Surface water quality status and chemical speciation of Qua Iboe River system, Niger-Delta, Nigeria

Introduction Over the past years, the Nigerian coastal environment which consists of rich and diverse ecosystems, natural resources and increased human population, has been subjected to erosion and different forms of anthropogenic pollution. The pollution of surface water bodies, especially with toxic trace metals, has attracted considerable public attention the past few decades (Suthar et al. 2009). The input of environmental pollutants into the aquatic systems is a common phenomenon in Nigeria (Abu and Egenonu 2008). Industrialization and urbanization is one of the main indices of national and global development, but sometimes, while it enhances the quality of life, it also poses serious threats to the management of the natural ecosystem and public health (Umoren and Udousoro 2009). Different sources of surface water pollution in the region include crude oil spills, refined oil pipeline leakages, solid wastes, garbage disposal, industrial wastes, municipal sewage, non-point pollutants runoff from agricultural farmlands, industrial effluents (heavy metals, phosphorus), urban runoff (oils, salts, various chemicals) and atmospheric fallouts of airborne pollution (Otokunefor and Obiukwu 2005; Rim-Rukeh et al. 2006; Abu and Egenonu 2008; Nduka et al. 2008; Umoren and Udousoro 2009). Typically, water quality criteria are defined based on the measurements of metal concentrations and the increasing release of heavy metals into the aquatic environment. This has posed serious threats to the environment and public health due to its accumulation and persistence in the food chain (Onianwa and Fakayode 2001). In order to assess possible effects on the biota, both the total trace element concentrations as well as their chemical speciation have to be determined, because of the increased toxicity and bioavailability of some metal species (Tepavitcharova et al. 2011). Speciation modeling uses a chemical analysis of water to calculate the distribution of aqueous species using an ionassociation aqueous model. The analysis of chemical species of trace metals in surface and ground water using the PHREEQC computer program allowed for the determination of the distribution of the metal species and the calculation of saturation indices to determine the saturation state of the water body with respect to different associated mineral phases (Parkhurst and Appelo 1999; Bhattacharya et al. 2006; Parello et al. 2008; Obiefuna and Orazulike 2010; Zhang et al. 2010; Tepavitcharova et al. 2010; Bouragba et al. 2011; Tepavitcharova et al. 2011). Normally, speciation modeling requires only a SOLUTION (or SOLUTION_SPREAD) data block for each water analysis for which saturation indices are to be calculated (Parkhurst and Apello 1999). Sequel to the recent interest in massive infrastructural and industrial development of the region by government, which tends to suggest an imminent environmental issues, there is therefore, need for continuous assessment of the pollution status of the region. This study, however, seeks to examine the water quality status of Qua Iboe River system, assess the distribution of solution species (speciation) and to calculate the saturation indices of selected mineral species using the PHREEQCI computer model. Results obtained will be used to predict the pollution status of the river for sustainable monitoring and management of the coastal waters in the area. Materials and Methods The study area and design The study area, Eket and Ibeno communities of the coastal South-eastern part of the Niger Delta region, Nigeria lies between latitude 4°40′ North and longitude 7°55′ East (Eket), and latitude 4°30′ North and longitude 8°00′ East (Ibeno). The Qua Iboe River is a confluence of rivers from different sources