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.

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.

Release of microplastic fibers from synthetic textiles during household washing.

Textile materials are one of the primary sources of microplastic pollution. The washing procedure is by far the most significant way that textile products release microplastic fibers (MPFs). Therefore, in this study, the effects of various textile raw materials (A acrylic, PA polyamide, PET polyester, RPET recycled polyester and PP polypropylene), fabric construction properties (woven, knitted), thickness and basis weight values on MPFs release at different washing stages (pre-washing, soaping/rinsing) were examined separately. To mimic the most popular home washing procedures, a 10-minute pre-wash and a 35-minute soaping/rinsing phase at 40°C were selected for the washing procedure. Utilizing the Image J program on macroscopic images captured by a high-resolution SL.R camera, the microfibers collected by filtering the water have been visually counted. According to the results, knitted fabrics released fewer MPFs than woven fabrics, with the woven acrylic sample (A3-w) exhibiting the highest release (2405 MPFs). The number of MPFs increased along with the thickness and weight of the fabric. Recycled polyester was found to release more MPFs than virgin polyester under the same conditions (1193 MPFs vs. 908 MPFs). This study demonstrates how recycled polyester, although initially an environmentally beneficial solution, can eventually become detrimental to the environment. Furthermore, it is known that the pre-washing procedure-which is optional-releases a lot more MPFs than the soaping and rinsing procedures, and that stopping this procedure will drastically lower the amount of MPFs incorporated into the water.

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.

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.

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.

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

Microplastic particles are a global problem, which has been widely found in marine and terrestrial environments. However, microplastic pollution in caves and karst aquifers is still poorly studied. To improve the current knowledge of microplastic pollution, we investigated the sediments of a show cave in Italy. We developed a methodology based on a cave-adapted version of the methods used in several studies to detect microplastics from sediments of different environments and with various laboratory tests. The microplastics were extracted from sediments via density separation and subjected to organic matter removal. Filters were observed with and without UV light under a microscope, before and after organic matter removal, and the microplastics were characterised according to shape, colour, and size, with visual identification. About 55% of the fibres observed under the microscope on filters were removed via organic matter removal. An average of 4390 items/kg dry weight was calculated for the touristic zone and 1600 items/kg dry weight for the speleological/research section. Fibre (84.9%) was the most abundant shape, and most microplastics were smaller than 1 mm, accounting for 85.4%, of which 58.4% were shorter than 0.5 mm. The highest microplastic abundance was fluorescent under UV light (87.7%); however, 12.3% of the microplastics observed on filters were not fluorescent. Most fluorescent fibres were transparent (84%), whereas blue (46.1%) and black (22.4%) fibres were more common for the non-fluorescent ones. Our results highlight the presence of microplastics in show caves, and we provide a valid non-invasive and non-expensive analytical technique for the preparation and isolation of microplastics from cave sediments, giving useful information for evaluating the environmental risks posed by microplastics in show caves.

Gravity and Electrostatic Separation for Recovering Metals from Obsolete Printed Circuit Board.

This study proposed an evaluation of enrichment processes of obsolete Printed Circuit Boards (PCBs), by means of gravity and electrostatic separation, aiming at the recovery of metals. PCBs are the most important component in electronic devices, having high concentrations of metals and offering a secondary source of raw materials. Its recycling promotes the reduction in the environmental impacts associated with its production, use, and disposal. The recovery method studied started with the dismantling of the PCB, followed by a comminution and granulometric classification. Subsequent magnetic, gravity, and electrostatic separations were performed. After the separations, a macroscopic visual evaluation and chemical analysis were carried out, determining the metal content in the concentrate products. The results obtained from gravity separation showed a product with metallic concentrations of 89% and 76% for particle sizes of 0.3−0.6 mm and 0.6−1.18 mm, respectively. In electrostatic separation, the product obtained was 88% for the lower particle size (<0.3 mm) and 62% for particles sizes >1.18 mm.

Silicate Sawing Sludge Recovery in Thermo Eco-Mortar for Macroporous Plaster.

The aim of this research was to develop a new eco-product to find a correct recovery of silicate sawing sludge by means of waste management according to European criteria. To reach this goal, a thermal eco-mortar for a macroporous plaster was developed. The main characteristics of a plaster that influence the correct choice of the mortar are good adherence with underlying support, impermeability, thermal and acoustic insulation, mechanical resistance and ability to allow transpiration processes through the wall's perimeters. Plaster is a mortar composed of a binding part that incorporates sand with a selected particle size distribution, not greater than 2 mm. The sludge, to be used as plaster, must satisfy requirements related to thermal insulation, resistance to moisture, mechanical resistance and good injection. For this purpose, low-content metals sludge, derived from the Luserna stone flaming and cutting slabs, are to be reused as a substitute for the sands and fine particles, respectively, that are normally used to produce plasters. The laboratory tests carried out on the finished product, in accordance with European standards, are as follows: water absorption, specific density, flexural and compressive strength, before and after freeze and thaw cycles, pull out, salt crystallisation cycle resistance and thermal conductivity. Chemical and leaching tests were carried out to verify the possible release of heavy metals into the environment after installation. The product quality was demonstrated as the cement mortars, incorporating the metals, did not allow their release in nature. A sludge recovery, in an unaltered state, was provided to reduce any costs connected to a pre-treatment and to make recovery economically advantageous for the stone sector.