Tracing PAH emissions from leisure boats in a low tidal coastal area, including comparison with Environmental Quality Standards (EQS)

The approximately 850,000 recreational boats in Sweden, has shown to have a significant impact on the marine environment of the Swedish west coast. The extensive weather-protected archipelagos and fjords with minor tidal activity, offers excellent conditions to uncover traces of leisure boats exhaust from the background. In this study we focus on polycyclic aromatic hydrocarbons (PAHs) from boat exhausts in surface sediments and water (using SPMD) in a busy harbour and a pristine fjord. The PAH analyses were performed using gas chromatography - mass spectrometry after suitable extraction procedures. Concentrations of total PAHs in water and sediments was 4-8 ng/L and 200-5500 ng/g respectively. In addition to PAH measurements, we used the number of documented motorboat passages together with residence time of water, to quantify the concentration enhancement of up to 40% due to recreational boating. Here we have for the first time succeeded in distinguishing the leisure boat PAH signature in coastal marine environments. This by combining our data and observed compositions from lakes where emissions from leisure boats is documented as a dominating source of pollution. Comparisons with Environmental Quality standards (EQS) showed elevated levels of up to more than five times in the most exposed sediments, while the water concentrations were below the EQS. The study concludes that boating activities significantly contribute to PAH-levels in these coastal environments, with implications for environmental management and pollution mitigation strategies.