Advances in Biology & Earth Sciences

The study aimed to conduct environmental monitoring and a comparative analysis of Azerbaijan’s major transboundary rivers (Aras, Okhchuchay, Bargushadchay, Ganikhchay) and internal rivers (Ganjachay, Lankaranchay) exposed to anthropogenic and climatic pressures. Water and sediment samples were collected from multiple sites throughout the year and ecological conditions were assessed using hydrochemical, hydrobiological and microbiological indicators. These included temperature, pH, dissolved oxygen, concentrations of nitrites, nitrates, ammonium, phosphates, as well as the abundance of saprotrophic, nitrogen-fixing, denitrifying and oil- and phenol-degrading bacteria. The results revealed that Okhchuchay was the most polluted river, with biogenic substance concentrations and microbial indicators exceeding permissible standards, reflecting severe organic and chemical contamination from transboundary sources. Pollution levels in other rivers varied seasonally and depended on local anthropogenic activities. The absence of modern wastewater treatment facilities and centralized sewage systems in many areas was identified as a key factor exacerbating river pollution. This research highlights the necessity of continuous environmental monitoring and the urgent modernization of wastewater management infrastructure. It also underscores the importance of strengthening international cooperation in managing transboundary water resources. The findings provide crucial data for developing sustainable water policies and safeguarding aquatic ecosystems and biodiversity.