Microplastic polystyrene foam has been found widely in the environment and is readily transported by wind or water. Beached and virgin foams of size 0.45e1 mm were prepared as sorbents to study oxytetracycline sorption. Enhanced adsorption were found in the beached foams compared to the virgin foams, corresponding to the higher specific surface area, micropore area and the degree of oxidation of the former. The Freundlich K f value was 894 ± 84 ((mg kg À1 ) (mg L À1 ) 1/n ) for oxytetracycline adsorption on the beached foams, approximately twice as high as on the virgin foams. Effects of solution pH on adsorption to the beached foams were more pronounced to the virgin foams. Maximum adsorption occurred at pH 5 at which electrostatic repulsion between the microplastic surface and the oxytetracycline zwitterion was minimal, indicating that electrostatic interaction may have regulated adsorption. Moreover, H-bonding and multivalent cationic bridging mechanisms may also have affected the adsorption of oxytetracycline to the beached foams as reflected by the ionic effects. Adsorption was promoted more in the presence of humic acid than of fulvic acid, perhaps owing to p-p conjugation between the humic acid and the microplastic surface which led to enhanced electrostatic attraction for oxytetracycline. This study suggests that weathered polystyrene foams may act as carriers of antibiotics in the environment and their potential risks to ecosystem and human health merit further investigation.

No abstract

No abstract

The chromate ore process residues (COPR) polluted soil was physically separated into coarse sand (2.000-0.425 mm), fine sand (0.425-0.053 mm) and silt to clay (< 0.053 mm) fractions. The Cr speciation was characterized by synchrotron based micro X-ray fluorescence (µ-XRF) and micro X-ray absorption near-edge spectra (µ-XANES). The results indicated that Cr was bearing both in COPR parent minerals and hydrated products and was dominated by Cr(III) in three size-fractions. The synchrotron results indicated that Cr(III) was dominated by chromite, organic matter bound Cr(III) and particle adsorbed Cr in the selected hotspots from the coarse sand, fine sand and silt to clay sized fraction, respectively. While Cr(VI) occurred in the form of CrO in the selected hotspots from three size fractions. The difference of Cr(III) species in the size-fractions suggested that higher edaphic effects occurred in the fine size-fractions than in the coarse size-fraction for the weathered COPR.