Effect on reclamation on mercury concentration in groundwater: a case study of Luboń Chemical Plant (Poznań, Poland)

Lubon Chemical Plant (Poland), founded in 1914, is the place where many products such as superphosphate, hydrofluoric acid, sulfuric acid, aluminum fluoride, potassium fluoroborate, vanadium catalyst and other chemicals and post-production waste have been produced and stored. The main products manufactured by Lubon Chemical Plant are powdered superphosphate (obtained from apatite) and sulfuric acid (obtained from pyrite) The aim of the study was to determine the impact of the former post-crystallization leachate disposal site located in the area of Lubon Chemical Plant on groundwater contamination with mercury. Groundwater samples were collected from 12 piezometers in the area of the plant or in close vicinity to the plant, and from one piezometer located 2.5 km north of the study area, i.e., from Poznan-Debina groundwater intake, in the years 2007–2014. Total mercury concentration in groundwater from Lubon was high in all samples, and ranged from 10.9 to 2818 ng L− 1 (average 335 ± 509 ng L− 1, median = 158 ng L− 1). The highest mercury concentration values were measured in piezometer no. 7, located in close proximity to the production facilities of the chemical plant, and they equaled 2604 ng L− 1 in 2007 and 2818 ng L− 1 in 2008. The lowest concentration of mercury (10.9 ng L− 1) was determined in 2014, in a sample taken from piezometer no. 13 located at the water intake for the agglomeration of Poznan (Poznan-Debina). Based on the obtained results, two sources of groundwater pollution were found: (1) Lubon Chemical Plant, and (2) former post-crystallization leachate disposal site. A decrease in mercury concentrations with increasing distance of piezometers from the pollution sources was reported. Moreover, a reduction in mercury concentration over the years has been observed, especially after completion of reclamation and remediation works in the area of Lubon Chemical Plant in 2008. Despite the negative impact of the plant on groundwater quality measured in the piezometer located at the water intake Poznan-Debina, the drinking water quality guidelines (1000 ng L− 1) was not exceeded.