Synthesis of iron-manganese bimetallic materials supported by activated carbon and application of activated persulfate in the degradation of soil contaminated by crude oil.

Heterogeneous catalytic processes based on zero-valent iron (ZVI) have been developed to treat soil and wastewater pollutants. However, the agglomeration of ZVI reduces its ability to activate persulfate (PS). In this study, a new Fe-Mn@AC activated material was prepared to activated PS to treat oil-contaminated soil, and using the microscopic characterization of Fe-Mn@AC materials, the electron transfer mode during the Fe-Mn@AC activation of PS was clarified. Firstly, the petroluem degradation rate was optimized. When the PS addition amount was 8%, Fe-Mn@AC addition amount was 3% and the water to soil ratio was 3:1, the petroluem degradation rate in the soil reached to the maximum of 85.69% after 96 h of reaction. Then it was illustrated that sulfate and hydroxyl radicals played major roles in crude oil degradation, while singlet oxygen contributed slightly. Finally, the indigenous microbial community structures remaining after restoring the Fe-Mn@AC/PS systems were analyzed. The proportion of petroleum degrading bacteria in soil increased by 23% after oxidation by Fe-Mn@AC/PS system. Similarly, the germination rate of wheat seeds revealed that soil toxicity was greatly reduced after applying the Fe-Mn@AC/PS system. After the treatment with Fe-Mn@AC/PS system, the germination rate, root length and bud length of wheat seed were increased by 54.05%, 7.98 mm and 6.84 mm, respectively, compared with the polluted soil group. These results showed that the advanced oxidation system of Fe-Mn@AC activates PS and can be used in crude oil-contaminated soil remediation.

The collaborative monitored natural attenuation (CMNA) of soil and groundwater pollution in large petrochemical enterprises: A case study.

A large in-service petrochemical enterprises in Northeast China was taken as the research object, and the Collaborative Monitored Natural Attenuation (CMNA) for soil and groundwater pollution was carried out to remedy combined pollution and reduce environmental risks. The pollutants distributions were obtained based on detailed regional investigation (Mar. 2019), and feature pollutants in soil and groundwater were then screened. The spatiotemporal variations of feature pollutants and relative microbial responses were explored during the CMNA process. Furthermore, the CMNA efficiency of the contaminated site at initial stage was evaluated by calculation of natural attenuation rate constant. The results showed that the feature pollutants in soil were 2,2',5,5'-tetrachlorobiphenyl (2,2',5,5'-TCB) and petroleum hydrocarbons (C10∼C40), and the feature pollutant in groundwater was 1,2-dichloroethane (1,2-DCA). The concentrations of all feature pollutants decreased continuously during four years of monitoring. Feature pollutants played a dominant role in the variability of microbial species both in soil and groundwater, increasing the relative abundance of petroleum tolerant/biodegradation bacteria, such as Actinobacteria, Proteobacteria and Acidobacteriota. The average natural attenuation rate constant of 2,2',5,5'-TCB and C10∼C40 in soil was 0.0012 d-1 and 0.0010 d-1, respectively, meeting the screening value after four years' attenuation. The average natural attenuation rate constant of 1,2-DCA was 0.0004 d-1, which need strengthening measures to improve the attenuation efficiency.

Paraliobacillus salinarum sp. nov., isolated from saline soil in Yingkou, China.

A novel Gram-stain-positive, facultatively aerobic, slightly halophilic, endospore-forming bacterium, designated G6-18T, was isolated from saline soil collected in Yingkou, Liaoning, PR China. Cells of strain G6-18T grew at 10-37 °C (optimum, 30 °C), at pH 6.0-9.0 (optimum, pH 8.0) and in the presence of 2-15 % (w/v) NaCl (optimum, 5 %). The strain could be clearly distinguished from the related species of the genus Paraliobacillus by its phylogenetic position and biochemical characteristics. It presented MK-7 as the major quinone and the dominant cellular fatty acids were iso-C16 : 0, anteiso-C15 : 0, C16 : 0 and iso-C14 : 0. The polar lipids consisted of diphosphatidylglycerol and phosphatidylglycerol as the major components. The G+C content of strain G6-18T genome was 35.3 mol%. 16S rRNA analysis showed that strain G6-18T had the highest similarity to Paraliobacillus ryukyuensis DSM 15140T, reaching 97.0 %, followed by Paraliobacillus quinghaiensis CGMCC 1.6333T with a value of 96.3 %. The average nucleotide identity values between strain G6-18T and Paraliobacillus ryukyuensis DSM 15140T, Paraliobacillus sedimins KCTC 33762T, Paraliobacillus quinghaiensis CGMCC 1.6333T and Paraliobacillus zengyii DSM 107811T were 74.3, 72.0, 73.2 and 72.8 %, respectively, and the digital DNA-DNA hybridization values between strain G6-18T and the neighbouring strains were 15.6, 13.8, 14.2 and 14.2 %, respectively. Based on phenotypic, chemotaxonomic and phylogenetic inferences, strain G6-18T represents a novel species of the genus Paraliobacillus, for which the name Paraliobacillus salinarum sp. nov. (=CGMCC 1.12058T=DSM 25428T) is proposed.

[Vibrational assignment analysis of Raman spectra of fatty alcohols].

In the present research, Raman spectra of 31 fatty alcohols were calculated by B3LYP/6-31G (d) and verified by taking methanol for example. The study results indicate that B3LYP/6-31G (d) is an effective approach for the fatty alcohols Raman spectra calculated. The vibrational assignment and Raman spectra features of 6 unbranched alcohols were discussed and the vibrating peaks derived from stretching vibration by C-O were chosen as the research target selection, and the multiple principal component regression models were established and validated with the parameters including polarizability, thermodynamic and energy parameters of the above unbranched alcohols. There exists significant correlation between the vibrating peaks derived from stretching vibration by C-O of fatty alcohols and the parameters (sig. = 0.015). This study will benefit the Raman spectra research of homologs.

Research on Risk Assessment and Contamination Monitoring of Potential Toxic Elements in Mining Soils.

Potentially toxic element (PTE) contamination in soils has serious impacts on ecosystems. However, there is no consensus in the field of assessment and monitoring of contaminated sites in China. In this paper, a risk assessment and pollution monitoring method for PTEs was proposed and applied to a mining site containing As, Cd, Sb, Pb, Hg, Ni, Cr, V, Zn, Tl, and Cu. The comprehensive scoring method and analytical hierarchical process were used to screen the priority PTEs for monitoring. The potential ecological risk index method was used to calculate the risk index of monitoring point. The spatial distribution characteristics were determined using semi-variance analysis. The spatial distribution of PTEs was predicted using ordinary kriging (OK) and radial basis function (RBF). The results showed that the spatial distribution of As, Pd, and Cd are mainly influenced by natural factors, while Sb and RI are influenced by both natural and human factors. OK has higher spatial prediction accuracy for Sb and Pb, and RBF has higher prediction accuracy for As, Cd, and RI. The areas with high ecological risk and above are mainly distributed on both sides of the creek and road. The optimized long-term monitoring sites can achieve the monitoring of multiple PTEs.

Metagenomic analysis reveals specific BTEX degrading microorganisms of a bacterial consortium.

Petroleum hydrocarbon contamination is of environmental and public health concerns due to its toxic components. Bioremediation utilizes microbial organisms to metabolism and remove these contaminants. The aim of this study was to enrich a microbial community and examine its potential to degrade petroleum hydrocarbon. Through successive enrichment, we obtained a bacterial consortium using crude oil as sole carbon source. The 16 S rRNA gene analysis illustrated the structural characteristics of this community. Metagenomic analysis revealed the specific microbial organisms involved in the degradation of cyclohexane and all the six BTEX components, with a demonstration of the versatile metabolic pathways involved in these reactions. Results showed that our consortium contained the full range of CDSs that could potentially degrade cyclohexane, benzene, toluene, and (o-, m-, p-) xylene completely. Interestingly, a single taxon that possessed all the genes involved in either the activation or the central intermediates degrading pathway was not detected, except for the Novosphingobium which contained all the genes involved in the upper degradation pathway of benzene, indicating the synergistic interactions between different bacterial genera during the hydrocarbon degradation.

How newly developed shale gas facilities influence soil erosion in a karst region in SW China.

We already know that the construction of shale gas extraction infrastructure exacerbates soil erosion in vulnerable areas. We are not clear however, about whether the completed well pads and pipelines continue to influence soil erosion after the construction is completed. We applied high-resolution remote sensing images and DEM data from 2014 and 2017 and the Revised Universal Soil Loss Equation (RUSLE) model to calculate how the layout of the well pads and pipelines in a shale gas development area affected soil erosion. We used Geodetector to analyze the factors that affected the soil erosion intensity around the well pads. The results showed that about 0.02% and 0.12% of the total erosion in the shale gas development zone was directly caused by the completed well pads and pipelines in 2014 and 2017, respectively. Most of the erosion was related to the completed pipelines. The completed shale gas well pads affected the soil erosion intensity up to 90 and 60 m from the pads in 2014 and 2017, respectively. The soil erosion around the completed pipelines was mainly from the soil surface over the pipeline and had little effect on the surroundings. The main influences on the soil erosion intensity at different distances from the well pads were land use and slope, and the interactions between them. We suggest that, when developing new shale gas extraction facilities, gas pipelines should be arranged in gently sloping areas, and vegetation should be planted on the bare soil over the pipelines to reduce soil erosion.

Assessing the quality of the soil around a shale gas development site in a subtropical karst region in southwest China.

The construction of shale gas facilities disturbs large areas of land and affects soil quality and function. In this study, we investigated the properties (including physical, chemical, and microbiological indicators) of soil at three different distances from a shale gas development site (<30 m, 30-50 m, and 50-100 m) in a karst area in 2017 and 2020. Our results showed that the soil water content; available carbon, nitrogen, and phosphorus concentrations; total nitrogen and total phosphorus concentrations; microbial biomass, and enzyme activities increased (P < 0.05) as the distance from the well pad increased, and the total carbon content, pH, electrical conductivity, and some ions (magnesium, sodium, and potassium) decreased with distance from the well pad (P < 0.05). The differences in the soil properties were most noticeable in 2017. The increases in the available nutrients were greater than in the total nutrients. The overall soil quality after the shale gas well pad construction was limited by the microbial biomass and sodium contents. The soil properties recovered most quickly at 30-50 m from the well pad, because of local farmland management practices that improved the soil properties and microbial biomass, and reduced the microbial stress. Therefore, we recommend planting sodium-tolerant crops on the land closest to the well pads, to facilitate restoration of the soil that was disturbed during the construction period.

Nitrogen conservation in simulated food waste aerobic composting process with different Mg and P salt mixtures.

To assess the effects of three types of Mg and P salt mixtures (potassium phosphate [K3PO4]/magnesium sulfate [MgSO4], potassium dihydrogen phosphate [K2HPO4]/MgSO4, KH2PO4/MgSO4) on the conservation of N and the biodegradation of organic materials in an aerobic food waste composting process, batch experiments were undertaken in four reactors (each with an effective volume of 30 L). The synthetic food waste was composted of potatoes, rice, carrots, leaves, meat, soybeans, and seed soil, and the ratio of C and N was 17:1. Runs R1-R3 were conducted with the addition of K3PO4/ MgSO4, K2HPO4/MgSO4, and KH2PO4/MgSO4 mixtures, respectively; run R0 was a blank performed without the addition of Mg and P salts. After composting for 25 days, the degrees of degradation of the organic materials in runs R0-R3 were 53.87, 62.58, 59.14, and 49.13%, respectively. X-ray diffraction indicated that struvite crystals were formed in runs R1-R3 but not in run R0; the gaseous ammonia nitrogen (NH3-N) losses in runs R0-R3 were 21.2, 32.8, 12.6, and 3.5% of the initial total N, respectively. Of the tested Mg/P salt mixtures, the K2HPO4/ MgSO4 system provided the best combination of conservation of N and biodegradation of organic materials in this food waste composting process.

Influence of shale gas development on core forests in the subtropical karst region in southwestern China.

Core forests are an important component of forest landscapes and wildlife habitat. Although the core forests were damaged during the development of shale gas sites, it remain unclear how much damage the shale gas development has caused to this ecologically vulnerable region. We analyzed high-resolution remote sensing images of a shale gas development area in 2012, 2014, and 2017 in the karst region in southwestern China. The results showed that the core forest area decreased by approximately 4.0% from 2012 to 2017. Of this decrease, approximately 32.3% was related to the shale gas development activities, while 67.7% was related to other human activities, i.e., agricultural lands and residential developments. Approximately 5.6% of the decrease in the core forest was for new pipelines, with 0.5 ha occurred in 2012-2014 and 248.6 ha occurred in 2014-2017. Of the shale gas development activities, the pipeline constructions were most detrimental to the core forest. The patchiness of the core forest increased by 8.2% from 2012 to 2017 by the expansions of dry fields, towns, and settlements. The core forest Effective Mesh Size (MESH) decreased by 86.3%, primarily caused by the shale gas development pipelines. In conclusion, human activities that were not directly related to shale gas development were the main driver of the core forest decreases. The pipelines caused most losses of the core forest among the shale gas activities and the impacts deteriorated as the shale gas development proceeds. Therefore, we propose that new shale gas pads should be placed adjacent to existing shale gas pipelines and new shale gas pipelines should be constructed in parallel with existing roads to reduce the damages on core forest.

Design of a Microbial Remediation Inoculation Program for Petroleum Hydrocarbon Contaminated Sites Based on Degradation Pathways.

This paper analyzed the degradation pathways of petroleum hydrocarbon degradation bacteria, screened the main degradation pathways, and found the petroleum hydrocarbon degradation enzymes corresponding to each step of the degradation pathway. Through the Copeland method, the best inoculation program of petroleum hydrocarbon degradation bacteria in a polluted site was selected as follows: single oxygenation path was dominated by Streptomyces avermitilis, hydroxylation path was dominated by Methylosinus trichosporium OB3b, secondary oxygenation path was dominated by Pseudomonas aeruginosa, secondary hydroxylation path was dominated by Methylococcus capsulatus, double oxygenation path was dominated by Acinetobacter baylyi ADP1, hydrolysis path was dominated by Rhodococcus erythropolis, and CoA path was dominated by Geobacter metallireducens GS-15 to repair petroleum hydrocarbon contaminated sites. The Copeland method score for this solution is 22, which is the highest among the 375 solutions designed in this paper, indicating that it has the best degradation effect. Meanwhile, we verified its effect by the Cdocker method, and the Cdocker energy of this solution is -285.811 kcal/mol, which has the highest absolute value. Among the inoculation programs of the top 13 petroleum hydrocarbon degradation bacteria, the effect of the best inoculation program of petroleum hydrocarbon degradation bacteria was 18% higher than that of the 13th group, verifying that this solution has the best overall degradation effect. The inoculation program of petroleum hydrocarbon degradation bacteria designed in this paper considered the main pathways of petroleum hydrocarbon pollutant degradation, especially highlighting the degradability of petroleum hydrocarbon intermediate degradation products, and enriching the theoretical program of microbial remediation of petroleum hydrocarbon contaminated sites.

Facile Approach to Fabricate a High-Performance Superhydrophobic Mesh.

When superhydrophobic meshes are used for oil/water separation, high flux and high intrusion pressure are usually compromised. Herein, a high-performance superhydrophobic stainless steel mesh membrane with a hairy-like poly(divinylbenzene) (PDVB) coating is fabricated by precipitated cationic polymerization. The synthesis is facile, which is completed in one step at ambient temperature within a short time, i.e., less than 90 s. The unique hair-like microstructure of PDVB is responsible for the superhydrophobic performance with less blockage for the pores. A higher flux for oil is achieved while keeping a high intrusion pressure. Especially, the ellipsoidal pore texture with two sharp tips can give additional high intrusion pressure. In the case of 2800 mesh, the superhydrophobic mesh displays an unprecedentedly high value of up to 22 kPa while maintaining a high flux of 2.0 × 104 L·m-2·h-1. The high intrusion pressure enables further increment of flux to 4.2 × 104 L·m-2·h-1 under a reduced pressure at a higher loading. The current high-performance superhydrophobic mesh realizes higher efficiency in separating oil/water mixtures, which is promising for practical applications, for example, in industrial extraction.

Temporal changes in vegetation around a shale gas development area in a subtropical karst region in southwestern China.

Over the past decade, various aspects of China's fragile karst environments, including net primary productivity (NPP), have been changed or threatened by shale gas development. This industry is still developing, so it is important to understand what drives environmental changes, particularly in NPP, when shale gas pads are constructed in sensitive areas. Few previous studies have addressed this issue, so we quantified how the NPP changed, and what drove the changes, when a large shale gas area was developed at the end of 2012 in a mountainous karst area in Sichuan Province. We calculated the trend in the normalized difference vegetation index (NDVI) from 2012 to 2017 and used the Carnegie-Ames-Stanford Approach (CASA) model to calculate the changes in NPP at different distances from the pads using remote sensing images for July 2012 and July 2017 and field survey data from July 2017. We then identified the factors that drove the changes with Geodetector. The results showed that the NDVI increased across 64.2% of the shale gas development area from 2012 to 2017 because of climate change, and only showed a significant decrease across 0.3% of the area, mainly because of the shale gas development. The NPP decreased by 110.1 t because of the shale gas development in July 2017, or by about 0.35% of the total NPP. Of this, 93.8 t were associated with the pad construction areas, and 16.3 t were associated with the area around the pads. The changes in NPP around the shale gas pads were mainly confined to within 150 m during the construction phase and 90 m once the construction was completed. The NPP at different distances from the pads during the construction period was related to the distance from the pad, slope, and land use. Once completed, the NPP mainly varied with distance, land use, and the distance from the pad to rural settlements. The NPP was most strongly influenced by the distance from the pad and the area of the pad. We suggest that, when planning the construction of shale gas pads, the pads should be sited on gently sloping areas, the number of wells on each pad should be optimized, land use type changes outside the pad should be limited, and the land beyond the pads should be reclaimed in a timely manner to allow the NPP to recover.

Combined molecular docking, homology modelling and density functional theory studies to modify dioxygenase to efficiently degrade aromatic hydrocarbons.

To promote the biodegradation of aromatic hydrocarbons in petroleum-contaminated soils, naphthalene dioxygenase (NDO), which is the key metabolic enzyme that degrades aromatic hydrocarbons, was modified using molecular docking and homology modelling. The novel NDO enzymes screened can efficiently degrade the target aromatic hydrocarbons naphthalene, anthracene, pyrene and benzo[a]pyrene. The docking showed that the key amino acid residues at the binding site of the NDO enzyme include both hydrophilic residues (Asn201, Asp205, His208, His213, His295 and Asn297) and hydrophobic residues (Phe202, Ala206, Val209, Leu307, Phe352 and Trp358), and the hydrophilic residues were replaced by hydrophobic residues to design 54 kinds of NDO enzyme modification schemes. A total of 14 kinds of novel NDO enzymes designed were found to simultaneously increase the binding affinity to the target aromatic hydrocarbons. The energy barrier and rate constant of the degradation reaction for the NDO enzyme modification were calculated using Gaussian09 software and the KiSThelP program. The novel NDO-7 enzyme exhibited decreases in the energy barrier of 76.28, 26.35, 4.39 and 1.88 kcal mol-1 and increases in the rate constant of 54, 18, 12 and 5 orders of magnitude in the degradation reactions with naphthalene, anthracene, pyrene and benzo[a]pyrene, respectively. These results provide a theoretical basis for the efficient degradation of aromatic hydrocarbons and the modification of their key metabolic enzymes.

In situ formation of DNA-templated copper nanoparticles as fluorescent indicator for hydroxylamine detection.

Herein, we develop a facile method for selective and sensitive detection of hydroxylamine (HA) based on the in situ formation of DNA templated copper nanoparticles (DNA-CuNPs) as fluorescent probes. It is firstly found that HA as a reducing agent can play a key role in the in situ formation of fluorescent DNA-CuNPs. This special optical property of DNA-CuNPs with (λ ex = 340 nm, λ em = 588 nm) with a mega-Stokes shifting (248 nm) makes it applicable for the turn-on detection of HA. In addition, this fluorescent method has several advantages such as being simple, rapid, and environmentally friendly, because it avoids the traditional organic dye molecules and complex procedures. Under optimized conditions, this platform achieves a fluorescent response for HA with a detection limit of 0.022 mM. Especially, successful detection capability in tap waters and ground waters exhibits its potential to be general method.

New evidence for the importance of Mn oxides contributed to nitrobenzene adsorption onto the surficial sediments in Songhua River, China.

Nitrobenzene at a relatively high concentration was reported to cause an environmental pollution event in Songhua River, China in 2005. The adsorption characteristics of nitrobenzene on the surficial sediments (natural surface coatings) were investigated via a selective extraction--adsorption--statistical analysis method. The experimental results show that the changes in the adsorption potential are not always consistent with the variation of particle structure, suggesting that the effect of removal of some components by extraction or separation procedures on the adsorption potential is much greater than that of variation of particle structure. An additional model analysis indicates that not only organic materials but also Fe oxides, Mn oxides and clay minerals contribute much to the adsorption of nitrobenzene. But the adsorption capacity of Mn oxides on a unit mass basis is the highest, and the lowest for clay minerals except for silicate minerals, implying that the role of organic materials and clay minerals in the solid particles contributed to binding of nitrobenzene is less than that of Fe and Mn oxides, especially the later. The new evidence for the higher adsorption potential of nitrobenzene on the surficial sediments (natural surface coatings) and the more importance of Mn oxides contributed to nitrobenzene adsorption is showed in the present study supposing that the adsorption capacity of solid particles can be divided into several fractions.