Ion Selective Electrode Determination of Ammonia Nitrogen in Passaic River Waste Water in New Jersey Essex County Area

The percent ammonia nitrogen was determined in Passaic River waste water using Ion-Selective Electrode EPA Method 350.3. The intelligent ammonia sensor integrates ammonia electrode, pH electrode and Ammonia Ion electrode together to realize the in situ detection of ammonia. The test results have shown that the sensor is easy operation, low cost and no pollution. The ammonia is determined potentiometrically using an ammonia ion selective electrode and a pH/mV meter, having an expanded millivolt scale. The ammonia selective electrode uses a hydrophobic gas-permeable membrane to separate the sample solution from an electrode internal solution of ammonium chloride. Dissolved ammonia is converted to NH3 gas by raising the pH to above 11.0 with a strong base. NH3 gas diffuses the membrane and changes the internal solution pH that is sensed by the electrode. In single laboratory test results have been found 1.001 NH3-/L and 0.897 mg NH3-N/L, recoveries were 77.3% and 83.1%, respectively.

基于^(15)N稳定同位素示踪技术的植物组合湿地对氨氮去除途径研究

人工湿地是生态修复受污染水体的重要手段,对氮的去除效果显著,但不同植物湿地对氮去除效果差异明显,因此不同类型植物组合后的湿地对氮去除效果及去除途径值得进一步研究。通过室内控制试验,以常见浮水植物绿狐尾藻(Myriophyllum elatinoides)和挺水植物梭鱼草(Pontederia cordata)为研究对象,利用^(15)N稳定同位素示踪技术探究绿狐尾藻、梭鱼草及绿狐尾藻+梭鱼草植物组合对氨氮(NH_(4)^(+)-N)的去除途径。结果表明,绿狐尾藻+梭鱼草植物组合处理相较于单一绿狐尾藻和梭鱼草处理对氮的脱除量分别提高1.8%和3.6%。基于^(15)N质量平衡,绿狐尾藻、梭鱼草和绿狐尾藻+梭鱼草植物组合处理氮去除途径的底泥吸附贡献分别为8.30%、7.96%和6.94%,植物吸收贡献分别为41.76%、35.34%和48.67%,微生物作用去除贡献分别为49.94%、56.71%和44.39%。微生物作用在湿地脱氮过程中占主导地位。相较于单一植物湿地,植物组合湿地对氮的去除效果得到提升,同时促进了植物对水体NH 4+-N的吸收。该研究有助于更好地理解植物组合湿地对氨氮的脱除途径。

应用^(15)N自然丰度值揭示不同氮源对设施土壤氨挥发的贡献

【目的】我国设施蔬菜生产中普遍存在着氮肥施用过量、氨气(NH_(3))挥发损失严重等问题。通过^(15)N自然丰度法,研究不同肥料类型对土壤NH_(3)挥发的影响,并定量分析其贡献率,为实现降低氮素损失的氮肥科学管理提供依据。【方法】开展为期40天的番茄盆栽培养试验,供试土壤为棕壤,未施过肥也未种植过作物,供试作物为番茄。试验设置4个处理,即不施氮肥(CK)和等量施氮(N3 g/pot)条件下单施鸡粪有机肥(M)、单施尿素(U)、有机肥半量替代尿素(MU)处理。利用被动采样器测定了土壤NH_(3)挥发速率和累积排放量,并借助^(15)N自然丰度方法估算肥料和土壤氮对NH_(3)挥发的贡献。【结果】基肥施用后3~6天内,NH_(3)挥发速率迅速增加并达到高峰,之后逐渐降低,直至第33天恢复到施肥前水平。与MU和U处理相比,M处理的净NH_(3)挥发累积量分别显著降低了60.8%和63.1%(P<0.05),MU较U处理的NH_(3)减排效果不显著(4.62%),相应的NH_(3)挥发系数分别为1.37%(U)、1.29%(MU)及0.51%(M)。施肥处理中,δ^(15)N-NH_(3)值随NH_(3)挥发的进行而迅速降低,然后逐渐增加至施肥前水平,M处理的δ^(15)N-NH_(3)均值高于MU和U处理。^(15)N同位素混合方程计算显示,在番茄生产中肥料对NH_(3)挥发的贡献比例为:M处理中鸡粪贡献30.5%,U处理中尿素贡献53.1%,MU处理中鸡粪和尿素分别贡献28.6%和56.6%。【结论】等量施氮条件下,单施鸡粪产生的NH_(3)挥发量远低于尿素,鸡粪和尿素等量氮配施对NH_(3)挥发的减排效果不显著。根据同位素分馏效应计算结果,单施鸡粪、尿素对土壤NH_(3)挥发源的贡献比例分别为30.5%、53.1%,鸡粪和尿素配施时二者对土壤NH_(3)挥发源的贡献比例分别为28.6%、56.6%,贡献比例与单施差异不大。因此,控制化肥氮施用量是减少NH_(3)挥发的关键。

Effects of Coagulation and Ozonation Pretreatments on Biochemical Treatment of Fluid Catalytic Cracking Wastewater

Fluid catalytic cracking (FCC) salty wastewaters, containing quaternary ammonium compounds (QACs), are very difficult to treat by biochemical process. Anoxic/oxic (A/O) biochemical system, based on nitrification and denitrification reactions, was used to assess their possible biodegradation. Because of the negative effects of high salt concentration (3%), heavy metals and toxic organic matter on microorganisms’ activities, some techniques consisting of dilution, coagulation and flocculation, and ozonation pretreatments, were gradually tested to evaluate chemical oxygen demand (COD), ammonia-nitrogen (ammonia-N) and total nitrogen (TN) removal rates. In this process of FCC wastewater, starting with university-domesticated sludge, the ammonia-N and TN removal rates were worst. However, when using domesticated SBR’s sludge and operating with five-fold daily diluted influent (thus reducing salt concentration), the ammonia-N removal reached about 57% while the TN removal rate was less than 37% meaning an amelioration of the nitrification process. However, by reducing the dilution factors, these results were inflected after some days of operation, with ammonia-N removal decreasing and TN barely removed meaning a poor nitrification. Even by reducing heavy metals concentration with coagulation/flocculation process, the results never changed. Thereafter, by using ozonation pre-treatment to degrade the detected organic matter of di-tert-butylphenol and certain isoparaffins, COD, ammonia-N and TN removal rates reached 92%, 62% and 61%, respectively. These results showed that the activities of the microorganisms were increased, thus indicating a net denitrification and nitrification reactions improvement.

N-甲基二乙醇胺脱碳效果的仿真研究分析

为解决当前合成氨脱碳工艺过程中脱碳效果不佳无法满足0.2%要求的问题,在对MDEA脱碳工艺进行简单概述的基础上,对实际生产中的生产参数进行采集并初步分析了导致脱碳效果不佳的主要问题;而后,基于ASPEN PLUS软件建立MDEA脱碳工艺数值模拟仿真模型,重点对吸收塔压力、MDEA浓度以及贫液量对脱碳效果的影响进行仿真分析,得出最适宜生产参数。

抑制剂NBPT对紫色土稻油轮作体系氨挥发和产量的影响

【目的】施用尿素时使用脲酶抑制剂有利于减少稻田氨挥发损失提高稻田氮肥利用效率,但对水稻-油菜轮作体系下氨挥发损失的影响并不是很清楚。研究紫色土丘陵区域稻油轮作模式体系下,不同脲酶抑制剂n-丁基硫代磷酰三胺(NBPT)添加量对氨挥发、氮沉降和产量的影响,可为四川省紫色土丘陵区域农业面源污染防治提供技术支撑。【方法】结合当地农民施肥习惯,设置了5个处理,分别为T0(不施肥)、T1(尿素)、T2(添加为纯氮施用量的0.1%脲酶抑制剂NBPT处理的尿素)、T3(添加为纯氮施用量的0.2%脲酶抑制剂NBPT处理的尿素)和T4(添加为纯氮施用量的0.5%脲酶抑制剂NBPT处理的尿素),均为基肥一次性施入,分别在水稻季和油菜季开展试验。【结果】T1、T2、T3和T4处理在水稻季累积氨挥发损失率为26.54%、18.28%、14.88%和12.78%,在油菜季为5.22%、1.57%、1.36%和1.31%。与T1相比,T2、T3和T4处理在水稻季累积氨挥发降低了31.14%、43.96%和51.82%,在油菜季降低了70%、74.04%和74.89%。但是在水稻季和油菜季T2、T3和T4之间处理累积氨挥发损失没有显著性变化。在整个稻油轮作体系,铵态氮沉降量约为硝态氮沉降量的1.86倍,占整个无机氮沉降的63.94%。此外,与T1处理相比,T2、T3和T4处理能够显著增加作物产量和氮肥农学利用效率,但T2、T3和T4处理之间作物产量和氮肥农学利用效率并不存在显著性差异。【结论】与单纯施用尿素相比,使用脲酶抑制剂NBPT能够显著降低氨挥发损失、提高作物产量和氮肥利用率。铵态氮为农田氮沉降的主要沉降形式。

Oxygen consumption and ammonia-N excretion of Meretrix meretrix in different temperature and salinity

Effects of temperatures and salinities on oxygen consumption and ammonia-N excretion rate of clam Meretrix meretrix were studied in laboratory from Oct. 2003 to Jan. 2004. Two schemes were designed in incremented temperature at 10, 15, 20, 25°C at 31.5 salinity and in incremented salinity at16.0, 21.0, 26.0, 31.5, 36.0, and 41.0 at 20°C, all for 8-10 days. From 10 to 25°C, both respiration and excretion rate were increased. One-way ANOVA analysis demonstrated significant difference (P<0.01) in physiological parameters in this temperature range except between 15 and 20°C. The highest Q10 thermal coefficient value (12.27) was acquired between 10 and 15°C, and about 1 between 15 and 20°C, indicating M. meretrix could well acclimate to tem- perature changes in this range. Salinity also had significant effects on respiration and excretion rate (P<0.05). The highest values of respiration and excretion rate of M. meretrix were recorded at 16.0 salinity (20°C). These two physiological parameters decreased as salinity increased until reached the minimum Q10 value at 31.5 (20°C), then again, these parameters increased with increasing salinity from 31.5 to 41.0. M. meretrix can catabolize body protein to cope with osmotic pressure stress when environmental salinity is away from its optimal range. No significant difference was observed between 26.0 and 36.0 in salinity (P>0.05), suggesting that a best meta- bolic salinity range for this species is between 26.0 and 36.0.

Ammonia Volatilization and Nitrogen Utilization Efficiency in Response to Urea Application in Rice Fields of the Taihu Lake Region,China

响应到稻田的脲申请的氨挥发损失，氮利用效率，和米饭收益在 Wangzhuang 镇上被调查， Changshu 城市，江苏省，中国。N 化肥处理，适用在三倍，是 0 (控制) ， 100， 200， 300，或 350 kg N 哈 ? 1。在脲被用于地面水以后，一个连续气流包围方法被用来在稻田测量氨挥发。通过氨挥发的全部的 N 损失通常与 N 申请率，和申请评估的二更高的 N 增加了(300 和 350 kg N 哈 ? 1 ) 证明 N 的更高的比率通过氨挥发输了到应用 N。由在全部米饭期间，生长上演的氨挥发的全部的氨损失从 9.0% ～ 16.7% 应用 N 。增加申请率通常减少了在到在植物的 N 的种子的 N 的比率。为所有 N 处理，氮肥利用效率从 30.9% ～ 45.9%。有最高的 N 率的剩余 N 导致了米饭植物，氮肥利用的减少的率，和减少的米饭收益的住宿。从这个实验计算，最节俭的 N 化肥申请率是 227 kg 哈 ? 1 为在泰胡·莱克区域的水稻土的类型。然而，推荐适当 N 化肥申请率以便植物生长被提高，氨损失被减少能改进大米的 N 利用效率。

EFFECTS OF REDUCED SALINITY ON OXYGEN CONSUMPTION AND AMMONIA-N EXCRETION OF CHLAMYS FARRERI

Effects of reduced salinity on the oxygen consumption rate (OCR) and the ammonia N excretion rate (AER) of scallop Chlamys farreri (3.2 5.9 cm in shell height, 0.147 1.635 g in soft tissue dry weight ) were studied in laboratory from March 21,1997 to April 16, 1997. Under the controlled conditions of reduced salinity from 31.5 to 15.0 and ambient temperature 17℃ and 23℃, the concentrations of dissolved oxygen and ammonia N were determined by the Winkle method and the hypobromite method, respectively. Results showed that with controlled reduced salinity, the mean values of the OCR were 2.17 mg/(g.h) at 17℃, and 2.86 mg/(g.h) at 23℃and that the mean values of the AER were 178.0 μg/(g.h) at 17℃ and 147.0 μg/(g.h) at 23℃. The OCR and the AER decreased with reducing salinity from 31.5 to 15.0 both at 17℃ and 23℃. The effects of reduced salinity on the OCR and the AER of scallop C. farreri could be represented by the allometric equation and the exponential equation, respectively.

Ammonia Volatilization and Denitrilfication Losses from an Irrigated Maize-Wheat Rotation Field in the North China Plain

Ammonia (NH3) volatilization, denitrification loss, and nitrous oxide (N2O) emission were investigated from an irrigated wheat-maize rotation field on the North China Plain, and the magnitude of gaseous N loss from denitrification and NH3 volatilization was assessed. The micrometeorological gradient diffusion method in conjunction with a Bowen Ratio system was utilized to measure actual NH3 fluxes over a large area, while the acetylene inhibition technique (intact soil cores) was employed for measurement of denitrification losses and N2O emissions. Ammonia volatilization loss was 26.62% of the applied fertilizer nitrogen (N) under maize, while 0.90% and 15.55% were lost from the wheat field at sowing and topdressing, respectively. The differences in NH3 volatilization between different measurement events may be due to differences between the fertilization methods, and to differences in climatic conditions such as soil temperature.Denitrification losses in the fertilized plots were 0.67%-2.87% and 0.31%-0.49% of the applied fertilizer N under maize and wheat after subtracting those of the controls, respectively. Nitrous oxide emissions in the fertilized plots were approximately 0.08%-0.41% and 0.26%-0.34% of the applied fertilizer N over the maize and wheat seasons after subtracting those of the controls, correspondingly. The fertilizer N losses due to NH3 volatilization were markedly higher than those through denitrification and nitrous oxide emissions. These results indicated that NH3 volatilization was an important N transformation in the crop-soil system and was likely to be the major cause of low efficiencies with N fertilizer in the study area. Denitrification was not a very important pathway of N fertilizer loss, but did result in important evolution of the greenhouse gas N2O and the effect of N2O emitted from agricultural fields on environment should not be overlooked.

Using a zeolite medium biofilter to remove organic pollutant and ammonia simultaneously

A pilot scale zeolite medium biological aerated filter(ZBAF) was designed and used to treat municipal wastewater. It showed that ZBAF could simultaneously remove chemical oxygen demand(COD), ammonia-N and turbidity to satisfied degree at a hydraulic retention time(HRT) of 0.95 h. Their average removal efficiencies were 73.9%, 88.4% and 96.2% with the corresponding average effluent concentrations of 43.4 mg/L, 3.5 mg/L and 3.7 NTU, respectively. These effluent items met with the water quality standard of the treated water reused for cooling water. The COD removal volumetric loading rate increased proportionally with its applied volumetric loading rate with its maximum of 7.1 kg/(m 3·d). Ammonia-N removal loading rate also increased proportionally with its applied loading rate at HRT of longer than 0.95 h and the feasible maximum removal loading rate was 0.9 kg/(m 3·d). The COD loading rate did not affect the ammonia-N removal efficiency significantly when it was lower than 5.5 kg/(m 3·d). ZBAF has good application prospect for its low cost and high removal efficiency in the future.

Ammonia Volatilization from Urea Applied to Acid Paddy Soil in Southern China and Its Control

Results showed that ammonia loss from urea broadcast into floodwater and incorporated into soil at transplanting was as high as 40% of applied N,and the corresponding total nitrogen (N) loss was 56%.Ammonia loss was measured with simplified micrometeorological method (ammonia sampler),and total N loss was concurrently measured using ^15N balance technique.The experiment was conducted under strong sunshine conditions on acid paddy soil derived from Quaternary red clay.The ammonia loss in this particular condition was much greater than those obtained from previous studies when urea was also applied to acid paddy soil but under cloudy conditions.It is concluded that the strong sunshine conditions with high temperature and shallow floodwater during the period of present experiment favoured ammonia volatilization.Application of stearyl alcohol on the surface of the floodwater reduced ammonia loss to 23% of applied N.However,the effect of stearyl alcohol was short-lived,probably due to the microbiological decomposition.

Diel variation in metabolism and ammonia excretion of Marphysa sanguinea (Polychaeta: Eunicidae)

Polychaetes provide an excellent food resource for fi sh and represent the dominant zoobenthos in marine ecosystems. Diel variation in the rates of metabolism and ammonia-N excretion of Marphysa sanguinea were studied. The worms were grouped according to their wet body weight into small(S; 1.24±0.06 g), medium(M; 4.00±0.30 g), and large(L; 8.54±1.08 g) categories. Their weight-specifi c metabolic rates, based on aerobic respiration( R), were measured at 16°C(±0.2°C) and classed as either routine( R_R) or standard( R_S) rates. Both respiration types decreased with increasing body weight. Respiration was described by R = a W^b, where b was-0.400 9 and-0.532 0 for R_R and R_S, respectively. Diurnal changes in R_S for each group was relatively flat, with a slightly increasing trend with time, but was relatively stable as a whole. R_R of the diurnal variation of worms was higher than R_S, but both had similar overall trends. The peak values of specifi c dynamic action(SDA)( R_(SDA)) in the S, M, and L groups were 2.704, 1.149, and 0.682 mg/(g?h), respectively. The durations of SDA were 13, 6, and 6 h, respectively and the energy expenditures of SDA were 377.98, 117.34, and 74.94 J/g, respectively. These data indicate that the metabolic rates were higher in smaller individuals, which is advantageous for their rapid growth.

Rice yield, nitrogen utilization and ammonia volatilization as influenced by modified rice cultivation at varying nitrogen rates

Field experiments were conducted in 2006 to investigate the impacts of modified rice cultivation systems on: grain yield, N uptake, ammonia volatilization from rice soil and N use efficiency (ANUE, agronomic N use efficiency;and PFP, partial factor productivity of applied N). The trials compared rice production using modified methods of irrigation, planting, weeding and nutrient management (the system of rice intensification, SRI) with traditional flooding (TF). The effects of different N application rates (0, 80, 160, 240 kg ha-1) and of N rates interacting with cultivation methods were also evaluated. Grain yields ranged from 5.6 to 6.9 t ha-1 with SRI, and from 4.0 to 6.1 t ha-1 under TF management. On average, grain yields under SRI were 24% higher than that with TF. Ammonia volatilization was increased significantly under SRI compared with TF and the average total amount of ammonia volatilization loss during the rice growth stage under SRI was 22% higher than TF. With increases in application rate, N uptake by rice increased, and the ratio of N in the seed to total N in the plant decreased. Furthermore, results showed that higher ANUE was achieved at a relatively low N fertilizer rate (80 kg ha-1 N) with SRI. Results of these studies suggest that SRI increased rice yield and N uptake and improved ammonia volatilization loss from rice soil compared with TF. Moreover, there were significant interactions between N application rates and cultivation methods. We conclude that it was the most important to adjust the amount of N application under SRI, such as reducing the amount of N application. Research on effects of N fertilizer on rice yield and environmental pollution under SRI may be worth further studying.

氨煤混燃NO生成机理研究

以氨煤混燃为研究对象,研究了不同温度,不同掺氨比(氨气完全燃烧释放的热量在总热量中所占百分比)对NO生成特性的影响。研究结果表明:温度与掺氨比对NO体积分数有显著的影响,在温度为1000℃和1100℃工况下,氨气的加入会抑制NO的生成;随着温度的升高,氨燃烧性能增强,促进了燃料-N到NO生成,使得温度在1200℃时,NO生成量随着掺氨比的增加而增大;当温度进一步升高至1300℃以上时,未燃氨协同煤焦对NO的还原作用增强,表现为NO生成量随掺氨比的增加呈现先增加后降低的规律;温度在1200℃时,单位质量燃料的NO释放量随着掺氨比的增加而增加;在研究的其他温度区间中,单位质量燃料的NO释放量随着掺氨比的增加而减少;煤粉燃烧中掺入氨气会大幅度降低燃料-N到NO的转化率,不同温度和不同掺氨比对燃料-N到NO转化率的影响不同。

氨煤混燃过程中NH/煤焦/O_(2)异相体系N氧化的分子机理

为了实现双碳目标,降低煤电碳排放势在必行。无碳燃料氨与煤混烧被认为是降低火电碳排放的有效途径之一。而氨作为N源,增加了氨煤混燃NOx排放量升高的可能性,因此,深入研究氨煤混燃NO生成机理对实现氨煤混燃低碳低氮燃烧十分关键。采用量子化学方法探究了当NH3以NH形式存在时氨煤混燃N的氧化机理,并采用波函数分析NH和O_(2)在煤表面的吸附行为。计算结果表明,NH在C5表面吸附形成中间体IM1的过程为放热过程,放热量高达754.79 kJ/mol,且C原子为电子供体而失电子,NH为电子受体而得电子,促进C—N键键合。进一步探究O_(2)以不同方式吸附时NH/煤焦/O_(2)体系的反应机理,得出NH/煤焦/O_(2)共燃体系首先发生NH在煤焦表面的氧化,随后煤焦表面残余氧或体系中O_(2)将煤焦-N进一步氧化。NH/煤/O_(2)异相体系中NH通过不同反应路径生成氧化产物NO、NO_(2)和HNO,对应决速步能垒分别为120.67、323.37和193.50 kJ/mol,说明氨-N/煤-N生成NO的过程更易进行。动力学结果表明,各温度下生成NO的决速步速率明显高于NO_(2),且随着温度升高,生成NO的决速步速率与HNO的逐渐接近。NH氧化产物释放后,残留在煤焦表面氧进一步与C结合成CO释放,实现了共燃体系氨燃料中N和煤粉中C的氧化。随后煤焦-N与体系中O_(2)发生异相氧化,实现煤焦-N向NO的转化。在微观层面揭示了氨燃烧生成NO过程中重要过渡产物HNO形成的分子机理,明晰了另一氧化产物NO_(2)的生成路径,为发展氨煤的混合燃烧机理提供理论支撑和数据参考。

Nitrogen mobility,ammonia volatilization,and estimated leaching loss from long-term manure incorporation in red soil

Nitrogen（N） loss from fertilization in agricultural fields has an unavoidable negative impact on the environment and a better understanding of the major pathways can assist in developing the best management practices. The aim of this study was to evaluate the fate of N fertilizers applied to acidic red soil（Ferralic Cambisol） after 19 years of mineral（synthetic） and manure fertilizer treatments under a cropping system with wheat-maize rotations. Five field treatments were examined： control（CK）, chemical nitrogen and potash fertilizer（NK）, chemical nitrogen and phosphorus fertilizer（NP）, chemical nitrogen, phosphorus and potash fertilizer（NPK） and the NPK with manure（NPKM, 70% N from manure）. Based on the soil total N storage change in 0–100 cm depth, ammonia（NH_3） volatilization, nitrous oxide（N_2O） emission, N plant uptake, and the potential N leaching loss were estimated using a mass balance approach. In contrast to the NPKM, all mineral fertilizer treatments（NK, NP and NPK） showed increased nitrate（NO_3~–） concentration with increasing soil depth, indicating higher leaching potential. However, total NH_3 volatilization loss was much higher in the NPKM（19.7%） than other mineral fertilizer treatments（≤4.2%）. The N_2O emissions were generally low（0.2–0.9%, the highest from the NPKM）. Total gaseous loss accounted for 1.7, 3.3, 5.1, and 21.9% for NK, NP, NPK, and NPKM treatments, respectively. Estimated N leaching loss from the NPKM was only about 5% of the losses from mineral fertilizer treatments. All data demonstrated that manure incorporation improved soil productivity, increased yield, and reduced potential leaching, but with significantly higher NH_3 volatilization, which could be reduced by improving the application method. This study confirms that manure incorporationis an essential strategy in N fertilization management in upland red soil cropping system.

A Review:Toxicity of Ammonia-N to Fish and Detoxification Strategy of Fish

In natural water, the content of ammonia nitrogen is always kept at a low level. However, the ammonia nitrogen content in water will be elevated or even excessive when the density of aquaculture is too large or exogenous ammonia are discharged into the water, causing a series of ad-verse effects on fish survival. Within a certain range, fishes reduce ammonia production in vivo by converting ammonia into glutamine and urea, and increase NH3 volatilization and NH4+emissions to ease ammonia toxicity, but the ability to alleviate ammonia poisoning vary with fish species and size. The ammonia nitrogen sources, existence form, factors affecting toxicity, toxic mechanism and detoxification strategy of fish are reviewed, in or-der to provide reference for improving the ability of fish to alleviate ammonia nitrogen toxicity and healthy farming.

Effect of Ammonia-Nitrogen Stress on Non-specific Immunity of Hybrid Tilapia(Oreochromis niloticus× Oreochromis areus)

The juveniles of hybrid tilapia （ Oreochromis niloticus x Oreochromis areus） were exposed to ananonia-nitrogen （N） （0, 2.5, 5, 10 and 20 mg/L） for 0, 12, 24, 48 and 72 h to evaluate the effect of ammonia-N stress on their non-specific immunity. Results show that the activity of serum lysozyme decreased signifi- candy with extension of stress time （P 〈 0.05）. The total antioxidant capacity （T-AOC） and activity of antioxidase in liver were significantly affected. The activi- ty of T-AOC and total superoxide dismutase （T-SOD） of fish exposed to ammonia-N were initially decreasing then increasing （ P 〈 0.05 ）. Activities of catalase （CAT） and glutathione peroxidase （GSH-Px） were correlated with concentrations of ammonia-N. Fish exposed to lower concentrations （2.5 mg/L or 5 mg/L） showed decreased CAT activity within 24 h （P 〈 0.05 ）, while those exposed to higher concentrations （10 mg/L or 20 mg/L） initially showed increased then decreased activity of CAT. Except for the highest concentration groups, fish exposed to ammonia-N showed inductive activity of GSH-Px （ P 〈 0.05 ）. Under the ex- perimental conditions, non-specific immunity of tilapia was affected by ammonia-N stress, and the impact was increased with increased concentration and extension of time.

基于HCO_(3)^(-)/N控制部分亚硝化及影响因素

部分亚硝化的稳定控制是基于厌氧氨氧化的两段式自养脱氮高效运行的关键。在好氧条件下(DO>1 mg/L),通过控制HCO_(3)^(-)与NH^(4+)的摩尔比,在SBR系统实现了高氨废水部分亚硝化的启动与长期稳定运行,出水NO_(2)^(-)-N/NH^(4+)-N为1.09±0.08。在此基础上,通过批式试验考察了HCO_(3)^(-)/N及pH对部分亚硝化的影响。结果发现,随着进水HCO_(3)^(-)/N由0.5∶1升高为1∶1,1.5∶1和2∶1,氨氮转化率由33.62%增加至57.41%,100%和100%。在控制HCO_(3)^(-)/N为1∶1前提下,随着pH由7升至8和9时,氨氮转化率由56.89%升高至61.32%和100%,平均氨氧化速率分别达0.39,0.42,0.49 mg N/(g MLSS·min)。结果表明,HCO_(3)^(-)/N和pH通过影响游离氨和游离亚硝酸的浓度同步影响着氨氧化速率、转化率和亚硝酸盐氧化,HCO_(3)^(-)/N为1∶1及pH=8是实现高氨废水部分亚硝化稳定运行的重要参数。