A PRELIMINARY STUDY ON ORGANIC MATERIAL, NITROGEN AND PHOSPHORUS IN THE DEEP-SEA SEDIMENTS OF THE PACIFIC WESTERN REGION

This paper deals with the distribution, controlling factors and geochemical characteristics of the organic material, nitrogen and phosphorus in the Pacific western region (2°-8°N, 170°-173° 20′E)by analysing the amount of the organic material, nitrogen and phosphorus of seven core samples and comparing the grain-size, miner-alogical and biological data of the sediments. The result shows that the average contents of organic material and nitrogen in the surface sediments are similar to those in the surface sediments in the Atlantic western part and the south of the Indian Ocean, but the content of phosphorus is double that in the south of the Indian Ocean. The plane distribution of organic material and nitrogen is just the same. The contents in the southeast are both higher than those in the northwest and increase with the amount of silicon increasing in the sediments. The contents of organic material and nitrogen have positive correlation with the depth of the water and negative correlation with the number of foraminifera in the sediments. The contents of organic material and nitrogen in the sediments are lower than those in the shallow area on the continental shelf. It is because the region is far from land and the sedimentation rate is very low. The sediments come mainly from the synthese of the chemical and biological reactions in sea water. It is suggested that the apatites [Ca₅(P0₂)³OH] added to the sediments during volcanic eruption serve as a reason why the content of phosphorus in the region is higher than that in the shallow water on the continental shelf and in the south of the Indian Ocean. The distribution of the contents of organic material and nitrogen is controlled mainly by the biological type and the amount of clay in the sediments. The amount of phosphorus is controlled mainly by minerals and subsequently by the biological type and the amount of clay in the sediments. The average value of C(org)/N in the surface sediments in the Pacific western region is 14. 98 with a range from 11. 21 to 30. 43. The C(org)/N ratio of the sediments in the region is higher than that in the Atlantic and the shallow area on the continental shelf. It is apparently caused by the following main factors : 1) the poor source of mineral;2)the lower sedimentation rate;and 3)the mineralization of some nitrogenous compounds in the surface sediments. However, the ratio of C(org)/N in the sediments from 0-100cm shows a slight change or no change in the some stations owing to the fact that the affect of bacterium in the deep-sea sediments has weakened or disappeared. There is a positive correlation between the organic material and nitrogen in the sediments. It can be expressed by the equation (Yn = 0.0592C-0.016, r = 0.966). It indicates that the nitrogen in the sediments exists mainly in forms of proteins, amino acids, etc. The correlation between nitrogen and phosphorus can be expressed by the equation: (Yn = 0.1036p + 0.0204, r = 0.500). It shows that the phosphorus exists in forms of inorganic compounds (for example, apatites [Ca₅(PO₂) ₃OH]) besides bio-organic compounds. The relationship between organic material, nitrogen and phosphorus and dioxide silicon and calcium carbonate in the sediments is influenced by the contents of dioxide silicon and calcium carbonate in the sedi ments. When the contents of dioxide silicon and calcium carbonate are about 45% and 5 % respectively and when the contents of dioxide silicon, calcium carbonate change slightly, the contents of organic material, nitrogen and phosphorus change apparently. When the contents of dioxide silicon and calcium carbonate lie between 15%-44%and 10%-60% respectively, the contents of organic material, nitrogen and phosphorus almost have no change. When the contents of dioxide silicon and calcium carbonate are in the ranges of 0-15% and 65%-85% respectively, C. N. P : CaCO₃ and C. X. P :SiO₂ are about 1 (- 1).