Monitoring and attenuation dynamics of riverine surface waters contaminated by petroleum hydrocarbons under conflict-affected conditions: processes, kinetics and implications for SDG achievement.

This study examines the temporal dynamics of petroleum hydrocarbon contamination and natural attenuation processes in riverine surface waters affected by military-related accidental pollution. Time-series monitoring data from six rivers located in eastern and western regions were analysed to quantify concentration exceedances, rates of decline, and differences in self-purification capacity among river systems. Petroleum hydrocarbon concentrations were determined using a standardised fluorimetric method, and their temporal behaviour was evaluated through descriptive statistics and first-order kinetic modelling. Extremely high peak concentrations were recorded following accidental releases, exceeding regulatory thresholds for fisheries and domestic water use by one to two orders of magnitude. Although a consistent decreasing trend was observed in all rivers, median and mean concentrations in several cases remained above regulatory limits for extended periods. Estimated half-times of concentration reduction varied markedly among rivers, reflecting differences in hydrological conditions, channel morphology, urbanisation, and dilution capacity. The results demonstrate that natural attenuation plays a significant role in reducing petroleum hydrocarbon levels, but is insufficient to fully offset the impacts of large-scale and repeated pollution events under conflict conditions. These findings highlight the need for integrated monitoring, targeted mitigation measures, and long-term restoration strategies to support sustainable water management during post-conflict recovery.