Cytomegalovirus-associated acute respiratory failure in lupus patients: case reports in relation to cytomegalovirus biology.

With the wide use of immunosuppressive agents, life-threatening cytomegalovirus-associated acute respiratory failure occurs frequently. However, this condition is yet to be fully recognized and the therapeutic approach to it can only be based on comprehensive protocols rather than the biological characteristics of cytomegalovirus. We describe three acute respiratory failure events that were related to the pathogenicity of cytomegalovirus, the primary cytopathic effect and secondary antiviral immunity-mediated damage. All cytomegalovirus infection occurred after immunosuppressive usage while the acute respiratory failure events took place in different clinical settings. The first acute respiratory failure event originated from the immunoinflammatory response after cytomegalovirus infection was circumscribed, while the second resulted from cytomegalovirus reactivation and the third was caused by the combined effect of acute cytomegalovirus infection and the subsequent immunoinflammatory response. According to the clinical setting, corresponding therapeutic approaches (sequential or combined strategy) were carried out. All the patients here presented were responsive to the above therapeutic strategies. Consequently, cytomegalovirus-associated acute respiratory failure in systemic lupus erythematosus patients should be carefully differentiated and a sequential or combined strategy should be carried out according to the clinical setting. Overall, we find that there are three patterns of cytomegalovirus-associated acute respiratory failure in systemic lupus erythematosus patients and propose a novel therapeutic strategy in relation to cytomegalovirus biology.

Outcome of serial cardiac evaluations during doxorubicin-based chemotherapy in small- to medium-sized dogs with multicentric lymphoma.

Doxorubicin is an anthracycline antitumor antibiotic with dose-dependent and cumulative cardiotoxicity. However, the necessity for serial cardiac evaluation is unknown in dogs without risk factors for dilated cardiomyopathy (DCM). This study aimed to investigate serial changes in echocardiographic and electrocardiographic measures in small- and medium-sized dogs after four doxorubicin doses. We included 17 dogs, weighting < 20 kg, with multicentric lymphoma. All dogs received doxorubicin over 30 min every 4 weeks as part of a multi-drug chemotherapy protocol. The average doxorubicin dose was 3.8 times per dog. Clinical cardiotoxicity was not observed during the monitoring period. The incidence of developing arrhythmia was not significantly associated with the number of doxorubicin doses received (P = 0.600). The development of valvular regurgitations and mitral regurgitation in these dogs was not significantly associated with the number of doxorubicin doses (P = 0.363 and P = 0.779, respectively). The other echocardiographic results were not significantly different between each evaluation. In conclusion, our results showed no significant cardiotoxicity under echocardiogram and electrocardiogram in small- and medium-sized dogs without risk factors for DCM after four doses of doxorubicin in a 30-minute infusion method.

High-field magnetization and electronic spin resonance study in the twisted honeycomb latticeα-Mn2V2O7.

We report the single-crystal growth of Mn2V2O7and the results of magnetic susceptibility, high-field magnetization up to 55 T and high-frequency electric spin resonance (ESR) measurements for its low-temperatureαphase. Two antiferromagnetic (AFM) ordering at 17.5 K and 3 K and obvious magnetic anisotropy are observed inα-Mn2V2O7upon cooling. In pulsed high magnetic fields, the compound reaches the saturation magnetic moment of ∼10.5µBfor each molecular formula at around 45 T after two undergoing AFM phase transitions atHc1≈ 16 T,Hc2≈ 34.5 T forH//[11-0] andHsf1= 2.5 T,Hsf2= 7 T forH//[001]. In these two directions, two and seven resonance modes are detected by ESR spectroscopy, respectively. Theω1andω2modes ofH//[11-0] can be well described by two-sublattice AFM resonance mode with two zero-field gaps at 94.51 GHz and 169.28 GHz, indicating a hard-axis feature. The seven modes forH//[001] are partially separated by the critical fields ofHsf1andHsf2, displaying the two signs of spin-flop transition. The fittings ofωc1andωc2modes yield zero-field gaps at 69.50 GHz and 84.73 GHz forH//[001], confirming the axis-type anisotropy. The saturated moment and gyromagnetic ratio indicate the Mn2+ion inα-Mn2V2O7is in a high spin state with orbital moment completely quenched. A quasi-one-dimensional magnetism with a zig-zag-chain spin configuration is suggested inα-Mn2V2O7, due to the special neighbor interactions caused by a distorted network structure with honeycomb layer.

Bacterial magnetic particles as a novel and efficient gene vaccine delivery system.

DNA vaccination is an attractive approach for eliciting antigen-specific immunity. In this study, we used magnetosomes (bacterial magnetic particles, BMPs) as carriers of a recombinant DNA composed of a secondary lymphoid tissue chemokine, human papillomavirus type E7 (HPV-E7) and Ig-Fc fragment (pSLC-E7-Fc) to generate a gene vaccine (BMP-V) for tumour immunotherapy. The results indicate that BMPs linked to DNA more efficiently in phosphate-buffered saline (pH=4-5) than in physiological saline. Efficient transfection of BMP-V in vitro and in vivo was achieved when a 600-mT static magnetic field was applied for 10 min. In a mouse tumour model, subcutaneous injection of BMP-V (5 µg, × 3 at 4-day intervals) plus magnetic exposure elicited systemic HPV-E7-specific immunity leading to significant tumour inhibition. The treated mice tolerated BMP-V immunisation well with no toxic side effects, as shown by histopathological examinations of major internal organs. Taken together, these results suggest that BMP can be used as a gene carrier to elicit a systemic immune response.

Development of a low-cost system for measuring conditional time-averaged gradients of SO2 and NH3.

A conditional time-averaged gradient (COTAG) system has been developed to provide direct long-term (weekly to monthly) average flux gradient measurements for a range of trace gases, between land and atmosphere. Over daily periods, atmospheric conditions can range from high stability, where the vertical gradients of ambient concentration are enhanced due to very small diffusivity, to highly unstable conditions, in which concentration gradients are small due to the intense turbulent activity of the surface layer. The large vertical gradients generated by high stability would bias the estimate of the actual flux: to avoid this, the COTAG system samples conditionally, within a carefully refined range of stability. A comparison with a continuous flux gradient system suggested that the removal of stable conditions from the sampling period does not substantially modify the evaluation of the long-term fluxes.

Modelling the spatial distribution of ammonia emissions in the UK.

Ammonia emissions (NH3) are characterised by a high spatial variability at a local scale. When modelling the spatial distribution of NH3 emissions, it is important to provide robust emission estimates, since the model output is used to assess potential environmental impacts, e.g. exceedance of critical loads. The aim of this study was to provide a new, updated spatial NH3 emission inventory for the UK for the year 2000, based on an improved modelling approach and the use of updated input datasets. The AENEID model distributes NH3 emissions from a range of agricultural activities, such as grazing and housing of livestock, storage and spreading of manures, and fertilizer application, at a 1-km grid resolution over the most suitable landcover types. The results of the emission calculation for the year 2000 are analysed and the methodology is compared with a previous spatial emission inventory for 1996.

Uncertainties and implications of applying aggregated data for spatial modelling of atmospheric ammonia emissions.

Ammonia emissions vary greatly at a local scale, and effects (eutrophication, acidification) occur primarily close to sources. Therefore it is important that spatially distributed emission estimates are located as accurately as possible. The main source of ammonia emissions is agriculture, and therefore agricultural survey statistics are the most important input data to an ammonia emission inventory alongside per activity estimates of emission potential. In the UK, agricultural statistics are collected at farm level, but are aggregated to parish level, NUTS-3 level or regular grid resolution for distribution to users. In this study, the Modifiable Areal Unit Problem (MAUP), associated with such amalgamation, is investigated in the context of assessing the spatial distribution of ammonia sources for emission inventories. England was used as a test area to study the effects of the MAUP. Agricultural survey data at farm level (point data) were obtained under license and amalgamated to different areal units or zones: regular 1-km, 5-km, 10-km grids and parish level, before they were imported into the emission model. The results of using the survey data at different levels of amalgamation were assessed to estimate the effects of the MAUP on the spatial inventory. The analysis showed that the size and shape of aggregation zones applied to the farm-level agricultural statistics strongly affect the location of the emissions estimated by the model. If the zones are too small, this may result in false emission "hot spots", i.e., artificially high emission values that are in reality not confined to the zone to which they are allocated. Conversely, if the zones are too large, detail may be lost and emissions smoothed out, which may give a false impression of the spatial patterns and magnitude of emissions in those zones. The results of the study indicate that the MAUP has a significant effect on the location and local magnitude of emissions in spatial inventories where amalgamated, zonal data are used.

Challenges in quantifying biosphere-atmosphere exchange of nitrogen species.

Recent research in nitrogen exchange with the atmosphere has separated research communities according to N form. The integrated perspective needed to quantify the net effect of N on greenhouse-gas balance is being addressed by the NitroEurope Integrated Project (NEU). Recent advances have depended on improved methodologies, while ongoing challenges include gas-aerosol interactions, organic nitrogen and N(2) fluxes. The NEU strategy applies a 3-tier Flux Network together with a Manipulation Network of global-change experiments, linked by common protocols to facilitate model application. Substantial progress has been made in modelling N fluxes, especially for N(2)O, NO and bi-directional NH(3) exchange. Landscape analysis represents an emerging challenge to address the spatial interactions between farms, fields, ecosystems, catchments and air dispersion/deposition. European up-scaling of N fluxes is highly uncertain and a key priority is for better data on agricultural practices. Finally, attention is needed to develop N flux verification procedures to assess compliance with international protocols.

Throughfall and bulk deposition of dissolved organic nitrogen to holm oak forests in the Iberian Peninsula: Flux estimation and identification of potential sources.

Deposition of dissolved organic nitrogen (DON) in both bulk precipitation (BD) and canopy throughfall (TF) has been measured for the first time in the western Mediterranean. The study was carried out over a year from 2012 to 2013 at four evergreen holm oak forests located in the Iberian Peninsula: two sites in the Province of Barcelona (Northeastern Spain), one in the Province of Madrid (central Spain) and the fourth in the Province of Navarra (Northern Spain). In BD the annual volume weighted mean (VWM) concentration of DON ranged from 0.25 mg l(-1) in Madrid to 1.14 mg l(-1) in Navarra, whereas in TF it ranged from 0.93 mg l(-1) in Barcelona to 1.98 mg l(-1) in Madrid. The contribution of DON to total nitrogen deposition varied from 34% to 56% in BD in Barcelona and Navarra respectively, and from 38% in Barcelona to 72% in Madrid in TF. Agricultural activities and pollutants generated in metropolitan areas were identified as potential anthropogenic sources of DON at the study sites. Moreover, canopy uptake of DON in Navarra was found in spring and autumn, showing that organic nitrogen may be a supplementary nutrient for Mediterranean forests, assuming that a portion of the nitrogen taken up is assimilated during biologically active periods.

Identification of endogenous electrophiles by means of mass spectrometric determination of protein and DNA adducts.

Monitoring exposure to alkylating agents may be achieved by quantitatively determining the adduct levels formed with nucleic acids and/or proteins. One of the most significant results arising from the application of this approach has been the discovery in control populations of "background" levels of alkylated nucleic acid bases or alkylated proteins, in particular hemoglobin (Hb). In the case of Hb, a wide variety of such adducts have been detected and quantitated by mass spectrometric techniques, with methylated, 2-carboxyethylated, and 2-hydroxyethylated modifications being most abundant. Although the source of these alkylation products is unknown, both endogenous and exogenous sources may be proposed. We have recently confirmed the presence of the N-terminal hydroxyethylvaline adduct in control human Hb using tandem mass spectrometry (MS-MS) and have now established background levels using GC-MS in more than 70 samples. Smoking raises the levels of the adduct up to 10-fold and occupational exposure to ethylene oxide up to 300-fold. Background levels of alkylated nucleic acids may be studied by analysis of N7-alkylated guanine or N3-alkylated adenine, which are excised from nucleic acids after their formation and are excreted in urine. Although the presence of some of these urinary constituents may be accounted for by their natural occurrence in RNA or diet, the endogenous or exogenous source of others is unknown. Quantitative methods using MS-MS have now been developed for five of the observed urinary alkylguanines [N7-methyl-, N2-methyl-, N2-dimethyl-, N7-(2-hydroxyethyl)-, and N2-ethylguanine].(ABSTRACT TRUNCATED AT 250 WORDS)

CT in diagnosis of acoustic neuromas.

A detailed analysis of the CT findings in 75 cases of acoustic neuroma is presented. The method of examination included plain and enhanced CT, metrizamide CT cisternography (M-CTC), and gas CT cisternography (gas-CTC). The common CT appearances of acoustic neuromas were as follows: 93.6% appeared as isodense or hypodense on precontrast scan; homogeneous enhancement was observed in 53.8% on postcontrast scan; the tumor center, mostly located at the level of the internal acoustic canal, was spherical in shape with an acute angle between the lateral tumor border and petrous bone; and there was widening of the internal acoustic canal or destruction of petrous bone. However, the presence of an acoustic neuroma could not be excluded if widening of the internal acoustic canal was absent. It was not certain whether contrast filling of the internal acoustic canal occurred at M-CTC in the four cases so examined. One case of intracanalicular neuroma was diagnosed by gas-CTC, which is the most sensitive and reliable technique for detecting and excluding small tumors. The significance of various CT appearances, early diagnosis, and differential diagnosis of acoustic neuroma from other cerebellopontine-angle tumors, particularly meningioma, are discussed.

Dynamic CT of the laterosellar extradural venous spaces.

We evaluated the ability of dynamic CT scanning to accurately demonstrate the laterosellar extradural venous spaces. Careful examination of 680 consecutive patients with this technique has permitted us to describe four main venous groups: the veins of the lateral wall (present in 98% of cases), the vein of the inferolateral group located beneath cranial nerve VI (present in 92% of cases), the medial vein located between the internal carotid artery and the pituitary gland (present in 20-30% of cases), and the vein of the carotid sulcus located between the intracavernous internal carotid artery and the lateral wall of the sphenoid bone (present in 65% of cases). The vein of the carotid sulcus is absent only when the internal carotid artery lies close to the sphenoid bone. In 12 patients with suspected cavernous sinus invasion, dynamic CT scanning demonstrated obliteration of the vein of the carotid sulcus. In five patients with huge tumors of the temporal region, dynamic CT scanning of the cavernous sinus permitted demonstration of normal laterosellar extradural venous spaces, thus permitting exclusion of intracavernous sinus invasion. We believe dynamic CT is the imaging technique best suited for studying the laterosellar extradural venous spaces. Its spatial resolution and dynamic capacity make it superior to MR, and it should be the first procedure when invasion of the cavernous sinus by a pituitary tumor is suspected.

Biological and chemical monitoring of occupational exposure to ethylene oxide.

Studies were carried out on two populations occupationally exposed to ethylene oxide (EtO) using different physical and biological parameters. Blood samples were collected from 9 hospital workers (EI) and 15 factory workers (EII) engaged in sterilization of medical equipment with EtO and from matched controls (CI and CII). Average exposure levels during 4 months (the lifespan of erythrocytes) prior to blood sampling were estimated from levels of N-(2-hydroxyethyl)valine adducts in hemoglobin. They were significantly enhanced in EI and EII and corresponded to a 40-h time-weighted average of 0.025 ppm in EI and 5 ppm in EII. Exposures were usually received in bursts with EtO concentrations in air ranging from 22 to 72 ppm in EI and 14 to 400 ppm in EII. All samples were analyzed for HPRT mutants (MFs), chromosomal aberrations (CAs), micronuclei (MN) and SCEs. MFs were significantly enhanced by 60% in EII but not in EI. These results are the first demonstration of mutation induction in man by ethylene oxide. CAs were significantly enhanced in EI and EII by 130% and 260% respectively. MN were not enhanced in EI but significantly in EII(217%). The mean frequency of SCEs was significantly elevated by 20% in EI and by almost 100% in EII. SCE was the only parameter that allowed distinction between daily and occasionally exposed workers in EII. An interesting finding in exposed workers was the large increase of the percentage of cells with high frequencies of SCE (3-4 times in EI and 17-fold in EII). The relative sensitivity of endpoints for detection of EtO exposure in the present investigation was in the following order: HOEtVal adducts greater than SCEs greater than chromosomal aberrations greater than micronuclei greater than HPRT mutants.

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.

Cephalometric studies on the upper airway space in normal Chinese.

A detailed cephalometric analysis of the soft and hard tissues of the upper airway was conducted with lateral cephalographs from 116 normal Chinese, aged between 18 and 25 years. Normal values and deviation range were preliminarily established for the size of the tongue, soft palate, nasopharynx, oropharynx, and hypopharynx, and for the relative position of the hyoid bone and vallecula in both sexes. Statistical findings showed that there were significant differences between the sexes. Significant relationships (P < 0.001) were observed 1) between the hypopharyngeal depth and the position of the hyoid bone and the vallecula, in which the horizontal position of vallecula appears to be the best predictor of the hypopharyngeal depth, as confirmed by the multiple regression equation; 2) between the upper airway depths at four different levels; and 3) between the naso-oropharyngeal area and tongue, soft palate, and oral area. The present data can be used to investigate further the upper airway in abnormal states.

Dynamic CT scan of intracranial tumors.

Of ninety-eight patients with intracranial tumors examined by dynamic CT scanning, 66 were confirmed operatively and pathologically. Our study showed that: 1) Dynamic CT can be performed safely and easily in outpatients; 2) Acoustic neurinoma, meningioma, pituitary chromophobe adenoma, astrocytoma and metastatic tumor have varying levels of time-density curves; 3) The tissue-blood ratio (TBR) at peak time (TBRp) is a useful indicator of the vascularity of tumoral tissues, and analysis of the time-density curve combining with TBRp is helpful to the differential diagnosis of tumors; 4) Differential diagnosis between tumors and vascular abnormalities such as aneurysm and arteriovenous malformation could be made easily with dynamic CT.

Development and types of passive samplers for monitoring atmospheric NO2 and NH3 concentrations.

Numerous passive samplers based on the "Palmes-tube" have been developed for ambient air monitoring. In each case, the diffusion path length and/or cross-sectional area are modified to achieve the desired sampling rate. "Tube-type" samplers are low sensitivity samplers suitable for long-term monitoring, whereas the "badge-type" samplers have faster sampling rates suited to short-term monitoring. In the U.K., diffusion tubes are widely used for monitoring nitrogen dioxide (NO2) and ammonia (NH3). The open-ended diffusion tubes are prone to positive bias caused by incursion of wind eddies, leading to a shortening of the diffusion path. By using a porous membrane at the inlet, wind incursion is prevented, but an additional diffusion resistance is imposed and it is necessary to calibrate the tubes against a reference method to obtain an effective sampling rate. For NO2 sampling, positive bias also arises from the reaction of NO with O3 within the sampler. The interference from the chemical reaction is severe close to NO sources, with errors up to 30% for curbside locations when using the "tube-type" sampler. In rural areas, where NO concentrations are small relative to NO2, these errors are small. In some implementations, there is also a negative bias over long sampling periods caused by the degradation of trapped NO2. The low sampling rates of diffusion tubes make them too uncertain for use at background NH3 concentrations (<1 microg NH3 m(-3)) where they significantly overestimate concentrations. Badge-type samplers such as the "Willems badge" samplers permit accurate sampling at low ambient NH3 concentrations, but suffer from saturation at high concentrations and sensitivity to wind speed. A passive sampler optimised for monthly measurements of NH3 is reported here, together with its application in the U.K. National Ammonia Monitoring Network.

A spatial analysis of atmospheric ammonia and ammonium in the U.K.

As measures are implemented internationally to reduce SO2 and NOx emissions, attention is falling on the contribution of NH3 emissions to acidification, nitrogen eutrophication, and aerosol formation. In the U.K., a monitoring network has been established to measure the spatial distribution and long-term trends in atmospheric gaseous NH3 and aerosol NH4+. At the same time, an atmospheric chemistry and transport model, FRAME, has been developed with a focus on reduced nitrogen (NHx). The monitoring data are important to evaluate the model, while the model is essential for a more detailed spatial assessment. The national network is established with over 80 sampling locations. Measurements of NH3 and NH4+ (at up to 50 sites) have been made using a new low-cost denuder-filterpack system. Additionally, improved passive sampling methods for NH3 have been applied to explore local variability. The measurements confirm the high spatial variability of NH3 (annual means 0.06 to 11 microg NH3 m(-3)), consistent with its nature as a primary pollutant emitted from ground-level sources, while NH4+, being a slowly formed secondary product, shows much less spatial variability (0.14 to 2.4 mg NH4+ m(-3)). These features are reproduced in the FRAME model, which provides estimates at a 5-km level. Analysis of the underlying NH3 emission inventory shows that sheep emissions may have been underestimated and nonagricultural sources overestimated relative to emissions from cattle. The combination of model and measurements is applied to estimate spatial patterns of dry deposition to different vegetation types. The combined approach provides the basis to assess NHx responses across the U.K. to international emission controls.

Ammonia emission and deposition in Scotland and its potential environmental impacts.

The main source of atmospheric ammonia (NH3) in Scotland is livestock agriculture, which accounts for 85% of emissions. The local magnitude of emissions therefore depends on livestock density, type, and management, with major differences occurring in various parts of Scotland. Local differences in agricultural activities therefore result in a wide range of NH3 emissions, ranging from less than 0.2 kg N ha(-1) year(-1) in remote areas of the Scottish Highlands to over 100 kg N ha(-1) year-1 in areas with intensive poultry farming. Scotland can be divided loosely into upland and lowland areas, with NH3 emission being less than and more than 5 kg N ha(-1) year(-1), respectively. Many semi-natural ecosystems in Scotland are vulnerable to nitrogen deposition, including bogs, moorlands, and the woodland ground flora. Because NH3 emissions occur in the rural environment, the local deposition to sensitive ecosystems may be large, making it essential to assess the spatial distribution of NH3 emissions and deposition. A spatial model is applied here to map NH3 emissions and these estimates are applied in atmospheric dispersion and deposition models to estimate atmospheric concentrations of NH3 and NH4+, dry deposition of NH3, and wet deposition of NHx. Although there is a high level of local variability, modelled NH3 concentrations show good agreement with the National Ammonia Monitoring Network, while wet deposition is largest at high altitude sites in the south and west of Scotland. Comparison of the modelled NHx deposition fields with estimated thresholds for environmental effects ("critical loads") shows that thresholds are exceeded across most of lowland Scotland and the Southern Uplands. Only in the cleanest parts of the north and west is nitrogen deposition not a cause for concern. Given that the most intense effects occur within a few kilometres of sources, it is suggested that local spatial abatement policies would be a useful complement to traditional policies that mitigate environmental effects based on emission reduction technologies.

Potential for ammonia recapture by farm woodlands: design and application of a new experimental facility.

There has been increasing pressure on farmers in Europe to reduce the emissions of ammonia from their land. Due to the current financial climate in which farmers have to operate, it is important to identify ammonia control measures that can be adopted with minimum cost. The planting of trees around farmland and buildings has been identified as a potentially effective and low-cost measure to enhance ammonia recapture at a farm level and reduce long-range atmospheric transport. This work assesses experimentally what fraction of ammonia farm woodlands could potentially remove from the atmosphere. We constructed an experimental facility in southern Scotland to simulate a woodland shelterbelt planted in proximity to a small poultry unit. By measuring horizontal and vertical ammonia concentration profiles within the woodland, and comparing this to the concentration of an inert tracer (SF6) we estimate the depletion of ammonia due to dry deposition to the woodland canopy. Together with measurements of mean ammonia concentrations and throughfall fluxes of nitrogen, this information is used to provide a first estimate of the fraction of emitted ammonia that is recaptured by the woodland canopy. Analysis of these data give a lower limit of recapture of emitted ammonia, at the experimental facility, of 3%. By careful design of shelterbelt woodlands this figure could be significantly higher.