Using bait lamina and litterbags, two functional methods to monitor biological activity in soil contaminated by dieldrin. Preliminary results from Dakar (Senegal) sahelian region

Abstract

The capability of bait lamina to assess biological activity of soil fauna in semi-arid zone was studied in a peri-urban area polluted by dieldrin. This method was compared to litter bags usually used in this savannah region to monitor the activity of soil macro-invertebrates. The study site is used for agriculture and the irrigation water contains known concentrations of dieldrin residues. Three plots were chosen: One plot was soaked with water containing 1.4 μg dieldrin/l; another with 1.96 μg dieldrin/l and a control without dieldrin. Analysis of dieldrin residue were done from water samples taken from wells used for watering. The feeding activity of soil macro-invertebrates monitored with bait lamina was significantly different between the two contaminated plots and the control, both in absolute numbers and in the vertical distribution. A similar trend had been observed between bait lamina and litter bags despite their differences such as study duration (10 days and 60 days, respectively). Soil dwelling organisms which attack bait lamina were not identified but further study could verify if termites, which are the main soil macro-fauna group in savannah, are responsible for these attacks.

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Keywords: Bait lamina, dieldrin, sahelian zone, biological activity, litter bags, ecotoxicology