Event mean concentrations of urban stormwater runoff quality from a small catchment in Nigeria

In this study, the event mean concentrations (EMC) of stormwater runoff from a medium cost residential area of Mubi, in Adamawa State Nigeria, were examined. A total of 79 samples were analyzed for pH, turbidity, total suspended solid (TSS), total dissolved solid (TDS), copper (Cu), iron (Fe) and zinc (Zn). The ranges of event mean concentrations (EMC) were 57.17 - 1004.22 mg/L for TSS, 283.74 - 3152.76 mg/L for TDS, 0.0292 - 0.3042 mg/L for Cu, 0.3530 - 7.5970 mg/L for Fe and 0.0189 - 0.1799 mg/L for Zn. These gives site mean concentration of 360.27 mg/L, 1049.14 mg/L, 0.1443 mg/L, 2.8066 mg/L and 0.0633 mg/L for TSS, TDS, Cu, Fe and Zn respectively. EMC for all constituents show large inter-event variation. Correlation analysis showed that no strong correlation between rainfall characteristics and the EMC values. However, the EMC of TDS has significant influence on EMC of Cu and Fe in the storm water runoff. Also, EMC of TSS has significant influence on EMC of Zn. All pollutants, show the occurrence of the first flush, indicating higher mass load delivery during the early part of storm events.