Environmental Pollution (1970)最新文献

The effect of Louisiana crude oil on growth of Spartina alterniflora Loisel and selected anaerobic soil processes in a Louisiana salt marsh was investigated. Greenhouse and field studies indicated that S. alterniflora can tolerate a large amount of oil without a short-term decrease in above-ground biomass. Neither the biological reduction of nitrate, manganese, iron and sulphate nor the production of methane and ammonium in stirred reduced sediments were affected by additions of up to 10% oil on a soil-weight basis. Oil placed on the water surface of unstirred sediment caused a release of iron, manganese and ammonium from the sediment to the overlying water due to the absence of oxygen in the water column.

The acute LD₅₀ value of DDT in adult summer frogs was only 7·6 mg/kg.The symptoms of poisoning caused by DDT point to nervous damage. The toxicity was further increased by starving. The retention of DDT was followed using (¹⁴C)-labelled DDT. It accumulated most in tissues containing fat. Thus the fat body and liver retained much of the DDT while only a very small amount was found in skeletal or heart muscle. In female frogs a large quantity of DDT is stored in the ovary, its large size and high fat content possibly accounting for this phenomenon. Moderate amounts of DDT were found in kidneys and nervous tissue. In addition, an autoradiographical study revealed considerable radioactivity in bones and spleen.

Starved animals retained higher amounts of DDT in their tissues, with the exception of the fat body, than did the fed animals. DDT was found to disappear extremely slowly. Its disappearance was, however, enhanced by previous DDT treatment since DDT-treated animals retained much less of the test dose than did the untreated controls. It is thus possible that DDT induces the activity of drug-metabolising enzymes which may lead to increased biliary excretion of the drug.

The potential radiological implications of environmental tritium releases must be determined in order to develop a programme for dealing with the tritium inventory predicted for the nuclear power industry which, though still in its infancy, produces tritium in megacurie quantities annually. Should the development of fusion power generation become a reality, it will create a potential source for large releases of tritium, much of it in the gaseous state. At present about 90% of the tritium produced enters the environment through gaseous and liquid effluents and is deposited in the hydrosphere as tritiated water. Tritium can be assimilated by plants and animals and organically bound, regardless of the exposure pathway. However, there appears to be no concentration factor relative to hydrogen at any level of food chains analysed to date. The body burden, for man, is dependent on the exposure pathway and tissue-bound fractions are primarily the result of organically bound tritium in food.

Four sludges, three of which contained Ca(OH)₂, FeCl₃ or Al₂(SO₄)₃ for phosphorus removal, were compared as to degradation in soil. All sludges degraded rapidly but rates <25 mg/g approached CO₂ evolution of untreated soil in 15 days while higher rates required about 50 days. Each of the sludges contained lime which, at each addition, increased the soil pH. The Ca-sludge produced the greatest pH increase and evolved larger amounts of CO₂ than the Fe- and Al-sludges. The Ca-sludge evolved 52%, the untreated Al-sludge 20% and the Fe-sludge 5% of the sludge C. Calcium carbonate added to the soil increased the degradation of the Al-sludge and no significant differences amongst sludges were noted in the percentage of sludge C evolved. The degradation of these sludges was more related to soil pH than to chemical treatment of the influent for phosphorus removal.

⁶⁰Co enters the environment with radioactive wastes from nuclear power reactors and fuel reprocessing plants as well as a component of fallout from nuclear tests.

A study of ⁶⁰Co in freshwater organisms has been carried out in order to compare the influence of different modes of uptake (immersion in contaminated water, ingestion of radioactive food, contamination by both food and water) upon the subsequent elimination.

The loss of ⁶⁰Co by Canadian pondweed Elodea canadensis is monophasic. For animal species, this phenomenon is biphasic, independently of the mode of uptake.

On the other hand, the biological half-life changes in relation to the vector of contamination. The same result is observed for the relative importance of the different compartments. This is easily explained because the mode of uptake determines the distribution of ⁶⁰Co in the organisms.

The turnover of ⁶⁰Co in the organisms is slow and the physical half-life of this radionuclide is relatively important (T_p = 5·27 years). Thus, the possible consequences of the release of this pollutant on freshwater life must not be neglected.