Ammonia loss from surface applied urea-acid products

Ammonia (NH₃) losses from soils occur only under alkaline conditions; therefore, adequate acidification could prevent NH₃ loss. In acid soils this alkaline condition will exist only as a micro-environment around the decomposing CO(NH₂)₂ granule. The objective of this experiment was to examine the degree of NH₃ loss reduction that occurs when acids are placed with surface applied CO(NH₂)₂. Phosphoric acid, H₂SO₄, HCl and HNO₃ were used with surface applied CO(NH₂)₂ in a laboratory experiment to examine resultant NH₃ loss under very extreme NH₃ loss conditions. Calcium and magnesium chloride salts were added to urea:phosphoric acid to compare the relative effectiveness of acid and Ca + Mg salts for control of NH₃ loss.Little depression of NH₃-N loss was found from CO(NH₂)₂ containing H₃PO₄ and H₂SO₄ when the sand contained free CaCO₃. However, when CO(NH₂)₂:H₃PO₄ (UP) mixtures were applied as 17-19-0 on neutral and acid sands, NH₃ losses were reduced. Molar ratios less than 1:1 (28-12-0, 35-7-0) resulted in NH₃ losses similar to those from CO(NH₂)₂ alone even in acid soils. The 110 g N m^–2 as 17-19-0 reduced relative NH₃-N loss and pH in acidified and neutral soils more effectively than 11 g N m^–2. Ammonia losses are determined by chemical reactions occurring under the individual CO(NH₂)₂ granules; therefore, the use of the high 110 g N m^–2 rates in this research. The 17-19-0 reduced soil pH and retarded the rate of CO(NH₂)₂ hydrolysis with consequent reduction in NH₃ loss. Ammonia loss was reduced only slightly at 11 g N m^–2 from 17-19-0 even in acid soils. Ammonia loss was reduced from 70 to 30% of applied N by applications of HNO₃ and HCl with the CO(NH₂)₂. The HNO₃ and HCl react with CaCO₃ in a calcareous soil to produce CaCl₂ and Ca(NO₃)₂ which are known to reduce NH₃ loss from surface applied CO(NH₂)₂. However, a dry product of HNO₃ · CO(NH₂)₂ is explosive and can not be used as a general fertilizer.Calcium chloride or MgCl₂ combined with CO(NH₂)₂:H₃PO₄ reduced NH₃ loss more at 110 g N m^–2 than at 11 g N m^–2. Calcium chloride reduced NH₃ loss more effectively than MgCl₂. The CaCl₂ and MgCl₂ salts were more effective than H₂SO₄ or H₃PO₄ in reducing NH₃ losses except when (e.g., 17-19-0) mixtures were added to neutral or acidic sands.Contribution from Texas Agric. Exp. Stn., Texas A & M University, College Station, TX 77843.     

Effects of nitrogen source,rate and application time on boronia (Boronia megastigma Nees) leaf nitrogen and flower production

Nitrogen was supplied from two fast release sources, ammonium sulfate ((NH₄)₂SO₄) and calcium nitrate (Ca(NO₃)₂) and a slow release source, isobutylidene diurea (IBDU) to boronia, a new flower crop native to Australia. At lower rates (25 kg per ha), N availability from different sources, as indicated by the leaf N concentration, did not differ within a month after application but three months after application, N availability was higher from IBDU than from (NH₄)₂SO₄ or Ca(NO₃)₂. At 50 or 100 kg per ha, N availability was higher throughout the year from (NH₄)₂SO₄ or Ca(NO₃)₂ than from IBDU, thereby allowing luxury consumption and causing toxicity. The flower yield increased with increasing N rates. Complete doses of all N rates which were applied early during the vegetative growth gave the highest yields and the same N rates applied in split doses at different phases of plant growth decreased the yields. In addition, high N availability during flowering (caused by a split dose) further decreased the yield. At all application times, IBDU gave the highest yield and the differences in yields with (NH₄)₂SO₄ and Ca(NO₃)₂ were not significant. The leaf N concentration associated with maximum yield declined as the plant advanced towards flowering.     

Evaluation of methods of measurement of nitrogen in poultry and animal manures

Kjeldahl nitrogen (N), total N and forms of inorganic N (ammoniacal (NH₄)-N, nitrate (NO₃)-N and nitrite (NO₂)-N) were measured in a range of animal manures. The manures include fresh samples of poultry manure, sheep manure, horse manure, dairy slurry and pig slurry and composted poultry manure. Kjeldahl N was measured by standard micro-Kjeldahl digestion. For total N measurements, NO₃-N and NO₂-N were recovered during Kjeldahl digestion by pretreatments with various oxidizing and reducing agents. Inorganic forms of N were measured by extraction with 2M KCl solution.Kjeldahl digestion alone allowed measurement only of organic N and NH₄-N. Amongst various modifications to the Kjeldahl, pretreatment with either acidified (H₂SO₄) Zn-CrK(SO₄)₂ or acidified (H₂SO₄) reduced Fe achieved complete recovery of NO₃-N. Nitrite N was only recovered by first oxidising the NO ₂ ^- to NO ₃ ^- with KMnO₄ followed by reduction to NH₄-N with acidified (H₂SO₄) reduced Fe.More than 95% of the total N in fresh animal manure was present as organic N and NH₄-N which were recovered by the standard Kjeldahl digestion. In the case of fresh manures there was no difference between the amount of total N measured by the Kjeldahl digestion and its modified methods. However composting of poultry manure or drying of poultry manure, pig slurry and dairy slurry resulted in an increase in NO₃-N which was not recovered during Kjeldahl digestion alone. Under these conditions the total N could be measured by pretreating the samples with KMnO₄ and reduced Fe prior to Kjeldahl digestion.Drying of animal manures caused a decrease in organic N and NH₄-N, especially in poultry, pig and dairy manures. There was a slight increase in NO₃-N; but most of the decrease in N content with drying was attributed to the volatilization loss of ammonia (NH₃). Amongst various drying methods examined air drying caused maximum loss of N as NH₃ whereas freeze drying caused minimum loss of N. This suggests that fresh animal manures can be freeze dried for analysis of N which causes minimum loss of N.     

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.     

Uptake and apparent utilization of urea and ammonium nitrate in wheat seedlings

Intact wheat (Triticum aestivum cv. Quern) seedlings that were grown in presence or absence of NH₄NO₃ were exposed to solutions containing CO(NH₂)₂, NH₄NO₃, CO(NH₂)₂ + NH₄NO₃, CO(NH₂)₂ + KNO₃ and CO(NH₂)₂ + (NH₄)₂SO₄ for consecutive periods of 3, 3, 6, 12 and 24h and N uptake determined by solution depletion measurements. Differences in ethanol-soluble N and ethanol-insoluble N content of roots and shoots of control (zero time) seedlings and seedlings exposed to CO(NH₂)₂, NH₄NO₃ and CO(NH₂)₂ + NH₄NO₃ for 48 h were used to characterize N utilization during/following uptake.Regardless of initial N status, uptake of N from CO(NH₂)₂ was less than one-third of that from NH₄NO₃. Relative absorption of the CO(NH₂)₂ and NH₄NO₃ was not substantially altered by acidity control of the uptake solutions. There was a reciprocal antagonism between uptake of CO(NH₂)₂ and uptake of NH₄NO₃. Whereas CO(NH₂)₂ inhibited NH₄ absorption in each set of seedlings, it decreased NO₃ uptake only in seedlings that had been pretreated with N. Simultaneous presence of KNO₃ enhanced CO(NH₂)₂ uptake but presence of (NH₄)₂SO₄ decreased it to the same extent as NH₄NO₃. All absorption processes involving CO(NH₂)₂ and NH₄ were substantially restricted by pretreatment of the seedlings with NH₄NO₃. The results suggest that apparent utilization of ambient N was dependent on initial N status of the seedlings and on the nature of the N species to which they were exposed.     

Formation of a new solid β tricalcium orthophosphate structure,from reaction between hydroxyapatite and ammonium sulfate

The reaction which occur during heating, from room temperature to 1100°C, of a mixture of hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂ [HAP] and ammonium sulfate (NH₄)₂SO₄ [AS] are studied. The formation of Ca₂(NH₄)₂(SO₄)₃, Ca₂P₂O₇ and Ca(PO₃)₂ is observed between 200°C and 300°C; at 400°C CaSO₄ appears. From 500 to 700°C, Ca(PO₃)₂ reacts with Ca SO₄ and with HAP and gives β-Ca₂P₂O₇. Lastly, from 700°C to 1000°C, β-Ca₂P₂O₇ reacts with HAP and with CaSO₄ and gives β-Ca₃(PO₄)₂ [β-TCP]; From 1000 to 1100°C, β-TCP and CaSO₄ react and form a sulfate ion containing calcium phosphosulfate, the structure of which is β-TCP     

Effect of soil clay mineralogy on the efficiency of ammonium sulfate in flooded rice

The effect of soil clay mineralogy on the efficiency of (NH₄)₂SO₄ in flooded rice was investigated in a greenhouse pot trial with four clayey soils of diverse clay mineralogies (x-ray amorphous, montmorillonite, vermiculite, beidellite). KCl (75 kg K ha^–1) and triple superphosphate (25 kg P ha^–1) were incorporated in the soil with and without (NH₄)₂SO₄ (100 kg N ha^–1) before transplanting 1-week-old IR-36 rice seedlings which were then grown to maturity under flooded conditions. Efficiency of (NH₄)₂SO₄ was inferred from the response of agronomic characteristics such as tiller number, height, grain and straw yields to NH₄ fertilization.The results showed greatest efficiency of (NH₄)₂SO₄ on the x-ray amorphous soil, followed by montmorillonitic soil; efficiency was much lower on the vermiculitic and negligible on the beidellitic soil.Soil clay mineralogy may be an important factor in the reduced efficiency of NH₄ (or NH₄-forming) fertilizers in certain rice soils.     

Recovery of15N from ammonium nitrate and algal biomass-amended soil

A greenhouse experiment was conducted to compare the effectiveness of blue-green algae (Anabaena flos aquae) produced in a simulated inorganic-wastewater medium and NH₄NO₃ as sources of N for bermudagrass (Cynodon dactylon L.) on a Decatur silt loam soil (clayey, kaolinitic, thermic Rhodic Paleudult).¹⁵N-labeled blue-green algae and¹⁵N-labeled NH₄NO₃ were used as N sources to supply up to 300 mg N per pot (3 kg of soil). Bermudagrass was clipped at 42, 63, and 102 d after planting and dry matter yield, total, and¹⁵N were determined at each clipping. Results indicated a highly significant increase in total dry matter (shoots and roots) and N uptake over the control for both algae and NH₄NO₃ treatments at all N rates. There were no significant effects of N source on bermudagrass yields, but total N uptake was significantly higher with NH₄NO₃. The net mineralization of N from blue-green algal biomass ranged from 36 to 59% of the total N applied and the corresponding net release for NH₄NO₃ ranged from 65 to 86%. From 29 to 54% of the total N applied as blue-green algal biomass and from 50 to 75% of the N applied as NH₄NO₃ were assimilated by bermudagrass plants. For N rates above 100 mg N pot^–1, higher proportions of the labeled N in the shoots of the third harvest were derived from algal biomass than from NH₄NO₃. A large portion of the labeled N remained undecomposed or immobilized in the algae treated soil (41–64%) as compared to NH₄NO₃ treated soil (14–35%). More loss of N occurred in the NH₄NO₃ treatments from 3 to 15%, while the corresponding figures for algae treated soil were 2 to 8%.     

Effects of soil fumigation and N source on soil inorganic N and tomato growth

Soil fumigation, commonly used in vegetable production, may alter the rate of nitrification, affecting availability of N for crop use. The objective of this research was to examine effects of soil fumigation and N fertilizer source on tomato growth and soil NO₃–N and NH₄–N in field production. Experiments 1 and 2 included application of methyl bromide at 420 kg ha^-1 to a Norfolk sandy loam (fine loamy siliceous thermic Typic Kandiudult) in combination with preplant applications of calcium nitrate, ammonium nitrate, and ammonium sulfate at 144 kg N ha^-1. An additional fumigant, metam-sodium, was included in the second experiment at 703 L ha^-1 (268 kg sodium methyldithiocarbamate ha^-1). Experiment 3 included methyl bromide and metam-sodium, with ammonium sulfate as the sole source of N applied at 144 kg N ha^-1. In the first two studies, fumigants had little or no effect on soil NH₄–N or NO₃–N concentration. Tomato plants were larger and fruit yield was greater in fumigated plots, but there were few growth or yield responses to N source. In the third experiment, fumigants increased concentration of soil NO₃–N and NH₄–N at 16 days after fumigation (DAF), however, there was no effect on nitrification owing to fumigants. It appears that N source selection to overcome inhibition of nitrification is not necessary in plant production systems that involve fumigation     

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.     

Studies on the relationship between slurry pH,volatilization processes and the influence of acidifying additives

The mutual influence of slurry pH and volatilization processes on one hand, and the possibility of N conservation by the use of acidifying additives on the other, were investigated in static incubation experiments. The influence of the NH₃ and CO₂ volatilizations on slurry pH was studied by selectively supporting one or both processes. The addition of Ca²⁺ to slurry was compared to that of K⁺ and H⁺. The effects of Cl^–, SO ₄ ^2– and NO ₃ ^– as corresponding anions of Ca²⁺ on slurry pH as well as NH₃ and N₂O emissions were tested. The slurry pH (7.4) increased during incubation. When CO₂ volatilization was suppressed, the pH increase was reduced, and NH₃ volatilization was cut down by 50%. Ca²⁺ additions hardly influenced the initial slurry pH, but reduced the pH increases and NH₃ losses. Proton addition, in contrast, decreased slurry pH but did not decrease the subsequent pH rise. K⁺ had no effect on slurry pH and N losses. As compared to CaCl₂, CaSO₄ showed less effect on slurry pH and N losses. Ca(NO₃)₂ was nearly as effective as CaCl₂ in preventing NH₃ volatilization, but caused denitrification losses and elevated N₂O production. Titration curves of the different slurry treatments were used to interpret the results of the incubation experiments. In a microplot field experiment the NH₃ volatilization and slurry pH after surface application of slurry was measured. The acidifying and N conserving effects of Ca²⁺ and H⁺ additions were confirmed.     

Transformations and losses of fertilizer nitrogen on no-till and conventional till soils

A field study was conducted in 1982 to measure the effect of no-till (NT) and conventional till (CT) systems on N transformation after surface and subsurface applications of N fertilizers. Urea, urea-ammonium nitrate (UAN) solution, (NH₄)₂SO₄ (AS), and CA(NO₃)₂ were applied to NT and CT plots (5.95 m²) at a rate of 448 kg N ha^–1. A comparison of fertilizer N recovered in soils receiving incorporated or surface applied N was used to estimate NH₃ volatilization while denitrification was estimated from fertilizer N recovered in the presence and absence of nitrapyrin with incorporated N. Immobilization was assessed in microplots (0.37 m²) after surface application of (¹⁵NH₄)₂SO₄ to NT and CT systems at a rate of 220 kg N ha^–1.The results indicate little difference between NT and CT systems on urea hydrolysis rates and immobilization of surface applied fertilizer N. Approximately 50% and 10% of the surface applied N was recovered in the inorganic and organic fractions, respectively, on both tillage systems. The N not recovered was likely lost from plot areas through soil runoff. Incorporation of UAN, urea and AS resulted in 20 to 40% greater inorganic N recovery than from surface application. Nitrification rates were greater under the NT than the CT system. The similarities in concentration in the various N pools observed between the two tillage systems may be partially due to the short length of time that NT was imposed in this field study (<1 year) since other researchers using established tillage systems (>5 y) indicate that NT tends to promote decreased efficiency of fertilizer N.     

An investigation of the phase transformations in a CaSO4/(NH4)2SO4/H2O system,directed at the preparation of a fine dispersed purified phosphogypsum

The process of recrystallization of apatite phosphogypsum (PHG) in a solution ammonium sulphate (AS) with the subsequent decomposition of the binary salt was investigated and the resulting highly dispersed products with a low P₂O₅ content have been discussed. The following effects were examined: (NH₄)₂SO₄ concentration, the quantity of ammonium sulphate, the reaction temperature of phosphogypsum with (NH₄)₂SO₄ solution, the time of treatment of phosphogypsum with (NH₄)₂SO₄ solution and the decomposition of the binary salt, as well as the liquid/solid ratio for the binary salts, Based on the results of the chemical and X-ray analysis, it was established that, depending on the technological conditions of the process of recrystallization, binary salts of (NH₄)₂SO₄·CaSO₄·H₂O and of (NH₄)₂SO₄·CaSO₄·H₂O and of (NH₄)₂SO₄·5 CaSO₄·H₂O were formed. As a result of the investigations carried out, a product with a low P₂O₅ content, suitable for direct processing to secondary products has been prepared.     

Effect of gas-liquid phase compositions on NO2 and NO absorption into ammonium-sulfite and bisulfite solutions

The effect of gas-liquid phase compositions on NO and NO₂ absorption into ammonium-sulfite and bisulfite solutions is investigated. Preliminary experiment results indicate that the concentrations of (NH₄)₂SO₃ or NH₄HSO₃ solution and the molar ratio for HSO₃⁻ to the total solution concentrations all have significant impact on NO₂ and NO absorption rates. While the solution concentration is constant, the absorption of NO_x mixture is strongly related to the ratio NO₂/NO_x. The absorption rate of NO is primarily affected by NO₂ inlet concentration, and the NO absorption rate reaches the maximum value in (NH₄)₂SO₃ solution with the increase of NO₂ inlet concentration, which is determined by the reaction of NO and NO₂ with SO₃²⁻ as well as NO formation. Moreover, when the solution is NH₄HSO₃ the best ratio of NO₂/NO for the maximum value of the NO absorption rate becomes less or smaller. Meanwhile, the presence of NO in the gas phase is also favorable to the absorption rate of NO₂ in ammonium-sulfite or bisulfite solutions. The total results suggest that the coexistence of NO and NO₂ in the flue gas could enhance the absorption of each other to some extent.     

Separation performance of a nanofiltration membrane influenced by species and concentration of ions

Nanofiltration (NF), which has been largely developed over the past decade, is a promising technology for the treatment of organic and inorganic pollutants in surface and ground waters. The ESNA 1 membrane from the Nitto Denko Corporation of Japan is made of aromatic polyamide, which provides salt rejection from 50% to 90%. In this paper permeation experiments of aqueous solutions of five chlorides (NH₄Cl, NaCl, KCl, MgCl₂ and CaCl₂), three nitrates (NaNO₃, Mg(NO₃)₂ and Ca(NO₃)₂), and three sulfates (NH₄)₂SO₄, Na₂SO₄ and MgSO₄) were carried out. The effects of species and concentration of salts on the separation performance of the ESNA 1 membrane were investigated. The experimental results showed that the rejection to most salts by the ESNA 1 membrane decreased with the growth of the concentration. Then, the reflection coefficient and solute permeability of ESNA 1 membrane were calculated by the Spiegler-Kedem equation from experimental data. The reflection coefficients of the ESNA 1 membrane to salts are all above 0.95. The salt permeabilities, except for magnesium and calcium salts, increased with the growth of concentration. The sequence of rejection to anions by the ESNA 1 membrane is R(SO²⁻₄) > R(Cl⁻) > R(NO⁻₃) at the same concentration which ranges from 10 mol/m³ to 100 mol/m³. The sequence of rejection to anions by the ESNA 1 membrane can be written as follows: R(Na⁺) > R(K⁺) > R(Mg²⁺) > R(Ca²⁺) at 10 mol/m³ concentration and R(Mg²⁺) > R(Ca²⁺) > R(Na⁺) > R(K⁺) at 100 mol/m³ concentration.     

Author Index to Volume 38

X-ray photoelectron spectroscopy (XPS) is a powerful technique for determining the surface chemical composition of atmospheric particles. In this article, we employed XPS to study atmospheric particles collected from Guangzhou city in typical sites and seasons. The results showed that the weight percentage of carbon, oxygen, nitrogen, and sulfur were about 70.5–87.1%, and these species dominated the surface structure of the particles independent of the collection site and season. Inorganic elements including Si, Na, Ca, Cl, Fe, K, Al, and Cu were also found on the particle surfaces. The high-resolution XPS spectra revealed: (1) High aromatic and aliphatic C-H, and other oxidized carbons were found on the surface of particles. (2) The nitrogen species were characterized by pyridinic, pyrrolic/amide, quaternary type nitrogen functionalities, and nitrate groups, indicating that inorganic and organic N species are both important components of N-containing particles. (3) Sulfate and sulfone groups were also present on the surface and were important components. The oxidized groups of C, N, and S were higher in winter samples, consistent with the monsoon weather of Guangzhou in winter, which is favorable for the formation of oxidized species. A comparison between total and surface analyses showed that the surface of particles was relatively high in organic carbon, NO₃ ^?, and SO₄ ^2?, and the interior of particles was higher in NH₄ ⁺. These results provide information on the formation of aerosols, e.g., NH₄ ⁺ may act as a very important nucleus and organic carbon, NO₃ ^?, and SO₄ ^2? coat the nuclei during particle growth.     

Raman Microspectroscopic Analysis of Size-Resolved Atmospheric Aerosol Particle Samples Collected with an ELPI: Soot,Humic-Like Substances,and Inorganic Compounds

Raman microspectroscopy and mapping have been applied for the analysis of soot, humic-like substances (HULIS) and inorganic compounds in size resolved samples of air particulate matter collected with an electrical low pressure impactor (ELPI). Using several reference materials, we found that spectral parameters determined by curve fitting with five bands (G, D1-D4) enable a discrimination of soot and HULIS and provide information about the relative abundance and structural order of graphite-like carbon. In particular, the D1 band width exhibited a near-linear negative correlation with the ratio of apparent elemental carbon to total carbon in different types of soot.

The ELPI samples of sub-micrometer atmospheric particles exhibited essentially the same Raman spectra and parameters as standard diesel soot. In winter samples this was also the case for larger particles with aerodynamic diameters up to 4 μm. Spring and autumn samples, however, exhibited increased D1 band widths and D3 band intensities, indicating a high prevalence of HULIS in the size range of 2–4 μm. In addition, various nitrates and sulfates (mostly NaNO₃ and (NH₄)₂SO₄; some NH₄NO₃, Ca(NO₃)₂, Na₂SO₄, and CaSO₄) and small amounts of CaCO₃ were detected. Different single- and multi-component spectra indicated the presence of externally and internally mixed particles. The relative abundance of different chemical components in different particle size ranges was quantified in mapping experiments (0–55% NaNO₃, 1–15% (NH₄)₂SO₄, 10–45% soot/HULIS, 30–60% highly fluorescent organics). Overall, the results of this study demonstrate that Raman microspectroscopy and mapping can provide qualitative and quantitative information about the composition of ELPI aerosol samples.     

Comparative reactivity of treated FBC- and PCC-Fly ash for SO2 removal

Two types of fly ash from fluidized bed (FBC) and pulverized coal combustors (PCC) were treated with calcium hydroxide (Ca(OH)₂) to produce reactive SO₂ sorbents. Treatment was performed using 28.6 mass% Ca(OH)₂/fly ash mixtures slurried at 350 K for 8 h. Sulfation experiments were carried out in a thermogravimetric analyzer (TGA) at SO₂ concentration ranging from 0.11 to 0.67 vol% and 10(53–1153 K temperature range. At conditions close to those prevailing in an atmospheric FBC (1123 K, 3000 ppmv ami 20 vol% excess air), about 92% and complete conversion of CaO to CaSO₄ within 1 h reaction could be achieved with treated PCC and FBC fly ashes, respectively. Based on pore structural measurements for both sorbents, treatment enhanced the specific surface area (by about 8 times) as well as pore volume (by about 5 times). The shape of the N₂-adsorption/desorption isotherms, specific pore area, and pore volume distribution curves remained unchanged. Study of the intrinsic kinetics of the reaction between treated fly ash and S02 indicated a first order reaction with respect to SO₂ concentration up to 0.31 vol% SO₂ (3.36 × 10^?8 mol/cm³). Activation energies of 82.3 and 89.0 kJ/mol were calculated for treated PCC and FBC fly ashes, respsctively.     

Scavenging Ratios in an Urban Area in the Spanish Basque Country

For a period of six years (1995–2000) the scavenging ratio, which is the ratio of a pollutant's concentration in water to its concentration in air, collected at an urban site in the Spanish Basque Country was studied. The aerosol is characterized by SO₄ ^2? and NO₃? with 1.79 and 1.61 μg m^?3, respectively. Greater fractions of SO₄ ^2?, NO₃?, and NH₄+ ions were present in the fine particle range, while greater fractions of other ions appeared in the coarse range. The most important species found in the precipitation is SO₄ ^2? with 3.0 mg l^?1. NO₃?, Ca²⁺, and Cl^? are the second most important ions. The volume-weighted mean concentration of H⁺ is 4.6 μg l^?1 (pH = 5.3). The concentration of all analyzed ions (except H⁺) decreases throughout the rain event, showing the washout phenomenon of the rainwater. The scavenging ratio for the anthropogenic ions NO₃?, SO₄ ^2?, NH₄+, and K⁺ is lower than the scavenging ratio for the marine-terrigenous ions, Cl^?, Na⁺, and Ca²⁺.     

Calcium deficiency identified as an important factor limiting maize growth in acid ultisols of eastern Nigeria

Poor maize growth in unlimed acid soils of eastern Nigeria was investigated with a view to identify the main factors responsible for infertility in such soils. Surface soils collected from 4 sites in the region were amended with (i) CaSO₄ (ii) Ca(OH)₂ and (iii) MgCO₃. Maize was grown in each soil, including an untreated check, in the greenhouse for 4 weeks and tops and roots dry matter were measured.Although CaSO₄ depressed the pH of the soil, it caused a highly significant increase (p = 0.01) in the yield of dry matter of tops and roots and a non-significant increase in the uptake of P and Ca. Exchangeable Al was virtually eliminated when the soil was amended with MgCO₃ but maize growth in this soil was drastically inhibited and symptoms of severe calcium deficiency were observed. Higher yield increases, arising from soil amendment with Ca(OH)₂ relative to CaSO₄ were ascribed to better Ca nutrition rather than reduction in the level of exchangeable Al. Uptake of P and Ca was significantly increased (p = 0.05) by liming with Ca(OH)₂.The results suggest that Ca deficiency is a more serious growth-limiting factor than Al toxicity in the soils tested. The implication of this finding is that much money can be saved by using industrial wastes of relatively low neutralizing value, like cement fluke dust and basic slag, as soil amendments rather than the costly ocnventional liming materials.