Accurate and reliable laboratory results are an extremely important and integral part of conducting scientific research. Many factors influence the results obtained, including the type of determination method, accuracy and precision of measurements, and laboratory equipment used for the tests. This paper presents the results of measurements of heavy metal concentration in soil using two methods for adding soil components into solution and different laboratory methods and types of measuring equipment. The first method used was hot digestion of soil samples with a mixture of concentrated HNO₃ and HClO₄, after prior ashing of organic matter (IUNG method). The second method was a two-stage decomposition, where soil samples were hot digested, initially with oxidizing acid (HNO₃) and subsequently with non-oxidizing acid (HF) (two-stage decomposition). The concentrations of selected heavy metals (Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined in solutions obtained by both digestion methods. The solutions obtained from soil decomposition were determined twice using atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP MS) methods in different laboratories using different types of spectrometers. In most cases, the measured concentrations of heavy metals are the highest for the two-stage solution samples and the measurements of their concentrations carried out using ICP. The exceptions are the measurements of Cu and Ni concentrations. In the case of Cu, lack of significant differentiation in concentrations of this metal may result from different forms of occurrence of Cu in soil than in the case of other metals. For Ni, however, a reversal of the trends seen for the other metals is observed and the type of spectrometer used for measurements is important. There may be an interference of the spectrometric spectrum of Ni with the spectra of the other determined metals. However, this is not clear at the present stage of the study. In conclusion, the results of this study indicate that the choice of soil sample preparation and the type of spectrometer used for measurements can, in many cases, determine the value of laboratory results, even if it is in an expected range of standard material. Research of published papers proved that most of them show only results based on one selected course of methodology without comparison with others. The novelty of the paper is the comparison of the measurements of heavy metal concentration in soil using two methods for adding soil components into solution and different laboratory methods and types of measuring equipment. Additionally, the article includes a discussion of the importance of methodology. We believe that the conclusions may help to better understand how sample preparation and measurement methods applied may influence the results obtained.

The aim of the study was to analyze the impact of the COVID-19 pandemic on water consumption in tourist destinations. The city of Ostróda, located in north-eastern Poland in the Warmian-Masurian Province, was selected as the subject of the study. The data for the analysis was obtained from Przedsiębiorstwo Wodociągów i Kanalizacji Ostróda sp. z o.o. (Ostróda Water Supply and Sewerage Company). It included monthly water consumption in individual consumer groups and the hourly volume of water pumped into the network. The following periods were subjected to a comparative analysis: before (1 January 2018–31 March 2020), during the pandemic (1 April 2020–31 May 2022), and in the phase of easing restrictions (1 June 2022–31 December 2023). Water consumption was analyzed using parametric and non-parametric tests in individual customer groups, with a distinction made between the following sectors: households, non-production services, food industry, wholesale, production services, and other industries. In addition, an analysis was carried out of the impact of the COVID-19 pandemic on the daily and hourly unevenness of water supply to the water supply network in individual research periods. Based on the analyses carried out, it was found that the impact of the pandemic on total water consumption in the water supply system was insignificant, but varied greatly among individual consumer groups. However, the pandemic did not have a major impact on the values of the coefficients of unevenness of water supply to the network or on the volume and times of peak supply. Based on the analyses, it was found that the COVID-19 pandemic did not significantly affect water consumption in households, but significant changes were observed in the industrial and service sectors (η² = 0.26–0.37; ε² = 0.36–0.52). There was no significant impact of the pandemic on the values of water supply irregularity coefficients or the size and hours of water supply peaks.

Cel pracy: Celem badań było określenie wpływu opadów atmosferycznych na zmienność odpływu ścieków z oczyszczalni w Łęgu, obsługującej aglomerację Połaniec. Materiał i metody: Analizie poddano średnie dobowe wartości odpływu ścieków, a także określono podstawowe statystyki opisowe, dotyczące charakterystyki ilościowej odpływu ścieków z oczyszczalni w Łęgu w latach 2016-2017. Pozyskane ze stacji meteorologicznej w Chorzelowie, oddalonej od oczyszczalni w Łęgu o 14,5 km, dane opadowe posłużyły do określenia średnich dobowych sum opadów atmosferycznych oraz liczby dni z opadem. Dane dotyczące dobowych opadów atmosferycznych pogrupowano względem wielkości, a następnie porównano ze średnimi dobowymi odpływami ścieków z oczyszczalni. Wyniki i wnioski: Na podstawie przeprowadzonej analizy statystycznej wykazano istotny wpływ opadów atmosferycznych na zwiększony odpływ ścieków z oczyszczalni. Na przestrzeni lat zauważono tendencję wzrostową temperatury powietrza oraz mniejsze sumy opadów czyli cieplejsze i bardziej suche lata.

The treatment of domestic wastewater remains a significant environmental challenge, particularly in rural areas where the construction of sewer systems is often not economically viable. Vertical-flow filters offer an alternative, but traditional filter media are prone to clogging, which justifies the search for new waste-based fillers. The aim of this study was to evaluate the potential of synthetic waste wool as a filter medium and biofilm carrier in vertical filters for domestic wastewater treatment, with particular emphasis on the effects of active bed height and hydraulic loading rate. Experimental models were used to assess the influence of these parameters on treatment performance. High removal efficiencies of organic pollutants and suspended solids were achieved. The filter with an active bed height of 0.9 m that operated at a hydraulic loading rate of 80 dm³·m⁻²·d⁻¹ achieved removal efficiencies of 93.06–97.65% for BOD₅, 86.53–94.20% for COD, 62.69–87.53% for TSS, and 65.73–94.31% for NH₄⁺-N. The most favorable treatment results were obtained for a greater bed depth and lower hydraulic load values. An increase in hydraulic load resulted in a deterioration of the quality of the treated wastewater. The results obtained indicate that waste synthetic wool can serve as a promising filtration material in decentralized wastewater treatment systems, aligning with the principles of the circular economy and the sustainable development of environmental technologies.