Citrinin (CIT), a known nephrotoxic mycotoxin, is mainly produced by Penicillium, Aspergillus, and Monascus species. It is a natural contaminant in cereal grains, foods, and feedstuff. Liupao tea (or Liubao tea) is a typical Chinese dark tea obtained via indigenous tea fermentation facilitated by microorganisms. Certain fungi present in Liupao tea that may produce CIT are a potential threat to consumer health. In the present study, various potential toxigenic mycoflora and the natural occurrence of CIT in Liupao tea were surveyed via the culture-dependent method, high performance liquid chromatography−fluorescence detection (HPLC− FLD), and ultrahigh performance liquid chromatography−tandem mass spectrometry (UHPLC−MS/MS). Total mold counts ranged from 3.5 × 10 2 CFU/g to 2.1 × 10 6 CFU/g tea in 28 tea samples. A total of 218 fungal isolates belonging to five genera and 23 species were identified. Some of these strains, such as Aspergillus ochraceus, Aspergillus oryzae, Penicillium citrinum, and Penicillium chrysogenum, may potentially be a CIT-producing species. In addition, 32.7% of 113 Liupao tea samples were contaminated with CIT at concentrations ranging from 7.8 to 206.1 μg/kg. These CIT concentrations in Liupao tea are chiefly attributed to climatic conditions and water activity during storage that favor fungal proliferation and mycotoxin production. However, CIT could not be detected in Liupao tea stored for over 10 years. These results provide the first information about the potential toxigenic mycoflora and natural occurrence of CIT in Liupao tea. Therefore, storage conditions and fungal community must be monitored to ensure the quality of Liupao tea.

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Nanoparticles can undergo aging phenomena that change their physical and chemical properties in sewage treatment systems. However, the effect of aged nanoparticles under long-term low concentrations on the dewatering performance of activated sludge in sewage treatment systems has not been reported yet. Here, we compared the chronic effects of pristine and aged TiO 2 nanoparticles on sludge dewatering index including speci c resistance to ltration (SRF) and bound water (BW) in the sequencing batch reactor (SBR) with the µg/L concentration levels and the relevant mechanisms were analyzed. The results show that the aging experiment in sludge supernatant could change the photosensitivity and water stability of nanoparticles, which was mainly due to the changes in the zeta potential and energy band of the particle, and ultimately attributed to the combined effect of particle surface inclusions such as organic matter and inorganic salt. At 10µg/L, nanoparticles could reduce the dewaterability of sludge, but at 100µg/L, nanoparticles could improve the dewaterability of sludge, because 10µg/L promoted the secretion of extracellular polymeric substance (EPS), regulated the structure of sludge ora and increased the abundance of secreting quorum sensing-acyl-homoserine lactones (QS-AHL) and EPS genera, while the corresponding exposure results of 100µg/L were the opposite, due to the damage and necrosis exposure effects of 100µg/L under long-term light, which reduced EPS production and increased sludge density. Interestingly, aging could alleviate the effects of two exposure concentrations on sludge dewatering, mainly being attributed to the decrease of the photoactivity of nanoparticles. The results of this study show that environmental aging could slow down, but cannot reverse the results of exposure to speci c concentrations of nanoparticles. However, the ecological effects of photosensitive nanoparticles with two environmentally-relevant concentration levels of ug/L were signi cantly different, which should be re ned and con rmed again in freshwater environment to provide a basis for subsequent scienti c management and control of photosensitive nanoparticles.

Nanoparticles can undergo aging phenomena that change their physical and chemical properties in sewage treatment systems. However, the effect of aged nanoparticles under long-term low concentrations on the dewatering performance of activated sludge in sewage treatment systems has not been reported yet. Here, we compared the chronic effects of pristine and aged TiO2 nanoparticles on sludge dewatering index including specific resistance to filtration (SRF) and bound water (BW) in the sequencing batch reactor (SBR) with the µg/L concentration levels and the relevant mechanisms were analyzed. The results show that the aging experiment in sludge supernatant could change the photosensitivity and water stability of nanoparticles, which was mainly due to the changes in the zeta potential and energy band of the particle, and ultimately attributed to the combined effect of particle surface inclusions such as organic matter and inorganic salt. At 10µg/L, nanoparticles could reduce the dewaterability of sludge, but at 100µg/L, nanoparticles could improve the dewaterability of sludge, because 10µg/L promoted the secretion of extracellular polymeric substance (EPS), regulated the structure of sludge flora and increased the abundance of secreting quorum sensing-acyl-homoserine lactones (QS-AHL) and EPS genera, while the corresponding exposure results of 100µg/L were the opposite, due to the damage and necrosis exposure effects of 100µg/L under long-term light, which reduced EPS production and increased sludge density. Interestingly, aging could alleviate the effects of two exposure concentrations on sludge dewatering, mainly being attributed to the decrease of the photoactivity of nanoparticles. The results of this study show that environmental aging could slow down, but cannot reverse the results of exposure to specific concentrations of nanoparticles. However, the ecological effects of photosensitive nanoparticles with two environmentally-relevant concentration levels of ug/L were significantly different, which should be refined and confirmed again in freshwater environment to provide a basis for subsequent scientific management and control of photosensitive nanoparticles.