Impacts of plastic film mulching on crop yields, soil water, nitrate, and organic carbon in Northwestern China: A meta-analysis

In order to increase crop yield in semi-arid and arid areas, plastic film mulching (PFM) is widely used in Northwestern China. To date, many studies have addressed the effects of PFM on soil physical and biochemical properties in rain-fed agriculture in Northwestern China, but the findings of different studies are often contradictory. Therefore, a comprehensive review of the impacts of PFM on soil water content, soil nutrients and food production is needed. We compiled the results of 1278 observations to evaluate the overall effects of PFM on soil water content, the distribution of nitrate and soil organic carbon, and crop yield in rain-fed agriculture in Northwestern China. Our results showed that PFM increased soil moisture and nitrate concentration in topsoils (0–20 cm) by 12.9% and 28.2%, respectively, but slightly decreased (1.8%) soil organic carbon (SOC) content in the 0–10 cm soil layer. PFM significantly increased grain yields by 43.1%, with greatest effect in spring maize (79.4%). When related to cumulative precipitation during the crop growing season, yield increase from PFM was greatest (72.8%) at 200–300 mm, which was attributed to the large increase for spring maize and potato, implying that crop zoning would be beneficial for PFM in this region. When related to N application rate, crop yields benefited most from PFM (80.2%) at 200–300 kg/ha. A cost-benefit analysis indicated that PFM increased economic return by an average of 29.5%, with the best improvement for spring maize (71.1%) and no increase for spring wheat. In conclusion, PFM can significantly increase crop yield and economic return (especially for spring maize) in rain-fed agriculture areas of Northwestern China. Crop zoning is recommended for PFM to achieve the largest economic benefit. However, full account needs to be taken of the environmental impacts relating to N loss, SOC depletion and film pollution to evaluate the sustainability of PFM systems and further research is required to quantify and mitigate these impacts

Unveiling the Effects of Solvent Polarity within Graphene Based Electric Double-Layer Capacitors

Solvents have been considered to show a profound influence on the charge storage of electric double-layer capacitors (EDLCs). However, the corresponding mechanisms remain elusive and controversial. In this work, the influences of solvent dipole moment on the EDL structures, kinetic properties, and charging mechanisms of graphene-based EDLCs are investigated with atomistic simulations. Specifically, electrolyte structuring is conspicuously modulated by solvents, where a sharp increment of capacitance (~325.6%) and kinetics (~10-fold) is documented upon the slight descent of polarity by ~33.0%. Unusually, such an impressive enhancement is primarily attributed to the suppressed interfacial electric fields stimulated by strong-polarity solvents in the proximity of electrodes, which goes beyond the previously observed issues that stemmed from the competitive interplays between ions and solvents. Moreover, a distinctive polarity-dependent charging mechanism (i.e., from pure counterion adsorption to coion desorption) is identified, which for the first time delineates the pivotal role of solvent polarity in manipulating the charge storage evolutions. The as-obtained findings highlight that exploiting the solvent effects could be a promising avenue to further advance the performances of EDLCs

Unveiling the Effects of Solvent Polarity within Graphene Based Electric Double-Layer Capacitors

Solvents have been considered to show a profound influence on the charge storage of electric double-layer capacitors (EDLCs). However, the corresponding mechanisms remain elusive and controversial. In this work, the influences of solvent dipole moment on the EDL structures, kinetic properties, and charging mechanisms of graphene-based EDLCs are investigated with atomistic simulations. Specifically, electrolyte structuring is conspicuously modulated by solvents, where a sharp increment of capacitance (~325.6%) and kinetics (~10-fold) is documented upon the slight descent of polarity by ~33.0%. Unusually, such an impressive enhancement is primarily attributed to the suppressed interfacial electric fields stimulated by strong-polarity solvents in the proximity of electrodes, which goes beyond the previously observed issues that stemmed from the competitive interplays between ions and solvents. Moreover, a distinctive polarity-dependent charging mechanism (i.e., from pure counterion adsorption to coion desorption) is identified, which for the first time delineates the pivotal role of solvent polarity in manipulating the charge storage evolutions. The as-obtained findings highlight that exploiting the solvent effects could be a promising avenue to further advance the performances of EDLCs

Evaluating Water Supply Risk in the Middle and Lower Reaches of Hanjiang River Basin Based on an Integrated Optimal Water Resources Allocation Model

The rapid socio-economic development and expanding human-induced hydrological alteration have strengthened the interactions between the social and hydrologic systems. To assess regional water supply security under changing water supply and demand condition in strongly human-impacted area, an integrated water resources management model that fully incorporates water demand prediction, optimal water resources allocation and water supply risk analysis is proposed and applied in the mid-lower reach of Hanjiang River basin. The model is run under three scenarios considering increasing water demand and expanding water diversion projects, and then spatial and temporal distributions of water supply reliability and vulnerability are evaluated. Results show that water supply risk in the mid-lower reach of Hanjiang River basin, especially units that take water directly from the mainstream, will be gradually enlarged in the future due to the expansions of both water demand and inter-basin water diversion capacity. The proposed method provides a practical approach towards more robust decision-making of long-term water resources planning and management under changing environment