Residence times of groundwater along a flow path in the Great Artesian Basin determined by 81Kr, 36Cl and 4He: Implications for palaeo hydrogeology.

Understanding the age distribution of groundwater can provide information on both the recharge history as well as the geochemical evolution of groundwater flow systems. Of the few candidates available that can be used to date old groundwater, 81Kr shows the most promise because its input function is constant through time and there are less sources and sinks to complicate the dating procedure in comparison to traditional tracers such as 36Cl and 4He. In this paper we use 81Kr in a large groundwater basin to obtain a better understanding of the residence time distribution of an unconfined-confined aquifer system. A suite of environmental tracers along a groundwater flow path in the south-west Great Artesian Basin of Australia have been sampled. All age tracers (85Kr, 39Ar 14C, 81Kr, 36Cl and 4He) display a consistent increase in groundwater age with distance from the recharge area indicating the presence of a connected flow path. Assuming that 81Kr is the most accurate dating technique the 36Cl/Cl systematics was unravelled to reveal information on recharge mechanism and chloride concentration at the time of recharge. Current-day recharge occurs via ephemeral river recharge beneath the Finke River, while diffuse recharge is minor in the young groundwaters. Towards the end of the transect the influence of ephemeral recharge is less while diffuse recharge and the initial chloride concentration at recharge were higher.

Ultra-trace analysis of 36Cl by accelerator mass spectrometry: an interlaboratory study.

A first international (36)Cl interlaboratory comparison has been initiated. Evaluation of the final results of the eight participating accelerator mass spectrometry (AMS) laboratories on three synthetic AgCl samples with (36)Cl/Cl ratios at the 10(-11), 10(-12), and 10(-13) level shows no difference in the sense of simple statistical significance. However, more detailed statistical analyses demonstrate certain interlaboratory bias and underestimation of uncertainties by some laboratories. Following subsequent remeasurement and reanalysis of the data from some AMS facilities, the round-robin data indicate that (36)Cl/Cl data from two individual AMS laboratories can differ by up to 17%. Thus, the demand for further work on harmonising the (36)Cl-system on a worldwide scale and enlarging the improvement of measurements is obvious.

[Anesthetic management of a patient with dermatomyositis--clinical observation of the effect of muscle relaxants].

A 58 year old woman suffering from dermatomyositis underwent elective surgery for spinal caries. Concerning the anesthetic management of patient suffering from dermatomyositis, there is little information on the appropriate use of muscle relaxants. It is generally suspected that the patient is sensitive to nondepolarizing muscle relaxants. Anesthesia was with oxygen-nitrous oxide and fentanyl. Pancuronium 6 mg was given intravenously after awake intubation and an additional dose of 2 mg was given after 7.3 hours. During anesthesia neuromuscular function was monitored by neuromuscular transmission monitor (Datex Relaxograph). Duration of neuromuscular block was defined as the time for the twitch height to recover from total paralysis to 25% of the control value. Duration in this patient was 3.1 hours and this was longer as compared with the values of 1.1-1.8 hours obtained in 7 control patients. It is suggested that a usual dose of muscle relaxants results in a relatively higher effect in the patients with dermatomyositis because of their diminished muscle mass. The anesthetist should be careful in using muscle relaxants. The muscle relaxants should be given to such a patient with monitoring closely the neuromuscular function using a neuromuscular transmission monitor.