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1.
J Hazard Mater ; 471: 134404, 2024 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-38688217

RESUMO

The influence of organic carbon on the proliferation of antibiotic resistance genes (ARGs) in the soil has been widely documented. However, it is unclear how soil organic carbon (SOC) interacts with the evolution of antibiotic resistance in bacteria. Here, we examined the variations in ARGs abundance during SOC mineralization and explored the microbiological mechanisms and key metabolic pathways involved in their coevolution. The results showed that the SOC mineralization rate was closely correlated with ARGs abundance (p < 0.05). High organic carbon (OC) mineralization was conducive to the occurrence of multidrug resistance genes. For example, multidrug_transporter and mexB increased 2.26 and 7.83 times from the initial level. The competitor (stress) evolutionary strategy model revealed that higher OC inputs drive environmental microorganisms to evolve from stress tolerant to high resistance and strong adaptation. Meta-genomic and transcriptomic analyses revealed that the conversion process of pyruvate to acetyl-CoA to acetate was the critical metabolic pathway for the co-regulation of antibiotic resistance. Gene deletion validation trials have demonstrated that the key functional genes (ackA and pta) involved in this process can modulate the development of vancomycin and multidrug resistance. This outcome provides a preliminary framework for microbial mechanisms that target the co-regulation of microbial OC conversion and the evolution of antibiotic resistance.


Assuntos
Carbono , Microbiologia do Solo , Solo , Carbono/metabolismo , Carbono/química , Solo/química , Bactérias/metabolismo , Bactérias/genética , Bactérias/efeitos dos fármacos , Antibacterianos/farmacologia , Resistência Microbiana a Medicamentos/genética , Genes Bacterianos
2.
J Environ Manage ; 346: 118981, 2023 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-37742563

RESUMO

The removal of antibiotic resistance genes (ARGs) in sewage is of great concern, but advanced sewage treatment technologies are not suitable for rural areas, so the multi-layer soil infiltration system (MSL) has been developed for rural sewage treatment. However, little is known about the performance and function of MSL in the treatment of ARGs in rural sewage. Here, we optimized the matrix composition and structure of MSL and explored the efficacy and mechanism of MSL systems for ARG removal under different hydraulic conditions. The ARGs removal rate of MSL ranged from 41.51% to 99.67%, in which MSL with the middle hydraulic load, high pollution load, and continuous inflowing conditions showed the best removal performance. In addition, this system can operate stably and resist the temperature fluctuation, which showed an equivalent removal rate of ARGs in warm and cold seasons, amounting to 69.0%. The structural equation model revealed that microorganisms in sewage could significantly affect ARG removal (path coefficient = 0.91), probably owing to their interspecies competition. As for the internal system, the reduction of ARGs was mainly driven by microorganisms in the system matrix (path coefficient = 0.685), especially soil-mixture-block (SMB) microorganisms. The physicochemical factors of the matrix indirectly reduce ARGs by affecting the microorganisms that adhere to the matrices. Note that the pairwise alignment of nucleotide analysis demonstrated that the system matrix, especially biochar in the SMB, adsorbed ARGs and their hosts from the sewage, and in turn eliminated them by inhibiting the spread and colonization of hosts, thereby reducing the abundance of ARGs. Collectively, this study provides a deeper insight into the removal of ARGs from rural sewage by MSL, which can help improve sewage treatment technologies.

3.
Bioresour Technol ; 385: 129443, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37399957

RESUMO

The effects of microbial inoculants on ARG removal in composting are poorly understood. Here, a co-composting method for food waste and sawdust amended with different microbial agents (MAs) was designed. The results show that the compost without MA unexpectedly achieved the best ARG removal. The addition of MAs markedly increased the abundance of tet, sul and multidrug resistance genes (p < 0.05). Structural equation modeling demonstrated that MAs can enhance the contribution of the microbial community to ARG changes by reshaping community structure and altering the ecological niche, causing the proliferation of individual ARGs, an effect related to the MA component. Network analysis revealed that inoculants weakened the correlation between ARGs and community but increased the linkage between ARGs and core species, suggesting that inoculant-induced ARG proliferation may correspond with gene exchange occurring mainly between core species. The outcome provides new insights into MA application for ARG removal in waste treatment.


Assuntos
Inoculantes Agrícolas , Compostagem , Eliminação de Resíduos , Antibacterianos/farmacologia , Inoculantes Agrícolas/genética , Genes Bacterianos/genética , Alimentos , Esterco , Resistência Microbiana a Medicamentos/genética
4.
Bioresour Technol ; 384: 129334, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37328014

RESUMO

The effect of microbial agents (MA) on hydrogen sulfide (H2S) emissions in the compost is still a controversial issue. This study examined the effects and microbial mechanisms of MA on H2S emissions during the composting of kitchen waste. The results showed that MA addition can promote sulfur conversion to elevate H2S emissions by approximately 1.6 âˆ¼ 2.8 times. Structural equations demonstrated that microbial community structure was the dominant driver on H2S emissions. Agents reshaped the compost microbiome, showing more microorganisms participated in sulfur conversion, and enhanced the connection between microorganisms and functional genes. The relative abundance of keystone species associated with H2S emissions increased after adding MA. Particularly, the sulfite and sulfate reduction processes were intensified, as evidenced by an increasing in the abundance and pathways cooperation of sat and asrA after MA addition. The outcome provides deeper insights into MA on regulating the mitigation of H2S emissions in compost.


Assuntos
Compostagem , Sulfeto de Hidrogênio , Microbiota , Enxofre , Sulfitos , Solo/química
5.
Sci Total Environ ; 874: 162522, 2023 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-36868270

RESUMO

Despite the role of microorganisms in nitrogen biotransformation has been extensively explored, how microorganisms mitigate NH3 emissions in the transformation of nitrogen throughout the composting system is rarely addressed. The present study explored the effect of microbial inoculants (MIs) and the contribution of different composted phases (solid, leachate, and gas) on NH3 emissions by constructing a co-composting system of kitchen waste and sawdust with and without the addition of MI. The results showed that NH3 emissions increased markedly after adding MIs, in which the contribution of leachate ammonia volatilization to NH3 emissions was most prominent. The core microorganisms of NH3 emission had a clear proliferation owing to the MIs reshaping community stochastic process. Also, MIs can strengthen the co-occurrence between microorganisms and functional genes of nitrogen to promote nitrogen metabolism. In particular, the abundances of nrfA, nrfH, and nirB genes, which could augment the dissimilatory nitrate reduction process, were increased, thus enhancing NH3 emissions. This study bolsters the fundamental, community-level understanding of nitrogen reduction treatments for agricultural.


Assuntos
Inoculantes Agrícolas , Compostagem , Compostagem/métodos , Amônia/análise , Solo , Nitrogênio/análise , Esterco
6.
Sci Total Environ ; 876: 162856, 2023 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-36931524

RESUMO

Bacterial resistance to antibiotics has become a widespread concern, and poses serious environmental and global health problems. Lots of studies have demonstrated that engineered nanoparticles (NPs) can significantly affect bacterial antibiotic resistance; however, whether NPs promote or inhibit antibiotic resistance remains a complex and well-debated issue. This will constrain environmental antibiotic resistance gene contamination and clinical bacterial resistance problems, resulting in unclear and poorly targeted treatment efficacy. To better understand the relationship between NPs and antibiotic resistance, this review systematically summarizes and reanalyzes published data on the effect of NPs on bacterial antibiotic resistance and related mechanisms. The effects of intrinsic properties of NPs, such as size, concentration, functional groups, and extrinsic properties of NPs on the development of antibiotic resistance were dissected. This review will provide a better understanding of the effects of increasingly released NPs in different environments on bacterial resistance and underlines the direction for employing NPs to control the dissemination of antibiotic resistance genes in the environment. Next, how NPs affect intracellular and extracellular antibiotic resistance needs in-depth exploration. Besides, alternative treatments of NPs and antibiotics in therapy will be a future trend for combating antibiotic resistance, and the follow-up emphasis should determine their dose effects and potential mechanism. This study will expand our understanding of the biosafety of nanomaterials and provides a theoretical reference to guide the proper application of nanomaterials or technologies to environmental pollution control and clinical treatment.


Assuntos
Infecções Bacterianas , Nanopartículas , Humanos , Farmacorresistência Bacteriana/genética , Antibacterianos/farmacologia
7.
J Environ Sci (China) ; 127: 361-374, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-36522068

RESUMO

Chinese government is vigorously promoting toilet renovation in rural areas to reduce the risk of human feces exposure, which would cause infectious diseases, especially antibiotic resistance genes (ARGs) and pathogens. However, the distribution of ARGs in human feces from different regions of China remained ill-defined. It is not yet known how the survival of ARGs after toilet treatment is associated with the regional infection rates. Here, we investigated the prevalence of ARGs in human feces in rural areas of China and their potential relationship with infectious diseases for the first large-scale. The results showed that there were still high ARGs residues in human feces after rural toilet treatment, especially tetM-01 and ermB with average relative abundance as high as 1.21 × 10-1 (Eastern) and 1.56 × 10-1 (Northern), respectively. At a large regional scale, the significant differences in human feces resistomes were mainly shaped by the toilet types, TN, NH3-N, and the bacterial community. A critical finding was that toilets still cannot effectively decrease the pathogenicity risk in human feces. The significant positive relationship (P<0.05) between infectious diseases and ARGs can infer that ARGs in human feces exposure might be a critical path for enhancing the incidence of diseases, as these ARGs hinder the effectiveness of antibiotics.


Assuntos
Antibacterianos , Doenças Transmissíveis , Humanos , Genes Bacterianos , Saneamento , Incidência , China/epidemiologia
8.
J Hazard Mater ; 437: 129322, 2022 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-35728320

RESUMO

Biomass amendments have numerous benefits in reducing antibiotic resistance genes (ARGs) in the soil environment. However, there are debatable outcomes regarding the effect of raw biomass and its pyrolytic biochar on ARGs, and the exploration of the influence mechanism is still in infancy. Herein, we investigated the changes in soil ARGs under the organic fertilizer application with coconut shell and its biochar. The results showed that the coconut shell biochar could effectively diminish ARGs, with 61.54% reduction in target ARGs, which was higher than that adding raw coconut shells (p < 0.05). Structural equation modeling indicated that ARGs were significantly affected by changes in environmental factors, mainly by modulating bacterial communities. Neutral community model and network analysis demonstrated that the coconut shell biochar can restrict the species dispersal, thereby mitigating the spread of ARGs. Also, coconut shell biochar exhibited strong adsorption, with a large specific surface area (476.66 m2/g) and pores (pore diameter approximately 1.207 nm, total pore volume: 0.2451 m3/g), which markedly enhanced soil heterogeneity that created a barrier to limit the resistant bacteria proliferation and ARGs propagation. The outcome gives an approach to control the development of ARGs after organic fertilizer application into soil.


Assuntos
Fertilizantes , Solo , Antibacterianos/farmacologia , Bactérias/genética , Carvão Vegetal/farmacologia , Cocos , Resistência Microbiana a Medicamentos/genética , Fertilizantes/análise , Genes Bacterianos , Solo/química , Microbiologia do Solo
9.
J Environ Manage ; 317: 115382, 2022 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-35623127

RESUMO

Organic fertilizer increase antibiotic resistance genes (ARGs) and bacterial pathogens have widely documented. However, how organic fertilizer is involved in changing soil ARGs and pathogenic bacteria after long-term (≥5 years) application remains unclear. Herein, the ARGs and pathogenic bacteria were compared in organic fertilized soils (AF) and non-fertilized soils (NF), and the contribution of input sources (organic fertilizer, irrigation water, air and background soil) on soil ARGs also was determined in this study. Results showed that the abundances of some ARGs, such as vanR and aac(6')-I in AF, were significantly higher than these of NF (p < 0.05). And a relatively higher abundance of potential pathogens, especially, Salmonella enterica and Stenotrophomonas maltophilia, in AF was observed. This indicated that organic fertilizer application can maintain a high level of some soil ARGs and pathogenic bacteria for at least 5 years. Traceability analysis unearthed that organic fertilizer application mainly increased its own contribution to soil ARGs from 1.16% to 9.05%, as well reduced the contribution of background soil, suggesting that the increase in soil ARGs may be partly attributable to organic fertilizer inputs. Notably, organic fertilizer application did not significantly alter the contribution ratio of input sources to microorganisms, but there was a clear change in the composition of soil microorganisms, which meant that the effect of the input source on the microorganism may emanate from other factors, rather than direct inputs. Subsequent structural equation demonstrated that organic fertilizer application significantly enhanced the effect of environmental factors on ARGs, and also indirectly increased the influence of communities on ARGs. Collectively, under the long-term fertilization, the role of organic fertilizers on soil ARGs not just stems from its own input, and also dominates the influence of environmental factors on ARGs. This study elucidates main causes for the difference in ARGs in AF vs. NF and enlightens actual role of organic fertilizer in them.


Assuntos
Fertilizantes , Solo , Antibacterianos/análise , Antibacterianos/farmacologia , Bactérias , Fertilizantes/análise , Genes Bacterianos , Esterco/microbiologia , Solo/química , Microbiologia do Solo
10.
J Environ Manage ; 312: 114912, 2022 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-35306420

RESUMO

Solving the problem of rural sewage is considered an essential task in China's rural revitalization strategy. Based on the yearbook data of sewage treatment in rural areas between 2014 and 2019, although the rate of sewage treatment in rural areas of China showed an upward trend, it was still below 35%, mainly due to the lack of suitable sewage treatment technologies. Here, we discuss the multi-soil-layering (MSL) system, which is an emerging technology suitable for rural sewage treatment. It was deemed to overcome the shortcomings of current biological and ecological treatment technologies, such as complex operation, large area, and high operating costs. We used system dynamics to evaluate the advancing and limiting factors of MSL application for rural sewage treatment from the social, environmental, and economic dimensions. The results illustrated a complete causal loop diagram in which essential variables and relationships were concentrated in the technology, operation and maintenance, and satisfaction of farmers. The efficiency of MSL is the key variable affecting the final decision of the MSL application. Overall, using MSL to treat rural sewage could be an option to improve the rural environment in China. However, the scientific technological model for MSL should be further explored. This review provides guidance on how to promote MSL systems in rural areas.


Assuntos
Esgotos , Solo , China
11.
Environ Res ; 203: 111884, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34400159

RESUMO

The prevalence of bacterial resistance caused by the application of animal manure has become an important environmental issue. Herein, the vertical migration of antibiotic resistance genes (ARGs) and pathogens in soil and vegetables after the application of different fertilizers was explored. The results showed that the application of composted manure considerably enhanced the abundance of most ARGs and pathogens, especially in surface soil and pakchoi roots. Moreover, the soil ARGs increased partially from log 1.93 to log 4.65 after the application of composted manure, and six pathogens were simultaneously detected. It was observed that the increase in soil depth decreased most ARGs and pathogens by log 1.04-2.24 and 53.98 %~85.54 %, respectively. This indicated that ARGs and pathogens still existed in the deep soil (80-100 cm). Moreover, total organic carbon had a significant influence on the pathogen distribution, whereas bacterial communities primarily drove the vertical migration of ARGs rather than environmental factors. Although most of the ARG-host associations observed in the surface soil were disappeared in deep soil as revealed by network analysis, some co-occurrence pattern still occurred in deep soil, suggesting that some ARGs might be carried to deep soil by their host bacteria. These results were novel in describing the vertical migration of ARGs in the environment after the application of different fertilizers, providing ideas for curbing their migration to crops.


Assuntos
Fertilizantes , Solo , Animais , Antibacterianos , Fertilizantes/análise , Genes Bacterianos , Esterco , Microbiologia do Solo , Verduras
12.
J Environ Manage ; 304: 114293, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-34915385

RESUMO

Although composting techniques are continuously optimised and adjusted, the removal of bacterial pathogen based on the quality of composting products needs further to ensure safe of agricultural use. In this study, we combined aerobic composting and anaerobic process to determine the optimal combination (turning frequency of once a day, the proportion of swine manure to corn straw (3:1), and mixed 6-day anaerobic process) that benefits the reduction of bacterial pathogens, among which the maximum removal efficiency of up to 92.96% was observed for Clostridium_sensu_stricto_1 reached, thereby improving the quality of the compost products. The variation partition analysis and redundancy analysis indicated that physicochemical factors such as temperature, TOC, and pH significantly affected the removal of bacterial pathogens. Therefore, the additive effects of physicochemical factors on bacterial pathogen removal requires further process optimisation. These findings offer powerful technological support for improving agricultural waste recycling and enhancing the safety of fertiliser application.


Assuntos
Compostagem , Anaerobiose , Animais , Bactérias , Esterco , Solo , Suínos , Virulência
13.
J Environ Manage ; 300: 113709, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34547574

RESUMO

Improved sanitation is critical important to reduce the spread of human deposited pathogens and antibiotic resistance genes (ARGs). In the China's rural "Toilet Revolution", three-compartment septic tanks (SPTs) are widely used as household domestic sewage treatment facilities. The effluents of SPTs are encouraged to be used as fertilizer in agriculture. However, whether SPT could eliminate fecal pathogens and ARGs is still unrevealed which is crucial in risk assessment of SPT effluent utilization. Herein, we employed metagenomic sequencing to investigate the pathogens and ARGs in rural household SPTs from Tianjin, China. We found that rural household SPT effluents conserved pathogens comparable to that of the influents. A total of 441 ARGs conferring resistance to 26 antibiotic classes were observed in rural household SPTs, with the relative abundance ranging from 709 to 1800 ppm. Results of metagenomic assembly indicated that some ARG-MGE-carrying contigs were carried by pathogens, which may pose risk to human and animal health after being introduced to the environment. This study raises the question of SPTs as sustainable on-site treatment facilities for rural domestic sewage and underscores the need for more attention to the propagation and dissemination of antibiotic-resistant pathogens from SPT to the environments, animals, and humans.


Assuntos
Bactérias , Genes Bacterianos , Animais , Bactérias/genética , Resistência Microbiana a Medicamentos/genética , Humanos , Metagenômica , Esgotos
14.
Bioresour Technol ; 341: 125746, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34438286

RESUMO

How to effectively dispose of rural solid waste has become one of the important issues that need to be solved urgently in China. A simplex centroid design was utilized to optimize four-component mixed composting (swine manure, human feces, rice straw and kitchen waste). 24 different runs were conducted to compost based on the mixture design. Three response models (2 special cubic and 1 quadratic) were successfully developed and validated by analysis of variance. It turns out that all models have a very high R2 value ranging from 94.76 to 98.81%. The global solution of the mixture optimization predicted the optimal value of 0.879, in a blend consisting of 41.4% swine manure, 13.7% human feces and 44.9% rice straw. That was considered to be the best combined proportion of mixed composting. This result is instructive for the efficient treatment and resource utilization of solid wastes in rural areas.


Assuntos
Compostagem , Oryza , Animais , Esterco , Solo , Resíduos Sólidos , Suínos
15.
Environ Sci Pollut Res Int ; 28(32): 43842-43852, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33840021

RESUMO

Recent studies on the microbial community composition of human excrement after rural household toilet treatment are unclear regarding the effects and risks of using recycled products as fertilizers in agriculture. In this study, we used Illumina high-throughput sequencing to investigate the microbial community structure of the excrement from 50 Chinese rural household toilets on a spatial scale, and we evaluated the impact of select geochemical factors on the bacterial and fungal communities in the human excrement. Multivariate analysis showed that there was a significant spatial differentiation of the human excrement in microbial communities after all toilet treatments. Twenty dry toilet samples and thirty septic tank samples had similar bacterial (Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes) and fungal phyla (Ascomycota and Basidiomycota), differing only in the proportions of the microorganisms. For both dry toilet samples and septic tank samples, the pH and ammonium nitrogen were found to be the major driving forces affecting the changes in bacterial community structures (p<0.05), while there was no correlation found for the fungal community with environmental factors in China (p>0.05), except in the northern regions, where the total phosphorus was found to be significantly correlated with the fungal community (p<0.05). Network analysis confirmed that NH4+-N had the most significant impact on the content of pathogens. Certain pathogens were still detected after toilet treatment, such as Streptococcus, Bacteroides, Aspergillus, and Chrysosporium, and the proportion of potential pathogenic bacteria in dry toilets was higher than that in septic tanks, suggesting that septic tanks were better than dry toilets in treating human excrement. These results provide an ecological perspective for understanding the large-scale geographic distribution of household excrement microbial communities in rural areas and for improving human excrement treatment technologies and avoiding the risks of agricultural applications.


Assuntos
Aparelho Sanitário , Microbiota , Micobioma , Bactérias , China , Humanos , Solo , Microbiologia do Solo
16.
J Environ Manage ; 289: 112576, 2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-33865023

RESUMO

The increasing prevalence of antibiotic resistance genes (ARGs) in the soil environment poses a serious threat to crop safety and even public health. In this study, the fate of ARGs in the soil was investigated during the growth period of pakchoi and after harvesting with the application of different kinds of fertilizers. The result showed that increasing rate of soil ARGs during the growth period of pakchoi followed the order of composted manure > commercial fertilizer > mineral fertilizer. After harvesting, soil ARGs abundance treated with mineral fertilizer, commercial fertilizer or composted manure significantly increased by 0.63, 3.19 and 8.65 times (p < 0.05), respectively, compared with the non-fertilized soil. The ARGs abundance in the pakchoi treated with composted manure was significantly higher than that of treatments with mineral fertilizer and commercial organic fertilizer. These findings indicated the application of composted pig manure would significantly increase the pollution load of ARGs in farmland soil and plant, and also promote the proliferation of farmland ARGs. Principal component analysis suggested that bacterial communities might have a significant influence on ARGs changes during the growth period of pakchoi. Network analysis further indicated ARGs changes may be mainly related to their host bacteria (including Gammaproteobacteria, Flavobacteriia and Bacilli). The results provided a proper method and useful information on reducing transmission risk of ARGs and control the propagation of ARGs in agricultural activities.


Assuntos
Fertilizantes , Solo , Animais , Antibacterianos/farmacologia , Resistência Microbiana a Medicamentos/genética , Fazendas , Fertilizantes/análise , Genes Bacterianos/genética , Esterco , Microbiologia do Solo , Suínos
17.
Environ Sci Pollut Res Int ; 28(27): 35751-35763, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33675496

RESUMO

Elevated CO2 levels may alleviate toxicities induced by environmental stresses in plants, such as heavy metals. To assess this possibility, seedlings of Lolium perenne L. were exposed to different Cd stress and CO2 levels during hydroponic culture. The kinetics of growth, Cd accumulation, and thiol formation were investigated. Elevated CO2 levels increased the growth rate from 30 to 75%, and decreased the Cd accumulation rate from 36 to 42%, leading to a decrease of Cd content in root and shoot. However, an increase in Cd transport from root to shoot was observed at elevated CO2 under Cd stress. The production of phytochelatins (PCs) occurred earlier at elevated CO2 level than at ambient CO2 level after exposure to Cd stress. The mean SH/Cd ratio was relatively higher at elevated CO2 level, but elevated CO2 level significantly decreased thiol contents. The reduction of Cd contents, earlier production of PCs, and relatively higher SH/Cd ratio at the elevated CO2 level alleviated Cd toxicity in root and shoot to some extent, causing significant yield increase of L. perenne after exposure to Cd stress. This study could provide an important data support and theoretical basis in understanding the effects of elevated CO2 on plant growth, heavy metal accumulation, and thiol formation.


Assuntos
Lolium , Poluentes do Solo , Cádmio/análise , Dióxido de Carbono/análise , Glutationa , Cinética , Fitoquelatinas
18.
Huan Jing Ke Xue ; 42(4): 1649-1659, 2021 Apr 08.
Artigo em Chinês | MEDLINE | ID: mdl-33742800

RESUMO

The characteristics of the VOCs species in foundry industries based on the production processes were analyzed through gas chromatography-mass spectrometry (GC-MS) after sampling the emissions of VOCs in 9 typical foundry enterprises using air packages and absorption tubes. The source profiles of the VOCs species in foundry industries based on production processes were established for the first time in China. In addition, the emission characteristics of VOCs and the contribution of VOCs emitted by various production processes to ozone generation were also studied. The results showed that the characteristic components of the VOCs in foundry industries were predominantly aromatic hydrocarbons, halogenated hydrocarbons, and oxygenated hydrocarbons. The average concentrations were 50.9%, 20.8%, and 12.6%, respectively. In general, aromatic hydrocarbons, such as toluene, benzene, and m/p-xylene; halogenated hydrocarbons, such as trichloroethylene and dichloromethane; oxygenated hydrocarbons, such as acetone, ethyl acetate, cyclopentanone, and some alkanes, were the primary VOCs species of the foundry industries. The emission characteristics of different production processes were related to the solvents and surface treating agents used by each process. The results also demonstrated that painting was the largest contributor of VOCs concentrations among all the production processes, followed by the modeling procedure and the silica sol and pouring processes. The OFP values for the different production processes ranged from 0.29-96.09 mg·m-3. Painting was the largest contributor to OFP, followed by the modeling procedure and the melting and pouring processes. Aromatic hydrocarbons and oxygenated hydrocarbons were the dominant contributors to OFP, and 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, toluene, and m/p-xylene were the main active components in the foundry industry, with a total contribution to the ozone generation potential of nearly 60%. It is suggested that the painting process should be prioritized regarding control measures to reduce its emissions and impact, while the waste gas from the modeling procedure and the melting and pouring processes should be collected efficiently and treated properly before being discharged to the environment.

19.
Bioresour Technol ; 325: 124710, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33493747

RESUMO

Single aerobic or anaerobic composting is reportedly as inefficient for removing antibiotic resistance genes (ARGs) from animal manure. This study investigates the effects of ARG removal during aerobic combined with anaerobic composting (ACA) under different conditions. The results showed that a turning frequency of once a day, the proportion of swine manure and corn straw (3:1) and an anaerobic time of 6 days were the best operating conditions for ARG reduction (>95%, especially ermF: 99.78%) during ACA. Moreover, redundancy analysis demonstrated that the bacterial community (especially Truepera, Petrimonas and Ureibacillus) had a stronger effect on ARG removal than environmental factors did (especially temperature, total phosphorus, ammonia nitrogen and pH). Network analysis indicated the important effect of these potential host bacteria on the spread of ARGs through significant co-occurrence between individual ARGs and specific bacteria. These findings offer an effective technology to reduce and block ARGs spread from animal manure.


Assuntos
Compostagem , Anaerobiose , Animais , Antibacterianos/farmacologia , Resistência Microbiana a Medicamentos/genética , Genes Bacterianos , Esterco , Suínos
20.
Molecules ; 25(14)2020 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-32650504

RESUMO

In order to improve the mechanical and dielectric properties of radome cyanate, a synergistic reinforcement method is employed to develop a resin-based ternary-composite with high heat-resistance and preferable radar-band transmission, which is expected to be applied to fabricate radomes capable of resisting high temperature and strong electric field. According to copolymerization characteristics and self-curing mechanism, epoxy resin (EP) and bismaleimide (BMI) are employed as reinforcements mixed into a cyanate ester (CE) matrix to prepare CE/BMI/EP composites of a heat-resistant radome material by high-temperature viscous-flow blending methods under the catalysis of aluminum acetylpyruvate. The crystallization temperature, transition heat, and reaction rate of cured polymers were tested to analyze heat-resistance characteristics and evaluate material synthesis processes. Scanning electron microscopy was used to characterize the micro-morphology of tensile fracture, which was combined with the tensile strength test and dynamic thermomechanical analysis to investigate the composite modifications on tenacity and rigidity. Weibull statistics were performed to analyze the experimental results of the dielectric breakdown field, and the dielectric-polarization and wave-transmission performances were investigated according to alternative current dielectric spectra. Compared with the pure CE and the CE composites individually reinforced by EP or BMI, the CE/BMI/EP composite acquires the most significant amelioration in both the mechanical and electrical insulation performances as indicated by the breaking elongation and dielectric breakdown strength being simultaneously improved by 40%, which are consistently manifested by the obviously increased transverse lines uniformly distributed on the fracture cross-section. Furthermore, the glass-transition temperature of CE/BMI/EP composite reaches the highest values of nearly 300 °C, with the relative dielectric constant and dielectric loss being mostly reduced to less than 3.2 and 0.01, respectively. The experimental results demonstrate that the CE/BMI/EP composite is a highly-qualified wave-transmission material with preferences in mechanical, thermostability, and electrical insulation performances, suggesting its prospective applications in low-frequency transmittance radomes.


Assuntos
Cianatos/química , Resinas Epóxi/química , Teste de Materiais , Temperatura Alta , Propriedades de Superfície
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