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

Assessment of the Pollution Status of Eleyele Lake, Ibadan, Oyo State, Nigeria

Background. Lakes are a vital water resource, but are adversely affected by pollutants such as heavy metals and polychlorinated biphenyls (PCBs) from urban, agricultural and industrial activities. This can give rise to potential pollution-related health problems such as cancer and infectious diseases. Risk assessments are necessary to determine the degree of pollution and its effects on human health and ecological systems. Objectives. This study assessed the pollution status and a risk assessment was calculated to determine the degree of the pollution and its effects on the human health and the ecological system of Eleyele Lake in Ibadan, Nigeria. Methods. Physical and chemical parameters, heavy metals and PCBs were determined in the lake water using standard methods from December 2013 to February 2014 at ten different sites of anthropogenic activity. Results. Water pH ranged from 6.00–7.50, while electrical conductivity ranged from 205.00–221.00 μs/cm3. Dissolved oxygen ranged from 0.30–6.00 mg/L and total dissolved solids ranged from 105.00–113.00 mg/L. Phosphate levels ranged from 13–0.99 mg/L. Nitrate and sulphate in the dry season ranged from (3.10–3.80 and 35.81–40.97 mg/L) and (0.12– 0.37 and 6.10–10.30 mg/L) in the wet season. Heavy metal concentrations were in the order cadmium (Cd) > zinc (Zn) > copper (Cu) > chromium (Cr) > lead (Pb) for the dry season and Cd > Zn > Cr > Pb > Cu for the wet season. Total PCBs ranged from 493.90–732.55 μg/L and 52.00–390.03 μg/L for the dry and wet seasons, respectively. All determined physical and chemical parameters were within permissible levels, while heavy metals and PCB concentrations were higher than permissible levels. Discussion. The hazard quotients and carcinogenic risk values were greater than acceptable limits, indicating that PCBs in Eleyele lake water pose adverse health effects to the local population. It was observed in this study that lower chlorinated PCBs were more prevalent than higher chlorinated PCBs. This may be attributed to the fact that the lower chlorinated PCBs are influenced by atmospheric deposition as a result of their volatility, and they are more susceptible to atmospheric transport than highly chlorinated PCBs. Conclusions. PCBs possess serious health risks to the population that depends on the lake as a source of domestic water and its aquatic organisms. Efforts are needed to reduce anthropogenic influence on the lake through strict environmental controls. Competing Interests. The authors declare no financial competing interests