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

Insights Into the Efficiency and Health Impacts of Emerging Microplastic Bioremediation Approaches

The pollution caused by microplastics (MPs) is a global environmental and health concern. These plastic particles disrupt food chains and pose health risks to organisms, including humans. From a total of 827 studies, synthetic textiles (35%) and tires (28%) are the primary sources of MPs, with fibers being the most common shape (60%). MPs were detected in feces (44% of studies), lungs (35%), and blood (17%), indicating widespread contamination and potential health impacts. Bioremediation is a promising and sustainable method for mitigating MP pollution, as it uses microorganisms and plants to break down or convert MPs into less hazardous substances. However, it is important to understand and address the potential unintended consequences of bioremediation methods on the environment and human health. This scoping literature review examines the efficiency of currently emerging approaches for microplastic bioremediation, their strengths and weaknesses, and their potential impacts on the environment and human health. Highly effective methods such as mycoremediation, soil microbes for enhanced biodegradation, and phytoextraction were identified, but they pose high toxicity risks. Moderately effective methods include plant-assisted remediation, rhizosphere degradation, phytodegradation, and biodegradation, with effectiveness rates between 50% and 65% and moderate toxicity risks.

Role of pressmud compost for reducing toxic metals availability and improving plant growth in polluted soil: Challenges and recommendations

Pressmud compost is an organic soil amendment and a robust technology that has potential to restore toxic metals (TMs) polluted soil. The application of organic amendments including pressmud compost in soil for toxic metals (TMs) alleviation have gained considerable attention as compared to traditional methods among the scientific community. In this review paper, we summarized the literature aiming to understand the immobilization efficacy of TMs such as cadmium, lead, chromium, copper, nickel, iron, zinc, and manganese, underlying mechanisms, plant growth, essential nutrients and soil health under pot, field and incubation conditions which has not been well investigated up-to-date. The application of pressmud compost at 10 t ha-1 rate has shown highly potential to reduce the bioavailability and bioaccumulation of TMs in the polluted soil. The immobilization mechanism of TMs in soil depends on soil pH, soil type, cation exchange capacity, hydraulic conditions, nutrients dynamics and soil properties. The application of pressmud compost integrated with biochar, compost, rock phosphate, farmyard manure, bagasse ash, molasses immobilized the cadmium, lead, copper, chromium, nickel and zinc in alkaline polluted soil, whereas pressmud compost combined with poultry manure and farmyard manure increased the bioavailability of lead, cadmium, cobalt, chromium, copper, zinc, iron and manganese in acidic soil, it could be due to aging of pressmud compost, application rate, metal type, nature of soil, particle size, application method, plant type and agronomic practices. There is a lack of knowledge on the phyto-management of arsenic, mercury and boron in soil amended with pressmud compost. Future studies must be focused on potential of pressmud compost co-amended with minerals, modified biochars and nano-material for immobilization of TMs in polluted soil-plant through machine learning/artificial intelligence in order to reduce the health risks and improve public health safety in urban and rural areas.

Assisted phytoextraction as a nature-based solution for the sustainable remediation of metal(loid)-contaminated soils

Soil contamination is a significant environmental issue that poses a threat to human health and the ecosystems. Conventional remediation techniques, such as excavation and landfilling, are often expensive, disruptive, and unsustainable. As a result, there has been growing interest in developing sustainable remediation strategies that are cost-effective, environmentally friendly, and socially acceptable. One such solution is phytoextraction: a nature-based approach that uses the abilities of hyperaccumulator plants to uptake and accumulate metals and metalloids (potentially toxic elements [PTE]) without signs of toxicity. Once harvested, plant biomass can be treated to reduce its volume and weight by combustion, thus obtaining bioenergy, and the ashes can be used for the recovery of metals or in the construction industry. However, phytoextraction has shown variable effectiveness due to soil conditions and plant species specificity, which has led researchers to develop additional approaches known as assisted phytoextraction to enhance its success. Assisted phytoextraction is a remediation strategy based on modifying certain plant traits or using different materials to increase metal uptake or bioavailability. This review article provides a practical and up-to-date overview of established strategies and the latest scientific advancements in assisted phytoextraction. Our focus is on improving plant performance and optimizing the uptake, tolerance, and accumulation of PTE, as well as the accessibility of these contaminants. While we highlight the advantages of using hyperaccumulator plants for assisted phytoextraction, we also address the challenges and limitations associated with this approach. Factors such as soil pH, nutrient availability, and the presence of other contaminants can affect its efficiency. Furthermore, the real-world challenges of implementing phytoextraction on a large scale are discussed and strategies to modify plant traits for successful phytoremediation are presented. By exploring established strategies and the latest scientific developments in assisted phytoextraction, this review provides valuable guidance for optimizing a sustainable, nature-based technology. Integr Environ Assess Manag 2024;20:2003-2022. © 2024 SETAC.

Effective and green in-situ remediation strategies based on TEMPO-nanocellulose/lignin/MIL-100(Fe) hydrogel nanocomposite adsorbent for lead and copper in agricultural soils

Hydrogel adsorbents are promising tools for reducing heavy metals' bioavailability in contaminated soil. However, their practical feasibility remains limited by the low stability, inefficient removal efficiency, and potential secondary pollution. Optimizing the adsorption operation and the functional properties of hydrogel adsorbents could eliminate this method's drawbacks. Herein, three innovative in-situ remediation strategies for Pb/Cu-contaminated soil were adopted based on the concept of novel TEMPO-cellulose (TO-NFCs)/lignin/acrylamide@MIL-100(Fe) nanocomposite hydrogel adsorbent (NCLMH). Characteristic analyses revealed ideal Pb/Cu adsorption mechanisms by swelling, complexation, electrical attraction, and ion exchange via carboxyl/hydroxyl/carbonyl groups and unsaturated Fe(III) sites on ANCMH besides FeOOH formation. The highest maximum theoretical adsorption capacities of Pb(II) and Cu(II) on ANCMH were 416.39 and 133.98 mg/g, under pH 6.5, governed by pseudo-second-order/Freundlich models. Greenhouse pot experiments with contaminated soils amended with two-depth layers of 0.5% NCLMHs (SA@NCLMH) displayed a decline in Pb and Cu bioavailability up to 85.9% and 74.5% within 45 d. Soil column studies simulating continuous water soil flushing coupled with NCLMH layers, instead of conventional extractant fluids, and connected to NCLMH-sand column as purification unit (CF@NCLMH) achieved higher removal rates for Pb, and Cu of 89.5% and 77.2% within 24 h. Alternatively, conducting multiple-pulse soil flushing mode (MF@NCLMH) gained the highest Pb and Cu removal of 96.5% and 85.4%, as the water flushing-stop flux events allowed adequate water movement/residence period, promoting Pb/Cu desorption-adsorption from soil to NCLMH. Also, the NCLMH-sand column conducting and easy separation of the stable/reusable NCLMHs prevented the potential secondary pollution. Interestingly, the three remediated soils reached the corresponding regulation of the permissible limits for Pb and Cu residential scenarios in medium-to-heavily agricultural polluted soils, alleviating the Pb/Cu bioaccumulation and phytotoxicity symptoms in cultivated wheat, especially after MF@NCLMH treatment. This study introduces promising alternative remediation strategies with high sustainability and feasibility in acidic-to-neutral heavy metal-contaminated agricultural soil.

Modern perspectives of heavy metals alleviation from oil contaminated soil: A review

Heavy metal poisoning of soil from oil spills causes serious environmental problems worldwide. Various causes and effects of heavy metal pollution in the soil environment are discussed in this article. In addition, this study explores new approaches to cleaning up soil that has been contaminated with heavy metals as a result of oil spills. Furthermore, it provides a thorough analysis of recent developments in remediation methods, such as novel nano-based approaches, chemical amendments, bioremediation, and phytoremediation. The objective of this review is to provide a comprehensive overview of the removal of heavy metals from oil-contaminated soils. This review emphasizes on the integration of various approaches and the development of hybrid approaches that combine various remediation techniques in a synergistic way to improve sustainability and efficacy. The study places a strong emphasis on each remediation strategy that can be applied in the real-world circumstances while critically evaluating its effectiveness, drawbacks, and environmental repercussions. Additionally, it discusses the processes that reduce heavy metal toxicity and improve soil health, taking into account elements like interactions between plants and microbes, bioavailability, and pollutant uptake pathways. Furthermore, the current study suggests that more research and development is needed in this area, particularly to overcome current barriers, improve our understanding of underlying mechanisms, and investigate cutting-edge ideas that have the potential to completely transform the heavy metal clean up industry.

Recent trends in the phytoremediation of radionuclide contamination of soil by cesium and strontium: Sources, mechanisms and methods: A comprehensive review

This comprehensive review examines recent trends in phytoremediation strategies to address soil radionuclide contamination by cesium (Cs) and strontium (Sr). Radionuclide contamination, resulting from natural processes and nuclear-related activities such as accidents and the operation of nuclear facilities, poses significant risks to the environment and human health. Cs and Sr, prominent radionuclides involved in nuclear accidents, exhibit chemical properties that contribute to their toxicity, including easy uptake, high solubility, and long half-lives. Phytoremediation is emerging as a promising and environmentally friendly approach to mitigate radionuclide contamination by exploiting the ability of plants to extract toxic elements from soil and water. This review focuses specifically on the removal of 90Sr and 137Cs, addressing their health risks and environmental implications. Understanding the mechanisms governing plant uptake of radionuclides is critical and is influenced by factors such as plant species, soil texture, and physicochemical properties. Phytoremediation not only addresses immediate contamination challenges but also provides long-term benefits for ecosystem restoration and sustainable development. By improving soil health, biodiversity, and ecosystem resilience, phytoremediation is in line with global sustainability goals and environmental protection initiatives. This review aims to provide insights into effective strategies for mitigating environmental hazards associated with radionuclide contamination and to highlight the importance of phytoremediation in environmental remediation efforts.

Unlocking the potential of biochar in the remediation of soils contaminated with heavy metals for sustainable agriculture

Agricultural soils contaminated with heavy metals (HMs) impose a threat to the environmental and to human health. Amendment with biochar could be an eco-friendly and cost-effective option to decrease HMs in contaminated soil. This paper reviews the application of biochar as a soil amendment to immobilise HMs in contaminated soil. We discuss the technologies of its preparation, their specific properties, and effect on the bioavailability of HMs. Biochar stabilises HMs in contaminated soil, enhance the overall quality of the contaminated soil, and significantly reduce HM uptake by plants, making it an option in soil remediation for HM contamination. Biochar enhances the physical (e.g. bulk density, soil structure, water holding capacity), chemical (e.g. cation exchange capacity, pH, nutrient availability, ion exchange, complexes), and biological properties (e.g. microbial abundance, enzymatic activities) of contaminated soil. Biochar also enhances soil fertility, improves plant growth, and reduces the plant availability of HMs. Various field studies have shown that biochar application reduces the bioavailability of HMs from contaminated soil while increasing crop yield. The review highlights the positive effects of biochar by reducing HM bioavailability in contaminated soils. Future work is recommended to ensure that biochars offer a safe and sustainable solution to remediate soils contaminated with HMs.

Impacts of climate change on the fate of contaminants through extreme weather events

The direct impacts of climate change involve a multitude of phenomena, including rising sea levels, intensified severe weather events such as droughts and flooding, increased temperatures leading to wildfires, and unpredictable fluctuations in rainfall. This comprehensive review intends to examine firstly the probable consequences of climate change on extreme weather events such as drought, flood and wildfire. This review subsequently examines the release and transformation of contaminants in terrestrial, aquatic, and atmospheric environments in response to extreme weather events driven by climate change. While drought and flood influence the dynamics of inorganic and organic contaminants in terrestrial and aquatic environments, thereby influencing their mobility and transport, wildfire results in the release and spread of organic contaminants in the atmosphere. There is a nascent awareness of climate change's influence of climate change-induced extreme weather events on the dynamics of environmental contaminants in the scientific community and decision-making processes. The remediation industry, in particular, lags behind in adopting adaptive measures for managing contaminated environments affected by climate change-induced extreme weather events. However, recognizing the need for assessment measures represents a pivotal first step towards fostering more adaptive practices in the management of contaminated environments. We highlight the urgency of collaboration between environmental chemists and climate change experts, emphasizing the importance of jointly assessing the fate of contaminants and rigorous action to augment risk assessment and remediation strategies to safeguard the health of our environment.

A review on natural based deep eutectic solvents (NADESs): fundamentals and potential applications in removing heavy metals from soil

Natural based deep eutectic solvent (NADES) is a promising green solvent to replace the conventional soil washing solvent due to the environmental benign properties such as low toxicity, high biodegradability, high polarity or hydrophilicity, and low cost of fabrication process. The application of NADES is intensively studied in the extraction of organic compounds or natural products from vegetations or organic matters. Conversely, the use of the solvent in removing heavy metals from soil is severely lacking. This review focuses on the potential application of NADES as a soil washing agent to remove heavy metal contaminants. Hydrophilicity is an important feature of a NADES to be used as a soil washing solvent. In this context, choline chloride is often used as hydrogen bond acceptor (HBA) whereby choline chloride based NADESs showed excellent performance in the extraction of various solutes in the past studies. The nature of NADES along with its chemistry, preparation and designing methods as well as potential applications were comprehensively reviewed. Subsequently, related studies on choline chloride-based NADES in heavy metal polluted soil remediation were also reviewed. Potential applications in removing other soil contaminants as well as the limitations of NADES were discussed based on the current advancements of soil washing and future research directions were also proposed.

Life cycle assessment and cost-benefit analysis of nature-based solutions for contaminated land remediation: A mini-review

Nature-based solutions (NbS) have gained significant attention as a promising approach for remediating contaminated lands, offering multiple ecosystem services (ESs) benefits beyond pollution mitigation. However, the quantitative sustainability assessment of NbS remediation systems, particularly with regard to post-remediation impacts, remains limited. This mini-review aims to address the existing gaps in the assessment of NbS remediation systems by evaluating the limitations of life cycle assessment (LCA) and cost-benefit analysis (CBA) methodologies. A systematic literature search was conducted resulting in the review of 44 relevant studies published between 2006 and 2023. The review highlights an increasing trend in the coverage in the sustainability assessment literature of NbS remediation systems. Phytoextraction was identified as the main NbS mechanism employed in 65 % of the reviewed works, targeting contaminants such as heavy metals and hydrocarbons. However, the post-remediation aspects, including impacts on ESs and the end-of-life management of NbS biomass, were often neglected in the assessments with only a subset of studies partially exploring such aspects. The findings underscore the need for a comprehensive and integrated approach to assess the sustainability of NbS remediation systems, including the incorporation of economic factors, site-specific considerations, and post-remediation impacts. Addressing these gaps will enhance the understanding of NbS effectiveness and facilitate informed decision-making for contaminated land remediation.

Investigation of water-soil-plant relationships based on hazardous and macro-micro element concentrations on Orontes River, Türkiye

Arundo donax and Phragmites australis were examined in 4 different periods (June and October for 2 years), heavy metal and mineral element accumulations in plants were evaluated, and water-soil-plant relationships were revealed. Element distributions, bioaccumulation factors (BAF) and translocation factors (TF) in different parts of the investigated plant species were also determined. BAFs of elements calculated by using the concentration values in underground parts and sediment samples were between 1.02 and 4.96. While the highest TF was determined as 8.07 for Zn between washed leaf and stem in A. donax, the lowest TF was determined as 0.05 for Fe between stem and underground part. Corresponding highest and lowest TFs for P. australis were 11.80 for Cu between washed leaf and stem, and 0.02 for Fe between stem and underground part, respectively. The results were supported by MANOVA statistical analyzes. Additionally, the macro-micro elements and heavy metal accumulation levels in the parts of the Orontes River ecosystem were significantly higher in the fall periods compared to the spring periods. Our research revealed that the versatile accumulation properties and high accumulation ability of A. donax for Cd, Cr, and Ni and of P. australis for Cd, Co, Cu, Ni, Pb, and Zn.

Nature-Based Solutions for Restoring an Agricultural Area Contaminated by an Oil Spill

A feasibility study is presented for a bioremediation intervention to restore agricultural activity in a field hit by a diesel oil spill from an oil pipeline. The analysis of the real contaminated soil was conducted following two approaches. The first concerned the assessment of the biodegradative capacity of the indigenous microbial community through laboratory-scale experimentation with different treatments (natural attenuation, landfarming, landfarming + bioaugmentation). The second consisted of testing the effectiveness of phytoremediation with three plant species: Zea mays (corn), Lupinus albus (lupine) and Medicago sativa (alfalfa). With the first approach, after 180 days, the different treatments led to biodegradation percentages between 83 and 96% for linear hydrocarbons and between 76 and 83% for branched ones. In case of contamination by petroleum products, the main action of plants is to favor the degradation of hydrocarbons in the soil by stimulating microbial activity thanks to root exudates. The results obtained in this experiment confirm that the presence of plants favors a decrease in the hydrocarbon content, resulting in an improved degradation of up to 18% compared with non-vegetated soils. The addition of plant growth-promoting bacteria (PGPB) isolated from the contaminated soil also promoted the growth of the tested plants. In particular, an increase in biomass of over 50% was found for lupine. Finally, the metagenomic analysis of the contaminated soil allowed for evaluating the evolution of the composition of the microbial communities during the experimentation, with a focus on hydrocarbon- oxidizing bacteria.

Screening of Plants and Indigenous Bacteria to Improve Arsenic Phytoextraction

Arsenic (As) is one of the most common inorganic pollutants; unfortunately, it is also one of the most toxic and is therefore a cause of great concern for the health risks that could result from it. Removing arsenic from the soil using phytoremediation approaches is an effective strategy, and several studies demonstrate the ability of Cannabis sativa (TSN 19109, hemp) to tolerate this harmful contaminant. The aim of this work was to identify the best experimental conditions for a phytoremediation plan to be applied in a disused area located in Sicily (Italy) and contaminated by As, comparing Cannabis sativa with Brassica juncea (TSN 23059) and Zea mays (TSN 42269, corn). To assist the process, several chelating agents were tested to improve arsenic mobility, and two different sets of arsenic-tolerant bacteria were isolated from the rhizospheric soil of indigenous herbaceous species and used to promote plant growth, leading to a significant improvement in terms of biomass produced and phytoextraction. After the combined treatment, the arsenic content in the aerial part of the plants increased by more than two orders of magnitude (e.g., from 0.05 to 6.57 mg kg−1, from 0.04 to 6.69 mg kg−1, and from 0.03 to 5.57 mg kg−1 for brassica, corn, and hemp, respectively), confirming the marked increase in the total absorption of As by plants.