The concentration of ammonia in the atmosphere over the ocean was determined for samples collected on board. The concentration of total ammonia in the maritime air was 50ng at/m3(STP) on the average which was much lower than that over the land, and was higher in the air nearer the land. The proportion of aerosol ammonia to total ammonia in the maritime air was 30% (mean) in the North Pacific, whereas it was 80% in the South Pacific. These facts together with the residence time of ammonia in the atmosphere suggest that most of ammonia in the oceanic air is of continental origin. The amount of combined nitrogen transported from the land to the ocean is estimated from its concentration in rain water to be 1.5 × 1012g at N/y. Judging from the budget of the combined nitrogen in the ocean, the large supply of nitrogen from the land is balanced by the denitrification in the ocean. Its mechanism is discussed from the quantitative aspect, and two possibilities still remain owing to the lack of decisive evidences, which are the reduction of nitrate in sea water containing little oxygen and the denitrification in the respiratory process in oxygenated sea water.
The carbon-reduction technique for the oxygen isotopic analysis of sulphates has been further developed to improve its reliability for isotopic ratio measurements. Barium sulphate is reduced with carbon at 1, 000°C in a thin platinum boat as an electric resistance heating element to evolve carbon dioxide and carbon monoxide. The carbon monoxide is converted by a high-voltage (3.0kV) discharge between two parallel platinum plates in a liquid-nitrogen cooled vessel. The barium sulphate precipitated from the solution containing sulphate ions by the standard procedure can be reduced with a 98 ± 2% yield of oxygen as carbon dioxide, and analysed with the reproducibility of 0.1-0.25‰ for the oxygen isotopic ratio. No significant memory effect is observed in the analyses of barium sulphates having oxygen isotopic ratios in the range from -1 to +46‰ (SMOW).
Barite concretions from the Shinguri and other banks of the Japan Sea off the Northeast Honshu have sulfate extremely enriched in heavy sulfur and oxygen isotopes; the δ34S value relative to Canõn Diablo troilite ranges from +47.5 to +86.7‰ and the δ18O value relative to SMOW from +24 to +29‰. When δ34S values are plotted against δ18O values, most data closely fit a line having a slope of 4 (Fig.3). Although other possibilities can not be excluded, the isotopic and other geologic features strongly suggest that most plausible environments of their formation were isolated “sea water lakes” which possibly formed on the tops of these banks during the Quaternary glacier ages and where extensive bacterial reduction of sulfate took place. The barite concretions from New Zealand studied by RAFTER and MIZUTANI (1967) and a barite concretion from a bank off Baja, California are isotopically similar to those of the present study.
Techniques developed for high contrast optical examination and high resolution study of fossil tracks are described. We find that depositing a thin layer of silver (or gold) on the surfaces of trackholes greatly enhances optical contrast allowing accurate measurement of track lengths. This technique has been successfully employed to measure lengths of “complete” tracks using the TINT and TINCLE method. Such measurements are useful in a study of the chemical composition of cosmic radiation and fossil records of transuranic elements in lunar and meteoritic samples. Another application for silver (or gold) coating of track hole surfaces lies in the study of long tracks due to cosmic ray nuclei of Z>30; epoxy resin adheres firmly to the coated surface and the tracks can be sealed against further chemical attack. The plastic replication and Pd shadowing technique was developed and used to examine fossil tracks occurring with high track densities, >107cm-2, in gas rich meteorites and in lunar regolith samples. The method seems to be accurate up to densities of about 3 × 109 cm-2.