Search

Fire events can modify the distribution and speciation of potentially toxic elements (PTEs) in soil, especially if they are associated to organic matter (OM). In fact, OM can undergo substantial structural modifications at high temperatures, up to the complete mineralization. The present study aims to investigate the changes of PTEs’ bioavailability to durum wheat (Triticum durum Desf.) plants after simulating fire events (up to 300 °C and 500 °C) in an agricultural soil polluted by Cr, Zn, Cu, and Pb. The PTEs’ uptake and allocation in plant tissues were assessed using the RHIZOtest system. After the fire simulations, no evident risk of accumulation and translocation in plants was observed for Zn, Pb, and Cu. Conversely, a high accumulation in roots and a significant translocation to shoots were observed for Cr, which reached concentrations of 829 mg kg−1 in roots and 52 mg kg−1 in shoots at 500 °C. Additional experimental evidence suggested that Cr was taken up by plants grown on heated soils as Cr(VI). Once acquired by roots, only a small part of Cr (up to 6%) was translocated to shoots where it was likely present as mobile forms, as evidenced by micro X-ray fluorescence (µ-XRF) analyses. Overall, the results obtained provide evidence that the high temperatures occurring during fire events can increase the mobility and bioavailability of certain PTEs transforming apparently safe environments into potentially dangerous sources of pollution. These processes can ultimately affect the human health through the food chain transfer of PTEs or their migration into surface water and groundwater.

A combined approach based on multiple X-ray analytical techniques and conventional methods was adopted to investigate the distribution and speciation of Cr in a polluted agricultural soil, from the bulk-scale down to the (sub)micro-level. Soil samples were collected from two different points, together with a control sample taken from a nearby unpolluted site. The bulk characterization revealed that the polluted soils contained much higher concentrations of organic matter (OM) and potentially toxic elements (PTE) than the control. Chromium was the most abundant PTE (up to 5160 g kg−1), and was present only as Cr(III), as its oxidation to Cr(VI) was hindered by the high OM content. According to sequential extractions, Cr was mainly associated to the soil oxidisable fraction (74%) and to the residual fraction (25%). The amount of Cr potentially bioavailable for plant uptake (DTPA-extractable) was negligible. Characterization of soil thin sections by micro X-ray fluorescence (μXRF) and field emission scanning electron microscopy coupled with microanalysis (FEGSEM-EDX) showed that Cr was mainly distributed in aggregates ranging from tens micrometres to few millimetres in size. These aggregates were coated with an aluminosilicate layer and contained, in the inner part, Cr, Ca, Zn, P, S and Fe. Hyperspectral elaboration of μXRF data revealed that polluted soils were characterised by an exogenous organic-rich fraction containing Cr (not present in the control), and an endogenous aluminosilicate fraction (present also in the control), coating the Cr-containing aggregates. Analyses by high-resolution micro X-ray computed tomography (μCT) revealed a different morphology of the soil aggregates in polluted soils compared with the control. The finding of microscopic leather residues, combined with the results of bulk- and micro-characterizations, suggested that Cr pollution was likely ascribable to soil amendment with tannery waste-derived matrices. However, over the years, a natural process of Cr stabilization occurred in the soil thus reducing the environmental risks.

The increased costumers' request of safe and high-quality food products makes food traceability a priority for frauds identification and quality certification. Elemental profiling is one of the strategies used for food traceability, and TXRF spectroscopy is widely used in food analysis even if its potentialities have not been fully investigated. In this work, a new method for food traceability using directly TXRF spectra coupled with multivariate analyses, was tested. Twenty-four different beans' genotypes (Phaseolus vulgaris L.) grown onto two different sites have been studied. After the development of the method for beans' analysis, TXRF spectra were collected and processed with PCA combined with SNV and GLSW filter obtaining a perfect clustering of the seeds according to their geographical origin. Finally, using PLS-DA, beans were correctly classified demonstrating that TXRF spectra can be successfully used as fingerprint for food/seed traceability and that elemental quantification procedure is not necessary to this aim.

Microgreens are an emerging class of vegetables, which have become increasingly important in the agri-food market in recent years, and contain a number of macro- and micro-nutrients. This paper presents a rapid method for the elemental analysis of microgreens based on total reflection X-ray fluorescence (TXRF) spectroscopy, without preliminary sample digestion. The following elements were detected and quantified simultaneously for six microgreen genotypes, belonging to Asteraceae and Brassicaceae: P, S, K, Ca, Cl, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr. The limit of detection (LOD) varied depending on the element and ranged between 0.1 mg kg−1 for Sr and 42 mg kg−1 for P. The method was validated using certified standards, and results compared with those obtained using a conventional ICP-AES method requiring sample digestion. The paper also presents the advantages and disadvantages of the two techniques.

In the last years, uncontrolled fires are frequently occurring in forest and agricultural areas as an indirect effect of the rising aridity and global warming or caused by intentional illegal burnings. In addition, controlled burning is still largely used by farmers as an agricultural practice in many parts of the world. During fire events, soil can reach very high temperatures at the soil surface, causing dramatic changes of soil properties and elements biogeochemistry. Among soil elements, also potentially toxic elements (PTEs) can be affected by fires, becoming more or less mobile and bioavailable, depending on fire severity and soil characteristics. Such transformations could be particularly relevant in agricultural soils used for crop productions since fire events could modify PTEs speciation and uptake by plants and associated (micro)organisms thus endangering the whole food-chain. In this review, after describing the effects of fire on soil minerals and organic matter, the impact of fires on PTEs distribution and speciation in soils is presented, as well as their influence on soil microorganisms and plants uptake. The most common experimental methods used to simulate fires at the laboratory and field scale are briefly illustrated, and finally the impact that traditional and innovative agricultural practices can have on PTEs availability in burned agricultural soils is discussed in a future research perspective.

This study was carried out in two olive orchards (Olea europaea L., cv. Chemlali) located in a polluted area near a fertilizers factory and in a control unpolluted site, managed with similar cultivation techniques. The aim was to investigate the physiological and biochemical responses of polluted plants (PP), exposed to atmospheric metal contamination (Cd, Cu, Fe, Mn, Ni and Pb) as compared to control plants (CP). Leaves, roots and fruits of PP showed a depression of their non-enzymatic and enzymatic antioxidant defences and a disruption of their hormonal homeostasis. The anomalous physiological status of PP was also demonstrated by the lower values of pigments in leaves and fruits, as compared to CP. Atmospheric metals negatively affected olive oil chemical and sensory quality. However, despite metal deposition on fruit surfaces, the accumulation of potentially toxic metals in olive oil was negligible. Considering that olive oil is an important food product worldwide and that many productive olive orchards are exposed to several sources of pollution, this work could contribute to clarify the effects of atmospheric metal pollution on olive oil quality and its potential toxicity for humans.

Besides the variety of colours and flavours, microgreens show interesting nutritional properties, mainly regarding their contents of mineral nutrients and bioactive compounds. To date, the literature has prevalently focused on the individual nutritional features of microgreens usually belonging to Brassicaceae. The present study reports an articulated nutritional profile of six genotypes of microgreens, belonging to three species and two families: chicory (Cichorium intybus L., Puglia's local variety ‘Molfetta’, CM, and cultivar ‘Italico a costa rossa’, CR) and lettuce (Lactuca sativa L. Group crispa, cultivar ‘Bionda da taglio’, LB, and ‘Trocadero’, LT), from Asteraceae; and broccoli (Brassica oleracea L. Group italica Plenk, Puglia's local variety ‘Mugnuli’, BM, and cultivar ‘Natalino’, BN) from Brassicaceae. All the microgreens, except LB, can be considered good sources of Ca, whilst LT and CM also showed considerable amounts of K. As regards bioactive compounds, Brassica microgreens were the richest in phenolic antioxidants. The microgreens also presented higher amounts of α-tocopherol and carotenoids compared to mature vegetables. In particular, broccoli microgreens and LB showed the highest amounts of vitamin E, while Asteraceae microgreens presented the highest levels of carotenoids. Due to their delicate tissues, fresh cut microgreens showed a shelf life not exceeding ten days at 5 °C. The results obtained highlight the possibility to exploit genetic biodiversity in order to obtain tailored microgreens with the desired nutritional profiles, with particular regard to mineral nutrients and bioactive compounds. Appropriate pre- and post-harvest strategies should be developed, so as to allow microgreens to retain as long as possible their nutritional value.

Compost has been recently suggested as an alternative to peat for the preparation of growing substrates in soilless cultivation systems. However, some physico-chemical properties of compost may reduce plant performance and endanger the quality of productions, in particular for possible heavy metal accumulation in edible parts. This study aims at evaluating the suitability of a municipal solid waste compost (MSWC) and a sewage sludge compost (SSC) as components of growing media for the soilless cultivation of lettuce (Lactuca sativa L.). Heavy metal content of SSC complied with legislation limits but, in MSWC, it exceeded (Cu, Pb) or was very close (Cd, Zn) to safe limits. A greenhouse experiment was carried out by cultivating four lettuce cultivars ("Maximus," "Murai," "Patagonia," and "Aleppo") in pots containing a mixture of MSWC and perlite (MSWC + P), SSC and perlite (SSC + P), or peat and perlite (peat + P), the latter used as control. Plant biometric parameters measured after 72 days of growth revealed that the yield of plants cultivated on SSC + P was similar to control plants, independently of the cultivar. Conversely, MSWC + P suppressed in general the biomass production, especially for Murai and Patagonia cultivars. Compared to peat + P, both compost-based substrates reduced the leaf accumulation of heavy metals, with a major effect in Maximus plants. The levels of Cd and Pb in the edible part were always below the safe limits imposed by European regulation. Therefore, risks of heavy metal intake in food chain associated with the replacement of peat with compost in the growing media are negligible, even when a compost with a significant amount of heavy metals is used. Besides compost quality monitoring, also an appropriate varietal choice is crucial to obtain good yields and safe products.