, Volume 37, Issue 2, pp 145-157

The nutrient input by Harmattan dust to a forest ecosystem in Côte d'Ivoire, Africa

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Abstract

During December and January, dry northeasterly surface winds (the Harmattan)distribute dust over West Africa. Rate of deposition and some chemical andphysical characteristics of Harmattan dust were measured in Taï NationalPark in the southwest corner of Côte d'Ivoire during the 1990–1991 dryseason. The dust deposition was estimated by the classical water-filled basinmethod and by using canopy drip to account for deposition on tree canopies.Contamination by local biotic debris in both, water-filled basin and canopydrip collectors, was corrected for by using Ti (which appears to be wholly ofatmospheric origin) as a reference element. Harmattan dust in Taï consistedmainly of kaolinitic silt finer than that collected in North Nigeria, closer tothe source area in the Chad basin. The estimates of seasonal deposition rateswere 33 to 47 kg ha-1 for the water-filled basin method andaround 80 kg ha-1 for the canopy drip method. The higher valuein canopy drip was in agreement with expected higher deposition of fine duston the canopies than on a water surface, and was therefore considered morereliable to estimate nutrient inputs by Harmattan dust deposition. The seasonalnutrient input by dust was thus estimated to be 0.11 kg ha-1for P, 2.5 kg ha-1 for K, 3.5 kg ha-1 for Caand 0.4 kg ha-1 for Mg.