Featured Application The Middle European ecotype of Cd hyperaccumulator Solanum nigrum L. ssp. nigrum was found to show extraordinarily strong tolerance to high contents of Cd in soil (over 50 mg kg-1 Cd) and high Cd accumulation capacity at this concentration range. Its adapted A50 variety obtained from the seeds of first-generation plants grown in soil with 50 mg kg-1 Cd appeared to display further considerable enhancement of resistance to Cd stress, accumulation capacity, and healthy state. This makes the Middle European ecotype and its adapted variety A50 particularly useful to sustainable decontamination of heavily polluted hot spots in degraded post-industrial areas.Abstract The Cd hyperaccumulator Solanum nigrum L. exhibits a cosmopolitan character and proven high and differentiated efficiency. This suggests the possibility of optimizing its Cd phytoremediation capacity and applicability through searching among remote ecotypes/genotypes. However, the extensive studies on this hyperaccumulator have been limited to Far East (Asian) regions. Pioneer pot experiments on the Middle European ecotype of S. nigrum within a concentration range of 0-50 mg kg-1 Cd in soil revealed its Cd phytoremediation capacity to be comparable to Asian ecotypes but with a fundamentally different Cd tolerance threshold. While biomass of the Asian ecotypes declined sharply at Csoil approximate to 10 mg kg-1 Cd, in the Middle European ecotype, a gradual mild biomass decrease occurred within the whole Csoil approximate to 0-50 mg kg-1 Cd range with no toxic symptoms. Its adapted A50 variety was obtained from the seeds of first-generation plants grown in soil with Csoil approximate to 50 mg kg-1 Cd. In this variety, Cd tolerance, accumulation performance, and all physiological parameters (chlorophyll, carotenoids, RuBisCO, and first- and second-line defense anti-oxidant activity) were significantly enhanced, while cell damage by ROS was considerably lesser. This makes the Middle European ecotype and its adapted variety A50 particularly useful to sustainable decontamination of heavily polluted hot spots in degraded post-industrial areas.
Rapid economic development has led to an alarming increase in soil pollution by potentially toxic elements (PTEs), significantly reducing soil productivity and posing long-term threats to sustainable agriculture and human well-being. Over the past two decades, it has been observed that soil PTEs pollution has severely impacted biodiversity, with damage rates of 94.7 % in plants, 77.4 % in humans, and 68.4 % in animals. In response, various remediation technologies have been developed, considering factors such as practical applicability, treatment duration, and ecological safety. Microbial remediation has shown a PTEs removal efficiency ranging from 32.0 % to 95.2 %, while multi-technology combined remediation approaches have demonstrated broader efficacy, with removal rates ranging from 18.7 % to 381 %. However, the selection of a suitable remediation technology must also consider the cost to ensure efficient contaminant removal. This review provides a comprehensive overview of the local and international status, sources, and hazards associated with PTEs, as well as the environmental factors influencing their migration. It also examines the detoxification mechanisms of plants and microbial remediation and evaluates the strengths and weaknesses of physical, chemical, biological, and combined remediation methods. Furthermore, it underscores the requirements and opportunities for developing effective PTEs removal techniques. The insights presented here are crucial for agronomists in developing soil remediation strategies and for interdisciplinary research into integrated emission sources and pathogenesis, thereby enhancing efforts to safeguard the Earth's ecological environment.
Oil pollutants affect the mechanical properties of soils differently. The effect of the kind of oil pollutants on the geotechnical characteristics of a type of soil is an interesting subject that has been examined less in previous studies. The results of this research can be used in designing structures built on soils that are likely to be contaminated with oil pollutants. This study comprehensively investigated the effect of the type of pollutants on the mechanical properties of sandy clay soil to provide the necessary parameters in the remediation plan for soils contaminated with various oil pollutants. A series of laboratory tests, including pH, standard compaction, one-dimensional consolidation, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), falling head permeability, and direct shear, was conducted on the clean and polluted samples. Scanning electron microscopy (SEM) micrographs confirmed that oil pollutants change the soil structure into a flocculated but dispersed one. In addition to the low dielectric constant of oil pollutants, their high viscosity played an important role in altering the geotechnical parameters of clayey sand. The higher the viscosity of the oil pollutant, the higher the maximum dry density (MDD), cohesion coefficient, compression index (Cc), swelling index (Cs), and permeability coefficient of oil-polluted soil. The samples polluted with used motor oil and crude oil, due to their high viscosity, had the greatest drop in compressive strength and shear strength, respectively; whereas the kerosene-polluted sample, due to its low viscosity compared to other oil pollutants, had the greatest rise in compressibility. Thus, in geotechnical plans, special attention should be paid to the bearing capacity and settlement of clayey sand contaminated with crude oil and kerosene, respectively. Oil pollution alters the mechanical properties of soil and poses hazards to the environment.The low dielectric constant and high viscosity of oil pollutants play important roles in changing the properties of soils.Used motor oil greatly reduces the compressive strength of clayey sand, while crude oil and kerosene make the shear stress and settlement of clayey sand more critical, respectively.
With the invasion of heavy metal ions, the electric double layer (DDL) on the surface of cohesive soil particles changes under the influence of heavy metal ions, which leads to significant changes in its physical and mechanical properties. In order to study the variation law of engineering characteristics of heavy metal contaminated soil, three common heavy metal materials, zinc (Zn), lead (Pb) and cadmium (Cd), are selected as pollution additives in this paper. Taking typical silty clay and clay in Nanjing as the research object, through physical property test (boundary moisture content test, particle test) and mechanical property test (direct shear test), The variation law of physical and mechanical indexes of natural cohesive soil polluted by heavy metals is studied, and the influence mechanism of metal ions in heavy metal contaminated soil on engineering characteristics is clarified, which provides a basis for the evaluation method of engineering characteristics of heavy metal contaminated soil.