No abstract available

[en] Six techniques were evaluated for their suitability for the pretreatment of dried sewage sludge prior to trace metal analysis by atomic absorption spectrophotometry. The evaluation comprised analysis of two prepared samples of dried sludge for aluminium, cadmium, chromium, copper, iron, lead, manganese, nickel and zinc, after the following pretreatment: dry ashing at 500 degrees Celsius followed by extraction with dilute hydrochloric acid; dry ashing at 500 degrees Celsius followed by extraction with aqua regia; nitric acid digestion followed by extraction with hydrochloric acid; extraction with aqua regia; ashing with magnesium nitrate solution at 550 degrees Celsius followed by digestion with hydrochloric acid and extraction with nitric acid; extraction with nitric acid. Procedures involving the use of perchloric acid, hydrofluoric acid and hydrogen peroxide were not considered for reasons of safety. Except in the case of aluminium the direct mineral acid digestion and/or extraction methods generally gave higher recoveries than the procedures incorporating an ashing step. Direct extraction of the sample with aqua regia was recommended as a rapid and simple general method of sample pretreatment prior to analysis for all the metals investigated except aluminium. For this metal, more drastic sample pretreatment will be required, for example fusion or hydrofluoric acid digestion

[en] Twenty eight groundwater samples form Beaufort group rocks were analysed for their dissolved He, Rn, Ra, CH₄, N₂, O₂, and Ar concentrations, and their ¹⁴C and ³H ages. Along the 120 km long sampling line large variations in He concentrations were measured, ranging over three orders of magnitude, and correlate with similarly large variatios in CH₄ concentrations. Higher He and CH₄ concentrations are characteristic of the older waters. However, unless the rocks are unusually radioactive or have very low porosities, the He concentrations appear to be too high for a system where the dissolved He was only that produced during the residence time of the water by the rock with which the water was in contact. The high He concentrations may be the result of He migration associated with CH₄ migration. The magnitude and uniformity of the Rn concentrations suggest that the Rn is of near-surface origin. N₂ and Ar concentrations are generally higher than those to be expected for waters originally in equilibrium with the atmosphere; excess air may be trapped in the waters during their initial infiltration

[en] The in vitro absorption of ₃₂P by the organs of intact and dissected plants of the submerged freshwater macrophyte, Potamogeton pectinatus L, was investigated. ₃₂P was absorbed by the roots, stems and leaves of intact and dissected plants under both light and dark conditions, and at both low and high phosphate concentrations. Absorption, translocation, and release of ₃₂P by this species were also investigated using compartmentalized containers separating foliage and roots. It was found that a higher P-concentration in the root compartment (simulating natural conditions) influences absorption, translocation and release of ₃₂P. An in situ study in Germiston Lake using ₃₂P confirmed that the roots of P. pectinatus can absorb phosphorus from the sediment followed by its translocation to the foliage

[en] The treatment of radioactive fission products ^{- 90}Sr2+, ⁶⁰Co2+ and ¹³⁷Cs+ - from simulated nuclear wastewater was evaluated using locally-isolated sulphate-reducing organisms. In this study, sulphate-reducing bacteria (SRB) were used as biosorbents for removal of the cationic fission products. The cultures achieved 90%, 100%, and 80% removal of Sr2+, Co2+ and Cs+, respectively, for a 75 mg×ℓ-1 solution of each metal under a low ionic strength of 0.01 M. Increasing the ionic strength of the solution to 0.5 M resulted in a decreased metal uptake to 80%, 65% and 70% for Sr2+, Co2+ and Cs+, respectively. Approximately 68% of the adsorbed fraction on cell surfaces was exchangeable (i.e., was desorbed under acidic conditions). Using surface complexation models and equilibrium modelling analysis, reaction sites on the cell walls of the cultures were determined to belong to the -COOH and -H₂PO₄ groups (pKa = 4-5 and 7-8, respectively). The distribution of the isoelectric equilibrium points for cell surfaces was consistent with the composition and characteristics of the identified microbial species in the culture which was dominated by the Gram(+ve) Bacilli - Lysinicibacillus boronitolerans AB199591 - and biofloc-forming Gram(-ve) SRBs, such as Desulfomonile tiedgei AF418162, Syntrophobacter wolinii X70905, and Desulforhopalus vacuolatus L42613. The high exchangeable fraction on the cells and the higher removal rates under lower ionic strength indicates that metal binding was non-electrostatic which was consistent with outer-sphere complexation behaviour. (author)

[en] Electron microscopy combined with the energy dispersive analysis of X-rays (EDX) has been used to examine the nature of the phosphorus accumulated in sludges from seven activated sludge plants exhibiting enhanced phosphorus removal. Large phosphorus accumulations were located in identical structures in the sludges examined. The phosphorus was located in large electron-dense bodies, within large bacterial cells which were characteristically grouped in clusters. The calcium:phosphorus ratio of these electron-dense bodies precluded them from being any form of calcium phosphate precipitate. Quantitative analysis indicated that the electron-dense bodies contained in excess of 30% phosphorus. The results obtained are supportive of a biological mechanism of enhanced phosphorus uptake in activated sludge

[en] The seasonal fluctuation in the phosphorus absorption, translocation, and release by the roots and shoots of Potamogeton pectinatus L. in Germiston Lake, is discussed. Shoot absorption exceeds that by the roots during spring and winter, while the reverse applies for summer and autumn. The shoots consistently release more phosphorus per plant than the roots. Both shoots and roots absorb considerably more phosphorus than what they release to the environment. This macrophyte, therefore, mainly acts as a phosphorus reservoir in Germiston Lake

[en] The concentration and distribution of nutrients (ammonia, nitrite, nitrate, phosphate and total phosphorus), faecal Escherichia coli I and heavy metals (copper, lead, zinc, iron, manganese, cobalt, nickel, cadmium, chromium and mercury) have been studied during a preliminary survey of the Papenkuils River undertaken in November 1980. Areas of pollutant input to the river have been identified from the results. These pollutants have caused extensive ecological modification in the river, which represents one of the more serious sources of pollutants in the coastal marine environment of the south-eastern Cape

[en] Water, surface sediment and sediment core samples were collected from sites in the Swartkops River up to 15 km from the mouth and analysed for up to sixteen elements. The results indicate the presence of four main areas of contamination in the river, at Redhouse, Swartkops, the brickworks and Amsterdam Hoek. The accumulation of zinc, copper, lead and nickel by oysters grown at the mouth of the river confirms the presence of greater than normal metal concentrations in the river. Fish-water Flats outfall contributes metals to the nearshore marine environment, but the strong tidal sweep disperses the effluent relatively quickly so that metal build-up in the area is minimal. In general, metal levels in the Swartkops River are low and, as yet, the area cannot be described as 'polluted' in the true sense of the word

[en] Chemical and meiofaunal studies have been carried out on ten sandy beaches along the south and west coasts of South Africa with the aim of establishing base line levels of some parameters, including trace metals, nutrients, dissolved oxygen, oxygen absorbed from alkaline permanganate (OA), temperature and salinity and the diversity and size of meiofaunal populations. Guidelines for the normal levels of the various parameters have been set out and some reasons for their variability have been suggested. The various sites share similarities with regard to exposure, granulometry and hydrology