The relationships of adjacent mounds of five widely distributed species of termites, at two sites south and southwest of Townsville in north Queensland have been examined. It has been shown that four of these species,Amitermes laurensis (Mjöberg),Tumulitermes pastinator (Hill),Drepanotermes rubriceps (Froggatt) andDrepanotermes perniger (Froggatt), are polycalic, with up to eight mounds comprising a single colony. A simple unequivocal method was used. A bait containing a radioactive tracer (131I) was introduced to a mound and the subsequent transfer of this bait to other mounds by termites was monitored with a scintillation detector. The existence of polycalic mounds among some Australian termite colonies alters the interpretation of mound distribution data. In particular, overdispersion of the mounds of some species cannot be interpreted as indicating intraspecific competition if the locations of polycalic mounds are unknown.

The use of the tracer dilution technique to gauge flow over broad shallow floodplains is examined. Because of the long mixing lengths, it sometimes takes several days for the passage of the laterally dispersed pulse. Tracer methods can be used if the flow rates vary linearly during the passage of the pulse. The measured flow rate is related to the time at which the first moment of the concentration profile (∫tc(z,t)dt) is zero. An experimental verification is presented.

A large part of Sydney Metropolitan sewage effluent after primary treatment is discharged into coastal waters from shoreline outfalls. It contains up to 70mg/1 grease and oil in the three distinct sewage fractions. Investigations to study the dispersal of grease and oil in coastal waters were initiated and carried out by the Metropolitan Water Sewerage and Drainage Board in conjunction with the firm of consultants, Crooks Michell Peacock Stewart Pty Limited, in collaboration with the Australian Atomic Energy Commission. Radioactive gold-198 was found to be an ideal label for the grease and oil. The areal and vertical dispersion of the ocean discharge sewage has been measured for two sewage fractions under a variety of weather conditions. These experiments have shown that a ten fold dilution of sewage effluent occurs within 100m of the ocean outfall and also that, except under violent wave action, the dispersing effluent is held as a surface trapped layer only 6m thick for at least 5km from the ocean outfall. It appears that the finely dispersed portion of the effluent grease mixes and disperses continuously with the ocean water. These investigations are providing a fuller understanding of the behaviour of sewage oil and grease discharged into coastal waters and should lead to a reduction in beach pollution.

The Australian Atomic Energy Commission has undertaken a number of studies using low level radioisotope techniques to assist in the assessment of waste disposal systems. The studies have varied, from the assessment of established systems where problems such as the beach deposition of ocean borne sewage effluent and the suitability of dumping sites for dredged spoil can be investigated, to the prediction of the impact of proposed systems where, for example, the effects of the discharge of waste water from mining operations into a flood plain system can be gauged.