Sinking particles were analyzed for their nitrogen isotopic ratio δ15N) of total particulate nitrogen (PN), stable carbon isotopic ratio (δ13C) and radioactive isotopic ratio (δ14C) of total particulate organic carbon (POC), at three different latitudinal (temperate, subpolar and equatorial) and geomorphological (trench, proximal abyssal plain and distal abyssal plain) sites in the western North Pacific Ocean using year-long time series sediment trap systems, to clarify the common vertical trends of the isotopic signals in deep water columns. Although the δ15N and δ13C values of sinking particulate organic matter (POM) were partly affected by the resuspension of sedimentary POM from the sea floor, especially in the trench, the changes in δ15N and δ13C values owing to the resuspension could be corrected by calculation of the isotopic mass balance from δ14C of sinking POC. After this correction, common downward decreasing trends in δ15N and δ13C values were obtained in the deep water columns, irrespective of the latitudes and depths. These coincidental isotopic signals between δ15N and δ13C values provide new constraints for the decomposition process of sinking POM, such as the preferential degradation of 15N- and 13C-rich compounds and the successive re-formation of the sinking particles by higher trophic level organisms in the deep water column. 相似文献
An automated titration for the Winkler method is presented for measuring primary productivity in the ocean. The system is based on a microcomputer-controlled titration with potentiometric endpoint detection. By the use of 0.005-N sodium thiosulfate as a titrant and a program designed to shorten the time for measuring, the method achieves a precision of 0.04% coefficient of variation with a range of 0.01 to 0.10% for six replicates of samples at oxygen concentration of 70 to 250 M. It takes about four to five minutes to measure one sample. 相似文献
Recognition of sequence boundaries and transgressive surfaces (i.e. ravinement surfaces, RS) is now known to be of great importance in stratigraphy. The sedimentary features of deposits immediately above a transgressive surface are well exposed in the Upper Pleistocene Kioroshi Formation of the Kanto Plain in central Japan. The formation comprises mainly coastal and shallow-marine deposits (estuarine, barrier-island and the strand-plain systems) which accumulated along a wavedominated coast in the Late Pleistocene, i.e., the last interglacial to last glacial period. The Kioroshi Formation is bounded above and below by sequence boundaries that formed in the lowstand periods correlative to the glacial periods of oxygen isotope stages 4 and 6, respectively. A significant transgressive surface that was formed by landward migration of barrier islands during the transgressive interval, the ravinement surface (RS), is found within the deposits of the upper shelf environment.
This ravinement surface is characterized by the exotic nature of the overlying sediment veneer (pebbles, shells and scattered mud clasts) which is poorly sorted. The RS shows a very flattened erosional surface in the shore-parallel sense, and the gradient of the surface in shore-normal sense is calculated as 0.0021, where the syndepositional tectonic movement is revised. The RS commonly cuts through the lower sequence boundary. However, in the places where the river or tidal channel valleys incised, the valley-filling sediment shows a deepening-upward sequence recognized as a transgressive systems tract and the RS can be clearly distinguished from the lower sequence boundary. 相似文献
Resource recycling reduces the amount of waste discharged into the global environment. The waste reduction achieved by thorough recycling is substantial. Recycling is thus an inseparable part of global environmental protection.We human beings have used mineral resources since the birth of our species. The quantities and increasingly complex forms in which mineral resources have been used at different times in our prehistory and history serve as indices of civilization's advancement. But on the eve of the 21st century, environmental pollution and global warming stemming from spiraling resource and energy consumption pose serious dilemmas for humanity. The rapidity with which our resource consumption has increased approximates exponential growth.The worsening condition of the earth's environment because of massive resource and energy consumption is the result of activity at many stages of production, from the mining of mineral resources to the manufacture of finished products; the culmination of the process is the disposal of products as waste after their use. As we shall see from examples given in this paper, efforts are being made to solve this problem through recycling; but in many areas the problems remain incompletely solved or unsolved altogether. 相似文献
Bottom sediments from the central zone of the Sea of Okhotsk were preliminarily dated. The petromagnetic parameters of two groups of samples formed at cold and warm climatic stages were studied. Warm oxygen isotopic stages and substages were characterized by the coexistence of pseudo-single-domain allogenic magnetite and predominant magnetite and greigite (pyrrhotite) grains subject to biologic control. At cold stages, sediments containing a mixture of pseudo-single-domain and multidomain terrigenous magnetite particles accumulated. The petromagnetic curves agree with the normalized standard oxygen isotopic curve over the last 350 kyr of the column section. 相似文献
A suite of surface sediment samples from three Icelandic lakes was analysed for subfossil chironomid head capsules, and a
quantitative July air temperature inference model was applied to the data to investigate whether there was significant variability
among samples taken from a lake. Ordination and simple regression methods were used to analyse the relationships between environmental
and sedimentological variables and the chironomid assemblages and inferred temperature data. Substrate was the most important
influence on the chironomid assemblages and inferred temperatures, while water depth at the sampling location had no relationship
with the chironomid-inferred temperatures. Within-lake variability of the chironomid assemblages and their inferred temperatures,
however, were not significant statistically, suggesting that in lakes of western and northwest Iceland within-lake sampling
location has no effect on the data obtained, and therefore on training set samples. 相似文献