SEGH Articles

Geochemistry in Africa

26 January 2017
Read about VicFalls 2018 and fieldwork in the Copperbelt

Michael Watts and Elliott Hamilton returned to Africa to undertake two main tasks; (1) find a conference venue for the Society for Environmental Geochemistry 2018 international conference to be hosted in Victoria Falls, and (2) undertake fieldwork in the Zambian copperbelt as part of the Royal Society-DFID project (Royal Society-DFID project).

We met up with Dr Godfrey Sakala (Zambian Agriculture Research Institute) and Professor Florence Mtambanengwe (University of Zimbabwe) in Victoria Falls and viewed venues for hosting 150-200 people.  The location is ideally suited, with ample accommodation, conference facilities, transport connections, activities, is safe to walk around and of course the spectacle of Victoria Falls. The Falls are a must see and a gentle introduction to Africa for the uninitiated, with many National Parks close by in Zimbabwe, Zambia and Botswana.  A video was filmed to begin the promotion of the conference and signpost SEGH 2018 VicFalls which will appear on  shortly.

We moved onto Zambia with Dr Sakala and headed up to Kitwe in the Copperbelt to join Prof. Maseka from the Copperbelt University to follow up on previous field collections in Mugala village where field characterisation identified specific plots for experimental trials to investigate the influence of soil management strategies, such as organic incorporation, liming, low tillage (Conservation Agriculture) on the uptake of metals deposited through dust onto agricultural soils from nearby mine tailings.  Elliott Hamilton will explain more in a follow-up blog about his PhD and some of the findings so far.  Belinda Kaninga, one of our Royal Society-DFID PhD students has set out her first season field experiments as identified by the site characterisation and will bring the resultant soil and crop samples to BGS for analysis next May. 

Both Elliott and Belinda are using the same location for experimental trials, with Elliott focussing on the control parameters for Chromium (Cr) soil-to-crop transfer employing elemental speciation and isotope dilution for pot experiments using soil samples collected on this visit across the range of Cr concentrations and soil pH identified. These experiments will be undertaken at Sutton Bonington campus (University of Nottingham).  The processing of samples back in ZARI also allowed us to work with lab staff, review training needs and preparations for our upcoming purchase of Microwave-Plasma Atomic Emission Spectrometers in each of Malawi, Zambia and Zimbabwe. Meanwhile, Belinda is investigating a broad panel of metals (Pb, Cu, Zn, Cd, Mn, Al, Ni) and the application of specific Conservation Agriculture methodologies and potential influence on the availability of metals for soil-to-plant uptake.  Belinda has conducted pot trials at the ZARI research station in Lusaka, but as mentioned, recently set up her field plots in collaboration with the village chief and local farmers which will run over two growing seasons.  

A further project was initiated with Prof. Maseka and Dr Sakala to investigate the potential exposure to metals from dust inhalation from the Mugala mine tailings in the nearby village, comparing pathways of exposure from environmental samples through to biological samples from a biomonitoring collection (urine, blood).  The focus of the project will be a two-year MSc project undertaken by Lukundo Nakaona, in collaboration with the CBU Department for Environmental and Agricultural Sciences and Medical School, ZARI and BGS-UoN (CEG).  There are many other possibilities for environmental-health exposure and food security studies with our close partners at ZARI, CBU and UNZA (University of Zambia).  In particular, scope for GCRF proposals to provide capacity strengthening in technical capability to cement the strong scientific activities of our partners both in Zambia, the wider Royal Society-DFID network in Zimbabwe and Malawi and with other partners in Kenya and Tanzania.

By Michael Watts, Elliott Hamilton, Belinda Kaninga, Kenneth Maseka and Godfrey Sakala

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

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  • Study of the interactions of dissolved organic matter with zinc ion and the impact of competitive metal ions (Ca 2+ and Mg 2+ ) by in situ absorbance 2017-06-22


    The bioavailability and toxicity of zinc to aquatic life depend on dissolved organic matter (DOM), such as Suwannee River Fulvic Acid (SRFA), which plays an important role in the speciation of zinc. This study examined reactions of SRFA with zinc at different concentrations from pH 3.0 to 9.0, and competitive binding of calcium/magnesium and zinc to SRFA at pH 6.0, using in situ absorbance. Interactions of Zn2+ with SRFA chromophores were evidenced by the emergence of features in Zn-differential spectra. Among all Zn2+–SRFA systems, dominant peaks, located at 235, 275 and 385 nm, and the highest intensity at 235 nm indicated the replacement of protons by the bound Zn2+. The Zn2+ binding with SRFA could be quantified by calculating the changes of the slopes of Zn-differential log-transformed absorbance in the wavelength range of 350–400 nm (denoted as DS350–400) and by comparing the experimental data with predictions using the Non-Ideal Competitive Adsorption (NICA–Donnan) model. DS350–400 was correlated well with the bound Zn2+ concentrations predicted by NICA–Donnan model with or without Ca2+ or Mg2+. Ca2+ and Mg2+ only affect intensity of the Zn-differential and Zn-differential log-transformed absorbance, not shape. In situ absorbance can be used to gain further information about Men+–DOM interactions in the presence of various metals.

  • Blood concentrations of lead, cadmium, mercury and their association with biomarkers of DNA oxidative damage in preschool children living in an e-waste recycling area 2017-06-16


    Reactive oxygen species (ROS)-induced DNA damage occurs in heavy metal exposure, but the simultaneous effect on DNA repair is unknown. We investigated the influence of co-exposure of lead (Pb), cadmium (Cd), and mercury (Hg) on 8-hydroxydeoxyguanosine (8-OHdG) and human repair enzyme 8-oxoguanine DNA glycosylase (hOGG1) mRNA levels in exposed children to evaluate the imbalance of DNA damage and repair. Children within the age range of 3–6 years from a primitive electronic waste (e-waste) recycling town were chosen as participants to represent a heavy metal-exposed population. 8-OHdG in the children’s urine was assessed for heavy metal-induced oxidative effects, and the hOGG1 mRNA level in their blood represented the DNA repair ability of the children. Among the children surveyed, 88.14% (104/118) had a blood Pb level >5 μg/dL, 22.03% (26/118) had a blood Cd level >1 μg/dL, and 62.11% (59/95) had a blood Hg level >10 μg/dL. Having an e-waste workshop near the house was a risk factor contributing to high blood Pb (r s  = 0.273, p < 0.01), while Cd and Hg exposure could have come from other contaminant sources. Preschool children of fathers who had a college or university education had significantly lower 8-OHdG levels (median 242.76 ng/g creatinine, range 154.62–407.79 ng/g creatinine) than did children of fathers who had less education (p = 0.035). However, we did not observe a significant difference in the mRNA expression levels of hOGG1 between the different variables. Compared with children having low lead exposure (quartile 1), the children with high Pb exposure (quartiles 2, 3, and 4) had significantly higher 8-OHdG levels (β Q2 = 0.362, 95% CI 0.111–0.542; β Q3 = 0.347, 95% CI 0.103–0.531; β Q4 = 0.314, 95% CI 0.087–0.557). Associations between blood Hg levels and 8-OHdG were less apparent. Compared with low levels of blood Hg (quartile 1), elevated blood Hg levels (quartile 2) were associated with higher 8-OHdG levels (β Q2 = 0.236, 95% CI 0.039–0.406). Compared with children having low lead exposure (quartile 1), the children with high Pb exposure (quartiles 2, 3, and 4) had significantly higher 8-OHdG levels.