Environmental Risk Assessment of Heavy Metal Concentrations in Road Runoff with Absorption Atomic Spectrophotometer(AAS) , Imo State, Nigeria.

Abstract

The study focused on the environmental risk evaluation of heavy metals in road runoff as non-point source   in the selected Routes in Owerri using Absorption Atomic Spectrophotometer. The major roads selected include Aba Road (RRSP1),  Orji Road (RRSP2),  Orlu Road (RRSP3),  Onitsha Road (RRSP4),  Wetheral Road (RRSP 5),  Okigwe Road (RRSP6),   and Port- Harcourt Road (RRSP) respectively. A total of twenty one runoff samples, three each from the seven selected roads were collected across three months (April-July, 2012), and analyzed using the M-Atomic Absorption Spectrophotometer (AAS). Results  shown that heavy metal concentrations originating from the  non-point source (NPS)  in  the six selected routes were in the following ranges: Cd(0.02 – 0.04 µg/l^-1), Cu (10.00-45.00 µg/l^-1), Cr(0.01-7.00 µg/l^-1), Zn(15.00 – 103.00 µg/l^-1), and Pb (12.00 – 79 µg/l^-1), which further explained  that concentrations were higher in the months of  April and May  in Aba road and reduced in other routes. An increased in heavy metals were observed during the month of July than the month of May.  Statistically, mean variations were observed  among heavy metals from road runoff that ranged between : Cd 0.07 µg/l^-1, Cr 3.10 µg/l^-1, Cu 22.70 µg/l^-1, Pb 36.70 µg/l^-1 and Zn 51. 40 µg/l^-1in order of Zn >Pb>Cu> Cr>Cd respectively. The results also indicated that Cd, Cu, Cr, Zn  and Pb concentrations in road runoff sampled were    above the  FMENV and WHO standards for potable water  during the  month of April being first flush, May being the after first flush and July that proceeds August break that affects man and his environment.

Keywords: Environmental Risk , Road runoff, Atomic Absorption Spectrophotometer, Heavy Metals, Nigeria.