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Phytoremediation represents a natural method to remove contaminants from soil. The goal of this study was to investigate the potential of phosphate-assisted phytoremediation by two energy crops, Cannabis sativa L. and Brassica juncea L., for the sustainable remediation of heavily arsenic-contaminated industrial soil. The two species were investigated for uptake, translocation, and physiological effects of arsenic and phosphate in a microcosm test. Although C. sativa and B. juncea were symptomless when grown in arsenic-contaminated soil, an important reduction of biomass (50 and 25%, respectively) was observed as a stress marker. Phytotoxicity and cytotoxicity effects promoted by contaminated soils were investigated in both the species and a model plant for ecotoxicity studies, Vicia faba L., which is the most developed model to test genotoxicity effects in terms of chromosomal aberration and micronuclei presence. The higher amount of arsenic was found in C. sativa and B. juncea roots (on average 1473 and 778 mg kg-1, respectively), but both species were able to uptake and translocate arsenic in leaves and stems, up to 47.0 and 189 mg kg-1, respectively. Phosphate treatment had no effect on arsenic uptake in none of the crop, but significantly improved the plant performance. Biomass production resulted similar to that of B. juncea control plants. Antioxidant enzymatic activities and photosynthetic performance responded differently in the two crops. The present investigation provides new insight for a proficient selection of the most suitable crop species for sustainable phytomanagement of a highly polluted As-contaminated site by coupled phytoremediation-bioenergy approach.

Many agricultural areas are contaminated by heavy metals to such a level that the growth of plants is drastically reduced. Based on the site’s specific characteristics, feasibility studies were carried out to choose the most effective technologies. Feasibility tests showed that soil washing and phytoremediation technologies could be used at the agricultural site under study. The efficiency of the technologies is highly dependent on soil characteristics, which determine the chemical form of the metals. The results indicate that water-based soil washing can be successfully used with the possibility of reaching the remediation objectives quickly. However, the technology in the first step essentially breaks down the soil. Moreover, phytoremediation cannot be used directly to overcome the toxicity derived from the very high bioavailability of the heavy metals. Still, there is the need to use “assisted” phytoremediation by adding compost that reduces metal bioavailability, allowing phytoextraction. In this case, a longer time is needed to reach the remediation target. The results provide a preliminary scenario for decision-makers and stakeholders to assess possible technologies applicable and a possible scheme to be applied in similar cases of polluted agricultural areas.

Pollution from numerous contaminants due to many anthropogenic activities affects soils quality. Industrialized countries have many contaminated sites; their remediation is a priority in environmental legislation. The aim of this overview is to consider the evolution of soil remediation from consolidated invasive technologies to environmentally friendly green strategies. The selection of technology is no longer exclusively based on eliminating the source of pollution but aims at remediation, which includes the recovery of soil quality. “Green remediation” appears to be the key to addressing the issue of remediation of contaminated sites as it focuses on environmental quality, including the preservation of the environment. Further developments in green remediation reflect the aim of promoting clean-up strategies that also address the effects of climate change. Sustainable and resilient remediation faces the environmental challenge of achieving targets while reducing the environmental damage caused by clean-up interventions and must involve an awareness that social systems and environmental systems are closely connected.

Phytoextraction is currently investigated to effectively remediate soil contaminated by metals and provide highly competitive biomass for energy production. This research aimed to increase arsenic (As) removal from contaminated soil using industrial Cannabis sativa L., a suitable energy crop for biofuel production. Assisted phytoextraction experiments were conducted on a microcosm scale to explore the ability of two friendly treatments, sodium sulphate (SO4) and exogenous cytokinin (CK), in increasing As phytoextraction efficiency. The results showed that the treatments significantly increased As phytoextraction. Cytokinin was the most effective agent for effectively increasing translocation and the amount of As in aerial parts of C. sativa. In fact, the concentration of As in the shoots of CK-treated plants increased by 172% and 44% compared to untreated and SO4-treated plants, respectively. However, the increased As amount accumulated in C. sativa tissues due to the two treatments negatively affected plant growth. Arsenic toxicity caused a significant decrease in aerial C. sativa biomass treated with CK and SO4 of about 32.7% and 29.8% compared to untreated plants, respectively. However, for our research purposes, biomass reduction has been counterbalanced by an increase in As phytoextraction, such as to consider C. sativa and CK an effective combination for the remediation of As-contaminated soils. Considering that C. sativa has the suitable characteristics to provide valuable resources for bioenergy production, our work can help improve the implementation of a sustainable management model for As contaminated areas, such as phytoremediation coupled with bioenergy generation.

Treating biosolids from industrial, urban, and agricultural plants produces high amounts of water. After organic pollutants and non-essential heavy metals have been removed, these wastewaters are still rich in trace elements such as zinc (Zn), copper, or manganese (Mn) and have high conductivity and extremely variable pH. In this study, an isolated Chlorella sp. strain was grown for 21 days in nutrient solutions enriched with known amounts of Zn or Mn to obtain concentrations three (4.0 mg L−1)- and six (1.0 mg L−1)-fold higher than the basal medium levels, respectively, and over the limits permitted in aquatic environments. The green alga exhibited high tolerance to Zn and Mn, with the maximum abatement of Zn (28–30%) and Mn (60–63.5%) after 14 and 7 days of culture, respectively. Mn stimulated the growth rate and biomass production of Chlorella, which showed the highest carbon levels just in the first week. In both treatments, the nitrogen and protein contents remarkably increased. The photosynthetic pigments increased until the 14th day, with a higher extent in the Zn-enriched solution. An increasing photochemical efficiency was observed after 7 days of treatment, when the microalgae grown in Zn- and Mn-enriched solutions showed a slightly higher maximum photochemical efficiency than control. The autotrophic and controlled growth system adopted was designed to monitor the dynamic balance of Zn and Mn contents in the solutions and in the algal biomass. This system has proved to be useful in identifying the optimal nutritional conditions of the microalgae, along with the optimal temporal patterns of both metal biosorption capacity for water remediation and element bioaccumulation in the algal biomass.

The increasing use of non-renewable resources to supply the growing energy demand has shifted the recent researches towards the development of new sustainable strategies to mitigate the consequent environmental impacts. The use of biomass lignocellulosic as a renewable energy source is among the most widespread solutions to face this problem. However, this practice is subject to further improvement. The new integrated phytoremediation-bioenergy strategy, based on the cultivation of the crops on contaminated soil for energy purposes, could be a possible sustainable solution. The main objective of this methodology is the valorization of biomass produced by phytoremediation systems to provide sustainable energy resources. In this way can be obtained the remediation of contaminated areas simultaneously with bioenergy production. This integrated approach offers an innovative and concrete contribution to the resolution of the current energy problem in full agreement with the sustainability concept

The latest developments in photovoltaic studies focus on the best use of the solar spectrum through Luminescent Solar Concentrators (LSC). Due to their structural characteristics, LSC panels allow considerable energy savings. This significant saving can also be of great interest in the remediation of contaminated sites, which nowadays requires green interventions characterized by high environmental sustainability. This study reported the evaluation of LSC panels in phytoremediation feasibility tests. Three plant species were used at a microcosm scale on soil contaminated by arsenic and lead. The experiments were conducted by comparing plants grown under LSC panels doped with Lumogen Red F305 (BASF) with plants grown under polycarbonate panels used for greenhouse construction. The results showed a higher production of biomass by the plants grown under the LSC panels. The uptake of the two contaminants by plants was the same in both the growing conditions, thus resulting in an increased total accumulation (defined as metal concentration times produced biomass) in plants grown under LSC panels, indicating an overall higher phytoextraction efficiency. This seems to confirm the potential that LSCs have to be building-integrated on greenhouse roofs, canopies, and shelters to produce electricity while increasing plants productivity, thus reducing environmental pollution, and increasing sustainability.

Liquid hydrocarbon pipeline accidents, including leaks due to the illegal or unauthorized collection of petroleum from oil pipelines, are a widespread phenomenon that can lead to pollution that may negatively affect soil quality and plant growth. The aim of this study is to evaluate hydrocarbon uptake and accumulation in Zea mays plants grown on soil affected by spills of fossil fuels. The experiments were conducted in microcosm, mesocosm and field tests. The potential transfer of contaminants from soil to plant and their effects on plant growth were investigated. The results from both the laboratory and field experiments showed that the plants grew better in the uncontaminated soil than in the soil polluted by hydrocarbons. Despite their significantly lower aerial biomass, plants grown in contaminated soil did not show any significant differences in C > 12 concentration, either in shoots or roots, compared to the control plants. Thus, the decrease in plant yield might not be attributed to hydrocarbons accumulation in the plant tissues and may rather be due to a reduced soil fertility, which negatively affected plant growth. Under our experimental conditions, the hydrocarbons present in the contaminated soil were not absorbed by the plants and did not accumulate in plant tissue or in grains, thus avoiding the risk of them entering the food chain. "PHC reduced soil fertility, negatively affecting plant growth. Our findings suggest that PHC in soil were not absorbed by the maize and did not accumulate in its tissues".

Lead (Pb) is one of the most common metal pollutants in soil, and phytoextraction is a sustainable and cost-effective way to remove it. The purpose of this work was to develop a phytoextraction strategy able to efficiently remove Pb from the soil of a decommissioned fuel depot located in Italy by the combined use of EDTA and endophytic bacteria isolated from indigenous plants. A total of 12 endophytic strains from three native species (Lotus cornicolatus, Sonchus tenerrimus, Bromus sterilis) were isolated and selected to prepare a microbial consortium used to inoculate microcosms of Brassica juncea and Helianthus annuus. As for B. juncea, experimental data showed that treatment with microbial inoculum alone was the most effective in improving Pb phytoextraction in shoots (up to 25 times more than the control). In H. annuus, on the other hand, the most effective treatment was the combined treatment (EDTA and inoculum) with up to three times more Pb uptake values. These results, also validated by the metagenomic analysis, confirm that plant-microbe interaction is a crucial key point in phytoremediation.

Mercury is widely distributed throughout the environment. In many contaminated soils other contaminants are present along with mercury; of these, arsenic is one of the most frequently found metals. In the presence of mixed contamination of this kind, remediation technologies must overcome many difficulties due to the different chemical characteristics of the various contaminants. In this study, repeated assisted phytoextraction cycles with Brassica juncea, were conducted on a laboratory scale to evaluate the removal efficiency of mercury and arsenic from a multi-contaminated industrial soil. The possibility of using only one additive, ammonium thiosulphate, to remove mercury and arsenic from co-contaminated soil simultaneously was also investigated. The thiosulfate addition greatly promoted the plant uptake of both contaminants, with an efficiency comparable to that of phosphate specifically used to mobilize specifically arsenic. Repeated additions of mobilizing agents increased metal availability in soil, promoted plant uptake and consequently increased the removal of contaminants in the studied soil. Repeated treatments with thiosulfate increased the concentration of mercury and arsenic in the Brassica juncea aerial part, but due to toxic effects of mercury that reduce biomass production, the total accumulation of both metals in plants tended to decrease at each subsequent re-growth.The use of a single additive to remove both contaminants simultaneously offers several new advantages to phytoextraction technology in terms of reducing cost and time.

A careful waste management system should primarily define the final destination of industrial and urban waste in order to help reduce its environmental impact. Many materials, derived from sewage sludge and industrial production, are characterized by considerable adsorbing capacity; thus, they can be used as low-cost adsorbents to remove heavy metals and organic pollutants from water and soil. The adsorption capacity of these sludge-based adsorbents (SBAs) depends on their specific properties, such as surface area and surface functional groups, which can be enhanced by suitable physical and/or chemical activation. The choice of using alternative and ecofriendly adsorbents is a means of exploiting different varieties of sludge, moving from them being waste-management liabilities toward becoming environmentally sustainable resources.

The phytoremediation efficiency is influenced by contaminant bioavailability in soil, which in turn depends on soil properties. These last, together with rhizosphere processes, regulate the adsorption and release processes of heavy metals in soil.

The problem of high levels of chromium is one of the most important issues in soils of the Mediterranean area, in particular those deriving from ophiolitic parent materials. Very often the chromium concentration is greater than the threshold values of legislation on soil pollution and the knowledge of the origin of contamination (natural or anthropogenic) is important to formulate risk characterization. This study evaluated the soils from three coastal areas of the Cecina Valley (Tuscany, Italy) to understand the origin of chromium in the soils, where high levels of hexavalent chromium were found in well and spring waters of the areas. The main soil characteristics and the correlations among the values of chromium and nickel were determined. Chromium speciation was evaluated by synchrotron radiation X-ray absorption spectroscopy. The results showed the presence of only trivalent chromium in soil and a positive linear correlation between chromium and nickel (e.g. r = 0.76 for the Marina di Bibbona-Bolgheri area), corroborating the hypothesis of a geogenic origin of contamination. This hypothesis was also supported by the low CRI index for the soils with high total Cr content, indicating a higher presence of refractory minerals in the Marina di Bibbona-Bolgheri area than Cecina and Collemezzano areas. The refractory material found in soils was attributed to the presence of ophiolite outcrops in the surroundings and their sedimentary remnants. The weathering of ultramafic-derived constituents and their regional-scale transport are believed to be responsible for the enrichment of chromium and nickel in the investigated soils.

Phytoextraction is a low-cost technology with negligible environmental impacts. A major issue at the field scale is the heterogeneity of contaminant concentration since the entire site needs to be treated evenly even though zones may need different incisiveness in the treatment. The concentration ratio (C-shoot/C-soil) is generally used to evaluate plant species performance and it includes for simplicity an assumption of linearity in the uptake behavior, although deviation from linearity has been observed in several studies. This work describes a phytoextraction feasibility test, conducted at a greenhouse scale for the remediation of an arsenic-contaminated site. Since a feasibility test should also provide an uptake model that accounts for plant growth in heterogeneous areas, the investigation focused on defining the uptake behavior of the various selected species growing in a site with homogeneous soil properties, but with considerable differences in arsenic concentration. Among the many models selectable to describe the soil-to-plant transfer, the Freundlich-like approach was tested. While remaining easy to handle, the non-linear model selected proves to be adequate to predict the arsenic uptake despite the complex contamination considered, thus allowing a more realistic prediction of the potential of a field-scale phytoremediation procedure.

Soil contamination by metals has been a serious problem since the very beginning of the industrial revolution and nowadays causes widespread environmental concern. Most frequently, the results of soil pollution are due to phenomena of co-contamination (multi-metals or organic and inorganic pollutants) that have negative consequences for soil quality and require appropriate solutions for their reclamation. Remediation technologies have often used invasive processes that impact the characteristics of the soil substantially, causing the degradation of this important resource. The simultaneous presence of different metals is very common in MGP sites, and the remediation of these areas is technically demanding and requires suitable interventions at a reasonable cost. A case study is reported to evaluate both biological and nonbiological approaches used at a former MGP site. Two technologies have been compared in order to evaluate the best possible cost-effective strategies for the maintenance of high soil quality. Results suggest the applicability of biological strategies, in this case phytoremediation, thanks to the efficiency achieved with minimal disturbance of surrounding areas.

Since the industrial revolution, soil has been increasingly subjected to continuous negative pressure, largely determined by human activities, which have dispersed heavy metals and many persistent organic compounds causing severe soil contamination. Among pollutants, heavy metals and polycyclic aromatic hydrocarbons (PAHs), which are ubiquitous and generated also from natural resources, are of particular concern. The simultaneous presence of both kinds of pollutants is very common in brownfield sites, and the clean-up of these areas presents technical difficulties and requires appropriate solutions at a reasonable cost. Remediation technologies have often used invasive processes that greatly damage soil characteristics, causing the deterioration of this important resource. In this chapter, the objectives are to briefly examine the processes involved in heavy metal and PAH reactions in soil in order to evaluate the best possible cost-effective remediation strategies for maintaining a high quality of soil and surrounding environment.

Arsenic (As) is recognized as a toxic pollutant in soils of many countries. Since phosphorus (P) and sulphur (S) can influence arsenic mobility and bioavailability, as well as the plant tolerance to As, phytoremediation techniques employed to clean-up As-contaminated areas should consider the interaction between As and these two nutrients. In this study, the bioavailability and accumulation of arsenate in the species Brassica juncea were compared between soil system and hydroponics in relation to P and S concentration of the growth substrate. In one case, plants were grown in pots filled with soil containing 878 mg As kg(-1). The addition of P to soil resulted in increased As desorption and significantly higher As accumulation in plants, with no effect on growth. The absence of toxic effects on plants was likely due to high S in soil, which could efficiently mitigate metal toxicity. In the hydroponic experiment, plants were grown with different combinations of As (0 or 100 μM) and P (56 or 112 μM). S at 400 μM was also added to the nutrient solution of control (-As) and As-treated plants, either individually or in combination with P. The addition of P reduced As uptake by plants, while high S resulted in higher As accumulation and lower P content. These results suggest that S can influence the interaction between P and As for the uptake by plants. The combined increase of P and S in the nutrient solution did not lead to higher accumulation of As, but enhanced As translocation from the root to the shoot. This aspect is of relevance for the phytoremediation of As-contaminated sites.

The capacity of Brassica juncea plants to remediate arsenic-contaminated soil was studied. Thiosulphate and potassium hydrogen phosphate were added to the soil to promote the release of As from soil surfaces, improve the phytoavailability and thus the plant absorption. The addition of thiosulphate and phosphate favoured the growth of the plants and increased the accumulation of arsenic in root and shoots. Assisted phytoextraction is a promising technology for the remediation of As-conaminated sites.

This study examined the capability of thiosulphate and phosphate to promote the release of As from soil surfaces in order to improve the phytoavaillability and thus the absorption of As by Brassica juncea plants.