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Abstract
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), 0.11–1.00 mg l−1 (Na+>Mg2+>K+), 1.01–10.00 mg l−1 (Ca
) and>10.01 mg l−1 (TS>TSS>TDS>HCO
SiO2>alkalinity>acidity>hardness). 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.