Heavy Metal Concentrations in Urban Stormwater Runoff and Receiving Stream.

Stormwater and receiving stream water samples were collected along Abeokuta- Ibadan road at four different locations and analysed for heavy metals: copper, zinc, lead, cadmium, chromium  and other pollution indicating indices like DO, BOD5, COD, total dissolved solid, EC, pH, chloride, hardness, and alkalinity. The result of the analyses showed the mean concentration of heavy metals were:  0.66 mg/L (Pb), 0.83 mg/L (Zn), 1.93 mg/L (Cu), 0.51 mg/L (Cd) and 0.44 mg/L (Cr). Copper is the most prominent metal both in the stormwater and the receiving streams in the study area compared to others.  Average physico-chemical properties of stormwater such as pH w as 9.15±0.49, temperature, 26.27±0.51, EC, 276.00±48.86 uScm-1, hardness, 93.25±48.0 and alkalinity, 2.78±1.04 for the stream. Dissolved Oxygen (DO) in the stormwater ranges from 2.88 to 3.97 mg/L. Mean TDS, COD and BOD5 were 128.7 mg/L, 156.25 mg/L, and 47.06 mg/L respectively. None of these values exceeded the limit considered as potential hazard according to international standards. However, in the nearest future the pollution level may likely increase drastically exceed the recognised standards due to increasing urban activities, hence, there is the need to safeguard the health of the urban ecosystem by reducing stormwater pollution from sources and the development of sustainable urban stormwater management using best management practices (BMPs). Keywords: Highways; Pollution; Urbanisation; Stormwater; Stormwater Management

Mapping of Traffic-Related Air Pollution Using GIS Techniques in Ijebu-Ode, Nigeria

Spatial and temporal characteristics of traffic related air pollutants (CO, NO, NO2 and SO2) in Ijebu-ode, Nigeria were determined using replicate portable gas detectors (Land Duo Multi Gas Monitor) at selected road junctions, motor garages and markets. Mapping of different concentration of air pollutants was carried out using kriging type of interpolation method in GIS environment. Concentration of CO ranges from 4.8 ppm at Erinlu/Molipa Roundabout to 137ppm on Sagamu/Ore Expressway. Concentrations of NO2  range from 100-662 ppb with overall average value (OAV) of 299.8 ppb, while concentration of nitrogen oxide (NO) ranges between 67-302 ppb and OAV of 166.23 ppb. SO2 had concentration ranging between 38-245 ppb and an OAV of 139.07 ppb all of which are above standard ambient air quality standards. AQI indicated very unhealthy air quality in most areas which calls for the need to establish and strengthen the health-based standard for air pollutants