Related Experiment Video
Updated: Feb 1, 2026

Quantification of Heavy Metals and Other Inorganic Contaminants on the Productivity of Microalgae
Published on: July 10, 2015
Concentrations and Human Health Risk of Heavy Metals in Rivers in Southwest Nigeria
Ibukun Modupe Adesiyan1, Mary Bisi-Johnson2, Omolara Titilayo Aladesanmi1
1Institute of Ecology and Environmental Studies, Obafemi Awolowo University, Ile-Ife, Nigeria.
Background:
Rivers are the most vital freshwater resources in the world. In Southwest Nigeria, anthropogenic activity stresses the quantity and quality of water resources.
Methods:
The present study examined the concentrations and human health risk of five heavy metals (manganese (Mn), arsenic (As), chromium (Cr), cadmium (Cd), and lead (Pb)) in selected rivers in Southwest Nigeria. The determination of heavy metals was carried out by atomic absorption spectrophotometry after digestion with a di-acid mixture 9:4 (v/v) (nitric acid: perchloric acid).
Results:
All rivers had higher concentrations of the five heavy metals in the dry season except for As in Dandaru (0.012 mg/L) and Asejire (0.016 mg/L). Manganese was observed to have the highest mean concentration among all the five metals in both the rainy and dry seasons across the sampled rivers. Generally, the annual mean concentration of metals followed the order: Mn>Cr>Cd>Pb>As in all the selected rivers.
Discussion:
The human health risk assessment showed that the hazard index and hazard quotient for ingestion of water for Cd and As in all the sampled rivers were higher than the acceptable limit of 1.0, indicating carcinogenic risk (CR) via direct ingestion of water. The CR via ingestion for As in all of the sampled rivers was above the remedial goal target of 1×10-6. The recorded values for chronic daily intake (CDI) were higher for Cr and Mn in all four sampled rivers.
Conclusions:
The results of the present study showed that As is a driver for carcinogenic risk through ingestion in all of the sampled rivers compared to other metals.
Competing Interests:
The authors declare no competing financial interests.
Related Concept Videos
Bonding in Metals
Metallic Solids
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability....
Alkali Metals
Table 1: Properties of the alkali metals
Relative Risk
Metal-Ligand Bonds
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
Expressing Solution Concentration
Concentrations may be quantitatively assessed using a wide variety of measurement units, each convenient for particular applications. Molarity (M) is a useful concentration unit for many applications in chemistry.

