.

Consumption of vegetables is often the predominant route whereby humans are exposed to the toxic metal Cd. Health impacts arising from Cd consumption may be influenced by changes in the mineral nutrient content of vegetables, which may occur when plants are exposed to Cd. Here, we subjected model root (carrot) and leaf (lettuce) vegetables to soil Cd concentrations of 0.3, 1.5, 3.3, and 9.6 μg g⁻¹ for 10 weeks to investigate the effect of Cd exposure on Cd accumulation, growth performance, and mineral nutrient homeostasis. The findings demonstrated that Cd accumulation in lettuce (20.1–71.5 μg g⁻¹) was higher than that in carrot (3.2–27.5 μg g⁻¹), and accumulation exceeded the maximum permissible Cd concentration in vegetables when soil contained more than 3.3 μg g⁻¹ of Cd. There was a marked hormetic effect on carrot growth at a soil Cd concentration of 3.3 μg g⁻¹, but increasing the Cd concentration to 9.6 μg g⁻¹ caused decreased growth in both crops. Additionally, in most cases, there was a positive correlation between Cd and the mineral nutrient content of vegetables, which was due to physiological changes in the plants causing increased uptake and/or translocation. This may suggest a general mechanism whereby the plant compensated for disrupted mineral nutrient metabolism by increasing nutrient supply to its tissues. Increased nutrient levels could potentially offset some risks posed to humans by increased Cd levels in crops, and we therefore suggest that changes in mineral nutrient levels should be included more widely in the risk assessment of potentially toxic metal contamination. Graphical abstract The Cd concentration (μg g-1 in dry matter) in the root, shoot and translocation factor (TF) of Cd from root to shoot in the carrot and lettuce, and the percentage of root Cd to the gross Cd contents (%) in carrot (C) and lettuce (D) exposed to soil Cd (0 (control), 1, 3, and 9 μg g-1) for 70 days. Values are means ± SD (n = 5).

This work examines the strategies adopted by an arbuscular mycorrhizal symbiotic system to ameliorate environmental Pb stress by examining the concentrations of P, Fe, and Pb in the fungal microstructures and the host’s root. In vitro cultures of Ri-T DNA-transformed carrot (Daucus carota L.) roots were inoculated with Glomus intraradices and treated with Pb(NO₃)₂ solution and the extraradical spores and mycelia (S/M) and the root with the vesicles, mycelia, and root cells were subsequently analyzed by polarized energy dispersive x-ray fluorescence (PEDXRF) spectrometry. Upon Pb treatment, within the root, the percentages of mycorrhizal colonization, the vesicles, and mycelia increased as well as the areas of the vesicles and the (extraradical) spores, although the number of spores and arbuscules decreased. The S/M and the mycorrhizal root showed enhanced concentrations of Pb, Fe, and P. These were particularly marked for Fe in the Pb-treated cultures. This indicates a synergistic relationship between the arbuscular mycorrhizal fungus and the host that confers a higher Pb tolerance to the latter by the induction of higher Fe absorption in the host. The intraradical vesicle, mycelia, and arbuscule numbers are interpreted as a “tactic to divert” the intraradical Pb traffic away from the root cells to the higher affinity cell walls of the arbuscular mycorrhizal fungi (AMF) microstructures in the apoplast. The results of this work show that the symbiosis between the AMF G. intraradices and the host plant D. carota distinctly improves the latter’s Pb tolerance, and imply that the appropriate metal tolerant host-AMF combinations could be employed in process designs for the phytoremediation of Pb.