Highly cross-linked and organic-inorganic hybrid poly(cyclotriphosphazene-co-curcumin) microspheres (PCPC-MS) were facilely prepared by a one-step precipitation copolymerization method, and served as a fluorescent chemical sensor for the detection of picric acid (PA) in solution phase. The photochemically inert cyclotriphosphazene moieties intentionally introduced into the structure of the sensor could play a role not only in connecting curcumin fluorophores to construct a highly cross-linked fluorescent architecture with excellent thermal stability and photobleaching stability, but also in effectively enriching PA from bulk solution to the surface of the sensor by the acid-base interaction between the acidic phenolic hydroxyl groups of PA molecules and the electron-rich nitrogen atoms of the cyclotriphosphazene units, which might facilitate the formation of a ground-state non-fluorescent complex of the microspheres and PA as well as the excited-state energy transfer from the microspheres to PA. Therefore, PCPC-MS exhibited a fluorescence quenching response towards PA with high sensitivity, efficiency, and selectivity over a number of other analytes such as 2,4,6-trinitrotoluene, 2,4dinitrotoluene, 1,3-dinitrobenzene, 4-nitrotoluene, nitrobenzene, 4-benzoquinone, chlorobenzene, and nitromethane in methanol. In addition, PCPC-MS could also effectively detect PA in the presence of the other analytes, indicating their remarkable ability for resisting interferences and specific recognition of PA. This study provides new insights into the design and preparation of a polymer-based fluorescence chemical sensor for PA with low toxicity, a simple preparation process, and high selectivity.

Microplastics pollution is a hotspot for researchers in recent years worldwide, for the large quantities of plastics in production and the resistance of degradation. China microplastics pollution attracts high attention because of the long coastline, large population and rapid economic development. This review addresses the widespread microplastics pollution in China water ecosystem through available research results in recent years and analyses the abundance, characteristics, fate and risk of microplastics. This paper also discusses the current treatment technology of microplastics. The conclusions show that the estuary area is a severely affected region of microplastics pollution; the accumulation of microplastics and adsorption of contaminants by microplastics could also lead to serious risks besides ingestion; there are few technologies that can efficiently remove microplastics pollution in sewage treatment plants. Finally, this review gives opinions in the future research trends.

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A sub-surface forest fire is a kind of fire that spreads slowly with no flames and lower temperatures, and threatens the ecosystem and human life. The moisture content of humus is considered to be an important factor in determining fire occurrence and sustaining. The humus of the Larix gmelinii in the Daxing’an Mountains was selected for the experiment, the limit moisture content condition of sub-surface forest fires was determined by an experiment simulating smoldering, and the prediction model of the probability of sub-surface forest fire occurrence was established. The results will be of great significance for the prevention, monitoring, and fighting of sub-surface forest fires in the boreal forest. The results showed that when the moisture content of humus in the upper layer was low, the smoldering process could be self-sustaining at 20%. For deeper layers of a depth of 18 cm, this increased to 30% moisture content of the humus and was the critical depth for sub-surface fires. The moisture content of 40% was a limit to burning where smoldering can only last for a short duration and is then extinguished. When the moisture content of the humus was 20%, the smoldering temperature was higher and the rate of spread was faster, with smoldering being maintained for longer periods at 30% moisture content. The regression prediction model of the highest temperature and vertical rate of spread in a column of humus was correlated to moisture content and depth, and the model significance was good at p < 0.01. Based on moisture content and depth, the occurrence probability prediction model of sub-surface fires has a good correlation (R2 = 0.93) and high prediction accuracy (AUC = 0.995). The effect of moisture content (Or = 4.008) on the occurrence probability of sub-surface fires is higher than that of depth (Or = 2.948). The results point out that it is necessary to prevent and monitor the occurrence of sub-surface fires when the humus moisture content is less than 40%. In order to reduce the risk of sub-surface fires, the monitoring time of the fire field should be extended after the fire is extinguished due to the slow-burning process of the sub-surface fire. Increasing the moisture content of the humus is an important method to reduce the probability and restrain the spread of sub-surface fires.