Environmental Pollution (1970)最新文献

A procedure for observing the effects of dissolved copper and other metal ions on the submersed aquatic macrophyte Elodea canadensis has been described. Metal concentrations have been determined which inhibit light-induced oxygen evolution from plant segments after short-term exposure (24h), and which produce phytotoxicity in whole plants over a longer period (28 days). These results are discussed in terms of the phytotoxic effects on Elodea resulting from dissolved metal ions present in polluting concentrations in natural water bodies or from the use of added copper as an aquatic herbicide.

Eighty-five samples of leaves of Ricinus communis L. (Euphorbiaceae) representing five populations—four collected from healthy, and one from polluted, environments—were studied to establish the relationship between environmental pollution and foliar epidermal features. The data obtained were analysed statistically.

Stomatal frequency per square millimetre and the percentage of abnormal stomata (single guard cell or both the guard cells aborted) on both the upper and the lower epidermis showed a marked increase in plants growing ni polluted areas. One or two per cent of stomata on the lower epidermis also showed a slight decrease in size. A correlation between idioblast frequency and pollution was also observed.

Scanning electron microscopic studies of the foliar surface revealed that stomatal openings were larger and cuticular striations more conspicuous in leaves of polluted populations than in those of healthy ones.

Radioisotopes of cobalt (^57,58,60Co) are present in nuclear test debris as well as in effluents of the non-military nuclear industry. The stable isotope, which is a constituent of vitamin B₁₂, has very important biological functions.

For each species, three experiments were carried out: (1) starved animals were immersed in ⁶⁰Co-contaminated water; (2) animals were immersed in contaminated water and received radioactive food and (3) animals were placed in fresh water without any pollutant but received contaminated food. Radiation doses were calculated for contamination via both food and water.

When ⁶⁰Co is taken up directly from water, the most contaminated organs are external ones, especially the shell of the snail Lymnaea palustris and the exoskeleton and feeding appendages of the crayfish Astacus leptodactylus. Contamination via food is responsible for a relatively greater accumulation of radiocobalt in internal organs. The cobalt content of muscles—that is to say the edible parts of crayfish and common carp Cyprinus carpio—is very low. The highest concentrations recorded are in the visceral mass of the snail, the digestive gland of the crayfish and the kidneys of the carp.

Internal doses for these organs are considerably higher than those for entire animals. Therefore, as a result of ⁶⁰Co distribution, they are critical organs for the freshwater species. Except for the carp, external radiation is very weak compared with internal radiation.

A strong retention of ⁶⁰Co is observed for the shell of L. palustris while the desorption of radiocobalt from the exoskeleton of A. leptodactylus is easier. In carp, the ⁶⁰Co taken up by the gut from food, as well as from water, is rapidly eliminated.

On first mixing digested sewage sludge with soil the proportions of the Cu and Zn in the sludge that are extractable to conventional extractants fluctuate considerably. Thus Cu extractable from sludge alone shows a marked initia fall to a minimum at 8–29 days and then rises to near its initial value; from a sludge—soil mixture there is a less marked decrease (over 8–16 days) and the extractable Cu returns to near its initial value over 90–100 days. The Zn extractable from sludge alone falls to a minimum at 8–16 days and then rises to near the initial value, but the Zn extractable from sludge-soil mixtures rises sharply over 2–4 days and then falls to near the initial value over 50–100 days.

There appears to be little further change in the extractable Cu, Ni or Zn during the next 600 days, although the metals in the sludge are still relatively more extractable than those ‘native’ to the soil. It is likely that similar processes operate under field conditions, but more slowly.