Removal of heavy metals from waters by means of natural zeolites

The natural zeolite clinoptilolite can be used as an ion exchanger for the removal of ammonium ions from drinking waters. These waters may also contain small amounts of heavy metals. The retention possibilities of these cations by the zeolite are presented.

The study of the selectivity of the Na-exchanged clinoptilolite in presence of ammonium ions has been achieved by plotting the exchange isotherms relative to the various cations. This leads to the following order of decreasing efficiency of the zeolite.     

Traffic pollution and roadside plants

Estimates of the levels of atmospheric pollution may be made by recording the presence or absence of common sensitive indicator species. The results of a simple survey might extend the range of plant material thought to be suitable for use in an urban area. Research by the author suggests however that some of the sensitive indicator species used seem to respond not only to sulphur dioxide but to proximity to busy roads, and there may be implications not only in the use of airpollution indicator species near roads, but in terms of roadside environmental conditions in general.     

Aeration as a tool to improve water quality and reduce the growth of hydrilla

Aeration of artificial, model lake systems was studied as a tool to improve water quality and to control the growth of a nuisance aquatic weed, Hydrilla verticillata (L.F.) Royle, which has been recognized as a plant pest since the mid-1960s. Aeration decreased the growth of Hydrilla by 20% fresh weight and 18% dry weight on average after 21 days. The effect was due to the oxygenation of the water and not the mechanical effect of the bubbles, as verified by studies using pure nitrogen. Aeration also affected water quality. Inorganic carbon decreased; nitrate-nitrite-nitrogen decreased, more slowly in test systems than in control systems; dissolved oxygen increased to saturation within 24 h and pH increased 0.5–1.5 unit over the period of study. Phosphate-phosphorus concentration was unaffected. The concentrations of zinc, calcium and iron decreased as well. The effect of aeration upon Hydrilla growth appears to be correlated with a decrease of iron. After 7 days, iron concentrations decreased to less than 20 ppb. Iron toxicity is proposed as the mechanism responsible for creating a limiting condition for Hydrilla growth.     

Reviews

LAND INTO LANDSCAPE by John M. Hunter, George Godwin/Longmans, 1985, 182 pp, £25.00

EATON ESTATE: LANDSCAPE CONSERVATION PLAN: Abridged Version of the Landscape Consultants' Report by Ian Laurie et al, Department of Town and Country Planning: University of Manchester, 1983.

DISCOVERING THE VERNACULAR LANDSCAPE by John B. Jackson, 165 pages, Yale University Press, 1984, $16.50.

THE ECOLOGICAL IMPACTS OF OUTDOOR RECREATION ON MOUNTAIN AREAS IN EUROPE AND NORTH AMERICA edited by N. G. Bayfield and G. C. Barrow. Published by Recreation Ecology Research Group 1985, Report No. 9.     

Predicting Dissolved-Oxygen Variations Downstream From An Intermittent Discharge

Intermittent discharges from unsatisfactory overflows and storm-sewage tanks to a watercourse can lead to depleted dissolved-oxygen concentrations downstream from the discharge point.
This paper assesses the accuracy and applicability of a simplified dynamic river-impact model which predicts BOD and dissolved-oxygen concentrations downstream from an intermittent discharge. The proposed model (a) requires relatively little input data, (b) is internally simple, and (c) uses well-known and established predictive equations. Concentrations of dissolved oxygen are predicted to within a mean error of 0.1 mg/l during post-storm conditions and 0.5 mg/l during actual storm conditions.     

Pharmacokinetics of dolasetron after oral and intravenous administration of dolasetron mesylate in healthy volunteers and patients with hepatic dysfunction

In previous studies, dolasetron was shown to have both renal and hepatic elimination mechanisms. This study was conducted to determine the impact of varying degrees of hepatic dysfunction on the pharmacokinetics and safety of dolasetron and its reduced metabolites. Seventeen adults were studied: six healthy volunteers (group I), seven patients with mild hepatic impairment (Child-Pugh class A; group II), and four patients with moderate to severe hepatic impairment (Child-Pugh class B or C1; group III). Single 150-mg doses of dolasetron mesylate were administered intravenously and orally, with a 7-day washout period separating treatments. After intravenous administration, no differences were observed between healthy volunteers and patients with hepatic impairment in maximum plasma concentration (Cmax), areas under the plasma concentration-time curve (AUC), or elimination half-life (t1/2) of intact dolasetron. No significant differences were found in Cmax, AUC, or apparent clearance (C(lapp)) of hydrodolasetron, the primary metabolite of dolasetron. The mean t1/2 increased from 6.87 hours in group I to 11.69 hours in group III. After oral administration, C(lapp) of hydrodolasetron decreased by 42%, and Cmax increased by 18% in patients with moderate to severe hepatic impairment. There were less changes in patients with mildly hepatic impairment. Total percentage of dose excreted as metabolites was similar for healthy volunteers and patients with hepatic impairment, although urinary metabolite profiles differed slightly. Dolasetron was well tolerated and there were no apparent differences in adverse effects between groups or treatments. Because hepatic impairment did not influence Cl(app) of hydrodolasetron after intravenous administration, and the range of plasma concentrations of hydrodolasetron after oral administration was not different from those observed in healthy volunteers, dosage adjustments are not recommended for patients with hepatic disease and normal renal function.     

Orbital pseudotumor: case report and overview

BACKGROUND: The most common cause of a sudden onset of painful proptosis with diplopia in an otherwise healthy adult is orbital pseudotumor. However, there are other conditions that mimic this presentation and must be ruled out with laboratory testing and imaging studies. CASE REPORT: A 41-year-old Hawaiian man sought treatment for an acute, progressive, painful, left ophthalmoplegia without exophthalmos. During the next week, a loss of accommodation and associated pupillary reaction, decreased visual acuity, color vision deficits, and a paracentral scotoma developed. CT and MRI revealed a mass in the orbital apex. All systemic findings were negative, and high-dose systemic steroid therapy was initiated. Symptoms resolved within hours of the first dose, and signs were completely absent 1 month later. Follow-up MRI revealed complete absence of the previously noted mass. CONCLUSION: This is an atypical case of orbital pseudotumor, since there was no exophthalmos. It was diagnosed by clinical presentation, laboratory and imaging studies, and response to therapy.