Integrated assessment of the surface source of water supply according to environmental-risk indicators

Abstract

The risk assessment provides a basis for comparing, ranking and prioritizing risks and assessing environmental impacts as functions of stressors in a river basin. The main sourc- es of pollution of the Dnipro Reservoir are discharge of wastewater into the river without proper treatment; uncontrolled discharges of wastewater; non-compliance with the regime in bank strips and water-protection zones; and bank erosion. Health-risk assessment includes four main stages: hazard identification, exposure assessment, dose-effect assessment, and risk characterization. We determined that according to all parameters – except BSK5, HSC, and suspended matter – the water meets the regulation standards of the Hygienic Water-Quality Standards of Water Bodies to Meet the Drinking, Household and Other Needs of Population, but does not reach the upper limit of the 1st quality class according to DSTU 4808:2007. Also, the average annual values were significantly above the minimum values of the examined parameters. There was a decrease in the level of BOD5 at the checkpoints in the city of Dnipro, indicating invasion of the watercourse (points 4 and 5) by substances that inhibit biochemical processes. The same parameter decreased at the checkpoint where the River leaves the city limits and further downstream, suggesting an influx of organic compounds. The oxygen content was observed to decline in the part of the watercourse located in the city (points 4 – 8) and increase in the middle and lower parts of the reservoir. There was also seen a trend of growth of sulfates, nitrogen compounds, phosphates, synthetic surfactants and COD at the control checkpoints located within the city of Dnipro. As a result of the risk assessment of the impact of anthropogenic activities of the Dnipro agglomeration on the Dnipro Reservoir, we determined that nitrites, nitrates and phosphates and suspended solids are the priority substances in the list. This can impose negative impacts on the health, causing mutagenic and carcinogenic effects, and enhance the eutrophication of the surface water. The Dnipro agglomeration has been causing a negative ecological impact on the Dnipro Reservoir, increasing the risk value from 0.999999206 (checkpoint 3, before the city of Kamianske) to 0.999999924 (checkpoint 6, where the River leaves the city limits).