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Microalgae-based wastewater treatment could realize simultaneous nutrients recovery and CO₂ sequestration. However, impacts of environmental microplastics (MPs) and antibiotic co-exposure on microalgal growth, nutrients removal, intracellular nitric oxide (NO) accumulation and subsequent nitrous oxide (N₂O) emission are unclarified, which could greatly offset the CO₂ sequestration benefit. To reveal the potential impacts of environmental concentrations of MPs and antibiotic co-exposure on microalgal greenhouse gas mitigation, this study investigated the effects of representative MPs (PE, PVC, PA), antibiotic sulfamethoxazole (SMX), and nitrite (NO₂^--N) in various combinations on attached Chlorella sorokiniana growth, nutrients removal, anti-oxidative responses, and N₂O emission originated from intracellular NO build-up. Microalgal biofilm growth was more inhibited under 10 μg/L MPs than 100 μg/L SMX, and MPs+SMX co-exposure displayed toxicity antagonism while MPs+MPs co-exposure caused toxicity synergism (up to 66 % growth inhibition). Extracellular polysaccharides content correlated well with microalgal biofilm density under various stresses, while SMX involved stresses displayed chlorophyll a content reduction. Microalgal assimilation and MPs adsorption contributed to nutrients removal, and phosphorus removal displayed less variance among different stresses (residual phosphorus <0.5 mg/L) than nitrogen. Intracellular NO conversion to N₂O almost doubled during the co-exposure processes, and N₂O emission under NO₂^--N + PE+PVC co-exposure could offset the contribution of microalgal CO₂ sequestration by as high as 176.2 %. Results of this study appealed for urgent concern regarding environmental MPs and antibiotic co-exposure on primary producers' growth characteristics and their greenhouse gas mitigation properties.

In this study, a pyrolysis-gas chromatography/mass spectrometry method was established to quantify microplastics (MPs) released from plastic food containers during rinsing and migration. The inner surface of actual samples was rinsed with deionized water, and the MPs in rinse water were collected through a glass fiber membrane with pore size of 1 μm. Subsequently, thoroughly cleaned polypropylene (PP) food packaging containers were selected for migration tests under different simulants, migration temperatures, and migration times. It was found that MPs corresponding to the materials of product manufacture were detected in all collected containers during rinsing. By migration tests, the results showed that high-fat foods, high/low temperature (5 °C), and long exposure periods can promote the release of MPs. It was also proved that the migration of MPs from plastic food containers was one of the important sources for human exposure to MPs. The obtained results can provide evidence for the safety risk assessment of plastic food containers.