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The dwindling availability of agricultural land, caused by factors such as rapid population growth, urban expansion, and soil contamination, has significantly increased the pressure on food production. To address this challenge, cultivating non-food crops on contaminated land has emerged as a promising solution. This approach not only frees up fertile soil for food production but also mitigates human exposure to contaminants. This work aimed to examine the impact of soil contamination with Cd, Pb, Ni, and Zn on the growth, productivity, metal accumulation, and the tolerance of five lignocellulosic non-food crops: switchgrass (Panicum virgatum L.), biomass sorghum (Sorghum bicolor L. Moench), giant reed (Arundo donax L.), African fodder cane (Saccharum spontaneum L. spp. aegyptiacum Willd. Hackel), and miscanthus (Miscanthus × giganteus Greef et Deu.). A two-year pot experiment was conducted in Greece, Italy, and Portugal, following the same protocols and applying various levels of metals: Cd (0, 4, 8 mg kg−1), Pb and Zn (0, 450, 900 mg kg−1), and Ni (0, 110, 220 mg kg−1). The experimental design was completely randomized, with three replicates for each treatment. The results showed that switchgrass and sorghum generally maintained their height and productivity under Cd and Pb stress but were adversely affected by high Zn and Ni concentrations. Giant reed and African fodder cane showed reduced height and productivity at higher Ni and Zn levels. Miscanthus exhibited resilience in height but experienced productivity reductions only at the highest Zn concentration. Heavy metal uptake varied among crops, with switchgrass and sorghum showing high Cd and Pb uptake, while giant reed accumulated the most Cd and Zn. Miscanthus had the highest Ni accumulation. The tolerance indices indicated that switchgrass and sorghum were more tolerant to Cd and Zn at lower concentrations, whereas miscanthus had lower tolerance to Cd but a higher tolerance to Zn at higher concentrations. Giant reed and African fodder cane demonstrated stable tolerance across most heavy metals. Accumulation indices highlighted the effectiveness of switchgrass and sorghum in Cd and Pb uptake, while miscanthus excelled in Ni and Zn accumulation. The cluster analysis revealed similar responses to heavy metal stress between African fodder cane and giant reed, as well as between sorghum and miscanthus, with switchgrass displaying distinct behavior. Overall, the study highlights the differential tolerance and accumulation capacities of these crops, indicating the potential for phytoremediation applications and biomass production in heavy metal-contaminated soils. [ABSTRACT FROM AUTHOR]

Using contaminated land to grow lignocellulosic crops can deliver biomass and, in the long term, improve soil quality. Biostimulants and microorganisms are nowadays an innovative approach to define appropriate phytomanagement strategies to promote plant growth and metal uptake. This study evaluated biostimulants and mycorrhizae application on biomass production and phytoextraction potential of four lignocellulosic crops grown under two metal-contaminated soils. Two greenhouse pot trials were setup to evaluate two annual species (sorghum, hemp) in Italy and two perennial ones (miscanthus, switchgrass) in China, under mycorrhizae (M), root (B2) and foliar (B1) biostimulants treatments, based on humic substances and protein hydrolysates, respectively, applied both alone and in combination (MB1, MB2). MB2 increased the shoot dry weight (DW) yield in hemp (1.9 times more), sorghum (3.6 times more) and miscanthus (tripled) with additional positive effects on sorghum and miscanthus Zn and Cd accumulation, respectively, but no effects on hemp metal accumulation. No treatment promoted switchgrass shoot DW, but M enhanced Cd and Cr shoot concentrations (+84%, 1.6 times more, respectively) and the phytoextraction efficiency. Root biostimulants and mycorrhizae were demonstrated to be more efficient inputs than foliar biostimulants to enhance plant development and productivity in order to design effective phytomanagement strategies in metal-contaminated soil. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the phytoremediation potential of fiber flax (Linum usitatissimatum L., var. Calista) cultivated in a soil contaminated with multiple metals, under real field conditions. A two-year (2022 and 2023) field experiment was conducted in a site contaminated with elevated concentrations of Cd, Ni, Cu, Pb, and Zn due to mining and metallurgical activities. Three different nitrogen fertilization levels were tested (N0: 0 kg N ha−1, N1: 30 kg N ha−1, N2: 60 kg N ha−1), and both spring and winter sowings were conducted. At full maturity, growth parameters and yields were measured. The phytoremediation potential of flax was assessed in terms of the metal concentrations in the above-ground biomass and of the metal uptake (i.e., the potential removal of the soil metals in g ha−1 and per year). Flax demonstrated a shorter growth cycle, with shorter and thicker plants and higher yields when sown in spring compared to winter sowing. Plant growth and productivity were not evidently influenced by additional nitrogen fertilization during plant growth. The cadmium bioaccumulation factor was 1.06, indicating that flax accumulates this metal. For Ni, Cu, Pb, and Zn, the corresponding values were 0.0, 0.04, 0.004, and 0.02, suggesting that this crop excludes these metals. The order of the higher uptake in plant tissues was as follows: Zn > Pb > Cd > Cu > Ni. In conclusion, flax demonstrated tolerance to heavy metals in the soil, effectively supporting soil restoration through cultivation. Additionally, flax showed potential as a cadmium accumulator while excluding nickel, copper, lead, and zinc. [ABSTRACT FROM AUTHOR]

Faced with the ongoing energy transition and the escalating fragility of our natural ecosystems, ecological reclamation emerges as an imperative necessity. Investigation within this field has been in progress since the early 20th century. To gauge the advancements in this realm, elucidate the evolving research trends, and emphasize pertinent metrics, it is essential to perform a comprehensive overview of the subject. Undertaking this bibliometric study is necessary to clarify research's current state of play, grasp research hotspots, showcase outstanding researchers, and predict future research trends. In this work, 40,386 articles were retrieved from the Scopus and Web of Science databases, and bibliometric analysis was carried out using the Biblioshiny R package (Version 4.0.0, K-Synth Srl, Naples, Italy), and Python (PyCharm Community Edition 2023.2.1)o understand the progress in this research field from 1980 to 2023. The findings reveal a consistent upward trend in the publication rate within the field of mine closure and ecological reclamation over this timeframe, culminating in 6705 articles by 2022. Notably, authors and institutions from China have taken the lead, followed closely by those from the USA and Canada in terms of article publications. This prominence can be attributed to these countries' rapid economic growth and energetic transition, which has frequently come at the expense of environmental quality, and a rise in reclamation challenges. In this sense, the circular economy has risen in force recently, which highlights the withdrawal of the old linear economy. In coming research on mine closure and ecological reclamation, multi-scale ecological reclamation research should be reinforced, and social and economic concerns should be integrated. This study pinpointed current research hotspots and forecasted potential future research areas, providing a scientific baseline for future studies in mine closure and ecological reclamation. [ABSTRACT FROM AUTHOR]

To limit the generation of acid mine drainage at the Kettara abandoned mine (KAM) located 35 km North‐North West of Marrakech, Morocco, a store‐and‐release (SR) system was constructed. The SR system made of two materials, the cover constituted by phosphate waste (PW) rock and lower layer was the coarse‐grained tailings of KAM. The lower layer restricted water in the interface and the stocked water during wet periods by the PW layer is released during dry ones. The objective of this study is to assess the phytostabilization ability of SR cover using local plants. Seeds of five wild local plants: Atriplex semibaccata R. Br., Peganum harmala L., Asparagus horridus L., Launaea arborescens (Batt.) Murb., and Vicia sativa L., were selected and planted. Pots experiment of phosphate mine wastes (PW) and PW amended with different ratios of compost and commercial peat. These pot experiments were performed in greenhouse conditions. The germination and growth parameters studied were germination percentage (GP), mean germination time (MGT), speed of germination (SG), epigeal height, and hypogeal length evolution. Cd, Ni, As, Cu, and Zn concentrations in substrates and in plant fractions were analyzed. The results obtained using 100% PW (PW100) as the highest GP (87.50%) were obtained for A. semibaccata R. Br., followed by V. sativa L. with GP (25.00%). The uppermost MGT results showed that A. semibaccata R. Br. (MGT = 4.39) and L. arborescens (Batt.) Murb. (MGT = 1.91), were the most suitable for the phosphate mine wastes. Concerning SG, the values obtained were 19.07 and 5.11, for A. semibaccata R. Br., and L. arborescens (Batt.) Murb., respectively. Regarding the epigeal and hypogeal length, respectively, the best values were obtained for A. semibaccata R. Br., and V. sativa L., with 40.70 cm and 13.73 cm for epigeal length and 20.97 cm and 82.67 cm for hypogeal length. The results obtained with different ratios of amendments showed that the application of 10% compost and 20% organic fertilizer, showed significantly higher germination index, hypogeal, and epigeal growth for A. semibaccata R. Br., V. sativa L., and L. arborescens (Batt.) Murb. The concentrations of the studied trace elements in selected plant fractions does not exceed domestic animal metal toxicity limits in any trial. The concentrations of these trace elements in plant hypogeal fractions were significantly (p <.05) higher than those of epigeal fractions. The transfer and bio‐concentration factors were <1 in all selected plants. According to these results, we can affirm that A. semibaccata R. Br., as a key species and that V. sativa L. and L. arborescens (Batt.) Murb. are also good candidates for the phytostabilization necessary for the SR cover. [ABSTRACT FROM AUTHOR]

Giant reed (Arundo donax L.) plants were grown outdoors, in pots, for 2 years and were irrigated with metalliferous water containing cadmium (Cd) and nickel (Ni) in low (5 mg/L), medium (50 mg/L) and high (100 mg/L) concentrations, whereas in the control group tap water was used. The determined soil Cd and Ni total contents (extracted by HNO3 + H2O2) ranged widely (13.5-973.8 mg/kg Cd and 68.5-2543.3 mg/kg Ni). For assessing the metal accumulated in the different soil phases, three extractant solutions were used, giving distinct extractable concentration peaks in the topsoil, following the order EDTA>DTPA>> KNO3. At the end of each cultivation period, all plants were harvested and the above-ground parts were divided into three equal pieces, apart from the panicle. Fresh and dry weights as well as heavy metal contents for leaves and stem of each third and the panicles were determined. The results showed that plant growth was not affected by elevated heavy metal content in the irrigation water and, thereafter, in the soil. Cadmium and nickel accumulation in all plant parts was increased in both years by the treatments, and the highest concentrations were determined in the leaves of the lower third. Cadmium showed a clear and stable vertical distribution in all treatments; in leaves, a significant decrease towards the top was determined, while the opposite was observed in stems. Panicle Cd contents were similar to the upper stem thirds, increasing by treatment. Nickel contents were generally higher than that of Cd, and they did not show a significant height effect for all treatments. The determined Cd and Ni total uptake within each third (leaves+stems) showed the highest contents in the middle third for the first year, while, in the second year, metal allocation varied, depending on heavy metal and treatment. [ABSTRACT FROM AUTHOR]

The management of mine waste has become an urgent issue, especially in semi-arid environments. In this context, and with an aim to inhibit the oxidation of the sulfide tailings of the abandoned mine of Kettara in Morocco, a store-and-release (SR) cover made of phosphate mine waste (PW) was implemented. In order to guarantee its long-term performance, phytostabilization by local wild plant species is currently the most effective and sustainable solution. This study aimed to assess the growth performance and phytostabilization efficiency of five local wild plant species to grow on the SR cover made of PW. A field experiment was conducted for two growing seasons (2018 and 2019), without amendments and with the minimum of human care. PW and the aboveground and belowground parts of the studied plant species were collected and analyzed for As, Cd, Cu, Ni, and Zn. The bioconcentration factor (BCF) and translocation factor (TF) were also calculated. Despite the hostile conditions of the mining environment, the five plant species showed promising growth performances as follows: Atriplex semibaccata > Vicia sativa > Launaea arborescens > Peganum harmala > Asparagus horridus. The five plants showed high accumulation capacity of the trace elements, with the highest concentrations in belowground tissue. Principal component analysis distinguished A. semibaccata as having a high concentration of Cu and As, while Asparagus horridus had higher concentrations of Cd and Zn. In contrast, P. harmala, V. sativa, and L. arborescens demonstrated affinity regarding Ni. According to the BCF (<1) and TF (<1), these plant species could be used as effective phytostabilizers of the studied trace elements. The present study showed that local wild plant species have a great potential for the phytostabilization of PW, and could ensure the long-term efficiency of SR cover. [ABSTRACT FROM AUTHOR]

Jatropha curcas is a perennial crop originating from Central America that has become a promising candidate crop for production of bio oil which has the potential to replace or complement fossil diesel. This crop shows favourable attributes and considerable potential, such as hardiness, drought resistance, rapid growth, high oil content, and multiple uses. It is claimed to enhance socio-economic development, especially of poor rural areas in developing countries. Moreover, it can reclaim marginal and degraded lands in (semi-)arid regions, without competing with food production and without depleting natural carbon stocks and ecosystem services. Nevertheless, the full potential of this crop has not been realized yet, and there are several gaps in knowledge of its growth and agronomic management. [ABSTRACT FROM AUTHOR]