Compared with traditional chemical analysis methods,reflectance spectroscopy has the advantages of speed,minimal or no sample preparation,non-destruction,and low cost.The present study explored the application of the reflectance spectroscopy within near ultraviolet-visible-near infrared region to predict bio-element compositions in the ornithogenic sediments from the maritime Antarctic.A total of 106 samples were taken from four ornithogenic sediment cores on the Ardley Island of Antarctica,68 samples were used for building calibration equation,and 38 for prediction of nine bio-elements including P,Ca,Cu,Zn,Se, Sr,Ba,F and S.Three multivariate statistical analysis techniques,including stepwise multiple linear regression（Stepwise-MLR）,principal component regression（PCR） and partial least squares regression（PLS） were used to develop mathematical relationships between the spectral data and the chemical reference data.The results showed that the regression models constructed by PCR and PLS models have no significant differences,and obviously supervisor to Stepwise-MLR.The correlations between spectra-predicted and chemically analyzed concentrations of nine bio-elements are statistically significant,and the concentration-versusdepth profiles predicted from reflectance spectra using PLS calibration model are consistent with those from actual chemical analysis.These results demonstrated the feasibility of using reflectance spectroscopy to infer bio-element concentrations in the ornithogenic sediments,and thus it is suggested that the reflectance spectroscopy could provide a rapid and valuable technique to indirectly identify whether the sediments were influenced by penguin droppings in the Antarctic region.
According to palaeoclimatic and modern instrumental data,numerous studies have indicated that the Arctic climate has undergone a significant warming during the past 100 years,and this may lead to significant impact on the fragile lake ecosystem.In this study,we collected a lake sediment core from the Nylesund of Svalbard and determined the concentrations of four pigments including chlorophyll derivatives,total carotenoids,oscillaxanthin and myxoxanthophyll in the sediments.Combined with other physical and chemical proxies such as calcium carbonate,total organic carbon,biogenic silicon etc.,we have reconstructed the historical changes of lacustrine primary productivity in Ny-lesund,especially for the past 100 years.The results showed that during the period of Little Ice Age（LIA）,the climate was unfavorable for the growth of the lake algae,and thus the lacustrine productivity declined.This result was supported by the relatively low contents of pigment and biogenic silica in the sediments.In contrast,the contents of total organic carbon（TOC） and sediment pigments increased significantly in the upper 5 cm（-1890AD）,reflecting the rapid growth of the lake algae,thus the great increase of lacustrine primary productivity,corresponding to the warming climate after LIA.However,the biogenic silica in the upper sediments still had a relatively low level,and this might be related to the growth competition with other algae species.Over the past 100 years,the ratio of Osc/Myx in the sediments decreased continuously,indicative of durative increase of myxoxanthophyll in blue-green algal pigments,and this might imply that the human activity had enhanced the nutrition level of the lake in the Arctic region.
The levels and depth distributions of As, Cd, Cu, Zn, Pb, Hg, Fe and Mn in two sediment cores DY2 and DY4 collected from the ＂Cattle Pond＂ of Dongdao Island, South China Sea, were determined and analyzed with the main objective to identify the sources of these elements and evaluate the corresponding sedimentological and geochemical processes. Lithological characters and sedimentary parameters such as LOI950℃, CaO, LOI550℃ and TOC indicate that the depth of 96 cm and 87 cm are the critical points for DY2 and DY4 cores, respectively. As, Cd, Cu, Zn, Hg and P are remarkably enriched in the ornithogenic sediments above the critical depth points; their concentration-versus-depth profiles are similar to those of TOC and LOI550℃; the ratios of As, Cd, Cu, Zn, Hg over Ca are significantly correlated with P/Ca. Statistical and comparative analyses of these elements＇ levels in the ornithogenic sediments of DY2 and DY4 strongly suggest that seabird droppings are the main source of these elements. Additionally, for the upper sediment layers of DY2 and DY4 cores, Fe oxide sorption mechanism, like organic matter, may also play an important role in the abundances of heavy metals. Heavy metal Pb has geochemical characteristics distinctly different from those of As, Cd, Cu, Zn, Hg and P, and its isotope composition indicates an origin of anthropogenic emissions from the surrounding countries. These geochemical characteristics in the orinithogenic sediments of Xisha Islands are compared with the studies in the remote Antarctic and Arctic regions.
We collected two lake sediment cores （MC and DM） from the East Antarctic region for analysis of biogenic silica and other biogeochemical parameters （e.g., organic matter, C, N, S, H）. Based on synthetically comparative research, we focused on the potential application of biogenic silica （BSi） for the reconstruction of paleo-primary productivity in the East Antarctic lakes. Analytical results showed that a large number of diatoms were well preserved in the freshwater lake sediments, and that concentrations of biogenic silica displayed notable fluctuations over different water depths. The content of biogenic silica had a consistent profile over water depth, and this pattern changed with organic matter, reflecting their potential as eco-environmental proxies. Low lev- els of BSi and organic matter indicated reduction of lake algal production, and corresponded to decreased lake primary productivity. Due to the fragile ecosystem state and limited contribution of terrestrinl organic matter in the East Antarctic lakes, the contents of biogenic silica in the lacustrine sediments can sensitively indicate the evolutionary history of paleo-primary productivity. Overall, BSi is an ideal proxy for the reconstruction of past eeo-environmental change recorded in the lacustrine sediments on East Antarctica.
