Display omitted
•MnxOy enhanced MW/PS oxidation is used to remedy pyrene polluted site.•Enhancement effect on pyrene removal by MnxOy is explored.•Radical and non-radical processes both contribute to ...pyrene removal.•Conversion of Mn(IV) to Mn(III) promotes ROS formation and pyrene removal.•Pyrene degradation pathways involve ring-opening and hydroxylation.
Polycyclic aromatic hydrocarbons (PAHs) contaminated sites have attracted worldwide concern due to their carcinogenic, mutagenic, and teratogenic natures. Crystallographic manganese oxides (MnxOy) are ubiquitous in soils. In this study, MnxOy enhanced PAHs contaminated soil remediation in a microwave activated persulfate (MW/PS) system was conducted, and pyrene was selected as a target pollutant. Significant enhancement performance on pyrene removal was observed after adding MnxOy, which ranked as β-MnO2 > α-MnO2 > γ-MnO2 > Mn2O3. Pyrene removal efficiency was enhanced from 65.7% to 85.6% within 15 min of treatment when β-MnO2 dosage increased from 0 to 0.1 g. MnxOy in the MW/PS system improved the production of active substances and converted radical process into non-radical process via conversion of Mn(IV) to Mn(III) and Mn-O-Mn to Mn-O-X. 1O2 played significant roles in pyrene degradation, whereas the presence of β-MnO2 alleviated the shielding effects of SO4− and OH scavengers. Pyrene molecular structures were destroyed, and some ring-opening and/or lower ring byproducts were generated. Residual toxicity of pyrene and its degradation byproducts was predicted. This work provided a potential pathway to promote PAHs contaminated soil remediation via MnxOy enhanced MW/PS oxidation, and highlighted new insights into the mechanism of PS activation by metal oxides.
Globally there are over 20millionha of land contaminated by the heavy metal(loid)s As, Cd, Cr, Hg, Pb, Co, Cu, Ni, Zn, and Se, with the present soil concentrations higher than the geo-baseline or ...regulatory levels. In-situ and ex-situ remediation techniques have been developed to rectify the heavy metal-contaminated sites, including surface capping, encapsulation, landfilling, soil flushing, soil washing, electrokinetic extraction, stabilization, solidification, vitrification, phytoremediation, and bioremediation. These remediation techniques employ containment, extraction/removal, and immobilization mechanisms to reduce the contamination effects through physical, chemical, biological, electrical, and thermal remedy processes. These techniques demonstrate specific advantages, disadvantages, and applicability. In general, in-situ soil remediation is more cost-effective than ex-situ treatment, and contaminant removal/extraction is more favorable than immobilization and containment. Among the available soil remediation techniques, electrokinetic extraction, chemical stabilization, and phytoremediation are at the development stage, while the others have been practiced at full, field scales. Comprehensive assessment indicates that chemical stabilization serves as a temporary soil remediation technique, phytoremediation needs improvement in efficiency, surface capping and landfilling are applicable to small, serious-contamination sites, while solidification and vitrification are the last remediation option. The cost and duration of soil remediation are technique-dependent and site-specific, up to $500ton−1 soil (or $1500m−3 soil or $100m−2 land) and 15years. Treatability studies are crucial to selecting feasible techniques for a soil remediation project, with considerations of the type and degree of contamination, remediation goals, site characteristics, cost effectiveness, implementation time, and public acceptability.
Display omitted
•Various remediation methods have been developed for heavy metal-contaminated soils.•In-situ, contaminant removal/extraction remediation techniques are more favorable.•The methods landfilling, soil washing, and solidification are well established.•Electrokinetic extraction, chemical stabilization, and phytoremediation are immature.•Treatability studies are crucial to selecting feasible soil remediation techniques.
Currently, nanobubbles are widely discussed in environmental research due to their unique properties, including significant specific surface area, transfer efficiency, and free radical generation. In ...this study, O2 and O3 nanobubbles (diameters ranging from 0 to 500 nm) were combined with conventional surfactant technology to investigate their enhanced efficacy in removing diesel contaminants from soil. The impact of various factors such as surfactant concentration, temperature, and soil aging duration on pollutant removal rates was examined across different experimental approaches (stirring/flushing). Soil samples subjected to different treatments were characterized using TG-DTG and FTIR analysis, while GC/MS was employed to assess the degradation products of diesel constituents in the soil. The results indicated that the elution efficiencies of the three surfactants (SDS, SDBS, and TX-100) for diesel in soil correlated positively with concentration (0.3–1.4 CMC) and temperature (18–60 °C), and inversely with aging time (10–300 days), with the elution capacity was SDS > SDBS > TX-100. Mechanical stirring (500 rpm) and temperature variations (18–60 °C) did not affect the stability of the nanobubbles. Upon the introduction of O3 nanobubbles to the surfactant solution, there was a consistent increase in both the removal (degraded and removed) efficiency and rate of diesel under varying experimental conditions, resulting in an enhancement of removal rates by approximately 8–15%. FTIR spectroscopy showed that surfactants containing O3 nanobubbles mitigated the impact on the primary functional groups of soil organic matter. GC/MS analyses indicated that residual pollutants were predominantly alkanes, with degradation difficulty ranking as: alkanes < alkenes < cycloalkanes < aromatic compounds. TG-DTG coupled with GC/MS analysis demonstrated that O3 nanobubbles contributed to a reduction in surfactant residues. This study significantly advances our understanding of how nanobubbles facilitate and optimize surfactant-assisted remediation of contaminated soil, thereby advancing the precise application of nanobubble technology in soil remediation.
Display omitted
•O3 nanobubbles maintain good stability during stirring and temperature changes.•O3 nanobubbles significantly enhance the removal of diesel pollutants by surfactants.•O3 nanobubbles can reduce surfactant residues in soil after washing.
To achieve “production while remediation” in arsenic (As) -contaminated farmlands, a field experiment was conducted to investigate the effects of five Pteris vittata L. (PV) - maize intercropping ...modes on the growth, nutrient, and As accumulation characteristics of PV and maize. The intercropping increased the As content of PV by 2.9%–132.0% and decreased the As content in maize shoots by 15.5%–37.0%. Total As accumulation in above-ground plant parts reached 202.03–941.97 g hm−2. Intercropping also improved nitrogen and phosphorus content in maize kernels by 27.6%–124.7% and 15.9%–31.5%, respectively. Additionally, intercropping increased maize kernel 100-grain weight by 10.0%–16.6% and resulted in a 1.1%–24.1% increase in maize yield compared to sole cultivation. The intercropping transformed soil As from iron-bound to calcium-bound and aluminum-bound forms. Analysis of soil microbial diversity showed that the intercropping decreases the abundance of Chloroflexi and increases the abundance of Proteobacteria. Among the five modes, the intercropping mode with 4 rows of maize and 4 rows of PV showed the highest remediation efficiency and mechanized operation. These findings contribute to a theoretical framework and technical support for the simultaneous soil pollution remediation and productive farming practices.
Display omitted
•Intercropping increased PV's arsenic (As) accumulation while reducing As content in maize.•Intercropping enhanced N and P content in maize kernels, leading to higher 100-grain weight and overall maize yield.•The intercropping mode with wide and narrow rows of maize and interleaved double rows of PV had the highest maize yield.•The intercropping mode with 4 rows of maize and 4 rows of PV showed the highest remediation efficiency.
DDTs (DDT and its metabolites) contaminated sites urgently need to be treated efficiently and greenly. In this study, a horizontal planetary mechanochemical method with co-milling additives was ...developed aiming at efficiently degrading high-concentration DDTs in historical contaminated soil (∼7500 mg/kg). Peroxymonosulfate (PMS) was firstly used to the mechanochemical degradation of DDTs in historical contaminated soil, with a degradation efficiency of over 95% after 1 h of milling under the optimal milling conditions (CR = 30:1, r = 500 rpm, R = 1:4). Mechanism study indicated that DDTs in soil were partially dechlorinated and mineralized. The main products formed might be chlorinated aliphatic hydrocarbons, which need further treatment by ball milling or other methods. Under the action of mechanical energy, PMS could oxidize DDTs in soil through non-radical way rather than common radical way. Then, a comprehensive assessment of this remediation method was conducted by analyzing the changes in soil properties and acute biotoxicity after ball milling. Although PMS had a great performance on the degradation of DDTs, especially p, p’-DDE, it would cause the acidification and salinization of soil. Therefore, further pH adjustment and desalination treatment were suggested to reduce the negative impacts. This work successfully presents a practical approach to mechanochemical remediation of DDTs contaminated sites.
Display omitted
•DDTs was efficiently degraded by PMS assisted mechanochemical method.•PMS degraded DDTs in soil probably through non-radical mechanism.•Comprehensive evaluation of method was carried out based on soil properties.
Both soil erosion and soil contamination pose critical environmental threats to the Chinese Loess Plateau (CLP). Green, efficient and feasible remediation technologies are highly demanded to meet ...these challenges. Herein we propose a unique “soil for soil-remediation” strategy to remediate the heavy metal polluted soil in CLP by converting loess into zeolite for the first time. With a simple template-free route, the natural loess can be converted into cancrinite (CAN) type of zeolite. A highly crystalline CAN was obtained via hydrothermal treatment at 240 oC for 48 h, with a precursor alkalinity of Na/(Si+Al)> 2.0. The as-synthesized CAN zeolite exhibits excellent remediation performance for Pb(II) and Cu(II) polluted soil. Plant assay experiment demonstrates that CAN can significantly restrain the uptake and accumulation of Pb(II) and Cu(II) ions in vegetables, with a high removal efficiency up to 90.7% and 81.4%, respectively. This work demonstrates a “soil for soil-remediation” strategy to utilize the natural loess for soil remediation in CLP, which paves the way for developing green and sustainable remediation eco-materials with local loess as raw materials.
Display omitted
•CAN zeolite was successfully synthesized using natural loess for the first time.•CAN exhibited high feasibility in the remediation of heavy metal contaminated soil.•Up to 90.7% and 81.4% of Pb and Cu in vegetables was removed after CAN remediation.•Both ion exchange and chemical adsorption are responsible for remediation mechanism.
Nanotechnology has shown promising potential to promote sustainable agriculture. This article reviews the recent developments on applications of nanotechnology in agriculture including crop ...production and protection with emphasis on nanofertilizers, nanopesticides, nanobiosensors and nano-enabled remediation strategies for contaminated soils. Nanomaterials play an important role regarding the fate, mobility and toxicity of soil pollutants and are essential part of different biotic and abiotic remediation strategies. Efficiency and fate of nanomaterials is strongly dictated by their properties and interactions with soil constituents which is also critically discussed in this review. Investigations into the remediation applications and fate of nanoparticles in soil remain scarce and are mostly limited to laboratory studies. Once entered in the soil system, nanomaterials may affect the soil quality and plant growth which is discussed in context of their effects on nutrient release in target soils, soil biota, soil organic matter and plant morphological and physiological responses. The mechanisms involved in uptake and translocation of nanomaterials within plants and associated defense mechanisms have also been discussed. Future research directions have been identified to promote the research into sustainable development of nano-enabled agriculture.
Display omitted
•Nanotechnology could promote sustainable agriculture.•Different roles of nanotechnology in agriculture are illustrated.•Comprehensive evaluation of its impacts on soil, plant and environment.•Perspectives on future challenges and opportunities in nano-enabled agriculture.
Cadmium (Cd) is a highly toxic metal released into the environment through anthropogenic activities. Phytoremediation is a green technology used for the stabilization or remediation of ...Cd-contaminated soils. Brassica crop species can produce high biomass under a range of climatic and growing conditions, allowing for considerable uptake and accumulation of Cd, depending on species. These crop species can tolerate Cd stress via different mechanisms, including the stimulation of the antioxidant defense system, chelation, compartmentation of Cd into metabolically inactive parts, and accumulation of total amino-acids and osmoprotectants. A higher Cd-stress level, however, overcomes the defense system and may cause oxidative stress in Brassica species due to overproduction of reactive oxygen species and lipid peroxidation. Therefore, numerous approaches have been followed to decrease Cd toxicity in Brassica species, including selection of Cd-tolerant cultivars, the use of inorganic and organic amendments, exogenous application of soil organisms, and employment of plant-growth regulators. Furthermore, the coupling of genetic engineering with cropping may also help to alleviate Cd toxicity in Brassica species. However, several field studies demonstrated contrasting results. This review suggests that the combination of Cd-tolerant Brassica cultivars and the application of soil amendments, along with proper agricultural practices, may be the most efficient means of the soil Cd phytoattenuation. Breeding and selection of Cd-tolerant species, as well as species with higher biomass production, might be needed in the future when aiming to use Brassica species for phytoremediation.
Display omitted
•Brassica species can be considered a potential candidate for Cd phytoremediation.•Brassica species can accumulate most of the soil Cd in its parts.•Different amendments can be applied to enhance Cd tolerance in Brassica species.•Integrated agricultural practices can be used to enhance Cd uptake in Brassica species.
Across the United States, thousands of hazardous waste sites are contaminated with chemicals that prevent the underlying groundwater from meeting drinking water standards. These include Superfund ...sites and other facilities that handle and dispose of hazardous waste, active and inactive dry cleaners, and leaking underground storage tanks; many are at federal facilities such as military installations. While many sites have been closed over the past 30 years through cleanup programs run by the U.S. Department of Defense, the U.S. EPA, and other state and federal agencies, the remaining caseload is much more difficult to address because the nature of the contamination and subsurface conditions make it difficult to achieve drinking water standards in the affected groundwater.
Alternatives for Managing the Nation's Complex Contaminated Groundwater Sites estimates that at least 126,000 sites across the U.S. still have contaminated groundwater, and their closure is expected to cost at least $110 billion to $127 billion. About 10 percent of these sites are considered "complex," meaning restoration is unlikely to be achieved in the next 50 to 100 years due to technological limitations. At sites where contaminant concentrations have plateaued at levels above cleanup goals despite active efforts, the report recommends evaluating whether the sites should transition to long-term management, where risks would be monitored and harmful exposures prevented, but at reduced costs.
Extensive and inefficient use of pesticides over the last several decades resulted in serious soil and water contamination by imposing severe toxic effects on living organisms. Soil remediation using ...environment-friendly amendments to counteract the presence of pesticides in soil seems to be one suitable approach to solve this problem. Biochar has emerged as a promising material for adsorbing and thus decreasing the bioavailability of pesticides in polluted soils, due to its high porosity, surface area, pH, abundant functional groups, and highly aromatic structure, mainly depending on the feedstock and pyrolysis temperature. However, biochar effects and mechanisms on the sorption and desorption of pesticides in the soil are poorly understood. Either high or low pyrolysis temperature has both positive and negative effects on sorption of pesticides in soil, one by larger surface area and the other by a large number of functional groups. Therefore, a clear understanding of these effects and mechanisms are necessary to engineer biochar production with desirable properties. This review critically evaluates the role of biochar in sorption, desorption, and degradation of pesticides in the soil, along with dominant properties of biochar including porosity and surface area, pH, surface functional groups, carbon content and aromatic structure, and mineralogical composition. Moreover, an insight into future research directions has been provided by evaluating the bioavailability of pesticide residues in the soil, effect of other contaminants on pesticide removal by biochar in soils, effect of pesticide properties on its behavior in biochar-amended soils, combined effect of biochar and soil microorganisms on pesticide degradation, and large-scale application of biochar in agricultural soils for multifunction.
Display omitted
•Dominant biochar properties affecting pesticide sorption-desorption were reviewed.•Biochar effect on pesticide sorption-desorption in the soil was evaluated.•Aging process usually causes lower sorption capacity of biochar.•Modified biochar provides higher sorption efficiency for pesticides.•How biochar affects the biodegradation of pesticides in soils is inconclusive.
PDF
