Table 5.

Average concentrations of selected elements, average shale (ppm) (Turekian and Wedepohl,1961), enrichment factor and the geoaccumulation index values in the clay samples

Elements	Average Shale Value	Ado Ekiti	EF	Igeo	Ara-Ijero Ekiti	EF	Igeo	Ire Ekiti	EF	Igeo	Isan Ekiti	EF	Igeo	Orin Ekiti	EF	Igeo
Cu	45	100.6	1.00	0.58	107.6	1.01	0.67	91.6	0.99	0.44	143.2	0.92	1.09	82.6	1.09	0.29
Zn	95	161	0.76	0.18	184.2	0.82	0.37	202.4	1.03	0.51	257.2	0.79	0.85	166.4	1.04	0.22
Ni	68	136.8	0.90	0.42	151.8	0.95	0.57	180.4	1.29	0.82	133.2	0.57	0.39	147.2	1.29	0.53
Mn	850	1593	0.84	0.32	1869.4	0.93	0.55	1682.8	0.96	0.40	3780.6	1.29	1.57	1451.4	1.02	0.19
Pb	20	232.2	5.20	2.95	199.8	4.23	2.74	174.4	4.23	2.54	247.2	3.59	3.04	150.6	4.48	2.33
As	13	160	5.51	3.04	-	-	-	-	-	-	23	0.51	-	-	-	-