Tidal effects on carbon dioxide emission dynamics in intertidal wetland sediments.

Understanding the control mechanisms of carbon dioxide (CO2) emissions in intertidal wetland sediments is beneficial for the concern of global carbon biogeochemistry and climate change. Nevertheless, multiple controls on CO2 emissions from intertidal wetland sediments to the atmosphere still need to be clarified. This study investigated the effect of tidal action on CO2 emissions from salt marsh sediments covered by Spartina alterniflora in the Jiaozhou Bay wetland using the static chamber method combined with an infrared CO2 detector. The results showed that the CO2 emission fluxes from the sediment during ebb tides were higher than those during flood tides. The whole wetland sediment acted as a weak source of atmospheric CO2 (average flux: 24.44 ± 16.80 mg C m-2 h-1) compared to terrestrial soils and was affected by the cycle of seawater inundation and exposure. The tidal influence on vertical dissolved inorganic carbon (DIC) transport in the sediment was also quantitated using a two-end member mixing model. The surface sediment layer (5-15 cm) with maximum DIC concentration during ebb tides became the one with minimum DIC concentration during flood tides, indicating the DIC transport from the surface sediment to seawater. Furthermore, aerobic respiration by microorganisms was the primary process of CO2 production in the sediment according to 16 S rDNA sequencing analysis. This study revealed the strong impact of tidal action on CO2 emissions from the wetland sediment and provided insights into the source-sink pattern of CO2 and DIC at the land-ocean interface.

A highly selective "turn-on" electroanalysis strategy with reduced copper metal-organic frameworks for sensing histamine and histidine.

A highly selective and sensitive electroanalysis strategy has been developed for sensing histamine (HTA) and histidine (His) with "turn-on" signal outputs using copper nanocomposites (Cu NCs) of reduced copper metal-organic frameworks (Cu MOFs). It was discovered that the Cu NC-modified electrodes could display the sharp and stable oxidation peaks of solid-state CuCl electrochemistry at a low potential (about -0.10 V). More interestingly, once HTA or His was introduced, the peaking currents of the electrodes would increase due to the specific interaction between Cu2+ and imidazole groups of HTA or His. A highly selective electroanalysis method was thereby developed for the detection of both HTA and His in the concentration range of 0.010-100 µM. Besides, the application feasibility of the developed electroanalysis strategy was demonstrated for the evaluation of HTA and His separately in red wine and urine samples. Such an electroanalysis candidate for HTA and His holds great potential for wide applications in the fields of food analysis and clinical disease diagnosis.

Mesoporous Silver-Melamine Nanowires Formed by Controlled Supermolecular Self-Assembly: A Selective Solid-State Electroanalysis for Probing Multiple Sulfides in Hyperhaline Media through the Specific Sulfide-Chloride Replacement Reactions.

Mesoporous silver-melamine (Ag-MA) nanocomposites were synthesized simply by the controlled supermolecular self-assembly process to be modified onto the electrodes for the electroanalysis of multiple sulfides in blood or wastewater. It was discovered that Ag-MA nanocomposites could be prepared with various morphological structures depending on the Ag-to-MA ratios. Furthermore, the electrodes modified with mesoporous Ag-MA nanowires could display stable and sharp electrochemical peaks of solid-state AgCl at a considerably low potential approaching zero, thus circumventing any interference from possibly coexisting electroactive substances in the background. More importantly, the yielded AgCl signals would decrease selectively induced by sulfides through the specific sulfide-chloride replacement reactions toward the transferring of AgCl into non-electroactive Ag2S. The developed electroanalysis strategy could facilitate the selective detection of multiple sulfides (i.e., S2- or H2S, Sx2-, cysteine, and S2O32-) in the complicated media with high-level salts such as blood and wastewater, showing a linear concentration range from 0.50 to 512 µM as exemplified for S2- ions in blood. Such an electroanalysis device equipped with the portable electrochemical transducer can be tailored for the field-deployable monitoring of a variety of sulfides in clinical and environmental analysis fields.