Abundance and fate of glass microspheres in river sediments and roadside soils: Lessons from the Świętokrzyskie region case study (south-central Poland)

Legacy of anthropogenic activity recorded in sediments by microtechnofossils and chemical markers

This overview presents comparison of common microtechnofossils with other geochemical markers that may have the great potential to be the anthropogenic signatures for recent and future sediment strata. The novel man-made products encompass spherical and spheroidal fly-ash particulates, microplastics, synthetic crystals, and more recently examined glass microspheres. Due to their low specific gravity and small size varying from a tiny fraction of millimeter to approximately 5 mm, microtechnofossils may be transported over a long distance from their primary or secondary sources by water and wind. Of these technogenic materials, among the most resistant to physical and chemical degradation are glass microbeads, and additionally synthetic crystals and some types of fly-ash particulates derived mostly from coal/oil combustion, metal ore smelting operations and cement/lime manufacturing. Nonetheless, synthetic glass microspheres have found exponentially growing applications as reflective ingredients in traffic-related paints and building facades, as well as in a variety of applications mostly as low-density fillers of many materials. In contrast to anthropogenic fly-ash and microplastic particles, glass microspheres resemble in many respects common detrital quartz grains. Moreover, like quartz, they are resistant to depositional and diagenetic processes, which is a prerequisite for future geologic archives preserving anthropogenic signals. These and other characteristics make glass microspheres a more widely used product in various fields thus assigning them to a new emerging and globally spreading chronostratigraphic marker of human-impacted sediments.

An explicit review and proposal of an integrated framework system to mitigate the baffling complexities induced by road dust-associated contaminants

Road dust-associated contaminants (RD-AC) are gradually becoming a much thornier problem, as their monotonous correlations render them carcinogenic, mutagenic, and teratogenic. While many studies have examined the harmful effects of road dust on both humans and the environment, few studies have considered the co-exposure risk and gradient outcomes given the spatial extent of RD-AC. In this spirit, this paper presents in-depth elucidation into the baffling complexities induced by both major and emerging contaminants of road dust through a panorama-to-profile up-to-date review of diverse studies unified by the goal of advancing innovative methods to mitigate these contaminants. The paper thoroughly explores the correlations between RD-AC and provides insights to understand their potential in dispersing saprotrophic microorganisms. It also explores emerging challenges and proposes a novel integrated framework system aimed at thermally inactivating viruses and other pathogenic micro-organisms commingled with RD-AC. The main findings are: (i) the co-exposure risk of both major and emerging contaminants add another layer of complexity, highlighting the need for more holistic framework strategies, given the geospatial morphology of these contaminants; (ii) road dust contaminants show great potential for extended prevalence and severity of viral particles pollution; (iii) increasing trend of environmentally persistent free radicals (EPFRs) in road dust, with studies conducted solely in China thus far; and (iv) substantial hurdle exists in acquiring data concerning acute procedural distress and long-term co-exposure risk to RD-ACs. Given the baffling complexities of RD-ACs, co-exposure risk and the need for innovative mitigation strategies, the study underscore the significance of establishing robust systems for deep road dust contaminants control and future research efforts while recognizing the interconnectivity within the contaminants associated with road dust.

Contamination of Thames Estuary sediments by retroreflective glass microbeads, road marking paint fragments and anthropogenic microfibres

Surface and subsurface sediment samples (n = 16) from the highly urbanised inner Thames Estuary (UK) have been physically and chemically characterised and analysed for anthropogenic microdebris. Sediments were gravelly sands throughout and were heavily contaminated by lead (Pb, up to 12,500 mg kg-1) and zinc (Zn, up to 9500 mg kg-1). Microfibres of mm-dimensions and retroreflective glass microbeads (median diameter = 188 μm) used in road markings were the most abundant types of microdebris present, and concentrations (as numbers, N) on a dry weight basis were spatially heterogeneous (ranging from about 4000 to 60,000 N kg-1 and 100 to 28,000 N kg-1, respectively). Nevertheless, concentrations of the two types of particle were significantly correlated and both displayed an inverse, non-linear relationship with sediment grain size. Road marking paint fragments of different colours were detected in most cases (n = 13) but quantification was difficult because of analytical constraints related to size, shape, colour, fragmentation and encrustation. Concentrations of up to about 500 mg kg-1 Pb were determined in isolated paint fragments but road paint particles are unlikely to make a significant contribution to Pb pollution in Thames Estuary sediments. Overall, our observations suggest that stormwater runoff is a significant source of multiple types of anthropogenic microdebris in urban estuaries, with additional, direct atmospheric deposition contributing to microfibre accumulation. More generally, it is recommended that studies of microplastics consider additional debris and sediment characteristics for a better understanding of their sources and transport.

Glass microbeads in coastal sediments as a proxy for traffic-related particulate contamination

Retroreflective glass microbeads used in road markings have been characterised and subsequently identified in urban coastal sediments. Clear or translucent silica beads range in diameter from about 30 to 700 μm and readily break from the matrix of detached or damaged markings on abrasion. At an urban location close to the city centre of Plymouth, southwest England, and in an estuary below a large road bridge, microbeads were detected in nearly all intertidal sediments analysed (n = 18) and at concentrations up to about 550 kg^-1 dw. At a location not immediately impacted by major roads, beads were entirely absent from sediments (n = 9). With a size range and density similar to silt-sand, glass beads appear to accumulate in sediment subject to road runoff and act as persistent proxies for traffic-related contamination. Although beads are unlikely to be inherently toxic, they may serve as indicators of more harmful chemicals in road dust.

Research on the Regional Environmental Impact and Risk Assessment Affected by Mineral Resource Development: A Case Study of the Taojia River Watershed in Hunan

The mining and production of mineral resources can directly lead to soil and water pollution, posing a serious threat to human health. In this study, the Taojia River basin, a tributary of the Xiangjiang River, was selected as the study area. Based on the concentrations of heavy metals (As, Cd, Pb, and Zn) in 653 soil/substrate samples collected from 342 points in the study area in 2013 and 2021, the changes in soil heavy metal concentrations in the region were systematically analyzed to assess their environmental risks and impacts on regional environmental quality. The results showed that from 2013 to 2021, the As, Pb, and Zn pollution in regional soil, tailing sand, and surface water was reduced, while the Cd pollution increased. The average soil As, Pb, and Zn concentrations decreased from 3,750, 2,340, and 1,180 mg/kg to 457, 373, and 387mg/kg, respectively, while the Cd concentration increased from 0.11to 1.91 mg/kg; additionally, the overall distribution trend of heavy metal concentrations was high in the south, low in the north, and gradually decreased from upstream to downstream. The single evaluation index of heavy metal pollution risk showed that the percentages of medium to heavy pollution points in the soil As, Pb, and Zn were 84, 57, and 28%, respectively, in 2013, and this index decreased to 38, 37, and 25%, respectively, in 2021. The regional environmental quality was closely related to the intensity of mineral resource development. From 2000 to 2010, frequent mining development activities led to an increase in the area of construction land and a continuous decrease in the area of arable land, grassland, and vegetation cover in the region. During 2010–2020, the area of construction land decreased, and the vegetation coverage increased. The comprehensive evaluation index showed that the overall soil pollution risk in the watershed decreased, and the proportion of heavily polluted points decreased from 80 to 65%. It was shown by principal component analysis and factor analysis that mining development activities were the largest source of heavy metal pollution, in addition to mixed sources of tailings, solid waste, agriculture, and traffic emission sources. The results provide a scientific basis for the management and risk control of heavy metal pollution in the Taojia River basin.

Glass Beads for Road Markings: Surface Damage and Retroreflection Decay Study

Road markings must be reflectorised with glass beads to be visible to drivers at night, retro-reflecting light from vehicle’s headlights, which is critical for road safety. Four commonly used types of glass beads were evaluated in a laboratory setting for retroreflectivity and their surfaces were analysed using optical and scanning electron microscopy. The glass beads were subjected to abrasion and a visual correlation was sought between the measured retroreflectivity and the surface damage. Scratching the glass bead surface with corundum in a rotary drum resulted in major differences in the rates of damage development, depending on the type of the glass beads, and it could be correlated with the rate of retroreflectivity decay. The relative results from abrasion testing were confirmed under tyre action during a turntable evaluation. Based on the outcomes of these tests, service lives, defined as maintaining appropriately high retroreflectivity, were predicted and used to calculate the consumption of raw materials—the basic sustainability parameter. It was shown that the use of ‘premium’ glass beads, enhanced with TiO2 and made in a proprietary process, provided the road marking system characterised by the lowest long-term consumption of resources.