Samples of bulk free-fall and roof-intercepted rainwater over five different roof types (iron-zinc corrugated sheets, concrete slate tiles, Adex/asbestos cement sheets, aluminium sheets, and thatch) were collected and analysed using standard methods with adequate quality-control and quality-assurance measures. The mean values of some of the investigated parameters for the roof-intercepted samples occurred within four continuous sets of ranges, viz: <0.11 mg l −1 (NH + 4 ), 0.11-1.00 mg l −1 (Na. The other parameters were: pH (6.68-7.45), conductivity (19.4-122.6 µS cm −1 ), colour (25.9-257.6 Pt-Co), and turbidity (6.4-24.7 NTU). The corresponding mean values for the free-fall samples were either within the low end of the same range or about one order of magnitude less than that of the roof-intercepted samples. The enrichment factors of the roof-intercepted samples were within the range of 1.03-4.92 with an overall mean of 2.9 ± 0.3 standard error. Most of the water-quality parameters, including bacterial counts and the number of isolated species were higher both at the beginning and end of the rainy season (when both dry and wet depositions were high) than during the mid-season period (when only wet deposition was high). They also showed an increase with the age of roof materials, especially the samples over Adex and concrete slate roofs. The rainwater sources were not potable without necessary treatment but suitable for a wide range of other applications.

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The seasonal variations, spatial distribution and interrelationships of rotifers in Opa Reservoir, Nigeria were studied and the relationship between rotifer species and certain physico-chemical parameters of the water described. The population density of rotifers was maximal during the rainy season, mostly concentrated at the top of the water column. Rotifer communities in the riverine source station were different from the open lake communities and rotifer population density was poorest in the riverine section. Significant correlations were found between rotifers and several physico-chemical parameters of which oxygen was the most pronounced. Considerable affinity and close associations were also found to exist between rotifer species. RCsmCOn a Ctudie les variations saisonnieres, la distribution spatiale et les interrelations des rotiferes du reservoir Opa, au Nigeria, et on a decrit la relation entre des especes de rotiferes et certains parametres physico-chimiques de I'eau. La densite de population des rotiferes etait maximale pendant la saison des pluies, concentree surtout au-dessus de la colonne d'eau. Les communautes de rotiferes a la station proche de la source etaient diffkrentes de celles du lac proprement dit, et la densit6 des populations de rotiferes etait plus faible dans la section riveraine. On a trouvC des correlations significatives entre les rotiferes et plusieurs parametres physico-chimiques, surtout avec I'oxygene. On a aussi dkcouvert qu'il existe des affinitks considkrables et d'etroites associations entre les espkces de ro ti feres.

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