Wet Precipitation Research Articles

Automated Cropland Fallow Algorithm (ACFA) for the Northern Great Plains of USA

ABSTRACT Cropland fallowing is choosing not to plant a crop during a season when a crop is normally planted. It is an important component of many crop rotations and can improve soil moisture and health. Knowing which fields are fallow is critical to assess crop productivity and crop water productivity, needed for food security assessments. The annual spatial extent of cropland fallows is poorly understood within the United States (U.S.). The U.S. Department of Agriculture Cropland Data Layer does provide cropland fallow areas; however, at a significantly lower confidence than their cropland classes. This study developed a methodology to map cropland fallows within the Northern Great Plains region of the U.S. using an easily implementable decision tree algorithm leveraging training and validation data from wet (2019), normal (2015), and dry (2017) precipitation years to account for climatic variability. The decision trees automated cropland fallow algorithm (ACFA) was coded on a cloud platform utilizing remotely sensed, time-series data from the years 2010–2019 to separate cropland fallows from other land cover/land use classes. Overall accuracies varied between 96%-98%. Producer’s and user’s accuracies of cropland fallow class varied between 70-87%.

Electron paramagnetic resonance and luminescence spectroscopy of transition metal ion impurities and X-ray-induced radicals in brushite

Calcium phosphates hold paramount importance as the constituents of hard tissue of living organisms. Among them, brushite (CaHPO4·2H2O), also known as dicalcium phosphate dihydrate (DCPD), is a common precursor in phosphate synthesis and is becoming increasingly appealing as a biomaterial for bone regeneration applications. This study presents a comparative analysis of structural, morphological, thermal, and spectroscopic properties of synthetic brushite prepared by the wet precipitation method with several brushite products available from commercial vendors. Electron paramagnetic resonance (EPR) spectroscopy revealed that Mn2+ and Fe3+ ions are common trace impurities in commercial products. Following exposure to X-rays, EPR signals of several phosphorous-related radicals emerge. The annealing of the irradiated samples gives rise to broad thermally stimulated luminescence (TSL) signals in the 40–120 °C range, which correlates with the annealing kinetics of the radicals. The stability of radiation-induced EPR and TSL signals is limited by the phase transformation temperature from brushite to monetite (CaHPO4). The results of this study provide novel insights into the formation and stability of phosphorous-related radicals and demonstrate how minuscule amounts of impurity ions can strongly influence the spectroscopic properties of brushite.

Leveraging regional mesh refinement to simulate future climate projections for California using the Simplified Convection-Permitting E3SM Atmosphere Model Version 0

Abstract. The spatial heterogeneity related to complex topography in California demands high-resolution (< 5 km) modeling, but global convection-permitting climate models are computationally too expensive to run multi-decadal simulations. We developed a 3.25 km California climate modeling framework by leveraging regional mesh refinement (CARRM) using the U.S. Department of Energy (DOE)'s global Simple Cloud-Resolving E3SM Atmosphere Model (SCREAM) version 0. Four 5-year time periods (2015–2020, 2029–2034, 2044–2049, and 2094–2099) were simulated by nudging CARRM outside California to 1° coupled simulation of E3SMv1 under the Shared Socioeconomic Pathways (SSP)5-8.5 future scenario. The 3.25 km grid spacing adds considerable value to the prediction of the California climate changes, including more realistic high temperatures in the Central Valley and much improved spatial distributions of precipitation and snowpack in the Sierra Nevada and coastal stratocumulus. Under the SSP5-8.5 scenario, CARRM simulation predicts widespread warming of 6–10 °C over most of California, a 38 % increase in statewide average 30 d winter–spring precipitation, a near-complete loss of the alpine snowpack, and a sharp reduction in shortwave cloud radiative forcing associated with marine stratocumulus by the end of the 21st century. We note a climatological wet precipitation bias for the CARRM and discuss possible reasons. We conclude that SCREAM RRM is a technically feasible and scientifically valid tool for climate simulations in regions of interest, providing an excellent bridge to global convection-permitting simulations.

An assessment of inorganic components in condensable particulate matter as a function of surface aggregation, spatial suspension state and particle size

Experimental studies assessed the removal efficiency and fine-size distribution of CPM coupled with compositional analysis across air pollution control device systems (APCDs) at an ultra-low emission (ULE) power plant. The findings indicated total CPM emissions were reduced to a minimum of 0.418 mg/m3 at the Wet Electrostatic Precipitator (WESP). The Wet Flue Gas Desulfurization (WFGD) showed the highest removal efficiency (98%) across all particle sizes, notably in the ultra-micron range. Selective Catalytic Reduction (SCR) demonstrated a mere 34% overall efficiency, with a negative removal rate in the ultra-fine particle range. The WESP effectively removed CPM only in sub-micron and ultra-micron sizes, but significantly increased water-soluble ions formation in ultra-fine spatially suspended CPM (CPMspa), leading to overall negative efficiency. Thus, the removal efficiency of the ultra-fine particle range was most affected among the three particle size ranges when the flue gas went through the APCDs. Major metal elements and water-soluble ions were more readily removed by APCDs due to their surface aggregation, while the removal of trace elements like Hg and Se was limited. Reducing SO42-/NH4+ formation in SCR, and optimizing WESP spray system operations based on flue gas components are essential steps in controlling CPM concentration in ULE power plants.

Correlation between positron annihilation lifetime and photoluminescence measurements for calcined Hydroxyapatite

Hydroxyapatite (HAp) Ca10(PO4)6(OH)2 is a compound that has stable chemical properties, composition, and an affinity for human bone. As a result, it can be used in odontology, cancer treatment, and orthopedic grafts to repair damaged bone. To produce calcined HAp at 600 °C with different pH values, a wet chemical precipitation method was employed. All synthesized HAp samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL), Zeta potential, and positron annihilation lifetime spectroscopy (PALS). The XRD results revealed that all calcined HAp samples were formed in a hexagonal structure with a preferred (002) orientation at different pH values. The crystal size of the samples was determined using the Scherrer equation, which ranged from 16 to 25 nm. The SEM and TEM results showed that the morphology of the samples varied from nanorods to nanospheres and rice-like structures depending on the pH value of the sample. The PL measurements indicated that the blue and green emission peaks of HAp were due to defects (bulk, surface, and interface) in the samples, which created additional energy levels within the band gap. According to Zeta potential measurements, the charge carrier changed from a positive to negative value, ranging from 3.94 mV to − 2.95 mV. PALS was used to understand the relationship between the defects and the photoluminescence (PL) properties of HAp. Our results suggest that HAp nanoparticles have excellent potential for developing non-toxic biomedical and optical devices for phototherapy.

Spatial and Temporal Evolution of Precipitation in the Bahr el Ghazal River Basin, Africa

Accurate and punctual precipitation data are fundamental to understanding regional hydrology and are a critical reference point for regional flood control. The aims of this study are to evaluate the performance of three widely used precipitation datasets—CRU TS, ERA5, and NCEP—as potential alternatives for hydrological applications in the Bahr el Ghazal River Basin in South Sudan, Africa. This includes examining the spatial and temporal evolution of regional precipitation using relatively accurate precipitation datasets. The findings indicate that CRU TS is the best precipitation dataset in the Bahr el Ghazal Basin. The spatial and temporal distributions of precipitation from CRU TS reveal that precipitation in the Bahr el Ghazal Basin has a clear wet season, with June–August accounting for half of the annual precipitation and peaking in July and August. The long-term annual total precipitation exhibits a gradual increasing trend from the north to the south, with the southwestern part of the Basin having the largest percentage of wet season precipitation. Notably, the Bahr el Ghazal Basin witnessed a significant precipitation shift in 1967, followed by an increasing trend. Moreover, the spatial and temporal precipitation evolutions reveal an ongoing risk of flooding in the lower part of the Basin; therefore, increased engineering counter-measures might be needed for effective flood prevention.

Changes of Wet Precipitation Flux and Pollutants associated with at Chongqing Urban Station from 2008 to 2020 and Influencing Factors

Changes of Wet Precipitation Flux and Pollutants associated with at Chongqing Urban Station from 2008 to 2020 and Influencing Factors

Optimization of Nanohydroxyapatite for Bone Tissue Engineering via Wet Chemical Precipitation Method

Optimization of Nanohydroxyapatite for Bone Tissue Engineering via Wet Chemical Precipitation Method

Industrial application and numerical simulation on discrete dynamics of fine particulate matters: Condensational growth, deposition and agglomeration

The removal effects of multiple discrete dynamic mechanisms on particulate matters (PMs) are of great significance for industrial application and basic research. In this work, a wet phase transition agglomerator (WPTA) is installed between a wet electrostatic precipitator (WESP) and a stack at a 280 t/h coal-fired power plant. The removal effects of the WPTA are compared with those of the WESP by field measurement. Meanwhile, a numerical model for predicting particle size distributions is developed and verified through the experimental data. The results indicate that the WPTA reduces the emission concentrations of PM1 and PM2.5 to 0.64 mg/Nm3 and 0.89 mg/Nm3, respectively. The PM1 removal efficiencies for the independent WPTA, the independent WESP and the combined method are 33.07 %, 40.31 % and 58.36 %, respectively. The microscopic morphologies of the fine PMs in the particle size range of 0.98–1.64 μm exhibit blocky, spherical and crystal structure. The simulated errors of PM1, PM2.5 and PM10 are 7.81 %, 7.87 % and 12.27 %, respectively. The boundary layers of the tube bundle are conducive to strengthening thermophoretic force and supersaturation. Consequently, the WPTA can effectively replace the WESP to achieve the emission control of fine PMs in industrial applications. The developed numerical model can accurately predict the particle size distributions in the WPTA.

Synergistic Humidification and Chemical Agglomeration to Improve Capturing the Fine Particulate Matter by Electrostatic Precipitator

The wet electrostatic precipitator (WESP) overcomes the shortcomings of traditional electrostatic precipitators, such as dust re-entrainment and back corona. It can effectively remove high-specific-resistivity dust, with a good removal effect on PM2.5. It is proposed to adopt chemical agglomeration and humidification agglomeration technology in the wet electrostatic precipitators to achieve ultra-low dust emissions from coal-fired power plants. The results show that the addition of chemical agglomerates, surfactants, and water vapor all affect the dust diameter of coal-fired power plants. After adding sesbania gum (SG), the D50 of dust particles increases from 28.29 μm to 48.22 μm. And the D50 of dust particles is 36.46 μm when spraying 3.6 kg/h water vapor only. With the cooperation of chemical agglomeration agents and water vapor, the dust agglomeration effect and removal efficiency can be further improved. When 10 mg/L SG is synergistically combined with 2.9 kg/h water vapor, the D50 is 64.75 μm, and the dust removal efficiency reaches 97.88%. On this basis, by adding 5 mg/L of Hexadecyltrimethylammonium bromide (CTAB), the D50 is 83.06 μm, and the dust removal efficiency increases to 98.62%. The synergistic effect of chemical agglomeration and humidification agglomeration promotes the aggregation of dust from coal-fired power plants. It can improve the removal efficiency of WESP for fine particulate matter but has little impact on the operation of existing equipment. The synergistic effects of multiple agglomeration technologies are also the direction for future research on the removal efficiency of fine particulate matter.

Multifunctional Sr, Mg, Ag-substituted octacalcium phosphate/carboxymethyl chitosan scaffolds: Antibacterial activity and osteogenic differentiation of human mesenchymal stem cells

Numerous studies indicate that octacalcium phosphate (OCP) possesses promising bone regenerative properties. To further improve the regenerative properties of OCP, several ionic substitutions have been proposed. However, knowledge regarding the synergic effect of multiple ions substituted in OCP crystals and fabricated scaffolds is lacking. In this work, plate-like OCP crystals substituted with 1 and 2.5 mol.% of Mg2+, Sr2+ and Ag+ were prepared by the wet precipitation method. Rietveld refinement analysis indicated a successful substitution of Ca2+ by Mg2+, Sr2+and Ag+ ions. The prepared substituted OCP powders showed a high antibacterial effect towards Gram-negative and Gram-positive bacteria. Further, composite scaffolds based on substituted OCP and carboxymethyl chitosan were prepared by the freeze-crosslinking method. The scaffolds had a highly porous structure, with interconnected pores and homogeneously dispersed OCP within the polymer matrix, and high stability in simulated physiological conditions during 28 days. Good viability and proliferation of human bone marrow-derived mesenchymal stem/stromal cells were confirmed by Live/Dead and CyQUANT assays. Additionally, successful osteogenic differentiation was confirmed by quantification of alkaline phosphatase activity and immunocytochemical staining for type I collagen. Results indicate that ionic substitutions with 1.0 mol.% have the most beneficial effect on stem cell differentiation towards osteoblast phenotype.

One step synthesis of FeOx magnetic nanoparticles in the microreactor with intensively swirling flows

One step method of iron oxides nanoparticles synthesis using novel type of microreactors was reported. All the data received from analysis of physical and chemical properties demonstrated that the nanoparticles obtained by means of the new method are similar to the nanopowders synthesized by wet precipitation. They are magnetite-maghemite solid solutions with unit cell parameter between 8.362 and 8.374 Å, with coherent scattering range values about 9 nm. In comparison with precipitated nanopowders they have lesser degree of agglomeration. Samples obtained in microreactor have smaller value and smaller spread in regard of the specific surface (76–86 m2/g) in comparison with precipitated ones (75–125 m2/g). All the samples from microreactor consist of spherical inhomogeneities with a diffuse surface, while sample of iron oxide nanopowder synthesized by the co-precipitation method consists of scattering cylindrical inhomogeneities with nearly smooth phase boundary. It was shown that microreactor with intensively swirling flows has demonstrated several advantages: (i) possibility to control the degree of oxidation of the product which depends on the flow rates of reagents solutions to the reactor; (ii) high productivity (up to 7 L/min for the suspension with particles, approx. 200 kg/day for the dried particles) that eases the scaling-up of the proposed synthesis method.

Copper-doped ZIF-67/wood aerogel for effective peroxymonosulfate activation

Metal-organic frameworks (MOFs), composed of metal ions and organic linkers, have garnered enormous attention in catalytic application due to their exceptional characteristics such as high specific surface area, low density, large porosity and structural diversity. However, the recycling and performance improvement of MOF should be taken into account in material design. In this work, we fabricated copper-doped metal-organic framework/wood aerogel composites to enhance the activation of peroxymonosulfate (PMS) for the degradation of organic contaminants. Wood Aerogel (WA) was used as suitable carrier to solve the recycling problem, and copper-doped ZIF-67 was developed to enhance the catalytic performance. Copper-doped ZIF-67 (ZIF-67B) was loaded into the cavities of a wood aerogel by in situ wet chemical precipitation, followed by freeze drying to obtain the composite. The effects of copper doping ratio, temperature, catalyst dosage, initial pH and other operational parameters on the degradation of organic pollutants were comprehensively investigated. The catalytic capacity of ZIF-67B@WA (CoxCu(1-x)) was investigated by activating PMS for the removal of Rhodamine B (RhB). The results demonstrate that the degradation efficiency of ZIF-67B@WA (CoxCu(1-x)) towards RhB can achieve 100 % within 15 min, showing exceptional catalytic performance compared with ZIF-67@WA. Even after four consecutive cycles, the degradation efficiency remains at 87.5 %, indicating that the catalyst has good cycle stability. Additionally, possible degradation mechanisms are proposed in this study, in which WA provides high loading active site/area for MOF catalyst and Cu doping can accelerate electron transfer and facilitate the redox cycling of Co2+ and Co3+, thereby enhancing catalytic efficiency. This work expands the application scope of MOF materials in environmental remediation and holds promising prospects.

Laser-assisted synthesis of nano-hydroxyapatite and functionalization with bone active molecules for bone regeneration

The main goal of bone tissue engineering research is to replace the allogenic and autologous bone graft substitutes that can promote bone repair. Owing to excellent biocompatibility and osteoconductivity, hydroxyapatite is in extensive research and high demand for both medical and non-medical applications. Although various methods have been developed for the synthesis of hydroxyapatite, in the present study we have shown the use of nanosecond laser energy in the wet precipitation method of nano-hydroxyapatite (nHAP) synthesis without using ammonium solution or any other chemicals for pH maintenance. Here, the present study aimed to fabricate the nanohydroxyapatite using a nanosecond laser. The X-ray diffraction and Fourier transform infrared spectroscopy have confirmed the hydroxyapatite formation under laser irradiation in less time without aging. A transmission electron microscopy confirmed the nano size of synthesized nHAP, which is comparable to conventional nHAP. The length and width of the laser-assisted nHAP were found to be in the range of 50–200 nm and 15–20 nm, respectively, at various laser parameters. The crystallite size obtained by Debye Scherrer formulae was found to be in the range of ∼ 16–36 nm. In addition, laser-assisted nHAP based composite cryogel (nanohydroxyapatite/gelatin/collagen I) was synthesized and impregnated with bioactive molecules (bone morphogenic protein and zoledronic acid) that demonstrated significant osteogenic potential both in vitro in cell experiment and in vivo rat muscle pouch model (abdomen and tibia muscles). Dual-energy X-ray analysis, micro-CT, and histological analysis confirmed ectopic bone regeneration. Micro-CT based histomorphometry showed a higher amount (more than 10-fold) of mineralization for animal groups implanted with composite cryogels loaded with bioactive molecules compared to only composite cryogels groups. Our findings thus demonstrate a controlled and rapid synthetic method for the synthesis of nHAP with various physical, chemical, and biological properties exhibited as comparable to conventionally synthesized nHAP.

Fabrication of biomimetic scaffold through hybrid forming technique

AbstractBone tissue engineering procedures require the use of a scaffold with a sufficiently porous structure, which serves as a three‐dimensional template for cell attachment, followed by tissue regeneration and vascularization both in vitro and in vivo. This study aimed to create scaffold material with a unique hybrid forming that met these parameters. Slip casting and freeze‐drying processes were used with a hybrid forming approach to create a bone scaffold based on hydroxyapatite (HA) mimicking the structure of cortical and cancellous bones, respectively. HA was synthesized by the wet chemical precipitation method. Fourier‐transform infrared spectroscopy, dynamic light scattering, X‐ray diffraction, thermogravimetric analysis‐differential thermal analysis, Brunauer‐Emmett‐Teller, He Pycnometer, and scanning electron microscope analyses were performed to characterize the scaffold. According to analysis results, HA particle size was found at 137.8 nm. The optimum sintering temperature was determined to be 1300°C. The specific surface area of the HA powder was measured as 55.11 m2/g. The total open porosity of the hybrid scaffold was calculated as 70%. Scaffold successfully substituted both cancellous and cortical layers of bone regarding structural characteristics, porosity, and mechanical strength. Considering morphological characteristics, a hybrid scaffold might facilitate vascularization, osteoinduction, and osteoconduction. Research findings suggest that the hybrid design strongly resembled natural bone and is suitable for both load‐bearing and non‐bearing bones.

Sea surface temperature driven modulation of decadal co-variability in mean and extreme precipitation

This study investigates the role that sea surface temperature (SST) variability plays in modulating the relationship between decadal-scale mean precipitation and monthly-scale extreme precipitation using the Australian Community Climate and Earth System Simulator Earth System model (ACCESS ESM1.5) climate model. The model large ensemble successfully reproduces the observed strong co-variability between monthly mean rainfall and wet extreme rainfall, defined as monthly rainfall totals above the 95th percentile. Removing SST variability in the ACCESS ESM1.5 model significantly weakens the co-variability between mean and wet extremes over most of the globe, showing that SSTs play a key role in modulating this co-variability. The study identifies Pacific and Atlantic SST patterns as the main drivers of the decadal scale co-variability in mean and extreme wet precipitation. On the other hand, observations and model results show that co-variability between mean and dry extremes is generally weaker than for wet extremes, with highly regional signals. Model experiments also show that SST variability plays a weaker role in modulating the co-variability between the mean precipitation and dry extremes as compared to wet extremes. These results suggest that stochastic atmospheric variability plays a stronger role in generating dry precipitation extremes compared SST forcing.

Experimental drought reduces the productivity and stability of a calcareous grassland

Abstract Grasslands, which encompass 40% of terrestrial ecosystems, hold global significance for food production, carbon storage and other ecosystem services. However, grasslands across the biosphere are becoming increasingly exposed to both wet and dry precipitation extremes resulting from climate change. Therefore, understanding how grasslands will respond to precipitation extremes is a pressing issue for managing changes to biodiversity and ecosystem service provision. Here, we use experimental manipulations of precipitation (50% increase and 50% decrease in growing‐season precipitation) over 6 years to investigate the stability and resistance of both productivity and community diversity in a calcareous grassland community. We found that decreased growing‐season precipitation led to reductions in mean productivity (25% decrease in peak above‐ground biomass) and its temporal stability (54% increase in the coefficient of variation of biomass across years). Productivity losses were more pronounced for graminoids and legumes, but this was not reflected in species per cent cover. Community composition was resistant to the precipitation manipulations, with no clear differences in overall community compositional turnover, dissimilarity or biodiversity indices. There was also no detectible effect of increased precipitation on productivity or community composition, which may indicate a lack of efficacy of the irrigation treatment in increasing soil moisture. Finally, the precipitation manipulations had no effect on temporal trends of community change, with an overall increase in richness and shift in grassland community composition across the study period independent of treatment. Synthesis. While the diversity and composition of this calcareous grassland was resistant to precipitation extremes (at least in the short term), sustained reductions in growing‐season precipitation reduced productivity and its temporal stability, particularly for graminoids and legumes. Therefore, we highlight that different properties of grasslands can vary in their responses to changes in precipitation.

Enhancement of energy storage in nanocomposite thin films: Investigating PVDF-ZnO and PVDF-TZO for improved dielectric and ferroelectric characteristics

In contrast to a polymer nanocomposite for high energy density application, a lead-free material such as zinc oxide (ZnO) and a non-toxic polymer matrix such as polyvinylidene fluoride (PVDF) can serve as a potential candidate for use in eco-friendly applications. In the present report, an effort has been made to enhance the dielectric behaviour of the PVDF-based nanocomposites by adding ZnO nanoparticles (NPs) and TiO2-coated ZnO NPs (TZO) as nanofillers. A wet chemical precipitation technique was adopted to synthesize the thin films of PVDF,PVDF-ZnO, and PVDF-TZO nanocomposites. The structural, dielectric, ferroelectric, and energy density studies of PVDF, PVDF-ZnO, and PVDF-TZO nanocomposites thin films were performed for different concentrations (10%, 20%, 30%, and 40%) of nanofillers. Structural characterization carried out using x-ray diffraction studies confirmed the formation of PVDF-ZnO and PVDF-TZO nanocomposite thin films as the diffraction peaks (110) and (200) belonging to β-phase of PVDF, and (100, (002), (101), (110), (103), (200), (112), and (210) peaks were observed for ZnO, and (200), (116), (202) peaks belonging to TiO2 in case of PVDF+ 10% TZO and PVDF+40% TZO thin films. The functional groups belonging to β-phase of PVDF and ZnO were detected using a Fourier transform infrared spectrometer (FTIR). The surface microstructural of pure PVDF thin films showed spherulites and microimages of PVDF+ 10% ZnO and PVDF+ 10% TZO thin films depicted the inhomogeneous distribution of particles in the PVDF matrix. The maximum value of the dielectric constant, the maximum value of energy density, maximum remnant polarization, and the minimum value of dielectric loss for PVDF-TZO. PVDF-TZO thin films show an energy density of 65.3 μJ/cm3 for 40% of the nanofiller (TZO).

Characterizing variability of spatial patterns of annual and seasonal precipitation of Turkey and identifying the probable driving factors including teleconnection patterns

Abstract This study aimed to identify primary modes of annual and seasonal precipitation in Turkey using a rotated Empirical Orthogonal Function (EOF) method, and the resulting patterns were described concerning the prevalent atmospheric circulations, orography, and continentality. The varimax rotation of the EOF determines modes that are more localized in space than the conventional EOF modes The first three EOFs accounted for approximately 67% and 62% of the total variance in the annual and wet season precipitation series, respectively, whereas only 50% of the variance was captured by the first three EOFs for dry season precipitation. Spatially different atmospheric circulation mechanisms are major drivers of variability in Turkish precipitation on annual and seasonal timescales. The spatial coherence of the highest negative and positive EOF1 loadings of the annual data was observed in the western and southern regions where westerly and northwesterly circulations prevailed during the wet season. A lower spatial coherency was observed with the dry season precipitation. The contribution of atmospheric moisture advection to precipitation variability diminishes in summer, whereas that of local land surface processes increases. Some regional teleconnection patterns, such as the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO), also contributed to the annual variability in precipitation.

Preparation and Characterization of NPK Nutrient Loaded Electrospun Cellulose Acetate Nanofiber Mat to be used as a Slow-release Fertilizer


 
 
 A major unsolved issue with chemical fertilizers is the low nutrient use efficiency. It has been reported that an excessive amount of up to 70% of the nitrogen applied to plants with traditional fertilizers is lost to the surrounding. Hence, the drastic pollution effects of chemical fertilizer usage. Slow-release fertilizers aim to reduce such losses via slow and sustained release of nutrients to the plant. In this study, we report the successful fabrication and characterization of a novel and biodegradable cellulose acetate (CA) electrospun nanofiber (NF) mat loaded with nitrogen, phosphorus and potassium plant nutrients of urea, hydroxyapatite nanoparticles (HANPs) and MOP respectively to be used as a slow-release fertilizer (SRF). It was envisaged that the unique properties of the electrospun NFs could overcome the shortcomings of traditional slow-release fertilizers (SRFs). The fabrication of the NFs was done with 8.5% w/v CA polymer dissolved in a 6 mL solvent system of acetone to dimethylformamide in a 2:1 volume ratio along with the addition of the aforementioned nutrients at 10% of the polymer weight. Electrospinning parameters were set after parameter optimization. The high-voltage supply was set at 16 kV, the spinneret to collector distance was 13cm and the flow rate was 1.5 ml/h. The solutions were electrospun only when the relative humidity was approximately between 65 to 70%. The HANPs incorporated were synthesized by the wet chemical precipitation method. The successful synthesis of the HANPs was confirmed via Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffraction (PXRD) analysis. The successful loading of the nutrients onto the electrospun NF mat was evident from FTIR, Raman and EDX analysis. Furthermore, the scanning electron microscopy images of the nutrient loaded NFs depicted a reduced average diameter with respect to those of the neat NF mat. The total nitrogen percentage of the nutrient loaded NF mat was determined to be 2.60% from Kjeldahl analysis. The initial nutrient release studies in water depicted a biphasic release model for orthophosphate and potassium nutrients while only a burst release profile was observed for nitrogen. It can be concluded that the electrospun NF mats display a potential application with regards to SRFs. However, several modifications to the NF mat fabrication such as the usage of coaxial electrospinning will have to be made in order to better optimize the nutrient loading and enhance its slow-release properties.
 Keywords: Electrospinning, Nanofiber mat, Slow-release, Hydroxyapatite nanoparticles