Search

Inland water ecosystems are unique, whereby water level changes can lead to variance in greenhouse gas (GHG) emissions. The GHG circulation intensity of inland waterbodies is high, so different water depths affect the temperature sensitivity of greenhouse gases, and have different cooling effects on CO 2 storage and warming effects on CH 4 emissions, being a typical GHG conversion channel. This study systematically reveals geographical GHG emission patterns from inland waterbodies and GHG impact mechanisms from regional waterbodies. Special emphasis is also paid to compounded environmental impact changes on GHG emissions under water level regulations. Additionally, we explore how increases in primary productivity can convert aquatic ecosystems from CO 2 sources to CO 2 sinks. However, GHG formation and emissions under ecological reservoir water level fluctuations in flood-ebb zones, intertidal tidal zones, wetlands, and lacustrine systems remain uncertain compared with those under natural hydrological conditions. Therefore, mechanisms that control GHG exchange and production processes under water level changes must first be determined, especially regarding post flood hydrological-based drying effects on GHG flux at the water-air interface. Finally, we recommend instituting environmental management and water-level control measures to reduce GHG emissions, which are favorable for minimizing GHG flux while protecting ecosystem functions and biodiversity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study addressed the challenges of cost and portability in synchronous monitoring water quality and greenhouse gas emissions in paddy-dominated regions by developing a novel Internet of Things (IoT)-based monitoring system (WG-IoT-MS). The system, equipped with low-cost sensors and integrated intelligent algorithms, enabled real-time monitoring of dissolved N 2 O concentrations. Combined with an air-water gas exchange model, the system achieved efficient monitoring and simulation of CO 2 and N 2 O emissions from agricultural water bodies while reducing monitoring costs by approximately 60 %. The proposed method was validated in paddy-dominated regions in Danyang, China. Results indicated the excellence of the dissolved N 2 O concentration model based on support vector regression, demonstrating accurate predictions within a concentration range of 2.003 to 13.247 μg/L. Notably, the model maintained acceptable predictive accuracy (R 2 > 0.70) even when some variables were partially absent (with the number of missing variables < 2 and the missing proportion (MP) ≤ 50 %), making up for the data loss caused by sensor malfunctions. Furthermore, the model performed well (R 2 > 0.80) when testing data sourced from paddy fields and lakes. Finally, CO 2 and N 2 O emissions were successfully monitored, with the results validated using a floating chamber method (R 2 > 0.70). The method provides crucial technical support for quantitative assessment of water quality and greenhouse gas emissions in paddy-dominated regions, laying a foundation for formulating effective emission reduction strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Revealing the magnitude, dynamics, and influencing factors of CO 2 emissions across the water-air interface in karst water with high frequency is crucial for accurately assessing the carbon budget in a karst environment. Due to the limitations of observation methods, the current research is still very insufficient. To solve the above problems and clarify the main influencing factors of CO 2 emission in karst water, this study selected Dalongdong (DLD) Reservoir, located in the typical karst peak and valley area in southwest China, to carry out a multi-parameter high-frequency monitoring study from January to December 2021, and used the thin boundary model method to estimate the CO 2 flux across the water-air interface (CF). The average annual flux of DLD reservoir is 84.48 mmol·(m 2 ·h) -1 , which represents a CO 2 source overall. However, during the stratification period in August, there is a transient carbon sink due to negative CO 2 emission. The alteration of thermal stratification in water is crucial in regulating the seasonal variation of CF. Meanwhile, the diurnal variation is significantly influenced by changes in hydrochemical parameters during the thermal stratification stage. Compared to low wind speeds (<3 m/s), high wind speeds (≥3 m/s) have a greater impact on the CO 2 flux. Furthermore, high-frequency continuous data revealed that the reservoir triggered a CO 2 pulse emission during the turnover process, primarily at night, leading to unusually high CO 2 flux values. It is of great significance to monitor and reveal the process, flux, and control factors of CO 2 flux in land water at a high-frequency strategy. They will help improve the accuracy of regional or watershed carbon budgets and clarify the role of global land water in the global carbon budget., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

As a volatile organic compound, nitrobenzene has high vapor pressure and low boiling point, and it is very volatile when it enters the water body and enters the air. The mass transfer of VOCs at the water-air interface is a complex process of transboundary transport. In this paper, the effects of water temperature, interface turbulence, surfactant concentration, and humic acid concentration on the volatilization of nitrobenzene at the water-air interface were investigated. Under the influence of temperature, the volatilization of nitrobenzene accorded with the first-order kinetic equation. When the temperature increased from 5 ℃ to 25 ℃, the volatilization rate of nitrobenzene increased by 2.03 times. Temperature for volatilization rate constant was in accordance with the Arrhenius equation. The water-gas distribution of volatile organic compounds was in accordance with the Boltzman equation. Under the same temperature conditions, when the agitating intensity increased from 0 r/min to 250 r/min, the volatilization rate constant of nitrobenzene increased by 1.51 times. When the surfactant is greater than the critical micelle concentration, the volatilization rate constant of nitrobenzene decreases with the increase of surfactant. When the concentration of humic acid increased from 100 mg/L to 500 mg/L, the half-life increased by 1.14 h, and the volatilization rate decreased by 1.14 h, reduced by 17%. The results showed that the increase of temperature and the intensification of stirring had a significant promoting effect on the volatilization of nitrobenzene, while the surfactant and humic acid both played an inhibitory effect on the volatilization of nitrobenzene.

Extreme impedance mismatch causes sound insulation at water-air interfaces, limiting numerous cross-media applications such as ocean-air wireless acoustic communication. Although quarter-wave impedance transformers can improve transmission, they are not readily available for acoustics and are restricted by the fixed phase shift at full transmission. Here, this limitation is broken through impedance-matched hybrid metasurfaces assisted by topology optimization. Sound transmission enhancement and phase modulation across the water-air interface are achieved independently. Compared to the bare water-air interface, it is experimentally observed that the average transmitted amplitude through an impedance-matched metasurface at the peak frequency is enhanced by ≈25.9 dB, close to the limit of the perfect transmission 30 dB. And nearly 42 dB amplitude enhancement is measured by the hybrid metasurfaces with axial focusing function. Various customized vortex beams are experimentally realized to promote applications in ocean-air communication. The physical mechanisms of sound transmission enhancement for broadband and wide-angle incidences are revealed. The proposed concept has potential applications in efficient transmission and free communication across dissimilar media., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

The chamber method is widely used to measure CO 2 and CH 4 flux in inland water. However, the designs of chamber used in various studies are different and lack unified standards, which would affect the observation results. To clarify the impacts of chamber characteristics, including light transmittance, air pressure difference inside and outside the chamber, and gas mixing degree in the chamber, on CO 2 and CH 4 flux measurements at the water-air interface, we compared the effects of transparent/opaque chamber, the chamber with/without air pressure equalizing device and fan on CO 2 and CH 4 flux measurements in the aquaculture pond, based on the multi-channel closed dynamic chamber system. The results showed that, during the daytime in summer, compared with the transparent chamber which could measure the actual CO 2 flux, when CO 2 was emitted from the pond, the opaque chamber overestimated the CO 2 flux by 90%; when CO 2 was absorbed by the pond, the opaque chamber underestimated the CO 2 flux by 50%. The CH 4 diffusion flux measured by the opaque chamber was 40% lower than that measured by the transparent chamber. There was no significant difference between CO 2 and CH 4 flux measured by the chamber with and without air pressure equalizing device. CO 2 flux observed by the chamber without fan had poor representativeness, being 20% higher than that observed by the chamber with fan. Moreover, CH 4 flux emitted through different pathways could not be distinguished using the chamber without fan. Therefore, when the chamber method was used to observe the CO 2 and CH 4 flux at the water-air interface, the chamber shall be transparent and be installed with fan.

In this study, a pressurized, water-filled impedance tube (WFIT) was developed to measure the reflection coefficients of sound-absorbing materials under various hydrostatic pressures. The developed WFIT was calibrated using a two-microphone, three-parameter calibration method (3PCM). The accuracy and repeatability of the measured reflection coefficients for the water-air interface in the WFIT were determined by comparing these coefficients with corresponding theoretical reflection coefficients. The WFIT was then used to measure the acoustic reflection coefficient of a porous rubber specimen on three dates, and the corresponding measurement results exhibited satisfactory repeatability. The aforementioned impedance tube was also used to measure the reflection coefficient of a porous rubber specimen under a hydrostatic pressure of 4 P atm three times on the same day, and one time each on three days, using the same experimental setup and measurement procedure. The results obtained in the aforementioned tests also exhibited satisfactory repeatability. Finally, the WFIT was used to measure the reflection coefficients of porous rubber specimens with various thicknesses under different hydrostatic pressures. The results of this study indicate that the developed WFIT calibrated with the 3PCM can achieve suitable repeatability in the measurement of the reflection coefficients of sound-absorbing materials under various hydrostatic pressures.

Plastic debris in the marine environment are the subject of an extensive literature. According to studies dedicated to the determination of plastic litter abundance and to the characterisation of degradation and fragmentation processes, models were used to estimate the global plastic debris abundance and to simulate their transfer and distribution. Despite these efforts, there is still missing plastic in the models used as areas exist where plastic abundance is less than that estimated. In parallel, microplastics presence in the atmosphere and in remote areas was confirmed suggesting long range atmospheric transport. Potentially addressing both these issues, recent literature suggests that microplastics (MPs) and nanoplastics (NPs) can be transferred from the marine environment to the atmosphere via the bursting of air bubbles at the sea surface. Nevertheless, to date there is no direct evidence of this transfer. In this study, we evaluate plastic particles transfer as a function of MPs/NPs characteristics and water composition by simulating the bubble bursting phenomenon in a laboratory reactor. Size distribution of transferred particles were recorded, and their plastic nature was confirmed using electron microscopy. Results show that under tested conditions, the transfer is possible but limited to particles smaller than 1 μm. The influence of the presence of proxies of components of the sea surface microlayer in the water was evaluated showing a higher particle transfer rate in the presence of a surfactant (sodium dodecyl sulfate) and no significant effect of polysaccharides (xanthan gum and dextran). The surface state of the particles can alter their behaviour in the aqueous phase and thus their transfer to the atmosphere. The effect of bubble size was also evaluated showing a higher transfer rate with the smaller bubble size. In addition, experiments performed with grounded polyethylene (PE) samples showed higher transfer for UV-aged PE than for pristine PE., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

It was previously shown [J. K. Lee et al. , Proc. Natl. Acad. Sci. U.S.A , 116, 19294-19298 (2019)] that hydrogen peroxide (H 2 O 2 ) is spontaneously produced in micrometer-sized water droplets (microdroplets), which are generated by atomizing bulk water using nebulization without the application of an external electric field. Here we report that H 2 O 2 is spontaneously produced in water microdroplets formed by dropwise condensation of water vapor on low-temperature substrates. Because peroxide formation is induced by a strong electric field formed at the water-air interface of microdroplets, no catalysts or external electrical bias, as well as precursor chemicals, are necessary. Time-course observations of the H 2 O 2 production in condensate microdroplets showed that H 2 O 2 was generated from microdroplets with sizes typically less than ∼10 µm. The spontaneous production of H 2 O 2 was commonly observed on various different substrates, including silicon, plastic, glass, and metal. Studies with substrates with different surface conditions showed that the nucleation and the growth processes of condensate water microdroplets govern H 2 O 2 generation. We also found that the H 2 O 2 production yield strongly depends on environmental conditions, including relative humidity and substrate temperature. These results show that the production of H 2 O 2 occurs in water microdroplets formed by not only atomizing bulk water but also condensing water vapor, suggesting that spontaneous water oxidation to form H 2 O 2 from water microdroplets is a general phenomenon. These findings provide innovative opportunities for green chemistry at heterogeneous interfaces, self-cleaning of surfaces, and safe and effective disinfection. They also may have important implications for prebiotic chemistry., Competing Interests: The authors declare no competing interest.

Modeling studies have focused on N 2 O emissions in temperate rivers under static atmospheric N 2 O (N 2 O airc ), with cold temperate river networks under dynamic N 2 O airc receiving less attention. To address this knowledge and methodological gap, the dissolved N 2 O concentration (N 2 O disc ) and N 2 O airc algorithms were integrated with an air-water gas exchange model (F N2O ) into the SWAT (Soil and Water Assessment Tool). This new model (SWAT-F N2O ) allows users to simulate daily riverine N 2 O emissions under dynamic atmospheric N 2 O. The spatiotemporal fluctuations in the riverine N 2 O emissions was simulated and its response to the static and dynamic atmospheric N 2 O were analyzed in a middle-high latitude agricultural watershed in northeastern China. The results show that the SWAT-F N2O model is a useful method for capturing the hotspots in riverine N 2 O emissions. The model showed strong riverine N 2 O absorption and weak N 2 O emissions from September to February, which acted as a sink for atmospheric N 2 O in this cold temperate area. High N 2 O emissions occurred from April to July, which accounted for 83.34% of the yearly emissions. Spatial analysis indicated that the main stream and its tributary could contribute 302.3-1043.7 and 41.5-163.4 μg N 2 O/(m 2 ·d) to the total riverine N 2 O emissions (15.02 t/a), respectively. The riverine N 2 O emissions rates in the subbasins dominated by forests and paddy fields were lower than those in the subbasins dominated by arable and residential land. Riverine N 2 O emissions can be overestimated under the static atmospheric N 2 O rather than under the increasing atmospheric N 2 O. This overestimation has increased from 1.52% to 23.97% from 1990 to 2016 under the static atmospheric N 2 O. The results of this study are valuable for water quality and future climate change assessments that aim to protect aquatic and atmospheric environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The static chamber-gas chromatography method was applied to observe CO 2 fluxes across the water-air interface from different aquaculture systems, including four groups of mesocosms, i.e., blank control system (CK), monoculture system of Sebastes schlegelii (F), monoculture system of Chlamys farreri (B) and polyculture system of S. schlegelii and C. farreri (FB). Meanwhile, the physical, chemical and biological indices of the water were measured. The results showed that the group CK was a stable CO 2 source, with the mean flux of 12.42 mg·m -2 ·h -1 . The group B was a CO 2 source during the early and middle periods of the experiment and a CO 2 sink at the end of the experiment, with the mean flux during the experiment being 10.95 mg·m -2 ·h -1 . The change trends of CO 2 flux in the group F and FB were generally consistent, acting as CO 2 sources in the early period and as CO 2 sinks subsequently. The mean fluxes of those two groups during the expe-riment were -3.53 and -10.49 mg·m -2 ·h -1 , respectively. Water pH was a good predictor for CO 2 flux across the water-air interface according to the result of regression analysis, with pH value of 8.25 as the critical threshold between efflux and influx. The net primary production of water column was the main factor influencing the CO 2 flux, indicating that phytoplankton might be the main internal force regulating the CO 2 flux across the water-air interface. Our results indicated that C. farreri at present stocking density in the polyculture system could promote phytoplankton biomass as well as primary production and therefore enhance the CO 2 sink function.

Hydrophobins (HPs) are small secreted fungal proteins possibly involved in several processes such as formation of fungal aerial structures, attachment to hydrophobic surfaces, interaction with the environment and protection against the host defense system. The genome of the necrotrophic plant pathogen Fusarium graminearum contains five genes encoding for HPs (FgHyd1-5). Single and triple FgHyd mutants were produced and characterized. A reduced growth was observed when the Δ Fghyd2 and the three triple mutants including the deletion of FgHyd2 were grown in complete or minimal medium. Surprisingly, the growth of these mutants was similar to wild-type when grown under ionic, osmotic or oxidative stress conditions. All the mutant strains confirmed the ability to develop conidia and perithecia, suggesting that the FgHyds are not involved in normal development of asexual and sexual structures. A reduction in the ability of hyphae to penetrate through the water-air interface was observed for the single mutants Δ Fghyd2 and Δ Fghyd3 as well as for the triple mutants including the deletion of FgHyd2 and FgHyd3. Besides, Δ Fghyd3 and the triple mutant Δ Fghyd234 were also affected in the attachment to hydrophobic surface. Indeed, wheat infection experiments showed a reduction of symptomatic spikelets for Δ Fghyd2 and Δ Fghyd3 and the triple mutants only when spray inoculation was performed. This result could be ascribed to the affected ability of mutants deleted of FgHyd2 and FgHyd3 to penetrate through the water-air interface and to attach to hydrophobic surfaces such as the spike tissue. This hypothesis is strengthened by a histological analysis, performed by fluorescence microscopy, showing no defects in the morphology of infection structures produced by mutant strains. Interestingly, triple hydrophobin mutants were significantly more inhibited than wild-type by the treatment with a systemic triazole fungicide, while no defects at the cell wall level were observed.

Diurnal and seasonal characterization of CO 2 partial pressure p (CO 2 ) and CO 2 areal flux F (CO 2 ) at the water-air interface in an anthropogenic river in the Three Gorges Reservoir area was studied. A tributary of the Jialing River in Chongqing Municipality was chosen, and daily and seasonal samples were taken in summer and autumn, focusing on riverine p (CO 2 ), F (CO 2 ), and their associated controls. Henry's law combined with the thin boundary layer model was adopted to estimate the CO 2 flux via the water-air interface. The results indicated that F (CO 2 ) was not high on average, namely (87.8±27.5) mmol·(m 2 ·d) -1 and (139.2±34.0) mmol·(m 2 ·d) -1 in summer and autumn, respectively. The water-air interface F (CO 2 ) showed significant hourly, daily, and seasonal variations. CO 2 release peaked around 09:00 and then slightly decreased. We also found that pH, alkalinity, water, and temperature were significantly related to p (CO 2 ) and F (CO 2 ), whereas pH and alkalinity were the best predictors of F (CO 2 ). This study aids understanding of the impacts of urbanization on CO 2 emissions in the rivers and helps to re-evaluate local riverine CO 2 budgets.

CO 2 fluxes across water-air interfaces of river systems play important roles in regulating the regional and global carbon cycle. However, great uncertainty remains as to the contribution of these inland water bodies to the global carbon budget. Part of the uncertainty stems from limited understanding of the CO 2 fluxes at diurnal and seasonal frequencies caused by aquatic metabolism. Here, we measured surface water characteristics (temperature, pH, and DO, DIC, Ca 2+ concentrations) and CO 2 fluxes across the air-water interface at two transects of Guijiang River, southwest China to assess the seasonal and diurnal dynamics of fluvial carbon cycling and its potential role in regional and global carbon budgets. The two transects had differing bedrock; DM transect is underlain by carbonate and detrital rock and PY is underlain by pure carbonate. Our results show that the river water both degasses CO 2 to and absorbs CO 2 from the atmosphere in both summer and winter, but the degassing and absorption varied between the two transects. Further, CO 2 fluxes evolve through diurnal cycles. At DM, the river evaded CO 2 from early morning through noon and absorbed CO 2 from afternoon through early morning. At PY in summer, the CO 2 evasion decreased during the daytime and increased at night while in winter at night, CO 2 uptake increased in the morning and decreased in the afternoon but remained relatively stable at night. Although the river is a net source of carbon to the atmosphere (~15mMm -2 day -1 ), the evasion rate is the smallest of all reported world's inland water bodies reflecting sequestration of atmospheric carbon through the carbonate dissolution and high primary productivity. These results emphasize the need of seasonal and diurnal monitoring of CO 2 fluxes across water-air interface, particularly in highly productive rivers, to reduce uncertainty in current estimates of global riverine CO 2 emission., (Copyright © 2017 Elsevier B.V. All rights reserved.)

As an important part of inland waters,small pond is a neglected source of greenhouse gas.The main objective of the study was to quantify greenhouse gas fluxes (CO 2 and CH 4 ) from small pond in the Yangtze Delta using flux-gradient method.The results showed that:① zero-gradient test indicated that the flux measurement precision for water vapor,CO 2 ,and CH 4 was 7.525 W·m -2 ,0.022 mg·(m 2 ·s) -1 ,and 0.054 μg·(m 2 ·s) -1 ,respectively.During the test period,84%,80%,and 94% of half-hourly flux data for H 2 O,CO 2 ,and CH 4 were higher than the zero-gradient measurement precision.② Based on the measurement,the small pond was the source of CO 2 and CH 4 for the atmosphere in summer,the mean emission flux of CO 2 and CH 4 was 0.038 mg·(m 2 ·s) -1 and 0.889 μg·(m 2 ·s) -1 ,respectively.The CH 4 emission fluxes from the small pond were more higher than the median value of emission for global lakes.The results indicated that greenhouse gas emission from small pond was an important part for estimating inland water greenhouse gas emissions,especially for CH 4 emission.These results can provide scientific reference for making emission inventory of regional greenhouse gas.

Water interfaces provide the platform for many important biological, chemical, and physical processes. The water-air interface is the most common and simple aqueous interface and serves as a model system for water at a hydrophobic surface. Unveiling the microscopic (<1 nm) structure and dynamics of interfacial water at the water-vapor interface is essential for understanding the processes occurring on the water surface. At the water interface the network of very strong intermolecular interactions, hydrogen-bonds, is interrupted and the density of water is reduced. A central question regarding water at interfaces is the extent to which the structure and dynamics of water molecules are influenced by the interruption of the hydrogen-bonded network and thus differ from those of bulk water. Herein, we discuss recent advances in the study of interfacial water at the water-air interface using laser-based surface-specific vibrational spectroscopy., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Molecular fragment dynamics (MFD) is a mesoscopic simulation technique based on dissipative particle dynamics (DPD). MFD simulations of the self-aggregation of the polyoxyethylene alkyl ether surfactants C6E6, C10E6, C12E6 and C16E6 at the water-air surface lead to equilibrium nanoscale structures and computationally determined surface tensions which are in agreement with experimental data for different surfactant concentrations. Thus, molecular fragment dynamics is a well-suited predictive technique to study the behavior of new surfactant systems., (Copyright © 2013 Elsevier Inc. All rights reserved.)