The supply of total nitrogen and total phosphorus from small urban catchments into the Gulf of Gdańsk

The main goal of work was to quantify the nitrogen and phosphorus loads transported by small streams to the Gulf of Gdańsk. The research aims to determine wastewater release volumes over time, instead of focusing only on spatial distributions. Another aim is to identify the main determinants potentially affecting water quality in rivers flowing across the city of Sopot. The study area consists of six small river catchments located in the city of Sopot, each with an open flow channel, which lies along the bay. Studies were conducted 12 times per year in the period from March 2014 to February 2015. Laboratory analyses were performed to determine the concentration of both total nitrogen and total phosphorus. In order to calculate pollutant loads, discharge was also measured in each of studied rivers. Conducted research has shown that all analyzed streams were characterized by low total nitrogen and total phosphorus concentrations. The mean annual values ranged from 0.60 to 1.28 mg·dm-3 in case of total nitrogen and from 0.066 to 0.100 mg·dm-3 in case of total phosphorus. In 2012, the total nitrogen load from Poland to the Baltic Sea was 210.768.000 kg N while the total phosphorus load was 15.269.000 kg P, which means that streams analyzed in this paper supplied barely 0.002 % of the biogenic load supplied to the Baltic Sea by Poland as a whole.