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Nanocrystalline cellulose (NCC) prepared via sulfuric acid hydrolysis was used as raw material. The nanocrystalline cellulose was graft-modified by long-chain fatty acids including lauric acid, palmitic acid, and stearic acid in a FeSO4/H2O2 oxidation–reduction system at low temperature. Modified nanocrystalline cellulose (MNCC) was obtained through above process. Crystalline structure and microstructure of the MNCC were analyzed and characterized. To explore the surface activities of the MNCC, contact angle, surface tension, critical micelle concentration (CMC) and hydrophile–lipophile balance (HLB) values were tested. Results showed that water contact angles of lauric acid-, palmitic acid-, and stearic acid-nanocrystalline cellulose were 79.3°, 82.5° and 84.8°, and HLB values were 15.78, 16.29 and 16.81, respectively. The CMC of the MNCC was 12.5 mg/L. The MNCC had good hydrophilic and lipophilic properties. It was a kind of non-ionic natural macromolecule surfactants and could replace traditional surfactants as emulsifiers and solubilizers.

Widespread and long-lasting drought disasters can aggravate environmental degradation. They can lead to significant economic losses and even affect social stability. The existing drought index mostly chose arid and semi-arid regions as study areas, because cloudy weather in humid and semi-humid regions hindered the satellite in its attempts to obtain the surface reflectivity. In order to solve this problem, a cloudy region drought index (CRDI) is proposed to estimate the drought of the clouded pixels. Due to the cumulative effect of drought, the antecedent drought index (ADI) has a certain impact on the calculation of the current drought. Furthermore, cloud is the only source of natural precipitation, and it also affects the evaporation and emission process on the ground. Therefore, based on the remote sensing drought index, ADI and cloud optical thickness (COT) are used to estimate the drought of pixels with missing data due to cloud occlusion. In this paper, a case study of the cloudy Guangdong, which is located in a humid area, is presented. First, we calculated the CRDI using Moderate Resolution Imaging Spectroradiometer (MODIS) data from 2003 to 2017, and then discussed the effect of CRDI with the data from 2016 as examples. Through the analysis of the parameters of regression equation, filling efficiency, rationality of the estimated value, the continuity of CRDI and the rationality of CRDI spatial distribution results, it is concluded that CRDI can effectively estimate the drought severity of the cloud-covered pixels, and more comprehensive drought data can be obtained by using CRDI. The successful application of CRDI in Guangdong shows it is robust and flexible, suggesting high efficiency and great potential for further utilization.

The DisTrad (Disaggregation Procedure for Radiometric Surface Temperature) model shows limited applicability for sub-pixel mapping of thermal remote-sensing images in densely vegetated areas due to...

In this study, we updated the hydrological data from the 1950s to 2012 and analysed the temporal variations in the hydrological series of the Pearl River using the wavelet transform method. Furthermore, we quantified the climatic and anthropogenic effects on the changes in the hydrological processes in the Pearl River. The results of the combined methods of the wavelet transform method and the Mann-Kendall (MK) trend test (i.e., wavelet trend test) reveal that the water discharge series exhibited a statistically insignificant changing trend since the 1950s; however, the sediment load series displayed a statistically significant decreasing trend. Comparisons of the results of the MK trend test and the wavelet trend test indicate that annual and inter-annual periodic oscillations affect the trend changes in the hydrological series. Statistical analysis and the double mass curve indicate that climatic change dominates changes in water discharge, such as the El Nino Southern Oscillation (ENSO), and human activities were mainly responsible for the phase changes in the sediment load. From 1973 to 1986, deforestation in the basin dominated the sediment variability and caused 83.2% of the increase in the sediment load compared to the reference period of 1957–1972. Even though water and soil conservation projects have been carried out since the early 1990s, the vegetation cover in the catchment area decreased by 6.5 × 10 4 km 2 from the late 1980s to the late 2000s, as detected by Landsat TM images, and water and soil conservation projects had little effect on the sediment reduction. Since the 1990s, dam construction has dominated sediment variability. Compared to the reference period, the sediment load due to dam construction decreased by 83.4 kg/s and 993.3 kg/s in the periods of 1987–1998 and 1998–2006, respectively, and the reduction in the sediment load increased to 1329.5 kg/s in the period of 2007–2012, indicating the intensifying impact of dam construction on the sediment reduction. The sediment sources in the Pearl River basin have changed, and scouring of the river channel has become a new sediment source in response to dam construction. The alteration of hydrological processes in the Pearl River will continue to occur in the future in the context of global climatic change, which is becoming increasingly important for river management in the Pearl River basin.

This paper presents an improved Dark Dense Vegetation (DDV) method for retrieving 500 m-resolution aerosol optical depth (AOT) based on MOD04-C005 arithmetic with the Moderate Resolution Imaging Spectroradiometer (MODIS) from the National Aeronautics and Space Administration (NASA). The improvements include change of the movement pattern of retrieval window, selection of a more suitable aerosol type, and storage of the look-up table. The method is then applied to obtain the AOT over the Pearl River Delta region (PRD). By comparing the results with the co-temporal ground sunphotometer observations in 2010, the correlation coefficient is found to be 0.794 with RMSE 0.139 and their variations remain consistent. Contrasts between model values in 2008 and MODIS AOT products in the same date also reveal a high accuracy of the improved DDV method. We also performed sensitivity tests to analyze the impacts of several parameters on apparent reflectance at different bands, and the results show that apparent reflectance is much more sensitive to surface reflectance and AOT than to elevation.

A hybrid inversion method that combines a Bayesian Network Classifier (BNC) with shape adaptive neighborhoods (SANs) is proposed for the classification of 10-m resolution remote sensing images. BNC uses a directed acyclic graph (DAG) to describe variable relationships. We define feature bands and land use/cover types as the feature and class variables, respectively, and describe them as nodes in the DAG. BNC only uses the posterior probability of the class node, and predicts the class with the highest posterior probability. A SAN, containing spectral, textural, and shape features, is used to study the Bayesian network structure, in contrast to methods which only use spectral features. The classification results of the proposed SAN-BNC are compared with those of the spectral-based Maximum Likelihood Classifier (MLC), the SAN-based MLC, and the SAN-based Support Vector Machine (SVM) using Guangzhou as a case study. Our results show that BNC and SVM have superior inference abilities relative to MLC. Ten meter resolution images will furnish better classification results using the proposed SAN-BNC procedure.

The spatiotemporal evolution of sea ice of Bohai Sea in the 2009–2010 winter was studied by time-series remote sensing data, and real-time meteorological data in combination with cumulative freezing degree days (CFDD). Sea ice acreage was determined using a ratio-threshold segmentation together with visual interpretation of daily MODIS 250 m imagery. We found the sea ice acreage soared to 31,849 km2 on January 23, covering 40.8% of the Bohai Sea. But on February 12, it reached 26,700 km2 in Liaodong Bay only, covering almost 90.0% of Liaodong Bay. The rapid formation and expansion of sea ice was caused by continuous cold snaps superimposed on a background of anomalously cold weather. CFDD calculated from surrounding cities highly correlated with sea ice acreage in Liaodong Bay (R 2 = 0.72) suggesting CFDD is one of the significant controlling factors. Sea ice expansion showed 7 days lag with respect to the lowest temperature from surrounding coastal cities, and it mainly occurred close to land, along the coastline, and gradually expanded from the shore outwards.

Three simple models estimating the evapotranspiration fraction (EF) were tested, validated and compared with available data from NDVI/albedo and day–night land surface temperature difference (DT). They were analyzed using ground based measurements collected by the energy balance Bowen ratio system at the 11 enhanced facilities located at the Southern Great Planes of the USA between April 2001 and May 2005. One model was superior in predicting the EF. It used an extension of the Priestly–Taylor equation and a relation between the normalized difference vegetation index (NDVI) and DT.

Satellite remote sensing offers an effective approach to estimate indicators of air quality on a large scale. It is critically significant for air quality monitoring in areas experiencing rapid urbanization and consequently severe air pollution, like the Pearl River Delta (PRD) in China. This paper starts with examining ground observations of particulate matter (PM) and the relationship between PM10 (particles smaller than 10 μm) and aerosol optical thickness (AOT) by analyzing observations on the sampling sites in the PRD. A linear regression (R2 = 0.51) is carried out using MODIS-derived 500 m-resolution AOT and PM10 concentration from monitoring stations. Data of atmospheric boundary layer (ABL) height and relative humidity are used to make vertical and humidity corrections on AOT. Results after correction show higher correlations (R2 = 0.55) between extinction coefficient and PM10. However, coarse spatial resolution of meteorological data affects the smoothness of retrieved maps, which suggests high-resolution and accurate meteorological data are critical to increase retrieval accuracy of PM. Finally, the model provides the spatial distribution maps of instantaneous and yearly average PM10 over the PRD. It is proved that observed PM10 is more relevant to yearly mean AOT than instantaneous values.

In this study, soil erosion in the Guangdong, China during 2012 was quantitatively assessed using Universal Soil Loss Equation (USLE). The parameters of the model were calculated using GIS and MODIS data. The spatial distribution of the average annual soil loss on grid basis was mapped. The estimated average annual soil erosion in Guangdong in 2012 is about 2294.47t/ (km2.a). Four high sensitive area of soil erosion in Guangdong in 2012 was found. The key factors of these four high sensitive areas of soil erosion were significantly contributed to the land cover types, rainfall and Economic development and human activities.

Cross radiometric calibration is an effective method of no-ground-site calibration of remote sensors through building the relationship between the radiance of the reference sensor with higher radiometric accuracy and the experimental sensor, which can avoid the disadvantages of ground-site calibration — higher cost and longer update cycle of calibration coefficients. In this paper, the visible and near-infrared spectral bands of HJ-1B/CCD1 are cross-calibrated through the Ray-Matching method (RM) using the corresponding bands of Aqua/MODIS with higher radiometric accuracy and the TM image at a similar time is used to validate our results. Compared with the results by the coefficients of the satellite, the cross-calibration results by RM method are desirable and the error is acceptable, showing higher accuracy and effectiveness.