Microplastic pollution in show cave sediments: First evidence and detection technique

The problem of anthropogenic microfibres in karst systems: Assessment of water and submerged sediments

A new worrying micropollutant threathens natural environments: the microfibres (MFs). Natural, regenerated and synthetic MFs have been detected in different environments, as well as in organisms. While synthetic MFs are generally detected in microplastic analyses, natural and regenerated MFs are not taken into account, or are wrongly considered plastics. They are generally considered biodegradable even if their degradation processes in ecosystems are poorly known. Their potential faster degradation could release toxic compounds, and their characteristics could led to a long-term accumulation in the environment. Understanding their dangerousness and the possible impact they could have on ecosystems is fundamental for environment conservation. We collected and investigated water and submerged sediment samples in different caves and springs of the Classical Karst Region (NE Italy), rich in protected habitats and species. MFs were analysed via microscopy and spectroscopy. MFs were found in all samples, highlighting pollution in surface and subterranean habitats of the karst system. MF concentration was higher in submerged sediments respect to waters, highlighting an accumulation of MFs over time. Big microfibres were less abundant, and MF amount increased with the decrease in the considered size. More than 80% of fibres were fluorescent under UV light. Fluorescent MFs were especially transparent, while non-fluorescent ones were mainly black and blue. Most MFs were cellulosic, and synthetic MFs represent only 15-22%, highlighting a significant gap between the MF composition detected in natural environments and the global production of synthetic textiles in recent times. Synthetic MFs were more abundant in waters. Our results improve the knowledge on micropollutants in karst environments, laying the foundations for future research. MF pollution monitoring in karst areas must become a priority for species protection, habitat conservation, and waters management, improving analyses on a larger number of aquatic environments, taking into account the ecological connections between surface and subterranean habitats.

Primary Microplastics in the Ecosystem: Ecological Effects, Risks, and Comprehensive Perspectives on Toxicology and Detection Methods

Recent discoveries of microplastics in cities, suburbs, and even remote locations, far from microplastic source regions, have raised the possibility of long-distance transmission of microplastics in many ecosystems. A little is known scientifically about the threat that it posed to the environment by microplastics. The problem's apparent size necessitates the rapid development of reliable scientific advice regarding the ecological risks of microplastics. These concerns are brought on by the lack of consistent sample and identification techniques, as well as the limited physical analysis and understanding of microplastic pollution. This review provides insight regarding some unaddressed issues about the occurrence, fate, movement, and impact of microplastics, in general, with special emphasis on primary microplastics. The approaches taken in the earlier investigations have been analyzed and different recommendations for future research have been suggested.

Natural and anthropogenic impact on the microclimate and particulate matter in the UNESCO show cave

Particulate matter concentrations (PM10, PM2.5, PM1) and microclimatic parameters (air temperature, CO2) were monitored in the Škocjan Caves (Slovenia). The effects of tourist visits on the PM concentrations and the cave's microclimate are immediate and direct, but these values normalise relatively quickly. The results showed seasonal, diurnal, and spatial differences in all parameters studied. Due to the higher number of visitors, their influence on the cave's microclimate and PM10 and PM2.5 concentrations is greater in summer than in winter. The measured PM1 levels depend on the ventilation in the cave, as air transport plays an important role in their introduction into the cave. PM consists of minerals of natural origin resulting from the re-suspension of cave sediments due to strong air currents generated by the opening of the doors to tourists and their walks. The second most common influence is the anthropogenic phases originating from maintenance work in the cave, electronic devices, cave lighting and emissions from outside the cave (aerosols from the polluted Reka River, industry, traffic, gypsum waste disposal). In order to upgrade the sustainable use of the UNESCO-listed Škocjan Caves for tourism, we propose regular monitoring of PM and a detailed characterization of individual PMs and their sources, in addition to monitoring of the cave's microclimate and biology.

Microplastic pollution calls for urgent investigations in stygobiont habitats: A case study from Classical karst

Microplastic pollution in karst systems is still poorly studied, despite the presence of protected species and habitats, and important water reserves. Vulnerable key species hosted in these habitats could consume or assimilate microplastics, which can irreversibly damage management efforts, and thus ecosystems functionality. This can be particularly true for subterranean water habitats where microplastic pollution effects on wildlife management programs are not considered. The aim of this study is to provide a case study from the Classical Karst Region, which hosts peculiar habitats and key species protected at European level, such as the olm Proteus anguinus. As this area has been deeply exploited and modified over time, and is adjacent to highways, roads and railways, which could contribute to pollution within the karst system, threatening the ecosystems, it provides a perfect model system. In this study we collected and investigated water and sediment samples from aquatic environments of surface and subterranean habitats hosting several subterranean environment-adapted organisms. Examined particles were counted and characterized by size, color and shape via visual identification under a microscope, with and without UV light. Furthermore, spectroscopic analyses were carried out in order to identify microplastics typology. Microplastics were found in all examined habitats. In water, microplastics concentration ranged from 37 to 86 items/L, in sediments from 776 to 2064 items/kg. Fibre-shape was the main present, followed by fragments and beads, suggesting multiple sources of pollution, especially textile products. Most of the particles were fluorescent under UV light and were mainly transparent, while not-fluorescent ones were especially black, blue or brown. Samples contained especially polyesters and copolymers. These results highlight intense MP pollution in karst areas, with significant impacts on water quality, and potential effects on subterranean environment-dwelling species. We stress the importance of monitoring pollution in these critical environments for biodiversity and habitat conservation: monitoring in karst areas must become a priority for habitat and species protection, and water resources management, improving analyses on a larger number of aquatic surface and subterranean habitats.

Sequestration and export of microplastics in urban river sediments

In rivers, riverbeds are considered to have dual properties as a short-term sink and a source of further mobilization for microplastics. To better understand the sources, storage, and fate of microplastics in river systems, this study quantified the formation of microplastic hotspots in riverbeds and seasonal variations in microplastic inventories in riverbeds, especially for small-sized microplastics (<330 µm), with a fluorescence-based protocol. This study provides first-hand measured evidence for the sequestration of microplastics in the riverbed under low-flow conditions and its export from the riverbed under high-flow conditions. The results show that riverbeds in urban areas are still hotspots for microplastic pollution and that high inputs of urban microplastics control microplastic load in its downstream areas. Seasonal rainfall exported 34.86 % (equivalent to 4.34 × 1011 items/8.57 t) of microplastic pollution from the riverbed, and its removal capacity may be related to the rainfall intensity. Wider riverbeds are conducive to the formation of microplastic hotspots due to the flow slow down. Most importantly, rainfall-driven scouring of the riverbed can enhance the pollution of small-sized microplastics in the riverbed, especially the smallest-size microplastics (<100 µm). Therefore, this study not only contributes reliable information about the sequestration and export of microplastics in the riverbed, but also provides a possible mechanism to explain the lack of small-sized microplastics (<330 µm) in the ocean.

Floods enhance the abundance and diversity of anthropogenic microparticles (including microplastics and treated cellulose) transported through karst systems

Microplastics (plastics <5 mm) are emerging contaminants that have been detected in virtually all environments. While microplastic research in terrestrial surface waters has been proliferating, microplastic contamination in subsurface environments remains understudied. Karst terrains may be particularly susceptible to microplastic pollution because the presence of large dissolution openings allows fast transport of water through these systems, facilitating the introduction of surface contaminants into subsurface habitats. Furthermore, few studies address the prevalence and movement of microparticles composed of semisynthetic and modified natural materials, despite their known ecotoxicity. Our study therefore aims to identify anthropogenic (i.e., synthetic, semisynthetic, and treated natural) microparticle extent, sourcing, and transport in subsurface karst environments. To do so, we examined a cave spring under variable flow conditions, finding that anthropogenic microparticles were present in all samples and were most frequently fibrous and clear. The mean anthropogenic microparticle concentration during baseflow was 9.2 counts/L but increased up to 81.3 counts/L during floods, indicating their enhanced mobilization when relatively dilute, acidic, and sediment-rich event water entered the cave. These results suggest that anthropogenic microparticles may originate from surface recharge or sediment resuspension within the cave. When we analyzed a subset of microparticles with Fourier transform infrared spectroscopy (FTIR), we found that cellulose of known (i.e., dyed) and suspected (i.e., clear) anthropogenic origin was the most abundant material type. We nevertheless confirmed the presence of microplastics in the cave stream under all flow conditions, with the most common polymer being polyethylene. Both the concentrations and relative fractions of microplastics were higher during floods compared to baseflow, indicating their increased transport during high flow events. We also observed that microplastic polymer types diversified as discharge increased. Our study gives new insight into how anthropogenic microparticle contamination is transported through karst landscapes that can help inform debris mitigation strategies to protect ecosystems and water resources.

Adherence of polystyrene microspheres on cave sediment: implications for organic contaminants and microplastics in karst systems

Interactions of karst aquifer sediments with organic contaminants or microplastics (MPs) have received relatively little attention even though the susceptibility of karst aquifers to contamination and their ability to store and transport sediment is well documented. Studies using polystyrene microspheres as surrogate tracers for bacteria transport in karst systems have generally observed low recovery of microspheres and attributed this to microsphere adsorption onto aquifer sediments. In addition to being used as surrogate tracer for bacteria, microspheres have the potential to be used as surrogate material for organic contaminants and MPs. Using cave sediments as a proxy for karst aquifer sediments, the adherence of two types of microspheres (carboxylated and nonfunctionalized) was measured in three different types of solutions: deionized water, a calcium carbonate solution, and a karst spring water. Both types of microspheres adhered to the sediments; the most influential factor in adherence was solution type not microsphere type. Average adherence ranged from 51%-94% with average adsorption coefficients (KD) ranging from 11.8-442. Average estimated organic-carbon water partition coefficients (KOC) and retardation factors (RF) ranged from 1.64×103 - 6.13×104 and 6.20×101 - 2.29 × 103, respectively. KD, KOC, and RF were an order of magnitude higher in the karst water than in DI or CaCO3 solution. The results illustrate the importance of sediment interactions with potential organic or MP contaminants in karst systems.

Exploring the vertical transport of microplastics in subsurface environments: Lab-scale experiments and field evidence

Microplastics (MPs) defined as smaller 5 mm plastic particles have received increasing attention due to their global occurrence and potential toxicity. This study investigated the effects of environmental factors (rainfall intensity, 13 and 29 mm/h) and MP characteristics (morphology (fiber, flake, and film), polymer type (polypropylene (PP), polyethylene terephthalate (PET), and polystyrene (PS)) and size (100-300, 300-500, and 500-1000 μm)) on the vertical transport of MP in unsaturated soil conditions using lab-scale column experiments. Additionally, the occurrence and characteristics of MP detected in soil/sediment (total 13 samples) and groundwater samples (total 6 samples) were explored in the field study. Laboratory-scale column experiments revealed that heavy rainfall intensity (29 mm/h) increased the degree of MP vertical transport in unsaturated soil conditions and MP fibers showed the greatest vertical mobility among the various morphologies of MPs assessed. For the polymer type and size, the lighter PP polymer or the larger size of MP (500-1000 μm) showed higher mobility. In the field study, a statistical difference in MP abundance was observed depending on the population density and degree of urban development in both soil and groundwater samples. Comparing to the two different types of environmental media samples obtained from the same site, there was a significant difference in the composition of polymer types present while statistically no difference in MP abundance was observed between the two media samples (i.e., soil or sediment and groundwater). In addition, MP fibers and polyethylene (PE) were predominantly detected in our two study areas. These results suggest that various types of MP can pass through the unsaturated zone by water infiltration, even if it takes a long time to reach groundwater. Overall, we found that the degree of vertical transport of the MPs was highly sensitive to environmental conditions and MP characteristics.

Consumption of commercially sold dried fish snack "Charales" contaminated with microplastics in Mexico

Inadvertent human exposure to microplastics by the ingestion of microplastic-contaminated processed foods poses health risks and new preventative issues; nevertheless, investigations analyzing microplastic occurrences in commercially dried fish for direct human consumption are scarce. This study assessed the abundance and characteristics of microplastics in 25 commercially sold dried fish products (4 supermarkets, 3 street vendors, and 18 traditional agri-product farmers' markets) from two widely consumed and commercially important Chirostoma species (C. jordani and C. patzcuaro) in Mexico. Microplastics were detected in all the samples examined, with abundances ranging from 4.00 ± 0.94 to 55.33 ± 9.43 items g^-1. C. jordani dried fish samples had higher mean microplastic abundance (15.17 ± 5.90 items g^-1) than the C. patzcuaro dried fish samples (7.82 ± 2.90 items g^-1); nevertheless, there was no statistically significant difference in microplastic concentrations between the samples. The most prevalent type of microplastic was fiber (67.55%), followed by fragment (29.18%), film (3.00%), and sphere (0.27%). Non-colored microplastics (67.35%) predominated, while microplastic sizes varied from 24 to 1670 μm, with sizes less than 500 μm (84%) being the most common. ATR-FTIR analysis revealed polyester, acrylonitrile butadiene styrene, polyvinyl alcohol, ethylene-propylene copolymer, nylon-6 (3), cellophane, and viscose in the dried fish samples. Overall, this study's findings are the first in Latin America to demonstrate microplastic contamination in dried fish for human consumption, underscoring the need for developing countermeasures to prevent plastic pollution in fish-caught regions and reduce the risks of human exposure to these micropollutants.

Microplastics in caves: A new threat in the most famous geo-heritage in the world. Analysis and comparison of Italian show caves deposits

Microplastic pollution represent a worldwide concern, however, in karst areas is still largely unknown, especially in underground environments. Caves are the most important geological heritage worldwide, rich in speleothems, unique ecosystems custodians of important drinking water reserves, and a significant economic resource. Thank to their relatively stable environmental conditions, they can preserve information for a long time such as paleontological/archaeological remains, however, these characteristics make caves vulnerable environments too, easily damaged by climate variations and pollution. To increase the current knowledge of microplastic pollution, the deposits of different Italian show caves were investigated, improving the method for microplastic separation. Microplastic were identified and characterised using MUPL automated software, observed with and without UV light under a microscope, and verified under μFTIR-ATR, highlighting the importance of combine different methods. Microplastics were present in sediments of all examined caves, and were always greater along the tourist route (an average of 4300 items/kg) than the speleological areas (an average of 2570 items/kg). Microplastics less than 1 mm dominated the samples and the amount increased with the decrease in the size considered. Fibre-shaped dominated the samples and 74% particles was fluorescent under UV light. Analysed sediment samples contained especially polyesters and polyolefins. Our results highlight the presence of microplastic pollution in show caves, giving useful information to assess risks posed by microplastics in show caves and emphasizing the importance of pollutants monitoring in underground environments to define strategies for the conservation and management of caves and natural resources.

Human occupational exposure to microplastics: A cross-sectional study in a plastic products manufacturing plant

Microplastics are ubiquitous in the natural environment, and their potential impact on health is a key issue of concern. Investigating exposure routes in humans and other living organisms is among the major challenges of microplastics. This study aims to examine the exposure level of plastic factory staff to microplastic particles before and after work shifts through body receptors (hand and facial skin, saliva and hair) in Sirjan, southeast of Iran. Moreover, the effect of face masks, gloves, cosmetics (e.g: face powder cream, lipstick and eye makeup products) and appearance on the exposure level is investigated. In total, 19 individuals are selected during six working days. Then, the collected samples are transferred to the laboratory for filtration, extraction, identification and counting of microplastic particles. Moreover, 4802 microplastic particles (100-5000 μm in size) in strand, polyhedral and spherical shapes and color spectra of white/transparent, black, blue/green, red and purple are observed. The nature of most of the observed samples is fiber with a size ≥1000 μm. Analyzing the selected samples using micro-Raman spectroscopy indicate polyester and nylon are the main identified fibers. Hair and saliva samples have the highest and lowest number of microplastics, respectively. Using gloves and sunscreen among all the participants, wearing a scarf and hair size among women and having a beard and mustache among men could have an effective role in the exposure level to microplastics. Results of this study could reveal the exposure route to microplastic particles in the human body and highlight the importance of providing higher protection to reduce exposure.

Automated method for routine microplastic detection and quantification

Microplastics (MPs) are a heterogeneous group of solid polymers with dimensions <5 mm, which are a widespread contaminant of the environment. Their ubiquitous presence grabbed researchers' attention in the last decade, and the problem of MPs detection and quantification is currently a topic of utmost importance. Most identification and quantification protocols are still based on the visual count, which is an extremely time-consuming and error-prone task due to operator subjectivity. To address such an issue, different software analysis procedures are available, but they mainly rely either on the use of optical microscopy, covering a minimal area for each sample (mm² size), or they allow only the identification of the largest particles (>1 mm). Here, a semi-automatic innovative image processing method for quantifying and measuring microplastics on filter membrane substrates is presented and validated, comparing results with data obtained using visual counting performed by an experienced operator. The algorithm was tested with artificially generated microplastic images and samples taken from natural environments. Samples of Borgio Verezzi show cave sediment and Po River water were filtered on a glass filter membrane, and photographs were taken under 365 nm illumination, both without and with Nile Red staining. The proposed image analysis method, implemented in an easy-to-use Python script, was quite accurate and fast (about 10 s/image average processing time), showing an average deviation below 10 %, which is further reduced to about 8 % if the samples are stained with Nile Red.

First record of microplastic in the environmental matrices of a Mediterranean marine cave (Bue Marino, Sardinia, Italy)

This study investigates for the first time the presence of microplastics in sediment, water, and benthic organisms (foraminifera) of a marine cave in the Gulf of Orosei (Sardinia, Italy). Microplastics were found in all water, and sediment samples with similar shapes, sizes, and compositions; identified items were mainly fragments and fibers constituted by PVC and polyethylene. Their provenance was supposed to be predominantly from the sea than from the seasonal freshwater supplies from the karst system. Foraminiferal assemblages were mainly constituted by calcareous hyaline taxa in the outer station, while in the inner ones, the agglutinated Eggerelloides advenus was dominant. FTIR analyses on agglutinated shells identified polyethylene. Microplastic items are collected by the foraminifers and sediment grains building the shell chambers. This is the first study providing evidence that marine caves may be collectors of microplastics and that, in these habitats, microplastics enter the biotic matrix at the protist's level.

Preliminary investigations of microplastic pollution in karst systems, from surface watercourses to cave waters

Microplastic pollution in different environments has increasingly been documented in detail in recent times, but it is still poorly studied in caves and karst aquifers. To deepen the knowledge of microplastic pollution, for karst environment protection and conservation purposes, we collected and investigated different water samples from a karst area of Italy, considering connected surface and cave waters. Microplastics were extracted from water samples by filtration and subjected to organic matter removal with 15% hydrogen peroxide solution. Microplastics on filters were counted and characterised (size, colour, shape) via visual identification under a microscope, with and without UV light, exploiting fluorescence given by fluorescent whitening additives contained in plastic materials. Finally, spectroscopic analyses were carried out on 10% of the microplastics observed on each filter. The concentration of microplastics in cave waters varied from 12 to 54 items/L, with a mean value of 28 items/L. In the surface water of a tributary, it was of 23 items/L, and in the downstream, it was 29 items/L. Fibres represented the most abundant shape (95.1%) in the karst system waters, and most microplastics (82.9%) were smaller than 1 mm. The majority of the microplastics were fluorescent under UV light (84.8%), and most fluorescent particles were transparent (46%). However, black microplastics (68%) were more common among the non-fluorescent ones. Polyethylene (51.7%) was the main type of microplastics found in the karst system waters. Our results show the presence of microplastics in karst systems and provide useful information for future research. Karst aquifers are open systems, subjected to possible contamination by surface pollutants. Microplastics in karst systems can be consumed by animals, damage ecosystems and contaminate water resources; surface karst areas and underground environments should therefore be monitored and protected, especially regarding the management of water resources. To further understand the sources and transport of microplastics within a karst system, analyses on a greater range of surface and subterranean waters throughout the world are required.

Preliminary Study on the Distribution, Source, and Ecological Risk of Typical Microplastics in Karst Groundwater in Guizhou Province, China

Karst groundwater is one of the important drinking water sources in karst areas, and it has an important role in maintaining the regional ecosystem and human health. The study of microplastics (MPs) in karst groundwater has rarely been reported, and the occurrence and migration behavior of MPs under the unique environmental conditions of karst is unclear. This study selected cave groundwater and common MPs in karst areas to explore the occurrence characteristics of MPs in groundwater to clarify the factors affecting the distribution and migration of MPs. The results showed that the abundance of MPs in karst groundwater was between 2.33 and 9.50 items·L^-1, with an average abundance of 4.50 items·L^-1. The microplastic size, type, color, and chemical composition were primarily 1~5 mm, film and fiber, color and transparent, and PS and PE, respectively. The risk characterization ratio (RCR) index results indicated that 80% of the samples were at a low ecological risk level, whereas 60% of the sampling points after concentrated rainfall in June were a medium ecological risk. The study showed that rainfall events significantly changed the abundance and migration of MPs in karst groundwater. The Pearson analysis showed a positive correlation between microplastic distribution and suspended particles (SP), total organic carbon (TOC), and water velocity (WV) in water. The study indicated that strong soil erosion in karst areas may also be one of the main sources of MPs in karst groundwater, and that karst groundwater microplastic pollution is an environmental problem that should not be ignored.

Microplastic-Induced Oxidative Stress in Metolachlor-Degrading Filamentous Fungus Trichoderma harzianum

While there has been intensive research on the influence of microplastics (MPs) on aquatic organisms and humans, their effect on microorganisms is relatively little-known. The present study describes the response of the Trichoderma harzianum strain to low-density polyethylene (LDPE) microparticles. MPs, either separately or with metolachlor (MET), were added to the cultures. Initially, MP was not found to have a negative effect on fungal growth and MET degradation. After 72 h of cultivation, the content of fungal biomass in samples with MPs was almost three times higher than that in the cultures without MPs. Additionally, a 75% degradation of the initial MET was observed. However, due to the qualitative and quantitative changes in individual classes of phospholipids, cell membrane permeability was increased. Additionally, MPs induced the overproduction of reactive oxygen species. The activity of superoxide dismutase and catalase was also increased in response to MPs. Despite these defense mechanisms, there was enhanced lipid peroxidation in the cultures containing the LDPE microparticles. The results of the study may fill the knowledge gap on the influence of MPs on filamentous fungi. The findings will be helpful in future research on the biodegradation of contaminants coexisting with MPs in soil.

Myco-degradation of microplastics: an account of identified pathways and analytical methods for their determination

Microplastics (MPs) have sparked widespread concern due to their non-degradable and persistent nature in ecosystems. Long-term exposure to microplastics can cause chronic toxicity, including impaired reproduction and malnutrition, threatening biota and humans. Microplastics can also cause ingestion, choking, and entanglement in aquatic populations. Thus, it is crucial to establish remarkably effective approaches to diminish MPs from the environment. In this regard, using fungi for microplastic degradation is beneficial owing to its diverse nature and effective enzymatic system. Extracellular and intracellular enzymes in fungi degrade the plastic polymers into monomers and produce carbon dioxide and water under aerobic conditions whereas methane under anaerobic conditions. Further, fungi also secrete hydrophobins (surface proteins) which serve as a crucial aid in the bioremediation process by promoting substrate mobility and bioavailability. Therefore, the present review provides insight into the mechanism and general pathway of fungal-mediated microplastic degradation. Additionally, analytical techniques for the monitoring of MPs degradation along with the roadblocks and future perspectives have also been discussed. However, more research is required to fully perceive the underlying process of microplastic biodegradation in the environment using fungus, to establish an effective and sustainable practice for its management.

Prevalence of small-sized microplastics in coastal sediments detected by multipoint confocal micro-Raman spectrum scanning

Microplastics have become global emerging issue and received widespread attention in recent years. Due to their chemical persistence, plastic particles can be broken into smaller items but accumulated for long time in the environment like sediment. However, limited by current detection technologies, the distribution and characteristics of small-sized microplastics in coastal sediment remain uncertain. In this study, we established a new method based on micro-Raman spectroscopy for detecting small-sized microplastics, namely multipoint confocal micro-Raman spectrum scanning (MCmRSS). The MCmRSS was first applied in detecting microplastics in the sediment samples collected from three bays of the East China Sea. The minimum size of microplastics was 4 μm and average microplastics concentration was 91 ± 55 items /g dry weight sediment, with fragment and polyethylene as the most common shape and polymer type, respectively. The spatial variation of microplastics was in accordance with the strength of coastal human activities and marine dynamics. In all the microplastic items, the small-sized ones (<10 μm) accounted for 67%; and the relationship between microplastic concentration and its size followed a power-exponential equation. Compared with previous studies, the number of microplastics in coastal sediments detected by the MCmRSS increased by 2 orders of magnitude, which was benefited from the advantages of multipoint scanning in the fixed identification areas and high resolution of micro-Raman spectrum. Our findings would summon the re-evaluation of the potential risks of small-sized microplastics in the coastal environment.

Sustainable Tourism and Conservation of Underground Ecosystems through Airflow and Particle Distribution Modeling

Underground ecosystems are often of interest for the tourism industry due to their important naturalistic and cultural heritage. Since these underground ecosystems are almost completely isolated, external agents (such as human presence) can easily disrupt their chemico-physical and biological processes, which can affect, sometimes irrevocably, their natural equilibrium, placing the preservation of such sites at risk. The most sensible managers of caves, catacombs, mines, and all the accessible cultural sites are searching for methods to control these dynamics and the modeling appears to be effective in preventing scenarios of the known impacts as well as suggesting strategies for their mitigation. In this study, by employing finite element analysis by the COMSOL Multiphysics software and reproducing, in a simplified way, a section of the tourist trail of the Pertosa-Auletta Cave (Italy), for the first time we provided a fact-finding survey of the airflow and the scattering and subsequent deposition of particles transported by tourists. Taking into account discontinuities in the pathway, the simulations rebuilt the possible natural airflow line, reproducing the particle movements induced by different tourist loads, whose high numbers increase the swirling movement of air masses, promoting a higher dispersion of particles, even in the remote cave areas. Performed simulations clearly indicated both the speed and direction followed by particles, as well as deposition sites, highlighting potential hotspots of damage, and demonstrating that the employed approach can be an excellent tool for planning the management of these extraordinary ecosystems, foretelling anthropogenic impacts, and supporting managers in decision-making processes.

Advanced microplastic monitoring using Raman spectroscopy with a combination of nanostructure-based substrates

Micro(nano)plastic (MNP) pollutants have not only impacted human health directly, but are also associated with numerous chemical contaminants that increase toxicity in the natural environment. Most recent research about increasing plastic pollutants in natural environments have focused on the toxic effects of MNPs in water, the atmosphere, and soil. The methodologies of MNP identification have been extensively developed for actual applications, but they still require further study, including on-site detection. This review article provides a comprehensive update on the facile detection of MNPs by Raman spectroscopy, which aims at early diagnosis of potential risks and human health impacts. In particular, Raman imaging and nanostructure-enhanced Raman scattering have emerged as effective analytical technologies for identifying MNPs in an environment. Here, the authors give an update on the latest advances in plasmonic nanostructured materials-assisted SERS substrates utilized for the detection of MNP particles present in environmental samples. Moreover, this work describes different plasmonic materials-including pure noble metal nanostructured materials and hybrid nanomaterials-that have been used to fabricate and develop SERS platforms to obtain the identifying MNP particles at low concentrations. Plasmonic nanostructure-enhanced materials consisting of pure noble metals and hybrid nanomaterials can significantly enhance the surface-enhanced Raman scattering (SERS) spectra signals of pollutant analytes due to their localized hot spots. This concise topical review also provides updates on recent developments and trends in MNP detection by means of SERS using a variety of unique materials, along with three-dimensional (3D) SERS substrates, nanopipettes, and microfluidic chips. A novel material-assisted spectral Raman technique and its effective application are also introduced for selective monitoring and trace detection of MNPs in indoor and outdoor environments.

A Global Perspective on Sustainable Show Cave Tourism

Caves are among the most visited geological features in the world, attracting over 70 million people every year in more than 1,200 caves worldwide, and amounting up to 800 million Euros in entrance fees alone. The global business of show caves employs roughly 25,000 people directly (management, guides), and at least 100 times more people if we consider the connected tourist activities (souvenir shops, local transport, travel agencies, restaurants, and bars). It is estimated that the whole show cave business has a global commercial value of roughly 2 billion Euros, a number that is increasing constantly. Show caves are generally fragile ecosystems, and care should be taken in their management to safeguard their value for future generations. The international scientific (speleological) community has issued international guidelines for the sustainable development and management of show caves eight years ago, but their application is still far from being applied globally, especially in developing and least developed countries. Cave tourism is expected to increase, especially in countries where caves are abundant but not yet considered as tourist attractions, and where economic and political instability slow down the development of tourism. There are still a lot of possibilities for the opening of new show caves, especially in countries with low Gross Domestic Income (GDI), but their management needs to be sustainable, so that caves become a means of sustaining local economies, educating people on these fragile geo- and ecosystems, and protecting contemporarily their scientific and cultural heritage for future generations.