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Purpose: This study investigated the spatial and temporal changes of elemental concentrations and their influencing factors, based on geochemical analysis of four sediment cores collected from the eastern shelf of Hainan Island, South China Sea, with different distance gradients from the coast. Methods: Samples used in the study, the four sedimentary cores C1, C2, C3, and C4, were all collected from the eastern Hainan shelf in the South China Sea. The concentrations of trace elements were measured by inductively coupled plasma-mass spectrometry (ICP-MS). We use X-ray fluorescence spectrometer (XRF) to measure concentrations of major elements. Combined with MS, TN, TOC, and particle size data, and then, multiple statistical analysis methods including correlation, principal component, and cluster analyses, these are comprehensively used. Results: Spatially, the contents of metallic elements are closely related to offshore distance. In terms of temporal distribution, the concentrations of Cu, Zn, As, Pb, Ni, and Cr overall increase from the bottom toward the surface. Conclusion: The cores show a simultaneous increase with the economic and social development of Hainan Island and the implementation of related policies. The metallic and metalloid elements in the sediments are mainly affected by the input of terrigenous debris and maritime materials. Redox conditions may also influence the geochemical characteristics of some elements such as As and Cr. [ABSTRACT FROM AUTHOR]

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This study aims to describe the relationship among heat input, microstructural evolution, and impact toughness in the simulated coarse-grained heat-affected zones of X90 pipeline steel under different heat inputs varying from 10 to 50 kJ/cm. Optical microscopy, transmission electron microscopy, and electron backscatter diffraction were performed for microstructure observation. As the heat input increases, the lath bainite expenses at the increase of granular bainite, which makes the samples fracture from ductile to brittle. The impact toughness was increased to a peak value of 273 ± 17 J when the heat input was increased to 25 kJ/cm, and was markedly decreased with increasing heat input. The toughness was deteriorated by the coarse-stringer and massive martensite/austenite constituent with a large grain size when the heat input was larger than 30 kJ/cm. The average efficient grain size (EGS) was 3.6, 3.7, and 4.3 μm with heat inputs of 10, 25, and 40 kJ/cm, respectively. The EGS is significantly smaller than the prior austenite grain size of 22.8, 26.8, and 31.2 μm. In addition, the precipitate is Nb-rich (Ti, Nb) C with a circular morphology modified to Ti-rich (Ti, Nb) C with a rectangular morphology and the size obviously increases, which also causes the toughness to deteriorate. [ABSTRACT FROM AUTHOR]

Atmospheric particulate matter (PM) has a significant impact on both the natural environment and human health. Iron is one of the most abundant elements in the earth's crust, playing an important role in geochemical processes, and is also an important trace component in atmospheric PM. In recent years, with the rapid development of non-traditional (metal) stable isotope technologies, new solutions and methods for the source apportionments of heavy metal elements have been put forward. Stable iron isotope analysis has become an effective tool to trace iron in atmospheric particles. This review paper briefly summarizes the recent progress of atmospheric iron isotope geochemistry. We show that some of the major natural and anthropogenic PM sources have different iron isotopic compositions. A Bayesian isotopic mixing model MixSIAR was used to quantitatively re-evaluate the contributions of different sources to iron in both urban and marine aerosols based on iron isotopic data in the literature. The results highlight the value of stable iron isotope analyses as an effective tool in the source apportionment of atmospheric aerosols. [ABSTRACT FROM AUTHOR]

Nitrogen-containing species are major components in atmospheric aerosols. However, little is known about the sources of N-containing aerosols over high mountainous regions, especially for organic nitrogen (ON). This study aims to reveal the emission sources of both inorganic and organic nitrogen in tropospheric aerosols atop Mt. Tai, China, and to improve our understanding of the N cycle imbalance in the North China Plain (NCP). Total suspended particle (TSP) samples were collected on a daytime/nighttime basis in spring 2017 and were investigated for the concentrations and stable N isotopic compositions of total nitrogen, NH4+, NO3− and ON. Our results show that the concentrations of N-containing compounds were higher in daytime than nighttime, mainly resulting from mountain–valley breezes and the changes of planetary boundary layer height. However, no significant day/nighttime changes were found for their corresponding δ15N values, indicating similar contributions from different N sources between day and night. The MixSIAR Bayesian stable isotope mixing model results suggest that the most important emission source of NH3 for aerosol NH4+ was agriculture, followed by fossil fuel-related sources, human waste and biomass burning. Aerosol NO3− was mainly formed from combustion and mobile emitted NOx. Interestingly, the isotopes of ON suggest that ON were very likely firstly of primary origin. Our study reveals the characteristics of reactive N emission sources and helps understand the regional transport of tropospheric N-containing aerosols in the NCP. [ABSTRACT FROM AUTHOR]

Photolysis of the widely used beta-blocker propranolol (PRO) was investigated in the presence of fulvic acid (FA) and inorganic ions under simulated solar irradiation. PRO undergoes direct photolysis proceeding mainly via degradation of the triplet excited state, 3PRO*. FA and inorganic ions inhibited photolysis of PRO in the order of FA > Fe3+ > Cl− > Ca2+ > Mg2+ > NO3− > K+. An antagonistic effect between FA and inorganic ions toward the suppression of PRO photolysis was exhibited. The binding behaviors of PRO, FA, and inorganic ions were examined through fluorescence quenching experiments, which showed that inorganic ions affected the binding between FA and PRO through competing for the binding sites of FA or PRO. The correlation analysis demonstrated a positive correlation between the binding constant (KOC) of FA-PRO and the inhibition rate of FA on PRO photolysis. The observed rate constants of photolysis (kobs) have opposite correlations with the concentration of singlet oxygen (1O2). These findings strongly suggest that inorganic ions decrease the inhibition effect of FA on PRO photolysis via restraining the complexation of FA-PRO and production of 1O2. [ABSTRACT FROM AUTHOR]

We measured total mercury (Hg) and selenium (Se) concentrations as well as stable nitrogen (N) isotopic composition in flyingfish and squid muscle tissues from the eastern Indian Ocean and western South China Sea. The results showed that the mean Hg concentration in squid muscle from the western South China Sea was lower than that in the eastern Indian Ocean. The Hg concentrations in flyingfish and squid muscle samples were positively correlated with organism size (length and weight) and δ15N in all the study areas. Furthermore, we found a negative correlation between Se and Hg in molar content of flyingfish and squid muscle from the western South China Sea. The Se:Hg molar ratio was significantly negative correlated with fish weight and δ15N, suggesting that the Se:Hg molar ratio decreases with the increase of fish size and trophic level in the food web. [ABSTRACT FROM AUTHOR]

Lamellar tin deposits were prepared by galvanostatical electroplating from the aqueous acidic-sulfate bath, with gelatin and benzalacetone dissolved in ethanol (A) as additive, and their morphologies were investigated by scanning electron microscopy. Cathodic polarization curves revealed that the absorbability of A on the cathode surface was higher than that of gelatin. X-ray diffraction analysis indicated preferred orientations of tin growth led to the formation of lamellar structure and distortion of tin lattice. The growth mechanism of lamellar tin was also discussed. [ABSTRACT FROM AUTHOR]