Fei Ma

Application of Nano FeIII–Tannic Acid Complexes in Modifying Aqueous Acrylic Latex for Controlled-Release Coated Urea

Acrylic latexes are valuable waterborne materials used in controlled-release fertilizers. Controlled-release urea coated with these latexes releases a large amount of nutrients, making it difficult to meet the requirement of plants. Herein, FeIII-tannic acid (TA) complexes were blended with acrylic latex and subsequently reassembled on a surface of polyacrylate particles. These complexes remarkably retarded the release of urea (the preliminary solubility was decreased from 22.3 to 0.8%) via decreasing the coating tackiness (Tg was increased from 4.17 to 6.42 °C), increasing the coating strength (tensile stress was improved from 3.88 to 4.45 MPa), and promoting the formation of denser structures (surface tension was decreased from 37.37 to 35.94 mN/m). Overall, our findings showed that a simple blending of FeIII-TA complexes with acrylic latex produces excellent coatings that delay the release of urea, which demonstrates great potential for use in controlled-release fertilizers coated with waterborne polymers.

Application of FTIR-PAS and Raman spectroscopies for the determination of organic matter in farmland soils

In soil analysis, Raman spectroscopy is not as widely used as infrared spectroscopy mainly owing to fluorescence interferences. This paper investigated the feasibility of Fourier-transform infrared photoacoustic (FTIR-PAS) and Raman spectroscopies for predicting soil organic matter (SOM) using partial least squares regression (PLSR) analysis. 194 farmland soil samples were collected and scanned with FTIR and Raman spectrometers in the spectral range of 4000-400cm(-1) and 180-3200cm(-1), respectively. For the PLSR models, the combined dataset was split into 146 samples as the calibration set (75%) and 48 samples as the validation set (25%). The optimal number of analytical factors was determined using a leave-one-out cross-validation. The results showed that SOM could be predicted using FTIR-PAS and Raman spectroscopies independently, with R(2)>0.70 and RPD>1.8 for the validation sets. In comparison to the single applications of FTIR-PAS and Raman spectroscopies, accurate prediction of SOM was made by combining FTIR-PAS and Raman spectroscopies, with R(2)=0.81 and RPD=2.18 for the validation sets. By statistically assessing large amounts of PLS models, model-population analysis confirmed that the accuracy of the PLS model can be increased by combining FTIR-PAS and Raman spectroscopies. In conclusion, the combination of FTIR-PAS and Raman spectroscopies is a promising alternative for soil characterization, especially for the prediction of SOM, owing to the availability of complementary information from both FTIR-PAS (polar vibrations) and Raman spectroscopy (non-polar vibrations).

Rapid Determination of N Isotope Labeled Nitrate Using Fourier Transform Infrared Attenuated Total Reflection Spectroscopy

Abstract Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy was utilized to quantify nitrate contents, 14NO3-N and 15NO3-N in KNO3 solution and soil. The results showed that the characteristic band of nitrate in solution and soil was 1200–1500 cm−1, and about 35 cm−1 of red shift was observed in the characteristic band of 15NO3− compared with 14NO3−. The intensity of the characteristic band of nitrate increased with the nitrate concentration and with less interference involved. The linear regression was made between the first principal component of characteristic band and nitrate-N content with a correlation coefficients of 0.9840, which indicated that FTIR-ATR spectroscopy was feasible for rapid monitoring of nitrate in solution and soil. Furthermore, based on the red shift of 15NO3− absorption, partial least squares (PLS) method was employed to predict the nitrate -N labeled with different N-isotope in solution and soil. As a result, all the prediction models were excellent. For 14NO3-N and 15NO3-N in solution, the determination coefficients (R2) were 0.9980 and 0.9982, respectively, and corresponding RPD were 6.44 and 4.76, respectively. For 14NO3-N and 15NO3-N in soil, the determination coefficients (R2) were 0.9794 and 0.9679, respectively, and the corresponding RPD were 5.75 and 4.78, respectively. Therefore, FTIR-ATR spectroscopy can be applied for rapid monitoring different N-isotope labeled nitrate in solution and soil, which provides a new method for in situ and fast analysis of nitrification process in soil.

Characterization of the Release of Urea from Coated Fertilizer by Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance

The development of a simple and cost-effective method for the determination of the release of coated urea has significant implications. Fourier-transform infrared spectroscopy with attenuated total reflectance was employed to determine the release of urea through univariate and multivariate calibration. The results indicated that univariate calibration did not accurately predict the release of urea, whereas partial least squares based on multivariate calibration performed significantly better. Partial least squares had the highest accuracy when the band located at 1420–1520 per centimeter was employed as the input. Moreover, the accuracy was further improved when segmented partial least squares models were developed at low and high urea concentrations. Unsegmented and segmented partial least squares models were employed, and release values were comparable to those measured by colorimetry. This work demonstrated the use of infrared spectroscopy and partial least squares to characterize the release of coated urea.

Quantitative analysis of different nitrogen isotope labelled nitrates in paddy soil using mid-infrared attenuated total reflectance spectroscopy

Nitrogen isotope labelled technology with mass spectroscopy is commonly used to trace the fate of agricultural N in the environment. However, due to mass spectroscopys cost, time consumption and long laborious preparation, Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) was employed to detect different isotope labelled nitrates in this study, and the feasibility of this method was investigated in paddy soil. The results showed that the RPD of a partial least squares regression (PLSR) model were 5.69 and 8.15 mg kg−1 for 14NO3–N and 15NO3–N, respectively, and the RMSEP were 5.60 and 3.91 mg kg−1, respectively, which indicated that the method could well predict the nitrate concentration. The model implementation indicated that the total nitrate concentrations from FTIR-ATR and mass spectrometry were almost the same, among which 15N labelled nitrate obtained by ATR was 3.58–10.02 mg kg−1 lower than that from mass spectrometry, while 14N labelled nitrate from ATR was 6.75–13.68 mg kg−1 higher. Compared with a control treatment, the mineralization and release of soil nitrogen were enhanced in a nitrogen treatment. Therefore, the technique of FTIR-ATR can be used as an alternative option in determining isotope labelled nitrate in paddy soil.

Evaluation of net nitrification rates in paddy soil using mid-infrared attenuated total reflectance spectroscopy

Colorimetry is a conventional method for the determination of soil nitrification rates, and it demands pretreatments and chemical reagents, which make it time and cost consuming. Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) as a simple and fast method was employed in this study, and the feasibility of determination of nitrate contents by FTIR-ATR under different soil conditions was investigated. It was found that the second-order derivatives of nitrate characteristic bands (1270–1320 cm−1) were proportional to nitrate contents, and an excellent correlation coefficient of 0.9751 was obtained, indicating that FTIR-ATR combined with second-order derivatives could be well used for quantification of nitrate. The nitrate-N contents determined by FTIR-ATR and colorimetry increased with increasing incubation time under different treatments including soil temperature, moisture, pH and nitrogen application rate; in most cases, the values obtained by FTIR-ATR were slightly higher than those obtained by colorimetry after 50% incubation. The abiotic immobilization of nitrate and Fe interference in the colorimetric procedure might contribute to this difference. Thus, FTIR-ATR combined with second-order derivatives can be used as an alternative option for fast determination of nitrate under varied conditions in paddy soils.

The Facile Modification of Polyacrylate Emulsion via Hexadecane to Enhance Controlled-release Profiles of Coated Urea

Development of controlled-release urea (CRU) has attracted research attention because of food scarcity problems and environmental concerns. To slow down the nutrient release of CRU coated with waterborne polyacrylate, conventional emulsion polymerization (CEP), conventional emulsion polymerization containing hexadecane (CEP + HD), and miniemulsion polymerization (MP) were carried out to discern the influence of polymerization technique and hexadecane on the properties of emulsions, films, and on the resultant nutrient release profiles of controlled-release urea. The addition of hexadecane improved water resistance, decreased the glass-transition temperature, and slowed down the nutrient release. CEP + HD was superior to MP in retarding nutrient release since the majority of HD was distributed in the exteriors of the particles of the former and interiors of the particles of the latter. Exterior HD improved water resistance more effectively, while interior HD reduced glass-transition temperature more significantly. Overall, our findings showed that incorporation of HD into polyacrylate emulsion produces excellent coatings that delay the release of urea. It has great potential application in controlled-release fertilizers coated with waterborne polymers.

Rapid and Nondestructive Detection of Pesticide Residues by Depth-Profiling Fourier Transform Infrared Photoacoustic Spectroscopy

Detection of pesticide residues is important for ensuring food safety, and it has assumed increased significance. Traditional analytical methods are known for being destructive and cost- and time-intensive. In this study, depth-profiling Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) was successfully used as an in situ, nondestructive, and rapid method for detecting tricyclazole residues on three metal surfaces (copper, aluminum, and iron) and subsequently, on the surfaces of fresh rice leaves and ripe husks. Four moving mirror velocities, that is, 0.32, 0.63, 0.95, and 1.90 cm s–1 were used for recording the spectra. The results indicated that the moving mirror velocity of 0.95 cm s–1 was optimal for depth profiling, and the obtained spectra showed a strong absorption band at around 1200 cm–1, corresponding to the C–N bond in tricyclazole. This band could be used for monitoring tricyclazole residues on plant surfaces. Principal component analysis confirmed the detection of tricyclazole on the basis of its spectral information. Considering the scanning depth and the thickness of the plant cuticle, FTIR-PAS can be an effective means for detecting and monitoring similar organonitrogen pesticide residues.