Methodological inconsistencies and variations in environmental pollution reports: A case study of the mining-affected Geita region, Tanzania

Abstract

Various studies report pollutant levels in the environment to raise awareness and call for government intervention to protect the environment and public health. However, inconsistent findings across studies complicate environmental actions and policy-making processes in many countries. Geita region in Tanzania is one of the areas with a high focus on metal pollution problems emanating from artisanal, small-scale, and industrial mining operations. This article presents a review of environmental studies conducted in the region as a case study to show the impacts of inconsistent methodological approaches resulting to varying pollutant levels of heavy metals (Hg, As, Pb, Zn and Ni) in soil, sediment, rice and water. The diversity of metal pollutant concentrations is caused by varying sample treatment methods, which result from a lack of standardised analytical methods for various pollutants within the country. For example, two different studies reported different total mercury (THg) concentrations in soil samples near the Geita gold mine: 1.89 mg/kg and 0.0625 mg/kg. Similarly, arsenic (As) levels were reported as 126.1 mg/kg and 5.5 mg/kg, while lead (Pb) concentrations varied between 23.46 mg/kg, 2.58 mg/kg, and 17.99 mg/kg in different studies of the same area. Classical analytical instruments were used in the analyses, including Atomic Absorption Spectroscopy (AAS), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Energy Dispersive X-ray Fluorescence (EDXRF), and Cold Vapour Atomic Fluorescence Spectrometry (CV-AFS). However, there have been diverse sample pre-treatment methods, including sample drying techniques, sample digestion, and chemical mixture ratios, that contribute to the differences in results. Although sampling seasons and weather conditions were not reported by the different authors, they likely contributed to the observed variations. To address these discrepancies, this review suggests establishing standardised analytical methods for different pollutants to ensure uniform procedures and comparable results in the country. This standardisation would aid in effective decision-making and policy formulation to manage environmental and health risks in mining-affected and other polluted areas.

Keywords: Analytical methods; Environmental policy; Metal concentrations; Standard methods.

Fig. 1

Summary of sample treatments and analytical methods from Table 1a, Table 1b, Table 1c, Table 2a, Table 2b, Table 3, Table 4, Table 5 for different metal residues in environmental samples, highlighting variations and the resulting incomparability of findings.