Origin, distribution, and perspective health benefits of particulate matter in the air of underground salt mine: a case study from Bochnia, Poland

Halophilic and Non-Halophilic Microbial Communities in Relation to Physico-Chemical Characteristics of Salt Mine Air

Salt mines are often used for halotherapy against lung and skin diseases. In addition to salt, they also contain various types of microorganisms, which remain poorly characterised. Here, we examined culturable halophilic and non-halophilic microbial populations in relation to the physico-chemical characteristics in the air of four different sites of the Bochnia Salt Mine, a popular halotherapy resort in Southern Poland. At the mine entrance, the temperature was highest (20.8°C) and decreased with increasing distance from the entrance (15.5°C at 2671 m from entrance), while humidity increased from 55.9% to 77.0%, as did the NaCl concentration. At the entrance, non-halophilic microorganisms prevailed, especially fungi that grew at 21°C. Halophiles gradually dominated with distance from the entrance, including halophilic archaea that grew at 28°C or 37°C on medium containing 15%, 20%, or 25% NaCl. Seven halophilic archaeal species were identified by 16S rRNA gene sequencing. The frequency of non-halophiles was inversely related to distance from the entrance, humidity, and presence of ions, while the reverse was seen for halophiles. An exception was the site used for halotherapy, where non-halophilic bacteria dominated. Thus, natural salt mines contain a wide variety of non-halophilic and halophilic microorganisms, including archaea, which may contribute to the halotherapeutic effects.

Geogenic characterisation of airborne particles from the former Regoufe mining area

Mining operations contribute to higher environmental contaminant levels, such as particulate matter (PM) hosting potentially toxic elements (PTE). This study aimed to comprehensively characterise atmospheric PM in an environment impacted by former tungsten-tin mining exploration at Regoufe mine (Arouca, Portugal). Although this is a deactivated mine, its location near population clusters and integration into a Geopark belonging to the "World Geoparks Network" with frequent presence of hikers highlight the importance of air quality monitoring to keep its Geopark classification. A seasonal and cumulative sampling approach was used, with samples collected over a seasonal period, between April 2022 and April 2023, through passive sampling, wet and dry sedimentation, and air mass filtration. All samples were analysed using SEM-EDS for detailed imaging. Samples from wet deposition and filtration were also analysed with ICP-MS to determine the concentration of the inorganic elements. The PTE determined in the atmospheric particulate matter of the studied area occurs in variable concentrations as a function of the sampling period. The mineralogy of the PM sampled includes Sn- and W-minerals, pyrite, quartz, phosphates, sulfates, and As-oxides. These materials are typical in the site's soils, suggesting their resuspension by the wind and transported to nearby areas. Angular to sub-angular dense particles indicate limited transportation, depositing closer to their emission source. The smaller particles (<25 μm) tended to be angular with sharp edges. Our results emphasise the importance of monitoring potentially toxic elements in atmospheric particulate matter of abandoned mining areas for developing mitigation strategies to reduce impacts on human health and surrounding environments.

Integrated smart dust monitoring and prediction system for surface mine sites using IoT and machine learning techniques

The mining industry confronts significant challenges in mitigating airborne particulate matter (PM) pollution, necessitating innovative approaches for effective monitoring and prediction. This research focuses on the design and development of an Internet of Things (IoT)-based real-time monitoring system tailored for PM pollutants in surface mines, specifically PM 1.0, PM 2.5, PM 4.0, and PM 10.0. The novelty of this work lies in the integration of IoT technology for real-time measurement and the application of machine learning (ML) techniques for accurate prediction based on recorded dust pollutants data. The study's findings indicate that PM 1.0 pollutants exhibited the highest concentration in the atmosphere of the ball clay surface mine sites, with the stockyard site registering the maximum levels of PM pollutants (28.45 µg/m3, 27.89 µg/m3, 26.17 µg/m3, and 27.24 µg/m3, respectively) due to the dry nature of clay materials. Additionally, the research establishes four ML models-Decision Tree (DT), Gradient Boosting Regression (GBR), Random Forest (RF), and Linear Regression (LR)-for predicting PM pollutant concentrations. Notably, Random Forest demonstrates superior performance with the lowest Mean Absolute Error (MAE) and Root Mean Squared Error (RMSE) at 1.079 and 1.497, respectively. This comprehensive solution, combining IoT-based monitoring and ML-based prediction, contributes to sustainable mining practices, safeguarding worker well-being, and preserving the environment.

Draft genomes of halophilic Archaea strains isolated from brines of the Carpathian Foreland, Poland

Halophilic Archaea are a unique group of microorganisms living in saline environments. They constitute a complex group whose biodiversity has not been thoroughly studied. Here, we report three draft genomes of halophilic Archaea isolated from brines, representing the genera of Halorubrum, Halopenitus, and Haloarcula. Two of these strains, Boch-26 and POP-27, were identified as members of the genera Halorubrum and Halopenitus, respectively. However, they could not be assigned to any known species because of the excessive difference in genome sequences between these strains and any other described genomes. In contrast, the third strain, Boch-26, was identified as Haloarcula hispanica. Genome lengths of these isolates ranged from 2.7 Mbp to 3.0 Mbp, and GC content was in the 63.77%-68.77% range. Moreover, functional analysis revealed biosynthetic gene clusters (BGCs) related to terpenes production in all analysed genomes and one BGC for RRE (RiPP recognition element)-dependent RiPP (post-translationally modified peptides) biosynthesis. Moreover, the obtained results enhanced the knowledge about the salt mines microbiota biodiversity as a poorly explored environment so far.

A first insight into the Polish Bochnia Salt Mine metagenome

The Bochnia Salt Mine is one of the oldest mines in Europe. It was established in the thirteenth century, and actively operated until 1990. The mine has been placed on the UNESCO World Heritage List. Previous research describing Polish salt mines has been focused on bioaerosol characteristics and the identification of microorganisms potentially important for human health. The use of Polish salt mines as inhalation chambers for patients of health resorts has also been investigated. Nevertheless, the biodiversity of salt mines associated with biotechnological potential has not been well characterized. The present study paper examines the biodiversity of microorganisms in the Bochnia Salt Mine based on 16S rRNA gene and shotgun sequencing. Biodiversity studies revealed a significantly higher relative abundance of Chlamydiae at the first level of the mine (3.5%) compared to the other levels (< 0.1%). Patescibacteria microorganisms constituted a high percentage (21.6%) in the sample from site RA6. Shotgun sequencing identified 16 unique metagenome-assembled genomes (MAGs). Although one was identified as Halobacterium bonnevillei, the others have not yet been assigned to any species; it is possible that these species may be undescribed. Preliminary analyses of the biotechnological and pharmaceutical potential of microorganisms inhabiting the mine were also performed, and the biosynthetic gene cluster (BGC) profiles and antimicrobial peptide (AMP) coding genes in individual samples were characterized. Hundreds of BGCs and dozens of AMP coding genes were identified in metagenomes. Our findings indicate that Polish salt mines are promising sites for further research aimed at identifying microorganisms that are producers of potentially important substances with biotechnological and pharmaceutical applications.

PM2.5 exceedances and source appointment as inputs for an early warning system

Between June 2018 and April 2019, a sampling campaign was carried out to collect PM2.5, monitoring meteorological parameters and anthropogenic events in the Sartenejas Valley, Venezuela. We develop a logistic model for PM2.5 exceedances (≥ 12.5 µg m-3). Source appointment was done using elemental composition and morphology of PM by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). A proposal of an early warning system (EWS) for PM pollution episodes is presented. The logistic model has a holistic success rate of 94%, with forest fires and motor vehicle flows as significant variables. Source appointment analysis by occurrence of events showed that samples with higher concentrations of PM had carbon-rich particles and traces of K associated with biomass burning, as well as aluminosilicates and metallic elements associated with resuspension of soil dust by motor-vehicles. Quantitative source appointment analysis showed that soil dust, garbage burning/marine aerosols and wildfires are three majority sources of PM. An EWS for PM pollution episodes around the Sartenejas Valley is proposed considering the variables and elements mentioned.

Analysis of Environmental and Pathogenic Bacteria Attached to Aerosol Particles Size-Separated with a Metal Mesh Device

Metal mesh devices (MMDs) are novel materials that enable the precise separation of particles by size. Structurally, MMDs consist of a periodic arrangement of square apertures of characteristic shapes and sizes on a thin nickel membrane. The present study describes the separation of aerosol particles using palm-top-size collection devices equipped with three types of MMDs differing in pore size. Aerosols were collected at a farm located in the suburbs of Nairobi, Kenya; aerosol particles were isolated, and pathogenic bacteria were identified in this microflora by next-generation sequencing analysis. The composition of the microflora in aerosol particles was found to depend on particle size. Gene fragments were obtained from the collected aerosols by PCR using primers specific for the genus Mycobacterium. This analysis showed that Mycobacterium obuense, a non-tuberculous species of mycobacteria that causes lung diseases, was present in these aerosols. These findings showed that application of this MMD analytical protocol to aerosol particles can facilitate the investigation of airborne pathogenic bacteria.

Properties of Particulate Matter in the Air of the Wieliczka Salt Mine and Related Health Benefits for Tourists

This study aimed to evaluate the mass concentration of size-resolved (PM1, PM2.5, PM4, PM10, PM100) particulate matter (PM) in the Wieliczka Salt Mine located in southern Poland, compare them with the concentrations of the same PM fractions in the atmospheric air, and estimate the dose of dry salt aerosol inhaled by the mine visitors. Measurements were conducted for 2 h a day, simultaneously inside (tourist route, passage to the health resort, health resort) and outside the mine (duty-room), for three days in the summer of 2017 using DustTrak DRX devices (optical method). The highest average PM concentrations were recorded on the tourist route (54-81 µg/m3), while the lowest was in the passage to the health resort (49-62 µg/m3). At the same time, the mean outdoor PM concentrations were 14-20 µg/m3. Fine particles constituting the majority of PM mass (68-80%) in the mine originated from internal sources, while the presence of coarse particles was associated with tourist traffic. High PM deposition factors in the respiratory tract of children and adults estimated for particular mine chambers (0.58-0.70), the predominance of respirable particles in PM mass, and the high content of NaCl in PM composition indicate high health benefits for mine visitors.

Possible sources of ambient PM10 inside Jadavpur University Campus, Kolkata

High concentration of particulates in the university and research institutional campus can affect cognitive performance of students and researchers. However, studies on ambient particulate concentration in the campus of universities or research institutes are scarce. The ambient concentration of PM₁₀ was measured in the campus of Jadavpur University, Kolkata, during two different seasons (S1: Post-monsoon; S2: Winter) to identify major sources of pollutant here. Significant seasonal variation of ambient PM₁₀ was recorded in the campus. The average ambient PM₁₀ concentration was recorded higher in S2 compared to S1 of the study period. Morphological characteristics of PM₁₀ during the study period suggest that the roundness of particles was in the range of 0.66 to 0.68, whilst the mean spherical diameter suggests most of the PM₁₀ particles were < 2.5 μ diameter. Based on factorial analysis, three factors were generated which includes factor 1: soil, building material and coal burning particles (53.76% of the variance); factor 2: particles from coal combustion (29.89% of the variance) and factor 3: particles from transport emission (16.33% of the variance). The study suggests that it is important to stop burning coal, reduce vehicular emission and reduce road dust resuspension around the campus to maintain the ambient PM₁₀ concentration within the university campus during the post-monsoon and winter months.

Mineralogical and Chemical Tracing of Dust Variation in an Underground Historic Salt Mine

The aim of this study was to investigate the causes of the evolution of atmospheric dust composition in an open-to-public subterranean site (UNESCO-recognized historic mine) at increasing distances from the air intake. The role of the components imported with atmospheric air from the surface was compared with natural and anthropogenic sources of dust from inside the mine. Samples of deposited dust were directly collected from flat surfaces at 11 carefully selected sites. The morphological, mineralogical, and chemical characteristics were obtained using scanning electron microscopy (SEM), X-ray diffraction (XRD), and inductively coupled plasma spectroscopy (ICP). The study showed that the air in the underground salt mine was free of pollutants present in the ambient air on the surface. Most of the components sucked into the mine by the ventilation system from the surface (regular dust, particulate matter, gaseous pollutants, biogenic particles, etc.) underwent quick and instantaneous sedimentation in the close vicinity of the air inlet to the mine. The dust settled in the mine interior primarily consisted of natural geogenic particles, locally derived from the weathering of the host rock (halite, anhydrite, and aluminosilicates). This was confirmed by low values of enrichment factors (EF) calculated for minor and trace elements. Only one site, due to the tourist railroad and the associated local intensive tourist traffic, represented the anthropogenic sources of elevated concentrations of ferruginous particles and accompanied metals (P, Cr, Mn, Co, Ni, Cu, As, Mo, Cd, Sn, Sb, Pb, and W). The gravitational deposition of pollutants from these sources limits the effects of the emissions to the local range. The used methodology and the results are universal and might also apply to other mines, caves, or underground installations used for museums, tourists, or speleotherapeutic purposes.