Seasonal metal fluxes derived by the interaction of surface water and groundwater in an aquaculture estuary

Submarine groundwater discharge(SGD)plays a major role as a conveyor of metals to coastal waters.However,the seasonal change of metal fluxes derived through SGD is unclear.Here,we evaluated the behaviours and fluxes of trace metals(Mn,Fe,Ba,Pb,U,Cr,Zn,Cu)in an estuary under different seasonal conditions.The behaviours of trace metals revealed that SGD was the source of Mn(3.51 mmol/(m^(2)·d)),Fe(0.174 mmol/(m^(2)·d))and Ba(0.024 mmol/(m^(2)·d)),but the Cu sink(−0.55μmol/(m^(2)·d))and other metals exhibited a seasonal source‒sink conversion.The seasonal variation of dissolved organic matter and the fresh groundwater proportion in subterranean estuaries may have an important effect on metals fluxes especially for the Fe,Mn and Ba.Our result shows that the single seasonal metal fluxes estimation applied to the annual scale will cause a large deviation,up to 3.6 times for Fe,5.5 times for Mn,and 15 times for Ba.Therefore,the influence of seasonal fluctuations on SGDderived metal fluxes cannot be ignored,and our findings will be important for comprehending the metal budget and cycle in nearshore environment.

Ultrastructural characterization of avian influenza A(H7N9) virus infecting humans in China

Dear Editor,In March 2013,the first 3 cases of severe disease dueto a novel avian-origin influenza A(H7N9)virus weredetected in the Chinese provinces of Shanghai and Anhui(Gao R,et al.,2013).A total of 339 laboratory-confirmedcases with 100 deaths were reported until January 142014(WHO,2014).To the best of our knowledge,thisis the first time that human infection with the avian in-fluenza A H7N9 subtype has been detected.Prior to

Morphology and structural dynamics of amyloid beta 42 assembly in vitro

Amyloid β42 （Aβ42） aggregation plays a key role in the pathogenesis of Alzheimer＇s disease. However, the morphology and structural dynamics in different stages of Aβ42 assembly are not well known. To investigate the dynamic properties of morphological and structural changes in the aggregation process of Aβ in vitro, transmission electron microscopy, western blot analysis and circular dichroism were used to observe the changes in morphology, immunoreactivity and secondary structure during Aβ aggregation, respectively. Results demonstrated that at 24 hours following Aβ42 aggregation in vitro, the structures of spherical granules from 5 to 10 nm and coils from 20 to 30 nm were visualized by transmission electron microscopy. Different immunoreactivities of the oligomers and fibers were detected by western blot analysis. The dynamic changes of the α-helix to β-sheet were confirmed by circular dichroism spectra. The dynamic properties of the morphological and structural changes in the aggregation process of Aβ42 in vitro were analyzed, which contributed to the identification of stable conditions of Aβ42 oligomer formation.

Spatial distribution and behavior of dissolved selenium speciation in the South China Sea and Malacca Straits during spring inter-monsoon period

Selenium(Se)has been recognized as a key trace element that is associated with growth of primary producers in oceans.During March and May 2018,surface water(67 samples)was collected and measured by HG-ICP-MS to investigate the distribution and behavior of selenite[Se(Ⅳ)],selenate[Se(Ⅵ)]and dissolved organic selenides(DOSe)concentrations in the Zhujiang River Estuary(ZRE),South China Sea(SCS)and Malacca Straits(MS).It showed that Se(Ⅳ)(0.14–3.44 nmol/L)was the dominant chemical species in the ZRE,related to intensive manufacture in the watershed;while the major species shifted to DOSe(0.05–0.79 nmol/L)in the MS,associated with the wide coverage of peatland and intensive agriculture activities in the Malaysian Peninsula.The SCS was identified as the northern and southern sections(NSCS and SSCS)based on the variations of surface circulation.The insignificant variation of Se(IV)in the NSCS and SSCS was obtained in March,potentially resulting from the high chemical activity and related preferential assimilation by phytoplankton communities.Contrastively,the lower DOSe concentrations in the SSCS likely resulted from higher primary production and utilization during March.During May,the concentration of Se(Ⅳ)remained low in the NSCS and SSCS,while DOSe concentrations increased notably in the SSCS,likely due to the impact of terrestrial inputs from surface current reversal and subsequent accumulation.On a global scale,DOSe is the dominant Se species in tropical oceans,while Se(Ⅳ)and Se(Ⅵ)are major fractions in high-latitude oceans,resulting from changes in predominated phytoplankton and related biological assimilation.