Xijie Yin

The source of natural and anthropogenic heavy metals in the sediments of the Minjiang River Estuary (SE China): implications for historical pollution.

Two sedimentary cores in the Minjiang River estuary (SE China) are documented for grain size, clay minerals, heavy metals, magnetic parameters and Pb isotopes to investigate the source and historical variation of heavy metals. The MJK9 core was collected outside of the Minjiang River estuary, and the core is composed of mixed sediments, of which ~70% from the Yangtze River and 30% from the Minjiang River. It is thus difficult to be used for tracing the human activity along the Minjiang River. In contrast, the sediments of MJK16 core which was collected in a nearshore area are primarily from the Minjiang River. The enrichment factors of the sediments were <1.5, indicating minor pollution. The results indicate that the sediments of the MJK16 core have Cu and Pb concentrations increasing since 1980, associated with the increase of magnetic mineral concentration and (206)Pb/(207)Pb and (206)Pb/(208)Pb of the sediments. We compared the Pb isotopic compositions between our results and those for the deposit mining in the Minjiang River basin, and aerosols and coal dust in south China, and considered that Pb in the sediments of the MJK16 core was derived primarily from weathered rocks as well as industrial emission (e.g. coal combustion). The sediments have anthropogenic Pb concentrations ranging from 6% in 1950 to 23.7% in 2010, consistent with the impact of rapid urban and industrial development in China.

The U–Pb ages and Hf isotopes of detrital zircons from Hainan Island, South China: implications for sediment provenance and the crustal evolution

In situ U–Pb dating and Hf isotopic of detrital zircons from beach sediments of Yalong Bay were analyzed to trace sedimentary provenance and reveal the crustal evolution of Hainan Island in South China. The grain size distribution of the sediments displays a clear single-peak feature, indicating the sediments were formed under the same condition of hydrodynamic force. The detrital zircons had Th/U ratios of greater than 0.1, and REE pattern displayed a positive Ce anomaly and a negative Eu anomaly, indicating that these zircons are predominantly of magmatic origin. The U–Pb spectrum of detrital zircons mainly peaked at the Yanshanian (96–185xa0Ma), Hercynian–Indosinian (222–345xa0Ma) and Caledonian (421–477xa0Ma). A portion of the detrital zircons were of Neoproterozoic origin (728–1,003xa0Ma), which revealed that the basement in the eastern region of Hainan Island was mainly of Neoproterozoic, with rare Archean materials. The positive εHf(t) values (0 to +10.1) of the Neoproterozoic detrital zircons indicated that the juvenile crust grew in the southeastern Hainan Island mainly during the Neoproterozoic period. The Neoproterozoic orogeny in the southeastern part of the island (0.7–1.0xa0Ga) occurred later than in the northwestern region of the island (1.0–1.4xa0Ga). Importantly, the Grenvillian orogeny in the southeastern area of Hainan Island shared the same timing with that of the western Cathaysia Block; i.e., both areas concurrently underwent this orogenic event, thereby forming a part of the Rodinia supercontinent. Afterwards, the crust experienced remelting and reworking during the Caledonian Hercynian–Indosinianand Yanshanian accompanied by the growth of a small amount of juvenile crust.

Remote-sensing observations of Typhoon Soulik 2013 forced upwelling and sediment transport enhancement in the northern Taiwan Strait

The Taiwan Strait plays an important role in water and sediment exchange between the East China Sea and the South China Sea. On 13 July 2013, Typhoon Soulik crossed the Taiwan Strait, causing a significant impact on the strait’s marine system. In this article, we document the use of remote-sensing data to study this impact by comparing sea surface temperature (SST), spatial distributions and concentrations of chlorophyll (Chl-a), and total suspended matter (TSM) in the strait over different time periods. During and after the typhoon, the TSM of the waters near the Minjiang estuary dramatically increased, while Chl-a and SST significantly decreased. To the southeast of Pingtan Island, the SST decreased and Chl-a significantly increased, causing strong upwelling that lasted eight to ten days. To the northwest of Taiwan Island, Chl-a and the TSM of the coastal waters dramatically increased. The strong cyclonic wind-stress of the typhoon enhanced heat exchange between the water and the atmosphere, and a large amount of rainfall and run-off significantly decreased the SST. During the typhoon, the increased sediment discharged into the strait by rivers, and the re-suspension of seafloor sediment, increased the concentration of TSM in the coastal waters. Seawater with relatively high sediment concentration was transported to the middle of the strait after being carried by wind-induced flows. In the waters near the typhoon’s path, especially in the upwelling area, nutrient-rich bottom water stirred by the typhoon promoted an outbreak of aquatic organisms and significantly increased the probability of a red tide occurrence.

Storm deposition layer on the Fujian coast generated by Typhoon Saola (2012).

Typhoons have a significant effect on the marine depositional environment and depositional process. In this paper, we used the high-resolution Chirp sonar sub-bottom profiler and radioisotope detection techniques to examine the storm-deposited layer formed in the seawater near the path of Typhoon Saola along the coast of Fujian, China. The thickness of the typhoon-deposited layer acquired using these two methods was 10–25u2009cm. The thickness, sediment grain size, and δ13C values of the deposited sedimentary layer indicated that it was mainly matter from the re-suspension and redistribution of seafloor sediments. The particle sizes of the sediments in the storm-deposited layer became coarser, indicating that the fine-grade compositions spread over a wider range out of the coastal zone.

Geochemical record of high emperor penguin populations during the Little Ice Age at Amanda Bay, Antarctica.

Emperor penguins (Aptenodytes forsteri) are sensitive to the Antarctic climate change because they breed on the fast sea ice. Studies of paleohistory for the emperor penguin are rare, due to the lack of archives on land. In this study, we obtained an emperor penguin ornithogenic sediment profile (PI) and performed geochronological, geochemical and stable isotope analyses on the sediments and feather remains. Two radiocarbon dates of penguin feathers in PI indicate that emperor penguins colonized Amanda Bay as early as CE 1540. By using the bio-elements (P, Se, Hg, Zn and Cd) in sediments and stable isotope values (δ(15)N and δ(13)C) in feathers, we inferred relative population size and dietary change of emperor penguins during the period of CE 1540-2008, respectively. An increase in population size with depleted N isotope ratios for emperor penguins on N island at Amanda Bay during the Little Ice Age (CE 1540-1866) was observed, suggesting that cold climate affected the penguins breeding habitat, prey availability and thus their population and dietary composition.

Geochemical analysis of sediments from a semi-enclosed bay (Dongshan Bay, southeast China) to determine the anthropogenic impact and source

The geochemical compositions of sediments in the Dongshan Bay, a semi-enclosed bay on the southeast coast of China, were obtained to identify pollutant sources and evaluate the anthropogenic impacts over the last 100 years. The results indicated that the metal flux had been increasing since the 1980s. Enrichment factor values (Pb, Zn and Cu) suggested only slight enrichment. The proportion of anthropogenic Pb changed from 9% to 15% during 2000-2014. Coal combustion might be an important contamination source in the Dongshan Bay. The historical variation in the metal flux reflected the economic development and urbanization in the Zhangjiang drainage area in the past 30 years. According to the Landsat satellite remote sensing data, the urbanization area expanded approximately three times from 1995 to 2010. The δ13C values (-21‰ toxa0-23‰) of the organic matter (OM) in the sediments indicated that the OM was primarily sourced from aquatic, terrigenous and marsh C3 plants. Nitrogen was mainly derived from aquatic plants and terrigenous erosion before the 1980s. However, the total organic carbon (TOC) contents, total nitrogen (TN) contents and δ15N had been increasing since the 1980s, which suggested that the sources of nitrogen were soil erosion, fertilizer and sewage. In addition, the TOC and TN fluxes in the Dongshan Bay had significantly increased since the 1980s, which reflected the use of N fertilizer. However, the TOC and TN fluxes significantly decreased in the past decade because environmental awareness increased and environmental protection policies were implemented.

Hydrodynamic and Biological Mechanisms for Variations in Near-Bed Suspended Sediment Concentrations in a Spartina alterniflora Marsh—a Case Study of Luoyuan Bay, China

Near-bed suspended sediment concentration (SSC) was measured at the margin and in the interior of a Spartina alterniflora marsh in Luoyuan Bay, a semi-enclosed embayment sheltered from the East China Sea, in January and July 2008. Variations in SSC at the two stations correlated to the tidal cycle: high SSC occurred in the early stage of the flood tide and the later stage of the ebb tide, while SSC was significantly lower at all other times. The SSC increased from the neap tide to the spring tide in both winter and summer. The high SSC in winter was primarily a result of stronger hydrodynamic processes, whereas the high SSC in summer was primarily attributable to biological activity. The particulate organic carbon (POC) in the S. alterniflora marsh of Luoyuan Bay primarily originates from freshwater and marine algae and phytoplankton, while the contribution of marsh detritus is limited. The contribution of POC to near-bed SSC is less than 5% in both winter and summer. During winter, the near-bed SSC was closely related to the bottom shear stress; therefore, variations in SSC were controlled by hydrodynamic processes. However, the correlation between bottom shear stress and near-bed SSC was poor in summer because of the interference of burrowing organisms during the late stage of the ebb tide. The maximum estimated contribution of turbid water flowing out of caves due to the biological activity of burrowing organisms was approximately 30.3xa0mgxa0L−1 or 20.2 to 50.5% with a mean value of 34.9% of total SSC at the late stage of the ebb tide. Our findings also suggest that the relative importance of hydrodynamic processes and biological activity can vary considerably between seasons.