Geochemical characteristics of rare earth elements in the surface sediments from the Spratly Islands of China

Hydrological Regime, Provenance, and Impacts on Cultural Development at Changsha Kiln Archaeological Site since 1300 a, Lower Xiangjiang River, China

Changsha kilns were exported to more than 20 countries and regions and were an essential part of the culture in the central Yangtze River during the late Holocene. Reconstructing the hydrological landform and sedimentary history of its surrounding areas (Shizhu) is significant for further constraining any links between regional paleoenvironmental change and the human−land relationship in the lager river valley. To examine paleo−hydrological and provenance evolution, the rare earth element (REE) and trace element ratio from the Shizhuping (SZP) section were analyzed. The SZP section records the paleo−hydrological evolution over 1300 years: river network cutting plain landscape—Shizhu Lake—river floodplain—Shizhu Lake reformation—Shizhu flat. This section was labeled as stages IV to I, respectively. The deposition of stages IV was wind and dust accumulation during the Last Glacial. The provenance of stages III (1288–1094 a.BP) was wasted from the ceramic production process. The layer of stage II (1094–380 a.BP) was in two parts. In stage II−2 (1094–890 a.BP), provenance was dominated by granite. Sedimentary rocks became the source of stage II−1 (890–380 a.BP). In stages I (380 a.BP–), the primary material sources were anthropogenic bedding and weathering erosion deposits around the slope. During the Medieval Warm Period, the climate was warm and humid, and the rising water level of the Xiangjiang River led to the emergence of lakes in the Shizhu area. The migration of northern China into Changsha kiln brought new technology and labor. In the late Five Dynasties, the climate turned dry, and the falling water level of the Xiangjiang River caused Changsha kiln to lose its commercial wharf.

Variation in Bacterial Community Structures and Functions as Indicators of Response to the Restoration of Suaeda salsa: A Case Study of the Restoration in the Beidaihe Coastal Wetland

Microbes play an essential role in the restoration of degraded coastal wetlands. However, few studies have focused on the role of key bacteria in the restoration process. Here, Suaeda salsa was planted to recover the biodiversity in the degraded Beidaihe coastal wetland. We monitored omics and soil environmental factors to understand the complex relationship between the bacterial community and wetland health during the restoration period. After planting S. salsa in the degraded area, the soil quality was improved in the later stage of restoration (LPR). Bacterial α-diversity increased with restoration and was positively correlated with TOC. Proteobacteria is the dominant bacterial phylum during the restoration period, and Bacteroidetes, Planctomycetes, Gemmatimonadetes, and Acidobacteria were sensitive to the planting restoration. Random forest analysis picked 30 key OTUs, showing the key bacterial variation of successful restoration. The result indicated that the sum of the relative abundances of key bacterial OTUs was more than 2% in the health wetland. The β-diversity showed that the growth of S. salsa reshaped the soil bacterial community structure and function in the LPR, which recovered to the level in the control area. Putative biogeochemical functions showed that symbionts and aromatic compound degradation were dominant bacterial functions in the growth period of S. salsa. Our study proposed a new indicator to assess wetland health and the planting restoration of S. salsa increased bacteria groups with the ability of symbionts and aromatic compound degradation in the Beidaihe coastal wetland. This study expanded our knowledge of coastal wetland restoration and its ecological contributions.

Effects of Lanthanum on the Photosystem II Energy Fluxes and Antioxidant System of Chlorella Vulgaris and Phaeodactylum Tricornutum

The rare earth elements are widely used in agricultural and light industry development. They promote the growth of crop seedlings, enhance root development and change the metal properties. Due to the large amount of rare earth minerals mined in China, rare earth elements have been detected in both coastal and estuary areas. They cause pollution and threaten the health of aquatic organisms and human beings. This study investigates the effects of lanthanum on two marine bait algae, and analyzes the changes in the photosynthetic and antioxidant systems of the two algae. The results show that rare earth elements have significant inhibitory effects upon the two algae. The OJIP kinetic curve value decreases with an increasing concentration of La(NO3)3 ·6H2O. The parameters of the fluorescence value were analyzed. The ABS/RC increases and the DI0/RC decreases during the first 24 h after exposure. The effects on the photosynthetic and antioxidant systems at low concentrations (both EC10 and EC20) show that the TR0/ABS increases, and the ET0/RC, ABS/RC, and DI0/RC has a decreasing trend after 30 min. However, after 24 h, normal levels were restored. In addition, the study finds that the TR0/ABS increases after 24 h, leading to an increase in reactive oxygen species. The antioxidant system analysis also confirms the increase in the activities of antioxidant enzymes, such as SOD and GSH. The experiment is expected to support the marine pollution of rare earths and the theoretical data of the impact on marine primary producers.

Determination of trace metals and analysis of arsenic species in tropical marine fishes from Spratly islands

Trace metal contents in 38 species of tropical marine fishes harvested from the Spratly islands of China were determined by microwave digestion and inductively coupled plasma mass spectrometry analysis. Arsenic species were determined by high-performance liquid chromatography and inductively coupled plasma mass spectrometry analysis. The average levels of Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Pb, and U in the fish samples were 1.683, 0.350, 0.367, 2.954, 36.615, 0.087, 0.319, 1.566, 21.946, 20.845, 2.526, 3.583, 0.225, 0.140, and 0.061mg·kg^-1, respectively; Fe, Zn, and As were found at high concentrations. The trace metals exhibited significant positive correlation between each other, with r value of 0.610-0.852. Further analysis indicated that AsB (8.560-31.020mg·kg^-1) was the dominant arsenic species in the fish samples and accounted for 31.48% to 47.24% of the total arsenic. As(III) and As(V) were detected at low concentrations, indicating minimal arsenic toxicity.