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Accurately tracking the changes in rice cropping intensity is a critical requirement for policymakers to formulate reasonable land-use policies. Southern China is a traditional region for rice multi-cropping, yet less is known about its spatial–temporal changes under the background of rapid urbanization in recent decades. Based on images from Landsat and MODIS and multiple land cover products, the gap-filling and Savitzky–Golay filter method (GF-SG), the enhanced pixel-based phenological features composite approach (Eppf-CM), random forest (RF), and the difference in NDVI approach (DNDVI) were combined to map the rice cropping pattern with a spatial resolution of 30 × 30 m over Southern China in 2000 and 2020 through Google Earth Engine (GEE). Subsequently, the spatial–temporal changes in rice cropping intensity and their driving factors were examined by Getis-Ord Gi* and geographical detector. The results showed that the produced rice cropping pattern maps exhibited high accuracy, with kappa coefficients and overall accuracies exceeding 0.81 and 90%, respectively. Over the past two decades, the planting areas of double-season rice in Southern China decreased by 54.49%, and a reduction was observed across eight provinces, while only half of the provinces exhibited an increase in the planting areas of single-season rice. Compared to the year 2000, the planting area of the conversion from double- to single-season rice cropping systems in 2020 was 2.71 times larger than that of the conversion from single- to double-season rice cropping systems. The hotspots of the change in rice cropping intensity were mainly located in the central part of Southern China (excluding the Poyang Lake Plain). The decline in the rural labor force, coupled with ≥10 °C accumulated temperature and topographical factors, plays a crucial role in the decreased intensity of rice cropping. Our findings can be beneficial for realizing regional agricultural sustainability and food security. [ABSTRACT FROM AUTHOR]

The magnetic reconnection process relevant to that at the magnetotail is one of the research contents of the Space Plasma Environment Research Facility, which is under construction at the Harbin Institute of Technology in China. Two magnetic mirror sub-coils placed symmetrically in the vertical direction and connected in series cooperate with a dipole coil to generate a magnetic field environment similar to the Earth's magnetotail. A capacitor-based pulsed power supply (PPS) system with a modular design is developed to excite two magnetic mirror sub-coils to generate a magnetic field with a magnetic flux density of not less than 200 G at the center of the two sub-coils. The PPS should deliver a pulsed current with a peak of more than 8 kA, and the duration of the current not be less than 95% of the peak over 5 ms to two magnetic mirror sub-coils when the charging voltage is not less than 20 kV. In addition, the duration from the peak to 10% of the peak is not more than 130 ms. The detailed design of the PPS is discussed in this paper, and a test method is designed to reduce the risk of damage to the wires and the connection between the wires and the coaxial cables of the PPS when the PPS discharges at a higher charging voltage. Finally, the discharge test of the PPS is carried out to verify the design of the PPS. [ABSTRACT FROM AUTHOR]

Natural colloids (NCs) are heterogeneous mixtures of particles in the aquatic environments that are strongly influenced by land use and water quality between terrestrial and aquatic environments. However, the relevant study paid little attention to the difference among the waters with different sizes of particles (e.g., suspended particulate matter (SPM), NCs, and the truly soluble substances). In this study, the spectral properties of these different waters were investigated from different land-use types in the Yuan River basin, China. Results of the UV–visible absorption spectral showed that with the particle size increased, the aromaticity, chromophoric dissolved organic matter, and humification degree of organic matter increased, while the condensation degree decreased. Data analysis from the fluorescence indices indicated that the source and the autochthonous feature of the truly soluble substances differed from that of NCs and SPM, whereas the protein-like component was mainly combined with the relatively larger size of particles (i.e., SPM and NCs), especially the downstream. Although the spectral characteristics of the water samples were strongly influenced by the water quality (> 45%), the land-use type might be the real potential impactor. Furthermore, the influence of land-use type on the spectral properties differed between the large and small scale of the buffer strips and between the mainstream and the tributaries. And this effect was more significant on the fluorescence properties in the mainstream and the spectral properties for NCs than for SPM. The study helps to understand the biogeochemical effects of the waters with different particle sizes. [ABSTRACT FROM AUTHOR]

Cropland abandonment is driven by various mechanisms and is best viewed from multiple perspectives to suggest targeted policy changes which may change the status quo of abandonment. Here, we systematically analyze the characteristics of abandonment and its driving mechanisms by different farming households (pure, part-time, and non-farm) in three topographic regions of the Poyang Lake region using a binary logistic regression model. Results show that: (1) The overall abandonment probability in the Poyang Lake region is largest for non-farm households, followed by part-time households and pure households. In the mountainous region, abandonment is largest for non-farm households, followed by pure households and part-time households. Both the hilly and plain regions show the largest abandonment probability for pure households, followed by part-time households, and non-farm households. (2) The low agricultural economic benefits and the uneconomical investments of time in plots are the main abandonment determinants for pure households. Economic efficiency, both the time invested in plots and economic efficiency, are key abandonment determinants for pure households in the mountainous and plain regions, respectively. (3) Labor shortage and plots which are time-consuming and unfavorable to cultivation are the main abandonment determinants for part-time households, with different factors in different topographic regions. (4) For non-farm households, many factors can influence the occurrence of abandonment. Non-farm households in the mountainous and hilly regions are more influenced by non-farm work and the number of farming workers, respectively; in addition, the inconvenience of using agricultural machinery has a significant influence. [ABSTRACT FROM AUTHOR]

In the past four decades, the livelihood strategies of Chinese smallholder farmers have become increasingly diversified and individualized, and consequently, their rice growing practices have diverged. However, few studies have identified how rice growing practices change with livelihood strategies. To address this challenge, this study employs an integrated smallholder livelihood strategy framework and uses crosssectional data in 2018 covering 250 smallholder farmers who belonging to 90 households in 10 villages in the Poyang Lake Plain, southern China. The results show that livelihood strategies were grouped into five categories based on the allocation of labor input, and the factors that differentiate the farmers adopting rice farming-dominated livelihoods from other farmers include age, sex, education level, health, annual income, the number of appliances and land area. Farmers who relied heavily on rice growing for their livelihoods grew larger area of rice paddy, invested more per unit area, applied more types of agrochemicals and obtained higher unit yields than those farmers spending most of their time on off-farm enterprises. However, the income of the former was much lower than that of the latter due to the low return of rice farming. There is no significant difference in the application weight of agrochemicals across livelihood strategies, which implies that farmers who do not heavily depend on rice growing excessively apply agrochemicals that cannot effectively increase rice yields. Based on these findings, we suggest that the government should implement measures to substantially increase the return of rice growing and educate rice farmers so they will adopt more environmentally friendly practices for applying agrochemicals. • Livelihood strategies of smallholder farmers were grouped into five categories. • The determinants of smallholder farmers' livelihood strategies were examined. • Smallholder rice farming practices across livelihood strategies were compared. [ABSTRACT FROM AUTHOR]

The mechanism of acceleration, loss, and wave–particle interaction of energetic particles in the magnetosphere is a research content of the Space Plasma Environment Research Facility, which is being built as a user facility at the Harbin Institute of Technology in China. Two magnetic perturbation coils are used to simulate the magnetic storm distortion and excite Alfvén wave perturbation. A capacitor-based pulsed power supply (PPS) system with a modular design is developed to excite the magnetic perturbation coils to generate the required amplitude and duration of the magnetic field. The two magnetic perturbation coils are the CRDI coil and CRDII coil and are excited by one set of PPSs. The PPS for the CRDI coil consists of two modules and can provide a pulsed current of no less than 132 kA at 0.12 ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 0.7 ms. The PPS for the CRDII coil consists of five modules and can provide a pulsed current of no less than 16 kA at 0.45, 0.65, 0.8, 0.95, and 1.1 ms, and the duration of the pulsed current from the peak to 10% of the peak is no more than 4.5 ms. The detailed design of the PPSs has been discussed in this paper, and the discharge test of the PPSs is carried out to verify the design of the PPSs. [ABSTRACT FROM AUTHOR]

3D asymmetric magnetic reconnection is an important investigation of the Space Plasma Environment Research Facility, which is being built as a user facility at the Harbin Institute of Technology in China. Four magnetosheath coils, which consist of Poloidal Field (labeled PF) coils and Toroidal Field (labeled TF) coils, are used to generate the magnetic field and plasma environment for the reconnecting experiment. A capacitor-based pulsed power supply (PPS) system with a modular design is developed to excite the magnetosheath coils to generate the required amplitude and duration of the magnetic field. The PPS system includes the PF PPS and TF PPS, which include four sets of PPSs, respectively. Each set of PF PPS and TF PPS consists of nine modules and four modules, respectively, and each module consists of a charge and discharge unit. The PF PPS can provide a pulsed current of no less than 360 kA for the corresponding PF coil at 0.11 ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 0.6 ms. The TF PPS can provide a pulsed current of no less than 200 kA for the corresponding TF coil at 0.08 ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 1.6 ms. The detailed design of the PPS has been discussed in this paper, and the detailed design of the main components in the discharge unit of the PPS is also given in this paper. Finally, the discharge tests of all the PPSs are carried out to verify the design of the PPSs, and the results of the PPSs in discharge tests indicate that all the PPSs meet the design requirements. [ABSTRACT FROM AUTHOR]

The Space Plasma Environment Research Facility currently under construction at the Harbin Institute of Technology in China uses four magnetosheath coils (flux cores) and a dipole coil to generate the magnetic field required for the study on the magnetopause magnetic reconnection. Two groups of magnetopause shape control coils (labeled CK coils) are used to slightly adjust the magnetic field distribution on the magnetopause. A capacitive pulsed power supply (PPS) system with a modular design is developed to excite CK coils. The PPS system consists of six sets of PPS with the same principle and structure, which are used to excite six sub-coils of the CK coils, respectively. Each set of PPS consists of ten modules and one local controller, and each module consists of a charger and discharge unit. Each set of PPS can provide a pulsed current of no less than 400 kA for the corresponding sub-coil at 0.11 ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 0.6 ms. The detailed design of the PPS is discussed in this paper, and the discharge test of the PPS is carried out to verify the design of the PPS. Because there are acquisition and control devices in the discharge unit, the electromagnetic interference immunity design is also discussed to ensure the normal operation of the PPS. [ABSTRACT FROM AUTHOR]

The Space Plasma Environment Research Facility (SPERF) currently under construction at the Harbin Institute of Technology in China is a user facility dedicated to studying space plasma physics on the ground. A coil system of the SPERF consists of seven types of coils, which are used to generate the magnetic fields and plasma required by the physical experiments. A dipole coil of the coil system works with four magnetosheath coils (flux cores) to build the magnetic fields resembling that of the Earth and solar wind. A capacitor-based pulsed power supply (PPS) system with a modular design is developed to excite the dipole coil to generate a magnetosphere-like magnetic field required by the magnetopause magnetic reconnection experiment. The PPS of the dipole coil has a longer pulse duration and more energy than that of other coils in the coil system, it delivers a pulsed current with a peak of more than 18 kA, and the duration of the current is not less than 95% of the peak over 10 ms to the dipole coil when the charging voltage is not less than 20 kV. The detailed design of the PPS is discussed in this paper, and the discharge test of the PPS is carried out to verify the design of the PPS. [ABSTRACT FROM AUTHOR]

The capacitor-based pulsed power supply (PPS) system is an important subsystem of the Space Plasma Environment Research Facility being built as a user facility at Harbin Institute of Technology in China. It has been developed with a modular design to drive magnetic coils to generate magnetic fields and plasma for the physical experiments. In this paper, the modular design and component selection are proposed based on a calculation of parameter ranges of components and the number of modules followed by a simulation and an engineering test. Both the simulation and test results show the feasibility of the selected components and the number of modules to meet the designing requirements of the PPS. [ABSTRACT FROM AUTHOR]

The ecological functions of core and non-core bacteria are gradually being identified, yet little is known about their responses to environmental changes and assembly processes, especially in urban river ecosystems. Here, we investigated bacterioplankton communities over 1 year in an urban section of the Ganjiang River, China. The results revealed that the alpha- and beta-diversity of bacterioplankton communities had no significant spatial differences along the urbanization gradient, but they presented distinct seasonal variations. The bacterioplankton communities were comprised of a few core taxa (11.8%) and a large number of non-core taxa (88.2%), of which the non-core taxa were the most active component responsible for community dynamics. Most non-core taxa (76.84%) belonged to non-typical freshwater bacteria, implying that they are more likely to derive from allochthonous inputs than the core taxa. Variance partitioning analyses showed that air temperature, flow rate and water chemistry together explained 58.2 and 38.9% of the variations of the core taxa and non-core taxa, respectively. In addition, the relative importance of temperature and water chemistry on the bacterioplankton communities prevailed over that of flow rate alone. This means that deterministic processes and stochastic processes simultaneously control the bacterioplankton community assembly, with deterministic processes contributing more than stochastic processes. [ABSTRACT FROM AUTHOR]

As the climate system is known to be warming unevenly, the open question of whether there has been a significant warming "hiatus" at global or regional scales has attracted worldwide attention. With annual mean air temperature (Tmean) setting new records subsequent to 2012, it is reasonable to reanalyse the presence of an apparent decelerated warming trend in China. We therefore examined the shifts of temperature trends in China between 1980 and 2017 using homogenized records from 798 meteorological stations via the Breaks For Additive Season and Trend (BFAST) method and Mann–Kendall and Sen's slope estimator statistical tests. The results show that Tmean at the country level exhibited monotonic increase with a positive break occurring around 1997, and the warming rate during 1980–2017 (0.36 °C/decade) was slightly higher than that during 1980–1997, which suggests that this positive break did not overwhelm the overall continuous warming trend. Spatial records show that most areas west of 108°E or south of 30°N within the country experienced a continual warming trend over the study period and that negative break that occurred around 2010 was major contributor to temporary decelerated warming trend detected in other areas, especially in Northeast China. Hence, this study highlights annual air temperature has continued to rise overall in China since 1980, while considerable regional differences have been detected within the shifts of temperature trends. Annual air temperature has continued to rise overall in China since 1980, albeit with short‐term fluctuations (a). Most areas west of 108°E or south of 30°N within the country has experienced a continual warming trend, whereas negative break that occurred around 2010 was a major contributor to the temporary decelerated warming trend detected in other areas (b). [ABSTRACT FROM AUTHOR]

The concentrations, sources, and risks of heavy metals (Fe, Al, Mn, Cr, Co, Ni, Cu, Zn, As, Cd, W, Pb, and Tl) in sediments in five river-lake ecosystems in the Poyang Lake region were studied. The concentrations of the heavy metals varied spatially, with most of the highest concentrations in the Raohe river-lake ecosystem (RH). All heavy metals except As, Cd, W, and Tl were enriched in sediments possessing high total organic carbon contents or in finer sediments. Based on enrichment factors and statistical methods, it was found that Cd in sediments in the Xiushui (XS), Ganjiang (GJ), Xinjiang (XJ) river-lake ecosystems, and RH; Mn in the XS, GJ, and RH; and W in the XS and GJ were greatly affected by anthropogenic inputs. Moreover, the origins of Cu, Zn, and As require more attention due to the high concentrations found. The high enrichment factor of Cd in the sediments indicated that this metal might cause significant pollution in the environment. The results of the modified potential ecological risk index revealed that the XS, GJ, RH, and XJ were at considerable ecological risk, while the sediments in the Fuhe river-lake ecosystem (FH) were at moderate ecological risk, with Cd contributing the highest proportion of risk. The hazard score fundamentally validated the modified potential ecological risk analysis and revealed a mean toxicity of 57.80% to the benthic organisms in the RH. [ABSTRACT FROM AUTHOR]

The occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs) in a city of Central China were determined in the settled dust and its extracted water phase from different land use types and bus stops in Nanchang City. The physicochemical properties of its water extracted dissolved organic matter (WEOM) were characterized to investigate the effect of fluorescence organic matter on the dust-water partitioning coefficients (K d) using three-dimensional excitation-emission matrix fluorescence spectroscopy combined parallel factor analysis. Results showed that the range of ∑PAHs in settled dust and the extracted water phase was 0.05–15.92 μg·g−1 and 2–211 ng·L−1, respectively. These PAHs mostly came from the combustion of biomass. The risk assessment showed that PAHs in dust had no obvious health risk (less than the magnitude of 10−6). Additionally, the high molecular weight (HMW) PAHs and the low molecular weight (LMW) PAHs were preferentially adsorbed by dust and the dissolved portion, respectively. It was confirmed by the relatively high log K d values of 4.23 for the HMW-PAHs. Pearson correlation analysis suggested that the higher concentration of dissolved organic carbon and humic-like substance were in favor of PAHs in dust released into waters. This study can provide information on pollution control when considering the impact of fluorescent organic matter on the fate and transport of PAHs. [Display omitted] • Partitioning behavior of PAHs between dust and WEOM was investigated. • Higher concentrations of ∑PAHs in both dust and WEOM were from the traffic roads. • LMW-PAHs preferred to dissolve in waters due to their higher solubility. • HMW-PAHs were predominantly existed in dust having a higher log K d value. • Humic-like substance was in favor of PAHs in dust released into waters. [ABSTRACT FROM AUTHOR]

Accurately understanding the relationship between grain production and economic development is of great practical significance for ensuring national food security and coordinating inter-regional economic development. Using 2012 counties as research units, we analyzed the spatial coordination between grain production and economic development in China using the coupling of grain and economy (CGE) index, as well as the curve of gravity center and thematic map series methods based on statistical data from counties between 2000–2017. The results showed that: (1) Grain production was weakly coordinated with the economic development in China; but this coordination was enhanced. (2) China's conversion between various types of grain production and economic development mainly occurred in the central and western regions, which are characterized by a much higher grain agglomeration level than the economic agglomeration level. (3) The northeastern region was prone to the grain agglomeration, the central and western regions were characterized by a grain-economy balance and the eastern region was dominated by economic agglomeration. (4) The increase of China's CGE gradually increased from the southwest to northeast. Therefore, we proposed that the government should pay more attention to grain circulation in the eastern region and main grain-producing areas in central region should develop an accurate benefit compensation system, support leading grain processing enterprises and implement cultivated land protection policies in order to ensure national food security. [ABSTRACT FROM AUTHOR]

Intermittent surface water frequently transitioning between water and land over months and years, plays a crucial and increasingly significant role in both social and ecological systems. However, their vital and dramatic dynamics have mainly remained invisible due to monitoring limitations. We present a new remote sensing framework to capture the long-term monthly dynamics of surface water bodies, applying it to Poyang Lake, the largest freshwater lake in China. This framework employed a random forest classifier on all available Landsat data to identify monthly surface water bodies. Additionally, we developed a Spatial and Temporal Neighborhood Similarity-based Gap Filling method to restore water bodies obscured by clouds and ensure spatial integrity. Furthermore, we introduced an index to quantify the intermittency of surface water bodies on a scale from 0 to 1, allowing for the classification of water bodies into three categories: perennial, wet intermittent, and dry intermittent. Employing this framework, we reconstructed the most complete monthly 30-m surface water dataset for cloudy regions to date, covering April 1986 to September 2023, demonstrating a strong correlation (Spearman's rank correlation coefficient of 0.909) with observed water levels. The results reveal a landscape dominantly composed of intermittent water bodies (91.2%), with a rapidly shrinking trend of perennial water bodies at 1303.58 ha per year. Notably, 162,685 ha (21.9%) of water bodies transitioned toward drier and more intermittent statuses. Dry intermittent water bodies exhibited the most pronounced land-water transitions, with the highest water-to-land (82.5%) and land-to-water (89.9%) proportions among the three categories. By uncovering the hidden dynamics of intermittent surface water, and highlighting its prevalence, expansion, and vulnerability, this framework paves the way for a better understanding of these critical water dynamics across the globe. • Presented a novel framework for detailed monitoring of surface water dynamics • Created an innovative index to quantify the intermittency of water bodies • Reconstructed a spatiotemporally-complete 450-month time series of surface water • Poyang Lake comprises 91.2% intermittent water and the remainder perennial • Revealed 21.9% of water bodies transitioned to drier and more intermittent state [ABSTRACT FROM AUTHOR]

Soil microbes play a crucial role in ecosystem function. Here, the effects of soil and water conservation measures on soil microbial community structures, biodiversity, and co-occurrence networks are investigated and compared. We sampled soils at three different depths (0–10 cm, 10–20 cm and 20–40 cm) in a citrus orchard that uses long-term soil and water conservation measures, which includes Bermuda grass strip intercropping (BS), Bermuda grass full coverage (BF), Radish–soybean crop rotation strip intercropping (RS) and clear tillage orchards (CT). Results demonstrated that BS and BF yields a significant increase in bacterial richness and diversity of fungal in soils, while BF contains more beneficial microbial taxa, especially those with degrading and nutrient cycling capabilities. Microbial community structures differed significantly among the applied measures. In addition, co-occurrence networks under BS, BF and RS were more complex and robust than that of CT, and the stability of the network in BF was the highest. Microbial interactive stability and potential interactions in bacterial networks were stronger than those of fungi. The distribution of dominant phyla showed that Chloroflexi and Ascomycota dominated the different soil and water conservation measures. Proteobacteria and Ascomycota are revealed to be keystone species in bacterial networks and fungal networks, respectively, while Proteobacteria was the keystone species in microbial networks. Though the relative abundance of Chloroflexi turned out to have increased among the four measures, the relative abundance for Proteobacteria, Acidobacteria and Actinobacteria all decreased along the soil profile, with Acidobacteria under BS to be an exception. Soils under BS and BF had higher total nitrogen, microbial biomass carbon and organic carbon than CT and RS. Organic carbon(C) and total nitrogen(N) in soil were the major drivers of these bacterial community patterns, while there was no significant correlation between them and fungi. Overall, BF increases soil nutrients and microbial diversity, and also promotes ecological stability and interrelations among microbial taxa that collectively improve soil quality in the citrus orchard studied. Therefore, we recommended BF to be an ideal application for citrus orchards of southeast China. [ABSTRACT FROM AUTHOR]

• Landscape ecological risk (LER) of a cross-border basin was assessed for sustainability. • Landscape management in the Koshi River Basin with its fragile ecosystems is a challenge. • LER decreased for 1990–2000 and increased for 2000–2017. • The LER of the border between China and Nepal was high and it increased for 2000–2017. • As the slope increased, the LER increased dramatically. Developing a reasonable landscape ecological risk (LER) assessment is crucial to establishing LER alert mechanisms and promoting ecological protection, environmental management and social development. The typical cross-border Koshi River Basin (KRB), which has a sensitive human-environment relationship, was the study area. Using the LER assessment model, we evaluated the LER of the KRB in 1990, 2000, 2010 and 2017 and analyzed its spatial-temporal evolution characteristics. Spatial autocorrelation analysis was conducted to assess the clustering characteristics of the LER. The results showed the following: (1) The LER in the KRB showed a decreasing trend for 1990–2000 and an increasing trend for 2000–2017. High LER areas were mainly located on the border between China and Nepal, where the LER increased from 1990 to 2017. (2) The Nepal part of the KRB had the highest LER, and the Indian part had the lowest LER. As the slope increased, the extremely ecologically deteriorated areas generally increased. (3) The LER displayed a clustering characteristic in the KRB. High–high regions were distributed in extremely high LER regions, and low–low regions were located in extremely low and low LER regions. High human influence intensity was responsible for the increase in LER. Our study is valuable to the development and ecological security management of cross-border basins. [ABSTRACT FROM AUTHOR]

Accurate information about the spatiotemporal patterns of rice paddies is essential for the assessment of food security, management of agricultural resources, and sustainability of ecosystems. However, accurate spatial datasets of rice paddy fields and multi-cropping at fine resolution are still lacking. Landsat observation is the primary source of remote sensing data that has continuously mapped regional rice paddy fields at a 30-m spatial resolution since the 1980s. However, Landsat data used for rice paddy studies reveals some challenges, especially data quality issues (e.g., cloud cover). Here, we present an algorithm that integrates time-series Landsat and MODIS (Moderate-resolution Imaging Spectroradiometer) images with a phenology-based approach (ILMP) to map rice paddy planting fields and multi-cropping patterns. First, a fusion of MODIS and Landsat data was used to reduce the cloud contamination, which added more information to the Landsat time series data. Second, the unique biophysical features of rice paddies during the flooding and open-canopy periods (which can be captured by the dynamics of the vegetation indices) were used to identify rice paddy regions as well as those of multi-cropping. This algorithm was tested for 2015 in Nanchang County, which is located on the Poyang Lake plain in southern China. We evaluated the resultant map of the rice paddy and multi-cropping systems using ground-truth data and Google Earth images. The overall accuracy and kappa coefficient of the rice paddy planting areas were 93.66% and 0.85, respectively. The overall accuracy and kappa coefficient of the multi-cropping regions were 92.95% and 0.89, respectively. In addition, our algorithm was more capable of capturing detailed information about areas with fragmented cropland than that of the National Land Cover Dataset (NLCD) from 2015. These results demonstrated the great potential of our algorithm for mapping rice paddy fields and using the multi-cropping index in complex landscapes in southern China. [ABSTRACT FROM AUTHOR]

A compound system involving three matrices (water, sediment, and paddy soil) was conceived to determine the potential sources of metal(loid)s (Ti, Fe, Co, Ni, Cu, Zn, As, Cd, Pb, and U) and synthetically evaluate their pollution levels in the Le'an River basin. The result indicated that the established background values (BVs) of paddy soil and sediment in the compound system were obviously higher than those of the upper continental crust (UCC) and soils from Jiangxi Province, a difference which was especially marked for sediment. The concentrations of Cu, Zn, As, Cd in the system had high coefficients of variation (CVs), and metal(loid)s in sediment showed higher levels than those in paddy soil, except for Pb. Cd and Cu in the system had the highest Ef levels, which probably pose a high risk to organisms and the health of local residents. There were significantly linear relationships between the site rank index (SRI) for water and that for sediment or paddy soil, revealing that matrices in the system interacted with each other. Principal component analysis (PCA) and absolute principal component scores and multiple linear regression model (APCS-MLR) results demonstrated that Cu, Zn, As, Cu, Pb, and U enrichments in the system were mainly affected by mining activities and were predominately deposited in sediment. Point pollution sources rather than non-point pollution sources such as mining activities, contributed most of the anthropogenic metal(loid)s to sediment. Both SRI and Hierarchical cluster analysis (HCA) results visually showed that S5, S8, S9, S10, S11, and S12 severe pollution grouped together and scattered through areas with extensive mining activities, while other sites with moderate pollution were spread along the main stream of the Le'an River. Image 1 • The compound system involving water, sediment and paddy soil was established. • There were latent interactions of metal(loid) among matrices in the compound system. • Cd and Cu enrichment in the compound system likely posed high risk to the organism and human health. • Sediment was the main sink of anthropogenic metal(loid)s mainly contributed by point pollution sources. • Sampling sites in the area with violent mining activities suffered severe pollution. Main finding: Establishing the compound system is an effective way to evaluate the pollution level in a specific basin. Efs indicate the migration of anthropogenic pollutants in the system. [ABSTRACT FROM AUTHOR]

Background: The increase in the frequency and intensity of extreme heat events, which are potentially associated with climate change in the near future, highlights the importance of heat health risk assessment, a significant reference for heat-related death reduction and intervention. However, a spatiotemporal mismatch exists between gridded heat hazard and human exposure in risk assessment, which hinders the identification of high-risk areas at finer scales. Methods: A human settlement index integrated by nighttime light images, enhanced vegetation index, and digital elevation model data was utilized to assess the human exposure at high spatial resolution. Heat hazard and vulnerability index were generated by land surface temperature and demographic and socioeconomic census data, respectively. Spatially explicit assessment of heat health risk and its driving factors was conducted in the Yangtze River Delta (YRD), east China at 250 m pixel level. Results: High-risk areas were mainly distributed in the urbanized areas of YRD, which were mostly driven by high human exposure and heat hazard index. In some less-urbanized cities and suburban and rural areas of mega-cities, the heat health risks are in second priority. The risks in some less-developed areas were high despite the low human exposure index because of high heat hazard and vulnerability index. Conclusions: This study illustrated a methodology for identifying high-risk areas by combining freely available multi-source data. Highly urbanized areas were considered hotspots of high heat health risks, which were largely driven by the increasing urban heat island effects and population density in urban areas. Repercussions of overheating were weakened due to the low social vulnerability in some central areas benefitting from the low proportion of sensitive population or the high level of socioeconomic development. By contrast, high social vulnerability intensifies heat health risks in some less-urbanized cities and suburban areas of mega-cities. [ABSTRACT FROM AUTHOR]

The biogeographical distribution of plants and animals has been extensively studied, however, the biogeographical patterns and the factors that influence bacterial communities in lakes over large scales are yet to be fully understood, even though they play critical roles in biogeochemical cycles. Here, bacterial community compositional data, geographic information, and environmental factors were integrated for 326 Chinese lakes based on previously published studies to determine the underlying factors that shape bacterial diversity among Chinese lakes. The composition of bacterial communities significantly varied among the three primary climatic regions of China (Northern China, NC; Southern China, SC; and the Tibetan Plateau, TIP), and across two different lake habitats (waters and sediments). Sediment bacterial communities exhibited significantly higher alpha-diversity and distance-decay relationships compared to water communities. The results indicate that the "scale-dependent patterns" of controlling factors, primarily influenced by geographical factors, become increasingly pronounced as the spatial scale increases. At a national scale, geographical factors exerted a dominant influence on both the water and sediment communities across all lakes, as geographical barriers restrict the dispersal of individuals. At smaller spatial scales, temperature-driven selection effects played a greater role in shaping water bacterial community variation in the NC, SC, and TIP, while geographical factors had a stronger association with sediment bacterial community variation in the lakes of the three regions. This synthesis offers novel insights into the ecological factors that determine the distribution of bacteria in Chinese lakes. [Display omitted] • Controlling factors of bacterial communities in Chinese lakes were identified. • Bacterial community composition significantly varied across regions and habitats. • Geographical factors drived the variation of water and sediment communities. • Temperature-driven selection effects had significant impacts on water communities. • Distance-decay relationship and α-diversity in sediments were higher than in waters. [ABSTRACT FROM AUTHOR]

Heavy metals in river basins can affect the entire ecosystem through water recycling. Different heavy metals are significantly affected by riparian landscape patterns due to the difference of source and migration processes, while the intensity of impact is directly influenced by the spatial scale of landscape patterns. Here, we employ correlation analyses (CA) and redundancy analyses (RDA) to determine spatial scales for which multi-medium heavy metals (Cr, Mn, Cu, Zn, As, Cd and Pb) are most sensitive landscape indices in the riparian zone of the Yuan River. Results show that the most sensitive spatial scales for dissolved heavy metals were the 300 m line buffer in the wet season and catchments in the dry season. The most sensitive spatial scales for suspended particulate heavy metals were catchments in the wet season, and the 300 m and 500 m line buffers in the dry season. However, correlations between heavy metals in sediment and landscape indices were unclear at all spatial scales. The spatial scales of the 100 m point buffer and catchments showed the highest explained variances for all media. The most important landscape indices for dissolved heavy metals were ENN_MN (Mean Euclidean Nearest Neighbor Distance) and LPI (Largest Patch Index), and SHDI (Shannon's Diversity Index) and ED (Edge Density) for particulate heavy metals. More accurate spatial scale effects of landscape indicators can provide data and reference for similar watershed studies. [Display omitted] • The responses of heavy metals in surface water, suspended particle, and sediment on landscape indices were studied. • The point buffer 100 m and catchment spatial scales showed the higher explained variances of all media. • The most important landscape indices for dissolved heavy metals were ENN_MN and LPI. • The highest explained variances for particulate heavy metals were from the landscape indices of SHDI and ED. [ABSTRACT FROM AUTHOR]

Due to rapid population growth and urbanization, paddy rice agriculture is experiencing substantial changes in the spatiotemporal pattern of planting areas in the two most populous countries—China and India—where food security is always the primary concern. However, there is no spatially explicit and continuous rice-planting information in either country. This knowledge gap clearly hinders our ability to understand the effects of spatial paddy rice area dynamics on the environment, such as food and water security, climate change, and zoonotic infectious disease transmission. To resolve this problem, we first generated annual maps of paddy rice planting areas for both countries from 2000 to 2015, which are derived from time series Moderate Resolution Imaging Spectroradiometer (MODIS) data and the phenology- and pixel-based rice mapping platform (RICE-MODIS), and analyzed the spatiotemporal pattern of paddy rice dynamics in the two countries. We found that China experienced a general decrease in paddy rice planting area with a rate of 0.72 million ( m ) ha/yr from 2000 to 2015, while a significant increase at a rate of 0.27 m ha/yr for the same time period happened in India. The spatial pattern of paddy rice agriculture in China shifted northeastward significantly, due to simultaneous expansions in paddy rice planting areas in northeastern China and contractions in southern China. India showed an expansion of paddy rice areas across the entire country, particularly in the northwestern region of the Indo-Gangetic Plain located in north India and the central and south plateau of India. In general, there has been a northwesterly shift in the spatial pattern of paddy rice agriculture in India. These changes in the spatiotemporal patterns of paddy rice planting area have raised new concerns on how the shift may affect national food security and environmental issues relevant to water, climate, and biodiversity. [ABSTRACT FROM AUTHOR]

To investigate the contamination levels of heavy metals, surface water and sediment samples were collected from 21 sites along the Gan River. The heavy metal concentrations (V, Co, Cr, Ni, Cu, Zn, Cd, and Pb) were determined using inductively coupled plasma spectrometry (ICP-MS). The results demonstrated that the status of the surface water and sediments as a whole were relatively clean with regard to heavy metals (except for Cd) compared to water quality standards and sediment quality guidelines. The two heavy metal sources of the surface water and sediments were identified separately using factor analysis (FA). High levels of metals were found in the sediment in the upstream and downstream due to frequent mining and industrial activities, whereas concentrations of heavy metal in the surface water from two sources were abundant in the upstream and midstream - likely related to mining activities and sediment suspension. As indicated by enrichment factor (EF) and potential ecological risk index (PERI), Zn, Pb, and Cd were the most anthropogenically enriched metals, while sediments in the upstream and downstream had high potential ecological risk. Local people, including adults and children who ingested water from the Gan River, showed little potential non-carcinogenic risk, as the hazard index (HI) scores were less than 1. Compared with those in other rivers in the world, heavy metal enrichments in surface water and sediments were of moderate levels. [ABSTRACT FROM AUTHOR]

Heavy metals in watersheds are a serious concern due to their toxicity, abundance, and persistence in the environment, especially in mining areas. Source analyses and exploration of other related factors are one of the most important methods to help with effective prevention and control of heavy metal pollution in watersheds. In this study, the concentrations of Cr, Co, Ni, Cu, Zn, As, Cd, Sb, Ba and Pb were measured in the Le'an River, and PCA (principal component analysis) and APCS-MLR (absolute principal component scores - multivariate linear regression) methods were used to identify the sources of the dissolved heavy metals. Additionally, a CA (correlation analysis) method was used to explore the correlations between landscape indices and concentrations of heavy metals. Results show that the main sources for these dissolved heavy metals are mining activities, fertilizers, pesticides, and natural sources. Specific results of PCA and APCS-MLR suggest that Cu, Zn, Cd, Ba are mainly related to mining activities, Cr and Pb are due to fertilizers and pesticides, and Co and Ni are mainly due to natural sources. Correlations between landscapes and heavy metals revealed significant temporal variations, with the strongest responses of dissolved heavy metals to landscape indices appearing in December and March. The propensity of positive or negative responses of the heavy metals to landscape indices are determined by the sources, and their temporal variations may be related to the seasonal changes of rainfall and plant metabolism. • Land indices regulating dissolved heavy metals reveals significant seasonal variations. • Varied source affect the response of the dissolved heavy metals to landscape indices. • Seasonal changes of rainfall and plant metabolism also account for the response. [ABSTRACT FROM AUTHOR]

• A 300 m buffer zone of the Yuan River basin is a critical scale at which landscape structures affect water quality. • Joint effects of landscape compositions and configurations account for most of the variation in water quality. • Different methods of dividing regions considerably impact the observed correlations between landscape structures and water quality. • Basin area also affects the correlation coefficient between landscape composition and water quality. Significant attention has recently been given towards understanding the hydrological effects of landscape structures. However, few studies have quantified the relationships between landscape structures and river water quality at different spatial scales. Here, we evaluated the influence of landscape structures, including structural composition and spatial configuration, on river water quality at scales ranging from riparian zones to entire regions. Water quality parameters (pH, Cl−, SO 4 2−, DO, NO 3 −−N, NH 4 +−N, TP, and heavy metals) were determined from 38 sample sites in August 2018 during the wet season and January 2019 during the dry season. Landscape structures explained more of the water quality variation (ranging from 7% to 36%) in the near-distance buffer zones (100, 300, and 500 m), but slightly less (ranging from 2% to 27%) in the long-distance buffer zones (1000 m and entire regions). Landscape structures had the greatest impact on water quality at the 300-m buffer zone, and of all explanatory variables of landscape, joint effects between landscape composition and landscape configuration accounted for more than half of the variation in water quality. Moreover, different regional division methods considerably impacted the measured correlation between landscape structures and water quality. Compared with zonal division, a larger basin area division of sub-basin enhanced the correlation and associated significance between landscape composition and water quality. Concomitantly, the input of exogenous pollutants weakened the influence of mean dendritic stream length on the relationships between landscape structures and water quality. Overall, this study provides new insights into the relationships between landscape structures and river water quality. In future studies, selecting an appropriate regional division method is critical for revealing the effects of landscape structures on water quality. Furthermore, strengthening land-use management in the buffer zones near river banks is critical for protecting river water quality. [ABSTRACT FROM AUTHOR]

Trace metals in street dust originate from many natural and anthropogenic sources and may directly or indirectly affect daily life and health. Here, the enrichment factor (EF), an efficient parameter to assess the contamination by trace metals, was evaluated and compared in four different zones of the urban area of Nanchang city during different seasons. Results showed that EFs of trace metals have regional seasonal variations. The EF range of Cr, Ni, Cu, Zn, As, Cd and Pb were found to be (0.76-16.38), (0.66-9.06), (1.09-169.58), (1.52-36.16), (0.44-7.17), (2.07-78.38), (0.95-20.94), respectively. These values indicate minimal to significant pollution. The EF values of Zn, Cd and Pb in street dust show very similar variations as their median and mean values of EF are higher in certain zones, and their seasonal variations are similar. The Ni and As results suggest that anthropogenic influences for these elements are not significant. The Ni may be influenced by land use type rather than point sources and As may be attributed to natural sources. The Principal Component Absolute Scores - Multivariate Linear Regression (PCAS-MLR) model was used to identify the types and contributions of trace metal sources. The main sources of trace metals in dust were found to be industrial discharges and traffic emissions. However, the percentages of their contributions have significant regional differences. The relationship between the EF of trace metals and the ecological risk index (ERI) was also investigated, and indicates that seriously polluted areas correspond to high ERI regions. The land use types and characteristics of the source jointly affects the relationship between EFs and ERI., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Natural colloids (NCs) are ubiquities in aquatic environments, which play an important role in the fate and transport of metal elements. Combined with a multi-method analytical approach, this study investigates the spectral characteristics and the contamination of metals of NCs from the five tributaries of Poyang Lake and the lakes in Nanchang City. Results showed that NCs in river samples were characteristic by the smaller molecular weight, lower chromophoric dissolved organic matter (CDOM) concentration, higher aromaticity, and higher CDOM contribution to the organic carbon than those in lake samples. Based on the parallel factor analysis model, three fluorophores were identified, including two humic-like components (C1 and C2) and a protein-like component (C3). NCs in river and lake waters were dominant by the humic-like substance (C1) and the protein-like substance (C3), respectively, with the relatively high fluorescence intensity for all the fluorophores in lake samples. Furthermore, NCs from the river samples were primarily terrestrial NCs with a high degree of humification. The average detection frequency of metal elements was nearly 50% for both river and lake samples, whereas the concentrations of the metal elements were higher in lake samples. Principal component analysis (PCA) results showed that the contamination of the detected metals could divide into three categories, with relatively high concentrations of Ba, Pb, Zn, Al, Sr, and Fe in lake samples. Moreover, PCA results showed that NCs in lakes with higher values of the absorbance and fluorescence parameters were associated with the higher concentration of metal elements, revealing that the spectral characteristic could be the proxy indicator of the contamination of metal elements of NCs.