3.2.2. Ecological Risk Factor (ErF)

For ErF results of heavy metal concentrations in the River Kaduna, the level of pollution was in the order Cd > Co > Ni > Pb > Cr > Cu > Zn > Mn (Table 4). Compared to other heavy metals, Cd ErF revealed a high metal pollution level especially at site S5 (ErF = 2206.41). However, the values of ErF for Mn, Cu, Zn, Cr, Pb, Ni, and Co revealed low potential ecological risk or pollution. But in total, the multi-metal ErF as reflected for variation in sites classified the sediments into low pollution to very high pollution in the sequence S5 > S3 > S4 > S1 > S2. Sites S3, S4, and S5 were classified as having very high ecological risk with ErF ≥ 320, S2 as a low potential ecological risk with ErF <40, and S1 as a moderate potential ecological risk with ErF falling between 40–79.9.

**Table 4.** Enrichment factor (ErF) values of heavy metals in sediment samples from the River Kaduna.


Note: S = Site.
