Mineralogical control and human impacts on the Girdiman River water chemistry in the Eastern Greater Caucasus, Azerbaijan

Understanding the geochemical controls on river water chemistry is critical for sustainable freshwater management, particularly in mountain regions. This study investigates the controls on water chemistry in the Girdiman River catchment, Greater Caucasus, Azerbaijan, focusing on lithology, mineral weathering, soil processes, and anthropogenic inputs.
Water, sediments, and soil samples were analysed using ICP-OES, XRF, and XRD. Mineral dissolution rates were quantified through batch, flow-through, and leaching-column experiments, while PHREEQC modelling was used to interpret solute behaviour.
River water chemistry varies with lithology. Ca dominates, followed by Mg in the upper reaches, reflecting rapid carbonate dissolution. Downstream, Na concentrations increase relative to Mg, consistent with albite-rich silicate rocks. Relatively constant K concentrations reflect the slow, continuous dissolution of muscovite, the only identified K-bearing mineral. Low Si mobility and undetected Al and Fe in river water are consistent with secondary mineral formation during incongruent silicate weathering.
Experimental results demonstrate contrasting dissolution rates under different conditions. Carbonates dissolve rapidly, promoting slightly alkaline pH, whereas slower silicate dissolution encourages secondary mineral precipitation, incorporating or adsorbing cations. Leaching-column experiments and comparisons of soil compositions indicate that irrigation and soil processes, including cation exchange, may further influence elemental release and river water chemistry.
Anthropogenic inputs also affect river water quality. In the middle reaches, where settlement density increases, nitrate and ammonium concentrations approximately double relative to upstream levels, and pharmaceuticals, particularly methylisothiazolinone, metformin, and caffeine, are detected. Concentrations remain below guideline limits, while phosphate is undetected.
This study demonstrates that river water chemistry reflects the combined influence of lithology, mineral dissolution kinetics, soil processes, and population density. Integrating field observations, laboratory experiments, and geochemical modelling provides new insights into natural weathering and anthropogenic influences, supporting sustainable water resource management in the Greater Caucasus.