SEGH Articles

Application of geochemical signatures of shale in environmental pollution and human health assessment in South East Nigeria

15 June 2011
Therese Ntonzi Nganje describes her experience through a Commonwealth Scholarship scheme on connecting Nigerian and UK scientists.

This work contained activities during the period of my Commonwealth Scholarship Commission Fellowship (NGCF-2009-154) tenable held at the University of the West of Scotland October 2009- April 2010 under the supervision of Professor Andrew Hursthouse.

Areas underlain by shale rock in some parts of south-eastern Nigeria were investigated to ascertain the degree of environmental pollution by potential toxic trace element and the possible impact on human health.   A control area underlain by sandstone was also investigated as a known naturally low potentially toxic trace element area. Shales, especially the black variety, are natural geological sources of potentially toxic trace elements such as As, Cd, U, Mo, Cu, Ni, Hg among others, which are known to influence human health. The aim of this work was to primarily assess the effect of shale on the quality of the environment (soil, edible crop plants and water), evaluate the exposure pathways of the toxic trace elements and their implications on the health of humans. Samples of food, soil and drinking water were collected and transported under licence to the  

The water and soils and crop plants materials after the necessary treatment were digested with aqua regia in a hot block and were analyzed for both major and trace metals contents using Inductively Coupled Plasma Emission Spectrometry (ICP - OES) and Inductively Coupled Plasma Mass Spectrometry (ICP - MS) techniques. The anions in the water samples were determined by means of ion chromatography. Water physical parameters such as pH and conductivity were determined in-situ in the field. Also, soil parameters such as pH, total organic carton (TOC) as well as particle size were determined using standard methods.

The full results of the work are in various stages of preparation for publication and will include assessment to:

  • Allow comparison with existing global soil/plant/water data bases.
  • Establish the relationship between micronutrients and trace elements in soils and plants and possible implications to the health of humans in the area of study.
  • It is anticipated that this will provide a guide for policy analysis, environmental and health management decisions in the rapid urbanizing environment of Calabar and environs where my home University is located.

In addition, during my Fellowship, I was able to update and acquire new analytical skills and support to enable me to obtain a tenured position and scientific leadership in the area of Environmental Geochemistry at the University of Calabar (Nigeria). 

 

Activities included typical staff induction and orientation activities, advanced lecture courses in analytical techniques and measurement processes, seminars on environmental geochemistry - including iodine deficiency as well as research funding guidance. I also met many researchers, academics and technicians from Universities and regulatory organisations in the local area and had contact with other Commonwealth Fellows in the UK. I also had the opportunity to supervise UWS students in practical lab work.

All these activities were very relevant to my research at UWS as well as for my future career back in Nigeria as I am acquainted with the recent advances and analytical techniques in the area of environmental geochemistry and health of humans

My research stay in Scotland and UK has been very joyous, beneficial and successful as can be seen from the above report. The enabling environment to carry out this work to a successful completion was due to the receptive, friendly and accommodating people I met within and out of UWS.

 

I would like to thank Prof Andrew Hursthouse for accepting to host me, supervision and guidance, the University of the West of Scotland for access to facilities at the School of Science, the Commonwealth Scholarship Commission and British Council for funding and for their support prior to my visit and during the period of my fellowship and the authorities of the University of Calabar for the nomination and granting a study leave for me to take up the fellowship. The contributions of my head of department, Prof Aniekan Edet and colleague, Prof CS Okereke, SEGH and Dr Michael Watts of the British Geological Survey in UK for finding me a host institute are appreciated. The assistance provided in various aspects of the research work by Dr Simon Cuthbert, Dr John Hughes, Mr David Wallace, Mr Charlie McGuinnes, Ms Margaret Train and Natalie Dickson are also appreciated.

Finally my sincere and special thanks to Mr David Stirling for skills acquired and updated in the use of ICP-AES and ICP-MS and Mr Iain Mclellan for skills updated in the determination of some soil bulk parameters in soils.

Dr. Therese Ntonzi Nganje, University of Calabar, Nigeria

Keep up to date

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Fertilizer usage and cadmium in soils, crops and food 2018-06-23

    Abstract

    Phosphate fertilizers were first implicated by Schroeder and Balassa (Science 140(3568):819–820, 1963) for increasing the Cd concentration in cultivated soils and crops. This suggestion has become a part of the accepted paradigm on soil toxicity. Consequently, stringent fertilizer control programs to monitor Cd have been launched. Attempts to link Cd toxicity and fertilizers to chronic diseases, sometimes with good evidence, but mostly on less certain data are frequent. A re-assessment of this “accepted” paradigm is timely, given the larger body of data available today. The data show that both the input and output of Cd per hectare from fertilizers are negligibly small compared to the total amount of Cd/hectare usually present in the soil itself. Calculations based on current agricultural practices are used to show that it will take centuries to double the ambient soil Cd level, even after neglecting leaching and other removal effects. The concern of long-term agriculture should be the depletion of available phosphate fertilizers, rather than the negligible contamination of the soil by trace metals from fertilizer inputs. This conclusion is confirmed by showing that the claimed correlations between fertilizer input and Cd accumulation in crops are not robust. Alternative scenarios that explain the data are presented. Thus, soil acidulation on fertilizer loading and the effect of Mg, Zn and F ions contained in fertilizers are considered using recent \(\hbox {Cd}^{2+}\) , \(\hbox {Mg}^{2+}\) and \(\hbox {F}^-\) ion-association theories. The protective role of ions like Zn, Se, Fe is emphasized, and the question of Cd toxicity in the presence of other ions is considered. These help to clarify difficulties in the standard point of view. This analysis does not modify the accepted views on Cd contamination by airborne delivery, smoking, and industrial activity, or algal blooms caused by phosphates.

  • Effects of conversion of mangroves into gei wai ponds on accumulation, speciation and risk of heavy metals in intertidal sediments 2018-06-23

    Abstract

    Mangroves are often converted into gei wai ponds for aquaculture, but how such conversion affects the accumulation and behavior of heavy metals in sediments is not clear. The present study aims to quantify the concentration and speciation of heavy metals in sediments in different habitats, including gei wai pond, mangrove marsh dominated by Avicennia marina and bare mudflat, in a mangrove nature reserve in South China. The results showed that gei wai pond acidified the sediment and reduced its electronic conductivity and total organic carbon (TOC) when compared to A. marina marsh and mudflat. The concentrations of Cd, Cu, Zn and Pb at all sediment depths in gei wai pond were lower than the other habitats, indicating gei wai pond reduced the fertility and the ability to retain heavy metals in sediment. Gei wai pond sediment also had a lower heavy metal pollution problem according to multiple evaluation methods, including potential ecological risk coefficient, potential ecological risk index, geo-accumulation index, mean PEL quotients, pollution load index, mean ERM quotients and total toxic unit. Heavy metal speciation analysis showed that gei wai pond increased the transfer of the immobilized fraction of Cd and Cr to the mobilized one. According to the acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) analysis, the conversion of mangroves into gei wai pond reduced values of ([SEM] − [AVS])/f oc , and the role of TOC in alleviating heavy metal toxicity in sediment. This study demonstrated the conversion of mangrove marsh into gei wai pond not only reduced the ecological purification capacity on heavy metal contamination, but also enhanced the transfer of heavy metals from gei wai pond sediment to nearby habitats.

  • Cytotoxicity induced by the mixture components of nickel and poly aromatic hydrocarbons 2018-06-22

    Abstract

    Although particulate matter (PM) is composed of various chemicals, investigations regarding the toxicity that results from mixing the substances in PM are insufficient. In this study, the effects of low levels of three PAHs (benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene) on Ni toxicity were investigated to assess the combined effect of Ni–PAHs on the environment. We compared the difference in cell mortality and total glutathione (tGSH) reduction between single Ni and Ni–PAHs co-exposure using A549 (human alveolar carcinoma). In addition, we measured the change in Ni solubility in chloroform that was triggered by PAHs to confirm the existence of cation–π interactions between Ni and PAHs. In the single Ni exposure, the dose–response curve of cell mortality and tGSH reduction were very similar, indicating that cell death was mediated by the oxidative stress. However, 10 μM PAHs induced a depleted tGSH reduction compared to single Ni without a change in cell mortality. The solubility of Ni in chloroform was greatly enhanced by the addition of benz[a]anthracene, which demonstrates the cation–π interactions between Ni and PAHs. Ni–PAH complexes can change the toxicity mechanisms of Ni from oxidative stress to others due to the reduction of Ni2+ bioavailability and the accumulation of Ni–PAH complexes on cell membranes. The abundant PAHs contained in PM have strong potential to interact with metals, which can affect the toxicity of the metal. Therefore, the mixture toxicity and interactions between diverse metals and PAHs in PM should be investigated in the future.