The composting process from a waste management method to a remediation procedure

Composting is a controlled technology to enhance the natural aerobic process of organic wastes degradation. The resulting product is a humified material that is principally recyclable for agricultural purpose. The composting process is one of the most important tools for waste management, by the European Community legislation. In recent years composting has been increasingly used as a remediation technology to remove biodegradable contaminants from soil, and to modulate heavy metals bioavailability in phytoremediation strategies. An optimization in the recovery of resources from wastes through composting could enhance soil fertility and promote its use in the remediation biotechnologies of contaminated soils

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

Influence of Increasing Tungsten Concentrations and Soil Characteristics on Plant Uptake: Greenhouse Experiments with Zea mays

Tungsten is largely used in high-tech and military industries. Soils are increasingly enriched in this element, and its transfer in the food chain is an issue of great interest. This study evaluated the influence of soil characteristics on tungsten uptake by Zea mays grown on three soils, spiked with increasing tungsten concentrations. The soils, classified as Histosol, Vertisol, and Fluvisol, are characteristic of the Mediterranean area. The uptake of the element by Zea mays was strictly dependent on the soil characteristics. As the pH of soils increases, tungsten concentrations in the roots and shoots of the plants increased. Also, humic substances showed a great influence on tungsten uptake, which decreased with increasing organic matter of soils. Tungsten uptake by Zea mays can be described by a Freundlich-like equation. This soil-to-plant transfer model may be useful in promoting environmental regulations on the hazards of this element in the environment

The Dynamics of Tungsten in Soil: An Overview

The increasing use of tungsten in the production of green energy in the aerospace and military industries, and in many other hi-tech applications, may increase the content of this element in soil. This overview examines some aspects of the behavior of tungsten in soil, such as the importance of characteristics of soils in relation to bioavailability processes, the chemical approaches to evaluate tungsten mobility in the soil environment and the importance of adsorption and desorption processes. Tungsten behavior depends on soil properties of which the most important is soil pH, which determines the solubility and polymerization of tungstate ions and the characteristics of the adsorbing soil surfaces. During the adsorption and desorption of tungsten, iron, and aluminum oxides, and hydroxides play a key role as they are the most important adsorbing surfaces for tungsten. The behavior of tungsten compounds in the soil determines the transfer of this element in plants and therefore in the food chain. Despite the growing importance of tungsten in everyday life, environmental regulations concerning soil do not take this element into consideration. The purpose of this review is also to provide some basic information that could be useful when considering tungsten in environmental legislation

Tungsten Bioaccessibility and Environmental Availability in Tungsten-Spiked Agricultural Soils

Tungsten is an essential element for many cutting-edge industries. Its use is increasing, so much that it has become a “critical element”. With the increase in the use of tungsten, a possible increase in its presence in environmental matrices including soil is expected. In this research, we assessed the environmental availability and bioaccessibility of W in relation to soil properties. Four representative Mediterranean soils, collected in Italy, were spiked with tungsten and incubated for 12 months. In the spiked soils, the environmental availability of the element was determined by the Wenzel sequential extractions. The bioaccessibility was determined by the UBM (BARGE) method in both the gastric and intestinal phases. The findings indicated that the environmental availability is largely influenced by soil properties such as pH and organic matter, while a lower influence was discovered for bioaccessibility, particularly for the gastric phase. These differences could be ascribed to the characteristics of the extractants utilized in the various tests, in particular the pH values. These results could be a valuable reference to integrate with studies on really and not spiked contaminated soils, for the improvement of risk assessments and the development of strategies for remediating soils polluted with tungsten

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

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

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)

Effects of phosphate and thiosulphate on arsenic accumulation in the species Brassica juncea

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 \ub5M) and P (56 or 112 \ub5M). S at 400 \ub5M 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