Search

The widespread occurrence of N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPD-Q) in aquatic environments and its hazards to aquatic species underscore the necessity of comprehending its environmental fate. Here, we investigated the transformation from 6PPD to 6PPD-Q and the attenuation of 6PPD-Q in surface water under natural conditions. Contrary to prior findings, this work revealed that 6PPD-Q and its precursor 6PPD-OH/6PPD-(OH)2, were not detected through target analysis and suspect screening during 6PPD transformation in the surface water under the natural conditions. 6PPD-Q predominantly accumulated in TWPs in ambient atmosphere with 1.28 % mass yield from the 6PPD dissipation. Subsequently, 6PPD-Q was eluted from TWPs and released to the water environment. The investigation on the natural attenuation of 6PPD-Q in the surface water demonstrated that direct and indirect photolysis facilitated the rapid dissipation of 6PPD-Q with a half-life of 2.57 h. Utilizing the liquid chromatography high resolution mass spectrometry (LC-HRMS), including both time of flight (TOF) MS and Orbitrap MS, twelve novel transformation products (TPs) of 6PPD-Q were identified by using a comprehensive non-targeted screening strategy. The results from two dimensions gas chromatography (GC×GC) TOF-MS revealed additional two TPs. Based on the molecular structure of TPs, four major pathways of 6PPD-Q attenuation were proposed, including bond cleavage, hydroxylation, quinone cleavage and rearrangement. All TPs were predicted to exhibit lower toxicity, indicating the natural attenuation of 6PPD-Q reduced its toxicity and potential environmental risks. This study provides crucial insights into the environmental fate of 6PPD-Q, highlighting the significance of understanding both its formation from 6PPD and its subsequent attenuation processes under natural conditions.

The effects of microalgal biofouling on microplastic (MP) may differ from bacterial biofouling. In this study, the influence of microalgae on MP surface alteration, structural change, and adsorption of organic micropollutants was evaluated. Virgin polyethylene (PE), polyvinyl chloride (PVC), and polyamide (PA) were each immersed in algal photobioreactor and river freshwater for 30 days to simulate algal and river microbe biofouling respectively. Consequently, their physicochemical changes and adsorption potential of a mixture of six bisphenol analogues (BPA, BPS, BPE, BPB, BPF, BPAF) and two parabens (propyl–paraben, benzyl–paraben) were investigated. Owing to the algal bioactive compounds, major microalgae-induced biofouling and more MP aging than the river microbe aging were observed through fractures, pits, cracks, and algal attachments. Intrusion of algal organic matter and scission of polymeric functional groups were revealed during microalgal immersion and the potential MP aging pathways were proposed. Algal biofouling considerably altered the intrinsic properties of the MPs, consequently the adsorption capacity of PE and PVC was enhanced by 3.04–6.72 and 2.14–8.72 times, respectively. Adsorption process onto algal-aged MPs was pH-dependent, endothermic, non-spontaneous, and favored by hydrogen bonds. Meanwhile, the amide group in PA structure was conducive to organic micropollutant adsorption, which was likely reduced by algal aging and the erosion of the N-H stretching. Moreover, higher adsorption capacities of organic micropollutants were shown by the algal-biofilm PE and PVC than virgin and river microbial biofilm MPs. This study discloses that, biofouling and aging of MPs by microalgae through their bioactive components would engender more incidences on MP properties, organic micropollutants adsorption with associated environmental and health hazards.