Weather Factors and E. coli Concentration in Barnviken, Malmö - A Linear Mixed Model Approach

Sammanfattning: Barnviken in Malmö has persistently encountered challenges associated with elevated concentrations of Escherichia coli (E. coli) without a discernible source of contamination. A notable concentration peak has been identified at the outflow of the stream traversing Hammer's Park, prompting speculation regarding the stream's potential role as the origin of the contamination. In order to investigate this hypothesis, sampling of E. coli concentrations was conducted at various points along the stream during the spring and summer of 2023. Two models were developed to analyze the spring and summer samples separately, employing the linear mixed model. Water temperature and rainfall were incorporated as explanatory variables to ascertain whether elevated concentrations could be attributed to weather factors. The spring model yielded statistically significant estimates for both water temperature and rainfall, affirming their impact on E. coli concentrations. Conversely, the summer model, optimized for improved fit, excluded rainfall as a parameter, with water temperature failing to attain statistical significance. The discerned disparity in results led to the conclusion that factors influencing contamination during the summer differ from those present in the spring. Postulated explanations encompass potential leakages from proximate sanitary facilities, heightened pollution from nearby camping sites, or increased presence of seagulls in the vicinity.