Quantification of the provenance contribution and sedimentary mixing effect of sediments in the Yellow River Basin, China.

Quantifying the source contributions of sediments in large fluvial systems with active wind erosion problems has crucial implications for understanding morphological evolution and ecological progression in the Earth system. Much effort have been focused on characterizing sediments of the Yellow River, but quantitation of the sediment source proportions at the basin-wide scale is lacking. To this end, the research aims to quantitatively elucidate the potential source contributions of sediments in the Yellow River based on geochemical characteristics and sediment fingerprinting technique, in order to identify sedimentary mixing effect and propose sustainable development strategies. In total, samples of four source groups (n = 107) and target floodplain sediments (n = 61) were collected and tested for elemental composition, grain size, magnetic susceptibility, and quartz grain microtextures. The results indicated that the optimal tracer combination was determined as P, Zn, and Ca. The average contributions of the "Tibetan Plateau", "Sandy deserts-Loess Plateau", "Loess Plateau", and "Loess Plateau-Qinling Mountains" source groups to the target sediments were 23.0 %, 21.5 %, 31.6 %, and 23.9 %, respectively. The accuracy of source apportionments was supported by the goodness of fit (GOF) and virtual mixtures tests. Meanwhile, large amounts of debris from surrounding mountains was transported to the Loess Plateau through fluvial processes and ultimately mixed with aeolian deposits, leading to sedimentary mixing effect. To maintain water balance and minimize erosion risk, the drought-resistant perennial planting and moderate grazing were recommended. The findings are instrumental in promoting soil and water conservation and disclosing fluvial and aeolian interaction on a global scale.

Insights into mineralogical distribution mechanism and environmental significance from geochemical behavior of sediments in the Yellow River Basin, China.

Mineralogical investigations on fluvial sedimentary sequences could provide historical environmental information on the effects of human activities and natural events. This study aims to identify the mineralogical distribution mechanism and environmental significance of sediments of the Yellow River Basin based on topographic analysis, statistics, weathering and recycling indices. In total, 107 samples were collected from sedimentary sequences in the source area, and the upper, middle, and lower reaches and analyzed for grain size, major elements, and mineral composition. The results showed that the climate conditions were cold and arid, where weak hydrolysis under continental weathering and strong erosion accelerated physical weathering. Clay minerals in the upper reaches primarily originated from the Tibetan Plateau, whereas the middle and lower reaches received input of aeolian deposits from Northern China. Quartz and feldspar in the middle and lower reaches may derive from the source area and upper reaches. Meanwhile, calcite and dolomite formed through diagenesis, with loess input from the Chinese Loess Plateau. Regarding heavy minerals, the dominant determinative factors of pyrite were post-depositional diagenesis and leaching. Hematite and amphibole primarily formed through magnetite conversion and contribution from regional sources, respectively. Moreover, the mineral distribution mechanism significantly affected the mobility and distribution of geochemical elements through diagenesis and alteration. The findings are instrumental in reconstructing the environmental evolution of large-scale watersheds across multiple climatic zones.

Theoretical Kinetic Studies on Thermal Decomposition of Glycerol Trinitrate and Trimethylolethane Trinitrate in the Gas and Liquid Phases.

Glycerol trinitrate (NG) and trimethylolethane trinitrate (TMETN), as typical nitrate esters, are important energetic plasticizers in solid propellants. With the aid of high-precision quantum chemical calculations, the Rice-Ramsperger-Kassel-Marcus (RRKM)/master equation theory and the transition state theory have been employed to investigate the decomposition kinetics of NG and TMETN in the gas phase (over the temperature range of 300-1000 K and pressure range of 0.01-100 atm) and liquid phase (using water as the solvent). The continuum solvation model based on solute electron density (SMD) was used to describe the solvent effect. The thermal decomposition mechanism is closely relevant to the combustion properties of energetic materials. The results show that the RO-NO2 dissociation channel overwhelmingly favors other reaction pathways, including HONO elimination for the decomposition of NG and TMETN in both the gas phase and liquid phase. At 500 K and 1 atm, the rate coefficient of gas phase decomposition of TMETN is 5 times higher than that of NG. Nevertheless, the liquid phase decomposition of TMETN is a factor of 5835 slower than that of NG at 500 K. The solvation effect caused by vapor pressure and solubility can be used to justify such contradictions. Our calculations provide detailed mechanistic evidence for the initial kinetics of nitrate ester decomposition in both the gas phase and liquid phase, which is particularly valuable for understanding the multiphase decomposition behavior and building detailed kinetic models for nitrate ester.

Natural-human driving factors of groundwater salinization in a long-term irrigation area.

Salinization of groundwater is a major challenge for groundwater management in long-term irrigation areas, decoupling its complex influencing factors can provide insights for the sustainable development of irrigation areas. In this study, the natural-human driving factors of groundwater salinization in the Yinchuan Plain, a typical irrigated area, were identified using isotope analysis, information entropy, and self-organizing map. Results show that groundwater in the study area is seriously salinized with obvious spatial heterogeneity. Multiple natural conditions and frequent human activities complicate the salinization characteristics of groundwater. On this basis, four typical natural influence units of groundwater were identified, namely, an evaporation and upward leakage zone, a runoff zone, an evaporation zone, and a runoff and upward leakage zone. Information entropy was proposed to quantify the complexity of groundwater resulting from human activities: The complexity difference between densely populated areas and natural dominant areas is mainly reflected in Na+, SO42-, and Cl-. Multiple human-made drivers of complex water environment were further separated into three patterns by the SOM model: blockage-evaporation type, leakage-evaporation type, and irrigation type. The blockage of drainage ditches and obstruction of salt discharge has the highest impact on the salinization of groundwater, followed by irrigation activities and transportation losses. Water excessive stagnation caused by blockage or irrigation is the root cause of groundwater salinization in the irrigated area, and its impact is greater than that of the traditional understanding of groundwater level rise. Based on the evaluation of irrigation water quality, management initiatives for irrigated areas should prioritize dredging and maintaining a healthy soil and groundwater environment in tandem.

Characterization of soil salinization and its driving factors in a typical irrigation area of Northwest China.

Salinization of irrigation areas is a global environmental challenge. The uncertainty in the distribution of salinization is increased by the complexity of the natural environment. This study adopted Yinchuan Plain as a typical irrigation area to study the relationship between soil salinity and the environment from the perspective of macro-environmental elements and micro-ion composition. A Geographic Weighted Regression model (GWR) was used to predict the risk of salinization in the Yinchuan Plain. The results showed obvious spatial variation in soil salinization in the Yinchuan Plain. Farmland accounted for the largest proportion of salinized land area, followed by woodland and "other" land use categories. The main characteristic ions in the salinized area of the Yinchuan Plain were SO42-, K++Na+and Cl-. The rank of ions in terms of change rate with increasing soil salinity was: SO42- > K+ + Na+ > Cl- > Ca2+ > HCO3- > Mg2+ > CO32-. However, the rank of ions in terms of their sensitivity to salinization was: HCO3- > Ca2+ > Mg2+ > SO42- > Cl- > K+ + Na+. On this basis, the geographical indicators of DEM and NDVI, groundwater indicators of groundwater depth and TDS, climate indicators of SPEI, as well as soil indicators of PH and organic matter were taken as the representative ecological drivers of salinization in irrigation areas. These environmental factors were found to control the distribution of salinization, whereas human activity affected the degree of change in salinization. The enrichment of SO42- in the Yinchuan Plain was mainly related to agricultural activities (such as pesticides application and irrigation evaporation), and followed by phreatic evaporation. The salt ions carried by irrigation and rainfall further polluted phreatic water. In the end, the measures of optimizing drainage, combined irrigation, and improving planting layout were recommended for the effectively and economically controlling of salinization.

Hydrogeochemical evidence for fluoride behavior in groundwater and the associated risk to human health for a large irrigation plain in the Yellow River Basin.

A hydrochemical analysis of groundwater (GW) was conducted to investigate the factors controlling GW fluoride (F) in a large irrigation plain in the Yellow River Basin, Guanzhong Plain, China. Area-dependent variations in F were observed in the study region. The F concentrations of 93% of samples on the south bank of the Weihe River and the western part of the Qishui River were <1 mg L-1, whereas those of 73% of GW samples for the eastern part of the Qishui River exceeded the national limit. A forward model based on mass budget equations identified carbonate weathering as the dominant factor regulating hydrochemistry in low-F GW, whereas the factors in the high-F zone were evaporate dissolution and evaporation. The high-F GW displayed a distinctive major ion chemistry, which could be attributed to a high pH, low Ca2+, and high HCO3- and Na+ concentrations. An analysis of the correlation between F/Cl and F concentrations and fluid-mineral equilibria indicated distinct forces driving the behavior of F in the subparts of the high-F GW zone, including irrigation-induced F dilution, F enrichment through Na-Ca exchange, and adsorption of F on clay minerals. The order of vulnerable segments of the population in terms of risk posed by F in GW was: infants > children > adults. These results can enhance the understanding of F behaviors in GW and provide insights into the effect of irrigation practices on GW F concentration.

Pb Single Atoms Enable Unprecedented Catalytic Behavior for the Combustion of Energetic Materials.

Manipulating the thermal decomposition behavior of energetic materials is the key to further pushing the combustion performance of solid rocket propellants. Herein, atomically dispersed Pb single atoms on polydopamine (PDA-Pb) are demonstrated, which display unprecedented catalytic activity toward the thermal decomposition of cyclotrimethylenetrinitramine (RDX). Impressively, RDX-based propellants with the addition of PDA-Pb catalyst exhibit substantially enhanced burning rates (14.98 mm s-1 at 2 MPa), which is 4.8 times faster than that without PDA-Pb and represents the best catalytic performance among Pb-based catalysts. Moreover, it also possesses low-pressure exponents in broad pressure ranges, which can enable more stable and safer combustion in solid rocket engines. Theoretical calculation unravels the efficient catalytic activity is stemmed from the enhanced interfacial electronic coupling between RDX and PDA-Pb via orbital level engineering. More importantly, PDA-Pb also presents similar catalytic behavior toward the decomposition of nitrocellulose, suggesting its broad catalytic generality. This work can open up new opportunities in the field of energetic compound combustion by exploring Pb-based single atom catalysts and beyond.

Evaluation of groundwater quality using an integrated approach of set pair analysis and variable fuzzy improved model with binary semantic analysis: A case study in Jiaokou Irrigation District, east of Guanzhong Basin, China.

The study proposes a new set pair analysis - variable fuzzy improved model (SPA-VFIM) by integrating the set pair analysis (SPA), variable fuzzy sets (VFS) theory, and binary semantic (BS). The SPA-VFIM method gets over the shortcomings of the existing SPA and VFS methods. The use of BS solves the problem of the weighted average principle (WAP) not being conducive to the timeliness of assessment. The existing and newly proposed methods were used to evaluate the groundwater quality in the Jiaokou Irrigation District, China, to show the advantages of the SPA-VFIM method. The results of SPA-VFIM method show that more than 80% of the groundwater, mainly distributed in the central and western parts of the study region, is assessed as level IV and level V, according to the Chinese Groundwater Quality Standards (GB/T 14848-2017). The assessment results are consistent with ground-based measurements of water quality, and NO3-, Na+, SO42-, Total Hardness (TH), and Cl- are the main pollutants. The SPA-VFIM and existing methods were compared. The results indicate that 57.69% and 76.92% of the assessment results by the SPA-VFIM method agree well with that of the SPA and VFS methods, respectively, indicating that the new SPA-VFIM method is reasonable and effective in groundwater quality. The results of groundwater quality assessment show that local authorities should pay more attention to areas with poor and very poor groundwater quality. These findings are beneficial to the future groundwater management plans dealing with drinking and irrigation and the sustainable development of water resources in this irrigation district.

Fluoride Occurrence and Human Health Risk in Drinking Water Wells from Southern Edge of Chinese Loess Plateau.

Fluoride hydrogeochemistry and associated human health risks implications are investigated in several aquifers along the southern edge of the Chinese Loess Plateau. Locally, 64% shallow groundwater samples in loess aquifer exceed the fluoride limit (1.5 mg/L) with the maximum of 3.8 mg/L. Presently, the shallow groundwater is the main source of private wells for domestic use, and this is clearly a potential risk for human health. Hydrogeochemistry and stable isotopes are used to elucidate the diversity of occurrence mechanisms. Enrichment of fluoride in groundwater is largely controlled by the F-containing minerals dissolution. Furthermore, alkaline condition and calcium-removing processes promote water-rock interactions. Stable isotopes of hydrogen and oxygen (δD and δ18O) in study area waters demonstrate that groundwater in loess aquifer is old, which means groundwater remains in the aquifer for a long time. Long residence time induces sufficient water-rock interactions, which play significant roles in the resolution of fluoride minerals. Samples from the shallow loess aquifer show elevated fluoride levels, which may pose human health risk for both adults (60%) and children (94%) via oral intake. To ensure drinking water safety, management measures such as popularizing fluoride-removing techniques and optimizing water supply strategies need to be implemented.

The role of sodium carbonate in PAM coagulation-flocculation for oil acidized wastewater treatment.

The pH value of oil acidized wastewater is relatively low (pH = 6.1), which seriously affects the flocculation of polyacrylamide (PAM). NaOH was used to adjust the pH value, but the maximum was only 7.5. The regulation was limited as the Ca2+ in aqueous phase up to 1,350 mg L-1 consumed OH-. A novel formulation of Na2CO3 + PAM was proposed to form CaCO3 floc core to facilitate PAM coagulation. When the concentration was above 400 mg L-1, the PAM precipitation tended to be maximum, followed by NaOH adjustment of pH to 8.0 that could enhance PAM flocculation successively. The sewage sludge (SS) remained and residue oil reduced to 25 mg L-1 and 34mg L-1 respectively. The analysis of the species and composition of fatty acids indicated that the coagulation-flocculation selectively effected the sedimentation of saturated fatty acids (SAT). This provides a new idea for recovery of high value-added residual oil. The optimal additive of Na2CO3 is expected as promising coagulant aid to improve the PAM coagulation-flocculation of oil acidized wastewater.

A silver nanoparticle based surface enhanced resonance Raman scattering (SERRS) probe for the ultrasensitive and selective detection of formaldehyde.

Here we report a silver nanoparticle based surface enhanced resonance Raman scattering (SERRS) probe for the ultrasensitive and selective detection of formaldehyde. The detection limit reaches as low as 10(-11) M.

High yield synthesis of matchstick-like PbS nanocrystals using mesoporous organosilica as template.

A simple hard template method has been developed to prepare uniform matchstick-like PbS nanocrystals. The approach combines functionalization of the mesoporous walls and channel surface with thioether groups, adsorption of Pb2+, and heating in an N2 atmosphere at high temperature. The structure, morphology and composition of the nanocrystals have been characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The optical properties of the matchstick-like PbS nanocrystals have been systematically investigated by Raman spectroscopy, UV-visible absorption spectroscopy (UV-vis), and photoluminescence spectroscopy (PL). These results demonstrate that these matchstick-like PbS nanocrystals are single crystals and possess novel optical properties, suggesting that they may have many potential applications. A large blue shift is observed in the photoluminescence spectrum, and this clearly shows the quantum size effects of the matchstick-like PbS . Furthermore, a growth mechanism of the PbS heteronanostructure is proposed.

Plasmonic resonance energy transfer-based nanospectroscopy for sensitive and selective detection of 2,4,6-trinitrotoluene (TNT).

Here we report sensitive and selective detection of TNT based on plasmonic resonance energy transfer from a gold nanoplasmonic probe to conjugated target TNT molecules, leading to quenching on the Rayleigh scattering spectrum of the probe.