Substances and nutrients in the Moonsund and the Gulf of Riga

The aim of the research was to support the measures planned in the development plan of the Estonian Marine Strategy, incl. the determination of classes of the environmental status of the marine environment, the assessment of the environmental status and the achievement of a good environmental status. Sediment samples, sediment profiles if possible, and bottom water layer profiles were taken from 5 Moonsund and 12 Gulf of Riga stations. Sediment samples (50 samples in total) were analyzed for dry matter content, fine fraction (<2 µm) content, organic matter content, total phosphorus, total nitrogen, arsenic, lead, cadmium, chromium, copper, zinc, mercury, 9 polyaromatic hydrocarbons (PAHs), mineral oils, 7 polychlorinated biphenyls (PCBs), 12 polybrominated diphenyls (PBDEs) and 10 organotin compounds in the sediment surface layer (0-5 cm). Based on the work, it was claimed that the environmental condition of the sediment of the Moonsund and the Gulf of Riga is good. However, we cannot say that some organic compounds, in particular carcinogenic polyaromatic hydrocarbons (PAHs) and organotin compounds, do not pose a risk to living organisms. In the future, it would be necessary to study the distribution of organotin and PAHs in the central part of the Gulf of Riga with more precise methods, and the content of PAHs in the bottom water layer should also be studied.