Unveiling Small-Sized Plastic Particles Hidden behind Large-Sized Ones in Human Excretion and Their Potential Sources.

Health risks of microplastic exposure have drawn growing global concerns due to the widespread distribution of microplastics in the environment. However, more evidence is needed to understand the exposure characteristics of microplastics owing to the limitation of current spectrum technologies, especially the missing information on small-sized particles. In the present study, laser direct infrared spectroscopy and thermal desorption-gas chromatography-mass spectrometry combined pyrolysis using a tubular furnace (TD-GC/MS) were employed to comprehensively detect the presence of plastic particles down to 0.22 µm in human excreted samples. The results showed that polyethylene (PE), polyvinyl chloride, PE terephthalate (PET), and polypropylene dominated large-sized (>20 µm) and small-sized plastic plastics (0.22-20 µm) in feces and urine. Moreover, fragments accounted for 60.71 and 60.37% in feces and urine, respectively, representing the most pervasive shape in excretion. Surprisingly, the concentration of small-sized particles was significantly higher than that of large-sized microplastics, accounting for 56.54 and 50.07% in feces (345.58 µg/g) and urine (6.49 µg/mL). Significant positive correlations were observed between the level of plastic particles in feces and the use of plastic containers and the consumption of aquatic products (Spearman correlation analysis, p < 0.01), suggesting the potential sources for plastic particles in humans. Furthermore, it is estimated that feces was the primary excretory pathway, consisting of 94.0% of total excreted microplastics daily. This study provides novel evidence regarding small-sized plastic particles, which are predominant fractions in human excretion, increasing the knowledge of the potential hazards of omnipresent microplastics to human exposure.

Effects of soil properties on the remediation of diesel-contaminated soil by Triton X-100-aided washing.

Although nonionic surfactant is widely used for petroleum-contaminated soil washing, there is no definite conclusion on the main soil factors which determine the removal of petroleum hydrocarbons from the soil. In this study, the influences of soil properties on Triton X-100-aided soil washing were investigated using 12 soils in China. The sorption characteristic of Triton X-100 on soils was described as well. The sorption isotherms of Triton X-100 on 12 typical soils were fitted to the Langmuir adsorption model, and the maximum sorption amount of Triton X-100 (Qmax) varied from 1.54 to 15.15 mg/g. The removal rates of diesel for 12 soils were well fitted to the modified Michaelis-Menten equation, and the maximum removal rate of diesel (φmax) ranged from 62.92 to 90.36%. The correlation analysis indicated that the φmax is significantly correlated with the Qmax. The soil factors affecting diesel removal from soils followed the order of sand content > cation exchange capacity (CEC) > organic matter (OM) content > silt and clay content > SSA >> pH. The prediction model based on CEC, silt content, and pH explained 83.1% of variance of diesel removal from soils. This study will have important implication for successfully remediating organic-contaminated soil using nonionic surfactant-based soil washing.