This study aimed to assess the pollution and potential ecological risk of seven heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in the sewage sludge collected from a wastewater treatment plant (WWTP), located in the most industrialized region of Poland (Silesian Voivodeship). The concentrations of heavy metals were determined using inductively coupled plasma optical spectrometry (ICP-OES) and cold vapor atomic absorption spectrometry (CVAAS). The chemical forms (chemical speciation) of heavy metals were determined using the three-step chemical sequential extraction procedure, developed by the Community Bureau of Reference (BCR). To assess the pollution level and potential ecological risk, the following indices were used: Geoaccumulation Index (I_geo), Potential Ecological Risk Factor (ER), Individual Contamination Factor (ICF), modified Risk Assessment Code (RAC_m), and Ecological Risk Factor (ERF)—the author’s index. Sludge samples were collected at successive stages of processing. The results revealed that the activated sludge process and sludge thickening have a significant impact on heavy metal distribution, while anaerobic digestion and dehydration decrease their mobility. The most dominant metals in the sludge samples were Zn and Cu. However, the content of heavy metals in sewage sludge did not exceed the permissible standards for agricultural purposes. The concentrations of heavy metals bound to the immobile fractions exhibited higher concentrations, compared to those bound to mobile fractions (except Zn). The values of the total indices indicated that sludge samples were moderately to highly contaminated with Zn, Hg, Cd, Cu, and Pb, of which only Hg, Cd, and Cu posed a potential ecological risk, while according to the speciation indices, sludge samples were moderately to very highly polluted with Zn, Cu, Cd, Cr, and Ni, of which Zn, Ni, and Cd were environmentally hazardous. The obtained results proved that assessment of the pollution level and potential ecological risk of heavy metals in sewage sludge requires knowledge on both their total concentrations and their chemical forms. Such an approach will help prevent secondary pollution of soils with heavy metals, which may influence the reduction of health risks associated with the consumption of plants characterized by a high metal content.

The analysis of heavy metal concentrations and forms in sewage sludge constitutes an important issue in terms of both health and environmental hazards the metals pose. The total heavy metals concentration enables only the assessment of its contamination. Hence the knowledge of chemical forms is required to determine their environmental mobility and sludge final disposal. Heavy metals speciation was studied by using four-stage sequential extraction BCR (Community Bureau of Reference). This study was aimed at determining the total concentration of selected heavy metals (Zn, Cu, Ni, Pb, Cd, Cr and Hg) and their chemical forms (except for Hg) in sludge collected at different stages of its processing at two municipal Wastewater Treatment Plants in southern Poland. Metals contents in sludge samples were determined by using flame atomic absorption spectrometry (FAAS) and electrothermal atomic absorption spectrometry (ETAAS). This study shows that Zn and Cu appeared to be the most abundant in sludge, while Cd and Hg were in the lowest concentrations. The sewage sludge revealed the domination of immobile fractions over the mobile ones. The oxidizable and residual forms were dominant for all the heavy metals. There was also a significant difference in metals speciation between sludges of different origin which was probably due to differences in wastewater composition and processes occurring in biological stage of wastewater treatment. The results indicate a negligible capability of metals to migrate from sludge into the environment. Our research revealed a significant impact of thickening, stabilization and hygienization on the distribution of heavy metals in sludge and their mobility.

The present study aimed to demonstrate that identification of the chemical forms of heavy metals in sewage sludge produced in municipal Wastewater Treatment Plants (WWTPs) is a critical element of ecological risk assessment, especially in terms of its agricultural or natural use. The concentrations of seven heavy metals (Cd, Cr, Cu, Ni, Pb, Zn and Hg) were determined using inductively coupled plasma optical spectrometry (ICP-OES) and cold vapor atomic absorption spectrometry (CV-AAS). The chemical forms of heavy metals were analyzed in accordance with the sequential extraction method proposed by the Community Bureau of Reference (BCR). Sludge samples were collected at the five municipal WWTPs located in the largest industrial area in the country, i.e., the Upper Silesian Industrial Region (southern Poland, central Europe). The ecological risk was assessed by calculating the Potential Ecological Risk Factor (ER), Risk Index (RI), Risk Assessment Code (RAC), Individual Contamination Factor (ICF), Global Risk Index (GRI) as well as the author’s indices, i.e., Individual Ecological Risk (IER) and Global Ecological Risk (GER). To demonstrate the differences between the level of ecological risk posed by the different heavy metals, sludge samples were collected at two specific points of the processing line. Considering the chemical forms of heavy metals, the highest ecological risk was posed by Zn, Cd and Ni, while in the case of their total concentrations, by Cd and Hg. The obtained results confirm that quantitative determination of the total content of heavy metals in sewage sludge is not a sufficient criterion in assessment of the ecological risk that these elements pose to the natural environment and living organisms. Moreover, multivariate statistical analysis revealed a significant correlation between the concentrations of heavy metals, which indicates that they plausibly originate from the same source of pollution.

Study was aimed to assess the potential ecological risk of nine metals (Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) and one metalloid (As) in bottom sediments of the Dzierżno Duże Reservoir located in the key anthropogenic “hot spot” area—Upper Silesian Industrial Region (Poland). Sediments were collected in seven sampling sites, along the main axis of a reservoir. Statistical analysis revealed a significant correlation (p < 0.05) between the potentially toxic elements, which indicated that they plausibly originate from the same source of contamination or have a similar accumulation behavior. Several indices were used to assess ecological risk associated with examined elements, i.e., Enrichment Factor, Geoaccumulation Index, Contamination Factor, Potential Ecological Risk Factor, Probable Effect Concentration, Threshold Effect Concentration, Degree of Contamination and Risk Index. The values of analyzed indices indicate that sediments are highly to extremely highly contaminated, especially by Cd, Pb, Zn, and As, which simultaneously pose the highest ecological risk. The results of Cluster Analysis (CA) and Principal Component Analysis (PCA) indicate that Cd, Cr, Fe, Ni, Pb, Zn, and As in the bottom sediments are most likely of anthropogenic origin, while Mn rather from natural sources. The obtained results confirm the usefulness of different indices in assessing the ecological condition of water bodies and prove that the problem of toxic elements contamination in bottom sediments of the Dzierżno Duże Reservoir poses a serious environmental threat.

This study aimed to assess the potential risks posed by heavy metals in sewage sludge (SS) produced by municipal wastewater treatment plants (WWTPs) in the most industrialized region in Poland, the Silesian Voivodeship. The ecological risk was assessed using three indices: the Geoaccumulation Index (I_geo), Potential Ecological Risk Factor (ER), and Risk Assessment Code (RAC), while the health risk was estimated by using carcinogenic and non-carcinogenic risk indices. The average concentrations of metals in the sludge samples were determined revealing that Zn was the predominant element, whereas Cd and Hg were present in the lowest concentrations. The study showed that the processes used in wastewater treatment plants influenced the overall metal content and chemical speciation. According to I_geo values, the dewatered sludge samples exhibited higher contamination levels of Cd and Zn, while Cu and Pb were upon to a lesser extent. The ER values suggest that Cd and Hg present the highest ecological risk. Considering the chemical forms and RAC values, Ni (26.8–37.2%) and Zn (19.8–27.0%) were identified to cause the most significant risks. The non-carcinogenic risk for adults and children was below acceptable levels. However, the carcinogenic risk associated with Ni (WWTP1) for both demographic groups and Cr and Cd (WWTP2), specifically for children, exceeded the acceptable threshold. Ingestion was the primary route of exposure. Although the dewatered SS met the standards for agricultural use, there is still a risk of secondary pollution to the environment and possible adverse health effects.

Aerosol water is a master component of atmospheric aerosols and a medium that enables all aqueous-phase reactions occurring in the atmosphere. This integral chemical compound of suspended aerosol particles (PM) has become one of the hottest issues in recent years. To look for scientific productivity in the area of PM-bound water research a bibliometric analysis was performed. Most actual literature regarding aerosol and particulate bound water and implications of the research in this field was downloaded from WOS database using 1996–2018 timespan. Different bibliographic statistics were used to get a general profile of leading authorships, institutions, countries and mainstream journals providing most highly cited articles in the field. Using the CiteSpace software it was possible to identify past trends and possible future directions in measuring aerosol bound water. The search terms used in the database were {“aerosol” AND “water” OR “chemical mass balance”} AND {“particulate matter” OR “PM-bound water” OR “hygroscopic”}. The answers to the following questions were found: which authors, countries, institutions and aerosol journals to the greatest degree influenced PM-bound water research?. The network of co-occurring noun phrases was extracted from the set of publications, followed by co-citation analysis. The network was also clustered by top terms which gave a clear picture of topics most often undertaken. Finally the publication meeting eligibility criteria were looked for chemical compounds most frequently determined in PM-bound water research, which help to indicate works where quantitative assessment of PM-bound water was performed. Obtained results indicate that the paper with the greatest citation burst was Tang and Munkelwitz (J Geophys Res Atmos 99(D9):18801–18808, 1994). The largest number of articles in this specific field was published in Atmospheric Chemistry and Physics. An absolute leader in the quantity of publications among all research institutions is National Aeronautics Space Administration NASA. Meteorology and Atmospheric sciences is the discipline most occupied by highly cited journals in this field. Clustering results indicate that the research has mainly focused on hygroscopic measurement of aerosol, hygroscopic growth of particles; aerosol liquid water, and hygroscopic behavior. Most articles rather points PM-bound water as an artifact in organic carbon and ions measurements without detailed analysis of its contents or probable origin. The number of publications in each cluster of the build network is relatively high, which indicate that scholars have formed a rather consistent studies in the theme of aerosol-bound water. Despite a relevant role played by aerosol-bound water in atmospheric processes a quantitative description of its contents is rather rarely found in the literature (with the total number of only 23 papers concerning PM-bound water contents). In terms of yield, USA, China and Italy ranked highest, playing a propelling role in the research on PM-bound water. Future trends in PM-bound water research should be directed to a quantitative measurements of its contents; source apportionment, chemical composition of PM—modulating its hygroscopicity and therefore cloud formation processes, and the assessment of artefacts influencing the quality of PM-bound water measurements. Those areas should be especially developed in future studies and scientific projects concerning atmospheric water.