Nitrate and ammonium levels of some water bodies and their interaction with some selected properties of soils in Douala metropolis, Cameroon
The present study examined the nitrate (NO3-) and ammonium (NH4+) levels of Rivers Wouri and Dibamba and some streams that feed them. The interaction of NO3- and NH4+ with some soil properties was also investigated. It was necessitated by the usage of these rivers for livelihood, despite the deposition of discharges into these streams. Twenty eight (28) surface water and four soil samples were collected from various sites within the Douala metropolis. The water was analysed for pH, electrical conductivity (EC), NO3-, NH4+ while the soil was analysed for particle size and cation exchange capacity (CEC). In both cases, standard methods were used. The NO3- and NH4+ levels were higher than the WHO threshold levels in some sites. Nitrate and NH4+ levels of 341.6 and 632.8 mg/l, respectively, were observed in some sites in Dibamba River despite the high level of clay in this area. The values in the Wouri River were low, contrary to the low level of clay in this area. This trend was also reflected in the streams that feed both rivers. The NH4+/NO3- molar ratio was low in areas proxy to the industries reflecting industrial source of pollution. The continuous use of water from Rivers Wouri and Dibamba for domestic purposes is variably unsafe and needs attention.
Key words: Nitrate, ammonium, water bodies/quality, soils, Douala metropolis.