An analysis of the components of the luminescence signals of selected polymineral and quartz samples from loess in western China and southern Tajikistan,and their suitability for optical dating

Previous luminescence dating studies on loess from China and Tajikistan have focused on the establishment of the regional chronology of the loess sequences. In order to improve the precision and accuracy of optical ages derived from the loess of the last glacial period in these regions, we have examined the components of luminescence signals in three loess samples from western China and southern Tajikistan. Our results show that the polymineral IRSL and post-IR OSL, and quartz OSL signals from loess of the two regions are represented by three components, which display different bleaching and growth characteristics. While the composition of the polymineral IRSL signals is similar between samples with the same age from the two regions, in the case of quartz there is significant discrepancy in the proportion of the fast and medium components of the OSL signals. Greater difference is observed in the composition of the polymineral post-IR OSL signals for the loess from the two regions. The three components of polymineral IRSL signals yield almost identical equivalent dose values as that derived from the total IRSL signal. An apparent agreement in equivalent dose is observed between the fast component of the polymineral post-IR OSL and the quartz OSL for the loess of western China but not in the loess of the same age from southern Tajikistan. The fast component of the quartz OSL yields an equivalent dose 25% higher than that based on the total signal for the sample from the base of the Late Pleistocene loess in southern Tajikistan. This demonstrates the importance of signal selection for an accurate luminescence dating of Central Asian loess.     

Assessment of nutrient sources and paleoproductivity during the past century in Longgan Lake,middle reaches of the Yangtze River,China

Total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) were determined in combination with stable isotope ratios of carbon and nitrogen (δ¹³C_Org, δ¹⁵N) in a 63 cm sediment core from Longgan Lake, located in the middle reaches of the Yangtze River, China. These geochemical and isotopic records provide a continuous history of lake productivity and trophic state of Longgan Lake since 1890. Variations of δ¹³C_Org, TOC, TN and TP indicate that primary productivity of Longgan Lake increased continuously during the last century and that the trophic state of the lake shifted from oligotrophic to mestrotrophic conditions accordingly. Anthropogenic sources of organic carbon (OC), nitrogen (N) and phosphorus (P) were distinguished from their natural background in the sediments using mass accumulation rates. Element mass accumulation rates suggested increased human activities in the lake’s catchment since 1950s, were especially the utilization of artificial fertilizers amplified the anthropogenic input of N and P into the lake. In the course of the improved availability of dissolved nutrients also primary productivity of Longgan Lake increased, resulting in an increase of the Suess-effect corrected organic carbon isotope ratios. δ¹⁵N of bulk sediments show a marked shift towards lower values around 1950 that has been attributed to the input of nitrogen from chemical fertilizers characterized by relatively depleted isotopic signatures into the lake.     

A geospatial framework to estimate depth of scour under buildings due to storm surge in coastal areas

Hurricanes and tropical storms represent one of the major hazards in coastal communities. Storm surge generated by strong winds and low pressure from these systems have the potential to bring extensive flooding in coastal areas. In many cases, the damage caused by the storm surge may exceed the damage from the wind resulting in the total collapse of buildings. Therefore, in coastal areas, one of the sources for major structural damage could be due to scour, where the soil below the building that serves as the foundation is swept away by the movement of the water. The existing methodologies to forecast hurricane flood damage do not differentiate between the different damage mechanisms (e.g., inundation vs. scour). Currently, there are no tools available that predominantly focus on forecasting scour-related damage for buildings. Such a tool could provide significant advantages for planning and/or preparing emergency responses. Therefore, the focus of this study was to develop a methodology to predict possible scour depth due to hurricane storm surges using an automated ArcGIS tool that incorporates the expected hurricane conditions (flow depth, velocity, and flood duration), site-specific building information, and the associated soil types for the foundation. A case study from Monmouth County (NJ), where the scour damages from 2012 Hurricane Sandy were recorded after the storm, was used to evaluate the accuracy of the developed forecasting tool and to relate the scour depth to potential scour damage. The results indicate that the developed tool provides relatively consistent results with the field observations.     

Paleoclimatic changes in southern Africa during the intensification of Northern Hemisphere glaciation: evidence from ODP Leg 175 Site 1085

Pliocene age sediments from Ocean Drilling Program Leg 175, Site 1085-A and B in the Cape Basin were analyzed to investigate the impact of the intensification of Northern Hemisphere glaciation (INHG) on the South Atlantic Benguela Current system from 4 to 2 Ma. Proxies for productivity (concentrations and mass accumulation rates of total organic carbon, carbon to nitrogen ratios, percent calcium carbonate, and percent biogenic silica) as well as weight percent sand (a proxy for preservation or winnowing) peak at 3.2, 3.0, 2.4, and 2.25 Ma. Normative calculations of allied trace and major elemental determinations indicate synchronous increases in productivity peaks, as well as high concentrations and accumulations of terrigenous sediments. Coeval increases in hemipelagic sedimentation and productivity indicators could be the result of enhanced eolian sedimentation resulting from strengthened winds, leading to elevated rates of upwelling and enhanced productivity. However, rapid burial, as indicated by high sedimentation rates, could also enhance preservation. The very high concentrations (>30%) and accumulations (up to 60 g/cm²/kyr) limit the likelihood that eolian sedimentation was the only transport mechanism, invoking an additional fluvial source. Rapid burial by either eolian or fluvial transport links these intervals of enhanced preservation and productivity with continental climate changes resulting from (1) increased winds and/or dust availability due to higher aridity in the Namibia/northern South Africa region; (2) lowered sea-level related to increased ice volume; (3) increased sediment load due to wetter conditions in the continental interior; or (4) some combination. Peaks at 3.2, 2.4 and 2.25 Ma are coincident with maximum precession, suggesting a link between hemipelagic sedimentation and enhanced monsoonal circulation over southern Africa. The Site 1085 sedimentary record during the INHG seems to be controlled by low-latitude processes linked to precession rather than hig-latitude processes.     

The cosmic ray energy spectrum between 10 and 10 eV

The energy spectrum of cosmic rays with primary energies between 10¹⁴ eV and 10¹⁶ eV has been studied with the CASA-MIA air shower array. The measured differential energy spectrum is a power law (dj/dE ∝ E^−y) with spectral indices γ of 2.66±0.02 below approximately 10¹⁵ eV and 3.00±0.05 above. A new method is used for measuring primary energy derived from ground-based data in a compositionally insensitive way. In contrast with some previous reports, the “knee” of the energy spectrum does not appear sharp, but rather a smooth transition over energies from 10¹⁵ eV to 3.0 × 10¹⁵ eV.     

Biochemical alterations in juvenile carp (Cyprinus carpio) exposed to zinc: glutathione reductase as a target

The aim of this study was to investigate biochemical changes in juvenile carp (Cyprinus carpio) exposed to zinc chloride (10, 30 and 100 microM) for a period of 48 h. Zinc exposure caused a concentration-dependent reduction in glutathione reductase (GR) activity in gills, liver and brain. Gill glutathione S-transferase (GST) was reduced when animals were exposed to the highest concentration of 100 microM zinc. The phosphorylation of p38(MAPK) increased in the brain of fish exposed to zinc 100 microM, while phosphorylation of the extracellular signal-regulated protein kinase 1/2 (ERK1/2) and c-Jun N-terminal protein kinase 1/2 (JNK1/2) remained unchanged. Expression of proteins HSP60 and HSP70 were not affected by zinc exposure. Considering the significant concentration-dependent inhibition of GR in all tissues analyzed, this enzyme could be a potential biomarker of exposure to zinc, which has to be confirmed.     

The Venus ionosphere at grazing incidence of solar radiation: Transport of plasma to the night ionosphere

Using a quasi-two-dimensional model of the Venus ionosphere, we calculated the ion number densities and horizontal ion bulk velocities expected for a range of solar zenith angles near the terminator (80 to 100°), and compared them with data obtained from the Pioneer Venus Orbiter retarding potential analyzer. The calculated ion bulk velocity arises entirely from the solar EUV-induced plasma pressure gradient and has a magnitude consistent with observations; ionization by suprathermal electrons is neglected in those computations. We find that while photoionization is the dominant source of ionospheric plasma for solar zenith angles less than 92°, plasma transport from the dayside is the dominant plasma source for solar zenith angles greater than 95°. We also show that the main nightside plasma peak at approximately 140 km altitude is of the F₂ type (i.e., is diffusion controlled). Its altitude and shape are thus quite insensitive to the altitude of the ion source.     

Estimation of bioavailability of polycyclic aromatic hydrocarbons in river sediments

This study aimed to evaluate the total concentration of polycyclic aromatic hydrocarbons in sediments of Iguassu River in Southern Brazil. Alongside the concentration, the amount of such compounds bioavailable was also evaluated. This is accomplished by comparing its total amount present in sediments and the amount extracted by n-butanol. The results showed that the total concentration of polycyclic aromatic hydrocarbons presented in sediment ranged from 4.49 to 58.75???g/g. The total amount of polycyclic aromatic hydrocarbons extracted by n-butanol ranged from 1.22 to 17.07???g/g. The use of n-butanol represents the mimetic conditions that hydrocarbons, derived from oil, could be taken up by organisms. Most of the hydrocarbons extracted by n-butanol were those with lower octanol?Cwater partition constant, usually those with three and four rings. Compounds with more than four rings were extracted in lower or insignificant amounts. Even the hydrocarbons with lower molecular weight available may be degraded or eliminated by organisms, when accumulated. Estimating bioavailability of hydrocarbons represents what specific hydrocarbons could be available to be taken up by organisms.