The successful implementation of in-situ bioremediation of nonaqueous-phase liquid (NAPL) contamination in soil-groundwater systems is greatly influenced by the migration performance of NAPL-degrading bacteria. However, the impact and mechanisms of NAPL on the migration/retention of pollutant-degrading bacteria remain unclear. This study investigated the migration/retention performance of A. lwoffii U1091, a strain capable of degrading diesel while producing surfactants, in porous media without and with the presence of mono- and multicomponent NAPL (n-dodecane and diesel) under environmentally relevant conditions. The results showed that under all examined conditions (5 and 50 mM NaCl solution at flow rates of 4 and 8 m/d), the presence of n-dodecane/diesel in porous media could reduce the migration and enhance retention of A. lwoffii in quartz sand columns. Moreover, comparing with mutlicomponent NAPLs of n-dodecane, the monocomponent NAPLs (diesel) exhibited a greater reduction effect on the retention of A. lwoffii in porous media. Through systemically investigating the potential mechanisms via tracer experiment, visible chamber experiment, and theoretical calculation, we found that the reduction in porosity, repulsive forces and movement speeds, the presence of stagnant flow zones in porous media, particularly the biosurfactants generated by A. lwoffii contributed to the enhanced retention of bacteria in NAPL-contaminated porous media. Moreover, owing to presence of the greater amount of hydrophilic components in diesel than in n-dodecane, the available binding sites for the adsorption of bacteria were lower in diesel, resulting in the slightly decreased retention of A. lwoffii in porous media containing diesel than n-dodecane. This study demonstrated that comparing with porous media without NAPL contamination, the retention of strain capable of degrading NAPL in porous media with NAPL contamination was enhanced, beneficial for the subsequent biodegradation of NAPL.
Abstract The insufficient exciton (e−-h+ pair) separation/transfer and sluggish two-electron water oxidation are two main factors limiting the H2O2 photosynthetic efficiency of covalent organic frameworks (COFs) photocatalysts. Herein, we present an alternative strategy to simultaneously facilitate exciton separation/transfer and reduce the energy barrier of two-electron water oxidation in COFs via a dicyano functionalization. The in situ characterization and theoretical calculations reveal that the dicyano functionalization improves the amount of charge transfer channels between donor and acceptor units from two in COF-0CN without cyano functionalization to three in COF-1CN with mono-cyano functionalization and four in COF-2CN with dicyano functionalization, leading to the highest separation/transfer efficiency in COF-2CN. More importantly, the dicyano group activates the neighbouring C atom to produce the key *OH intermediate for effectively reducing the energy barrier of rate-determining two-electron water oxidation in H2O2 photosynthesis. The simultaneously enhanced exciton separation/transfer and two-electron water oxidation in COF-2CN result in high H2O2 yield (1601 μmol g−1 h−1) from water and oxygen without using sacrificial reagent under visible-light irradiation. COF-2CN can effectively yield H2O2 in water with wide pH range, in different real water samples, in scaled-up reactor under natural sunlight irradiation, and in continuous-flow reactor for consecutively producing H2O2 solution for water decontamination.
Human occupants themselves constitute an important source of volatile organic compounds (VOCs) in indoor environments through breath and dermal emissions. In order to quantify VOC emissions from occupants under real-world settings, previous indoor observational studies often determined emission factors (i.e., average emission rates per person). However, the values obtained across these studies exhibited large variability, and the causes of this variability still need to be understood. Herein we report 10-day real-time VOC measurements in a university student office, using a proton transfer reaction-quadrupole interface-time-of-flight mass spectrometer. A method was developed to identify VOCs of primary human origin and to quantify the corresponding emission factors, accounting for the dynamically changing occupancy level and ventilation rate in the assessed office. We found that the emission factors of many dermally emitted VOCs strongly increased as the ozone concentration increased from <3 to 10–15 ppb. These VOCs include geranyl acetone, 6-methyl-5-hepten-2-one (6-MHO), and C10-C12 saturated aldehydes, which align with characteristic first-generation ozonolysis products of skin oil. The strongest increase occurred for 6-MHO, from 113 to 337 μg/h/p. In comparison, acetone and isoprene, which are primarily emitted from human breath, varied little with the ozone level. In light of this finding, we conducted an integrated analysis of emission factors reported in the literature for two frequently reported species, namely, 6-MHO and decanal. Ozone concentration alone can explain 94–97% of the variation in their emission factors across previous studies, and the best-estimated ozone dependence obtained using the literature data is consistent with those obtained in the current study. These results suggest that the ozone concentration is a key factor regulating emission factors of many dermally emitted VOCs in real indoor environments, which has to be considered when reporting or using the emission factors.
Quorum sensing (QS)-based manipulations emerge as a promising solution for biofilm reactors to overcome challenges from inefficient biofilm formation and lengthy start-ups. However, the ecological mechanisms underlying how QS regulates microbial behaviors and community assembly remain elusive. Herein, by introducing different levels of N-acyl-homoserine lactones, we manipulated the strength of QS during the start-up of moving bed biofilm reactors and compared the dynamics of bacterial communities. We found that enhanced QS elevated the fitness of fast-growing bacteria with high ribosomal RNA operon (rrn) copy numbers in their genomes in both the sludge and biofilm communities. This led to notably increased extracellular substance production, as evidenced by strong positive correlations between community-level rrn copy numbers and extracellular proteins and polysaccharides (Pearson's r = 0.529−0.830, P < 0.001). Network analyses demonstrated that enhanced QS significantly promoted the ecological interactions among taxa, particularly cooperative interactions. Bacterial taxa with higher network degrees were more strongly correlated with extracellular substances, suggesting their crucial roles as public goods in regulating bacterial interactions and shaping network structures. However, the assembly of more cooperative communities in QS-enhanced reactors came at the cost of decreased network stability and modularity. Null model and dissimilarity-overlap curve analysis revealed that enhanced QS strengthened stochastic processes in community assembly and rendered the universal population dynamics more convergent. Additionally, these shaping effects were consistent for both the sludge and biofilm communities, underpinning the planktonic-to-biofilm transition. This work highlights that QS manipulations efficiently drive community assembly and confer specialized functional traits to communities by recruiting taxa with specific life strategies and regulating interspecific interactions. These ecological insights deepen our understanding of the rules governing microbial societies and provide guidance for managing engineering ecosystems.
The speedy raise of residential buildings' carbon emissions is a hindrance to achieving China's 2030 carbon peak goal. This study constructs an assessment framework for comprehensive consideration of 30 Chinese provinces' socioeconomic circumstances, energy demand, and emissions reduction technology to meet the consistent coupling degree of equity and efficiency (CDEE). This study is the first to propose an allocation scheme for equilibrating provincial carbon increments for rural and urban residential buildings in 2030 under carbon peaking constraints. The relevant results are fourfold. (1) Residential building's floor area per capita and energy carbon emissions coefficients are the soliddest drivers to facilitate and inhibit the raise of carbon emissions during 2010–2020. (2) Through dynamic Monte Carlo simulation from 2021 to 2030, we demonstrate that provinces with the most gamey carbon emissions in urban and rural areas include Shandong, at 121.52 (± 5.50) Mt. and Hebei, at 61.34 (± 3.08) Mt. in 2030, respectively. (3) A CDEE of 52.3% (biased equity) in urban areas and 34.5% (biased efficiency) in rural areas indicates equilibrated allocation of provincial carbon increment. (4) In the final 2030 allocation scheme, the greatest carbon mitigation pressures are in Beijing (11.34 Mt) and Heilongjiang (3.23 Mt), and the provinces with the largest carbon increment in urban areas include Hebei, Henan, and Guangdong, while the largest carbon increments in rural areas are in Hebei, Henan, and Guangdong. Overall, this study furnishes a targeted and valuable decision making reference for the government to determine provincial carbon peak goals for Chinese residential buildings.
Deep neural networks can be employed for estimating the direction of arrival (DOA) of individual sound sources from audio signals. Existing methods mostly focus on estimating the DOA of each source on individual frames, without utilizing the motion information of the sources. This paper proposes a method for estimating trajectories of sources, leveraging the differential of trajectories across different time scales. Additionally, a neural network is employed for enhancing the trajectories wrongly estimated especially for sound sources with low-energy. Experimental evaluations conducted on simulated dataset validate that the proposed method achieves more precise localization and tracking performance and encounters less interference when the sound source energy is low.
Chlorinated paraffins (CPs), mainly short-chain CPs (SCCPs) and medium-chain CPs (MCCPs), are currently the most produced and used industrial chemicals related to persistent organic pollutants (POPs) globally. These chemicals are widely detected in the environment and in the human body. As the release of SCCPs and MCCPs from products represents only a small fraction of their stock in products, the potential long-term release of CPs from a large variety of products at the waste stage has become an issue of great concern. The results of this study showed that, by 2050, SCCPs and MCCPs used between 2000 and 2021 will cumulatively generate 226.49 Mt of CP-containing wastes, comprising 8610.13 kt of SCCPs and MCCPs. Approximately 79.72 Mt of CP-containing wastes is predicted to be generated abroad through the international trade of products using SCCPs and MCCPs. The magnitude, distribution, and growth of CP-containing wastes subject to environmentally sound disposal will depend largely on the relevant provisions of the Stockholm and Basel Conventions and the forthcoming global plastic treaty. According to multiple scenarios synthesizing the provisions of the three conventions, 26.6–101.1 Mt of CP-containing wastes will be subject to environmentally sound disposal as POP wastes, which would pose a great challenge to the waste disposal capacity of China, as well as for countries importing CP-containing products. The additional 5-year exemption period for MCCPs is expected to see an additional 10 Mt of CP-containing wastes subject to environmentally sound disposal. Thus, there is an urgent need to strengthen the Stockholm and Basel Conventions and the global plastic treaty.
This paper aims to examine the impact of the digital economy on urban entrepreneurship and its spatial spillover effects. To achieve this purpose, this research relies on data from 252 prefecture-level cities in China from 2012 to 2019. The findings demonstrate that the development of the digital economy has a positive influence on entrepreneurial activity in cities, with particularly effects observed robust at higher quantile levels. Additionally, the results suggest that urban entrepreneurial activity may be a siphoning effect, impeding entrepreneurship in neighboring cities. Furthermore, further investigation shows regional and policy heterogeneity.
Promoting rural family entrepreneurship is an effective way to realize rural revitalization. The primary aim of this study is to assess the entrepreneurial impact of family social capital on rural households in China. The objective of this study is to understand how family social capital affects rural entrepreneurship in a Chinese context. Using data from the 2020 China Family Panel Studies, this study empirically tests the effect of family social capital on rural family entrepreneurship. Research shows that family social capital is significantly and positively correlated with rural family entrepreneurship, indicating that it is an essential determinant in promoting rural family entrepreneurship. Internet use is an effective transmission path for family social capital, which affects rural entrepreneurship, and the impact of rural entrepreneurship varies with family size and household head characteristics. This study not only enriches the theoretical understanding of rural entrepreneurship but also sheds light on the behavioral mechanisms that explain the entrepreneurial process of rural households. To promote rural entrepreneurship and revitalization, it is important to be adept at activating family social capital.
