“New” DDT inputs to North America: Atmospheric deposition

Measurement of untransformed (p,p'- and o,p'-) DDT in rain, snow, and peat indicates that input of “new” DDT continues over a large portion of eastern North America. Peat cores obtained from ombrotrophic bogs indicate that current atmospherically derived fluxes are about 10–20% of those which occurred during peak DDT usage (～1960). Since DDT has been banned in North America and considering the magnitude of present fluxes, these residues must result from atmospheric transboundary transport. It is suggested that “new” DDT is being transported from neighboring areas where current use is substantial, Mexico and Central America.     

Soil functional responses to excess nitrogen inputs at global scale

There is little evidence that nitrogen (N) cycling in the highly weathered, low-phosphorus (P), acidic soils found in Southern Hemisphere continents will differ greatly from that in North America and Europe. Evidence from the 'south' shows: the similarity in forms and temporal patterns in losses of N from different land uses; that the C:N ratios of the forest floor/litter layer from different continents are strongly predictive of a range of processes on a global scale; that generalizations based on Northern Hemisphere experience of the impact of N additions to 'P-limited' ecosystems are likely to fail for southern ecosystems where anatomical and physiological adaptation of native plants to low-P soils makes questionable the concept of 'P-limitation'; that the greatest threats in the 'south' are probably changes in land use that may greatly increase N inputs and turnover; that localized increases in N inputs produce similar effects to those seen in the 'north'.     

Atmospheric deposition of metallic pollutants over the Ligurian Sea: labile and residual inputs

Atmospheric fluxes of six trace metals (Cd, Cr, Cu, Ni, Pb and Zn) with Al as a crustal reference were measured at Cap Ferrat (French Riviera) between February 1997 and July 1998. An original sampling protocol enabled the separation of labile (seawater at pH 2) and residual fractions in the total atmospheric input. Median acid-labile fractions were 91%, 69%, 83%, 84%, 97% and 98% of the total for Cd, Cr, Cu, Ni, Pb and Zn, respectively. Under the conditions used, lability of individual metals is related to the anthropogenic component of the samples. Enrichment factors and anthropogenic fraction are estimated for each metal. Some interannual changes are investigated (Pb, Zn). The observed increase of Zn inputs may be linked to local input from the Nice district waste plant (commissioned in 1988), 6.5 km away.     

Riverine inputs of organic carbon and nitrogen to Norwegian coastal areas

The transport of organic and inorganic material in 10 Norwegian rivers has been monitored from 1990 to 1998. The suspended material in the rivers consisted of 40-80% organic materials. A major part of this was DOC with a C/ N mole ratio > 25. The C/N ratio of the organic material increases with increasing river flow when drained from forest-dominated catchments, in contrast to mountain dominated catchments where variation in runoff does not influence the C/N ratio. Laboratory experiments showed that more than 90% of the DOC remained in solution when salinity increased to 30. The flocculated and settled material contained less than 5% organic material with a C/N ratio of 6.7-12.4, comparable to C/N ratios in cultivated soils and coastal marine sediments. This confirms that only a minor amount of organic material carried to the sea by rivers settles in the coastal zone.     

吹脱法去除垃圾渗滤液中的氨氮研究

对吹脱法去除垃圾渗滤液中的氨氮进行了研究 ,控制吹脱效率高低的关键因素是温度、气液比和 pH值。在水温大于 2 5℃ ,气液比控制在 35 0 0左右 ,渗滤液 pH值控制在 1 0 5左右 ,对于氨氮浓度高达 2 0 0 0～ 4 0 0 0mg/L的垃圾渗滤液 ,去除率可达到 90 %以上     

MAP热分解产物的氨氮吸附性能研究

以TG-DTA、XRD、SEM等手段研究了MAP的热分解行为,并对热分解产物的氨氮吸附性能进行了研究。结果表明,热分解MAP可将水和氨释放出来,热分解产物粒径变小,结晶度降低,其XRD图谱主要出现MgHPO₄·3H₂O的特征衍射峰,但在吸附氨氮后,则主要出现MgNH₄PO₄·6H₂O的特征衍射峰;控制MAP在100℃条件下热分解3 h再用于氨氮的处理药剂是合适的,氨氮吸附反应体系的pH值以10较为适宜,在此条件下反应40 min对氨氮的去除率即达90%。     

改性天然沸石去除水中氨氮的研究

分别采用NaCl、KCl和CaCl2对黑龙江省某市天然沸石进行改性,考察了pH值、氨氮初始浓度以及温度对改性沸石交换性能的影响,并对改性沸石的交换动力学进行了研究.结果表明,NaCl和KCl改性对沸石原矿交换容量有不同程度提高,而KCl改性后容量有所降低.pH、NH4 初始浓度以及温度对交换性能有明显影响,pH 6.0附近沸石交换容量最大;NH4 初始浓度越高,反应速度越快,相同初始浓度下,钾型沸石交换速度较快,而沸石原矿交换速度最慢.采用Langmuir型离子交换等温线进行非线性回归的结果显示,低温有利于交换反应的进行.溶液中NH4 在改性沸石上的离子交换反应可采用Vermeulen模型描述,沸石原矿拟合相关系数较差.改性沸石多次再生后,其交换容量均有所降低.     

改性天然沸石去除水中氨氮的研究

分别采用NaCl、KCl和CaCl2对黑龙江省某市天然沸石进行改性，考察了pH值、氨氮初始浓度以及温度对改性沸石交换性能的影响，并对改性沸石的交换动力学进行了研究。结果表明，NaCl和KCl改性对沸石原矿交换容量有不同程度提高，而KCl改性后容量有所降低。pH、NH4初始浓度以及温度对交换性能有明显影响，pH6．0附近沸石交换容量最大；NH4初始浓度越高，反应速度越快，相同初始浓度下，钾型沸石交换速度较快，而沸石原矿交换速度最慢。采用Langmuir型离子交换等温线进行非线性回归的结果显示，低温有利于交换反应的进行。溶液中NH4^＋在改性沸石上的离子交换反应可采用Vermeulen模型描述，沸石原矿拟合相关系数较差。改性沸石多次再生后，其交换容量均有所降低。     

Ecosystem responses to reduced and oxidised nitrogen inputs in European terrestrial habitats

While it is well established that ecosystems display strong responses to elevated nitrogen deposition, the importance of the ratio between the dominant forms of deposited nitrogen (NH_x and NO_y) in determining ecosystem response is poorly understood. As large changes in the ratio of oxidised and reduced nitrogen inputs are occurring, this oversight requires attention. One reason for this knowledge gap is that plants experience a different NH_x:NO_y ratio in soil to that seen in atmospheric deposits because atmospheric inputs are modified by soil transformations, mediated by soil pH. Consequently species of neutral and alkaline habitats are less likely to encounter high NH₄⁺ concentrations than species from acid soils. We suggest that the response of vascular plant species to changing ratios of NH_x:NO_y deposits will be driven primarily by a combination of soil pH and nitrification rates. Testing this hypothesis requires a combination of experimental and survey work in a range of systems.     

Concentrations of ammonia and nitrogen dioxide at roadside verges, and their contribution to nitrogen deposition

Bimonthly integrated measurements of NO2 and NH3 have been made over one year at distances up to 10 m away from the edges of roads across Scotland, using a stratified sampling scheme in terms of road traffic density and background N deposition. The rate of decrease in gas concentrations away from the edge of the roads was rapid, with concentrations falling by 90% within the first 10 m for NH3 and the first 15 m for NO2. The longer transport distance for NO2 reflects the production of secondary NO2 from reaction of emitted NO and O3. Concentrations above the background, estimated at the edge of the traffic lane, were linearly proportional to traffic density for NH3 (microg NH3 m(-3) = 1 x 10(-4) x numbers of cars per day), reflecting emissions from three-way catalysts. For NO2, where emissions depend strongly on vehicle type and fuel, traffic density was calculated in terms of 'car equivalents'; NO2 concentrations at the edge of the traffic lane were proportional to the number of car equivalents (microg NO2 m(-3) = 1 x 10(-4) x numbers of car equivalents per day). Although absolute concentrations (microg m(-3)) of NH3 were five times smaller than for NO2, the greater deposition velocity for NH3 to vegetation means that approximately equivalent amounts of dry N deposition to road side vegetation from vehicle emissions comes from NH3 and NO2. Depending on traffic density, the additional N deposition attributable to vehicle exhaust gases is between 1 and 15 kg N ha(-1) y(-1) at the edge of the vehicle lane, falling to 0.2-10 kg N ha(-1) y(-1) at 10 m from the edge of the road.     

Atmospheric nitrogen deposition: revisiting the question of the importance of the organic component

The organic component of atmospheric reactive nitrogen plays a role in biogeochemical cycles, climate and ecosystems. Although its deposition has long been known to be quantitatively significant, it is not routinely assessed in deposition studies and monitoring programmes. Excluding this fraction, typically 25-35%, introduces significant uncertainty in the determination of nitrogen deposition, with implications for the critical loads approach. The last decade of rainwater studies substantially expands the worldwide dataset, giving enough global coverage for specific hypotheses to be considered about the distribution, composition, sources and effects of organic-nitrogen deposition. This data collation and meta-analysis highlights knowledge gaps, suggesting where data-gathering efforts and process studies should be focused. New analytical techniques allow long-standing conjectures about the nature and sources of organic N to be investigated, with tantalising indications of the interplay between natural and anthropogenic sources, and between the nitrogen and carbon cycles.     

Atmospheric dynamics and ozone cycles related to nitrogen deposition in the western Mediterranean

Recent results from EU-sponsored projects have shed new light on the workings of the atmosphere in the Mediterranean Basin, where a large airmass becomes trapped and nearly stagnant over the sea during the summer. This work reviews the developments which have led to our present understanding of air pollution dynamics and associated meteorological processes in this region. In summer, the sea breezes combine with upslope winds to create recirculations along the coasts and within the western Mediterranean basin, with residence times in the order of days. Under strong insolation these recirculations become "large natural photo-chemical reactors" where most of the NOx emissions and other precursors are transformed into oxidants, acidic compounds, aerosols and ozone, which can exceed European Union directives for several months of the year. The objective of this paper is to evaluate available experimental evidence and complementary modelling results to help in the interpretation of observed ozone cycles and to anticipate possible scenarios for anthropogenic nitrogen deposition in the region.     

黄河兰州段悬移质泥沙对氨氮的吸附特性

实验研究了黄河兰州段不同粒径的悬浮泥沙对氨氮的吸附行为,拟阐释黄河兰州段水质自净的机制。通过分析探讨了含沙量、氨氮初始浓度、泥沙粒径和化学成分对氨氮吸附过程的影响。结果表明,准二级动力学方程和Langmuir模型能够较好地描述黄河兰州段不同粒径泥沙的吸附动力学和等温吸附过程(R20.9);含沙量对泥沙吸附氨氮作用具有显著影响,且氨氮吸附量和平衡时间与含沙量呈明显负相关性;氨氮初始浓度与氨氮吸附量及平衡时间呈正相关性;同时,泥沙颗粒越细,吸附氨氮的能力越强,吸附容量越大,反应的自发程度越高。此外,泥沙有机质、Fe2O3、Al2O3和MgO的含量随粒径减小而增大,它们对单位质量泥沙最大吸附量(Sm)具有正效应。泥沙的吸附在黄河兰州段水质自净过程中起着一定的促进作用。     

凹凸棒土的氨氮吸附性能研究

在以氨氮去除率为指标,在振荡时间60 min,振荡温度25℃,振荡速度140r/min的条件下发现凹凸棒土的最佳投加量2.5 g;添加凹凸棒土可以加强SBR生物系统去除氨氮的能力;拟合凹凸棒土吸附氨氮的等温线方程符合Freundlich吸附模型.     

超声波吹脱技术处理高浓度氨氮废水试验研究

采用超声波吹脱技术对高浓度NH3 N废水进行了处理试验。试验结果表明 ,废水采用超声波辐射以后 ,NH3 N的吹脱效果明显增加 ,与传统吹脱技术相比 ,NH3 N的去除率增加了 1 7%—1 64%。经超声吹脱处理后的废水 ,NH3 N完全可以达到国家排放标准     

Growth and foliar nitrogen status of four plant species exposed to atmospheric ammonia

A chamber study was conducted to evaluate the growth response and leaf nitrogen (N) status of four plant species exposed to continuous ammonia (NH3) for 12 weeks (wk). This was intended to evaluate appropriate plant species that could be used to trap discharged NH3 from the exhaust fans in poultry feeding operations before moving off-site. Two hundred and forty bare-root plants of four species (Juniperus virginiana (red cedar), Gleditsia triacanthos var. inermis (thornless honey locust), Populus sp. (hybrid poplar), and Phalaris arundinacea (reed canary grass) were transplanted into 4- or 8-L polyethylene pots and grown in four environmentally controlled chambers. Plants placed in two of the four chambers received continuous exposure to anhydrous NH3 at 4 to 5 ppm while plants in another two chambers received no NH3. In each of the four chambers, 2 to 4 plants per species received no fertilizer while the rest of the plants were fertilized with a 100 ppm solution containing 21% N, 7% phosphorus, and 7% potassium. The results showed that honey locust was the fastest-growing species. The superior growth of honey locust among all species was also supported by its total biomass, root, and root dry matter (DM) weights. For all species there was a trend for plants exposed to NH3 to have greater leaf DM than their non-exposed counterparts at 6 (43.0 vs. 30.8%; P = 0.09) and 12 wk (47.9 vs. 36.6%; P = 0.07), and significantly greater (P 相似文献   

Atmospheric nitrogen deposition in south-east Scotland: Quantification of the organic nitrogen fraction in wet,dry and bulk deposition

Water soluble organic nitrogen (WSON) compounds are ubiquitous in precipitation and in the planetary boundary layer, and therefore are a potential source of bioavailable reactive nitrogen. This paper examines weekly rain data over a period of 22 months from June 2005 to March 2007 collected in 2 types of rain collector (bulk deposition and “dry + wet” deposition) located in a semi-rural area 15 km southwest of Edinburgh, UK (N55°51′44″, W3°12′19″). Bulk deposition collectors are denoted in this paper as “standard rain gauges”, and they are the design used in the UK national network for monitoring precipitation composition. “Dry + wet” deposition collectors are flushing rain gauges and they are equipped with a rain detector (conductivity array), a spray nozzle, a 2-way valve and two independent bottles to collect funnel washings (dry deposition) and true wet deposition. On average, for the 27 weekly samples with 3 valid replicates for the 2 types of collectors, dissolved organic nitrogen (DON) represented 23% of the total dissolved nitrogen (TDN) in bulk deposition. Dry deposition of particles and gas on the funnel surface, rather than rain, contributed over half of all N-containing species (inorganic and organic). Some discrepancies were found between bulk rain gauges and flushing rain gauges, for deposition of both TDN and DON, suggesting biological conversion and loss of inorganic N in the flushing samplers.     

腐殖填料生物滤池氨氮降解特征

根据腐殖填料生物滤池及石英砂普通生物滤池的氨氮去除效率、表面水力负荷及微生物量差异,比较两者氨氮降解速率及比降解速率,对腐殖填料生物滤池的氨氮降解特征进行分析。结果表明,在相同运行方式及外界环境下,腐殖填料滤池表面水力负荷数倍于石英砂普通生物滤池;腐殖填料生物滤池单位体积平均氨氮降解速率高达31.5 g NH4+-N/(m3.d),是石英砂普通生物滤池的5.4倍;腐殖填料生物滤池氨氮比降解速率为4.1×10-2μg NH4+-N/(g微生物碳.d),约为石英砂普通生物滤池的4倍。腐殖填料生物滤池能负载较高的生物量,抗堵塞性能较强,系统内特异微生物对氨氮降解能力较高,是一种优良的降解氨氮的生物滤池。     

高浓度氨氮废水同步硝化反硝化性能研究

利用序批式反应器研究了溶解氧浓度和进水碳氮比对高浓度氨氮废水脱氮性能的影响.结果表明,溶解氧浓度降低实现了短程同步硝化反硝化,并提高了反应器脱氮效率.反应器运行经历了外部碳源的摄取、PHB储存、PHB有氧氧化和同步硝化反硝化作用,PHB作为同步硝化反硝化过程中反硝化的电子供体.     

高有机物浓度下氨氮的好氧硝化

污水中往往同时含有较高浓度的有机物和氨氮,研究较高有机物浓度下氨氮的好氧生物硝化,以为工程应用提供实践和理论依据。考察了COD浓度为1 200 mg·L-1,好氧活性污泥处理氨氮废水过程中COD、NH4+-N的去除情况,硝态氮、亚硝态氮的生成情况。在整个驯化阶段,氨氮的最高去除率达到86.42%,COD最高去除率达到85.40%,同时亚硝态氮的最大生成量为15.97 mg·L-1,硝态氮的最高生成量为5.14 mg·L-1,且8 h的短期实验显示,COD、NH4+-N的去除可以同步进行。