Ammonia volatilization from urea and ammoniacal fertilizers surface applied to winter wheat and grassland

Ammonia volatilization from urea, diammonium phosphate, ammonium sulphate and calcium ammonium nitrate surface applied to winter wheat and grassland was determined with windtunnels. The fertilizers were applied at a rate of 8–12 g N m^–2 to plots on a non-calcareous sandy loam. Five experiments were carried out during March to June 1992, each experiment including 2 to 4 treatments with two or three replications. The daily ammonia loss rate was measured during 15 to 20 days. Cumulated daily loss of ammonia from urea followed a sigmoidal expression, while the cumulated ammonia loss from diammonium phosphate showed a logarithmic relationship with time from application. For ammonium sulphate and calcium ammonium nitrate no significant loss could be determined, because daily loss of ammonia were at the detection limit of the wind tunnels. Mean cumulated ammonia loss from plots receiving urea, diammonium phosphate, ammonium sulphate and calcium ammonium nitrate were 25%, 14%, <5% and <2%, respectively, during a 15–20 day measuring period.     

Ammonia losses from ammonium-containing and -forming fertilizers after surface application at different rates on alkaline soils

The objective of this investigation was to compare the susceptibility of different ammonium containing and forming fertilizers to NH₃ losses and to determine the effect of application rates on NH₃ volatilization. Losses of NH₃ from five fertilizers, namely (NH₄)₂SO₄, CAN, urea, MAP and DAP were determined. The fertilizers were surface-applied to a sandy clay loam Arniston soil and a clayey Gelykvlakte soil of which the pH values were respectively 9.0 and 8.9. The application levels were equivalent to 0, 15, 30, 60, 120 and 240 kg N ha^–1. After a contact period of 3 days NH₃ losses were determined. Ammonia was lost from both soils under all treatments. More NH₃ was lost from the clayey Gelykvlakte soil compared with the sandy clay loam Arniston soil. Loss of NH₃ from the various fertilizers was ranked as follows: Urea > DAP > (NH₄)₂SO₄ > MAP > CAN. Ammonia losses increased with increasing application rates, but the proportion of N lost, decreased. Losses of NH₃ may be reduced by selective choice of fertilizer type and application rate.     

Ammonia volatilization from urea nitricphosphate and urea applied to the soil surface

Urea nitricphosphate (UNP) is an N-P fertilizer prepared by solubilizing phosphate ore with nitric acid and conditioning the product with urea. The product is acidic, and its nutrient analysis is 23-12-0. Urea makes up 74% of the N component of this material and the remainder comes from the nitrate added as nitric acid. In volatilization trials, UNP lost significantly less N than did urea in a noncalcareous soil (13 and 31% respectively). In calcareous soils the urea-N component of UNP exhibited loss patterns similar to those of urea. Soil pH remained stable at the center of the granule placement site during UNP hydrolysis, thereby reducing NH₃ loss, whereas the pH of the same soil treated with urea rose almost 1.9 units. The urea component of UNP appeared to diffuse from the center of the acidic microsite allowing hydrolysis to take place and permitting limited NH₃ volatilization to occur. UNP appears to be an attractive NP fertilizer in terms of nutrient analysis and resistance of the N component to volatile N losses as NH₃.     

普钙厂技术改造的可靠途径

针以协内钙及钙磷磷肥生产企业技术水平和经济效益不高的现状,从化肥发展趋势产品结构高速满足农业所需、提高效益出发,上海化工研究院研究开发了多项适合现有化肥生产厂进行技术改造的成套技术,并在生产厂推广应用。这些具有投资省、工艺先进、效益佳、无三废污染等特点,有些成果已达到国际先进水平。     

Relative ammonia loss from urea-based fertilizers applied to rice under different hydrological situations

Relative ammonia volatilization loss from prilled urea, urea supergranule (USG), neem cake-coated urea (NCU), rock phosphate-coated urea (RPCU), gypsum-coated urea (GCU), and prilled urea supplemented with dhaincha (Sesbania aculeata) green manure (Dh + PU) was measured in the fields under different hydrological situations of rice growing. Ammoniacal-N and pH of flood water were less with point placement of USG and Dh + PU treatments than with single basal broadcast applications of urea-based fertilizers. Ammonia collected with an acid trap in an enclosed chamber ranged from 1.47–3.07, 0.24–3.74, 0.80–3.50 and 0.50–1.20% of the applied N in upland, alternate wetting and drying, shallow submergence and intermediate deep water situations, respectively. The collected ammonia was less with point placement of USG at 5 cm depth in all situations and with Dh + PU treatment in shallow submergence than with other sources of N. Single basal broadcast applications of RPCU or NCU resulted in relatively higher loss. The loss from top-dressed urea was less than that from basally applied urea because of larger crop canopy at later stages of crop growth.     

Ammonia volatilization losses from fertilizers applied to acid soil in the field

Losses of ammonia by volatilization from ammonium sulphate and urea applied to soil were studied in field conditions.Losses from ammonium sulphate generally were not large; ammonia volatilization is thus unlikely to be an important pathway of nitrogen loss from cropped soils, and does not explain the low responses to nitrogen fertilizer of wheat grown in the higher rainfall cropping areas of South-Eastern Australia.Losses of nitrogen from ammonium sulphate were not greatly affected by meteorological variables, rate of application, water applicaton or incorporation into soil.The above variables all affected losses of nitrogen from urea, by influencing the rates of solution and hydrolysis of urea, and volatilization of ammonia. Losses ranged from 4 to 50% of the applied urea-nitrogen. Losses of urea-nitrogen were large when evaporation rates were high, and large variations occurred in the rates at which urea could be hydrolyzed.Extrapolation of the results to grazing conditions suggests that ammonia volatilization may result in large losses of nitrogen from short pastures in dry conditions.     

A comparative study of urea hydrolysis rate and ammonia volatilization from urea and urea calcium nitrate

A comparing of urea hydrolysis and NH₃ volatilization from urea supergranules and urea calcium nitrate (UCN, a new fertilizer produced by Norsk Hydro A/S, Norway) was made on two different flooded soil types, a high-CEC clay loam (Ås) and an intermediate-CEC clay loam (Kinn).Nitrogen loss by ammonia volatilization was reduced from 17% by surface application of urea supergranules (USG) on flooded Ås soil to 3% and 6% by UCN briquettes at either the same urea or nitrogen concentration as USG. A significant reduction was even found with the surface application of prilled UCN, 12% and 18% N-loss for prilled UCN and urea, respectively. The floodwater pH and NH ₄ ⁺ content was lower with UCN than urea, which reduced the potential for ammonia volatilization.NH₃-loss (5%) was significantly less when USG was surface applied on Kinn soil, while NH₃-loss from UCN briquettes was independent of soil type. The reduction in NH₃-loss from USG on Kinn soil was due to a decrease in the pH and NH ₄ ⁺ content of the floodwater caused by a reduced rate of urea hydrolysis.The rate of urea hydrolysis was lower with UCN than USG in both soils, but the difference between UCN and USG was greater in the Ås soil than in the Kinn soil. Three days after deep placement (10 cm), 18% of UCN urea and 52% of USG urea were hydrolyzed in Ås soil, while only 12% UCN and 17% USG were hydrolyzed in the Kinn soil.The surface application of USG on flooded soil reduced the rate of urea hydrolysis as compared to deep placement. 30% and 17% of USG urea was hydrolyzed after four days on Ås and Kinn soil, respectively. During the first few days the rate of hydrolysis of UCN was more affected by the soil type than the application method. Four days after surface application 32% and 13% UCN urea was hydrolyzed on Ås and Kinn soil, respectively. The rate of urea hydrolysis exhibited a zero-order reaction when USG and UCN-briquettes were point placed in flooded soils.     

Ammonia losses from surface-applied urea as related to urea application rates,plant residue and calcium chloride addition

Volatile losses of NH₃ from surface-applied urea are known to decrease in the presence of soluble Ca-salts or with a decrease in easily decomposable organic matter content (EDOM), both of which influence urease activity. How these factors interact to affect NH₃ losses is not fully understood. Studies were conducted to determine the effect CaCl₂ in sand with varying rates of EDOM on NH₃ losses from surface applied urea. The same effects were examined on agricultural soils containing partially decomposed native organic matter (NOM). Determinations were made in the laboratory on field soils, sand free of organic matter and sand with known amounts of grass clippings (GC, EDOM). Low levels of GC in sand with low amounts of added urea resulted in little NH₃ loss. Ammonia loss increased as more N was applied at the low levels of GC. The loss was independent of urea application rates at high levels of GC. Ammonia losses were reduced more effectively at low EDOM and NOM in the presence of Ca. Incubation of sand with GC at low rates prior to urea addition increased NH₃ losses relative to high levels of non-incubated GC. For the above situation incubation for as high as 24 days resulted in equivalent NH₃ losses. The amount and state of decomposition of existing organic matter affected the degree of NH₃ loss from surface placed urea and its control by added Ca-salts. Microbial decomposition of EDOM, such as might occur in the spring prior to urea addition, led to greater NH₃ losses. Greater loss of NH₃ from urea might be an indication of a larger ureolytic microbial population leading to increased urease production.     

Leaching loss of calcium,magnesium, potassium and nitrate derived from soil,lime and fertilizers as influenced by urea applied to undisturbed lysimeters in south-east Nigeria

Calcium hydroxide was applied to monolith lysimeters at Onne in south-east Nigeria. Eight lysimeters were cropped with maize followed by upland rice and four were uncropped. The cropped and two uncropped lysimeters received Mg, K and urea in the first season. Two uncropped lysimeters received no fertilizers. Drainage water was collected during the two growing seasons and analyzed for calcium, magnesium, potassium, sodium, nitrate and chloride. The fertilizer applied in the second season was not leached during the year of application.The cropped lysimeters lost 27 percent of the sum of the exchangeable Ca in the soil profile and the calcium added, and 29 percent of the corresponding sum for Mg. With no crop, the losses increased to 34 and 37 percent, respectively, but with no crop or fertilizer, the losses were similar to those from the cropped lysimeters. The loss of potassium ranged from 6 percent from the unfertilized lysimeters to 10 percent in the cropped lysimeters. The amounts of sodium leached ranged from 29 to 35 kg Na ha^–1. The bulk of the calcium and magnesium leached from calcium hydroxide and fertilizers occurred in the second season when the loss was in good agreement with the amount of nitrate lost giving (Ca + Mg)/NO₃ charge ratios of approximately one. Urea increased the amount of nitrate leached and led to a corresponding increase in the amounts of calcium and magnesium lost in the drainage water. The charge ratio remained unchanged when the cations were leached only with nitrate derived from the mineralization of soil organic matter. In the cropped lysimeters, this source accounted for about four times more nitrate in the drainage water than the fertilizer.     

Ammonia volatilization from point-placed urea in upland,sandy soils

The upland fertilization practice in Africa of placing N fertilizer below the soil surface near the plant might be facilitated through use of urea supergranules (USG). Since little is known about N losses from point-placed urea on light-textured African soils, laboratory studies were conducted in a forced-draft system to determine (a) the influence of soil properties on ammonia loss from USG and (b) to compare N loss from USG with that from broadcast N sources. Ammonia loss from 1.1 g USG placed at a 4-cm soil depth ranged from 2.9 to 62% of the added N on six light-textured soils. Ammonia loss was correlated with soil clay content (r = –0.93^**) but not with pH. A more detailed study on a soil from Niger revealed significantly less ammonia loss from either surfaced applied urea (18%) or surface-applied calcium ammonium nitrate (7%) than from USG placed at a 4-cm depth (67%). Amendment of surface-applied urea with 1.7% phenyl phosphorodiamidate (PPD), a urease inhibitor, essentially eliminated ammonia loss (1.9%). An¹⁵N balance confirmed that ammonia volatilization was the major loss mechanism for all N sources. The results suggest that point-placed urea may be prone to ammonia volatilization loss on light-textured African soils moistened by frequent light rainfall. In such cases, broadcast application of urea, CAN, or urea amended with PPD may be less prone to N loss.     

Factors controlling ammonia loss from trash covered sugarcane fields fertilized with urea

Ammonia losses following surface applications of urea to trash covered sugar cane fields were investigated in four climatic zones of tropical Queensland. Volatilization of ammonia and evaporation of water were determined by micrometeorological techniques. The results showed that the pattern, rate and extent of ammonia loss were controlled by the availability of water in the trash and its evaporation. Water added by dewfall, rainfall or condensation of evaporated soil moisture dissolved some of the urea and allowed it to be hydrolyzed to ammonia by the urease enzyme in the sugarcane residues; when the water evaporated, ammonia was lost to the atmosphere.In the dry climatic zone, where no rain or dew fell, water addition to the trash by condensation of evaporated soil moisture was not sufficient to dissolve much urea so very little ammonia was lost. In the cool and warm moist zones, small additions of water to the trash from dew, light rain and condensation maintained a slow but steady pattern of ammonia loss over a period of six weeks and resulted in losses of 32% and 39% of the applied nitrogen. At the site in the wet zone, heavy rainfall apparently washed the urea from the trash layer into the soil and limited ammonia loss to 17% of the applied nitrogen.Substitution of ammonium sulfate for urea reduced ammonia loss to less than 1.8% of the applied nitrogen.     

Ammonia volatilization losses from different fertilizers and effect of several urease inhibitors,CaCl2 and phosphogypsum on losses from urea

The extent of ammonia volatilization losses from urea, ammonium sulphate (AS), and diammonium phosphate (DAP) were determined in soil incubation studies. The effects of some urease inhibitors (thiourea, hyroquinone, 2–4 dinitro phenol and boric acid) and CaCl₂ and phosphogypsum additions on ammonia loss from urea were also studied. Total ammonia volatilization losses were 32.6%, 3.1% and 2.3% of the N applied to the soil as urea, AS and DAP, respectively. Among the chemicals examined in the study, 500 mg H₃BO₃ in 1 kg of the soil decreased the ammonia loss from urea by 21% in comparison with the control. When 50 mg/kg soil of thiourea, 2–4 dinitro phenol or hydroquinone were applied, ammonia volatilization losses were found to be 10%, 3% and 0% less than urea applied alone, respectively. When 2500 mg CaCl₂ was applied to 1 kg of soil with urea, ammonia loss was decreased by 5%. The lowest hydrolysis rate (65%) occurred with the boric acid treatment. The differences between the hydrolysis rates of the other treatments were not statistically significant. Phosphogypsum was found the most effective agent in reducing ammonia losses from urea. When phosphogypsum was mixed at 2.3 times as much as the urea, ammonia loss was about 85% less than that of urea applied alone. Obviously, further work is needed to find out the potential of both boric acid and phosphogypsum as reducing agents of ammonia losses from urea.     

Characteristics and so2 capture capacities of sorbents prepared from products of spray-drying flue gas desulfurization

The characteristics and the SO₂ capture capacities of sorbents prepared from products of spray-drying flue gas desulfurization (FGD) have been studied. Sorbents were prepared by first slurrying Ca(OH)₂ and CaSO₃ and/or CaSO₄ with and without the addition of fly ash and then drying. Compared to the use of pure Ca(OH)₂, the SO₂ capture and Ca(OH)₂ utilization decreased for sorbents prepared without fly ash and increased for sorbents with fly ash. Flakelike ill-crystallized tobermorites were observed for all the sorbents containing fly ash. In addition, significant amounts of needle-shape Ca₄Al₂(OH)₁₂SO₄ . 6H₂O and Ca₆Al₂ (OH)₁₂(SO₄)₃ . 26H₂O (ettringite) were also observed for the sorbents containing CaSO₃ and/or CaSO₄. These newly formed compounds dissociated into CaSO₃ . 0.5 H₂O and inert precursors upon sulfation, and were responsible for the high SO₂ capture capacities and Ca(OH)₂ utilizations of the sorbents prepared with fly ash.     

芒硝型卤水中盐硝组分对碱法脱除钙镁的影响

采用＂烧碱-纯碱＂法,对芒硝型卤水中Ca^2＋和Mg^2＋的脱除进行了研究,在常温、两碱用量为理论用量、反应时间为30 min和陈化时间为60 min的条件下详细考察了卤水中氯化钠和硫酸钠含量的变化对Ca2＋和Mg2＋脱除效果的影响。结果表明,硫酸钠组分对Ca2＋的脱除效果影响较大,当硫酸钠含量在30 g/L以下时,Ca2＋脱除率在90%以上,硫酸钠浓度增加有利于Mg2＋的脱除,但影响不大。氯化钠组分对Ca2＋、Mg2＋脱除效果的影响相对较小,氯化钠含量增加,Ca2＋脱除率明显增加,而Mg2＋脱除率略有下降。     

Optimization of amino acids production from waste fish entrails by hydrolysis in sub and supercritical water

A resource recovery technique using sub‐ and supercritical water hydrolysis was applied to convert waste fish entrails into amino acids. The effect of reaction parameters such as temperature and time necessary for the control of reaction towards optimum yield of amino acids was investigated. Results showed a maximum yield of total amino acids (137 mg/g dry fish) from waste fish entrails at T= 523 K (P = 4 MPa) and reaction time of 60 min in a batch reactor. Under supercritical conditions (e. g., T= 653 K, P = 45 MPa), the yield decreases due to rapid decomposition compared to production rate of amino acids. The results suggest operation of the system at short reaction time and mild temperature condition.     

煤矸石低温中和过程铁、钙、镁的溶出及动力学

立足于贵州盘州丰富的煤矸石资源,为探求其高值化开发利用途径,采用硫酸浸取法对煤矸石中铁、钙、镁的提取过程进行研究。研究结果表明：在中和反应过程中,随着温度的升高,铁、钙、镁的溶出逐渐增加,最后趋于平稳,温度对铁、镁溶出率的影响较为显著,对钙溶出的影响相对较小。因此,选择低温中和过程作为铁、钙、镁溶出动力学研究。动力学研究结果表明：煤矸石中和过程中铁、钙、镁溶出的活化能分别为19.523kJ/mol、8.300 kJ/mol和27.565 kJ/mol,E_a钙＜E_a铁＜E_a镁,说明在煤矸石硫酸浸出中和反应过程中钙的溶出最容易,铁次之,镁的溶出相对较难;浸出过程的动力学控制类型属于内扩散控制,可用动力学方程\mathrm{1}\text{-}\frac{\mathrm{2}}{\mathrm{3}}x\text{-}{\left(\mathrm{1}\text{-}x\right)}^{\frac{\mathrm{2}}{\mathrm{3}}}\text{=}kt来描述。通过对固相物质XRD、SEM的表征,初步对煤矸石中的碳酸盐酸浸溶出过程进行了机理分析,为工业生产中煤矸石的高效利用提供了技术指导和理论支撑。     

Effect of hydrolysis products and Mg2+, Mn2+ and Ca2+ ions on whey lactose hydrolysis and β‐galactosidase stability

BACKGROUND: Enzyme inhibition is one of the constraints of reactions catalysed by enzymes, and information is required on the inhibition mechanisms that affect the process yield. Therefore the aim of the present study was to investigate the effect of hydrolysis products and ions on the hydrolysis of lactose recovered from whey and enzyme inactivation during the reaction. The experiments were carried out in 250 mL of 25 mmol L^?1 phosphate buffer solution using β‐galactosidase from Kluyveromyces marxianus lactis in a batch reactor system. RESULTS : The degree of lactose hydrolysis (%) and the residual enzyme activity (%) in the presence and absence of lactose over time were investigated versus hydrolysate amount, glucose and galactose concentrations and Mg²⁺, Mn²⁺ and Ca²⁺ ion concentrations. The hydrolysis degree decreased with the addition of all hydrolysis products, as enzyme inhibition occurred. The residual enzyme activity increased with the addition of hydrolysate and glucose but decreased with the addition of galactose. It was observed that Mn²⁺ and Mg²⁺ ions activated the enzyme. It was also found that the hydrolysis degree was not affected by the addition of Mn²⁺ ions. On the other hand, the hydrolysis degree decreased with the addition of Ca²⁺ ions, as the enzyme was inactivated. CONCLUSION: Evaluation of the experimental data showed that both β‐galactosidase activity and lactose hydrolysis were affected by the addition of hydrolysis products and ions. Moreover, mathematical models proposed to predict the residual lactose concentration and residual enzyme activity were confirmed by the experimental results. Copyright © 2008 Society of Chemical Industry     

玉米秸秆衍生碳基固体酸的制备及其催化纤维素水解糖化

以玉米秸秆为原料,通过碳化-磺化法制备了碳基固体酸（CSA）,采用XRD、FTIR、XPS、SEM、阳离子交换与返滴定法等手段对其结构形貌进行表征,并考察了制备条件对固体酸表面活性基团含量与催化活性的影响。以NaOH/尿素冻融预处理后的纤维素为底物,研究了CSA催化纤维素水解糖化的效果与条件。结果表明：NaOH/尿素冻融预处理能够有效辅助固体酸催化纤维素水解,在350℃碳化2h、100℃磺化5h条件下制备的CSA催化性能最好,其酸量达3.94mmol/g,其中磺酸基、羧基、酚羟基含量分别为1.09mmol/g、1.36mmol/g、1.49mmol/g。在m(CSA)∶m(纤维素)=3∶1、水解温度200℃、水解时间为0.5h的条件下,纤维素水解还原糖得率与转化率分别为47.1%和63%。CSA循环利用3次催化活性下降不大。本研究可为废弃生物质原料制备的固体酸催化纤维素水解转化利用提供科学参考。     

Stable suspension fertilizers from monoammonium phosphate

Research studies conducted at the Tennessee Valley Authority (TVA) have shown that the addition of fluoride ion can improve the physical properties of suspension fertilizers made from monoammonium phosphate (MAP) containing metallic impurities. In the past, compounds of high cost, such as ammonium fluoride or bifluoride, have been used as the source of fluorine. Because of the cost of these compounds, a study was carried out using fluorosilicic acid, which is a by-product of the phosphate fertilizer industry, as the fluorine source in the production of suspension fertilizers from MAP. In the study, three commercial MAPs of medium- to high-impurity levels were evaluated. The experimental data showed improvements in both viscosity and pourability of 10-30-0 (N-P₂O₅-K₂O) and 11-33-0 grade suspensions made from 11-52-0 grade MAPs using as little as 0.6% fluorine added as fluorosilicic acid. Products of grades 10-30-0 and 11-33-0 (fluorine added) had satisfactory storage at both 27 and 38°C for up to 90 days, while the control sample (no fluorine added) had satisfactory storage for only 30 days at 27°C and less than 15 days at 38°C.     

Immobilization of tannery industrial sludge in ceramic membrane preparation and hydrophobic surface modification for application in atrazine remediation from water

Chromium laden waste produced from tannery industry was immobilized in ceramic matrix for fabrication of the tubular single channel microfiltration membranes by extrusion. The presence of chromia resulted in substitutional solid solution formation with alumina and catalyzed mullite phase growth, hence increasing the mechanical and chemical stability of the membranes. The structural, morphological and water permeation characteristics of the membranes were studied to analyze their formation mechanism and effect of different parameters, viz. the sintering temperature, amount of waste added, presence of organics and extent of chromium immobilization. The surface of the macroporous membrane was hydrophobically modified, by polydimethylsiloxane (PDMS), producing contact angle of 141°. The process efficiency of the hydrophobic membrane was assessed in terms of the removal of atrazine, a contaminant of emerging concern, following the principle of hydrophobic interaction. Effect of different operating parameters affecting atrazine removal, viz. transmembrane pressure, cross flow velocity and filtration time was studied in cross flow filtration mode. High atrazine removal of >95% was obtained along with the maintenance of high flux during the filtration operation. The prepared cost-effective microfiltration membranes can thus be further modified for efficient water treatment applications.