Po Concentration Research Articles

Environmental factors affecting the seasonal changes of net plankton in two tropical fish ponds in India

Estimates of population size and biomass of net plankton were made in two tropical fish ponds in relation to the ecological data over a period of one year. There was a wide spatial and seasonal variation of population size and biomass of net plankton in two ponds studied. Always predominant over zooplankton, phytoplankton demonstrated three distinct annual peaks in the pond N-1 while a single peak was obtained in the pond N-2. A variable result was found in two ponds in the values of Shannon index of general diversity for phyto- and zooplankton. The seasonal changes of phytoplankton number in these ponds showed an inverse characteristic either with absolute concentration or with the rate of concentration changes of bicarbonate in the water, while the former and concentration of dissolved oxygen was positively correlated. In the multiple correlation analysis, the greatest importance of the concentration of PO4 was indicated on the phytoplankton population as HCO 3 − and dissolved oxygen were not considered to be included in the final regression formula in both the ponds studied but the rate of changes of HCO 3 − , PO4 and dissolved oxygen were influential on phytoplankton in the pond N-1.

Effect of physical and culture conditions on uptake of cadmium by <I>Chlorella pyrenoidosa</I>

<P>The effects of pH, temperature, concentrations of Cd<sup>2+</sup> and P<sub>4</sub><sup>3-</sup>, and density of algal suspension on the uptake of cadmium by <I>C.pyrenoidosa</I> were studied. Uptake occurred in at least two phases: fast (8 min) and slow (24 h). The slow uptake was dependent on pH (greater at pH 8.0 than 6.5) and temperature (faster at 25 than 4ºC) whereas the fast uptake was not. Both phases of uptake were affected by the density of the algal suspension. Dependence on the concentration of Cd<sup>2+</sup>, at pH 8.0, was limited by the concentration of PO<sub>4</sub><sup>3-</sup> and also possibly by the concentration of CO<sub>3</sub><sup>-2</sup>. Results were generally consistent with the model of initial ion-exchange uptake onto the cell wall and much slower transport across the cell membrane.</P>

Simulation of PO 4;P balance in a shallow and polluted river

A sophisticated and one-dimensional model to simulate the concentration of PO 4;P (x,i) in a shallow and polluted river is presented; the model incorporates, other than the convection and dispersion, various physico-chemical and biochemical reactions of phosphorus sinks and sources. With reference to the field data on Tama-gawa, which penetrates through the metropolitan area of Tokyo, the model is confirmed to represent the concentration of PO 4;P fairly well in the mid-region except for the mountainous origin and its estuary. A material balance of PO 4;P, the calculation of which is made possible from the model, reveals that about 15% of the daily phosphorus input into the region is fixed by algae on the river bottom, while about 54% of the input flows downstream without being fixed. The balance also discloses that phosphorus decrease due to adsorption on to suspended solid and the increase attributable to hydrolysis of condensed phosphates in the water can be disregarded, respectively. The rest of PO 4P balance amounting to about 30% is composed of adsorption on to the river-bed, seepage into the groundwater and release from the non-viable algal decomposition. The model is also used to simulate the PO 4;P concentration in the region under various conditions. Though naive, the most effective means to decrease the concentration is found, from the model, to be to curtail as much as possible the phosphorus inflow from tributaries.

A molecular mechanism for biological calcification

A general mechanism for calcification in biological systems is outlined which consists of organization of macromolecules and simultaneous or subsequent binding of alkali cations (principally Ca 2+) by the molecules to create compartments with higher pH values than the bulk phase of the solution. The higher pH value in this microcompartment would raise the concentration of PO 4 3− and OH − to an extent sufficient to induce their precipitation with Ca 2+.

Plant uptake of 210Po from soil

A study of plants grown in 210PoO 2 contaminated soil indicated definite uptake through the root system. The Po concentration in the tissues varied with plant species and decreased with period of growth. Transfer coefficients ( 210Po per g dry plant/ 210Po Per g dry soil) were calculated and ranged from 3 × 10 −2 to 3 × 10 −6 for the plants grown in 210PoO 2 contaminated soil. Comparison of the natural concentrations of 210Po in plants with the data for those grown in contaminated soil confirmed that natural fallout of radon daughters is the primary source of natural 210Po in plants.

Microbiological Leaching of Metallic Sulfides

The percentage of chalcopyrite leached in percolators by Thiobacillus ferrooxidans was dependent on the surface area of the ore but not on the amount. Typical examples of ore leaching, which demonstrate the role of the bacteria, are presented. In stationary fermentations, changes in KH(2)PO(4) concentration above or below 0.1% decreased copper leaching as did reduction in the MgSO(4).7H(2)O and increase in the (NH(4))(2)SO(4) concentration. Bacterial leaching of chalcopyrite was more effective than nonbiological leaching with ferric sulfate; ferric sulfate appeared to retard biological leaching, but this effect was likely caused by formation of an insoluble copper-iron complex. Ferrous sulfate and sodium chloride singly accentuated both bacterial and nonbiological leaching of chalcocite but jointly depressed bacterial action. Sodium chloride appeared to block bacterial iron oxidation without interfering with sulfide oxidation. Bacterial leaching of millerite, bornite, and chalcocite was greatest at pH 2.5. The economics of leaching a number of British Columbia ore bodies was discussed.

THE RÔLE OF PHOSPHATE IN BIOLOGICAL OXIDATIONS

1. The effect of phosphate on the oxidation of glyceric aldehyde by methylene blue, 1-naphthol 2-sulfonate indophenol, and phenol-indophenol has been studied. 2. At pH 4.77 in a phthalate-buffered medium phosphate does not catalyze the reaction. 3. At pH 7.9 in solutions buffered with borate, carbonate, or phenylalanine marked catalysis by phosphate is observed. The effect is most pronounced in borate. 4. Phosphate catalysis, within the limits studied, is strictly a linear function of the phosphate concentration. 5. The high concentration of HPO(4) (=) and the low concentration of PO(4) ( identical with) relative to that of the substrate virtually demand the conclusion that the PO(4) ( identical with) ion is the active catalytic species.