Recycling and value-added utilization of agricultural residues through combining technologies such as anaerobic digestion and pyrolysis could double the recoverable energy, close the nutrient recycle loop, and ensure cleaner agricultural production. This study assessed the beneficial application of biochar to soil to recycle digestate nutrients, improve soil quality, and reduce conventional chemical fertilizer. The addition of digestate-enriched biochar improved soil quality as it provided higher soil organic matter (232%–514%) and macronutrients (110%–230%) as opposed to the unenriched biochar and control treatments. Maize grown in soil amended with digestate-enriched biochar showed a significantly higher biomass yield compared to the control and non-enriched biochar treatments but was slightly lower than yields from chemical fertilizer treatments. The slightly lower yield (20%–25%) achieved from digestate-enriched biochar was attributed to slower mineralization and release of the adsorbed nutrients in the short term. However, digestate-enriched biochar could in the long term become more beneficial in sustaining soil fertility through maintaining high soil organic matter and the gradual release of micronutrients compared to conventional chemical fertilizer. Positive effects on soil micronutrients, macronutrients, organic matter, and biomass yield indicates that enriched biochar could partly replace chemical fertilizers and promote organic farming in a circular economy concept.

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Extensive studies have been carried out on the impact of human activities on air pollution, but systematic investigation on the relationship between air pollutant and meteorological conditions is still insufficient, especially in the context of China’s site scale and recent comprehensive environmental pollution control. Here, we used a spatial interpolation technology to establish a set of data sets of pollutants and meteorological elements that are spatially matched at 896 stations in China to reveal the air pollutant-meteorological interactions between 2014 and 2019. We found that air pollution and meteorological elements have obvious seasonal and regional characteristics. Over the last few years, the concentration of most air pollutants in China has dropped significantly except for O 3 . The increase in O 3 concentration was closely related to the decrease of particulate matter and NO 2 concentration. The concentration of most air pollutants was affected by meteorological conditions, but the level of impact depended on the type of pollutants and varied across regions. The concentration of air pollutants at most stations was significantly negatively correlated with wind speed, precipitation and relative humidity, but positively correlated with atmospheric pressure. As the latitude increases, the impact of temperature on the concentration of air pollutants becomes more obvious. To effectively control air pollution, it is further urgent to reveal the relationship between air pollution and meteorological conditions based on long-term daily or real-time data.

Achieving nanocomposites with simultaneous highly anisotropic thermal and electrical conductivities using carbon materials remains challenging as carbon material tends to form random networks in nanocomposites. Here, highly anisotropic and flexible graphene@naphthalenesulfonate (NS)/poly(vinyl alcohol) (GN/PVA) nanocomposites were fabricated using a layer-by-layer scraping method with flat graphene as the starting functional filler. NS acted as a bond bridge for linking the graphene (π−π interaction) and PVA (hydrogen bond). The results showed well-dispersed graphene in the nanocomposites while maintaining flat morphology with uniform in-plane orientation. The as-fabricated nanocomposites exhibited highly anisotropic thermal and electrical conductivities. The in-plane and out-of-plane thermal conductivities of the nanocomposite prepared with 10.0 wt % graphene reached 13.8 and 0.6 W m −1 K −1 , and in-plane and out-of-plane electrical conductivities were 10 −1 and 10 −10 S cm −1 , respectively. This indicated highly anisotropic thermal and electrical conductivities. Furthermore, the nanocomposites showed elevated flexibility and tensile strength from 42.0 MPa for pure PVA to 110.0 MPa for GN-5.0 wt %/PVA. In sum, the proposed strategy is effective for the preparation of nanocomposites with high flexibility, as well as superior anisotropic thermal and electrical conductivities.