Fractionation of organo-mineral complexes by sedimentation and density techniques

Soil samples were fractionated by sedimentation in water and by flotation in heavy liquids to separate complexed and uncomplexed organic and inorganic components. Flocculation of clays in heavy organic liquids was delayed by addition of a surfactant. Heavy liquids and surfactants sorbed by soil components were removed by washing with acetone-water mixtures.In a sample of a red-brown earth, the organic carbon and nitrogen contents were highest in the finest separates. In samples of a ground-water rendzina and a chernozemic soil, the coarse clay and silt separates had the highest organic carbon and nitrogen contents. Organic matter was concentrated in low density fractions in all separates. Carbon/nitrogen ratios were lowest in the finer and heavier separates. Calcium, and to a lesser extent manganese, iron and phosphorus, were concentrated in low density fractions: thus these elements appear to be associated with organic matter and may be important in organo-mineral complex formation. Carbonates, titanium, iron, silicon and potassium were concentrated at the highest densities.Organic fractions < 2.06 g cm^?3 from sand size separates were insoluble in alkali and had wide carbon/nitrogen ratios characteristic of plant debris. The light fractions from fine silt and coarse clay separates were more soluble in alkali but showed high ratios of humic to fulvic materials and high absorption at 280 nm. Such materials were considered to be microbial cell debris and were associated with high contents of disordered aluminium and iron oxides and expanding lattice silicates in 1 to 5 μm aggregates.Heavier fractions, particularly of finer clay separates, contained more fulvic and humic materials of a more aliphatic nature than those in < 2.06 g cm^?3 fractions. It is suggested that physical sorption on clay surfaces may be more important in these fractions. Ellite and kaolinite were concentrated in medium density fractions, and contents of some iron oxides and titanium minerals were highest in fractions > 2.06 g cm^?3. Such minerals plus quartz and feldspars were associated with minor amounts of organic matter or possibly were not involved in organo-mineral associations.     

Aquatic turtles of Amazonia: An endangered resource

Turtles have long served man as an important food resource in Amazonia. During the colonial period, Portuguese traders disturbed nesting beaches on a large scale in search of eggs which were converted into oil for cooking and lighting. Exploitation was increasingly intense by the end of the 19th century and turtle populations had declined drastically. Although legislation has been passed to protect them, enforcement is lax and turtles face increasing pressure from man not only for food but as a result of habitat disturbance.     

The Prince Edward Islands: A sanctuary for seabirds in the Southern Ocean

This paper reviews the breeding distribution and numerical status of selected species of seabirds at 23 oceanic island groups in the Southern Ocean (between latitudes 35 and 70°S), based on census data and population estimates which have become available through increased scientific endeavour in the region during the last 15 years or so. The paper focuses on the avifauna of the Prince Edward islands, in the southern Indian Ocean, and points to the importance of these islands as a breeding station and sanctuary for seabirds. Only one oceanic island group, the Crozets, contains more species of breeding seabirds than the Prince Edward islands. Substantial segements (about 10% and greater) of the world breeding populations of the king and macaroni penguins, and the wandering, grey-headed, yellow-nosed and sooty albatrosses are based at the Prince Edward group. We recommend that Prince Edward Island (sensu stricto) should be a wilderness area, and that development at Marion Island should be kept to an absolute minimum.     

Analysis of fat-soluble vitamins. XXIII. High performance liquid chromatographic assay for vitamin D in vitamin D3 and multivitamin preparations.

Vitamin D is determined in preparations containing other fat-soluble vitamins by high performance liquid chromatography (HPLC). The unsaponifiable residue is extracted and separated from interferences by reverse phase chromatography; the fraction corresponding to vitamin D3 is collected and quantitated using normal phase chromatography (amylalcohol-n-hexane as mobile phase) by measuring the vitamin D3 and pre-vitamin D3 peaks at 254 nm. Previtamin D3 content is calculated as vitamin D3 with a conversion factor (determined on the equipment used). Application of the method to vitamin AD3 mixtures in oils gives 98-102% recovery. The reproducibility, using an external standard, is 2-3%, calculated as the coefficient of variation; with an internal standard, the coefficient of variation is 1-1.5%. The method measures potential vitamin D3 content in preparations containing greater than or equal to 200 IU/g in the presence of all known vitamin D3 isomers, vitamin A, and vitamin E.     

Instability of PR toxin in blue cheese.

PR toxin was unstable in solvent extracts of blue cheese and in strongly acidic solutions. However, it was appreciably stable over a 2.5 hr period in moderately acidic methanol-water extracts (pH 2--3) of blue cheese. Using this extraction mixture, it was determined that PR toxin was not stable in blue cheese itself. PR toxin reacted with model neutral and basic amino acids and the formation of PR imine from PR toxin in the presence of blue cheese was demonstrated. While PR imine added to blue cheese could be recovered on analysis after 5 min, over a 2--5 day period it too was unstable in the cheese.     

Gas-liquid chromatographic/mass spectrometric screening method for T-2 toxin in milk

A method for the analysis of T-2 toxin in milk is presented. Ethyl acetate extracts of milk samples which had been spiked with T-2 toxin were purified by thin layer chromatography and derivatized with N,O-bis(trimethylsilyl)acetamide to produce the T-2 toxin trimethylsilyl ether (T-2 toxin-TMS). N,O-bis(trimethylsilyl-d9)acetamide was used to make T-2 toxin d9-trimethylsilyl ether (T-2 toxin-d9 TMS) which was added to the derivatized milk extract as an internal standard. Samples were analyzed by combined gas-liquid chromatography/mass spectrometry using either electron impact ionization or chemical ionization mass spectrometry. In electron impact ionization analyses, simultaneous monitoring of the T-2 toxin-TMS fragment ion at m/z 436 and the T-2 toxin-d9TMS fragment ion at m/z 445 gave a T-2 toxin-TMS detectability estimated at 6 microgram/kg. In chemical ionization analyses, the T-2 toxin-TMS fragment ion at m/z 377 and the T-2 toxin-d9TMS fragment ion at m/z 386 were simultaneously monitored to give a T-2 toxin-TMS detectability estimated at 3 microgram/kg. Average recovery was 85% at 200 microgram/kg and 65% at 20 microgram/kg.     

Effect of strains of Rhizobium trifolii on the establishment of oversown white clover (Trifolium repens)

Strains of Rhizobium trifolii incorporated into commercial peat inoculants were compared for their effect on the establishment and growth of oversown white clover (Trifolium repens) on soils devoid of infective rhizobia.There were marked differences in numbers of seedlings establishing and clover dry matter production per hectare with the various strains. However, when adjusted to a constant number of established seedlings, dry matter production from all strains, apart from one strain at one site, were similar indicating that the strains did not appear to influence the growth of individual clover plants.The marked differences in establishment of clover inoculated with the various strains could not be accounted for by differences in the number of rhizobia in the peat inoculant.Selecting strains of rhizobia for ability to increase establishment is considered important where clover is oversown onto soils devoid of rhizobia.     

A comparison of continuous grazing systems for milk production

In two experiments conducted with Ayrshire dairy cows in 1974 and 1975 on swards of S23 perennial ryegrass, four systems of continuous grazing were investigated. The leys received 345 and 370 kg ha^-1 fertilizer nitrogen in 1974 and 1975 respectively and were stocked at the rate of five cows per ha. In 1974, a comparison was made between two systems which either integrated silage making with, or separated it from, the continuous grazing. The provision of a silage aftermath in late July increased milk yield after that time, but had no significant effect on milk yield over the 19-week experimental period. In 1975, a comparison between weekly and monthly applications of fertilizer N showed no significant differences between milk yields in a 20-week period. The feeding of supplementary concentrates from late July onwards significantly increased milk yield. The treatments in both years had only small and mainly non-significant effects on milk composition. On average, excluding the concentrate treatment, the annual output of milk was 10,800 kg ha^-1 using spring-calved cows.