Finding a relationship between physicochemical characteristics and ionic composition of River Nworie, Imo State, Nigeria

Abstract

Water has been described as a universal solvent, and this is perhaps the strength behind its many uses. Despite this unique property, anthropogenic activities along its course and natural factors often determine the composition of water. In the current research, the portion of River Nworie having past Owerri town was sampled in the dry season 2017 to determine its ionic composition at predestinated points and to relate such properties to its physicochemical characteristics. Studies relating physicochemical properties and dissolved toxic ions in water could develop a body of knowledge that could enable detection and quantification of potential risk of ions such as heavy metals from natural water to aquatic ecosystem, animal and human health without actually involving aquatic organism, animal and human. Clean sterile plastic bottles were used for collecting surface water. A total of 30 sub-samples from five points at 300 m apart were sampled in the morning. Physicochemical properties were determined using standard methods and ionic composition of water was determined according methods of APHA. Results revealed that Ca2+ had a mean 23.60 ± 0.67 mg/l and was the highest while K+ with a mean 0.72 ± 0.30 was the least amongst major cations. Amongst the major anions Cl− had mean of 31.58 ± 4.47 mg/l while mean of PO43− was 1.42 ± 0.13 mg/l. The ionic balance calculate as % balance error showed high values for all sampling sites ranging from 30 to 39.42% indicating that there is massive input from anthropogenic activities. The computed relationships for selected heavy metals, cations and anions revealed that R2 values were ranging between  ± 0.012 to 1 indicating some form of relationship existing. The water pH weakly correlated with dissolved cations and anions while moderate with pH only, due to the pH level (5.2–6.2). The cations and anions were more influenced by the water temperature than the heavy metals. Therefore, high temperature ranges of 31–32.4 °C will favour more dissolution of cations and anions in natural water. Cations showed stronger relationship with EC while only heavy metals showed no relationship with DO (Dissolved oxygen). Dissolved oxygen relationship with cations and anions was in the order; K+ > Mg2+ > Ca2+ > Na+ while anions was SO42− > NO3− > Cl− > PO43−, respectively. Information here could be used to predict the effects of using this water for various purposes including water for agricultural purposes, in the management of ion polluted waters, and also to inform on the mitigation process to be taken.