Isabelle Halleux

Toxicity monitoring of the Scheldt and Meuse rivers in Wallonia (Belgium) by conventional tests and microbiotests

The Mierotox«> acute toxieity test using the luminescent bacterium Vibrio fischeri, was chosen as a cornplementary deseriptive parameter of toxie pollution in the framework of monitoring surface water quality in Wallonia, Belgium. In order to examine the samples on a routine basis, ensure a cost-effective approach adapted to the dilution effects, and enhance the sensitivity of the system, a two-step strategy has been adopted and validated : a qualitative screening test, followed by a standard test for an the sampies indueing a light inhibition ~ 20%. For samples in whieh toxieity was detected, Microtox«> responses were compared with the results of a battery of tests ineluding conventional bioassays (algal growth inhibition, Daphnia magna acute test) and rnierobiotests (Rotoxkit FTM and Thamnotoxkit FTM). These additional bioassays generally eonfirmed the toxieity detected by the bacterial test, at least qualitatively. This battery of tests has also been used to eharacterise the toxieity of effiuents upstream of toxie points, and to identify the assays appropriate for studying the toxie plume. Ten % ofthe 1500 results from about 50 locations sampled every 4 weeks since 1994, appeared to be acutely toxie to Vibrio fischeri at different scales. Results can be negative, toxie or positive when showing a slight effect at high concentrations. The frequeney of toxie events ranged from occasional to permanent. Analysis of the results at each toxie point or on the whole data set showed that toxicologieal and chernical parameters are eomplementary. In view of the rapid evolution of Materials and methods in toxicity testing, a critical analysis is Made of the use of the acute bioassay with Vibrio fischeri for monitoring the quality of river waters and some new perspectives are presented.

Development of a database system for the management of borehole data: Experience and lessons

CBS-LOG is a multilingual database system for the management of coal exploratory borehole data. It is a dBase application running on PCs with minimum configurations. Developing a suitably accurate database requires some strategic choices and lots of discussions and compromises between experts. The experience shows that it is absolutely necessary to follow strictly the development flowsheet and that the difficulties rely mainly on communication and human aspects of mathematical geology. A step by step approach is reviewed in terms of experience and lessons.

Contribution of the quantitative interpretation of gamma-ray logs to the study of limestone exploitation, a case-study at Maizeret, Belgium

Abstract Economic considerations constrain quarrymen in Wallonia to consider more profit-earning exploitation of limestone deposits and (or) to diversify their products. Gamma-ray logs contain information about the geology, structure and quality of deposits. Quantitative interpretation of the logs is necessary in order to provide a reasonably good image of reality. The method proposed here consists in removing the effects of different parameters influencing the measurements (analog ratemeter, statistical noise, etc.) and in deconvolving the data in the frequency domain by the analytical impulse response function of the system. An example demonstrates that mathematical processing increases the lithologic and stratigraphic definition of the logs (bed boundaries, bed thicknesses) and offers a satisfactory characterization of the rocks along boreholes. Some of the quarrymens questions can be answered from this analysis.