Chitin is an abundant biopolymer whose natural production is second only to cellulose. Similar to cellulose nanocrystals (CNCs) or nanofibers (CNFs), chitin nanofibers (ChNFs) can be isolated and used as sustainable O 2 barrier materials for food, electronics, and pharmaceutical packaging. These bioavailable nanomaterials are readily dispersed in water enabling spray-coated films to be deposited at high rates onto uneven or delicate surfaces. In the present study, we demonstrate the successful layer-by-layer spray coating of cationic ChNF and anionic CNC suspensions onto poly(lactic acid) (PLA) films. ChNF/CNC multilayers were found to lead to a reduction in the O 2 permeability of the final composite film by as much as 73% with the largest effects seen in composites with three alternating layers (ChNF-CNC-ChNF). Multilayer ChNF/CNC coatings were found to have lower O 2 permeability and lower haze than those coated with ChNF or CNCs alone (72% and 86% lower haze, respectively), pointing to a synergistic effect. The composites had a water vapor transmission rate similar to the PLA substrate.

Hunger and chronic undernourishment impact over 800 million people, which translates to ≈10.7% of the world's population. While countries are increasingly making efforts to reduce poverty and hunger by pursuing sustainable energy and agricultural practices, a third of the food produced around the globe still is wasted and never consumed. Reducing food shortages is vital in this effort and is often addressed by the development of genetically modified produce or chemical additives and inedible coatings, which create additional health and environmental concerns. Herein, a multifunctional bio‐nanocomposite comprised largely of egg‐derived polymers and cellulose nanomaterials as a conformal coating onto fresh produce that slows down food decay by retarding ripening, dehydration, and microbial invasion is reported. The coating is edible, washable, and made from readily available inexpensive or waste materials, which makes it a promising economic alternative to commercially available fruit coatings and a solution to combat food wastage that is rampant in the world.

Meteorological and air-quality model simulations are analyzed alongside observations to investigate the role of the Chesapeake Bay breeze on surface air quality, pollutant transport, and boundary layer venting. A case study was conducted to understand why a particular day was the only one during an 11-day ship-based field campaign on which surface ozone was not elevated in concentration over the Chesapeake Bay relative to the closest upwind site and why high ozone concentrations were observed aloft by in situ aircraft observations. Results show that southerly winds during the overnight and early-morning hours prevented the advection of air pollutants from the Washington, D.C., and Baltimore, Maryland, metropolitan areas over the surface waters of the bay. A strong and prolonged bay breeze developed during the late morning and early afternoon along the western coastline of the bay. The strength and duration of the bay breeze allowed pollutants to converge, resulting in high concentrations locally near the bay-breeze front within the Baltimore metropolitan area, where they were then lofted to the top of the planetary boundary layer (PBL). Near the top of the PBL, these pollutants were horizontally advected to a region with lower PBL heights, resulting in pollution transport out of the boundary layer and into the free troposphere. This elevated layer of air pollution aloft was transported downwind into New England by early the following morning where it likely mixed down to the surface, affecting air quality as the boundary layer grew.

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Chitin nanofibers (ChNFs) and cellulose nanocrystals (CNCs) have been proposed as materials for renewable packaging with low O 2 transmission that protect food, medicine, and electronics. A challenge in biomass-derived functional materials is tuning both barrier and mechanical properties, while minimizing process steps. A concept that merits additional study in this field is tuning of the barrier and mechanical properties by use of oppositely charged biomass-derived fibers, through interactions that support dense film formation. We report free-standing films formed by solution casting of blends of aqueous suspensions of CNCs and ChNFs with either low degree of acetylation (LChNFs, higher charge) or high degree of acetylation (HChNFs, lower charge). While neat CNC films had the highest O 2 permeability (OP), the OP was lowered by 91% by addition of at least 25 wt % LChNFs to CNCs to an OP value near 1.7 cm 3 μm/m 2 /d/ kPa. Interestingly, blends of CNCs with less highly charged, larger HChNFs had equivalently lower OP as with LChNFs. The tensile strength and strain at break of blended ChNF/CNC films was optimal compared to neat cellulose or chitin when at least 50 wt % LChNFs or HChNFs were blended with CNCs. We show that the ability to tune properties of ChNF/CNC blends was coincident with the formation of aggregates of chitin and cellulose nanomaterials, which appear to support formation of dense layers of tortuous fiber networks.