Content and Speciation of Phosphorus in Lake Kórnickie

This paper presents the speciation of phosphorus in bottom sediments and its spatial variability in Lake Kórnickie. This study provides a quantitative determination of the abundance and chemical speciation of P and potential P-release rates from Lake Kórnickie. Phosphorus (P) is an important macronutrient that can limit primary productivity in fresh water ecosystems. The study was conducted during the hydrological years 2016–2018. The speciation analysis was carried out using Visual Minteq software. The predominant form of orthophosphate (V) in the waters of Lake Kórnickie was the HPO42− anion, which was related to the reaction of the studied waters. Conditions favoring the precipitation of orthophosphates to hydroxyapatite, aragonite, and calcite prevailed in the lake waters. No cyclic periods of deposition of minerals and release of phosphorus from bottom sediments were observed and, for most of the study period, the lake acted as a “trap” for phosphorus at point JK1. The findings of this study suggest that the internal sedimentary P loading contributes substantial bioavailable P to the water column at one of sampling points (JK2). The accumulation of phosphorus in bottom sediments meant that the lake restoration processes carried out in various lakes may not have had the intended results. At the same time, bottom sediments can be a secondary source of pollution of river waters with this element despite the reduction of inflow from the catchment area of this element.