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Vegetation restoration is a vital ecological remediation technology for greening saline‐alkaline soils. However, little attention is paid to the seasonal changes of soil remediation under different vegetation coverage. This study investigated a recently restored coastal tidal flat located on the island of Zhoushan, by examining shifts in physicochemical properties, enzyme activities, and bacterial communities over 1 year. Soils under Suaeda australis (SUA), Phragmites australis (PHR), Tamarix chinensis (TAM), and two hybrid treatments (SUA+PHR and SUA+TAM) were collected seasonally. Results showed that the seasonal climate variations and vegetation types played important roles in soil physicochemical properties and soil enzyme activities during vegetation restoration. Vegetation could stimulate the activities of soil microbial enzymes, of which PHR‐covered soils exhibited higher catalase activities, higher alkaline phosphomonoesterase activities were observed in summer except for PHR. The combined communities had the highest urease activities in spring and summer, and the highest levels of polyphenol oxidase activity were found in summer or autumn. Furthermore, the bacterial alpha diversity revealed that SUA‐ and SUA+PHR‐covered soils were not markedly affected as the season progressed, whereas PHR and SUA+TAM were characterized by an increase–decrease trend, as well as TAM exhibited highest in autumn. Proteobacteria, Bacteroidetes, Acidobacteria, Actinobacteria, and Chloroflexi were the dominant phyla in each vegetation types. This study deepens our understanding of the effects of halophyte cultivation on coastal ecosystem phytoremediation. [ABSTRACT FROM AUTHOR]

Lead (Pb) is a typical toxic heavy metal element in soils and plants, which has a potential threat to human health through the food chain. Uptake of Pb in the soil–vegetable system has attracted broad attention, whereas reports on the main controlling factors of Pb uptake and accumulation in different soil–vegetable systems are limited. The effect of soil properties on Pb uptake and accumulation in pepper (Capsicum annuum L.) was studied by a pot experiment with 16 typical soils in China. The results showed that the Pb bioavailability was lower in alkaline soils, and that soil cation exchange capacity (CEC), CaCO3, and total phosphorus contents might influence the uptake and transfer of Pb by peppers. Soil pH and CEC were the most significant factors affecting Pb accumulation in pepper fruits. Soil pH was negatively correlated with Pb uptake and accumulation due to its influence on Pb mobility and bioavailability. The accumulation of Pb decreased as soil CEC increased, which might inhibit the absorption and transfer of Pb in peppers. The multiple linear regression function based on soil Pb content, pH, and CEC could provide enough information for a good prediction of the accumulation of Pb in soil–pepper systems (R2 = 0.733). The results are in favor of developing a Pb threshold for vegetables in agricultural soils in China, thus improving the food safety of crops. Environ Toxicol Chem 2021;40:1443–1451. © 2021 SETAC [ABSTRACT FROM AUTHOR]

ABSTRACT A comprehensive feasibility study on the adsorption of Cd2+ ions by cassava starch-based superabsorbent polymers (CST-SAPs) as the biosorbent was investigated as a function of adsorbent dosage, pH, initial concentration, contact time, and temperature. An orthogonal experiment and range analysis were applied to optimize the adsorption conditions. Adsorbent dosage and initial concentration were the most sensitive variables for adsorption capacity. The maximum adsorption value of Cd2+ ions was determined as 347.46 mg/g at pH 6.0, initial concentration of 200 mg/L, and contact temperature and time of 323 K and 6 h, respectively, with 0.1 g adsorbent dosage. The equilibrium data were well described by a Langmuir model, and the adsorption process was well fitted by pseudo-second-order kinetics. The Fourier transform infrared spectroscopy (FTIR) data confirmed that acrylic acid and acrylic amide grafted onto the cassava starch. The X-ray diffraction and FTIR results for the Cd2+-absorbed CST-SAP (CST-SAP-Cd2+) samples showed that the CST-SAP could effectively adsorb Cd2+ ions and that the characteristic groups were translocated by chelation. The scanning electron microscopy results for the CST-SAP revealed that the surface of the polymer was rough, and the layered structure that was full of folds caused an enhanced specific surface; such conditions were beneficial to Cd2+ ion adsorption. It was concluded that the CST-SAP was an excellent adsorbent for Cd2+ ion removal from aqueous solution. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44758. [ABSTRACT FROM AUTHOR]

Natural organic matter (NOM) can interact with engineered nanoparticles (NPs) in the environment and modify their behavior and toxicity to organisms. In the present study, the phytotoxicity of copper oxide (CuO) NPs to rice seedlings in the presence of humic acid as a model NOM was investigated. The results showed that CuO NPs induced the inhibition of root elongation, aberrations in root morphology and ultrastructure, and losses of cell viability and membrane integrity. The adverse effects partly resulted from the generation of reactive oxygen species caused by CuO NPs, which led to lipid peroxidation, mitochondrial dysfunction, and programmed cell death in rice seedlings. However, all the phytotoxicity was alleviated with the addition of humic acid because humic acid coatings on nanoparticle surfaces enhanced electrostatic and steric repulsion between the CuO NPs and the plant cell wall/membrane, reducing contact between NPs and plant and CuO NP-induced oxidative damage to plant cells. The present study's results shed light on the mechanism underlying NP phytotoxicity and highlight the influence of NOM on the bioavailability and toxicity of NPs. Environ Toxicol Chem 2015;34:1996-2003. © 2015 SETAC [ABSTRACT FROM AUTHOR]

Engineered nanoparticles (NPs) and natural organic matter (NOM) in the environment may interact with background contaminants such as heavy metals and modify their bioavailability and toxicity. In the present study, the combined influences of 2 common NPs (TiO2 and CeO2) and humic acid (HA; as a model NOM) on Cu(II) phytotoxicity to rice were investigated by a 3-d root elongation assay performed on filter paper media. The results showed that the adsorption coefficients of bare TiO2 and CeO2 NPs (100 mg/L) toward Cu2+ are 2.65 and 4.37, respectively, at an initial concentration of 10 mg/L, suggesting that Cu(II) could be strongly adsorbed by NPs, whereas HA-coated TiO2 and CeO2 NPs further enhanced the adsorption coefficients to 4.37 and 6.85, respectively. In addition, compared with Cu-alone treatment, the addition of bare TiO2 and CeO2 NPs (1000 mg/L) increased the length of rice root by 32.5% and 39.0%, respectively; however, the presence of HA-coated TiO2 and CeO2 NPs increased the root length by 90.2% and 100.1%, respectively, which indicated that the mitigation effect of HA-coated NPs on Cu(II) phytotoxicity was more visible than that of bare NPs. The results demonstrated that coexistence of NPs and HA significantly alleviated Cu(II) phytotoxicity as a result of a decrease in bioavailable soluble Cu(II) concentration, which contributes to an understanding of the potential behavior of NPs in the environment. Environ Toxicol Chem 2015;34:1588-1596. © 2015 SETAC [ABSTRACT FROM AUTHOR]