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Abstract: Di-(2-ethylhexyl) ammonium phosphate (DEHAP)/octanol reverse micellar extraction was demonstrated to be an effective method to separate glutathione (GSH) from yeast fermentation broth. The effect of several important factors including pH, DEHAP concentration, and types and concentration of cations was investigated, and the optimum operating conditions were obtained by orthogonal experiments, for forward extraction: pH 2.5, DEHAP concentration=0.16mol/L, W 0 =10, phase ratio (organic/aqueous, v/v)=2:1, K+ concentration=0.1mol/L, and extraction time=15min. For back extraction: pH 10.5, Ca2+ concentration=0.6mol/L, phase ratio (aqueous/organic, v/v)=3:1, back extraction time=45min. Under the optimum operating conditions, the yield of GSH can reach 65% after one forward and three back extractions. No protein and only a small portion of amino acids were detected in the lyophilized product of GSH. The study on the extraction kinetics showed that the volumetric mass transfer rates of the forward and back extraction are around 0.209s−1 and 0.054s−1, respectively, which is very close to the literature results of electrostatic force-based reverse micellar extraction of protein. [Copyright &y& Elsevier]

The air–sea exchange of elemental mercury (Hg0) plays an important role in the global Hg cycle. Existing air–sea exchange models for Hg0 have not considered the impact of sea surfactants and wave breaking on the exchange velocity, leading to insufficient constraints on the flux of Hg0. In this study, we have improved the air–sea exchange model of Hg0 in the three-dimensional ocean transport model MITgcm by incorporating sea surfactants and wave breaking processes through parameterization utilizing the total organic carbon concentration and significant wave height data. The inclusion of these factors results in an increase of over twofold in the transfer velocity of Hg0 relative to the baseline model. Air–sea exchange flux is increased in mid- to high-latitude regions with high wind and wave breaking efficiency, while it is reduced by surfactant and concentration change at low latitudes with low wind speeds and nearshore areas with low wave heights. Compared with previous parameterizations, the updated model demonstrates a stronger dependence of Hg0 air–sea exchange velocity on wind speed. Our results also provide a theoretical explanation for the large variances in estimated transfer velocity between different schemes. [ABSTRACT FROM AUTHOR]

High-mercury wet deposition in the southeastern United States has been noticed for many years. Previous studies came up with a theory that it was associated with high-altitude divalent mercury scavenged by convective precipitation. Given the coarse resolution of previous models (e.g., GEOS-Chem), this theory is still not fully tested. Here we employed a newly developed WRF-GEOS-Chem (WRF-GC; WRF: Weather Research Forecasting) model implemented with mercury simulation (WRF-GC-Hg v1.0). We conduct extensive model benchmarking by comparing WRF-GC with different resolutions (from 50 to 25 km) to GEOS-Chem output (4 ∘ × 5 ∘) and data from the Mercury Deposition Network (MDN) in July–September 2013. The comparison of mercury wet deposition from two models presents high-mercury wet deposition in the southeastern United States. We divided simulation results by heights (2, 4, 6, 8 km), different types of precipitation (large-scale and convective), and combinations of these two variations together and find most mercury wet deposition concentrates on higher level and is caused by convective precipitation. Therefore, we conclude that it is the deep convection that caused enhanced mercury wet deposition in the southeastern United States. [ABSTRACT FROM AUTHOR]

High mercury wet deposition in southeastern United States has been noticed for many years. Previous studies came up with a theory that it was associated with high-altitude divalent mercury scavenged by convective precipitation. Given the coarse resolution of previous models (e.g. GEOS-Chem), this theory is still not fully tested. Here we employed a newly developed WRF-GEOS-Chem (WRF-GC) model implemented with mercury simulation. We conduct extensive model benchmarking by comparing WRF-GC with different resolutions (from 50 km to 25 km) to GEOS-Chem output (4° × 5°) and data from Mercury Deposition Network (MDN) in July-September 2013. The comparison of mercury wet deposition from two models both present high mercury wet deposition in southeastern United States. We divided simulation results by heights, different types of precipitation and combination of these two variations together and find most of mercury wet deposition concentrates on higher space and caused by convective precipitation. Therefore, we conclude that it is the deep convection caused enhanced mercury wet deposition in the southeastern United States. [ABSTRACT FROM AUTHOR]

The results of axial stress-strain measurements made from short columnar samples of seafloor shallow surface sediment in the southern South China Sea area indicate that there are three kinds of variations in the longitudinal wave sound velocity, which are related to such characteristics as physical-mechanical properties, grain contact status and grain structure and microstructure of the submarine shallow surface sediment. This study may make theoretical contributions to further understanding the reliability of various submarine sediments in the southern South China Sea as bearing interfaces and such scientific objectives as phonotelemetering and remote sensing of the engineering mechanical properties of seafloor sediment. [ABSTRACT FROM AUTHOR]

Analytical results of sound velocity and spectrum for seafloor sediment ore obtained by VWA (velocity-wave-amplitude) discrimination technique. Based on velocity-wave-amplitude, an understanding is gained of the physical condition and structural characteristics of seafloor sediment, which is combined with other geological information of the sedimentary layer to synthetically discriminate the properties of seafloor sediment. Experimental results show that, by using the relationship between sound velocity, wave form envelope, amplitude shape and size, and such parameters as sedimentary structure, microstructure, bedding, grain composition, mineral composition, and physical-mechanics, etc., the basic properties of the shallow surface seafloor sediment in the experimental sea area can be discriminated and the burial depth of traces of ancient marine transgression and regression events in the borehole cores of seafloor sediment can be divided, thus making an attempt of and contribution to the practice of acoustically remote-sensing and telemetering seafloor sediment. [ABSTRACT FROM AUTHOR]

Using physical (acoustical engineering mechanics and scanning electron microscope) and other technical methods, is study makes a comprehensive analysis of the structural characteristics and engineering mechanics properties of sediments, the sediment structure, microstructure and their classification characteristics and in the light of the physical-mechanical characteristic parameters, the relations between the grain contact, grain accumulation, and porosity with the physical-mechanical characteristics of sediment, and reports the relationship between the acoustic physical parameters and the stress-strain properties of sediment. Results show that there are six structural types in the shelf seabed sediment of the northern South China Sea, among which, the mixed contact structural type sediment has a higher compressive strength and a higher sound velocity than others, and that in the shallow seabed there exists a mesoscale structure with high and low velocity layers. [ABSTRACT FROM AUTHOR]

This article preliminarily reports and analyses the transmission characteristics and behaviors of shear wave in the offshore seafloor surface sediments in China, discusses the relationships between the physical and mechanical features of the shear wave and the compression wave, and compares the testing results with that of Hamilton and Chen et al. The result shows that the shear wave can be tested if the seafloor surface sediment has tangent modulus. The shear wave velocity ranges from 50–600 m/s and the measuring frequency from 50–200 kHz. The sound velocity rate of shear wave and compression wave can be used to appraise the stress-strain feature of seafloor surface sediments. This study provides a basis for further describing and appraising the seafloor sedimentary acoustic-mechanical feature and building a geological-acoustic model on China's offshore sea area. [ABSTRACT FROM AUTHOR]

Sound velocity in each type of seafloor sediment from the South China Sea varies with the development of strain in the controlled stress-strain course. Experiments show that there may exist three cases for the maximum sound velocity: (1) it appears at the stress peak; (2) it appears in the phase of no load; and (3) it appears at the end of the strain course. These results are related to physical-mechanical properties and structure of sediments. [ABSTRACT FROM AUTHOR]

• The Hg fluxes of the river to the ocean were about 10 Mg/yr in 2018 and 2021. • Agricultural emission & sediment re-suspension significantly contributes to Hg flux. • The Three Gorges Dam is still a significant sink of Hg. • More efforts are needed to decrease the Hg flux in the Yangtze River. Riverine processes are crucial for the biogeochemical cycle of mercury (Hg). The Yangtze River, the largest river in East Asia, discharges a substantial amount of Hg into the East China Sea. However, the influencing factors of the Hg budget and its recent trends remain unclear. This study quantitatively analyzed the total Hg concentration (THg) in suspended particulate matter (SPM) in the Yangtze River and calculated the Hg budget in 2018 and 2021. The results showed that the total Hg concentrations varied substantially along the river, with concentrations ranging from 23 to 883 μg/kg in 2018 and 47 to 146 μg/kg in 2021. The average Hg flux to China Sea in 2018 and 2021 were approximately 10 Mg/yr, lower than in 2016 (48 Mg/yr). Over 70% of the SPM was trapped in the Three Gorges Dam (TGD), and 22 Mg/yr of Hg settled in the TGD in 2018 and 10 Mg/yr in 2021. Hg fluxes in the Yangtze River watershed were driven by various factors, including decreased industrial emissions, increased agriculture emissions, and decreased soil erosion flux. We found that in the upper reach of the Yangtze River changed from sink to source of Hg possibly due to the resuspension of sediments, which implies that the settled sediments could be a potential source of Hg for downstream. Overall, emission control policies may have had a positive impact on reducing Hg flux to the East China Sea from 2016 to 2021, but more efforts are needed to further reduce Hg emissions. [Display omitted] [ABSTRACT FROM AUTHOR]

This study focused on the heavy metal concentrations in the soil and their representative input and output fluxes to paddy fields in four types of contaminated areas in Changzhutan urban agglomerations, Hunan, China. Four types of contaminated areas (mining area, livestock breeding area, suburb area and control area) were chosen for monitoring. Three input pathways and three output pathways were considered so as to figure out the heavy metal balance throughout the topsoil. In all study areas, the input fluxes of atmospheric deposition, accounting for 51.21%–94.74% of the total input fluxes, were significantly higher than those of fertilizer and irrigation water. Nevertheless, the manure fertilizer contributes nearly the same proportion as atmospheric deposition in livestock breeding area. In suburb area, only the flux of atmospheric deposition was higher than that in control area, and other input fluxes showed no significant difference. Crop removal, especially straw removal, was the primary output pathway of soil elements, contributing 60.19%–89.37% of the total output fluxes. Annual balance demonstrated that Cd was the metal of the primary concern in study areas. Furthermore, obvious differences were observed among the distribution of heavy metals (Cd, Pb and As) fractions in four types of contaminated areas. In general, the available content was the primary portion of the total contents, mostly up to about 51.70%–87.76%. The information obtained in this paper provides a more comprehensive understanding of the differences in the net inputs of heavy metals among four types of contaminated areas and emphasizes the significance of straw removal for Hunan agricultural soil. [ABSTRACT FROM AUTHOR]

The vegetation uptake of atmospheric elemental mercury [Hg(0)] and its subsequent littering are critical processes of the terrestrial Hg cycles. There is a large uncertainty in the estimated global fluxes of these processes due to the knowledge gap in the underlying mechanisms and their relationship with environmental factors. Here, we develop a new global model based on the Community Land Model Version 5 (CLM5-Hg) as an independent component of the Community Earth System Model 2 (CESM2). We explore the global pattern of gaseous elemental Hg [Hg(0)] uptake by vegetation and the spatial distribution of litter Hg concentration constrained by observed datasets as well as its driving mechanism. The annual vegetation uptake of Hg(0) is estimated as 3132 Mg yr−1, which is considerably higher than previous global models. The scheme of dynamic plant growth including stomatal activities substantially improves the estimation for global terrestrial distribution of Hg, compared to the leaf area index (LAI) based scheme that is often used by previous models. We find the global distribution of litter Hg concentrations driven by vegetation uptake of atmospheric Hg(0), which are simulated to be higher in East Asia (87 ng/g) than in the Amazon region (63 ng/g). Meanwhile, as a significant source for litter Hg, the formation of structural litter (cellulose litter + lignin litter) results in a lagging effect between Hg(0) deposition and litter Hg concentration, implying the buffering effect of vegetation on the air-land exchange of Hg. This work highlights the importance of vegetation physiology and environmental factors in understanding the vegetation sequestration of atmospheric Hg globally, and calls for greater efforts to protect forests and afforestation. [ABSTRACT FROM AUTHOR]