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Spatio-temporal distributions of air pollution and population are two important factors influencing the patterns of mortality and diseases. Past studies have quantified the adverse effects of long-term exposure to air pollution. However, the dynamic changes of air pollution levels and population mobility within a day are rarely taken into consideration, especially in metropolitan areas. In this study, we use the high-resolution PM 2.5 data from the micro-air monitoring stations, and hourly population mobility simulated by the heatmap based on Location Based Service (LBS) big data to evaluate the hourly active PM 2.5 exposure in a typical Chinese metropolis. The dynamic "active population exposure" is compared spatiotemporally with the static "census population exposure" based on census data. The results show that over 12 h on both study periods, 45.83% of suburbs' population-weighted exposure (PWE) is underestimated, while 100% of rural PWE and more than 34.78% of downtown's PWE are overestimated, with the relative difference reaching from -11 μg/m 3 to 7 μg/m 3 . More notably, the total PWE of the active population at morning peak hours on weekdays is worse than previously realized, about 12.41% of people are exposed to PM 2.5 over 60 μg/m 3 , about twice as much as that in census scenario. The commuters who live in the suburbs and work in downtown may suffer more from PM 2.5 exposure and uneven environmental resource distribution. This study proposes a new approach of calculating population exposure which can also be extended to quantify other environmental issues and related health burdens., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Antibiotic concentrations in surface waters far exceed the pollution limit due to the abuse of pharmaceuticals, resulting in an urgent need for an approach with potential efficiency, sustainability and eco-friendliness to remove antibiotic pollutants. A novel biochar-based nanomaterial was synthesized by hydrothermal synthesis and was investigated for its removal potential for tetracycline hydrochloride (TC) from both artificial and real wastewater. The associative facilitation between biochar and g-MoS 2 nanosheets was proposed, revealing the favorable surface structures and adsorption properties of the composite. The related adsorption kinetics, isotherms and thermodynamics were studied by several models with adsorption experimental data, turning out that biochar decorated by g-MoS 2 exhibited optimum TC removal with adsorption capacity up to 249.45 mg/g at 298 K. The adsorption behavior of TC molecules on g-MoS 2 -BC can be interpreted well by three-step process, and it is dominated by several mechanisms containing pore-filling, electrostatic force, hydrogen bond and π-π interaction. In addition, the cost-effective g-MoS 2 -BC nanocomposites demonstrated excellent adsorption and recycling performance in TC-contaminated river water, which might provide the underlying insights needed to guide the design of promising approach for contaminant removal on a large scale in practical application., (Copyright © 2018. Published by Elsevier B.V.)