Ammonium thiosulphate assisted phytoextraction of mercury and arsenic in multi-polluted industrial soil

The possibility of using ammonium thiosulphate in assisted phytoextraction was evaluated on a greenhouse scale (mesocosm) for the simultaneous removal of mercury and arsenic from multi-polluted industrial soil. The addition of thiosulphate to the soil greatly promoted the uptake and translocation of both contaminants in the aerial parts of Brassica juncea and Lupinus albus. Thiosulphate showed great potential since it is a common fertilizer used to promote plant growth and is able to promote plant uptake of both Hg and As. Hg concentration in the aerial part of the plants reached 867 mg kg-1 in B. juncea and 114 mg kg-1 in L. albus. In the aerial parts, As concentration was about 9 mg kg-1 in B. juncea and 20 mg kg-1 in L. albus. This thus increases the applicability of phytoextraction in terms of cost and time especially if the remedial targets are based on bioavailable metal concentrations

Soil Remediation: Towards a Resilient and Adaptive Approach to Deal with the Ever-Changing Environmental Challenges

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. \u201cGreen remediation\u201d 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

Genotoxic effects of Boron contaminated sediments from Cecina basin (Tuscany) on Vicia faba L

In this work a Boron contaminated sediment from the Cecina basin in Tuscany (Italy) was considered for its possible genotoxic effects on plants. The greatest part of Cecina basin is located in the geothermal zone of Larderello, where for about a hundred years the mine activities in this area and more recently the geothermoelectric industry spilled in the Possera and Pavone creeks (tributaries of Cecina river) until about 1975. However, contamination is still present in certain areas of the basin with high level of B

Genotoxicity study on Vicia faba L. grown on natural and spiked contaminated soils

Genotoxicity study on Vicia faba L. grown on natural and spiked contaminated soil

Phosphate-assisted phytoextraction in as-contaminated soil

In this paper, the effect of phosphate on As phytoextraction was examined. The effect of phosphate on As dissolution, the As uptake of plants, the internal plant translocation, and phytotoxic effect were investigated. Lupine plants were grown on As-contaminated soil collected from an industrial site containing 670 mg/kg As and were treated with biammonium phosphate (BAP). Two different BAP application procedures were tested: single-dose and multiple split additions. BAP was found to be effective in increasing the water-soluble As concentration in the test soil. As the concentration of water-soluble As increased, the Lupine plants responded accordingly with an increased As uptake. The As content in the shoots and the translocation factor were the highest when BAP was added in multiple split additions. On the contrary, a single application caused the highest As content in the roots and consequently the lowest translocation factor. In addition, it was established that the single-application method significantly reduced the plant biomass by twofold, this reduction being an evident phytotoxic symptom. Measurements of the combined biomass production and As content values revealed that the highest As phytoextraction is obtained with BAP applied in multiple doses which is about 14-fold higher than in the control plants, whereas a single-dose BAP application increased the phytoextraction rate only 1.6 times. These results demonstrate that significant improvements in the current phosphate-assisted phytoextraction of As could be achieved

Improvement of Arsenic Phytoextraction Using Indigenous Bacteria and Mobilizing Agents

Among inorganic contaminants, arsenic (As) is known for its toxicity and the risks to the environment and human health that could derive from its presence. Phytoremediation represents an effective strategy for the removal of arsenic from contaminated soil, provided that suitable plant species and adequate operational plans are exploited. With reference to a disused area located in Southern Italy which was the subject of a previous study, in this work, new strategies were investigated to further improve the effectiveness of a phytoremediation plan for the removal of arsenic. The usefulness of Cannabis sativa (hemp) and Zea mays (corn) was evaluated in this work by microcosm (300 g of mixed soil per test) and mesocosm (4 kg of mixed soil + 1 kg of inert gravel per test) experiments. The addition of arsenic-tolerant bacteria isolated from the rhizosphere of native herbaceous species grown in the contaminated soil was employed to promote plant growth, while different mixtures of mobilizing agents were tested to improve arsenic bioavailability. After the combined treatment, the arsenic content in the aerial parts of the plants increased by about 10 times in the case of corn (from 1.23 to 10.41 mg kg−1) and by about 8 times in the case of hemp (from 1.05 to 8.12 mg kg−1)

Improvement of Arsenic Phytoextraction Using Indigenous Bacteria and Mobilizing Agents

Among inorganic contaminants, arsenic (As) is known for its toxicity and the risks to the environment and human health that could derive from its presence. Phytoremediation represents an effective strategy for the removal of arsenic from contaminated soil, provided that suitable plant species and adequate operational plans are exploited. With reference to a disused area located in Southern Italy which was the subject of a previous study, in this work, new strategies were investigated to further improve the effectiveness of a phytoremediation plan for the removal of arsenic. The usefulness of Cannabis sativa (hemp) and Zea mays (corn) was evaluated in this work by microcosm (300 g of mixed soil per test) and mesocosm (4 kg of mixed soil + 1 kg of inert gravel per test) experiments. The addition of arsenic-tolerant bacteria isolated from the rhizosphere of native herbaceous species grown in the contaminated soil was employed to promote plant growth, while different mixtures of mobilizing agents were tested to improve arsenic bioavailability. After the combined treatment, the arsenic content in the aerial parts of the plants increased by about 10 times in the case of corn (from 1.23 to 10.41 mg kg−1) and by about 8 times in the case of hemp (from 1.05 to 8.12 mg kg−1)

Protocols for Applying Phytotechnologies in Metal-Contaminated Soils

Contamination with heavy metals continues to pose a serious challenge for the remediation of polluted soil, as they are not degradable and must be physically removed. At present, most technologies used for removing heavy metals from the soil greatly affect the biogeochemical characteristics of the soil. In many cases, the soil can no longer be considered a useful and productive soil resource, and the treated soil has to be disposed of in landfills. Phytoremediation is the only solution that approaches the problem from an eco-sustainable point of view—it is environmentally friendly and relatively cheap. In this chapter, two phytotechnology approaches for remediating heavy metal-contaminated soil will be discussed, along with protocols for their implementation: phytoextraction and phytostabilization. Phytoremediation as a technique for rehabilitating heavy metal-polluted land therefore requires protocols and decision-support tools to assess the most appropriate approach, based on site-specific characteristics and requirements for soil status during and after remediation. Decisions have to be made on whether to use phytoextraction or phytostabilization, or even reject phytoremediation as a whole. Protocols and decision tools, from modeling and laboratory tests to full-blown feasibility studies, will be discussed

Overcoming limitation of “recalcitrant areas” to phytoextraction process: The synergistic effects of exogenous cytokinins and nitrogen treatments

The aim of the present work was to test the efficiency of the phytoextraction process involving the use of exogenous phytohormone (cytokinins, CKs) and fertilizer (nitrogen, N) treatments in phytotechnologies to address risk management in “recalcitrant areas”. The CKs and N treatments, alone or combined (CKs + N) in a Modulated Application (MA), were tested on the crop plant Helianthus annuus, common to Mediterranean area, fast growing and with high biomass production. Plants were grown on boron (B) contaminated sediments (collected from a geothermal area located in Tuscany (Italy). Plant growth, B uptake, together with plant stress parameters were investigated. Boron is easily taken up and translocated by some crop plants, but the high phytotoxicity can dramatically impact the plant growth and consequently the applicability and efficiency of the phytoextraction process. As indicators of plant stress, oxidative balance and photosynthetic parameters were investigated to give a deeper insight of phytotoxic mechanisms. Results showed that while each treatment (CKs and N alone) had significantly positive effects on plant health, the MA treatment provided a synergistic effect on morphological parameters and biomass production as a whole. After MA treatment, plants showed antioxidant activity comparable to that of the control (unpolluted sediments) and showed an increase of net photosynthesis. Moreover, our data showed very high values of B uptake and translocation (about 800 mg kg−1 in shoots), without any alteration triggered by the treatments (CKs and N alone or combined in MA). B phytoextraction resulted increased about fivefold with the MA treatments, while each treatment alone increased only two or three folds when treated with either CKs or N. The MA treatment is not “contaminant specific”, so it could be applied in other “recalcitrant areas” where different types of contaminations occur, in order to overcome limitations of plant growth

Effect of Soil Aging on Cadmium Bioavailability and Bioaccessibility at a Contaminated Site

The effect of aging on cadmium (Cd) bioavailability and bioaccessibility was investigated in naturally aged field soil within a contaminated site. The results, which are based on a comparison of investigations carried out in 2018 and 2022 on the same soil samples, provide a realistic evaluation of the variation in Cd chemical forms due to long-term aging. The data obtained show a significant reduction (from approximately 30% to 60%) in the mobile and bioavailable forms of cadmium, while the total quantity in soil did not change significantly. The effect of aging on the bioavailable fractions is also reflected in the reduction in the amount of the metal absorbed by plants. On the one hand, this indicates a reduction in the potential contamination of the food chain, while on the other, it highlights the limitations of the use of phytoextraction as a clean-up technology in this specific site. In the case under study, it should also be noted that there was no decrease in cadmium bioaccessibility over time, which remained very high even after four years of cadmium aging in the soil, which was about 60% of the total content in the most contaminated soil samples. This highlights the potential health risks related to the incidental ingestion of Cd-contaminated soil, which could become the main exposure route in the case of the final use of the site as a park or public green area