Sediment resuspension as a driving force for organic carbon transference and rebalance in marginal seas.

The transfer of particulate organic carbon (POC) to dissolved organic carbon (DOC; OC transferP-D) is crucial for the marine carbon cycle. Sediment resuspension driven by hydrodynamic forcing can affect the burial of sedimentary POC and benthic biological processes in marginal sea. However, the role of sediment grain size fraction on OC transferP-D and the subsequent impact on OC cycling remain unknown. Here, we conduct sediment resuspension simulations by resuspending grain-size fractionated sediments (< 20, 20-63, and > 63 µm) into filtered seawater, combined with analyses of OC content, optical characteristics, 13C and 14C isotope compositions, and molecular dynamics simulations to investigate OC transferP-D and its regulations on OC bioavailability under sediment resuspension. Our results show that the relative intensities of terrestrial humic-like OC (refractory DOC) increase in resuspension experiments of < 20, 20-63, and > 63 µm sediments by 0.14, 0.01, and 0.03, respectively, likely suggesting that sediment resuspension drives refractory DOC transfer into seawater. The variations in the relative intensities of microbial protein-like DOC are linked to the change of terrestrial humic-like OC, accompanied by higher DOC content and reactivity in seawater, particularly in finer sediments resuspension experiments. This implies that transferred DOC likely fuels microbial growth, contributing to the subsequent enhancement of DOC bioavailability in seawater. Our results also show that the POC contents increase by 0.35 %, 0.66 %, and 0.93 % in < 20, 20-63, and > 63 µm resuspension experiments at the end of incubation, respectively. This suggests that the re-absorption of OC on particles may be a significant process, but previously unrecognized during sediment resuspension. Overall, our findings suggest that sediment resuspension promotes the OC transferP-D, and the magnitudes of OC transferP-D further influence the DOC and POC properties by inducing microbial production and respiration. These processes significantly affect the dynamics and recycling of biological carbon pump in shallow marginal seas.

Influences of oxidation ability on precision in nitrogen isotope measurements of organic reference materials using elemental analysis-isotope ratio mass spectrometry.

RATIONALE: The precision of the standard measurements of reference materials (RMs) is critical to normalize the raw δ15 N values of samples to the international scale. Because the measurement configuration is required to moderate the properties of both RMs and samples for obtaining an ideal measurement precision, it is important to determine the appropriate measurement configurations of RMs to achieve accurate nitrogen isotope compositions of samples. Therefore, it is critical to systematically examine RMs for optimizing the configurations and further improve the measurement precision. METHODS: Gas source isotope ratio mass spectrometry (IRMS) coupled with an online elemental analyzer (EA) equipped with a single-quartz reactor was performed to analyze the nitrogen isotope compositions. Some adjustments were made as follows: (a) as the in-house working standard, urea was used to investigate the influences of combustion through moderating the different oxygen injections (0-20 mL) and sample delay times (10-12 s) and optimize the combustion conditions to enhance oxidation ability; (b) CO2 from the sample gas stream was removed to prevent interferences between CO2 and N2 ; (c) international RMs, including USGS40 (l-glutamic), IAEA600 (caffeine), and soil standard (B2153) with a low organic content, were systematically analyzed under the optimized configurations, and the precisions of the δ15 N values were further examined. RESULTS: Our results showed that sufficient oxygen should be injected to improve the sample combustion when analyzing δ15 N in natural samples such as soil or marine sediment with low organic content. In addition, the measurement precision of δ15 N was affected by the tailing of the CO2 peak from the gas chromatography column into the subsequent sample measurement if the EA is equipped with a single-quartz reactor column. Our adjustments can produce an optimized repeatability and accuracy of the δ15 N value, especially for RMs with low organic content, and the uncertainty of the measurements is improved to be better than 0.1‰ under optimized configurations. CONCLUSIONS: The analytical conditions such as the oxygen flow rate and injection time or sample introduction time into the EA need to be adjusted depending on the combustion conditions of the RMs and samples to obtain a reliable accuracy of measurement. We recommend that when analyzing δ15 N of natural samples such as soil or marine sediment samples with low organic content, more oxygen should be injected to improve the combustion of the samples. In addition, CO2 should be removed from the sample gas stream before being introduced into the isotope ratio mass spectrometer when the EA is equipped with a single-quartz reactor.

Construction of rGO wrapping Cu2O/ZnO heterostructure photocatalyst for PNP and PAM degradation.

Copper and zinc composite oxides (Cu2O/ZnO) were synthesized by an impregnation-reduction-air oxidation method. A series of Cu2O/ZnO/rGO ternary composites were prepared by coupling with graphene oxide (GO) with different mass fractions in a solvothermal reaction system. The microscopic morphology, crystal structure, and optical characteristics of the photocatalysts were characterized. The degradation of p-Nitrophenol (PNP) and polyacrylamide (PAM) by photocatalytic materials under simulated solar irradiation were studied, and the degradation kinetics were also investigated. The results showed that cubic Cu2O was modified by ZnO nanorods and distributed on rGO nanosheets. The ternary Cu2O/ZnO/rGO nanocomposites have stronger simulated solar absorption ability and higher photodegradation efficiency than pure ZnO and binary Cu2O/ZnO nanocomposites. When the amount of Cu2O/ZnO/rGO-10 was 0.3 g L-1, the degradation rate of 10 mg L-1 PNP reached 98% at 90 min and 99.6% of 100 mg L-1 PAM at 30 min. The photocatalytic degradation processes of PNP and PAM all followed the pseudo-first-order kinetic model. Free radical trapping experiments showed that superoxide radicals were the main active substances to improve photocatalytic efficiency. In addition, after four recycles, the catalytic efficiency of Cu2O/ZnO/rGO-10 was still over 90%. It showed that Cu2O/ZnO/rGO-10 was a promising catalyst for wastewater treatment because of its good photostability and reusability.

Antibacterial and anticorrosive properties of CuZnO@RGO waterborne polyurethane coating in circulating cooling water.

In order to control bacterial adhesion and metal corrosion in the circulating cooling water system, it is necessary to prepare a nanocomposite-modified coating with antibacterial and anticorrosive functions. Copper and zinc composite oxide (CuZnO) was synthesized to prepare CuZnO@RGO nanocomposites. The antibacterial mechanism of CuZnO@RGO nanocomposites was investigated using gram-negative bacteria E. coli and gram-positive bacteria S. aureus as the two model microorganisms. The antibacterial properties of CuZnO@RGO nanocomposites on mixed bacteria were researched in the cooling water system. In addition, the CuZnO@RGO waterborne polyurethane (WPU) composite coating (CuZnO@RGO/WPU) was synthesized. The antibacterial performance, hardness, and corrosion inhibition performance of CuZnO@RGO/WPU composite coating in the cooling water system were also investigated. The results showed that after adding CuZnO@RGO nanocomposites to E. coli or S. aureus suspension, the protein leakage after 20 h was 9.3 times or 7.2 times higher than that in the blank experiment. The antibacterial rate of CuZnO@RGO nanocomposites in circulating cooling water reached 99.70% when the mass fraction of RGO was 15%. When the mass fraction of CuZnO@RGO accounting for CuZnO@RGO/WPU composite coating was 2%, the antibacterial rate, hardness, and corrosion inhibition efficiency were 94.35%, 5H, and 93.30%, respectively.

Antibacterial properties of chitosan chloride-graphene oxide composites modified quartz sand filter media in water treatment.

In order to control bacterial pollution in water treatment, it is necessary to prepare efficient antibacterial materials. Novel chitosan chloride-graphene oxide (CSCl@GO) composites were prepared via a one-step solution blending method. The composites were characterized by FT-IR, XRD and TEM techniques. The antibacterial mechanism of CSCl@GO composites was investigated using gram-negative bacteria E. coli and gram-positive bacteria S. aureus as two model microorganisms. The antibacterial properties of CSCl@GO composites for complex bacteria in the cooling water system were researched. In addition, the CSCl@GO composites modified quartz sand filter media (CSCl@GO/QS) were synthesized. The antibacterial performance of CSCl@GO/QS filter media in secondary effluent of domestic sewage was also investigated. The results showed that E. coli and S. aureus were completely inactivated after treatment with 100 mg·L-1 of CSCl@GO composites for 15 min. When adding CSCl@GO composites to E. coli or S. aureus suspension, the protein leakage was 12.7 or 9.9 times higher than that in the blank experiment after 12 h. The antibacterial rate of CSCl@GO composites in circulating cooling water reached 95.74% when the mass fraction of GO was 0.6%. After the CSCl@GO/QS filter media were backwashed for 3 times, the antibacterial rate could still be above 90%.

A taxonomic study of Eupolyphaga Chopard, 1929 (Blattodea: Corydiidae: Corydiinae).

The cockroach genus Eupolyphaga is revised. Twenty species and two subspecies are recognized, with thirteen species and two subspecies are new to science: E. daweishana sp. nov., E. dongi sp. nov., E. fengi sp. nov., E. hanae sp. nov., E. hupingensis sp. nov., E. maculata sp. nov., E. nigrifera sp. nov., E. nigrinotum sp. nov., E. pilosa sp. nov., E. robusta sp. nov., E. shennongensis sp. nov., E. wooi sp. nov., E. xuorum sp. nov., E. everestiana reni subsp. nov., and E. fengi yongshengensis subsp. nov. Homœogamia sinensis Saussure is placed as a junior synonym of E. sinensis (Walker) and the replaced name E. limbata (Kirby) for Homœogamia sinensis is invalid, the status of Eupolyphaga thibetana (Chopard) is recovered. Male genitalia of species in the genus is described and illustrated. Females and oothecae of some species are described and illustrated. Distribution maps and a checklist of Eupolyphaga are provided. A key to males of Eupolyphaga is given. Plenty habitat photographs are shown.