新疆盐渍化土壤氮肥氨挥发损失特征初步研究

在室温下应用“静态吸收法”,研究不同盐渍化程度的盐化土壤和碱化土壤上氮肥氨挥发损失特征。结果表明:(1)除碱土外碱化土壤上氮肥氨挥发量随时间延长呈现下降趋势,在盐化土壤上氨挥发量随时间呈现先上升后下降趋势。(2)供试9个典型盐渍化土壤样品上氮肥氨挥发量(Y)与时间(t)关系均符合Y=at2 bt c动力学方程,相关性呈极显著水平。(3)氨挥发总量(Y)、氨挥发速率(Yi)与土壤含盐量(x)呈极显著正相关;氨挥发持续时间随着盐渍化程度的增加而延长。(4)氨挥发总量、挥发速率与盐渍土pH相关性未达到显著水平;盐渍土上pH值对氨挥发的影响需要进一步研究。以上结果表明,盐渍化耕作土壤上氮肥氨挥发的控制要依据盐渍化类型的不同而制定相应的措施。     

人工湿地脱氮途径及其影响因素分析

简述了人工湿地脱氮模型。各种形态的氮在人工湿地系统中可以通过氨的挥发、植物吸收、介质沉淀吸附以及微生物硝化/反硝化作用等过程被去除。讨论了各脱氮途径对人工湿地脱氮的贡献,在大多数人工湿地的pH条件下,湿地地面氨挥发可以忽略,湿地植物叶片氨挥发量尚不清楚。湿地介质的直接吸附是短期的。植物在湿地脱氮过程中起了重要作用,但一般认为植物直接吸收和存储只占湿地脱氮的一小部分,一般低于30%。微生物的硝化/反硝化作用,是人工湿地脱氮的最主要的形式。讨论了影响人工湿地硝化作用的主要因素:溶解氧,pH和温度。大多数人工湿地的pH适合硝化作用,溶解氧和温度对湿地硝化作用的影响最大。温度不仅影响微生物的硝化作用,而且可以间接地影响植物的生长从而影响人工湿地的脱氮性能。     

膜接触器从混合气中脱氨性能的研究

采用中空纤维膜接触器进行了从模拟“铜洗再生气”中脱氨的研究,探讨了影响脱除效率的主要因素．试验表明:膜吸收法对混合气中的氨有很好的脱除效果,当混合气中氨的浓度为２０．０ｇ·Ｎｍ－３,膜组件的处理能力为５．１Ｎｎ３·ｍ－２·ｈ－１时,脱氨率大于９９．９%,即脱氨后氨的浓度低于０．０２ｇ·Ｎｍ－３．当组件内吸收液供应充足时,分离过程的传质阻力主要在膜和气体一侧．研究发现,当用挥发性水溶液(盐酸)作为吸收剂时,由于ＮＨ４Ｃｌ晶体的桥联作用导致疏水性微孔膜亲水化．     

石灰预处理对树叶堆肥过程中养分转化的影响

以树叶干质量的0%、1.00%、2.50%和4.00%的石灰预处理树叶,24h后分别将预处理后的树叶与鸡粪联合堆肥,研究不同用量石灰预处理树叶对树叶堆肥过程中养分转化的影响。试验在自制的堆肥反应器内进行,采用间歇式强制通风的方式,进行为期59d的堆肥试验。结果表明:石灰预处理树叶24h可以有效的降低树叶中的有机质质量分数,以4.00%的石灰预处理的树叶其有机质降幅达6.00%;石灰预处理24h后,各处理pH相差不大;EC的变化与pH相似;预处理前后,各处理总氮、总磷和总钾的质量分数相差不大。用石灰预处理后的树叶堆肥有利于堆肥有机质的降解,尤以2.50%石灰预处理的效果最好;有利于堆肥w(C)/w(N)的降低,其降低幅度与石灰用量成正比;有利于减少堆肥过程中氮素的损失,且氮素损失与石灰使用量呈反比;有利于堆肥NH4 -N质量分数的降低;提高堆肥终产品NO3--N的质量分数,其质量分数与石灰用量呈正比;有利于堆肥中钾的浓缩;对堆肥的pH、EC、w(NH4 -N)/w(NO3--N)和总磷的影响不大。综合考虑试验结果后认为,以4.00%石灰预处理的效果最为理想。     

Removing ammonia from air with a constant pH,slightly acidic water spray wet scrubber using recycled scrubbing solution

Slightly acidic solutions are a practical means of removing ammonia from air Scrubbed NH₃ accumulates in solution as NH₄⁺ and should be an excellent fertilizer Increased air velocity decreased NH₃ removal and increased NH₄⁺ collection Previous research on wet scrubbers has only studied highly acidic scrubbing solutions because of their high ammonia capture efficiencies; however, the high acidity created practical problems. Lower acidity solutions would reduce corrosion, maintenance, and cost; however, designers may need to use strategies for increasing scrubber effectiveness, such as using lower air velocities. The objective of this study was to determine if a spray scrubber with slightly acidic and higher pH scrubbing solution (pH from 2 to 8) could effectively remove NH₃ from NH₃ laden air (such as animal building exhaust air), and also collect this valuable resource for later use as a fertilizer. A bench-scale spray wet scrubber treated 20 ppmv NH₃/air mixture in a countercurrent contact chamber. First, the solution pH was varied from 2 to 8 while maintaining constant air velocity at 1.3 m·s⁻¹. Next, air velocity was increased (2 and 3 m·s⁻¹) while solution pH remained constant at pH6. At 1.3 m·s⁻¹, NH₃ removal efficiencies ranged between 49.0% (pH8) and 84.3% (pH2). This study has shown that slightly acidic scrubbing solutions are a practical means of removing ammonia from air especially if the scrubber is designed to increase collisions between solution droplets and NH₃ molecules. The NH₃ removed from the air was held in solution as NH₄⁺ and accumulates over time so the solution should be an excellent fertilizer.     

The toxicity of ammonia,nitrite and nitrate to the fish,Catla catla (Hamilton)

The acute toxicity of unionized ammonia; nitrite and nitrate to the Indian major carp Catla catla (Hamilton) was determined using static and continuous flow through systems for 24 hours. The median lethal concentration (LC50) values for 24 h of ammonia (NH3-N), nitrite (NO2-N) and nitrate (NO3-N) were 0.045 mg/l, 120.84 mg/l and 1565.43 mg/l in static test respectively and were 0.036 mg/l, 117.43 mg/l and 1484.08 mg/l in continuous flow through test respectively.     

聚丙烯中空纤维膜结构与氨水分离性能的研究

本文研究了聚丙烯中空纤维膜成型的工艺条件与结构性能的关系，并利用聚丙烯中空纤维膜组件进行了氨／水分离和影响分离效果的各种因素的研究。结果表明：在制膜工艺中，聚丙烯分子链在应力场下的结晶过程对后续的轴向拉伸形成微孔结构是非常重要的；伸长率为１６０％时的聚丙烯中空纤维膜，具有最大的孔隙率、平均孔径和透气率；其组件在氨／水分离中具有较好的分离效果，脱氨率可达９９％以上。进一步对氨／水分离的研究表明：分离     

Ammonia modeling for assessing potential toxicity to fish species in the Rio Grande, 1989-2002.

Increasing volumes of treated and untreated human sewage discharged into rivers around the world are likely to be leading to high aquatic concentrations of toxic, unionized ammonia (NH3), with negative impacts on species and ecosystems. Tools and approaches are needed for assessing the dynamics of NH3. This paper describes a modeling approach for first-order assessment of potential NH3 toxicity in urban rivers. In this study daily dissolved NH3 concentrations in the Rio Grande of central New Mexico, USA, at the city of Albuquerque's treated sewage outfall were modeled for 1989-2002. Data for ammonium (NH4+) concentrations in the sewage and data for discharge, temperature, and pH for both sewage effluent and the river were used. We used State of New Mexico acute and chronic NH3- N concentration values (0.30 and 0.05 mg/L NH3-N, respectively) and other reported standards as benchmarks for determining NH3 toxicity in the river and for assessing potential impact on population dynamics for fish species. A critical species of concern is the Rio Grande silvery minnow (Hybognathus amarus), an endangered species in the river near Albuquerque. Results show that NH3 concentrations matched or exceeded acute levels 13%, 3%, and 4% of the time in 1989, 1991, and 1992, respectively. Modeled NH3 concentrations matched or exceeded chronic values 97%, 74%, 78%, and 11% of the time in 1989, 1991, 1992, and 1997, respectively. Exceedences ranged from 0% to 1% in later years after enhancements to the wastewater treatment plant. Modeled NH3 concentrations may differ from actual concentrations because of NH3 and NH4+ loss terms and additive terms such as mixing processes, volatilization, nitrification, sorbtion, and NH4+ uptake. We conclude that NH3 toxicity must be considered seriously for its potential ecological impacts on the Rio Grande and as a mechanism contributing to the decline of the Rio Grande fish community in general and the Rio Grande silvery minnow specifically. Conclusions drawn for the Rio Grande suggest that NH3 concentrations may be high in rivers around the world where alkaline pH values are prevalent and sewage treatment capabilities are poorly developed or absent.     

N fertilization effects on denitrification and N cycling in an aggrading forest.

We investigated N cycling and denitrification rates following five years of N and dolomite amendments to whole-tree harvested forest plots at the long-term soil productivity experiment in the Fernow Experimental Forest in West Virginia, USA. We hypothesized that changes in soil chemistry and nutrient cycling induced by N fertilization would increase denitrification rates and the N2O:N2 ratio. Soils from the fertilized plots had a lower pH (2.96) than control plots (3.22) and plots that received fertilizer and dolomite (3.41). There were no significant differences in soil %C or %N between treatments. Chloroform-labile microbial biomass carbon was lower in fertilized plots compared to control plots, though this trend was not significant. Extractable soil NO3- was elevated in fertilized plots on each sample date. Soil-extractable NH4+, NO3-, pH, microbial biomass carbon, and %C varied significantly by sample date suggesting important seasonal patterns in soil chemistry and N cycling. In particular, the steep decline in extractable NH4+ during the growing season is consistent with the high N demands of a regenerating forest. Net N mineralization and nitrification also varied by date but were not affected by the fertilization and dolomite treatments. In a laboratory experiment, denitrification was stimulated by NO3- additions in soils collected from all field plots, but this effect was stronger in soils from the unfertilized control plots, suggesting that chronic N fertilization has partially alleviated a NO3- limitation on denitrification rates. Dextrose stimulated denitrification only in the whole-tree-harvest soils. Denitrification enzyme activity varied by sample date and was elevated in fertilized plots for soil collected in July 2000 and June 2001. There were no detectable treatment effects on N2O or N2 flux from soils under anaerobic conditions, though there was strong temporal variation. These results suggest that whole-tree harvesting has altered the N status of these soils so they are less prone to N saturation than more mature forests. It is likely that N losses associated with the initial harvest and high N demand by aggrading vegetation is minimizing, at least temporarily, the amount of inorganic N available for nitrification and denitrification, even in the fertilized plots in this experiment.     

Acid–base regulation in the Dungeness crab (Metacarcinus magister)

Homeostatic regulation allows organisms to secure basic physiological processes in a varying environment. To counteract fluctuations in ambient carbonate system speciation due to elevated seawater pCO₂ (hypercapnia), many aquatic crustaceans excrete/accumulate acid–base equivalents through their gills; however, not much is known about the role of ammonia in this response. The present study investigated the effects of hypercapnia on acid–base and ammonia regulation in the Dungeness crab, Metacarcinus magister on the whole animal and isolated gill levels. Hemolymph pCO₂ and [HCO₃ ^?] increased in M. magister acclimated to elevated pCO₂ (330 Pa), while pH remained stable. Additionally, hemolymph [Na⁺], [Ca²⁺], and [SO₄ ^2?] were significantly increased. When challenged with varying pH during gill perfusion, the pH of the artificial hemolymph remained relatively unchanged. Overall, ammonia production and excretion, as well as oxygen consumption, were reduced in crabs acclimated to elevated pCO₂, demonstrating that either (amino acid) oxidation is reduced in response to this particular stress, or nitrogenous wastes are excreted in an alternative form.     

鸟粪石法沉淀去除氨氮的平衡体系模拟预测

使用化学平衡软件Visual MINTEQ计算拟合鸟粪石(磷酸镁铵,MgNH4PO4·6H2O,MAP)沉淀去除氨氮的平衡体系在不同pH值条件下Mg2+、NH4+和PO34-各组分的变化及饱和指数(SI)的变化.实验和预测结果表明,模型对MAP沉淀平衡体系拟合良好.在本研究的pH值范围内(8.0—11.0),化学平衡模型VisualMINTEQ能预测敞开体系氨氮废水中通过磷酸铵镁沉淀去除的NH4+-N,但不能用来预测敞开体系中所有氨氮的去除,即预测结果中不包括由于氨气挥发而去除的氨氮.     

氧化亚铁硫杆菌浸出废旧锂离子电池的工艺条件

考察了接种量、振荡条件、浸出液以及电池原料对氧化亚铁硫杆菌浸出废旧锂离子电池的影响.研究结果表明,浸出10 d,钴浸出率达到48.5%,之后,浸出率不再增加;当接种量在2.5%—12.5%之间时,钴浸出率在第10天都为47.6%,接种量对浸出率无影响;振荡过程中控制温度为35℃时,钴浸出率最佳,并随着振荡速率的升高而增加;浸出液中加入硫磺对浸出影响不大,初始pH值在1.5—2.5范围内,都适合钴酸锂的浸出,而初始亚铁离子浓度在45 g.L-1条件下浸出效果最好;选择固液比为3%最佳,并且钴酸锂粉末的粒度大小对浸出率无影响.     

喷氨同时脱除NO和N_2O过程的化学动力学模拟

本文采用化学动力学模拟的方法,对广泛应用于燃煤锅炉的喷氨脱硝技术进行了研究,首次发现在燃煤锅炉的烟气中喷入氨气不仅可以降低NO_x的排放量.而且可以同时降低N_2O的排放量.文中还就喷氨初期的烟气温度、烟气中的含氧量和水份、NO和N_2O的初始浓度、烟气中的CO含量以及喷氨量对喷氨同时脱除NO和N_2O效果的影响进行了计算分析,确定了喷氨同时脱除NO和N_2O的最佳条件.对喷氨过程的化学反应机理进行的分析表明,该过程之所以能同时脱除NO和N_2O,是因为在NH_3的分解和NO的还原过程中产生了一定浓度的H和OH离子,从而加速了N_2O的热分解过程.     

不同硝/铵比值对小麦幼苗根系释放氢氧根的影响

为研发酸化土壤的生物修复技术,采用水培试验和自动电位滴定装置研究酸性条件下氮素形态对小麦幼苗根系释放氢氧根及培养液pH变化的影响。结果表明,小麦幼苗在初始pH值为4.0,n(NO3-)∶n(NH4+)比值(以下简称硝/铵比)分别为15∶1、3∶1和1∶1的营养液中培养6 d后营养液pH升高,且增幅随硝/铵比的增加而增大,小麦对硝态氮的吸收量和氢氧根释放量呈相同的变化趋势,说明小麦对硝态氮的吸收偏好导致根系释放氢氧根,进而使得培养液pH升高。小麦幼苗在硝/铵比为3∶1,初始pH值分别为4.0、4.5和5.0的营养液中培养6d后,培养液pH和氢氧根释放量的增幅随初始pH的升高而降低,说明低pH条件有利于小麦幼苗对硝态氮的吸收,可促进小麦根系释放更多的氢氧根。10 h的恒定pH试验结果表明,恒定pH条件下小麦根系释放的氢氧根数量大于非恒定pH条件,且硝态氮比例越大,差值越大。因此,可以根据小麦在酸性条件下对硝态氮的吸收偏好建立酸化土壤的生物修复方法,即调节硝态氮含量以加大小麦根系的氢氧根释放量,进而提高土壤pH。     

利用根箱法解析甜椒根际土壤中氮的行为(英文)

为研究甜椒根际土壤中氮的行为,与既报同样的方法进行研究,即,利用15NH4+,15NO3-双标记的硝胺(NH,4>15NO3,15NH4NO3),在温室里对甜椒进行6周的根箱栽培.收割后,对土壤全氮,NO3-N,水溶性NH4-N,KCl抽出NH4-N和其各自的15N atom%进行测定.结果表明,土壤全氮从非根际到根际逐渐增加,与栽培前相比,土壤全氮在非根际中减少,却在根际中增大.土壤NO3-N浓度朝根际增加到离根际2 mm处,然后激减到根际.NO3-N的来自施给NO3-N的比例靠近根际逐渐升高,在根际达到了69%,反而,来自施给NH4-N的比例靠近根际逐渐降低,在根际将至7%左右.水溶性NH4-N和KCl抽出NH4-N浓度靠近根际逐渐降低,而且,从非根际到根际,二者匀保持3∶10的比例.KCl抽出NH4-N的来自施给NO3-N的比例靠近根际逐渐升高,但在根际仍低于3%,反而,其来自施给NH4-N的比例在非根际约为47%～55%,在根际降到41%.在整个根箱里,施用NO3-N的有機率达到62%,但其值在根际比非根圈要低.相反,施用NH4-N的有機率仅11%左右,但其值在根际比非根际要高.以上结果表明,在甜椒根际土壤中氮的无机化-有机化活性与水稻相比显著低.     

不同减量施肥条件下稻田田面水氮素动态变化及径流损失研究

采用过量施用化肥获得高产已成为近年来太湖地区的普遍现象,而由此引发的农业面源污染对水体生态环境恶化的贡献值也越来越大。通过对苕溪流域地区的田间试验,研究了8种不同减量施肥处理条件下,稻田田面水中氮素的动态变化特征和径流损失量,研究结果表明,（1）各处理铵氮浓度在施肥后迅速上升,1～3d达到最大值,而总氮在施肥后第1天便达到峰值,之后随时间变化逐渐下降,铵氮、总氮浓度在一周之后均降至较低水平。（2）田面水中铵氮／总氮比在施肥后3～7d达到峰值,之后逐渐下降。（3）田间任何1次的径流排水均会造成田面水氮素的流失,径流排水发生的时间与施肥时间间隔越小氮素的流失负荷就越大。（4）各减量化施肥处理年度累计流失负荷较常规施肥处理下降6％～53％,当季稻田氮素流失率在1．4％～2．6％之间。为减少农田氮肥使用量,降低氮素流失量,减缓农业面源污染提供理论依据。     

炼焦污水零排放技术初探

本文介绍了炼焦污水零排小试结果,试验中采用新型大孔吸附树脂脱酚,蒸汽汽提脱氨,处理后的污水用作熄焦补充水.试验证明该零排放方案是可行的.     

施用尿素和硫酸铵对红壤硝化和酸化作用的影响

通过室内恒温培养试验,研究施用CO(NH2)2和(NH4)2SO4对初始pH值分别为5.14、4.77和4.34的红壤酸化速率和硝化速率的影响。结果表明,施用CO(NH2)2显著增加了3种红壤的硝化速率,从而显著加速土壤酸化。培养结束时,3种红壤pH值较培养过程中最高值分别下降2.14、1.23和0.56。施用(NH4)2SO4抑制了初始pH<5.0的2种红壤的硝化作用,从而显著降低这2种红壤的硝化速率和酸化速率,但显著增加了初始pH>5.0红壤的硝化速率,对其酸化速率则未见显著影响。3种红壤的酸化速率与硝化速率间存在显著线性相关关系。硝化作用是导致农田红壤pH值下降的主要原因之一,但不同氮肥对红壤硝化速率和酸化速率的影响不同。     

生态沟渠净化稻田排水动力学分析和生物相特征

本研究以太湖流域常见的菱角、水葫芦、梭鱼草、圆币草等水生植物和人工水草、塑料立体弹性填料为生态强化载体,构建"水生植物-载体生物膜-菌藻"复合型生态系统,研究了稻田排水中的氮、磷等营养元素的去除特性,构建氮、磷污染物的降解动力学模型,并调查了沟渠内"微生物-藻类"生物相特征.结果表明,生态沟渠运行期间,随着水稻进入不同...     

Ammonia as confounding factor in toxicity tests with the sea urchin Paracentrotus lividus (Lmk)

The aim of this study was to investigate the toxicity of total ammonia towards sea urchin bioassays, in order to elucidate the role of ammonia as confounding factor in sediment quality assessment studies. New toxicity data, expressed as EC50, NOEC and LOEC are reported for Paracentrotus lividus based on experiments at differing pH values. Results confirmed that sperm cell toxicity test is not very sensitive to ammonia, while total ammonia embryotoxicity is strictly pH dependent. Accurate observations of embryotoxic effects at increasing total ammonia concentrations evidenced progressive shifts from malformed plutei to gastrula and blastula blockages. Toxicity data obtained for P. lividus are comparable with previous results with other echinoid species.