Assessing the Ecological Risks of Gold Mining in Tanzanian River Systems / 3.11.2026

Researchers from the Department of Environmental Sciences (Marko Štrok, Tjaša Žerdoner and Tea Zuliani) have co-authored a new scientific article “Multi-tributary seasonal patterns and exploratory source identification of potentially toxic elements in water and sediments: Ecological risks screening in a gold - mining river systems, Northern, Tanzania”.

The study, published in the Journal of Hazardous Materials (https://doi.org/10.1016/j.jhazmat.2026.143939), looks at the Mara and Mori rivers, which drain gold-mining areas into Lake Victoria. The work is part of the PhD thesis of Dorice Rashid Seif.

The main aim of the study was to find out how arsenic, uranium, lead, cadmium, copper and zinc are distributed in river water and sediments across the Mara River, its tributaries and the Mori River, and how these change between seasons. The potential ecological risk was assessed, and sites that need the most attention were identified.

Sediments showed clear seasonal differences: concentrations were significantly lower in the rainy season, whereas dissolved concentrations in water did not change significantly between seasons. Arsenic and cadmium were the main concern in sediments, exceeding levels at which harmful effects on aquatic life become likely in about a third and a sixth of samples, respectively, mostly in tributaries draining mining areas. In water, arsenic and lead exceeded drinking-water guidelines at some sites. The estimated ecological risk depended strongly on the natural background values used for comparison, but both approaches identified the same priority sites. These findings provide a basis for targeted monitoring of contamination hotspots in the region.

The work was supported by the International Atomic Energy Agency (project INT0101), the Slovenian Research and Innovation Agency (programmes P1-0143 and P2-0075) and the Tanzania Commission for Science and Technology (COSTECH).