Aging, characterization and sorption behavior evaluation of tire wear particles for tetracycline in aquatic environment

Potential deterioration of chemical water quality due to trace metal adsorption onto tire and road wear particles - Environmentally representative experiments

Tire wear particles are an increasing issue in particle emissions to the environment. Germany-wide approximately 100,000 t tire wear particles are emitted every year into the environment which are estimated to be one third of the microplastic emissions. Up to 20% are estimated to reach inland surface waters. Their behavior in the aquatic environment is understudied. Tire wear particles have an overly hydrophobic surface that is capable of adsorbing substances like trace elements. In this study we investigated the adsorption and desorption of trace metals onto and from the particle surface of tire-related samples in water samples of the Freiberger Mulde, a river with naturally elevated concentration of trace elements. The priority trace metals Cr, Ni, Zn, Cd and Pb show a significant adsorption onto the particle surface of tire-related samples. Tire wear particles themselves revealed adsorption of mainly Ni, Cd and Pb. Regarding the German classification for suspended matter in freshwaters, an endangering of the chemical water quality is expected due to the adsorption process and not due to the particles themselves. Upcoming electromobility is expected to increase the Zn (increased tire abrasion) and decrease the Cu amount (reduced brake abrasion) released to freshwaters.

Microbial carbon metabolism patterns of microplastic biofilm in the vertical profile of urban rivers

Microplastics (MPs) can provide a unique niche for microbiota in waters, thus regulating the nutrients and carbon cycling. Following the vertical transport of MPs in waters, the compositions of attached biofilm may be dramatically changed. However, few studies have focused on the related ecological function response, including the carbon metabolism. In this study, we investigated the microbial carbon metabolism patterns of attached biofilm on different MPs in the vertical profile of urban rivers. The results showed that the carbon metabolism capacity of biofilm on the degradable polylactic acid (PLA) MPs was higher than that in the non-degradable polyethylene terephthalate (PET) MPs. In the vertical profile, the carbon metabolism rates of biofilm on two MPs both decreased with water depth, being 0.74 and 0.91 folds in bottom waters of that in surface waters. Specifically, the utilization of polymers, carbohydrate, and amine of PLA biofilm was significantly inhibited in the bottom waters, which were not altered on the PET. Compared with surface waters, the microbial metabolism function index of PLA biofilm was inhibited in deep waters, but elevated in the PET biofilm. In addition, the water quality parameters (e.g., nutrients) in the vertical profile largely shaped carbon metabolism patterns. These findings highlight the distinct carbon metabolism patterns in aquatic environments in the vertical profile, providing new insights into the effects of MPs on global carbon cycle.

Combined toxicity of pristine or artificially aged tire wear particles and bisphenols to Tigriopus japonicus

Tire wear particles (TWPs) are considered an important component of microplastic pollution in the marine environment and occur together with a variety of aquatic pollutants, including frequently detected bisphenols. The adverse effects of TWPs or bisphenols on aquatic organisms have been widely reported. However, the combined toxicity of TWPs and bisphenols is still unknown. In this study, the combined toxicity of both pristine (p-) and aged TWPs (a-TWPs) and four bisphenols ((bisphenol A (BPA), bisphenol F (BPF), bisphenol S (BPS), and bisphenol AF (BPAF)) to Tigriopus japonicus was evaluated. TWPs increased the toxicity of BPA and BPF but decreased the toxicity of BPAF. For BPS, there was synergistic toxic effect in the presence of p-TWPs, but slightly antagonistic effect was observed in the presence of a-TWPs. This adsorption of BPAF by TWPs resulted in a reduction of its toxicity to the copepod. A-TWPs could release more Zn than p-TWPs, and the released Zn contributed to the synergistic effect of TWPs and BPA or BPF. The aggregation formed by TWPs in certain sizes (e.g., 90-110 μm) could cause intestinal damage and lipid peroxidation in T. japonicus. The synergistic effect of p-TWPs and BPS might be due to the aggregation size of the binary mixture. The results of the current study will be important to understand the combined toxic effect of TWPs and bisphenols and the potential toxic mechanisms of the binary mixture.

Interfacial interactions of polyethylene terephthalate microplastics and malachite green, tetracycline in aqueous environments

Polyethylene terephthalate microplastics (PET-MPs) are one of pivotal nondegradable emerging pollutant. Here the variation of the surface physicochemical characteristics of PET-MPs with UV irradiation aging and the adsorption behaviors of PET-MPs in malachite green (MG), tetracycline (TC) solution and the effect of coexisting Cu(II) were comparatively investigated. The yellowing, weakened hydrophobicity, and increased surface negative charge, crystallinity degree and oxygen-containing functional groups were manifested specifically by the aged PET-MPs. Different from the single system, the hydrophobic interaction and metal ion bridging complexation dominated the adsorption of MG and TC, respectively, in the binary solution. While in the ternary solution, cationic ion competition of Cu(II) with MG decreased its capture, and the formation of PET-Cu(II)-TC ternary complexes promoted TC adsorption. Moreover, PET-MPs could serve as an efficient vector for MG and TC in MG/TC/Cu(II) ternary system, indicating PET-MPs tend to carry more varieties in the complex environment, that may increase the environmental risk of PET-MPs.

Review of emerging contaminants in green stormwater infrastructure: Antibiotic resistance genes, microplastics, tire wear particles, PFAS, and temperature

Green stormwater infrastructure is a growing management approach to capturing, infiltrating, and treating runoff at the source. However, there are several emerging contaminants for which green stormwater infrastructure has not been explicitly designed to mitigate and for which removal mechanisms are not yet well defined. This is an issue, as there is a growing understanding of the impact of emerging contaminants on human and environmental health. This paper presents a review of five emerging contaminants - antibiotic resistance genes, microplastics, tire wear particles, PFAS, and temperature - and seeks to improve our understanding of how green stormwater infrastructure is impacted by and can be designed to mitigate these emerging contaminants. To do so, we present a review of the source and transport of these contaminants to green stormwater infrastructure, specific treatment mechanisms within green infrastructure, and design considerations of green stormwater infrastructure that could lead to their removal. In addition, common removal mechanisms across these contaminants and limitations of green infrastructure for contaminant mitigation are discussed. Finally, we present future research directions that can help to advance the use of green infrastructure as a first line of defense for downstream water bodies against emerging contaminants of concern.