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Cuticle is the first barrier for rice to resist blast fungus on the surface of the leaf. Studies on how the rice leaf cuticle responds to rice blast and attempts to perform early detection of rice blast are limited, and these two issues were explored in this study via depth-profiling Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). Rice leaves with four different scales of injury (healthy leaves as CK, asymptomatic leaves from mildly diseased seedlings as S1, infected leaves with fewer than five lesions as S2, and infected leaves with more than 10 lesions as S3) were scanned by three moving mirror velocities 0.32, 0.47, and 0.63 cm/s for the depth profiling of the rice leaf surface. The response patterns were acquired via chemometrics to analyze the variations of the chemical group absorptions in the different layers of a sample and in the same layer between different samples. Results showed that the leaf cuticle tended to be thicker and the relative content of fatty alcohols and cutin, unsaturated compounds, and aromatics in the cuticle increased when rice seedlings were infected by blast fungus. Together with the principal component analysis, the probabilistic neural network was applied to identify the samples in early stages (CK and S1), which reached an accuracy of 90% for the samples in the greenhouse and 82% for the samples in the field. Thus, depth-profiling FTIR-PAS was good at analyzing the variation in cuticle layers and showed great potential in the early detection of rice blast or other diseases in different species.

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The nitrate-N content in KNO3 solution and soil was rapidly predicted using techniques of mid-infrared spectroscopy, in which 15 NO-3 and 14 NO-3 were distinguished and predicted. The results showed that the characteristic band of nitrate in solution and soil was 1200-1500 cm-1 , and compared with 14 NO-3 , the red shift of characteristic band of 15 NO-3 was about 35 cm-1 . In the characteristic band of nitrate, absorption band increased with the nitrate nitrogen concentration with less interference absorption. The linear regression was made between the first principal component of characteristic band and nitrate-N content, and correlation coefficient was more than 0 . 9840 , indicating that the technique of mid-infrared attenuated total reflectance spectroscopy could be applied for rapid monitoring of nitrate in solution and soil. Meanwhile, based on the red shift characteristic of 15 NO-3 absorption band, the method of partial least squares were involved to predict the nitrate-N of different N-isotope labeled in solution and soil, resulting that all the prediction models reached excellent levels. For 14 NO3-N and 15 NO3-N in solution, the correlation coefficients ( R2 ) were 0. 9980 and 0. 9982 respectively, and ration performance to standard deviations ( RPD ) were 6. 44 and 4. 76, respectively. While for 14 NO3-N and 15 NO3-N in soil, the correlation coefficients ( R2 ) were 0. 9794 and 0. 9679, and RPD were 5. 75 and 4. 78, respectively. Therefore, the technique of mid-infrared attenuated total reflectance spectroscopy can be applied for rapid monitoring different N-isotope labeled nitrate in solution and soil, to provide a new in situ and fast time method to study nitrification process in soil.

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Soil particles are very heterogeneous in microscopic scale, which is manifested the double-layer structure made of the soil organic matter and mineral matter. In this work, Fourier by transform infrared photoacoustic spectroscopy ( FTIR-PAS) combined with independent component analysis ( ICA) was utilized for in situ depth-profiling of the manmade complex film, in order to lay a foundation of in situ characterizing the heterogeneous soil organic-mineral complex. The complex film was composed of the PE preservative film and office adhesive tape. The moving velocity of infrared photoacoustic spectrometer was set to 0. 16 cm/s, 0. 32 cm/s and 0. 64 cm/s, respectively. Independent component analysis ( ICA ) was performed on the photoacoustic spectra of the heterogeneous complex film. Results showed that the depth-resolved information of the complex film could be derived by changing the moving velocity, and the estimated thickness of PE film was 5. 4-7. 6 μm, which was close to the actual thickness 7 ± 1 μm. Moverover, the spectral features of the polyethylene ( PE) preservative film and office adhesive tape were extracted from the photoacoustic spectra of the heterogeneous complex film by means of ICA. Depth profiling of complex film samples showed that FTIR-PAS could be used as a new analytical tool to study heterogeneous soils, especially soil organic-mineral complexes.

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Paddy soils are classified as wetlands which play a vital role in climatic change and food production. Soil carbon (C), especially soil organic C (SOC), in paddy soils has been received considerable attention as of recent. However, considerably less attention has been given to soil inorganic carbon (SIC) in paddy soils and the relationship between SOC and SIC at interface between soil and the atmosphere. The objective of this research was to investigate the utility of applying Fourier transform mid-infrared photoacoustic spectroscopy (FTIR-PAS) to explore SOC and SIC present near the surface (0-10 µm) of paddy soils. The FTIR-PAS spectra revealed an unique absorption region in the wavenumber range of 1,350-1,500 cm(-1) that was dominated by C-O (carbonate) and C-H bending vibrations (organic materials), and these vibrations were used to represented SIC and SOC, respectively. A circular distribution between SIC and SOC on the surface of paddy soils was determined using principal component analysis (PCA), and the distribution showed no significant relationship with the age of paddy soil. However, SIC and SOC were negatively correlated, and higher SIC content was observed near the soil surface. This relationship suggests that SIC in soil surface plays important roles in the soil C dynamics.

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A method to prepare granular palygorskite (GPA) was put forward in this research, and its potential use to remove phosphate species from aqueous solution was assessed. Batch experiments were performed to study the adsorption equilibrium and influence of contact time and pH on the adsorption and desorption of phosphate onto GPA in water. The maximum phosphate adsorption capacity of GPA was 13.1 mg/g. Kinetic data revealed that more than 90% of phosphate was adsorbed onto GPA within 2 hours. Phosphate adsorption capacity was 0.10 mg/g in column experiments, and co-existing anions could decrease phosphate removal. The saturated column was regenerated by 0.2 mol/L sodium hydroxide, and the GPA could be reused in phosphate removal. The data obtained from both batch and column studies indicated that GPA could be used effectively to remove phosphate from water.

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The feasibility of using Fourier transform mid-infrared photoacoustic spectroscopy (FTIR-PAS) for rapid characterization of animal manures was investigated. Animal manure samples were collected from various places in China, and probabilistic neural networks (PNN) and partial least squares (PLS) were initially applied in the qualitative and quantitative analysis of animal manures, respectively. The animal manures exhibited distinctive bands, specifically around 2900-3700 cm(-1), 1200-1800 cm(-1) and 500-1100 cm(-1). There were numerous differences in the spectra of different animal manures, and manures were successful identified by PNN model; organic matter contents in animal manure were well predicted by PLS model, and the calibration coefficient (R(2)), validation error and RPD (ratio of standard deviation to predicted error) were 0.93, 2.38% and 2.58%, respectively, suggesting the potential application of FTIR-PAS for the fast characterization of animal manures.

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This study investigates the use of photoacoustic spectroscopy (PAS) for rapid soil analysis. Photoacoustic spectroscopy requires very minimal sample preparation (air-drying), which is a major advantage compared to the more traditional transmittance technique, which requires time-consuming preparation of pellets. The amount of information contained in the PAS spectra appears to be similar to that contained in transmittance spectra, and the PAS spectra exhibit a large number of bands that can be associated with various soil constituents such as quartz, calcium carbonate, and various types of clay. Comparison with attenuated total reflection (ATR) spectra of saturated soil pastes shows that the PAS spectra provide much more information than the ATR spectra due to the strong water bands present in the latter. PAS quantitative analysis of clay, calcium carbonate, and organic matter is presented, with respective determination errors of approximately 12% clay, approximately 5% CaCO(3), and approximately 0.2% organic matter.

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