Assessment of heavy metals in soils and groundwater in an urban watershed of Yaoundé (Cameroon-West Africa).

The aim of this study was to investigate the heavy metals concentrations in soils and groundwater within the Ntem watershed in Yaoundé, to prevent the risk on the public health. Soils investigated were sampled in five (05) representative profiles at the surface and the bottom of the unsaturated zone of each profile. Soil samples were air-dried and ground to pass through a 2-mm sieve, and different soil extracts were prepared for chemical analysis (organic matter, cation exchange capacity and pH).

Microphyte and macrophyte-based lagooning in tropical regions.

A 720 m2 plant made of 8 ponds in series, set in Yaounde (Cameroon), was successively operated as a macrophyte-based system (type M) from November 1997 to October 98, a microphyte-based system (type m) from October 1999 to September 2000 and a combination of macrophyte and microphyte ponds (type M + m) from May to July 2001. Average applied loads varied over the years; from 420 kg. BOD5 ha(-1)d(-1) on the year 1997/98, the loads reached 510 kg BOD5 ha(-1)d(-1) in 1999/2000 and 500 in 2001.