The COVID-19 pandemic has driven explosive growth in the use of masks has resulted in many issues related to the disposal and management of waste masks. As improperly disposed masks enter the ocean, ...the risk to the marine ecological system is further aggravated, especially in the shoreline environment. The objective of this study is to explore the changing characteristics and environmental behaviors of disposable masks when exposed to the shoreline environment. The transformation of chain structure and chemical composition of masks as well as the decreased mechanical strength of masks after UV weathering were observed. The melt-blown cloth in the middle layer of masks was found to be particularly sensitive to UV irradiation. A single weathered mask can release more than 1.5 million microplastics to the aqueous environment. The physical abrasion caused by sand further exacerbated the release of microplastic particles from masks, with more than 16 million particles released from just one weathered mask in the presence of sand. The study results indicate that shorelines are not only the main receptor of discarded masks from oceans and lands, but also play host to further transformation of masks to plastic particles.
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•Disposable masks are widely observed on shorelines during the pandemic.•Physicochemical features of disposable masks changed dramatically under UV weathering.•The transformation of chain structure and decreased mechanical strength were observed.•Masks can be broken into small pieces, releasing a large quantity of microplastics.•Around 1.5 million particles can be released from a disposable mask after weathering.
We examined the fate and behaviour of diluted bitumen (dilbit) as it weathered for 70 days in freshwater limnocorrals (10 m diameter × 1.5 m depth) installed in a boreal lake to simulate dilbit ...spills in a natural aquatic environment. We added seven different dilbit spill volumes, ranging from 1.5 to 180 L, resulting in oil-to-water ratios between 1:71,000 (v/v, %) and 1:500 (v/v, %). Volatile hydrocarbons in the dilbit slick decreased rapidly after the dilbit was spilled on the water's surface, and dilbit density and viscosity significantly increased (>1 g mL−1 and >5,000,000 mPa s, respectively). Dilbit sank to the bottom sediments in all treatments, and the time to sinking was positively correlated with spill volume. The lowest dilbit treatment began to sink on day 12, whereas the highest dilbit treatment sank on day 31. Dilbit submerged when its density surpassed the density of freshwater (>0.999 g mL−1), with wind, rain, and other factors contributing to dilbit sinking by promoting the break-up of the surface slick. This experiment improves our ability to predict dilbit's aquatic fate and behaviour, and its tendency to sink in a boreal lake. Our findings should be considered in future pipeline risk assessments to ensure the protection of these important aquatic systems.
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•Dilbit density and viscosity quickly surpasses thresholds of efficient recovery.•Dilbit sinks between 12 and 31 days following the spills.•The onset of dilbit submergence is related to the volume of dilbit spilled.•Suspended sediments and mixing not likely drivers of submergence in this study.
•Transparent wood composite (TWC) is susceptible to weathering deterioration.•Weathering TWC is manifested by discoloration and loss in optical transmittance.•Degradation of lignin and breakdown of ...epoxy network observed.•Detrimental effect of weathering can be retarded by incorporating UV absorber in TWC.
Transparent wood composite (TWC) is an innovative wood-based polymeric material prepared by the impregnation of a suitable polymer into the lignin-modified wood substrate. TWC has gained significant attention for several outdoor applications including transparent wood smart windows, substrate for solar cells, light management devices and energy-efficient building materials. However, the interaction of TWC with various environmental factors affects its physical aesthetics, chemical and optical properties, thus impairing its effectiveness as an outdoor material. Therefore, the outdoor durability of TWC is important while considering its growing popularity. In this study, the effects of natural weathering on the properties of TWC prepared from two wood species, viz., Melia dubia (Melia) and Populus deltoides (Poplar) were investigated. The effects of weathering on TWC were evaluated in terms of changes in visual appearance, colour parameters, optical transmittance and chemical changes. Prominent colour changes were observed on the samples soon after the exposure to natural environment mainly due to photo-oxidative degradation by solar UV radiation. FTIR measurements revealed chemical degradation of the exposed polymeric materials. The optical transmittance of TWC exposed to natural weathering for 150 days showed colour darkening and a transmittance loss of ∼33–35 %. The addition of a benzotriazole-derived UV absorber (1.75 % conc.) in TWC was found effective in reducing photo-yellowing in TWC and limiting the transmittance loss to 15 %.
The structural properties of geopolymers based on locally available volcanic feedstocks were here investigated in the optics of the development of sustainable non-structural building materials. ...Geopolymer binders and mortars based on two volcanic pyroclastic residues from Mt. Etna (ejected ash and a paleosoil, named “ghiara”) were studied to assess the effects of natural weathering.
The strength and durability of the resultant products were examined before and after six months of outdoor exposure by comparing ultrasound pulse velocity (UPV), specific weight, Brazilian Disk test (BD) and Digital Image Correlation (DIC) together with Dynamic Vapour Sorption (DVS) results. DVS data were also compared to those of pure salts (e.g. sulphates and carbonates) commonly occurring in geopolymers as efflorescences.
The results obtained on unexposed and exposed samples and the relationship between the moisture transportation, efflorescence development, and structure degradation have shown a better response of the volcanic ash-based geopolymers to weathering in the hot summer Mediterranean climate zone than ghiara-based products. The latter are more affected by exposure conditions as revealed by the decrease of UPV, the influence of efflorescences on moisture adsorption-desorption curves and the consequent worsening of mechanical performances.
The correlation between UPV and DVS applied for the first time to the study of volcanic precursors-based geopolymers exposed to natural weathering has proven to be an effective and useful tool for assessing the durability of materials.
•Five types of plastic as the matrix phase in WPCs were compared.•ANOVA, Tukey’s multiple range comparison, and t-test were applied.•The plastic type was found to significantly affect the mechanical ...properties of WPC.•Mechanical property losses from weathering were the least for WPCs from PS and PP.
The influences of plastic matrix on mechanical properties (flexural and tensile properties) of wood-plastic composites (WPCs) were investigated. WPCs were prepared with five types of plastic as the matrix phase, namely high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS). Rubberwood flour was used as reinforcing filler. Additionally, maleic anhydride, UV-stabilizer, and paraffin wax were used as coupling agent, ultraviolet stabilizer and lubricant, respectively. The WPCs were produced in two stages: mixing in an internal mixer, and compression molding. WPCs from PS and PP exhibited higher mechanical properties whereas LDPE, HDPE, and PVC gave lower values. In particular LDPE gave consistently the poorest mechanical properties to WPCs. Moreover, the WPCs with PS and PP had the smallest losses of mechanical properties from natural weathering, while LDPE would again be the poorest choice in this respect. These results indicate that WPCs from PP and PS are the best alternatives for applications requiring resistance to natural weathering (exposure to ultraviolet and humidity) or with high mechanical loading (stresses).
Natural weathering of polystyrene (PS) was performed at six exposure sites with various climate types along the coastal line from China to Europe, including Qionghai (typical hot-humid climate), ...Sansha (island hot-humid climate), Chennai (savanna hot-humid climate), Jeddah (xerothermic climate), Sanary-sur-Mer (mediterranean climate), Hoek van Holland (warm-temperate climate). The chemical structure, morphology and color changes of PS after weathering were characterized by FTIR, DSC, SEM and Color spectrometer, and relative weathering severity of different climates on PS were compared. Results show that Sansha has the highest severity value while the severity value of Hoek van Holland is the lowest. The degradation degree of PS at the sites of Qionghai, Sansha, and Chennai is higher than that at other sites, resulted in a deterioration of the optical properties and serious damage of the sample surface. In the xerothermic climate, the optical properties of PS decrease drastically during the process of natural weathering, while only slight change in hydroxyl index and carbonyl index is observed, and micrographic surface does not differ from the surface of un-weathered materials. For other climates, the degradation degree was low, resulting in a relative slow change of optical properties and long time for the appearance of surface defects. In order to quantify the relative severity of these climates, a mathematic model was proposed based on the basic degradation principle of polymer materials, which could predict the failure time of PS. The failure time was predicted by the model using gloss loss of PS as failure index, with an accuracy up to 99.2%.
•Weathering of PS was performed at six exposure sites with various climate types along the coastal line from China to Europe.•The PS degrade faster at hot-humid climate sites than at other sites during the exposure.•Sansha has the highest severity while the severity value of Hoek van Holland is the lowest.•Due to the low average relative humidity, the weathering process of PS at xerothermic climate was restricted significantly.•A mathematic model with an accuracy up to 99.2% was proposed to predict the failure time of PS.
Zinc (Zn)-Lead (Pb) deposits are generally rich in cadmium (Cd), and the weathering of sulfide minerals in such deposits results in large releases of Cd into the environment. From an environmental ...and public health standpoint, understanding Cd sources and cycling is critical to identifying potential hazards to humans. In this study, the Cd isotope compositions (expressed as δ114/110Cd) of secondary minerals such as anglesite (−0.57±0.03‰; 2S.D.), granular smithsonite (0.04±0.14‰; 2S.D.), layered smithsonite (0.15±0.40‰; 2S.D.), hydrozincite (0.26±0.01‰; 2S.D.) and clay minerals (−0.01±0.06‰; 2S.D.) from the Fule Zn-Pb-Cd deposit, Southwest China, are investigated to better understand the Cd sources and cycling in this area.
Combined with our previous study (Zhu et al., 2017), the work herein elucidates the patterns of Cd isotopic fractionation during the formation processes of such secondary minerals and traces the weathering of these minerals into the ecosystem. The δ114/110Cd values of secondary minerals exhibit the following decreasing trend: hydrozincite>large granular smithsonite>small granular smithsonite>anglesite. Although different amounts of Cd were lost during the formation of equally sized samples, no or minor variations in Cd isotopic composition were observed. However, significant isotopic differences were observed between different size fractions. These results demonstrate that the particle size of secondary minerals and weathering products of sulfide significantly influence Cd isotope composition and fractionation during natural weathering. This systematic fractionation provides an initial foundation for the use of Cd isotopes as environmental tracers in ecosystems and in the global Cd isotope budget.
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•Determined Cd isotopic compositions in sulfides and different secondary minerals•Weathering could result in detectable Cd isotope fractionation (Δ114/110Cd≈0.33‰).•The δ114/110Cd values and Cd contents decline linearly during weathering.•Mineral species and grain size control Cd isotope variations in secondary minerals.
•FRC girders were exposed to long term natural weathering action.•PPFRC showed less WA and CP values than SFRC.•SEM and EDX analysis showed no corrosion in FRCs.•FRCs are durable against long term ...natural weathering action.
It is common perception that fiber reinforced concretes (FRCs) are prone to internal and external deterioration due to presence of fibers. This is the reason that construction industry is reluctant to use FRC despite of having large number of advantages. The main objective of this research is to investigate the natural weathering effect on prestressed concrete girders. These girders comprising of one control mix, two girders with steel fiber reinforced concrete (SFRC), two with polypropylene fiber reinforced concrete (PPFRC) and one having both fibers. The specimens were undergone natural exposure to open atmosphere for 36 months. The durability properties studied include unit weight, compressive strength, water absorption, porosity, sorptivity coefficient, chloride penetration test, scanning electron microscope analysis and energy dispersive X-Ray analysis. It was concluded that by natural weathering exposure polypropylene fibers improve the durability and they negate the effect of steel fibers in case of hybrid fiber reinforced concrete.
In this research work, both natural weathering and artificial weathering processes were carried out to investigate the effects of multi-functional epoxy chain extender (Joncryl ADR 4370) content on ...the degradation and the mechanical properties and molecular weight of poly(butylene adipate-co-terephthalate) (PBAT). The carboxyl end-groups of PBAT decreased significantly with an increase in ADR content from 0 to 1.5 wt%. Similarly, the molecular weight of PBAT initially increased and then decreased because of the formation of a crosslinked network structure under the influence of excessive chain extenders. The main degradation mechanism of PBAT during the natural and artificial weathering process is photo-degradation and hydrolyzation. The degradation rate of PBAT increased with increasing content of chain extender, as hydroxyl groups facilitate the water attack on the ester bonds of PBAT. In contrast, the higher content of chain extender presented the lower loss velocity of the tensile strength. This is mainly because the more ADR content, the more crosslinking network structures will be formed during the melting extrusion which can slow down the decrease of tensile strength. Hence, it is indicated that the crosslinking structure has more effect on tensile strength than that of hydrolysis effect during degradation. According to the analysis and study on the performance changes of PBAT/ADR materials under the conditions of long-term natural weathering (360d) and artificial weathering (600 h), this work provides theoretical guidance to produce PBAT mulching films with excellent performance.
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•Effect of chain extender and its content on weathering resistance of the PBAT.•The main degradation mechanism of PBAT during weathering process is photo-degradation and hydrolyzation.•The higher content of chain extender presents the lower loss velocity of the PBAT tensile strength.•This work provides theoretical guidance to produce PBAT mulching films with excellent performance.
Bamboo structures are susceptible to natural weathering when exposed to outdoor conditions, making it imperative to comprehend the aging resistance of bamboo. In this paper, the study of Moso bamboo ...exposed to outdoor environment for one year illustrates the discoloration, expansion, mass loss and density reduction of the specimens. The changes of relative crystallinity (CrI) of bamboo were measured by using X-ray diffraction (XRD), the microstructural changes of bamboo were observed by scanning electron microscopy (SEM), and the computed tomography (CT) scanning technology was used to analyze the internal structure of the damaged specimens. Meanwhile, the damage and differences in the mechanical properties of bamboo internodes and nodes were evaluated by the tests of compression parallel to the grain, compression perpendicular to the grain and compressive elastic modulus parallel to the grain, taking into account the bamboo height. The results showed that natural weathering reduces cellulose crystallinity and has a detrimental effect on the cellular structure of bamboo, resulting in a weakening of the interfacial bonding between the vascular bundles and the parenchyma. Consequently, this leads to a decrease in the mechanical properties of bamboo. Compared to the internode specimens, the compressive strength perpendicular to the grain and compressive elastic modulus parallel to the grain are higher in the bamboo node specimens. However, the compressive strength parallel to the grain will be significantly reduced due to the complex fiber structure inside the bamboo nodes. In light of the experimental findings, a constitutive model is proposed to describe the relationship between uniaxial compressive stress and strain in Moso bamboo, both before and after weathering. The numerical results obtained from this model demonstrate a strong correlation with the experimental findings, thereby establishing a solid foundation for conducting finite element analysis on Moso bamboo structures.
•The cellulose crystallinity and microstructural changes of weathered bamboo were analyzed.•Comparative studies were conducted to investigate the mechanical properties of weathered bamboo.•An axial compressive stress-strain constitutive model of weathered bamboo was proposed.
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