Urea Nitrate Research Articles

Agronomic responses of diverse bread wheat genotypes to phosphorus levels and nitrogen forms in a semiarid environment

Increasing wheat production has become an urgent requirement to cope with rapid population growth and abrupt climate change. The management of phosphorus (P) and nitrogen (N) is one of the most important factors for sustaining and increasing wheat production, particularly in semiarid environments. This 2-year field study, which aimed to investigate the effect of P levels (0, 35, and 70 kg P2O5 ha−1) and N forms (urea, ammonium sulfate, and ammonium nitrate) on the yield attributes of three diverse high-yielding commercial wheat cultivars (‘Shandawel-1’, ‘Sids-14’, and ‘Sakha-95’), was carried out at Om-Elzain Village, Zagazig, Egypt. The results indicated that increasing P levels was accompanied by a substantial increase in all evaluated traits, except spike length, and that high P level (70 kg P2O5 ha−1) was superior. Considerable genetic variation was detected among the evaluated cultivars for all studied traits. Cultivar ‘Sakha-95’, followed by ‘Sids-14’, presented the most vigorous growth and enhancements in most yield components, grain yield, and biological yield. Furthermore, ‘Sakha-95’ recorded the highest agronomic P use efficiency, followed by cultivar ‘Sids-14’. N forms did not significantly affect all of the tested traits except plant height, spike number m−2, and 1000-grain weight, during both seasons. Ammonium-containing fertilizer (ammonium sulfate and ammonium nitrate) resulted in the highest values for these traits when compared with urea. Accordingly, ‘Sakha-95’ and ‘Sids-14’ are recommended for commercial use under high P levels. N forms had a marginally substantial effect on grain yield and its attributes.

Performance of conventional and enhanced-efficiency nitrogen fertilizers on potato tuber mineral composition and marketability.

Potato is an essential crop for global food security, and its cultivation requires a significant amount of readily available nitrogen (N) to ensure tuber quality. Therefore, managing N with enhanced-efficiency fertilizers becomes a potential strategy to meet the seasonal potato N demand. A 3 site-years (SYs) study was conducted to assess the marketable attributes and mineral composition of table-stock potato in response to N rates and fertilizers urea, ammonium sulfate and ammonium sulfate nitrate (ASN) with nitrification inhibitor dimethylpyrazole phosphate (DMPP). At 75% of recommended N rate (RNR), ammonium sulfate and ASN+DMPP ensured marketable tuber yields equivalent to that observed at 100% of RNR. Urea promoted greater tuber K and Mg concentrations than ammonium sulfate and ASN+DMPP. Although inconsistent across SYs, ASN+DMPP generally reduced starch and reducing sugars contents and increased pulp pH and protein content than other fertilizers. Increasing N rates from 50% up to 75% and 100% of RNR increased marketable tuber yields and protein content, whereas soluble solids increased from 50% to 100% of RNR. Conversely, increasing N rates from zero to 75% of RNR reduced tuber firmness, whereas N application reduced tuber P concentration, regardless of N rates. Although ASN+DMPP showed potential for increasing marketable tuber yield and protein content, potatoes receiving ammonium sulfate and ASN+DMPP lowered tuber K and Mg concentrations compared to those receiving urea. Overall, potato tuber quality improvements are N source-specific, demanding strategies under which these fertilizers can ensure/improve tuber nutritional composition along with size quality. © 2021 Society of Chemical Industry.

Evaluation of Soil S Pools under 23 Years of Maize Monoculture

Sulfur nutrition is a critical part of proper crop growth and development. In our study, biomass yields (BY) and S uptake were investigated on long-term maize monoculture on haplic luvisol soil during the 23 years of this trial, as well as changes in water extractable (Sw), adsorbed (Sads), mineral (Sav), and pseudo-total S (St) fractions. Treatments used in this study are: (1) Control (Cont); (2) ammonium sulfate (AS); (3) urea and ammonium nitrate (UAN); (4) UAN + phosphorus and potassium (UAN + PK); (5) UAN + phosphorus, magnesium, sulfur (UAN + PMgS); and (6) Fallow. Recently, the Mehlich 3 method started to be used in the Czech Republic to determine content of plant available S. Using this method, it was found that the content of S extracted by Mehlich 3 (SM3) closely correlates to Sav in both topsoil and subsoil (r = 0.958 in 1997 and 0.990 in 2019, both at p < 0.001). We also found that, on average, during the entire experiment, all treatments had increased yields over Cont (135–147%) and increased S uptake (291, 192, 180, and 246% of Cont for AS, UAN, UAN + PK, and UAN + PMgS, respectively). Examining the changes from 1997 to 2019 in topsoil (0–30 cm depth), we discovered a decrease of S content in Sw, Sads, Sav, and St fractions on all treatments to an average of 34.6%, 65.8%, 42.2%, and 78.6% of their initial values. The exception was AS treatment, which doubled its initial content in mineral fractions and maintained the same levels of St, and which we attribute to the very high dose of S on this treatment (142 kg ha−1 year−1). Using the simple balance method, AS and UAN + PMgS treatments lost 142.2 and 95.3 kg S ha−1 year−1 to other sinks, except plant uptake, from the entire soil profile (0–60 cm) during 23 years of experiment. Other treatments also show significant losses with the exception of Fallow. Given these results, it is clear that content of sulfur in soil is generally decreasing and attention should be paid mainly towards minimizing of its losses.

Analysis of the conduction mechanisms of the Ni doped apatite‐type lanthanum silicate electrolyte ceramics synthesized by the combustion method

AbstractIn this study, the nickel doped apatite‐type lanthanum silicate La9.33Si6‐xNixO26‐x (x = 0, .5, 1.0, 1.5, 2.0) (LSNO) electrolyte powders were successfully generated by using the urea nitrate combustion method at 600°C and 6–8 min. The optimal sintering temperature was determined to be 1500°C on the basis of the linear shrinkage, relative density as a function of temperature, and microcosmic analysis. It was observed that Ni2+ successfully replaced Si4+ in [SiO4] to form the [Si(Ni)O4] tetrahedra. LSNO had a typical p63/m apatite structure of high purity. A significant change in the cell volume of the doped samples was observed, and the cell volume increased with the doped nickel content. The conductivity reached the peak value at x = 1.0 (1.21 × 10−3 S·cm−1, 700°C). Nickel doping introduced the oxygen vacancies and expanded the channels for interstitial oxygen conduction. Further, it also directly reduced the amount of interstitial oxygen in the LSO structure. This led to an enhancement in the conductivity of La9.33Si6‐xNixO26‐x, followed by a decrease on increasing the doped nickel content. The conductivity enhancement in the Ni‐doped LSO resulted from the combination of two mechanisms, namely, the oxygen vacancy defect and lattice volume enhancement mechanism.

CeO2 quantum dots anchored g-C3N4: synthesis, characterization and photocatalytic performance

Cerium dioxide quantum dots (CeO2QDs) modified graphitic carbon nitride (g-C3N4) was fabricated by a facile chemical reaction with urea and cerium nitrate hexahydrate as precursors. Combined X-ray diffraction (XRD), UV–Vis DRS, transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), Electrochemical impedance spectra (EIS), Thermogravimetric analysis (TGA), Brunner-Emmet-Teller (BET) measurements and X-ray photoelectron spectroscopy (XPS) studies showing that CeO2QDs dispersed homogeneously on the g-C3N4 surface, which enhanced the absorption in visible light region. Specifically, we found that CeO2QDs/g-C3N4 shows much lower electron-hole recombination rate, and its Rhodamine B photodegradation rate constant can reach 0.00985 min−1, which is 7 times higher than that of single g-C3N4. In addition, the CeO2QDs/g-C3N4 displayed outstanding catalytic stability. Furthermore, the CeO2QDs/g-C3N4 catalyst also exhibited the excellent photodegradation performance on other substrates such as TC, Methyl Orange, and Methyl Blue. It was proposed that the CeO2QDs/g-C3N4 photocatalyst could follow a more appropriate Z-scheme charge transfer mechanism. Our studies extend the application of Quantum dots nanocomposite catalyst and pave the way for its further rational design.

Pigment production by Scenedesmus dimorphus using different low‐cost and alternative culture media

AbstractBACKGROUNDThis study investigated the feasibility of producing pigments from Scenedesmus dimorphus using different low‐cost synthetic and alternative media. Thus the influence of nitrogen and phosphorus deficiency, different nitrogen sources and alternative culture media (wheat bran, garlic powder, wheat bran supplemented with garlic powder) on pigment and biomass production was evaluated.RESULTSAmong the three sources of nitrogen studied (ammonium sulfate, urea and sodium nitrate), urea was the cheapest efficient alternative source of nitrogen for pigment production, especially total chlorophylls (67.38 μg L−1 d−1), by this strain, without strongly affecting biomass yield. Phosphorus deficiency had no negative effect on biomass production, but improved the production of zeaxanthin and chlorophyll b by13.1% and 26.8%, respectively, compared to control. Compared to BG‐11 medium, the alternative garlic powder medium increased the biomass yield of S. dimorphus by 5.2 times, improved the productivity of xanthophylls and contributed to the accumulation of β‐carotene.Wheat bran medium was found to be efficient as a zero‐cost culture medium for the production of pigments, where S. dimorphus accumulated twice the total pigment concentration of the control, with high β‐carotene productivity (38.58 ± 11.94 μg L−1 d−1). The addition of garlic powder to wheat bran increased the biomass (3.14 g L−1) and pigment productivity (216.86 ± 2.06 μg L−1 d−1) by 28.5 and 1.4 times, respectively, but inhibited zeaxanthin biosynthesis. This alternative medium reduced biomass and pigment production costs by 99.80% and 96.21%, respectively.CONCLUSIONWheat bran supplemented with garlic powder showed good application potential for the industrial production of biomass and pigments from S. dimorphus in open cultivation systems where garlic powder might be used simultaneously for biomass and pigment accumulation, and for biological contamination control. © 2021 Society of Chemical Industry (SCI).

Synthesis and characterisation of homemade urea nitrate explosive from commercial sources of urea

The aim of this study was to investigate the preparation of urea nitrate (UN) using a range of urea sources followed by characterisationwithanalytical techniques routine to explosive analysis. The UN was prepared from lab grade urea, fertiliser urea, urea cold packs, diesel exhaust fluid (DEF) and Osmocote plant feed, resultingin six samples of UN as the Osmocote plant feed produced a blue and yellow product due to variation between products purchased at different times. Infrared and Raman spectroscopy revealed no notable differences between the samples apart from the blue UN product, which hada distinct peak in the IR spectra at 1150 cm−1. The Osmocote products couldbe discriminated by scanning electron microscopy energy-dispersive x-ray spectroscopy (SEM-EDS) and ion chromatography (IC), as bulk samples contained a range of trace metals and ions. Analysis by inductively coupled plasma mass spectrometry (ICP-MS)found 9 elementspresent at varying concentrations throughout the samples. The Osmocote products could be identified by the concentration of manganese, copper, and molybdenum whiletheDEF product could be discriminatedas it contained a high concentration of nickel compared to other samples. ICP-MS has potential to further discriminate between the lab grade, fertiliser and cold pack samples, however, additional statistical and chemometric analysis is necessary. This study highlights that seized UN can be identified as being prepared from DEF or an Osmocote product, and contributes to the forensic intelligence of improvised explosives by reporting how UN can be commercially sourced, prepared and characterised.

Efecto de las diferentes fuentes de nitrógeno en la producción de metano, amonio libre y ácido sulfhídrico en la digestión anaeróbica del lactosuero con estiércol de vaca

In this present study, the effect of different nitrogen sources in the anaerobic digestion of cheese whey on methane production, free ammonia, and hydrogen sulfide. The results showed that supplementation with urea at a concentration of 1000 mg L-1 the maximum methane production values of 513.95 ± 2.12 mL CH4 g VS-1 were obtained. On the other hand, supplementation with ammonium nitrate at a concentration of 1000 mg L-1 gave a value of methane of 415.93 ± 5.44 mL CH4 g VS-1 and exhibited the lowest values hydrogen sulfide of 267.69 ± 0.37 ppm and free ammonium of 49.18 ± 9.66 mg L-1. Supplementation with ammonium sulfate at a concentration of 2000 mg L-1, methane values of 466.64 ± 9.93 mL CH4 g VS-1 and hydrogen sulfide of 2768.43 ± 20.52 ppm were obtained. The findings from this research contributed to elucidate the role of supplementation with urea, ammonium sulfate, and ammonium nitrate in the anaerobic digestion process, which could help to solve some problems related to the reduction of methane production in cheese whey fed biodigesters.

Impact of Nitrogen Levels and Planting Density on the Growth and Yield of Okra (Abelmoschus esculentus L. Moench)

The study was carried out to the effects of different plant densities and nitrogen levels on okra yield and plant development. Field trials were conducted in two locations, the training fields of the Ege University, Ödemiş Research and Training area, and Ege University Faculty of Agriculture, Menemen Research and Training Farm. The field layout was a split-plot design with 3 replicates, where main plots consisted of nitrogen applications and sub-plots of plant densities. Fertilizer was applied in the form of Triple Superphosphate, Potassium Sulfate, Urea and Ammonium Nitrate. Five different nitrogen levels (F1: 0, F2: 40, F3: 80; F4: 120 and F5: 160 kg N ha-1) and two different rows spacing (PD1: 15 cm×70 cm and PD2: 25 cm×70 cm) have been tested. Yield and yield components, plant height at flowering, height of the first fruits, the number of leaves, the number of branches, the number of days from sowing to first flowering, the number of days from sowing to first harvest, plant height, foliation status, total yield, yield of plant, average fruit weight, fruit length, fruit diameter have been noted in the field experiments. Total yield ranged from 5923.8 to 12888.9 kg ha-1 at the Ödemiş location, while it was 3363.3-5009.2 kg ha-1 at the Menemen location. In conclusion, the highest yield is taken from F2 in both plant densities in Ödemiş. In Menemen, the highest yield is taken from the dose of F3 (80 kg Nha-1) and F4 (120 kg Nha-1).

Long-term assessment of the thermal stability of sodium nitrate-urea eutectic phase change material

The eutectic mixture formed by urea and sodium nitrate can be an interesting candidate for use as a phase change material for thermal energy storage in space heating and domestic hot water applications. It shows a melting point of 85 °C, a melting enthalpy of 172 J/g and a price around 0.9 €/kg. However, the thermal stability of the mixture is a great concern for this application. A preliminary evaluation of the thermal stability was performed and previously reported by the authors. It consisted of an accelerated thermal cycling test with 210 thermal cycles and the material showed a stable behavior. Nevertheless, the long-term stability of urea in the liquid state at temperatures below 100 °C is uncertain and requires a specific study. The main objective of the present work is to evaluate the long-term thermal stability of the mixture when it is exposed to long periods of use under conditions representative of actual applications, by means of analyzing the thermal and compositional behavior of samples remaining at 100 °C for several periods up to one year. A methodology is proposed, which intends to isolate the thermal degradation phenomenon from others, such as phase segregation, supercooling, and polymorphism, that can be introduced by thermal-cycling. It also aims to be more representative of the actual application than the accelerated thermal cycling approach. • Long-term degradation study of the urea-sodium nitrate eutectic mixture as a phase change material. • Experimental tests representative of actual use conditions. • Urea mainly degrades to biuret and cyanuric acid. • Degradation levels stabilize after an initial significant decrease. • Tightness is a key parameter and greatly influences degradation.

Phase Equilibria in the Sections of the Ca(NO3)2–CO(NH2)2–H2O System and Deicing Properties of Nitrate–Urea Mixtures

Phase Equilibria in the Sections of the Ca(NO3)2–CO(NH2)2–H2O System and Deicing Properties of Nitrate–Urea Mixtures

Thermochemical degradation of cotton fabric under mild conditions

Textile waste presents a major burden on the environment, contributing to climate change and chemical pollution as toxic dyes and finishing chemicals enter the environment through landfill leachate. Moreover, the majority of textile waste reaching landfills is discarded clothing, which could be reused or recycled. Here we investigate environmentally benign morphology changing of cotton textiles as a precursor for reintegration into a circular materials economy. At 50 °C using low concentrations of acids and bases, the interfiber structures of woven cotton were successfully degraded when treated with the following sequence of chemical treatment: citric acid, urea, sodium hydroxide, ammonium hydroxide, and sodium nitrate. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) reveal separation of the constituent fibers without depolymerization of the cellulose structure, and streaming potential measurements indicate that surface charge effects play a key role in facilitating degradation. The proposed reaction procedures show feasibility of effective waste-fabric recycling processes without chemically intensive processes, in which staple fibers are recovered and can be re-spun into new textiles.

Nitrogen sources affected the biosynthesis of 2-acetyl-1-pyrroline, cooked rice elongation and amylose content in rice.

Many studies have been carried out on N sources effect on fragrant rice; however, their impact on rice grain quality is largely unclear. In this study, we evaluated the effects of different types of N sources on rice growth, yield, 2-acetyl-1-pyrroline (2AP), amylose and cooked rice elongation. Two indica rice cultivars, Basmati 385 (B385), Xiangyaxiangzhan (XYXZ) and two japonica cultivars, Yunjingyou (YJY), Daohuaxiang (DHX) were grown in experimental pots with six replications under four N sources: Potassium nitrate (KNO3), ammonium bicarbonate (NH4HCO3), urea (H2NCONH2) and sodium nitrate (NaNO3) in 2019 and 2020 early seasons. Our results showed that N dynamics regulated the number of panicles, 1000-grain weight, grain yield, 2-acetyl-1-pyrroline, amylose and cooked rice elongation across all the four treatments. The NH4HCO3 treatment significantly increased the number of panicles and grain yield across the four rice varieties compared with KNO3, H2NCONH2 and NaNO3 N sources in both 2019 and 2020 early season, The KNO3 treatment significantly showed higher 1000-grain weight in B-385, YJY, XYXZ and DHX compared to other N sources. Compared with other N sources treatment, the NH4HCO3 treatments significantly increased the 2AP contents in heading stage leaves, matured leaves and grains of B-385, YJY, XYXZ and DHX respectively. Cooked rice elongation percentage also showed significant difference in all treatments studied with KNO3 recorded the highest across the four varieties. Analysis of major enzymes and compounds such as P5C, P5CS, PDH, Pyrroline, proline and Methylglyoxal showed remarkable differences in each cultivar at heading and maturity stages with higher activity in NH4HCO3 and H2NCONH2 treatments. Similarly, in all treatments, we also observed significant increase in amylose content percentage, with NH4HCO3 having greater percentage of amylose.

DMPP mitigates N2O emissions from nitrogen fertilizer applied with concentrated and standard vinasse

The application of vinasse, an organic byproduct of ethanol production, can enhance greenhouse gas emissions from N fertilizers, especially nitrous oxide (N2O). The objective of this work was to test the efficiency of the nitrification inhibitor (NI) 3,4 dimethylpyrazole phosphate (DMPP) in reducing N2O emissions from urea (UR) and ammonium nitrate (AN) applied with or without standard (V) or concentrated vinasse (CV). Two laboratory studies were conducted with repacked soil columns from a sugarcane field. Based on usual field rates, UR and AN were added at a rate equivalent to 100 kg N ha−1, V was added at 100 m3 ha−1 (51 kg N ha−1), and CV was added at 20 m3 ha−1 (Exp. 1: 35 kg N ha−1 and Exp. 2: 56 kg N ha−1). N2O emissions were measured for 75 and 61 days after the input of fertilizers and vinasses. When mineral fertilizers were compared, the N2O-N emission factors (EFs) were: 0.08% (AN) and 1.44% (UR). Combined with N fertilizers, vinasses (CV and V) greatly enhanced the N2O emissions from soil (ranging from 0.76% to 1.5% in one study and 1.37% to 6.27% in the other). In addition, CV + N fertilizer emitted more N2O than V + N fertilizer or N fertilizer alone. However, NI reduced N2O emissions by 80% on average for vinasses (CV and V) plus N fertilizer (AN and UR) and UR alone, but not for AN alone. Since both vinasses and mineral N fertilizers are standard inputs for sugarcane production and high N2O emissions are observed when they are applied in the same area, NI should be considered for mitigation of soil N2O emissions from sugarcane used for bioenergy.

Deflagration method synthesizing N, S co-doped oxygen-functionalized carbons as a bifunctional catalyst for oxygen reduction and oxygen evolution reaction

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the main reaction processes in metal-air batteries, fuel cells, and water electrolysis devices. It is of great significance to develop highly efficient and low-cost bifunctional catalysts for these two reactions. In this study a rapid deflagration method was reported by using Vulcan XC/72 carbon black, sublimated sulfur, potassium nitrate, urea and ammonium nitrate as raw materials to fast synthesize N and S co-doped and oxygen-functionalized carbon materials (D-NSOCs) in one step. The prepared D-NSOCs electrocatalyst exhibits excellent ORR and OER bifunctional catalytic reactivity with a small potential gap (ΔE) of 0.77 V between the corresponding potential when the OER current density reaches 10 mA cm−2 (Ej = 10) and the half-wave potential (E1/2), which is slightly better than 0.78 V for the commercial Pt/C + IrO2. This deflagration method is generally applicable to other carbon materials. It can dope nitrogen and sulfur elements into carbon materials and realize the functionalization of oxygen on the surface of carbon materials.

Dual role of activated carbon as fuel and template for solution combustion synthesis of porous zinc oxide powders

AbstractIn this work, nanosized zinc oxide (ZnO) powders were fabricated by urea–nitrate solution combustion synthesis using activated carbon as a structure‐directing template and secondary fuel at different fuel–oxidant ratios. The as‐synthesized powders were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption–desorption measurements, UV–Vis diffuse reflectance spectroscopy, and photoluminescence. The effect of fuel amount on photocatalytic activity of ZnO powders was evaluated by the degradation of an azo dye Orange G. It was observed that combustion synthesis with activated carbon as a secondary fuel had a profound effect on reducing crystallite size and enhancement of specific surface area. The crystallite size of the as‐synthesized powders varied from 46 to 26 nm. The ZnO powder prepared at a fuel–oxidant ratio of 1.8 possessed the small crystallite size and high specific surface area of 69 m2/g. It correspondingly resulted in the highest dye removal percentage of 99% with a rate constant of 0.027 min−1. The improvement in dye degradation can be due to the synergistic interaction and interplay of enhanced surface area and catalytic ability of the photocatalyst. This study provides a simple single‐step synthesis methodology to produce metal oxide nanopowders with tunable surface properties for high potential applications in catalysis, optoelectronics, and gas sensors.

DRY MATTER ACCUMULATION AND SUGAR AND ALCOHOL YIELD OF SUGARCANE SUBMITTED TO NITROGEN SOURCES AND DOSES

The study aimed to evaluate the nitrogen sources and doses application effects on the dry matter production and the sugar and alcohol gross yield of sugarcane (SP80-1816) in the cane-plant cycle in a dystrophic Red Oxisol. The experiment was conducted in the Fazenda Rio Paraiso II field, belonging to Usina Raízen, in Jataí - GO. The experimental design used was randomized blocks, arranged in a factorial scheme (2 x 4), with three replications. The treatments consisted of two nitrogen sources (urea and ammonium nitrate) and four nitrogen doses (0, 60, 120, and 180 kg ha-1). Dry matter variables were analyzed in sub-subdivided plots, as four evaluation periods were added (210, 250, 290, and 330 days after planting). The evaluation periods influenced sugarcane dry matter, and urea favored these variables to the ammonium nitrate's detriment. In contrast, the opposite occurred for stalk yield and sugar and alcohol yields, in which ammonium nitrate provided greater increments. The increase in nitrogen doses provided linear gains in practically all studied variables.

Fabrication of flexible, cost-effective, and scalable silver substrates for efficient surface enhanced Raman spectroscopy based trace detection

The fabrication and optimization of cost-effective, eco-friendly, uniform and flexible SERS platforms by facile synthesis routes has recently attracted great attention for trace detection of various analytes. Herein, we report the fabrication of interconnected Ag nanostructures on the unmodified filter paper-based flexible substrates by a facile recipe, which involves evaporation of Ag precursor solution on the filter paper followed by its reduction with a strong reducing agent, NaBH4. The fabrication process is time-efficient, reproducible, and has the potential of being scaled up. The presence of inter-connected nanostructures results in high concentration of uniformly distributed hotspots on the substrate, which in turn provide excellent and reproducible SERS sensitivity. The finite element simulation results showed that fabricated nanostructures are much more effective for field enhancement as compared to the agglomerated spherical nanoparticles. Crystal violet (CV) concentration of 10−8 M was easily detected with these substrates both via solution drying and swabbing. Similarly, AgFPS have proven effective for swab-based detection of urea nitrate (UN), a well-known constituent of homemade explosives. The C-N and NO3- symmetric stretching modes of UN are detectable down to 1 µM and 100 µM concentrations, respectively. Moreover, these substrates showed SERS signal uniformity both from different spots of a single substrate, and substrates from different batches, with spot-to-spot relative standard deviation (RSD) of 15% and sample-to-sample RSD of 15–19%. This makes them excellent for reliable and quick quantitative detection. The simple synthesis strategy, flexibility, cost-effectiveness, and quantitative detection makes these substrates ideal for SERS based trace detection, especially for on-site analysis, and various sensing applications.

Effect of urease/nitrification inhibitor on urea nitrogen conversion in black soil and cinnamon soil.

We studied the effects of urease/nitrification inhibitor combinations on urea hydrolysis and nitrification, aiming to screen out the effective inhibitor combinations for black soil and cinnamon soil in Northeast China. Urease inhibitor, N-butyl thiophosphate-triamine (NBPT), and its combination with nitrification inhibitor dicyandiamide (DCD), 3, 4-dimethylpyrazole phosphate (DMPP), 2-chloro-6 (trichloromethyl)-pyridine (CP), 2-amino-4-chloro-6-methylpyrimidine (AM) and 3-methylpyrazole (MP) were added to urea separately. Samples were collected 15 times in each of all the treatments during 125 days. We examined the changes of urea nitrogen, ammo-nium, nitrate, and nitrification inhibition rate in the two soils. Our results showed the hydrolysis of urea in black soil and cinnamon soil was about 7 d, and the addition of NBPT with or without diffe-rent nitrification inhibitors slowed down the hydrolysis to 21 d at least. Compared with the treatment with common urea, inhibitor addition significantly increased soil NH4+-N, decreased soil NO3--N, and maintained the high NH4+-N content in soil for a longer time. In black soil, application with nitrification inhibitor inhibited soil nitrification significantly and lasted for more than 125 d. DMPP and CP combined with NBPT increased the NH4+-N content in black soil by 1.6-1.8 times, while the nitrification inhibition rate was 47.9% and 24.1% at 125 d, respectively. In the cinnamon soil, the application of nitrification inhibitor could prolong the duration of ammonium oxidation from 80 d to 110 d. DCD and DMPP combined with NBPT increased the NH4+-N content in cinnamon soil by 2.1-3.4 times, while the nitrification inhibition rates at 125 d were 25.3% and 23.2%, respectively. Therefore, NBPT+DMPP combination with urea was recommended for utilization in black soil, followed by NBPT+CP. In cinnamon soil, NBPT+DCD combination with urea was recommended, followed by NBPT+DMPP.

Contrasting patterns of 2-methylisoborneol (MIB) vs. geosmin across depth in a drinking water reservoir are mediated by cyanobacteria and actinobacteria

Taste and odor episodes caused by off-flavor secondary metabolites, such as 2-methylisoborneol (MIB) and geosmin, pose one of the greatestchallenges for drinking water utilities around the world. The prevalence of these compounds is predicted to increase in the future as a function of nutrient enrichment and elevated temperatures of surface drinking water sources. We conducted a manipulative field experiment in a drinking water reservoir to elucidate patterns for two taste and odor compounds, MIB and geosmin, as well as two taxa known to produce these compounds, phytoplankton (more specifically, cyanobacteria) and actinobacteria, across different depths in response to nutrient enrichment with two common dissolved nitrogen forms, organic urea or inorganic nitrate. In general, we found that MIB levels increased by greater than 250% with nutrient enrichment mediated by increased phytoplankton biomass. However, the effect of the fertilization treatments on MIB decreased with depth with a 35% reduction at 7m versus 1.5 m. In contrast, geosmin levels reached a maximum at the lowest measured depth (7 m), were unaffected by the fertilization treatments, and followed a similar pattern to the abundance of actinobacteria. Thus, our data suggest that the positive response of phytoplankton (e.g., cyanobacteria, such as Oscillatoria species) to the fertilization treatments is likely responsible for increased MIB, while geosmin concentrations may be a function of actinobacteria-mediated decomposition in the hypolimnion in our study system.