Variation of Catalyst Structure and Catalytic Activity During Catalyst Preparation for Catalytic Ozonation of Heavy Oil Produced Water

Ni, Cu, and Ni-Cu metal oxides supported on granular activated carbon (GAC) were synthesized and used in catalytic ozonation of heavy oil produced water. The effect of preparation conditions on their catalyst composition, catalyst structure, and catalytic activity was investigated. The catalyst structure was characterized by X-ray power diffraction (XRD). The results revealed that the Ni-Cu/GAC has the highest catalytic activity, followed by Cu/GAC and Ni/GAC. Metal oxide loading rate depended on impregnation process, whereas dispersion of metal oxides was controlled by calcination process. The XRD analysis showed that the principal active phase was Cu₂O for Cu/GAC and Ni-Cu/GAC catalyst and NiO for Ni/GAC catalyst. The most active plane was Cu₂O₍₂₀₀₎ and then followed by Cu₂O₍₁₁₀₎ and Cu₂O₍₁₁₁₎ for Cu-supported catalysts. Higher calcination temperature and time favored the generation of Cu₂O but increased the crystalline diameter. It also suggested that promoting the generation of NiO and Cu₂O phase and reducing the crystalline diameter could improve the catalytic activity. During Ni-Cu/GAC preparation, existence of Ni(NO₃)₂ could accelerate the adsorption of Cu(NO₃)₂, promoting the generation of Cu₂O, and improve the dispersion of Cu₂O phase.

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Graphical Abstract ?

     

Effect of green synthesized molybdenum nanoparticles on nitrate accumulation and nitrate reductase activity in spinach

Abstract

In the present study, the green synthesized Mo nanoparticles (NPs) were firstly prepared using vermicompost extracts and, then, two experiments were separately carried out in a completely randomized design. The first experiment was conducted to investigate the effects of ammonium nitrate (AN) on nitrate (NO₃^?) accumulation rates as well as some other vegetative traits in spinach in four treatments and three replicates and the second experiment was done to investigate the effects of elemental Mo and green synthesized Mo NPs on NO₃^? accumulation, nitrate reductase (NR) activity and some morphological parameters in seven treatments with three replicates. The results of the first experiment indicated that the greatest accumulation of NO₃^? in the aerial parts of the plants was observed in the 3?M AN treatment. That is why the same concentration was utilized in the second experiment to study the effects of elemental Mo and green synthesized Mo NPs on the NR activity, NO₃^? accumulation and the other traits. The results of the second experiment indicated that various concentrations of elemental Mo and green synthesized Mo NPs have significant effects on all measured traits including the fresh and dry weights of the plant, NO₃^? concentration, NR activity, chlorophyll a (Chl a) and chlorophyll b (Chl b) rates, total chlorophyll (Chl a?+?b) and the plant height. Moreover, it was found that the green synthesized Mo NPs, as compared to elemental Mo, have a greater effect on the increase of NR activity and, consequently, significant reduction of NO₃^? accumulation. Abbreviations AN ammonium nitrate

Chl a chlorophyll a

Chl b chlorophyll b

Chl a?+?b the total chlorophylls

M Molar

Mo molybdenum

NPs nanoparticles

NR nitrate reductase

N nitrogen

NO₃^? nitrate

     

Post Plasma-Catalysis of Low Concentration VOC Over Alumina-Supported Silver Catalysts in a Surface/Packed-Bed Hybrid Discharge Reactor

In this study, the degradation of benzene by the means of an optimized surface/packed-bed hybrid discharge (SPBHD) plasma combined with γ-Al₂O₃-supported MO _x (M?=?Ag, Mn, Cu, or Fe) catalysts in post plasma-catalysis (PPC) system. The effects of Ag loading amount and gas hourly space velocity (GHSV) for plasma-catalysis degradation of benzene have been systematically investigated. The experimental result showed that the benzene degradation was improved and the mineralization process was greatly enhanced towards total oxidation after the combination of plasma with all MO _x /γ-Al₂O₃ catalysts. The AgO _x /γ-Al₂O₃ catalyst exhibited the best catalytic activity in benzene degradation than the other catalysts in PPC system. The highest benzene degradation efficiency of 96% and CO _x selectivity of 99% can be obtained for AgO _x /γ-Al₂O₃ catalyst with optimum Ag loading amount and GHSV of 15% and 22,856 h^?1, respectively. Time course of benzene degradation during PPC process indicated that the plasma-induced catalytic activity of AgO _x /γ-Al₂O₃ catalyst was temporary rather than lasting over a period after the plasma off. FT-IR analysis results revealed that the intermediate products (such as CO, HCOOH) and unwanted by-products (O₃ and NO _x ) generated in plasma process could be significantly inhibited by PPC process with AgO _x /γ-Al₂O₃ catalyst.     

Potassium Supply Influences Molybdenum,Nitrate, and Nitrate Reductase Activity in Eggplant

Abstract

Greenhouse experiments were conducted for two years (1993–1994) with eggplants to study the impact of potassium (K) as K₂SO₄ (0.5 mM, 1 mM, 2 mM, and 3 mM) on molybdenum (Mo) distribution and on aspects of nitrate (NO₃ ^?) metabolism, and fruit quality. The nitrates and Mo in leaf blades, petioles, and fruits as well as foliar in vivo nitrate reductase (NR; E.C. 1.6.6.1) activity were analyzed. In view of these results, the K application at levels exceeding 0.5 mM K, altered the NO₃ ^? and Mo status and distribution in the aboveground organs of eggplant. The 3 mM K distributed the NO₃ ^? proportionally between leaf blades, petioles, and fruits. The 0.5 mM K and the 1 mM K increased the NO₃ ^? and Mo concentration in fruits, respectively. These results indicated the 3 mM K the most appropriate treatment for the greenhouse eggplant production under Mediterranean climate conditions, with reduced NO₃ ^? density in fruits for human consumption.     

A Stable Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/Expanded Perlite Composite Catalyst for Degradation of Rhodamine B in Heterogeneous Photo-Fenton System

A stable and efficient Fe₂O₃/expanded perlite (Fe₂O₃-Ep) composite catalyst was synthesized by a simple hydrothermal method for degradation of refractory contaminants in heterogeneous photo-Fenton system. X-ray diffraction and FT-IR analyses confirmed the presence of the Fe₂O₃ in the synthesized catalyst. The catalytic activity of the Fe₂O₃-Ep catalyst was evaluated by the degradation of rhodamine B (RhB, 5 mg/L) and metronidazole (MET, 5 mg/L) in the presence of H₂O₂ under visible light irradiation. The Fe₂O₃-Ep catalyst exhibited high efficiency for degradation of RhB at a wide pH range from 2 to 10 and showed excellent catalytic property for decomposition of MET as well. The degradation ratio of RhB was achieved 99%, and the removal ratio of COD was 62% within 90 min at the best experimental conditions (0.5 g/L of Fe₂O₃-Ep catalyst, 2 mL/L of H₂O₂). Furthermore, iron leaching of the Fe₂O₃-Ep catalyst during the catalytic degradation reaction was negligible and the catalyst still exhibited high catalytic activity and stability after five cycles. These results show that the catalyst can be used as a highly efficient heterogeneous photo-Fenton catalyst for the degradation of non-biodegradable refractory pollutants in water.     

Denitrification in intact subsoil cores

 Intact, unamended subsoil cores taken from two contrasting field sites were incubated in the laboratory at 12  °C under aerobic (21% O₂) and anaerobic (1.1–5.5% O₂) conditions. Denitrification of ¹⁵N-NO₃ ^– diffusing into the cores across a semi-permeable membrane was estimated by: (1) direct observation of ¹⁵N-labelled N₂ and N₂O, and (2) mass balance following sectioning at the end of the experiment. The in situ denitrification potential (rates where the supply of NO₃ ^– is not limited by diffusion) was estimated using a finite-difference approximation to a diffusion reaction equation based on comparison of time and depth profiles of NO₃ ^– and Br^– in the incubated cores. Potentials between 0.2 and 2.5 mg N kg^–1 day^–1 were obtained under low O₂ and natural C concentrations. These results indicate the potential for denitrification in glacial till subsoils to reduce NO₃ ^– leaching to ground or surface waters to levels unlikely to result in a pollution hazard. The major product of NO₃ ^– reduction in these subsoils was observed to be N₂, rather than the greenhouse gas and catalyst of stratospheric O₃ removal, N₂O. Received: 31 October 1997     

Effect of Adding Flue Gas Desulphurization Gypsum on the Transformation and Fate of Nitrogen during Composting

The objective of this study was to investigate the effect of adding flue gas desulphurization gypsum (FGDG) on the transformation and fate of nitrogen during co-composting of dairy manure and pressmud of a sugar refinery. The ammonia absorption of FGDG was investigated. The changes in compost temperature, pH, electrical conductivity (EC), moisture, organic matter, the C/N ratio, Kjeldahl N, NH₄⁺-N, NO₂^?-N, NO₃^?-N were assessed. The addition of FGDG did not significantly affect compost temperature, pH, EC, moisture, and organic matter degradation. However, the addition of FGDG significantly increased the NH₄⁺-N content in the compost during the thermophilic phase, and the NH₄⁺-N maximal content in the compost with FGDG (CP+G) was 59.9% more than that in the compost without FGDG (CP–G). FGDG was thought to create the formation of (NH₄)₂SO₄ and the cation exchange between NH₄⁺ and Ca²⁺. The NO₂^?-N content in the CP+G peaked on day 15, and was not observed in the CP–G. In the final compost products, the NO₃^?-N concentration in the CP–G was more than that in the CP+G, which was 1451 (CP–G) and 1109 mg·kg^?1 (CP+G) dry material. This might be due to the NO₂^? accumulation in the CP+G, which accelerated N loss in the form of N₂O. There is a strong correlation between N₂O emission and NO₂^?-N accumulation in the composting process. Compared with the original N content in the compost mixture, the N loss in CP–G and CP+G were 15.0 and 10.8%, respectively. These results revealed that NH₄⁺-N conservation effect was improved during the thermophilic phase and the total N loss was mitigated by adding FGDG into composting materials. FGDG could be utilized as a potential amendment to conserve nitrogen during composting.     

Effects of nitrite toxicity on soil bacteria under aerobic and anaerobic conditions

Isolates of a soil Pseudoimonas, as well as other soil bacteria, showed a different sensitivity towards NO^?₂ when grown under aerobic or anaerobic conditions. The tolerance to NO^?₂ was increased in the presence of O₂: for instance, a concentration of $\text{200parts}\text{10}{}^6$ of NO^?₂-N proved to be toxic to a Pseudomonas sp. under anaerobic conditions, whereas over $\text{400 parts}\text{10}{}^6$ were needed aerobically to suppress its growth completely. The addition of NO^?₃ as an electron acceptor for anaerobic respiration did not overcome the inhibitive effect of NO^?₃. The pH range, at which NO^?₂ was utilized anaerobically, was narrowed with increasing NO^?₂ concentration (pH 6.8–8.8 at $\text{70 parts}\text{10}{}^6$ of NO^?₂-N and 7.4–8.5 and $\text{140 parts}\text{10}{}^6$ of NO^?₂-N).Tolerance to nitrite varied considerably among the bacteria tested. Each species was able to overcome the inhibitory effect of NO^?₂ up to a certain concentration, while the length of the lag phase was related to NO^?₂ concentration.     

Organics Wastewater Degradation by a Mesoporous Chromium-Functionalized γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> with H<Subscript>2</Subscript>O<Subscript>2</Subscript> Assistance

In this study, a mesoporous chromium-functionalized γ-Al₂O₃ (Cr/γ-Al₂O₃) catalyst was prepared by an impregnation method, and the catalytic activity was evaluated by the degradation of organics wastewater. The prepared catalyst was characterized by X-ray photoelectron spectroscopy, X-ray diffraction, nitrogen adsorption-desorption experiments, and scanning electron microscopy. The characterization results confirmed that the pores in the Cr/γ-Al₂O₃ catalyst distributed broadly in the mesoporous region, and the active chromium species were highly dispersed on the catalyst surface. The catalytic activity tests showed that the Cr/γ-Al₂O₃ catalyst exhibited a superior performance for the degradation of organics wastewater with H₂O₂ assistance. And the methylene blue (MB) disappeared within 20 min and the COD removal reached 76.5% within 40 min for the MB-simulated wastewater; for the phenol-simulated wastewater, the phenol removal was above 95% and the corresponding COD removal reached 71% within 40 min. Such an excellent catalytic performance demonstrates that the Cr/γ-Al₂O₃ catalyst has a potential application in the degradation of complex organics wastewater simultaneously.     

Participation of iron in denitrification in waterlogged soil

A study was made of the formation of anaerobiosis in a waterlogged soil. A dilute soil suspension containing NO^?₃, Fe³⁺, sodium citrate, a limited amount of O₂, and trace elements was used as a model of waterlogged soil. Polarography was used to detect dissolved O₂, Fe³⁺ and Fe²⁺. The fates of the NO^?₃ and Fe³⁺ during and after O₂ consumption by the microorganisms were studied in a specially designed vessel. A close correspondence was obtained between the reduction of NO^?₃, NO^?₂ and Fe³⁺ and the growth of denitrifying bacteria in the closed system employed. From the experimental results we presume that microorganisms which respire NO^?₃ are also capable of utilising Fe³⁺ in their respiration. The mechanisms of reduction of these chemical species by the microorganisms are also discussed, emphasising the possibility of the participation of chemical reduction of NO^?₂ by Fe²⁺ in the over-all reduction process.     

Physiological changes in soybean treated with ozone and molybdenum

Abstract

An open‐top field chamber experiment was conducted to evaluate the impact of Molybdenum (Mo) addition to soil on the physiological changes in soybean (Glycine max L. Merrill) exposed to ozone (O₃). Plants grown with Mo (0, 1.0, or 2.0 mg kg"¹ soil dry weight) were exposed to O₃ (O, 0.06, or 0.12 μmol mol^‐1) in open‐top field chambers for 12 h d^‐1 for 21 d with a N‐free fertilizer, during the sensitive growth stage (R2). The rate of photosynthesis (PN), specific root nodule nitrogenase activity (SNA), leaf nitrogen (N), chlorophyll (chl‐a, chl‐b) and biomass of soybean were measured. The increase in O₃ levels significantly reduced PN, SNA, leaf‐N, chl‐a, chl‐b, and biomass. Addition of Mo increased leaf‐N, shoot, root, and nodule dry weights but did not change PN, SNA, or chlorophyll. The addition of Mo (2 mg kg ^‐1) helped in significantly increasing PN and chlorophyll in the presence of 0.06 umol mol^‐1 O₃ but no change was observed in the presence of 0.12 μmol mol^‐1 O₃.     

Effect of sodium chloride on denitrification in glucose amended soil treated with ammonium and nitrate nitrogen

Laboratory incubations were conducted to study the effect of sodium chloride (NaCl) on denitrification and respiratory gases (CO₂, O₂) from soil treated with ammonium or nitrate and incubated at 20 % moisture. The same samples were assayed for denitrifying enzyme activity (DEA) after incubation at 40 % moisture with glucose and NO₃^–. Under aerobic conditions (20 % water content), a flush of activity was observed at 6 hours after start of incubation and subsided to negligible levels at 12 hours. Sodium chloride significantly depressed N₂O and CO₂ emissions and O₂ consumption. Significantly more loss of N₂O occurred from NH₄⁺‐ than NO₃^–‐treated soil at all NaCl levels and was attributed to higher microbial activity. A highly significant positive correlation was obtained between N₂O emission and respiratory gases. The respiratory quotient (CO₂ evolved/O₂) was higher for NH₄⁺‐treated soil and decreased with the amount of NaCl. At 40 % moisture, N₂O emissions were higher than at 20 % and peaked at 37 hours followed by a sharp decrease. Short‐term incubations of soil with NH₄⁺ or NO₃^– did not have an effect on denitrifying enzyme activity (DEA) while NaCl had a positive effect, particularly in previously NO₃^–‐treated soil.     

氮素不同形态配比对菜用大豆生长、种子抗氧化酶活性及活性氧代谢的影响

通过蛭石盆栽试验,研究了氮素不同形态配比对菜用大豆[Glycine max (L.) Merr.]品种"理想95-1"生长、种子抗氧化酶活性及活性氧代谢的影响。结果表明,营养液中适宜的硝铵比(75∶25)有利于菜用大豆的生长发育,植株具有最大生物量;在高比例的硝态氮(100%)和铵态氮(75%)处理下,植株的干重、鲜重及产量均显著降低,以硝铵比为25∶75处理下尤为显著。在适宜的硝铵比(75∶25和50∶50)处理下,菜用大豆种子具有较低的抗氧化酶活性,活性氧代谢产物O2、过氧化氢(H2O2)和膜脂过氧化产物丙二醛(MDA)含量也较低,表明植株受到的氧化胁迫程度较低;而在硝铵比为25∶75处理中,抗氧化酶活性最高,O2生成速率、H2O2和MDA含量也最高,表明过多的铵态氮对细胞膜造成了伤害,所受的氧化损伤程度较重。     

薄层营养液膜技术(NFT)水培多年生黑麦草对不同富氮废水的净化效果

采用薄层营养液膜技术(NFT)培育多年生黑麦草(Lolium perenne L),以草带为植物滤器净化5种不同配置的富氮废水,废水10 d更换一次.试验结果表明在短期内(2d),TAN、NO-2-N和NO-3-N的去除量均在本身高水平而其他成分低水平的试验组达到最高,4组非离子氨UIA的净化率均高于99%.所有废水的pH值在2 d后均被控制在6.5～8.0.以上述3种氮90%的净化率为目标,废水G3(初始浓度为TAN:40 mg·L-1,NO-2-N:40 mg·L,NO-3-N:10 mg·L-1)和CK(仅在26.77 L自来水中加入18.36 g四水硝酸钙)需2d,废水G4(TAN:40 mg·L-1,NO-2-N:4 mg·L-1,NO-3-N:10 mg·L-1)需4 d,废水G1(TAN:140 mg·L-1,NO-2-N:40 mg·L-1,NO-3-N:80 mg·L-1)、废水G2(TAN:140mg·L-1,NO-2-N:40 mg·L-1,NO-3-N:10 mg·L-1)仅TAN和NO-2-N在6 d内完成.试验结束时G3草净增长最高(169.3 mm),并获得最大干草产量0.205 kg·m-2,G4获得最大鲜草产量1.48 kg·m-2.     

两个品种水稻中硝酸盐吸收和利用率对氮素饥饿的响应特征

Ammonium（NH＋4） is the main nitrogen（N） form for rice crops, while NH＋4near the root surface can be oxidized to nitrate（NO-3）by NH＋4-oxidizing bacteria. Nitrate can be accumulated within rice tissues and reused when N supply is insufficient. We compared the remobilization of NO-3stored in the tissue and vacuolar between two rice（Oryza sativa L.） cultivars, Yangdao 6（YD6, indica）with a high N use efficiency（NUE） and Wuyujing 3（WYJ3, japonica） with a low NUE and measured the uptake of NO-3, expression of nitrate reductase（NR）, NO-3transporter genes（NRTs）, and NR activity after 4 d of N starvation following 7-d cultivation in a solution containing 2.86 mmol L-1NO-3. The results showed that both tissue NO-3concentration and vacuolar NO-3activity were higher in YD6 than WYJ3 under N starvation. YD6 showed a 2- to 3-fold higher expression of OsNRT2.1 in roots on the 1st and 4th day of N starvation and had significantly higher values of NO-3uptake（maximum uptake velocity, Vmax） than the cultivar WYJ3.Furthermore, YD6 had significantly higher leaf and root maximum NR activity（NRAmax） and actual NR activity（NRAact） as well as stronger root expression of the two NR genes after the 1st day of N starvation. There were no significant differences in NRAmax and NRAact between the two rice cultivars on the 4th day of N starvation. The results suggested that YD6 had stronger NRA under N starvation, which might result in better NO-3re-utilization from the vacuole, and higher capacity for NO-3uptake and use, potentially explaining the higher NUE of YD6 compared with WYJ3.     

不同肥土比对NO3——-N浓度变化的影响研究

采用室内培养方法,对不同肥土比对NO3--N浓度变化的影响及可能机理进行了探讨。结果表明,肥土比为1∶400(处理G)可能是引起土壤性质变化的一个敏感量,NO3--N浓度、脲酶活性和硝化细菌数量在肥土比低于G处理时随尿素用量的增加而增加,高于G处理时随尿素用量增加而下降。尿素用量增加引起的土壤pH值变化是硝化与反硝化细菌数量和脲酶活性变化的主要原因,也是影响土壤中NO-3--N浓度变化的重要因素。     

A Comparison of Trace Gases and Particulate Matter over Beijing (China) and Delhi (India)

Air pollution represents a significant fraction of the total mortality estimated by the World Health Organization (WHO) global burden of disease projec?t (GBD). The present paper discusses the characteristics of trace gases (O₃, NO, NO₂, and CO) and particulate matter (PM₁₀ and PM_2.5) in two Asian megacities, Delhi (India) and Beijing (China). A continuous measurement of trace gases and particulate matter are considered from 12 measuring sites in Beijing and 8 sites in Delhi. Over Beijing, the annual average of PM_2.5, PM₁₀, O₃, NO₂, and CO is, respectively, 85.3, 112.8, 58.7, and 53.4 μg/m³ and 1.4 mg/m³, and, respectively, over Delhi 146.5, 264.3, 24.7,and 19.8 μg/m³ and 1.73 mg/m³. From the spatial variations of pollutants, the concentrations of particulate matter and trace gases are observed to be much higher in the urban areas compared to the suburban areas. The higher average concentrations of PM₁₀ and PM_2.5 over Delhi and Beijing are observed during winter season compared with other seasons. The maximum diurnal variation of PM₁₀ concentration is observed during winter season over Beijing and Delhi. The comparison of trace gases shows that the O₃ concentrations during daytime are obviously higher compared with nighttime, and the highest diurnal variation of O₃ is observed during summer. The concentrations of CO are highest during winter season, and higher concentrations are observed during nighttime compared to daytime. The O₃ and CO show negative correlation over Beijing and Delhi. The negative correlation between O₃ and NO₂ is merely observed over Beijing, while CO and NO₂ concentrations, in contrast, show positive correlation over Beijing.     

Effects of Arbuscular Mycorrhizal Fungi and Ammonium: Nitrate Ratios on Growth and Pungency of Onion Seedlings

ABSTRACT

A pot experiment was conducted to study the growth and pungency of Allium cepa L. grown in Perlite as affected by colonization by the arbuscular mycorrhizal (AM) fungi Glomus versiforme and Glomus intraradices BEG141 and by ammonium:nitrate (NH₄ ⁺:NO₃ ^?) ratios of 3:1, 1:1, and 1:3 in 4 mM solutions. Plants were harvested when bulb formation commenced. In general, mycorrhizal colonization resulted in increased shoot dry weight, shoot length, sheath diameter, root nitrogen (N) and phosphorus (P) content (except with G. intraradices and a NH₄ ⁺:NO₃ ^? ratio of 1:3), shoot N and P concentrations (except with G. versiforme and a NH₄ ⁺:NO₃= ratio of 3:1) and content. Plants inoculated with G. versiforme had higher growth parameters and N and P content than those with G. intraradices, whereas N and P concentrations showed the opposite trends. Growth parameters and N and P content of non-mycorrhizal plants were highest at a NH₄ ⁺:NO₃= ratio of 1:3, while those of plants inoculated with G. versiforme or G. intraradices were highest at a ratio of NH₄ ⁺:NO₃ ^? 3:1 or 1:1. Neither mycorrhizal colonization nor proportion of inorganic N species significantly affected bulb enzyme-produced pyruvate or total or organic sulfur (S) concentrations in plant shoots. Colonization by AM fungi made a substantial contribution to onion growth and may not have been directly related to bulb pungency at early stages of plant growth. However, the influence of AM fungi on plant N and P metabolism may have implications for onion flavor at later stages of plant growth.     

Comparative Study of the Leachates from Syngonium podophyllum using Different Fertilization Techniques and Nitrogen Forms

The objectives of this article were to analyze the evolution of the nutrient parameters of the leachates collected from Syngonium podophyllum var. Silver plants cultivated for 20 weeks in a buried greenhouse with four methods of fertilization. The treatments were T₁, standard liquid feeding (SLF) [7.0 mmol L^?1 nitrate (NO₃ ^?) nitrogen (N), 0.3 mmol L^?1 phosphorus (P), and 3.5 mmol L^?1 potassium (K)] after transplanting; T₂, liquid feeding soluble fertilizer (LFSF) [6.9% NO₃ ^? N, 11.1% ammonium (NH₄ ⁺) N stabilized by 3,4-dimethylpyrazole phosphate, 8.0% P₂O₅, and 14.0% K₂O] after transplanting; T₃, controlled release fertilizer (CRF I) (7.4% NO₃ ^? N, 8.6% NH₄ ⁺ N, 8.0% P₂O₅, and 12.0% K₂O) applied before planting and half concentration of SLF from 45 days after transplanting; and T₄, controlled release fertilizer (CRF II) (8.5% NO₃ ^? N, 7.5% NH₄ ⁺ N, 8.0% P₂O₅, and 12.0% K₂O) applied before planting and half concentration of SLF from 45 days after transplanting. Solution pH, electrical conductivity (EC), NO₃ ^? N, NH₄ ⁺ N, K, and P concentrations in the leachate were analyzed weekly. Plant quality was assessed at the end of the trial through objective and subjective parameters. Significant differences among the different fertilization methods were observed. CRF treatments resulted in the greatest nutrient leachate concentration during the first 6 weeks of the study, and afterward it decreased gradually until the end of the cultivation. CRF I showed greater leachate concentrations of N, P, and K than the others during the first half of the study. The concentrations of NO₃ ^? N and P from all the fertilizer types were often above the permissible levels cited in the federal Clean Water Act. The best-quality plants were obtained with CRF II, whereas the greatest height and Aerial Dry Weight (ADW) were obtained with CRF treatments and the greatest Root Dry Weight (RDW) was obtained with the NH₄ ⁺ N treatments.     

Effects of air pollution on the searching behaviour of an insect parasitoid

To assess the impact of air pollutants on the population dynamics of herbivores, the effects of pollutants on their natural enemies including predators, parasites, and pathogens must be evaluated in addition to direct effects and indirect effects mediated via the host plant. Insect parasitoids are an important group of such natural enemies providing many examples of partial or complete biological control of pest species. This study examined the effects of air pollutants (ozone (O₃), sulphur dioxide (SO₂), and nitrogen dioxide (NO₂)) on the searching behaviour of insect parasitoids. A series of experiments comprising short-term, closed chamber fumigations of O₃, SO₂, and NO₂ (100 nl l^?1) of the braconid parasitoid (Asobara tabida) and aggregated distributions of its host larvae (Drosophila subobscura) was set up. Analysis of chamber results showed that the proportion of hosts parasitised and the searching efficiency of the parasitoids were both significantly reduced with O₃ fumigation, but not with NO₂ or SO₂ fumigations. O₃ fumigation reduced percentage parasitism by approximately 10%. Parasitoids were able to avoid patches with no hosts, both in filtered air controls and when exposed to pollutants. However in the O₃ and NO₂ treatments they appeared less able to discriminate between different host densities, suggesting that pollutants may interfere with the olfactory responses of the parasitoids. These results indicate the potential for air pollutants, particularly O₃, to negatively influence the searching behaviour of parasitoids, and hence reduce the efficiency of natural enemy control of many pest species.