This paper studies the concentration of Pb, Cd, Hg and As in vegetable and soil of 13 main vegetable base, Chongqing, China, as well as the correlation between them. Results show that the ...concentrations of heavy metals in different vegetables from 13 main vegetable bases of Chongqing are also significantly different. The order of Pb concentration is root vegetable (the average value is 0.203 mg/kg) > leaf vegetable (the average value is 0.065 mg/kg) > solanaceous vegetable (the average value is 0.004 mg/kg); the order of Cd concentration is leaf vegetable (the average value is 0.090 mg/kg) > solanaceous vegetable (the average value is 0.061 mg/kg) > root vegetable (the average value is 0.049 mg/kg); the order of Hg concentration is leaf vegetable (the average value is 0.004 mg/kg) > root vegetable (the average value is 0.003 mg/kg) > solanaceous vegetable (the average value is 0.001 mg/kg); the order of As concentration is root vegetable (the average value is 0.116 mg/kg) > solanaceous vegetable (the average value is 0.057 mg/kg) > leaf vegetable (the average value is 0.026 mg/kg). Significant positive correlation was found between the Cd concentration in vegetables and the Cd concentration in soil, and the linear equation was
y
= 0.065 + 0.012
x
. There was no significant correlation between the concentrations of Pb, Hg and As in vegetables and Pb, Hg and As in soil.
The capability of laccase to oxidate a broad range of polyphenols and aromatic substrates in vitro offers a new technological option for the remediation of polycyclic aromatic hydrocarbon (PAH) ...pollution with high cytotoxicity. However, laccase application in the remediation of PAH-contaminated sites mainly suffers from a low oxidation rate and high cost because of the difficulty in its recovery. In this study, laccases were immobilized on magnetic Fe3O4 particles coated with chitosan (Fe3O4@SiO2-chitosan) to improve the operational stability and reusability in the treatment of PAH pollution. The enzyme fixation capacity reached 158 mg g−1, and 79.1% of free laccase activities were reserved under the optimum immobilized condition of 4% glutaraldehyde, 1.0 mg mL−1 laccase, 2 h covalent bonding time, and 6 h fixation time. The degradation efficiencies of anthracene (ANT) and benzoapyrene (B(a)P) by Fe3O4@SiO2-chitosan immobilized laccase in 48 h were 81.9% and 69.2%, respectively. Furthermore, it is very easy to magnetically recover the immobilized laccase from reaction systems and reuse it in a new batch. The relative activities of immobilized laccase were over 50% for the degradation of ANT and B(a)P in three catalytic runs, reaching the goal of substantially reducing cost in practice. According to the results from quantum calculations and mass spectrum analyses, the degradation products of ANT and B(a)P by laccase were anthraquinone and B(a)P-dione, respectively. The findings from this study provide valuable insight in promoting the application of immobilized laccase technology in the remediation of PAH contamination.
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•Immobilized laccase on magnetic Fe3O4@SiO2-chitosan is of great performance in both operational stability and reusability.•ANT and B(a)P were effectively oxidized by immobilized laccase with degradation efficiencies of 81.9% and 69.2% in 48 h.•The degradation products of ANT and B(a)P by laccase were anthraquinone and B(a)P-dione, respectively.
With low bioaccessbility, persistence of the undissolved organic pollutants in soil and sediments poses threat to health of the resident. Although ubiquitous black carbon catalyzes a wide range of ...biogeochemical reactions in nature, its role in biotransformation of the compounds in non-aqueous phase like 2, 2′-nitrobiphenyl remains unclear. Reduction rate constants of 2, 2′-dinitrobiphenyl by Shewanella oneidensis MR-1 increased from 0.0044 h−1 by 7-fold to 0.035 h−1 in the presence of black carbons produced at pyrolysis temperature of 250–900 °C. Accordingly, electrical conductivity of black carbon was enhanced from 0 to 5.56 S∙cm−1. The reactivity of black carbon for catalyzing the biotransformation positively correlated with its electrical conductivity (R2 > 0.89), which was strongly associated with conductive graphitic clusters in it. The surface oxygenated groups in black carbon were likely not involved in the bioreduction. This work attaches importance to role of the ubiquitous black carbon in natural biotransformation of the undissolved pollutants, and elucidates new mechanism for the biotransformation.
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•Black carbon (BC) promoted bioreduction of undissolved 2, 2′-dinitrobiphenyl.•BC reactivity in bioreduction linearly correlated with its electrical conductivity.•The electrical conductivity was associated with the graphitic structures in BC.•Surface oxygenated moieties in BC were most likely not involved in the reduction.
Microwave irradiation is a promising technology for the remediation of soil contaminated by organic contaminants. However, the roles of volatilization and decomposition in microwave removal of ...polycyclic aromatic hydrocarbons (PAHs) in soil have not yet been quantitatively determined. A model describing the removal efficiency of benz(a)anthracene (BaA) at different treatment times and varied conditions was constructed, wherein BaA removal efficiency was positively and linearly correlated with soil temperature. BaA removal in soil was attributed to thermal volatilization (97.8%) and decomposition (2.2%). Radicals such as ∙OH and ∙O 2- were found to initiate BaA decomposition, the pathway of which was elucidated through HPLC-MS analysis, revealing benz(a)anthracene-7,12-dione as the main intermediate product. The new ideas and perspectives founded in this study offer theoretical support for microwave remediation of organic compound-contaminated sites.
Benzoapyrene (BaP) is a highly carcinogenic organic pollutant. Its distinct toxic effects have raised significant concerns among regulators and researchers. However, the absence of established soil ...environmental criteria for ecological safety of BaP has led to a lack of evidence in the current risk assessment for soil ecological security. To address this gap, we conducted a comprehensive study to investigate the toxicity of BaP using multiple soil organisms, including rice, wheat, lettuce, rape, cucumber, tomato, leonurus, and earthworm. The toxicity data obtained were applied to the species sensitivity distribution (SSD) approach, and the soil environment criteria for ecological safety of BaP under different land use types were derived. The soil environmental criteria for ecological safety of BaP were estimated to be 1.07 (Natural reserve and agricultural land), 1.63 (Parkland), 3.84 (Residential land) and 6.46 (Commercial service and industrial land) mg·kg−1, respectively. This study is the first to conduct toxicity testing and derive soil environmental criteria of BaP in terrestrial ecosystems. These findings are effective supplement for the current soil environmental quality standards and will function as the basis for ecological risk assessment of BaP.
•The test species can be affected under exposure to 0.5 mg·kg−1 BaP.•BaP exhibited lower toxicity to the test plants in soils with high SOM content.•The soil environment criteria of BaP under varying land use types were obtained.
China is the world's largest livestock and poultry breeding country. Heavy metal trace element additives are widely used to prevent animal diseases and promote their growth. China produces ...approximately 3.8 billion tons of livestock and poultry manure annually, and untreated livestock and poultry manure causes a large amount of heavy metal elements to enter the soil environment. Currently, there is limited research on the accumulation of heavy metals in the soil due to the continuous application of livestock and poultry manure, the resulting pollution risk and the negative effects on soil ecology sustainability. This study thoroughly investigated the effects of livestock and poultry manure on the composition and function of soil microbial, and heavy metal resistance genes using 16S and metagene sequencing and 6 years of field experiments. The application of livestock and poultry manure for 6 consecutive years increased the accumulation of zinc (Zn), copper (Cu), mercury (Hg), and chromium (Cr) in the soil at the experimental sites, and cadmium (Cd) and Hg had higher potential risk levels (single potential ecological risk coefficients (Eri) of Hg and Cd were 190.49–336.52 and 385.43–468.52, respectively). Firmicutes and Zoopagomycota were significantly correlated with the soil Zn and Cd contents and pH. After continuous application of manure, the relative abundance of Hg resistance genes (merA) in soil increased by 7.3–8.2 times compared with inorganic feitilizer treatment (IF), and Cu resistance genes (copF and actP) increased by 2.45–5.45 times and 3.8–4.6 times. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt2) and metagenomic function prediction indicated that resistance genes, antioxidant response, and metal output played an important role in heavy metal bioresistance and biotransformation. This work presented heavy metal contents, microbial composition and resistance genes in continuous application of livestock and poultry manure in China, and these data will be of great use in the surveillance, maintenance, and biological removal of heavy metals in manure.
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•Continuous application of manure, soil Cd and Hg had higher potential risk levels.•The relative abundance of soil Mortierella was increased.•Relative abundance of merA and actP was increased by 7.3–8.2 and 3.8–4.6 times.•Resistance genes, etc. played an important role in heavy metal biotransformation.
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•ROX transformation by earthworms reduced the levels of total and available As in soil.•Earthworm gut enhanced ABG-mediated As reduction and methylation in soil.•Gut ABGs decreased ...soil As without enriching host bacterial composition.•The model elucidates the role of gut and soil ABGs in As transformation.
The organoarsenical feed additive roxarsone (ROX) is a ubiquitous threat due to the unpredictable levels of arsenic (As) released by soil bacteria. The earthworms representing soil fauna communities provide hotspots for As biotransformation genes (ABGs). Nonetheless, the role of gut bacteria in this regard is unclear. In this study, the changes in As speciation, bacterial ABGs, and communities were analyzed in a ROX-contaminated soil (50 mg/kg As in ROX form) containing the earthworm Eisenia feotida. (RE vs. R treatment). After 56 d, earthworms reduced the levels of both ROX and total As by 59 % and 17 %, respectively. The available As content was 10 % lower in the RE than in R treatment. Under ROX stress, the total ABG abundance was upregulated in both earthworm gut and soil, with synergistic effects observed following RE treatment. Besides, the enrichment of arsM and arsB genes in earthworm gut suggested that gut bacteria may facilitate As removal by enhancing As methylation and transport function in soil. However, the bacteria carrying ABGs were not associated with the ABG abundance in earthworm gut indicating the unique strategies of earthworm gut bacteria compared with soil bacteria due to different microenvironments. Based on a well-fit structural equation model (P = 0.120), we concluded that gut bacteria indirectly contribute to ROX transformation and As detoxification by modifying soil ABGs. The positive findings of earthworm-induced ROX transformation shed light on the role of As biomonitoring and bioremediation in organoarsenical-contaminated environments.
We have developed a new concept for reversible peptide stapling that involves macrocyclization between two amino groups and decyclization promoted via dual 1,4-elimination. Depending on the trigger ...moiety, this strategy could be employed to selectively deliver peptides to either intracellular or extracellular targets. As a proof of concept, a peptide inhibitor targeting a lysine-specific demethylase 1 (LSD1) was temporarily cyclized to enhance its stability and ability to cross the cell membrane. Once inside the cells, the biologically active linear peptide was released under reducing environment. Moreover, we have developed reversibly stapled peptides using antimicrobial peptides (RStAMPs) whose bioactive helical conformation can be temporarily destabilized by stapling the peptide backbone. The resulting helix-distorted RStAMPs are nontoxic and highly resistant to protease hydrolysis, while at the infection site, RStAMPs can be rapidly activated by the overproduced H2O2 through the dual 1,4-elimination. The latter restored the helical structure of the native peptide and its antimicrobial activity. This work illustrates a highly valuable macrocyclization strategy for the peptide community and should greatly benefit the field of peptide delivery.
Tracing pedogenic processes is fundamental for reconstructing climatic and environmental changes using loess deposits. Lithium isotopes can serve as a sensitive tracer to unravel these processes, ...owing to its active behaviors without effect by redox and biological reactions. This study investigated the Li contents and δ7Li values of leachate and residue (Lileachate, Liresidue, δ7Lileachate and δ7Liresidue) of the upper 12.5 m Luochuan loess-paleosol sediment (since the last interglacial) on the Chinese Loess Plateau, in order to better understand pedogenic processes in loess. The Lileachate, varying from 0.39 to 1.97 μg/g, is mainly derived from the adsorption phase, with a significant variation in δ7Lileachate, from −6.55‰ to +12.88‰. Both Lileachate and δ7Lileachate variations reflect weathering and adsorption processes during different periods. The Liresidue vary from 34.4 to 46.3 μg/g (averaging 38.4 μg/g) and their δ7Liresidue vary from −3.66‰ to +2.44‰ (averaging −0.22 ± 1.68‰), both in agreement with the upper continental crust values. At initial stage after loess deposited (stage I), high Lileachate but low δ7Lileachate are results of preferential adsorption of 6Li by clays and migration of 7Li with soil solution during weathering and eluviation processes. When overlying loess was deposited and experienced pedogenesis as the stage I, 7Li migrated downward and was adsorbed by clays (stage II), resulting in high Lileachate and δ7Lileachate in underlying loess. When loess has superimposed pedogenic and adsorption processes as the stages I and II, loess became as paleosol with highest δ7Lileachate in underlying carbonate accumulation layer. A persistent increase in δ7Lileachate indicates dominant control of post-depositional adsorptions on Li fractionation along solution migrations during weathering and eluviation of overlying deposits, and vice versa. These results highlight that variations in Lileachate and δ7Lileachate can be used to trace soil water migration processes and the magnitude of pedogenic processes in loess-paleosol sediment at different periods.
Naturally occurring cyclic antimicrobial peptides (AMPs) such as tyrocidine A (Tyrc A) and gramicidin S (GS) are appealing targets for the development of novel antibiotics. However, their therapeutic ...potentials are limited by undesired hemolytic activity and relatively poor activity against Gram-negative bacteria. Inspired by polycationic lipopeptide polymyxin B (PMB), the so called ‘last-resort’ antibiotic for the treatment of infections caused by multidrug-resistant Gram-negative bacteria, we synthesized and biologically evaluated a series of polycationic analogues derived from Tyrc A. We were able to obtain peptide 8 that possesses 5 positive charges exhibiting potent activities against both Gram-negative and Gram-positive bacteria along with totally diminished hemolytic activity. Intriguingly, antibacterial mechanism studies revealed that, rather than the ‘pore forming’ model that possessed by Tyrc A, peptide 8 likely diffuses membrane in a ‘detergent-like’ manner. Furthermore, when treating mice with peritonitis–sepsis, peptide 8 showed excellent antibacterial and anti-inflammatory activities in vivo.
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•Totally ten polycationic cyclopeptides derived for Tyrocidine A were synthesized.•Several peptides display broad antibacterial spectrum and very low hemolysis.•Peptide 8 shows excellent antibacterial and anti-inflammatory activities in vivo.•Peptide 8 likely diffuses membrane in a ‘detergent-like’ manner.
