Influence of biodeposition by suspended cultured oyster on the distributions of trace elements in multiple media in a semi-enclosed bay of China.

It remains unclear how the suspended non-fed bivalve mariculture will alter the coastal transfer and cleaning process of trace elements, the non-degradable contaminants, which have been reported to accumulate in sediment from bivalve mariculture areas. Herein, we set up a field in situ comparative test in the suspended oyster (Crassostrea plicatula) farming area (OF) and reference area (RA) of Xiangshan Bay to verify our hypothesis that the biodepositon of suspended oysters would consolidate trace elements from the water column and transport them to the sediment. Distribution of trace elements in multiple media of biodeposits (BDs), settling particles (SPs), sediments (SEs), and seawater demonstrate that the accelerated deposition of BDs which enriched trace elements from the water column by oysters filtering suspended particles led to trace elements accumulation in SEs from OF. Additionally, As, Cd, Co, Cr, Cu, Ni, V, and Zn were strongly regulated by this process with significant (p < 0.05) higher concentrations in SEs from OF (10.96, 0.20, 13.98, 82.40, 38.47, 38.22, 108.57, and 111.20 µg/g, repectively) than those from RA (9.43, 0.13, 11.76, 63.30, 30.34, 29.55, 86.59, and 100.24 µg/g, repectively), but the extent was different for Mn, Mo, Pb, and W with concentrations in SEs from OF (737.37, 0.81, 30.98, and 3.96 µg/g, repectively) and RA (765.25, 0.69, 31.27, and 3.34 µg/g, repectively), especially for Rb and Sr with concentrations in SEs from OF (131.13 and 96.24 µg/g, repectively) and RA (142.21 and 161.10 µg/g, repectively), due to their geochemical and geophysical properties. Moreover, the harvest of hyper-accumulated oysters as a sink for removing trace elements from water column cannot hide the impact of this process.

Composition and sources of suspended particles in the Pacific Arctic region.

During the 6th (2014) and 7th (2016) Chinese Arctic Expedition (CHINARE), samples of suspended particulate matter (SPM) were collected from both surface (depth: <1.0 m) and subsurface (depth: approximately between 10 and 150 m) waters over the northern shelf of the Bering Sea and in the western Arctic Ocean. To investigate the distribution and sources of organic matter in both the surface water and the vertical profile, the concentration and stable carbon isotopic composition of SPM, particulate organic carbon (POC), and particulate nitrogen (only in surface water samples) were determined, and some particle samples were selected for examination using scanning electron microscopy. Results showed apparent geographical partitioning and temporal variation in both the concentration and the composition of SPM. Higher SPM concentrations were observed in nearshore, shelf break, and sea ice edge areas; the distribution of POC concentration displayed a similar pattern, with higher values found from the northern part of the Bering Shelf to southern parts of the Chukchi Shelf. In surface water, SPM mainly comprised clay and detrital minerals with higher POC contents, lighter δ13C values, and higher POC/PN ratios, indicating organic matter predominantly derived from terrestrial sources in areas south of St. Lawrence Island and north of 73°N. The downward trend of heavier δ13C values, together with reduction in clay and detrital minerals, suggests that vertical transport of SPM is hindered by stratification, resulting in transport of terrestrial materials toward northern basin areas. In the Chukchi Slope and Canada Basin areas, extremely light δ13C values (as low as -33.41‰ PDB) were mainly observed at depths of 20-60 m, where the Polar Mixed Layer (PML) intersects with the Upper Halocline Layer (UHL). Under the condition of low sea ice extent in 2016, the POC-δ13C values were heavier in the PML than in the UHL in the Chukchi Slope and Canada Basin areas. These findings provide insights into the sources, transport, and fate of organic matter in the Pacific Arctic region, which have important implications for understanding the biogeochemical cycles and ecosystem dynamics in this remote and rapidly changing environment.

An overlooked source of nanosized lead particles in the atmosphere: Residential honeycomb briquette combustion.

Atmospheric lead (Pb) pollution has attracted long-term and widespread concerns due to its high toxicity. The definite source identification of atmospheric Pb is the key step to mitigate this pollution. Here, we first report an overlooked source of atmospheric nanosized Pb particles using transmission electron microscopy and bulk sample analyses, finding that residential honeycomb briquette combustion emits large numbers of nanosized Pb-rich particles. We found that 33.7 ± 19.9 % of primary particles by number from residential honeycomb briquette combustion contains the crystalline Pb particles. These Pb-rich particles range in size from 14 to 956 nm with a mean diameter of 117 nm. Compared with raw coal chunks, honeycomb briquette combustion could emit less carbonaceous particles, but largely increase nanosized Pb particle emissions. This result is attributed to two key factors: (1) higher Pb content in honeycomb briquette (63.6 µg g-1) than that in coal chunk (8.5 µg g-1), and (2) higher Pb release rate for honeycomb briquette (62.3 %) caused by honeycomb structure than that for coal chunk (20.1 %). This study highlights that atmospheric and health implications of high emissions of toxic nanosized Pb from honeycomb briquette should be paid more attention in future research on ambient and indoor airs.

[Development of ceramic standard samples used for X-ray fluorescence spectrometric analysis].

The preparation of 17 kinds of ceramic standard samples (CSS) is introduced briefly in the present paper, and the experimental results of the sintered CSS by using EPMA and XRF are discussed in detail. The conclusions can be mainlydrawn that the CSS, which have high density, low water absorption and good homogeneity of element distribution, have similar phase structure (or matrix) to the bodies of ancient ceramics, and perfectly meet the requirements of being used as ceramic standard samples. This set of CSS are expected to play an important role in x-ray fluorescence spectrometric quantitative analysis of Na2O, MgO, Al2O3, SiO2, K2O, CaO, TiO2 and Fe2O3 in the body of ancient ceramics and can provide accurate and reliable data for study and identification of ancient ceramics.

Low-temperature synthesis of high-ordered anatase TiO2 nanotube array films coated with exposed {001} nanofacets.

High-ordered anatase TiO2 nanotube array films coated with exposed high-reactive {001} nanofacets were fabricated by a modified hydrothermal method using amorphous anodic TiO2 nanotube arrays (ATONAs) as starting materials. It was found that the reaction between gas phase HF and solid ATONAs played a key role in the transformation process from amorphous to anatase TiO2, and the TiO2 tubular structure kept unchanged during the surface modification with an exposed {001} facets up to 76.5%, which could be attributed to the low reaction temperature of 130 °C. Our study provided a novel route for the facile preparation of {001} facets exposed anatase TiO2.