Specific response of soil properties to microplastics pollution: A review.

The soil environment is a critical component of the global ecosystem and is essential for nutrient cycling and energy flow. Various physical, chemical, and biological processes occur in the soil and are affected by environmental factors. Soil is vulnerable to pollutants, especially emerging pollutants, such as microplastics (MPs). MPs pollution has become a significant environmental problem, and its harm to human health and the environment cannot be underestimated. However, most studies on MPs pollution have focused on marine ecosystems, estuaries, lakes, rivers, and other aquatic environments, whereas few considered the effects and hazards of MPs pollution of the soil, especially the responses of different environmental factors to MPs. In addition, when many MPs pollutants produced by agricultural activities (mulching film, organic fertilizer) and atmospheric sedimentation enter the soil environment, it will cause changes in soil pH, organic matter composition, microbial community, enzyme activity, animals and plants and other environmental factors. However, due to the complex and changeable soil environment, the heterogeneity is very strong. The changes of environmental factors may react on the migration, transformation and degradation of MPs, and there are synergistic or antagonistic interactions among different factors. Therefore, it is very important to analyze the specific effects of MPs pollution on soil properties to clarify the environmental behavior and effects of MPs. This review focuses on the source, formation, and influencing factors of MPs pollution in soil and summarizes its effect and influence degree on various soil environmental factors. The results provide research suggestions and theoretical support for preventing or controlling MPs soil pollution.

The relationships between heavy metals and bacterial communities in a coal gangue site.

Coal is the main source of energy for China's economic development, but coal gangue dumps are a major source of heavy metal pollution. Bacterial communities have a major effect on the bioremediation of heavy metals in coal gangue dumps. The effects of different concentrations of heavy metals on the composition of bacterial communities in coal gangue sites remain unclear. Soil bacterial communities from four gangue sites that vary in natural heavy metal concentrations were investigated using high-throughput sequencing in this study. Correlations among bacterial communities, heavy metal concentrations, physicochemical properties of the soil, and the composition of dissolved organic matter of soil in coal gangue dumps were also analyzed. Our results indicated that Actinobacteriota, Proteobacteria, Chloroflexi, Acidobacteriota, and Gemmatimonadota were the bacterial taxa most resistant to heavy metal stress at gangue sites. Heavy metal contamination may be the main cause of changes in bacterial communities. Heavy metal pollution can foster mutually beneficial symbioses between microbial species. Microbial-derived organic matter was the main source of soil organic matter in unvegetated mining areas, and this could affect the toxicity and transport of heavy metals in soil. Polar functional groups such as hydroxyl and ester groups (A226-400) play an important role in the reaction of cadmium (Cd) and lead (Pb), and organic matter with low molecular weight (SR) tends to bind more to mercury (Hg). In addition to heavy metals, the content of nitrogen (N), phosphorus (P), and total organic carbon (TOC) also affected the composition of the bacterial communities; TOC had the strongest effect, followed by N, SOM, and P. Our findings have implications for the microbial remediation of heavy metal-contaminated soils in coal gangue sites and sustainable development.

Study on Extraction Valuable Metal Elements by Co-Roasting Coal Gangue with Coal Gasification Coarse Slag.

Coal gangue (CG) and coal gasification coarse slag (CGCS) possess both hazardous and resourceful attributes. The present study employed co-roasting followed by H2SO4 leaching to extract Al and Fe from CG and CGCS. The activation behavior and phase transformation mechanism during the co-roasting process were investigated through TG, XRD, FTIR, and XPS characterization analysis as well as Gibbs free energy calculation. The results demonstrate that the leaching rate of total iron (TFe) reached 79.93%, and Al3+ achieved 43.78% under the optimized experimental conditions (co-roasting process: CG/CGCS mass ratio of 8/2, 600 °C, 1 h; H2SO4 leaching process: 30 wt% H2SO4, 90 °C, 5 h, liquid to solid ratio of 5:1 mL/g). Co-roasting induced the conversion of inert kaolinite to active metakaolinite, subsequently leading to the formation of sillimanite (Al2SiO5) and hercynite (FeAl2O4). The iron phases underwent a selective transformation in the following sequence: hematite (Fe2O3) → magnetite (Fe3O4) → wustite (FeO) → ferrosilite (FeSiO3), hercynite (FeAl2O4), and fayalite (Fe2SiO4). Furthermore, we found that acid solution and leached residue both have broad application prospects. This study highlights the significant potential of co-roasting CG and CGCS for high-value utilization.

Differential responses of the properties of soil humic acid and fulvic acid to nitrogen addition in the North China Plain.

Humus (HS) is an important component of soil organic matter. Humic acid (HA) and fulvic acid (FA) are two of the most important components of HS, as they substantially affect biogeochemical processes and the migration and transformation of pollutants in soil. Long-term nitrogen (N) addition can lead to changes in soil physical and chemical properties, affect the structural characteristics of soil HS (HA and FA), cause changes in the adsorption and migration of pollutants, and ultimately result in the continuous deterioration of the soil ecological environment. However, few studies have examined the effects of N addition on the structural characteristics of soil HS, including the responses of soil HA and FA to N addition. Here, we conducted a long-term positioning experiment with different levels of N addition (CK: 0 kg N ha-1 yr-1, LN: 100 kg N ha-1 yr-1, and HN: 300 kg N ha-1 yr-1) in typical farmland soils of the North China Plain to study the response of soil HA and FA to N addition. N addition altered the physical and chemical properties of soil (e.g., pH, SOC, TN, and enzyme activity), which affected the responses of the chemical structure, quality indexes, and composition distribution of soil HA and FA to N addition. Differences in the response to N addition between HA and FA were observed. The structural characteristics of FA were stronger in response to HN compared with those of soil HA. As the level of N added increased, soil FA degradation increased, the composition distribution changed, the aromatization degree and molecular weight decreased, and the molecular structure became simpler. The properties of soil HA did not significantly respond to N addition. Given increases in the global N input (N addition and N deposition), our results have implications for agricultural fertilization, soil management, and other activities.

Removal of Cr(VI) by biochar derived via co-pyrolysis of oily sludge and corn stalks.

The co-pyrolysis of oily sludge with biomass to prepare carbon materials is not only an effective way to mitigate oily sludge pollution, but it is also a method of obtaining carbon materials. In this study, a carbon material (OS-CS AC) was obtained by the direct co-pyrolysis of oily sludge (OS) and corn stalks (CS) and then applied to Cr(VI) removal. According to the hydroxy and carboxy masking experiments and the characterization of OS-CS AC by FT-IR, SEM, XPS, XRD, and N2 physical adsorption-desorption, Cr(VI) can be adsorbed efficiently through pore filling, the surface oxygen-containing functional groups can promote the reduction of Cr(VI) to Cr(III) through electron donors, and the greater the electrostatic attraction between the electron-donating functional groups of OS-CS AC and the Cr(VI) is, the stronger the ability to remove Cr(VI). In addition, the removal process was discussed, and the results indicated that the McKay kinetic model, Langmuir isotherm model and Van't Hoff thermodynamic model were the most suitable models for removal. The main factors affecting the removal of Cr(VI) were discussed, and the removal of Cr(VI) reached 99.14%, which gives a comprehensive utilization way of oily sludge and corn stalks.

Synthesis of Mg-Al Hydrotalcite Clay with High Adsorption Capacity.

A novel Mg-Al metal oxide has been successfully synthesized by the calcination of hierarchical porous Mg-Al hydrotalcite clay obtained by using filter paper as a template under hydrothermal conditions. Various characterizations of the obtained nanoscale oxide particles verified the uniform dispersion of Mg-Al metal oxides on the filter paper fiber, which had a size of 2-20 nm and a highest specific surface area (SSA) of 178.84 m2/g. Structural characterization revealed that the as-prepared Mg-Al metal oxides preserved the tubular morphology of the filter paper fibers. Further experiments showed that the as-synthesized Mg-Al metal oxides, present at concentrations of 0.3 g/L, could efficiently remove sulfonated lignite from oilfield wastewater (initial concentration of 200 mg/L) in a neutral environment (pH = 7) at a temperature of 298 K. An investigation of the reaction kinetics found that the adsorption process of sulfonated lignite (SL) on biomorphic Mg-Al metal oxides fits a Langmuir adsorption model and pseudo-second-order rate equation. Thermodynamic calculations propose that the adsorption of sulfonated lignite was spontaneous, endothermic, and a thermodynamically feasible process.

Characteristics and Environmental Response of White Secondary Mineral Precipitate in the Acid Mine Drainage From Jinduicheng Mine, Shaanxi, China.

The study focuses on the white secondary mineral precipitate and its environmental response formed in acid mine drainage (AMD) at Jinduicheng Mine (Shaanxi, China). The mineral composition of white precipitate was characterized by Scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), X-ray photoelectron spectroscopy (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Inductively coupled plasma-atomic emission spectrometer (ICP-AES), chemical quantitative calculation and PHREEQC software. The white precipitate was a kind of amorphous crystal with the characteristics of a fine powder, and its main elements were O, Al, S, F, OH- and SO42- groups. Moreover, by comparing the mole number of chemical elements, the main mineral composition of the white precipitate was closest to basaluminite. The geochemical simulation result of the PHREEQC software verified that the white precipitate was basaluminite. According to the analysis of water quality characteristics of water samples, basaluminite can reduce the ions content in the AMD and enrich Cu, Ni, Mo, Cr and F ions, showing an excellent self-purification capacity of the water body. These results are helpful to improve the understanding of secondary mineral and its environmental response, and are of great significance for the environmental protection and sustainable development of mining area.

Bioremediation of clay with high oil content and biological response after restoration.

The clay with high oil content form soil lumps, which is hard for microbes to repair. In this paper, the bioaugmentation and biostimulation technology  were applied to improve the bioremediation effect of the soil with high oil content, that modified by local cow dung and sandy soil, the ecological toxicity of the soil after restoration was further analyzed. After 53 days of bioremediation, the degradation efficiency with respect to the total petroleum hydrocarbons (TPH) content reached 76.9% ± 2.2%. The soil bacterial count of M5 group reached log10 CFU/g soil = 7.69 ± 0.03 and the results were better than other experimental groups. The relative abundances of petroleum-degrading bacteria added to M5 remained high (Achromobacter 9.44%, Pseudomonas 31.06%, and Acinetobacter 14.11%), and the proportions of some other indigenous bacteria (Alcanivorax and Paenibacillus) also increased. The toxicity of the bioremediated soil was reduced by seed germination and earthworm survival experiments.

Enhanced Removal of Sulfonated Lignite from Oil Wastewater with Multidimensional MgAl-LDH Nanoparticles.

In this study, hierarchical MgAl-LDH (layered double hydroxide) nanoparticles with a flower-like morphology were prepared under a hydrothermal condition by employing worm-like micelles formed by cetyltrimethylammonium bromide (CTAB) and salicylic acid (SA) as templates. The morphology and structure of the materials were characterized by Brunauer-Emmett-Teller (BET), SEM, and XRD analyses. The performance for the adsorption of sulfonated lignite (SL) was also investigated in detail. FTIR was used to detect the presence of active functional groups and determine whether they play important roles in adsorption. The results showed that the hierarchical MgAl-LDH nanoparticles with a specific surface area of 126.31 m2/g possessed a flower-like morphology and meso-macroporous structures. The adsorption capacity was high-its value was 1014.20 mg/g at a temperature of 298 K and an initial pH = 7, which was higher than traditional MgAl-LDH (86 mg/g). The adsorption process of sulfonated lignite followed the pseudo-second-order kinetics model and conformed to Freundlich isotherm model with a spontaneous exothermic nature. In addition, the hierarchical MgAl-LDH could be regenerated and used, and the adsorption was high after three adsorption cycles. The main adsorption mechanisms were electrostatic attraction and ion exchange between the hierarchical MgAl-LDH and sulfonated lignite.

Temperature-induced changes in the proteome of Pseudomonas aeruginosa during petroleum hydrocarbon degradation.

Petroleum hydrocarbon contaminants, which are among the most serious pollutants in the petroleum industry, can be degraded sufficiently by Pseudomonas aeruginosa. However, temperature-induced stress will severely inhibit this biodegradation. In this study, the proteome of P. aeruginosa P6 at 25 °C, 43 °C and 37 °C was used to examine the impact of temperature on the molecular mechanism of biodegradation of petroleum hydrocarbon by P. aeruginosa P6. Differentially expressed proteins were identified by iTRAQ technology, and the functions of these proteins were identified by bioinformatic analysis. The impact of 25 °C and 43 °C on cellular processes has also been discussed. The results showed that the expression of proteins in chemotaxis toward petroleum hydrocarbons, terminal oxidation of aromatic rings in petroleum hydrocarbons and trans-membrane transport of fatty acids and nutriments were clearly inhibited under 25 °C condition. The expression of proteins in chemotaxis, emulsification, adhesion and terminal oxidation of petroleum hydrocarbons; catalysis of fatty alcohols and fatty aldehydes; trans-membrane transport of nutriments and ß-oxidation were clearly inhibited under 43 °C condition.

The sludge-based adsorbent from oily sludge and sawdust: preparation and optimization.

Sludge-based adsorbent (S-AB) converted by oily sludge can make full use of the precious resource. In this paper, oily sludge and discarded sawdust are used to prepare adsorbent through chemical activation. The adsorbent prepared is used to adsorb raw petroleum. Firstly, the most reasonable chemical activator ZnCl2 is ascertained through parallel comparative experiments. The characterization results of N2-adsorption are consistent with adsorption experiment results, which shows that higher mesopore surface area and volume are benefitted by the adsorption process. Secondly, the optimization of preparation technology is investigated through orthogonal experiments after parallel comparative experiments. The adsorption capacity of S-AB-ZnCl2 is stronger when the preparation conditions are as follows: an activation temperature of 550°C, an activation time of 3.5 h, a solid-liquid ratio of 1:1.5, a sludge-sawdust ratio of 1:0.5 and the heating rate of 15°C/min. The maximum quantity adsorbed Q0 = 434.78 mg/g, calculated through the Langmuir adsorption isothermal models, of S-AB-ZnCl2 prepared under optimized condition is higher than that before optimization. In addition, the most reasonable kinetics fits were of the second-order model.

Synthesis of hierarchical MgO based on a cotton template and its adsorption properties for efficient treatment of oilfield wastewater.

A biomorphic MgO nanomaterial was fabricated via a facile and low-cost immersion method using cotton as the template. The obtained materials were characterized via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and N2 adsorption-desorption analysis. The as-prepared MgO retained the structure of cotton, with a porous hierarchical structure and a high specific surface area, which endowed it with great potential due to its excellent adsorption properties for the adsorption of additives in oil field wastewater. It also exhibited the maximum adsorption capacity of 391.36 mg g-1 for sulfonated lignite. The adsorption process of sulfonated lignite on biomorphic MgO was systematically investigated and was found to obey the pseudo-second-order rate equation and the Langmuir adsorption model. The negative values of Gibbs free energy change (ΔG) showed that the adsorption process was feasible and spontaneous. The endothermic process was depicted with a positive value for ΔH.

Covalently assembled dopamine nanoparticle as an intrinsic photosensitizer and pH-responsive nanocarrier for potential application in anticancer therapy.

We report a novel nanophotosensitizer via one-step covalent assembly of dopamine and genipin. This is the first report unveiling the photodynamic effect of dopamine-based materials. These nanophotosensitizers can also act as pH-responsive drug nanocarriers via a catechol-boronate linkage, thus achieving combined PDT and chemotherapy for highly efficient cancer treatment.

A Global Proteomic Change in Petroleum Hydrocarbon-Degrading Pseudomonas aeruginosa in Response to High and Low Concentrations of Petroleum Hydrocarbons.

In this study, iTRAQ analysis and bioinformatics analysis were used to reveal the changes in key proteins induced by different concentrations of petroleum hydrocarbons during the biodegradation of petroleum hydrocarbons in Pseudomonas aeruginosa P6. Sixty-three proteins were identified as differentially expressed proteins, and all of them were strongly associated with the cellular processes related to the biodegradation of petroleum hydrocarbons. The results further showed that among the differentially expressed proteins, 3 chemotaxis-related proteins, 10 terminal oxidation of short-chain alkane-related proteins, and 13 transmembrane transport-related proteins were down regulated, while 1 uptake of petroleum hydrocarbon-related protein, 3 terminal oxidation of long-chain alkane-related proteins, 4 dehydrogenation-related proteins, 12 ß-oxidation-related proteins, and 2 metabolisms of acyl-CoA-related proteins were up regulated. These results indicated that during the biodegradation of petroleum hydrocarbons in P. aeruginosa P6, the activity of chemotaxis, the terminal oxidation of short-chain alkanes, and transmembrane transport decreased, while the activity of the uptake of petroleum hydrocarbons, the terminal oxidation of long-chain alkanes, dehydrogenation, ß-oxidation, and the metabolism of acyl-CoA increased under the 20,000 mg/L petroleum hydrocarbon condition compared with the 500 mg/L petroleum hydrocarbon condition. The findings revealed changes in the key proteins and the corresponding cellular process of the biodegradation of petroleum hydrocarbons in P. aeruginosa P6 under high and low concentrations of petroleum hydrocarbons and provided references for future studies.

Enhanced Fenton-like oxidation of hydroxypropyl guar gum catalyzed by EDTA-metal complexes in a wide pH range.

A series of EDTA-metal complexes was prepared for the Fenton oxidation catalysts and Fe(II)L exhibits high catalytic performance for degradation of hydroxypropyl guar gum in a wide pH range 7.0-13.0. The viscosity of hydroxypropyl guar gum can be reduced with the 10.0% H2O2 and 5.0% Fe(II)L. The viscosity average molecular weight of hydroxypropyl guar gum was decreased from almost 2 million to 3,199. Most important of all, the chemical oxygen demand (COD) value can be decreased to 104 mg/L from 8,080 mg/L with enough H2O2, and Fe(II)L also shows great catalytic ability in the degradation of various polymers by H2O2. The proposed mechanism of the activation of H2O2 by the complex was studied.

Exploration of Up-regulated Key Proteins in Pseudomonas Aeruginosa for High-efficiency Petroleum Degradation by Proteomic Analysis.

In this work, proteomic analysis was used to identify the up-regulated key proteins of Pseudomonas aeruginosa (P6), a bacteria used in petroleum degradation, responsible for its high efficiency in degrading crude oil. Seventeen proteins were identified as up-regulated proteins by proteomic analysis and classified by bioinformatics analysis. The results indicated that most of the up-regulated proteins were responsible for P. aeruginosa (P6) survival under harsh environmental conditions and utilization crude oil as carbon source in a better way. The physiological processes, chemotaxis to carbon sources, terminal oxidation of carbons, carbon source uptake and nutrients transport, were associated with the up-regulated proteins in the study. The findings revealed the most influential proteins and set a clear direction for future research.

Low-temperature co-pyrolysis behaviours and kinetics of oily sludge: effect of agricultural biomass.

Pyrolysis is potentially an effective treatment of oily sludge for oil recovery, and its kinetics and efficiency are expected to be affected by additives. In the present study, the pyrolysis parameters, including heating rate, final pyrolysis temperature, and pyrolysis time of oily sludge in the presence of agricultural biomass, apricot shell, were systematically explored. As a result, maximum oil recovery is achieved when optimizing the pyrolysis conditionas15 K/min, 723 K, and 3 h for heating rate, final pyrolysis temperature, and pyrolysis time, respectively. Thermogravimetric experiments of oily sludge samples in the presence of various biomasses conducted with non-isothermal temperature programmes suggest that the pyrolysis process contains three stages, and the main decomposition reaction occurs in the range of 400-740 K. Taking Flynn-Wall-Ozawa analysis of the derivative thermogravimetry and thermogravimetry results, the activation energy (Ea) values for the pyrolysis of oily sludge in the presence and absence of apricot shell were derived to be 35.21 and 39.40 kJ mol-1, respectively. The present work supports that the presence of biomass promotes the pyrolysis of oily sludge, implying its great potential as addictive in the industrial pyrolysis of oily sludge.