Salinity changes in the Bay of Puck due to brine discharge based on in-situ measurements

Brine, a by-product in the process of constructing gas storage caverns in salt deposits, has been discharged into Puck Bay by a system of diffusers since autumn 2010. In-situ measurements taken in the period of October 2010–December 2012 were used to assess salinity changes in the vicinity of the discharge installation. The measured salinity values included two components: the natural, representing salinity in the absence of discharge, and salinity excess due to brine discharge. Owing to the limited number of locations in the Gulf of Gdańsk where the national program of monitoring environmental changes is carried out, it was impossible to determine exactly the natural component. As a consequence, four estimation methods were proposed. A detailed analysis was carried out for the second half of 2012, when parameters of brine were close to the maximum permissible values. It was found that the average salinity excess in the vicinity of the installation rarely reached 0.5 PSU, and the maximum values at individual sites occasionally reached 0.6 PSU. It was shown that the local wind plays an important role in brine mixing with the surrounding environment, however, it is not sufficient to explain the observed salinity patterns.