Phosphorus (P) is a key indicator of the aquatic organism growth and eutrophication in lakes. The distribution and speciation of P and its release characteristics from sediments were investigated by ...analyzing sediment and water samples collected during high flow and low flow periods. Results showed that the average concentrations (ranges) of total phosphorus (TP) in the surface and deep water were 0.06 mg L(-1) (0.03-0.13 mg L(-1)) and 0.15 mg L(-1) (0.06-0.33 mg L(-1)), respectively, while the average concentration (range) of TP in sediments was 709.17 mg kg(-1) (544.76-932.11 mg kg(-1)). The concentrations of TP and different forms of P varied spatially in the surface sediments, displaying a decreasing trend from south to north. P also varied topographically from estuarine areas to lake areas. The vertical distribution of TP and different forms of P were observed to decrease as depth increased. The P concentrations during the low flow period were higher than those during the high flow period. Inorganic phosphorus (IP) was the dominant form of P, accounting for 61%-82% of TP. The concentration of bioavailable phosphorus in sediments was relatively large, indicating a high risk of release to overlying water. The simulation experiment of P release from sediments showed that the release was relatively fast in the first 0-5 min and then decreased to a plateau after 1 hr. Approximately 84-89% of the maximum amount of P was released during the first hour.
Rare earth mine tailing dumps are environmental hazards because tailing easily leaches and erodes by water and wind. To assess the influence of mine tailing on the geochemical behavior of rare earth ...elements (REEs) in soil, sixty-seven surface soil samples and three soil profile samples were collected from different locations near China's largest rare earth mine tailing. The total concentration of REEs in surface soils ranged from 156 to 5.65 × 10(4) mg·kg(-1) with an average value of 4.67 × 10(3) mg·kg(-1), which was significantly higher than the average value in China (181 mg·kg(-1)). We found obvious fractionation of both light and heavy REEs, which was supported by the North American Shale Composite (NASC) and the Post-Archean Average Australian Shale (PAAS) normalized concentration ratios calculated for selected elements (La(N)/Yb(N), La(N)/Sm(N) and Gd(N)/Yb(N)). A slightly positive Ce anomaly and a negative Eu anomaly were also found. For all 14 REEs in soils, enrichment was intensified by the mine tailing sources and influenced by the prevailing wind.
Precision agriculture relies on the rapid acquisition and analysis of agricultural information. An emerging method of agricultural monitoring is unmanned aerial vehicle low-altitude remote sensing ...(UAV-LARS), which possesses significant advantages of simple construction, strong mobility, and high spatial-temporal resolution with synchronously obtained image and spatial information. UAV-LARS could provide a high degree of overlap between X and Y during key crop growth periods that is currently lacking in satellite and remote sensing data. Simultaneously, UAV-LARS overcomes the limitations such as small scope of ground platform monitoring. Overall, UAV-LARS has demonstrated great potential as a tool for monitoring agriculture at fine- and regional-scales. Here, we systematically summarize the history and current application of UAV-LARS in Chinese agriculture. Specifically, we outline the technical characteristics and sensor payload of the available types of unmanned aerial vehicles and discuss their advantages and limitations. Finally, we provide suggestions for overcoming current limitations of UAV-LARS and directions for future work.
Intensive anthropogenic activity has triggered serious heavy metal contamination of soil. Land use and land cover (LULC) changes bear significant impacts, either directly or indirectly, on the ...distribution of heavy metal in soils. A total of 180 samples were acquired from various land covers at different depths, namely surface soils (020 cm) and subsurface soils (20–40 cm). Spatial interpolation, geographically weighted regression (GWR) and self-organizing map (SOM) were used to discern how variations in the spatial distributions of soil heavy metals were caused by human activities for different land uses, and how these pollutants contributed to environmental risks. The medium concentrations of Cd, Cr, Cu, Pb and Zn in surface soil all exceeded the corresponding local background values in flat cropland and developed area soil. The overall ecological risk level of the study varied from low to medium. The GWR model indicated that the land use intensity had a certain influence on the accumulation of heavy metals in the surface soil. K-means clustering of the SOM revealed that the type of LULC also contributed to the redistribution of heavy metals in the surface soil.
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•Heavy metal differentiation in soil was described by spatial interpolation.•The correlation between heavy metals and land use intensity was analyzed.•Most of samples from cropland and developed areas were polluted by heavy metals.•SOM was used to identify the impact of LULC on heavy metal accumulation in soil.
Changes in land use and land cover caused by human activities affect the enrichment and redistribution of heavy metals in soil.
China has relatively abundant rare earth elements (REEs) reserves and will continue to be one of the major producers of REEs for the world market in the foreseeable future. However, due to the large ...scale of mining and refining activities, large amounts of REEs have been released to the surrounding environment and caused harmful effects on local residents. This paper summarizes the data about the contents and translocation of REEs in soils, waters, atmosphere, and plants in REE mining areas of China and discusses the characteristics of their forms, distribution, fractionation, and influencing factors. Obviously high concentrations of REEs with active and bioavailable forms are observed in all environmental media. The mobility and bioavailability of REEs are enhanced. The distribution patterns of REEs in soils and water bodies are all in line with their parent rocks. Significant fractionation phenomenon among individual members of REEs was found in soil–plant systems. However, limited knowledge was available for REEs in atmosphere. More studies focusing on the behavior of REEs in ambient air of REE mining areas in China are highly suggested. In addition, systematic study on the translocation and circulation of REEs in various media in REEs mining areas and their health risk assessment should be carried out. Standard analytical methods of REEs in environments need to be established, and more specific guideline values of REEs in foods should also be developed.
Rare earth elements (REEs) have been increasingly emitted into the atmosphere with a worldwide increase in use of these metals. However, the research on REEs in atmospheric particulates is fairly ...limited. In this paper, atmospheric particulates including total suspended particulate (TSP) matter and particles with an equivalent aerodynamic diameter less than 10 μm (PM10) were collected around a rare earth mine tailing in Baotou, the largest rare earth industrial base in China, in August 2012 and March 2013, for the analyses of REE levels and distributions. The total concentrations of REEs for TSP were 172.91 and 297.49 ng/m3, and those for PM10 were 63.23 and 105.52 ng/m3, in August 2012 and March 2013, respectively. Enrichment factors for all 14 analyzed REEs in the TSP and PM10 indicated that the REE enrichment in atmosphere particulates was caused by anthropogenic sources and influenced by the strong wind in spring season. The spatial distribution of REEs in TSP showed a strong gradient in the prevailing wind direction. The chondrite-normalized patterns of REEs in TSP and PM10 were similar with the conspicuous fractionation between light REEs and heavy REEs.
Groundwater is essential for regional ecological-economic system and is an important resource of drinking water, especially in the Chinese Loess Plateau (CLP), where is a typical water-limited ...ecosystem. Groundwater quality deterioration will affect water security and exacerbate the water shortages. Groundwater hydrochemistry, pollution source apportionment, quality and health risks were evaluated based on analysis of major ions and selected trace elements in seasonal samples of the Fen River Basin (FRB) in the eastern CLP. Groundwaters in the FRB were mainly HCO3−-Ca2+-Na+ water type with low dissolved solutes in upstream samples, high values in midstream samples and medium values in downstream samples. Solutes in upstream samples were mainly derived from carbonate weathering, while those in midstream and downstream samples came from silicate weathering, evaporites dissolution and anthropogenic sources. Self-organizing map (SOM) showed the hydrochemistry remained unchanged from dry to wet season for most sampling points. The seasonal variations of Ag, Cd, Ni, Pb, and Tl were significant due to anthropogenic input. High NO3− in upstream and downstream samples resulted primarily from sewage discharge, and high SO42− in midstream and downstream samples was from gypsum- and coal-related industries. In addition, anthropogenic input related to coal industries significantly aggravates pollution of As, Ni, Ag, Fe, and Mn. Influenced by evaporites and anthropogenic input, midstream samples had high salinity, total hardness and water quality indices (WQIs) and were unsuitable for irrigation or drinking purposes. Seasonal variation of WQI in the FRB was unsignificant except Jiaokou River sub-basin, where groundwater quality was worse in the wet season than the dry season due to coal mining. Great attention should be paid to the high non-carcinogenic risks of exposure to F, V, Mn, and Cr via dermal absorption, particularly for children. Overall, groundwater quality in the FRB was best in upstream, medium in midstream and worst in midstream based on different index. Groundwater quality is deteriorated by anthropogenic input and the sewage discharge in the FRB should be strictly controlled. Our report provides a reference for groundwater pollution evaluation and source identification in similar areas.
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•Seasonal groundwater chemistry and quality was analyzed in Fen River Basin.•Evaporite and anthropogenic input significantly influence groundwater chemistry.•Poor water quality in midstream and wet season are related with human pollution.•Mn, NO3 and SO4 were the main pollutants for drinking purpose.•High non-carcinogenic risks of F, V and Mn were found, especially for children.
Loess weathering and anthropogenic input significantly influence seasonal groundwater hydrochemistry and groundwater quality in the Fen River Basin.
•Rare earth elements has influence on P adsorption process in soil.•P adsorption declined when soils were amended with lower concentration rare earth.•Langmuir equation fitted P adsorption in all ...five types soils.•P desorption increased when soil were amended with rare earth.
Phosphorus (P) is an important biogeochemical element and the environmental fate of P receives increasing attention. Through batch equilibration experiments, the adsorption and desorption of P in the absence and presence of exogeneous rare earth elements (REEs) were investigated in five types of agricultural soil samples collected from China. The results showed that the addition of different doses of REEs had influences on P adsorption processes in the soils, and there were differences in different soil types and different P concentrations of the P solutions. The amount of P adsorption tended to decline when the five types of soils were amended with low concentrations of REEs. The characteristics of P adsorption were more complicated when high concentrations of REEs were added to the different soils. Affected by the high concentrations of REEs, when the P concentration of the P solution added to soils was less than 20mgL−1, the rate of P adsorption tended to increase in all the five types of soils. However, when the P concentration of the P solution added to soil was greater than 30mgL−1, the rate of P adsorption tended to decrease. The Langmuir equation fitted P adsorption in all the five types of soils well. Compared with the control, when soil samples were amended with REEs, the P desorption rates of the five types of soils increased.
•The NANI peaked in 2020, representing a 54.41% increase compared to 1990.•The proportion of food/feed nitrogen input to NANI was the highest, reaching 62.30%.•The spatial pattern of NANI exhibited a ...decreasing trend from east to west and from north to south.•The spatiotemporal changes of NANI are related to the intensity of human activities.•Population density and GDP were the most influential socioeconomic factors impacting NANI.
The issue of global nitrogen overload is widely acknowledged as a pressing concern, with excessive nitrogen input resulting from human activities posing a significant threat to regional security. Notably, China emerges as a prominent contributor, exhibiting one of the highest anthropogenic nitrogen inputs worldwide. This study employs the Net Anthropogenic Nitrogen Input (NANI) as a pivotal tool to scrutinize the spatial and temporal patterns of nitrogen input in China spanning from 1990 to 2020. The total NANI reached its zenith in 2020 at 723,378.80 kg·km−2·yr−1, marking a noteworthy 54.41 % increase from 1990. Among the various nitrogen sources, food/feed nitrogen input prevails, constituting 62.30 % of NANI, followed by atmospheric nitrogen deposition at 30.05 %. In less developed regions, primary contributors to NANI include nitrogen fertilizer application and crop nitrogen fixation. The spatial distribution of NANI exhibits a diminishing trend from east to west and north to south. Conducting a quantitative analysis, this study elucidates the impact of socioeconomic factors on NANI in China. Population density (r = 0.97) and GDP (r = 0.91) emerge as primary influencers, with agricultural factors such as livestock breeding (r = 0.70), grain production (r = 0.40), and fertilizer application (r = 0.65) following suit. In addressing the environmental challenges posed by excessive nitrogen, future mitigation strategies should prioritize enhancements in manure management practices and the implementation of pollution reduction facilities.
The effects of topography, land cover type, and soil physicochemical properties on the distribution of soil organic carbon (SOC) and total nitrogen (TN) have drawn growing attention recently, but ...little is known about how these features-associated interactions impact SOC and TN. To elucidate how these interactions affect the preservation of carbon and nitrogen in soils, we used data-driven models (random forest regression and structural equation modeling) to identify the dominant environmental factors affecting the distribution of SOC and TN in two different soil layers (0–20 and 20–40 cm) of the Qinghai-Tibet plateau. In addition, an algorithm based on random forest (“Boruta”) was chosen to identify the relevant influencing factors and partial dependence was used to depict the two most important factors. We found that rather than land cover type, environmental properties, such as soil physicochemical characteristics and altitude had the most significant effects on the distribution of SOC and TN. Our findings indicate that elevation and TN are the two most important factors influencing SOC in the surface and subsurface soil layers. Moreover, total potassium (TK) impacts TN content in the surface soil layer, but only in a specific range of concentrations, which could be attributed to anthropogenic activities such as applying nitrogen and potassium fertilizers to increase the yields of local food crop, Tibetan hulless barley. These findings provide a scientific perspective on soil nutrient preservation.
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•Partial dependence of various features on SOC and TN was found.•Interactive relationships between altitude, TN and SOC were depicted by a plot.•TK facilitates nitrogen fixation only in a specific range of amounts.
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