Seasonality and interaction of biogenic and lithogenic particulate flux at the panama basin

Time-series sediment traps were deployed for an entire year at three depths (890, 2590, and 3560 meters) at a deepwater station (3860 meters) in the Panama Basin. The amount of horizontal and lithogenic particulate material arriving at the three depths was seasonally pulsed and directly reflected changes in surface primary production. Two spikes of organic flux were simultaneously recorded at all three depths: (i) a period of high productivity during regional upwelling in February through March and (ii) an unusual bloom of a single species of coccolithophorid during June through July. This latter spike delivered approximately 25 grams of coccolith per square meter of area at a depth of 3860 meters during less than 60 days. The flux of lithogenic particles increased with increasing depth and was seasonally correlated to surface production and current direction, and not to the detritus discharged in river flow. The data suggest that suspended clays are efficiently scavenged from the water column by rapidly sinking organic aggregates.     

Deep advective transport of lithogenic particles in panama basin

Sediment traps were deployed at several depths between 660 and 3800 meters in the Panama Basin. The flux of lithogenic particles increased with increasing depth. This increase was due primarily to particles of beidellite (a smectite clay), which was identical to the clay occurring in bottom sediment on the continental slope to the west of the sediment trap mooring. The beidellite vertical flux at the Panama Basin station increased when an easterly current prevailed and decreased when the current reversed, indicating that a major portion of smectite was transported horizontally at mid-water depth to the mooring site from the nearby continental slope.     

ROS-generating mitochondrial DNA mutations can regulate tumor cell metastasis

Mutations in mitochondrial DNA (mtDNA) occur at high frequency in human tumors, but whether these mutations alter tumor cell behavior has been unclear. We used cytoplasmic hybrid (cybrid) technology to replace the endogenous mtDNA in a mouse tumor cell line that was poorly metastatic with mtDNA from a cell line that was highly metastatic, and vice versa. Using assays of metastasis in mice, we found that the recipient tumor cells acquired the metastatic potential of the transferred mtDNA. The mtDNA conferring high metastatic potential contained G13997A and 13885insC mutations in the gene encoding NADH (reduced form of nicotinamide adenine dinucleotide) dehydrogenase subunit 6 (ND6). These mutations produced a deficiency in respiratory complex I activity and were associated with overproduction of reactive oxygen species (ROS). Pretreatment of the highly metastatic tumor cells with ROS scavengers suppressed their metastatic potential in mice. These results indicate that mtDNA mutations can contribute to tumor progression by enhancing the metastatic potential of tumor cells.     

Measurement of radioactivity in contaminated crops (Part 1)

It is a prerequisite to settle down how to subtract the counts based on natural radio-potassium in crops, finding out an accurate and efficient method. Considerable effort has been made so far with the investigations which have been conducted In various parts of Japan in accordance with this purpose. The writers wish to present a tentative method for measuring the radioactivity, reporting on the results obtained in comparison of this method with here-to-fore methods.     

Susceptibility of humic acid towards sodium amalgam

Three humic acids (HA-I) of different degrees of humification were treated with HCl (1:1). The hydrolyzed humic acids (HA-II) were subsequently degraded with Na-amalgam. The reduction products were divided into the following fractions: humic acid residues (HA-III), fulvic acid (FA), and ether-extractable lubstances (Et),

The humic acids used in this study were extracted from the following three soils; Inogashira (Volcanic ash soil), Kuragari (Drown forest soil, B_D type), and Higashiyama (Brown forest soil, rB_B type).

The experimental results are summarized as follows:

1. The RF values of HA-II, in the case of Inogashira and Kuragari, were higher, and the △log K values were lower than those of HA-I. The carbon and oxygen contents of HA-II were higher while the hydrogen, and nitrogen contents were lower than those of HA-I.

2. The total amount of carbon in HA-III. FA and Et added up to about 90% of the carbon present in HA-II. The carbon of HA-III found in HA-III after reduction tended to increase in the order: Inogashira>Kuragari>Higashiyama. In FA and Et, the opposite trend was followed.

In the case of Inogashira about 60% of the carbon of HA-II was found in HA-III.

3. The dark coloration of humic acid largely disappeared during the reductive treatment. As for the amorphous carbon-like structure detected in Inogashira, it was not found in the HA-III after reduction.

Therefore, it was presumed that the structures destroyed or saturated during the reductive treatment were the ones responsible for the essential properties of humic acid.     

Mechanisms and processes of crust formation on artificial aggregates

Crust formation process initiates from aggregate disinategration occurred through the combined effects of inherent soil properties and external actions. Rainfall plays a major role in determining the moisture conditions of the soil surface and in triggering aggregate disintegration mainly through slaking and the impact off raindrops. To analyze the relations between rainfall characteristics and crust formation, three artificially granulated aggregates were exposed to natural rainfall events. The rainfall characteristics were expressed in terms of the distribution pattern of rainfall intensity, I _10min; mean weighted drop diameters, D _n; raindrop concentration, N _Dn,; rainfall energy, Et;and kinetic energy, KE; as well as conventionally used parameters, such as total amount and mean intensity of rainfall. The degree of crusting was evaluated in terms of the water permeability and morphological observation just after the rainfall treatment. Based on a comparison of the rainfall characteristics and degree of crusting, we confirmed the following relations. Rainfall characteristics at the onset of the event considerably influence the degree of crusting, i.e. initial rainfall with high I _10min; and large drop size promotes aggregate disintegration by slaking due to rapid wetting, whereas initial gentle rainfall prevents slaking by slow wetting and subsequent crusting. When initial rainfall is not saaficient for slaking but Beads to a weakening sf the aggregates, subsequent disintegration and crusting are promoted by impact together with the residual influence of slaking. Impact is a dominant factor for aggregate disintegration under wet conditions after initial rainfall which is so gentle that slaking never occurs. Responses of the soils under different natural rainfall conditions were almost consistent with the results under simulated rainfall reported in the previous papers (Tanaka et $1.1997: Soil Sci. Plant Nutr., 43, 99-107, 109-115). Crusting was not observed in the Fujino 1–3 soil gender any rainfall events. In the Wokuei 1–3 soil, characterized by a susceptibility to slaking and stability to impact, crusting was only formed under the rainfall with high I _{10 min} at the onset. For the Shimazu 1 soil, impact played a dominant role in crusting under any rainfall events, and a larger degree of crusting was found when the effects of impact and slaking were combined. The characteristics of rainfall monitored in this study may be within a normal range as natural rainfall in terms of the amount and the mean intensity, suggesting that crusting likely to occur if the aggregate stability of soils is Bower than or similar to that sf the Shimaza 1 and the Hokuei 1–3 soils.     

Contents of heavy metal elements in copper mosses: Scopelophila ligulata,Scopelophila cataractae,and Mielichhoferia japonica and their substrates

Scopelophila ligulata (Spruce) Spruce, S. cataractae (Mitt.) Broth., and Mielichhoferia japonica Besch. (Mielichhoferia mielichhoferi (Hook.) Wijk et Marg. var. japonica (Besch.) Wijk et Marg.) are well known “copper mossess” which show peculiar ecological characteristics consisting of a preference for metal-rich soils, lithosols, rocks, etc. as their substrates. The total and water-soluble element contents in the substrates and heavy metal contents in the moss body were analyzed in this study. The results of these chemical analyses were as follows: The iron contents in the moss body and substrate of S. ligulata were higher than those of S. cataractae and M. japonica. On the contrary the copper contents of the former were lower than those of the latter. The pH values of substrate of S. ligulata were lower than those of S. cataractae and M. japonica. The concentrations of water-soluble iron and sulfate in the substrate of S. ligulata were higher than those of S. cataractae and M. japonica. On the contrary, the water-soluble copper concentrations in the substrate of S. ligulata were lower than those of the others. Although in the substrate of S. cataractae the iron content was several times higher than the copper content, in the moss body the copper content was higher than iron content.     

Estimation of microbial biomass potassium in paddy field soil

Abstract

Potassium (K) in microbial cells, microbial biomass K, in soil has been recently recognized as a K pool for plant growth. We determined soil microbial biomass K in paddy fields to reveal its importance as a K pool in paddy field soil for the first time. Microbial biomass K ranged from 5 to 21 mg K kg^?1 in the soil samples periodically collected from a paddy field and the value corresponded to 41% of the exchangeable K on average. Both microbial biomass K and exchangeable K increased conspicuously due to the long-term application of livestock manure compost or rice straw compost. Biomass K was higher than exchangeable K under K-deficient conditions in the long-term experimental plots without K application. The present study revealed that the microbial biomass contained considerable amounts of K in paddy field soil, indicating the need for evaluation of the microbial biomass K as a source and a stock of K in soil that has been overlooked.