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Activity of lactate dehydrogenase (LDH) was used as an effect criterion in toxicity tests with Daphnia magna. In the first part of the work, the conditions for the use of LDH activity in toxicity tests with juveniles and adults of D. magna, were optimized. The influence of parameters such as the number of animals per sample, nutritional status, age and the presence of eggs in the brood chamber were investigated. In the second part of the study, both in vivo and in vitro tests based on the alteration of LDH activity of D. magna were developed and tested using zinc chloride as test substance. The results obtained indicate that LDH activity of D. magna may be used as an indicative parameter in aquatic toxicity tests.

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T his paper summarises the results obtained in the MICAT (Mapa Ibero-Americano de E. ALMEIDACorrosa ˜o Atmosfe ´rica (L atin American Map of Atmospheric Corrosion)) atmospheric M. MORCILLOcorrosion project (an Iberoamerican project on atmospheric corrosion, involving 14 count- B. ROSALESries and 75 atmospheric test sites) for zinc specimens exposed in the L atin American region for 1-4 years at 23 pure marine and 19 mixed marine (i.e. SO 2 polluted) sites. T he atmospheres at these sites were characterised climatologically and in terms of their pollution levels so that their corrosivity could be expressed in accordance with ISO standards. Morphological and chemical characterisation of the zinc corrosion product layers (ZCPL s) was performed using scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS), X-ray diVraction (XRD), Fourier transform infrared spectroscopy (FT IR), and soluble salt evaluation techniques. T he results obtained show that the corrosion rate of zinc is a function of both the chloride pollution level and the time of wetness. Some synergetic eVects of Cl− and SO 2 were demonstrated, although some special types of behaviour were also observed.

As a result of a widespread application in numerous industrial processes, chromium is a contaminant of many environmental systems. Chromium and their compounds are toxic to both invertebrates and vertebrates and, for this reason, there has been a search for suitable and less toxic alternatives. Molybdenum compounds have been studied as alternative to chromium compounds for some industrial applications. The toxicity of chromium is well known but the effects of molybdenum and molybdenum mining on natural populations and communities of freshwater invertebrates have not often been studied. However, chromium, and molybdenum (and their compounds) are included in the same list (List II) of European Union dangerous substances. In this study, the acute and chronic effects of sodium molybdate and sodium dichromate to Daphnia magna Straus were evaluated. Furthermore, in vitro and in vivo effects of these two metals on acetylcholinesterase (AChE) activity of D. magna Straus were investigated. LC(50) values determined at 48 h were 0.29 and 2847.5 mg L(-1) for chromium (as sodium dichromate) and molybdenum (as sodium molybdate), respectively. No significant in vitro effects of both metals on AChE were found. However, both toxicants inhibited AChE in vivo at concentrations under the respective 48-h LC(50) values. Both sodium dichromate and sodium molybdate inhibited the reproduction and growth of D. magna, but the concentrations inducing significant effects were different for the two chemicals. Sodium molybdate had significant lower toxicity to D. magna Straus than sodium dichromate.

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This paper presents the results obtained at 3 Antarctic test sites participating in the "Ibero-American Map of Atmospheric Corrosiveness" (MICAT), a project on atmospheric corrosion carried out during the period 1988-1994 at some 70 sites distributed across 12 countries of the Latin-American region, Spain and Portugal. The three Antarctic sites are located near the coastline. The singular climatic characteristics of Antarctic regions are related with the purity of the air, the absence of rainfall and the formation of ice on the metallic surface during an important part of the exposure time. However electrochemical activity is possible below ice layers. This situation affects the structure and morphology of corrosion product films and the resulting corrosion rates of metallic surfaces.