Towards Terrestrial Ecotoxicological Test Methods for the Tropics.
Christopher Martius, Center for Development Research (ZEF), Walter-Flex-Strasse 3, Bonn, Germany, Marcos V.B. Garcia, EMBRAPA Amaz˘nia Ocidental, Rod. AM-10, Km 28, Manaus, Brazil, and Joerg Roembke, ECT Oekotoxikologie GmbH, Boettgerstrasse 2-14, Floersheim, Germany.
Soil organisms play a crucial role in terrestrial ecosystems. Plant Protection Products (PPPs) are known to affect these organisms and might have negative impacts on soil functions influenced by these organisms. Little research has been done to day on the impact of PPPs on tropical ecosystems. Therefore, in a pilot investigation we studied whether the effects of pesticides differ between tropical and temperate regions and whether data generated under temperate conditions can be used for the Environmental Risk Assessment (ERA) in tropical regions. In the pilot tests, one fungicide (Carbendazim) and one insecticide (lambda-Cyhalothrin) were used as model organisms. Their effects on soil invertebrates (earthworms and arthropods) and functional parameters (organic matter (OM) breakdown, feeding rate) were evaluated in semi-field tests using Terrestrial Model Ecosystems (TMEs) and in field tests using litter-bags. The soil for the TMEs was extracted from the same site near Manaus (Amazonas, Brazil) where the field test was conducted. The soil was acid clay, typical for tropical regions. In the TMEs the standard test species as well as native tropical species were introduced. Several application scenarios, selected according to their relevance for practical conditions, were realized in TME-tests and field (duration: 150 and 365 days, respectively). Finally, an Environmental Risk Assessment (ERA) for the two chemicals was performed. The results from the TME-tests show that both test chemicals (depending on their concentration) had toxic effects on the tested organisms and organic matter breakdown, but not on the feeding rates. In the field organic matter breakdown was affected for some time too, but effects on single species were, with one exception (the native earthworm Andiorrhinus amazonicus) not observed; a result probably influenced by the small size of the test plots. Observed differences in OM breakdown between control and treated TMEs were often significant, while due to the higher variability even with differences >10% between means this was not the case in the field. According to the results of the Environmental Risk Assessment presented here, the use of the three model chemicals in the tropics (e.g. in Brazil) can cause damage to the soil. Therefore, a more detailed investigation of these PPPs is recommended, in particular a better evaluation of the exposure (residue analysis). In general, the work performed in Amazonia can be summarised as follows: (1) Depending on the properties of the PPP, the effects of pesticides in tropical and temperate regions can differ widely. (2) If a PPP is going to be used in the tropics, tests should be performed that have been modified to match the tropical environmental conditions, and their results should be incorporated in an Environmental Risk Assessment (ERA) for tropical regions.