Search

Total Phosphorus Content in the Waters of the Arabian Sea along the West coast of India

Observations on oil slicks, tar residues and dissolved petroleum hydrocarbons (DPH) shortly after the oil spill resulting from the tanker accident in January 1993 showed negligible impact on the Indian EEZ of the Great Channel (Andaman Sea). DPH were between 0.31 and 1.85 μg l −1 in the area examined. Tar residues were absent throughout the study area. Prevailing NE wind with resultant SW surface current appears to have pushed the oil patches out towards the open Indian Ocean. A follow-up survey of the same area was carried out in September-October 1993 and observations similar to those made during the earlier survey were recorded. The zooplankton biomass had increased considerably during the interval between the two surveys, but this was probably due to seasonal changes and natural variability. The spill did not cause any perceptible impact on the environment.

A new method for the production of a continuously variable high contrast spatial frequency pattern is described. It uses two-beam interference of a laser through a wedge lens. Such patterns are useful for the evaluation of resolving power and Modulation Transfer Function (MTF) of photographic recording materials.

The Raman spectra in the lattice region (0–400 cm−1) of single crystals of NaNH4SO4·2H2O in various orientations are reported for the temperature range 293–87 K. NaNH4SO4·2H2O undergoes a transition at 101 K from a paraelectric phase to a ferroelectric phase. The changes in the Raman spectra as the crystal is cooled support the evidence from magnetic resonance studies that a large lattice distortion occurs at the transition temperature.

The Raman spectra of single crystals of NaNH4SeO4·2H2O in various orientations are reported for the temperature range 293–89 K. NaNH4SeO4·2H2O undergoes a transition at 180 K from a paraelectric phase to a ferroelectric phase. The changes in the Raman spectra as the crystal is cooled support the evidence from magnetic resonance studies that the transition is of a displacive type with an associated overdamped soft mode. Ordering of the NH ions but not of the complete crystal occurs at the transition temperature.

The Raman spectra in the region 250–1000 cm−1 are reported for six orientations of a single crystal of K2SeO4 over the temperature range 293–87 K. In the spectra of the paraelectric phase at 293 K, splitting of the internal vibrations of the SeO ion is in accord with the predictions of group theory. No significant differences are found in this internal frequency region in the ferroelectric phase at 87K. It is concluded that only minor lattice distortions are occurring at the ferroelectric phase transition which may be associated with a soft mode in the 22 cm−1 region.

The Raman spectra in the region 400–4000 cm−1 of single crystals of NaNH4SO4·2H2O in various orientations are reported for the temperature range 293–87K. NaNH4SO4·2H2O undergoes a transition at 101 K from a paraelectric phase to a ferroelectric phase. The changes in the Raman spectra of the constituent species, NH, SO and H2O as the temperature is lowered indicate that below the phase transition there are non-equivalent ions in the unit cell. The abruptness of the spectral changes at 101 K suggests a large lattice distortion in accord with the predictions of magnetic resonance studies.

The nutrient distribution of the Cochin Backwater was studied at 6 stations throughout the year. The depth profiles of phosphorus (inorganic and organic), nitrogen (nitrate and nitrite) and silicon, showed a marked seasonal rhythm, induced by the local precipitation and land runoff. Changes in other environmental features such as temperature, salinity, dissolved oxygen, pH and alkalinity were small during the premonsoon period when the system remains marine-dominated, and large during the monsoon period when the estuary becomes freshwater-dominated. Seasonal changes in the hydrographical conditions of the adjoining coastal waters of the Arabian Sea which influence the backwater system have been discussed.

The concentration of particulate organic carbon in the vicinity of Kavaratti Atoll is much greater than that of the surrounding sea. The particulate organic matter, which is largely produced by the coral reef, amounts to about 20% of the total gross production of tho reef community. It is suggested that, in the absence of an adequate standing crop of phytoplankton, the particulate matter may form an important source of energy to zooplankton in coral reef waters.

Changes during one year in the fauna of two beaches in south India are described in relation to the nutrient content of the water and sand, and the physical changes brought about by the south-west monsoon. At both beaches, the most stable conditions were reached in the pre-monsoon months when the greatest number of species occurred and when there was marked zonation. During the monsoon, erosion took place and only actively migrating species remained to form a permanent element of the beach fauna. Data on population density and biomass indicate markedly seasonal recruitment and rapid growth of individual species, most of which are suspension feeders.

The Raman and infrared absorption spectra of (NH4)2 SeO4, (ND4)2 SeO4 and Li (NH4) SeO4 have been recorded at 300° K; while the spectra of the non-deuterated compounds have been recorded at 110° K also. (NH4)2 Se04 crystal exhibits 33 Raman lines, while LiNH4SaO4 shows 30 Raman lines at 300° K. Proper assignments have been given to the observed vibration frequencies. The SeO4 −− ions and the (NH4)+ ions are found to be highly distorted in these selenates. There is lowering of the N-H vibration frequencies due to hydrogen bonding. The present spectroscopic investigations do not reveal the existence of any phase transition in these selenates in the temperature region investigated.

Organic detritus of the Cochin Backwater (India) is largely composed of fine silt and sand particles around which organic matter adheres and forms aggregates. In addition to plankton, large quantities of benthic algae, rooted plants, animal matter, suspended soft mud and the material brought down by the rivers and land runoff constitute the main sources of detritus. Detritus sedimentation in the estuary attains its maximum from April to June. Detritus forms a major portion of seston, while phytoplankton productivity constitutes 0.1 to 1.0% of settled detritus. Detrital pigments include degraded chlorophyll (phaeophytin), which has a marked seasonal variation; detrital carbon, phosphorus and nitrogen show little change during the year. The caloric value of detritus, calculated from protein, carbohydrate and lipid fractions and also from total carbon, indicates that sedimented detritus does not have a high nutritional value. However, being a readily available material, its entry into the food chain seems to increase the efficiency of energy transfer from one trophic level to another.

The Raman and infrared absorption spectra of sodium ammonium selenate dihydrate (SASD) have been recorded both above and below the ferroelectric transition temperature. The deuterated SASD has also been investigated. The results support the view that while there is only one type of NH4 + ions in the para electric phase, there are two types of NH4 + ions below Tc . The water molecules undergo considerable change and non-equivalent O-H bonds are produced below Tc . The SeO2/4− ions undergo very little change.