Abstract:Forest evapotranspiration is one of the main components in the regional water budget. A comparison between measured and estimated eddy covariance (EC) data, considering the Katerji-Perrier (KP), Todorovic (TD) and Priestley-Taylor (PT) actual evapotranspiration methods, was carried out. These models, relying on more easily obtainable data, are valuable when long-term direct measurements are not available. The objective of this paper is to compare the effectivity of these three models. In this paper, experimental data were obtained within the temperate mixed forest of broad-leaved and coniferous trees of the Changbai Mountains in northeastern China during the growing seasons of 2003 to 2005. The KP method gave the most effective values for half-hourly and daily evapotranspiration computed by summing up half-hourly estimates, and the TD method overestimated evapotranspiration by about 30%. The diurnal courses of estimated and measured evapotranspiration showed bell curves, similar to that of net radiation, except for a slight increase at about 14 : 30 solar time due to a peak value of vapour pressure deficit (VPD). For the case of daily evapotranspiration using daily mean micrometeorological variables, the PT method presented the closest values to the measurements. Accuracy of estimation related to VPD negatively (especially for VPD >1Ð5 kPa). The KP parameters, considered to be vegetation dependent, were a D 0Ð545 and b D 1Ð31 at the experimental site. A constant PT parameter (˛D 1Ð18) was applied to estimated evapotranspiration. Daily values of˛responded to VPD (negatively) more strongly than to soil moisture (positively) in this forest. The experiment showed the inherent limits and advantages of the three methods. The KP method, a semi-empirical approach, was preferred to estimate half-hourly evapotranspiration. The TD method was a mechanistic approach to estimate reference evapotranspiration and always overestimated actual evapotranspiration. The PT method, being site dependent and the simplest approach, was effective enough to estimate large time-scale (at least daily) evapotranspiration.

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A new solar energy storage system is designed and synthesized based on phase-changing microcapsules incorporated with black phosphorus sheets (BPs). BPs are 2D materials with broad light absorption and high photothermal performance, which are synthesized and covalently modified with poly(methyl methacrylate) (PMMA) to produce the PMMA-modified BPs (mBPs). With the aid of PMMA, the mBPs and phase-changing materials (PCM, eicosane) are encapsulated together to form microcapsules. The microencapsulated eicosane and mBPs (mBPs-MPCM) composites exhibit a high latent heat of over 180 kJ kg −1 , good thermal reliability, as well as excellent photothermal characteristics inherited from BPs. Owing to the direct contact in the integrated mBPs-MPCM composites, the thermal energy generated by mBPs is transferred to eicosane immediately giving rise to three times higher efficiency in solar energy storage compared to microcapsules with mBPs on the surface. The mBPs-MPCM composites have great potential in solar energy storage applications and the concept of integrating photothermal materials and PCMs as the core provides insights into the design of high-efficiency solar energy storage materials. Solar energy is one of the most important renewable energy sources in the continuous efforts to meet the ever-increasing global energy demand [1,2] and techniques that capture solar

Burning is one of the most widely used methods for removing crop residues during harvest seasons. It cleans fields faster and costs less in comparison to other residue removal methods. Agricultural burning, however, has been recently limited or banned during harvest seasons in China, mainly due to the air quality and human health concerns raised from its use. This paper reviews recent studies on the burning of agricultural landscapes in China to understand the natural (environmental and ecological) and human (economic and social) impacts and identifies uncertainties, gaps, and future research needs. The total annual crop straw output in China is more than 600 billon kg, with about 110, 130, and 230 billion kg coming from rice, wheat, and corn, respectively. Agricultural burning removes about one-fourth of total crop straw and emits about 140-240, 1.6-2.2, and 0.5-0.14 billion kg of CO 2 , PM 2.5 , and black carbon, respectively. Agricultural burning accounts for upto half of the total PM 10 concentrations in the major burning regions during harvesting periods. Burning emissions contribute to regional haze and smog events. Therefore, limiting or banning agricultural burning is a necessary measure for reducing air pollution in China. The estimations of total burned crop straw amounts and emission factors are the major uncertainty sources for emission estimates. More studies are needed to better describe the smoke plume rise, dispersion, and interactions with weather and climate and to simulate the ecological impacts of agricultural burning. Effective alternatives need to be explored in order to provide solutions for farmers to remove agricultural residues in the wake of the burning ban.

Controversial results in the drying and wetting trends were found with different indices and potential evapotranspiration calculations in previous studies. Here we make an attempt to find robust conclusions of drying and wetting trends over regions by coherent results of various independent indices by using China (1961–2012) as a study area. Precipitation, statistical, and physical drought indices, including the Standardized Precipitation Evapotranspiration Index (SPEI) and the Palmer Drought Severity Index (PDSI) and self‐calibrating PDSI (sc_PDSI), with both the Penman‐Monteith (PM) and Thornthwaite (TH) approaches in PDSI calculation are considered. In consequence, four PDSI variants of PDSI_pm, sc_PDSI_pm, PDSI_th, and sc_PDSI_th are involved. To illustrate regional characteristics, six climatic regions based on the Köppen climate classification are defined. At the national scale, precipitation and SPEI indicate wetting trends but all PDSI variants have drying trends. On the other hand, these six indices exhibit coherent results in five of these six regions. Increases in wetness occur in arid region and the Qinghai‐Tibet Plateau. Drying trends were found in semiarid and cold and temperate semihumid regions. Only the humid region in southeastern China is seen to have increasing precipitation and SPEI and decreasing PDSI variants. From the perspective of climatic regions, the drying trends mainly occur in the transition regions between the humid and arid regions in China. The spatial pattern of changes in droughts could be categorized by climatic zones, and the changes at regional scale are robust based on these six indices.

Abstract. It has been proposed that increasing levels of pCO2 in the surface ocean will lead to more partitioning of the organic carbon fixed by marine primary production into the dissolved rather than the particulate fraction. This process may result in enhanced accumulation of dissolved organic carbon (DOC) in the surface ocean and/or concurrent accumulation of transparent exopolymer particles (TEPs), with important implications for the functioning of the marine carbon cycle. We investigated this in shipboard bioassay experiments that considered the effect of four different pCO2 scenarios (ambient, 550, 750 and 1000 μatm) on unamended natural phytoplankton communities from a range of locations in the northwest European shelf seas. The environmental settings, in terms of nutrient availability, phytoplankton community structure and growth conditions, varied considerably between locations. We did not observe any strong or consistent effect of pCO2 on DOC production. There was a significant but highly variable effect of pCO2 on the production of TEPs. In three of the five experiments, variation of TEP production between pCO2 treatments was caused by the effect of pCO2 on phytoplankton growth rather than a direct effect on TEP production. In one of the five experiments, there was evidence of enhanced TEP production at high pCO2 (twice as much production over the 96 h incubation period in the 750 μatm treatment compared with the ambient treatment) independent of indirect effects, as hypothesised by previous studies. Our results suggest that the environmental setting of experiments (community structure, nutrient availability and occurrence of phytoplankton growth) is a key factor determining the TEP response to pCO2 perturbations.

The development of digital economy affects environmental pollution emission and green sustainable development. However, the relationship between digital economy and industrial wastewater discharge has rarely been examined. This study establishes the urban digital economy evaluation index system, measures the digital economy indexes of 281 prefecture-level cities in China from 2011 to 2016, and examines the impact effect of digital economy development on industrial wastewater discharge using the system generalized method of moment method and the intermediary effects model. The empirical results indicate that the digital economy reduces the industrial wastewater discharge. As evidence shows, the digital economy significantly promotes the upgrading of industrial structure, which is an important factor affecting the industrial wastewater discharge. Additionally, the inhibiting effect of digital economy on industrial wastewater discharge is more significant in big cities. This study provides a scientific base and guidance for reducing environmental pollution emissions and promoting the development of digital economy.

Although perovskite wafers with a scalable size and thickness are suitable for direct X‐ray detection, polycrystalline perovskite wafers have drawbacks such as the high defect density, defective grain boundaries, and low crystallinity. Herein, PbI2‐DMSO powders are introduced into the MAPbI3 wafer to facilitate crystal growth. The PbI2 powders absorb a certain amount of DMSO to form the PbI2‐DMSO powders and PbI2‐DMSO is converted back into PbI2 under heating while releasing DMSO vapor. During isostatic pressing of the MAPbI3 wafer with the PbI2‐DMSO solid additive, the released DMSO vapor facilitates in situ growth in the MAPbI3 wafer with enhanced crystallinity and reduced defect density. A dense and compact MAPbI3 wafer with a high mobility‐lifetime (µτ) product of 8.70 × 10−4 cm2 V−1 is produced. The MAPbI3‐based direct X‐ray detector fabricated for demonstration shows a high sensitivity of 1.58 × 104 µC Gyair−1 cm−2 and a low detection limit of 410 nGyair s−1.