In food packaging industry, plastic was the most commonly used material for packaging, which caused serious pollution to the marine and soil environment. The researches on biodegradable films development from biodegradable polymers was arise, which was expected to ensure the quality and safety of food as much as possible. Biodegradable materials for films included polysaccharides and proteins of different biological sources, and synthetic materials. This review discussed the molecular characteristics and film-forming properties of natural polymer materials of polysaccharides from halobios, plant and microorganism, protein from animal, plant, milk. In addition, the effects of polymerization degree, crystallinity, and film-forming process of synthetic materials (polycaprolactone, polyvinyl alcohol, polylactic acid) on film performance was studied. In order to improve the practicality of biodegradable films in food packaging, many methods were explored to enhance the physical performance of the films. The enhancement strategies including: introduction of nanoparticles, chemical modification, and blending with other polymers, which can effectively enhance the mechanical properties and water vapor barrier performance of biodegradable films. Furthermore, it will provide a reference for future research interest that to development biodegradable food packaging films with high mechanical and barrier properties.

Unlike many biopolymers, alpha-1,3-glucan (alpha-1,3-GLU) is water-insoluble, making it a promising candidate for the production of moisture-resistant films with applications in biodegradable packaging, biomedicine, and cosmetics. This study aimed to characterize the structural, physicochemical (water affinity, optical, mechanical), and biodegradation properties of a film made from alpha-1,3-GLU extracted from Laetiporus sulphureus. The film was fabricated through alkaline dissolution, casting, drying, washing to remove residual NaOH, and re-plasticization with a glycerol solution. FTIR and Raman spectroscopy confirmed the polysaccharide nature of the film, with predominant alpha-glycosidic linkages. The film exhibited a semi-crystalline structure and high opacity due to surface roughness resulting from polymer coagulation. Owing to re-plasticization, the film showed a high moisture content (similar to 47%), high water solubility (81.95% after 24 h), and weak mechanical properties (tensile strength = 1.28 MPa, elongation at break approximate to 10%). Its water vapor permeability (53.69 g mm m(-2) d(-1) kPa(-1)) was comparable to other glycerol-plasticized polysaccharide films reported in the literature. The film supported the adhesion of soil microorganisms and target bacteria and was susceptible to degradation by Trichoderma harzianum and endo- and exo-alpha-1,3-glucanases, indicating its biodegradability. The limitations in its mechanical strength and excessive hydration indicate the need for improvements in the composition and methods of producing alpha-1,3-GLU films.

The objective of the present work was to investigate the effect of CMC biopolymer on the physicochemical, mechanical, thermal, barrier, and biodegradation properties of PVA-based films. The polymeric films were developed using solution casting method, incorporating CMC at concentrations ranging from 0.5 to 1.5%. With the addition of CMC, the tensile strength (TS) of the hybrid films was reduced from 1.40 +/- 0.02 MPa to 1.99 +/- 0.02 MPa. However, there was a significant improvement in the elongation at break (EAB) up to 49.29% compared to PVA film. The addition of CMC resulted in substantial improvements in water vapor permeability (WVP) and moisture retention capacity (MRC), showcasing a 38.73% improvement in WVP and a satisfactory MRC of 78.374% at 0.5% CMC concentration. The hybrid films also exhibit enhanced light absorbance at UV wavelength with opacity ranging from 0.301 to 1.413. TGA analysis showed a notable enhancement in the decomposition temperature of the hybrid PVA/CMC films, resulting in reduced mass loss compared to the PVA film. FTIR spectra confirmed that blending CMC with PVA led to the formation of strong hydrogen bonds within the polymer blend, significantly affecting the intermolecular forces inside the cellulose matrix. Moreover, with the addition of CMC, the degradation rate of the PVA/CMC film was increased approximately to 40% on the 30th day of soil burial. The films also exhibit effective microbial degradation against Pseudomonas putida and Bacillus subtilis bacteria strains as compared to commercial plastics. Overall, the obtained results validate the use of CMC biopolymer for blending of single polymer system as well as scaling down the extensive use of petroleum-based polymers in the field of packaging.

The present work investigates the development and characterization of cellulose acetate (CA) films with varying concentrations of CA, incorporating glycerol as a plasticizer and calcium chloride (CaCl2) as a crosslinker. The films were fabricated using solution casting and phase inversion techniques. The inclusion of glycerol significantly enhanced the surface morphology, tensile strength (TS), and elongation at break (EAB) of the films. The optimal composition, containing 10% (w/v) CA and 1% (v/v) glycerol, achieved the highest TS (3.199 +/- 0.077 MPa) and EAB (9.500% +/- 0.401%). The addition of CaCl2 to CA resulted in improved thermal properties of the films, suggesting effective crosslinking between CA and glycerol, as demonstrated by the DSC and TGA analyses. FTIR analysis suggested that glycerol interacts with cellulose, through hydrogen bonding, modifying the intermolecular forces within the cellulose matrix. Glycerol also improved the films' hydrophilicity and reduced swelling, solubility, and water contact angle (WCA). The films also exhibited antimicrobial properties against Staphylococcus aureus (S. aureus), a gram-positive bacterium, and achieved a soil biodegradation rate of 43.65% within 30 days. These results suggest that CA films with optimized glycerol and CaCl2 are promising for various industrial and medical applications where enhanced mechanical properties, permeability control, and biodegradability are essential.

Cellulose micro-nanofibrils (CMNF) with different fibrillation levels were partially acetylated while preserving their morphological and native crystalline structure. The morphological changes due to fibrillation and chemical modification were observed using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and optical profilometry. The change in tensile and burst strength, barrier, and biodegradability profile were investigated which revealed that the mechanical properties of the unmodified CMNF films increased with increase in extent of fibrillation. However, the mechanical strength of the acetylated film decreased with the increase in degree of acetylation. The stretching or folding property of the film increased with the increase in both the fibrillation and acetylation. The contact angle value increased due to a higher degree of fibrillation and acetylation because they increased the hydrophobicity and consequently enhanced the air and water vapor resistance of the unmodified and modified CNF films. Furthermore, all films exhibited the highest resistance against oil and grease, and the biodegradability test substantiated that CNF films were compostable in soil. In total, this work expresses new pathways to enhance the barrier properties of biodegradable CNF films by regulating the degree of fibrillation and acetylation, thus can emerge as sustainable alternatives for packaging and agriculture applications.

Salt damage caused by the complex interaction between water and salt in the heritages is the main factor that deteriorates the materials and destroys the historical information of the relics. The influence of environmental conditions, especially humidity, on salt damage of heritages has been emphasized by many researches. In this study, the water-salt migration characteristics in soil columns under different humidity were studied by laboratory tests. First, water vapor adsorption test was carried out to investigate the soil samples adsorption capability in 6 relative humidity conditions (RH11%, RH23%, RH43%, RH60%, RH75%). There is a linear relation between relative humidity and water vapor absorbed by soil, and the water vapor adsorption curves of samples can be well described by first-order exponential attenuation equation. Second, the water content and conductivity distribution within samples (hygroscopic and non-hygroscopic samples respectively) were investigated after capillary migration tests using 4 types of saline solutions (0.2 mol/L NaCl, 0.2 mol/L Na2SO4, 0.2 mol/L NaCl Na2SO4 mixed solution and distilled water). Results show that high conductivity appears on the top of most samples, and the values have a correlation with type of capillary migration fluid: NaCl > Na2SO4 > NaCl-Na2SO4 > H2O. In addition, the distribution of water content and conductivity becomes complicated under different relative humidity conditions.

The northernmost margin of the East Asian summer monsoon (NMEASM) is the northernmost position that the East Asia summer monsoon (EASM) can reach. NMEASM has obvious multi-scale variability, and well reflects the wet/dry climate variability in northern China. Predicting the location change of the NMEASM is important for understanding future East Asian climate change. However, the variability of the NMEASM has not been studied extensively, and its underlying mechanisms have not been clarified. To explore the movement of the NMEASM and its causes, we use reanalysis datasets to evaluate the NMEASM index from 1979 to 2018. The NMEASM indicates a decreasing trend over 40 years and a significant abrupt point in 2000, which is positively correlated with the Tibetan Plateau snow cover before 2000 and the Siberian snow cover after 2000 in spring. The decreased Siberian snow cover increases the soil temperature and decreases the atmospheric baroclinicity over Mongolia and northern China after 2000. The decreased atmospheric baroclinicity induces the dipole mode of anticyclonic anomaly over Mongolia and northern China and the cyclonic anomaly over the Sea of Japan by modulating the wave activity flux (WAF). The WAF's southeastward propagation strengthens the anticyclonic anomaly over Mongolia and northern China and the cyclonic anomaly over the Sea of Japan, which weakens the upward movement and water vapor transport, respectively. Hence, the decreased Siberian snow cover in spring modulates the precipitation over Mongolia and northern China and the southward movement of NMEASM by turbulent westerly circulation.

Climate changes significantly impact the hydrological cycle. Precipitation is one of the most important atmospheric inputs to the terrestrial hydrologic system, and its variability considerably influences environmental and socioeconomic development. Atmospheric warming intensifies the hydrological cycle, increasing both atmospheric water vapor concentration and global precipitation. The relationship between heavy precipitation and temperature has been extensively investigated in literature. However, the relationship in different percentile ranges has not been thoroughly analyzed. Moreover, a percentilebased regression provides a simple but effective framework for investigation into other factors (precipitation type) affecting this relationship. Herein, a comprehensive investigation is presented on the temperature dependence of daily precipitation in various percentile ranges over the Qinghai-Tibet Plateau. The results show that 1) most stations exhibit a peaklike scaling structure, while the northeast part and south margin of the plateau exhibit monotonic positive and negative scaling structures, respectively. The scaling structure is associated with the precipitation type, and 2) the positive and negative scaling rates exhibit similar spatial patterns, with stronger (weaker) sensitivity in the south (north) part of the plateau. The overall increase rate of daily precipitation with temperature is scaled by Clausius-Clapeyron relationship. 3) The higher percentile of daily precipitation shows a larger positive scaling rate than the lower percentile. 4) The peak-point temperature is closely related to the local temperature, and the regional peak-point temperature is roughly around 10 degrees C.

The spatiotemporal characteristics of aerosol direct radiative forcing (RF) and the relative contributions from aerosol species, as well as the impacts of cloud coverage and relative humidity on aerosol direct RF were quantified in East Asia using a regional climate model. Generally, the total aerosol produces net RFs of -12.78 W m- 2 at surface, 1.72 W m- 2 at TOA (top-of-atmosphere), and atmospheric heating of 14.50 W m- 2. It was found that dust, black carbon, and sulfate made dominant contributions to the total RF at surface and TOA, and all aerosol species induced atmospheric heating, whereas more than 96% of which was induced by dust and black carbon. The remarkably seasonally decreasing tendency of the total and the absorbing aerosol RFs was found from spring to winter at surface. Moreover, dust contributes relatively larger to the positive TOA RF and to the atmospheric heating in spring and summer, which were weakened and smaller than black carbon in other seasons. Sensitivity studies further demonstrated cloud strengthens the dust and black carbon direct RF and weakens the other species direct RF at TOA, while induces weak direct RFs of all aerosol species at surface. Particularly, cloud induced larger reduction in dust longwave RF than shortwave leads to remarkable enhanced net surface direct RF of dust, especially in JJA. The aerosol swelling effect induced by relative humidity strengthens aerosol direct RF at both TOA and surface. The percentage changes in aerosol RF and its seasonal amplitude by cloud are considered larger at TOA than surface, however, the effects of relative humidity distribute relatively uniform vertically. Meteorological factors impact on scattering aerosols direct RF is assumed larger than absorbing aerosols. The impacts of cloud on aerosol direct RF are compared to the relative humidity and are supposed to be more important at TOA and surface.

Due to the extreme, harsh natural environment in the Himalayas higher than 8000 m above sea level (asl) long-term and continuous meteorological observation is still a great challenge, and little is known about water vapor transport in this extremely high region. Based on the Automatic Weather Stations (AWSs) at 3810 m, 5315 m, 6464 m, 7945 m and 8430 m asl on the southern slope of Mt. Everest, this study investigates the meteorological characteristics and water vapor transport in the Mt. Everest region from June 2019 to June 2021. The results show that (1) with the increase of altitude, the temperature lapse rate becomes deeper from -4.7 degrees C km(-1) to -8.1 degrees C km(-1); (2) the relative humidity increases significantly in summer, and precipitation during the monsoon period accounts for more than 70% of the annual total; and (3) during the monsoon in 2020, the number of days with negative daily water vapor divergence in the whole layer accounted for 31% at the height from ground to 350 hPa, and the moisture amount transported through water vapor convergence was about 122 mm. The study indicates that, with sufficient moisture supply, strong water vapor convergence and a relatively large vertical velocity, a small amount of water vapor can climb to an extreme height and be transported from the southern to the northern slope of the Himalayas.