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China has witnessed extensive development of the marine aquaculture industry over recent years. However, such rapid and disordered expansion posed risks to coastal environment, economic development, and biodiversity protection. This study aimed to produce an accurate national-scale marine aquaculture map at a spatial resolution of 16 m, using a proposed model based on deep convolution neural networks (CNNs) and applied it to satellite data from China's GF-1 sensor in an end-to-end way. The analyses used homogeneous CNNs to extract high-dimensional features from the input imagery and preserve information at full resolution. Then, a hierarchical cascade architecture was followed to capture multi-scale features and contextual information. This hierarchical cascade homogeneous neural network (HCHNet) was found to achieve better classification performance than current state-of-the-art models (FCN-32s, Deeplab V2, U-Net, and HCNet). The resulting marine aquaculture area map has an overall classification accuracy > 95 % (95.2 %–96.4, 95 % confidence interval). And marine aquaculture was found to cover a total area of ∼ 1100 km 2 (1096.8–1110.6 km 2 , 95 % confidence interval) in China, of which more than 85 % is marine plant culture areas, with 87 % found in the Fujian, Shandong, Liaoning, and Jiangsu provinces. The results confirm the applicability and effectiveness of HCHNet when applied to GF-1 data, identifying notable spatial distributions of different marine aquaculture areas and supporting the sustainable management and ecological assessments of coastal resources at a national scale. The national-scale marine aquaculture map at 16 m spatial resolution is published in the Google Maps kmz file format with georeferencing information at 10.5281/zenodo.3881612 (Fu et al., 2020). [ABSTRACT FROM AUTHOR]

China has witnessed extensive development of the marine aquaculture industry over recent years. However, such rapid and disordered expansion posed risks to coastal environment, economic development, and biodiversity protection. This study aimed to produce an accurate national-scale marine aquaculture map at a spatial resolution of 16 m, using a proposed deep convolution neural networks (CNNs) based model and applied it to satellite data from China's GF-1 sensor in an end-to-end way. The analyses used homogeneous CNNs to extract high-dimensional features from the input imagery and preserve information at full resolution. Then, a hierarchical cascade architecture was followed to capture multi-scale features and contextual information. This hierarchical cascade homogeneous neural network (HCHNet) was found to achieve better classification performance than current state-of-the-art models (FCN-32s, Deeplab V2, U-Net, and HCNet). The resulting marine aquaculture area map has an overall classification accuracy > 95 % (95.2 %-96.4, 95 % confidence interval). And marine aquaculture was found to cover a total area of ~1100 km2 (1096.8 km2-1110.6 km2, 95 % confidence interval) in China, of which more than 85 % are marine plant culture areas, with 87 % found in the Fujian, Shandong, Liaoning, and Jiangsu provinces. The results confirm the applicability and effectiveness of HCHNet when applied to GF-1 data, identifying notable spatial distributions of different marine aquaculture areas and supporting the sustainable management and ecological assessments of coastal resources at a national scale. The national-scale marine aquaculture map at 16 m spatial resolution is published in the Google Maps kmz File Format with georeferencing information at https://doi.org/10.5281/zenodo.3881612 (Fu et al., 2020). [ABSTRACT FROM AUTHOR]

The reserve of rare-earth element-bearing phosphorite ores in Guizhou province in western China is huge. Increased demand for the different products manufactured from rare-earth elements has resulted in an extreme need for reasonable and comprehensive extraction of rare-earth elements. An improved understanding of rare-earth element occurrence states in single minerals of ores is important for their further processing. In this paper, rare-earth element contents were analyzed by inductively coupled plasma (ICP), and the occurrence states in single minerals were further investigated through SEM-EDS and focused ion beam-scanning electron microscope (FIB-SEM) methods. The results indicate that rare-earth element contents of apatite are far more than that of dolomite. No independent mineral of rare-earth elements exists for the studied sample. Rare-earth elements are present in the form of ions in the lattices of apatite. Based on the analysis of occurrence states and properties in single minerals, the distribution of rare-earth elements in the flotation process was investigated by reverse flotation technology. It shows that rare-earth elements are mainly concentrated in apatite concentrate. Under the optimized conditions, the P2O5 grade increases from 11.36% in the raw ore to 26.04% in the concentrate, and the recovery is 81.92%, while the total rare-earth oxide grade increases from 0.09% to 0.21% with the recovery of 80.01%, which is similar to P2O5 recovery. This study presents the feasibility of extracting rare-earth elements from rare-earth element-bearing phosphorite ores through the flotation of apatite. [ABSTRACT FROM AUTHOR]

Ecosystem water use efficiency (WUE describes carbon-water flux coupling in terrestrial ecosystems. Understanding response and resilience of WUE to drought are essential for sustainable water resource and ecosystem management under increasing drought risks over China due to climate warming. Here we analyzed the response of ecosystem WUE to drought (spatiotemporal variability and resilience) over China during 1982–2015 based on an evapotranspiration (ET) dataset based on the model tree ensemble (MTE) algorithm using flux-tower ET measurements and satellite-retrieved GPP data. The results showed that the multiyear average WUE was 1.55 g C kg−1 H2O over China. WUE increased in 77.1% of Chinese territory during the past 34 years. During drought periods, the ecosystem WUE increased mainly in the northeast of Inner Mongolia, Northeast China and some regions in southern China with abundant forests but decreased in northwestern and central China. An apparent lagging effect of drought on ecosystem WUE was observed in the east of Inner Mongolia and Northeast China, the west and east regions of North China and the central part of Tibetan Plateau. Some ecosystems (e.g., deciduous needle-leaf forests, deciduous broadleaf forests, evergreen broadleaf forests and evergreen needle-leaf forests) in Central China, Northeast and Southwest China exhibited relatively greater resilience to drought than others by improving their WUE. Our findings would provide useful information for Chinese government to adopt a reasonable approach for maintaining the structure and functions of ecosystems under drought disturbance in future. [ABSTRACT FROM AUTHOR]

The European Space Agency (ESA) Climate Change Initiative (CCI) project combines multi-sensors at different microwave frequencies to derive three harmonized soil moisture products using active, passive and combined approaches. These long-term soil moisture products assist in understanding the global water and carbon cycles. However, extensive validations are a prerequisite before applying the retrieved soil moisture into climatic or hydrological models. To fulfill this objective, we assess the performances of three CCI soil moisture products (active, passive and combined) with respect to in-situ soil moisture networks located in China, Spain and Canada. In order to compensate the scale differences between ground stations and the CCI product's coarse resolution, we adopted two upscaling approaches of Inverse Distance Weighting (IDW) interpolation and simple Arithmetic Mean (AM). The temporal agreements between the satellite retrieved and ground-measured soil moisture were quantified using the unbiased root mean square error (ubRMSE), RMSE, correlation coefficients (R) and bias. Furthermore, the temporal variability of the CCI soil moisture is interpreted and verified with respect to the Tropical Rainfall Measuring Mission (TRMM) precipitation observations. The results show that the temporal variations of CCI soil moisture agreed with the in-situ ground measurements and the precipitation observations over the China and Spain test sites. In contrast, a significant overestimation was observed over the Canada test sites, which may be due to the strong heterogeneity in soil and vegetation characteristics in accordance with the reported poor performance of soil moisture retrieval there. However, despite a retrieval bias, the relatively temporal variation of the CCI soil moisture also followed the ground measurements. For all the three test sites, the soil moisture retrieved from the combined approach outperformed the active-only and passive-only methods, with ubRMSE of 0.034, 0.050, and 0.050–0.054 m3/m3 over the test sites in China, Spain and Canada, respectively. Thus, the CCI combined soil moisture product is suggested to drive the climatic and hydrological studies. [ABSTRACT FROM AUTHOR]

Application of nitrogen (N) fertilizer increases grain yield and soil organic carbon (SOC) sequestration, but accompanied by the emission of greenhouse gas (GHG) especially nitrous oxide (N 2 O). To spatial-temporally analyze the trade-off between yield and GHG emissions under different N fertilization levels at regional scale, this study integrated geographic information system (GIS) and the DeNitrification-DeComposition (DNDC, Version 9.5) model to define the impacts of different N fertilization levels on rice production, SOC sequestration, and GHG emission in Fuyang District, a county-scale region in Eastern China. The whole region was divided into 28825 polygon-based modeling units based on heterogeneity of soil property, climate and agricultural management conditions. After validating the DNDC model by field observation data of the year 1979 and 2015, five N fertilization levels (0, 140, 210, 280 and 350 kg N ha−1) from the year 2016–2035 were designed for simulating the rice yield, SOC sequestration, N 2 O and methane (CH 4) emissions. Validation results showed a good performance of the refined DNDC model. Simulation results indicated that yield and GHG emission increased with the growth of N fertilization rate, but the SOC sequestration change was not noticeable. Around 210 kg N ha−1 was recommended as optimal N fertilization level in Fuyang District, because its global warming potential intensity (GWPI) was the lowest among all the N fertilization levels. As excessive N input is a common problem across China, our results provide a case for a win-win scenario for both food security and environmental friendliness. • Increasing N fertilization level makes the growth of yield as well as GHG emission. • The reduction of yield can be compensated by the decline of N 2 O emission. • Yield growth and carbon sequestration potential are influenced by the soil type. • 25 percent reduction of N fertilization is suggested in the study area. [ABSTRACT FROM AUTHOR]

To extend the utilization of the low-grade Human (China) sepiolite, the purification of the ore is the prerequisite for all applications. Sepiolite accompanied by quartz and calcite was effectively purified via sedimentation method and the microwave assisted acid treatment. The influence of treatment time on sepiolite purity and structure was qualitatively studied based on XRD and FESEM. Sepiolite had been successfully purified and the content was elevated from 42 wt.% to more than 90 wt.%. Microwave assisted acid treatment demonstrated to be an effective purification process by removing carbonates without affecting sepiolite length. Furthermore, both physical method of lyophilization and chemical method of surface modification were proposed as simple alternatives to defibering acid-treated sepiolite crystal bundles. The effects of freezing time and surfactant chain length on the disaggregation state, micro-structure and properties of treated sepiolite were analyzed comparatively using FESEM, TEM and BET. Results of FESEM and TEM indicated that the crystal structure of sepiolite was not changed after freezing at − 50 °C for 12 h or modification with hexadecyl trimethyl ammonium bromide (HDTMA), but the aggregates were effectively disaggregated. The BET specific surface areas of the dispersed sepiolite rods obtained by these two methods increased to 144.3 and 93.1 m 2 /g, respectively, showing good agreement with the perfect dispersion of sepiolite fibers. [ABSTRACT FROM AUTHOR]