Source or sink? A study on the methane flux from mangroves stems in Zhangjiang estuary, southeast coast of China

Mangrove ecosystems are an important component of "blue carbon". However, it is not clear whether the stems play roles in the CH₄ budget of mangrove ecosystems. This study investigated the CH₄ emission from mangrove stems and its potential driving factors. We set up six sample plots in the Zhangjiang Estuary National Mangrove Nature Reserve, where Kandelia obovata, Avicennia marina and Aegiceras corniculata are the main mangrove tree species. Soil properties such as total carbon content, redox potential and salinity were determined in each plot. The dynamic chamber method was used to measure mangrove stems and soil CH₄ fluxes. Combined field survey results with Principal Component Analysis (PCA) of soil properties, we divided the six plots into two sites (S1 and S2) to perform statistical analyses of stem CH₄ fluxes. Then the CH₄ fluxes from mangrove tree stems and soil were further scaled up to the ecosystem level through the mapping model. Under different backgrounds of soil properties, salinity and microbial biomass carbon were the main factors modified soil CH₄ fluxes in the two sites, and further affected the stem CH₄ fluxes of mangroves. The soil of both sites are sources of CH₄, and the soil CH₄ emission of S2 was about twice higher than that of S1. Results of upscaling model showed that mangrove stems in S1 were CH₄ sinks with -105.65 g d^-1. But stems in S2 were CH₄ sources around 1448.24 g d^-1. Taken together, our results suggested that CH₄ emission from mangrove soils closely depends on soils properties. And mangrove stems were found to act as both CH₄ sources and CH₄ sinks depend on soil CH₄ production. Therefore, when calculating the CH₄ budget of the mangrove ecosystem, the contribution of mangrove plant stems cannot be ignored.

Co-crystallization of hemimellitic acid with 4,4'-bipyridine forming a pillar-layered hydrogen-bonded network

Co-crystallization of hemimellitic acid (benzene-1,2,3-tricarboxylic acid) dihydrate (H3HMA.2H2O) with 4,4'-bipyridine (4,4'-bpy) affords the 1:1 co-crystal benzene-1,2,3-tricarboxylic acid-4,4'-bipyridine (1/1), H3HMA.4,4'-bpy or C9H6O6.C10H8N2. Strong O-H...O hydrogen bonds connect the acid molecules to form a one-dimensional zigzag chain, around which the 4,4'-bpy components are fixed as arms via O-H...N interactions, resulting in a ladder motif. Through weak C-H...O non-covalent forces, the resulting acid layers are extended into a three-dimensional pillar-layered architecture supported by rod-like 4,4'-bpy components. The influence on hydrogen-bonding models is also discussed, with the discovery of an unexpected interaction motif that does not follow the routine hydrogen-bonded hierarchical rule in the construction of an acid-base co-crystal.

Multicentric biatrial myxoma in a young female patient: case report

We report a case of multicentric, biatrial cardiac myxoma in a 29-year-old female who complained of exertional dyspnea, abdominal distension and peripheral edema. Any other associated skin lesions, breast mass or endocrine disorder presenting complex form were' not seen on her. Also, there was no contributory medical history, hypertension and diabetes mellitus. By using transthoracic echocardiography, we identified a biatrial myxoma attached to the interatrial septum. During surgical excision, we found a large right atrial myxoma with extension through the fossa ovalis into the left atrium and small myxoma attached to the right atrial free wall. After successful resection of interatrial septum and free wall, atrial septal defect was created during the resection and safely repaired by bovine pericardial patch.