Lithium and heavy metal concentration analysis in Sajó valley

Abstract

The Sajó valley was a blooming industrial area 20-25 years ago, but in the early 1990s most of the factories closed down, but relatively little attention was paid to the pollution left behind. The Green Action Association carried out a comprehensive monitoring of the Sajó Valley in the early 1990s. This gave us the idea to carry out our work, as significant heavy metal and lithium pollution was found in the areas surveyed. It is very likely that this was mainly caused by heavy industry from the 19th century until the 1980s. Our aim was to investigate how the lithium and heavy metal contamination might be found in some of the areas studied by the association more than 20 years later. Six areas were selected as study sites for the soil samples, between Ónod and Muhi (3 areas) and near Tiszaszederkény and Tiszagyulaháza (3 additional areas). Our soil samples were collected from the floodplains of the Sajó, Hernád and Tisza rivers at a depth of 0-40 cm. After proper storage, we started the analysis by preparing and digesting the samples. The pH-value and dry matter content of the sieved (2 mm) samples were determined. Digestion of the finely sieved samples (0.45 mm) with nitric acid using a Milestone 1200mega microwave digestion system allowed the samples to be analyzed with an "ATI UNICAM 939 AAS" atomic absorption spectrometer for seven elements: cadmium, copper, zinc, lead, manganese, iron and lithium. The results of the measurements were converted to mg/kg dry matter. The results obtained showed that there are still areas where some elements, such as Cd, are contaminated above the limit values (Joint Decree 6/2009 (IV. 14.) of the Ministry of Agriculture, Forestry, Environment and Water Management). The measured pH values are slightly alkaline and slightly acidic, which means that the contaminants are immobile in the soil. Statistical evaluation was performed by use of the three-factor random block analysis variance method using SPSS 14.0 for Windows software package. After performing analysis of variance, it was shown that the heavy metal content of soil samples was significantly related to the sampling location. Based on the data obtained in our work, we propose to carry out a study of similar magnitude to the monitoring carried out in the 1990s and to clean up the contaminated soils