Seasonal Variations in Pollution in Swedish Watercourses

The study covered a wide range of substances, including pharmaceutical residues, PFAS and pesticides, revealing that pollutant levels vary throughout the year and across different geographical locations.

- Based on our findings, we can conclude that pollutants are not solely originating from wastewater treatment plants but it is one of many sources of how these contaminants enter the water environment, says Oksana Golovko, researcher and one of the authors of the report.

Seasonal Variations and Unexpected Findings

The most frequently detected compounds were the two stimulants nicotine and caffeine, and among the pesticides diethyltoluamide (DEET). The research shows that certain substances appear in higher concentrations during specific seasons. For instance were antihistamines, commonly used to relieve allergy symptoms, found in higher quantities during spring sampling, coinciding with increased consumption. Also, most locations showed high PFAS concentrations in May compared to autumn samples. Other factors, such as weather and UV light, also influence how concentrations of various substances can change over time. Heavy rain following a dry period can for example transport substances stored in the soil into watercourses.

Golovko also highlights an unexpected finding of the antidepressant venlafaxine, as it was detected in samples from several remote and seemingly pristine locations.

Pollutant Levels and Thresholds

The study identified several substances exceeding established threshold values based on the current annual average (AA) Environmental Quality Standard (EQS) for inland surface waters. A common ingredient in anti-inflammatory drugs called diclofenac was exceeded at two out of 34 sites and PFOS (a PFAS substance) was exceeded at almost half of the sites (14 out of 34 sites). Some of the studied chemicals are so called endocrine disruptors, which can alter behavior, harm cells, and even skew the balance of male and female populations in wildlife.

Ongoing Environmental Monitoring is Crucial

Continued research and monitoring are crucial to uncover where these organic micropollutants come from, how much is present in the environment, and the damage they might cause to ecosystems.

The published report marks an important step in understanding and managing organic micropollution in Sweden's watercourses. It provides valuable insights that can be used in ongoing efforts to monitor and protect the country’s water resources.