Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Transmission through air as a possible route of exposure for MRSA
    Bos, Marian E.H. ; Verstappen, Koen M. ; Cleef, Brigitte A.G.L. Van; Dohmen, Wietske ; Dorado-García, Alejandro ; Graveland, Haitske ; Duim, Birgitta ; Wagenaar, Jaap A. ; Kluytmans, Jan A.J.W. ; Heederik, Dick J.J. - \ 2016
    Journal of Exposure Science and Environmental Epidemiology 26 (2016)3. - ISSN 1559-0631 - p. 263 - 269.
    air - exposure - livestock - MRSA - transmission

    Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is highly prevalent in pigs and veal calves. The environment and air in pig and veal calf barns is often contaminated with LA-MRSA, and can act as a transmission source for humans. This study explores exposure-response relationships between sequence type 398 (ST398) MRSA air exposure level and nasal ST398 MRSA carriage in people working and/or living on farms. Samples and data were used from three longitudinal field studies in pig and veal calf farm populations. Samples consisted of nasal swabs from the human participants and electrostatic dust fall collectors capturing airborne settled dust in barns. In both multivariate and mutually adjusted analyses, a strong association was found between nasal ST398 MRSA carriage in people working in the barns for >20 h per week and MRSA air levels. In people working in the barns <20 h per week there was a strong association between nasal carriage and number of working hours. Exposure to ST398 MRSA in barn air seems to be an important determinant for nasal carriage, especially in the highly exposed group of farmers, next to duration of contact with animals. Intervention measures should therefore probably also target reduction of ST398 MRSA air levels.

    Volatilisation of pesticides after application in vegetable greenhouses
    Doan Ngoc, K. ; Berg, F. van den; Houbraken, M. ; Spanoghe, P. - \ 2015
    Science of the Total Environment 505 (2015). - ISSN 0048-9697 - p. 670 - 679.
    fungicide fenpropimorph - potato crop - plants - soil - air - surfaces - reentry - tunnel
    Background Volatilisation of pesticides after application to the soil or the crop is an important source of emission into the atmosphere. As a result, workers, residents and bystanders are potentially at risk when exposed to these volatilised substances. Nonetheless, data on measured concentrations are quite scarce, especially in greenhouses. The objective of this work is to present the results of volatilisation experiments performed in greenhouses. Results The results indicate that the concentrations are highest in the hours after application and rapidly decline during the days following application. Conclusion Greenhouse temperature, ventilation rate, the substance vapour pressure and the rate of competing processes were identified as important factors influencing volatilisation in greenhouses. The results from this study contribute to a better understanding of volatilisation in greenhouses and may help to improve the recent PEARL model for volatilisation in greenhouses.
    Net CO2 surface emissions at Bern, Switzerland inferred from ambient observations of CO2, d(O2/N2), and 222Rn using a customized radon tracer inversion
    Laan, S. van der; Laan-Luijkx, I.T. van der; Zimmermann, L. ; Conen, F. ; Leuenberger, M. - \ 2014
    Journal of Geophysical Research: Atmospheres 119 (2014)3. - ISSN 2169-897X - p. 1580 - 1591.
    carbon-dioxide - netherlands - methane - rn-222 - air
    The 222Radon tracer method is a powerful tool to estimate local and regional surface emissions of, e.g., greenhouse gases. In this paper we demonstrate that in practice, the method as it is commonly used, produces inaccurate results in case of nonhomogeneously spread emission sources, and we propose a different approach to account for this. We have applied the new methodology to ambient observations of CO2 and 222Radon to estimate CO2 surface emissions for the city of Bern, Switzerland. Furthermore, by utilizing combined measurements of CO2 and d(O2/N2) we obtain valuable information about the spatial and temporal variability of the main emission sources. Mean net CO2 emissions based on 2 years of observations are estimated at (11.2¿±¿2.9) kt km-2 a-1. Oxidative ratios indicate a significant influence from the regional biosphere in summer/spring and fossil fuel combustion processes in winter/autumn. Our data indicate that the emissions from fossil fuels are, to a large degree, related to the combustion of natural gas which is used for heating purposes.
    Atmospheric CO2, d(O2/N2), APO and oxidative ratios from aircraft flask samples over Fyodorovskoye, Western Russia
    Laan, S. van der; Laan-Luijkx, I.T. van der; Rödenbeck, C. ; Varlagin, A. ; Shironya, I. ; Neubert, R.E.M. - \ 2014
    Atmospheric Environment 97 (2014). - ISSN 1352-2310 - p. 174 - 181.
    southern taiga - carbon-cycle - oxygen - o-2/n-2 - siberia - air - climatology - variability - network - tower
    We present atmospheric CO2 and d(O2/N2) from flask samples taken on board aircraft over Fyodorovskoye (56°27'N, 32°55'E) at heights of 3000 m and 100 m between 1998 and 2008. The long-term trends for CO2 and d(O2/N2) are similar for both sampling heights, and also similar to observations from marine background station Mace Head (Ireland) and coastal station Lutjewad (the Netherlands). The seasonal CO2 amplitude at 100 m was almost twice as large as at 3000 m and a phase shift in the seasonality of about two weeks between both sampling heights was observed. This indicates a dominant influence on CO2 in the boundary layer from the regional biosphere which is confirmed by analysis of the d(O2/N2) to CO2 oxidative ratio (OR). Together with simulations with the TM3 model, our data suggest that the observed OR of -1.7 ± 0.2 in the free troposphere is mainly driven by exchange processes with the ocean. Within the boundary layer an OR of -0.89 ± 0.12 was observed which supports the results of other recent studies suggesting the commonly used value of -1.1 for biospheric OR is likely too low.
    Quantification of Methylated Selenium, Sulfur, and Arsenic in the Environment
    Vriens, B. ; Ammann, A.A. ; Hagendorfer, H. ; Lenz, M. ; Berg, M. ; Winkel, L.H.E. - \ 2014
    PLoS ONE 9 (2014)7. - ISSN 1932-6203
    plasma-mass spectrometry - atomic fluorescence spectrometry - solid-phase microextraction - gas-chromatography - speciation analysis - volatile selenium - natural-waters - icp-ms - elements - air
    Biomethylation and volatilization of trace elements may contribute to their redistribution in the environment. However, quantification of volatile, methylated species in the environment is complicated by a lack of straightforward and field-deployable air sampling methods that preserve element speciation. This paper presents a robust and versatile gas trapping method for the simultaneous preconcentration of volatile selenium (Se), sulfur (S), and arsenic (As) species. Using HPLC-HR-ICP-MS and ESI-MS/MS analyses, we demonstrate that volatile Se and S species efficiently transform into specific non-volatile compounds during trapping, which enables the deduction of the original gaseous speciation. With minor adaptations, the presented HPLC-HR-ICP-MS method also allows for the quantification of 13 non-volatile methylated species and oxyanions of Se, S, and As in natural waters. Application of these methods in a peatland indicated that, at the selected sites, fluxes varied between 190–210 ng Se·m-2·d-1, 90–270 ng As·m-2·d-1, and 4–14 µg S·m-2·d-1, and contained at least 70% methylated Se and S species. In the surface water, methylated species were particularly abundant for As (>50% of total As). Our results indicate that methylation plays a significant role in the biogeochemical cycles of these elements
    Nitrous oxide (N2O) emissions from biotrickling filters used for ammonia removal at livestock facilities
    Melse, R.W. ; Mosquera Losada, J. - \ 2014
    Water Science and Technology 69 (2014)5. - ISSN 0273-1223 - p. 994 - 1003.
    activated-sludge - liquid fraction - water-treatment - nitric-oxide - air - nitrification - operations - manure
    Recently several manufacturers of nitrifying biotrickling filters for ammonia (NH3) removal at animal houses have started to add a denitrification step to the installation, aiming to reduce the amount of discharge water by conversion of NH3 to nitrogen gas (N2). The aim of this research was to quantify the possible formation of nitrous oxide (N2O), which is a potent greenhouse gas, in three of these farm-scale installations. Furthermore, the removal efficiency of NH3 and odor was determined. All installations were successful in reducing the amount of discharge water. The average NH3 removal efficiency for the three locations was 85, 71 and 86%, respectively. However, a significant part of the NH3 removed from the inlet air was not converted to N2 but to N2O, which is a potent greenhouse gas. The part of the inlet NH3-N that was converted to N2O-N amounted to 17, 66 and 24%, respectively. The high N2O production might have been caused by a too low scarcity of biodegradable carbon/N ratio for complete denitrification. The average odor removal efficiency was 21, 32 and 48%, respectively. Further research is necessary to explore how process conditions can be adjusted and controlled in order to reduce the production and emission of N2O from these types of systems.
    Meteorology during the DOMINO campaign and its connection with trace gases and aerols
    Adame, J.A. ; Martinez, M. ; Sorribas, M. ; Hidalgo, P.J. ; Vilà-Guerau de Arellano, J. - \ 2014
    Atmospheric Chemistry and Physics 14 (2014). - ISSN 1680-7316 - p. 2325 - 2342.
    oh reactivity measurements - particulate matter - spain - air - variability - emissions - origin - ozone - pm10 - site
    The DOMINO (Diel Oxidant Mechanisms in relation to Nitrogen Oxides) campaign was carried out from 21 November to 8 December 2008 at the El Arenosillo station (SW of Spain) in a coastal-rural environment. The main weather conditions are analysed using local meteorological variables, meteorological soundings and synoptic maps, as well as back trajectories of the air masses using the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory Model) model and a high spatial resolution of meteorological fields. Measurements of the main meteorological parameters were collected both from the surface and from a tall tower. A detailed land use analysis was performed on a 80 km scale showing the main types of vegetation and land use. Also the main anthropogenic atmospheric emission sources – both industrial-urban from Huelva and from the urban Seville area – are shown. A study to identify air mass origins and their variation with height was carried out. In this intensive campaign, air masses coming from different areas with different emission sources were observed: from the NW, with a highly industrial-urban character; continental flows from northerly directions; from the NE, with a pathway starting over the Seville metropolitan area and then continuing over the Doñana National Park; and maritime air masses coming from the Atlantic Ocean. To study the chemistry in the four atmospheric scenarios identified, gas -phase measurements of primary and secondary species such as ozone, NO, NO2 and SO2, biogenic and anthropogenic VOCs (volatile organic compounds) like benzene and isoprene, as well as total particle concentration and chemical composition of the aerosols are compared and discussed. The highest levels for total particle concentration, NO, NO2, SO2, benzene, PM10, PM2.5 and chemical elements such as As or Cu were found under flows associated with industrial-urban emissions from the Huelva–Portugal sector which are transported to the site before significant removal by chemical or deposition mechanism can occur. The air masses from the north were affected mainly by crustal elements and biogenic sources, the latter being exemplified by the biogenic species such as isoprene, particularly in the first part of the campaign. The urban air from the Seville area, before arriving at El Arenosillo, traversed the Doñana National Park and therefore was affected by industrial-urban and biogenic emissions. This aged air parcel can transport low levels of NOx, total particle concentration and SO2 as well as ozone and isoprene. Marine air masses from the Atlantic Ocean influence El Arenosillo frequently. Under these conditions, the lowest levels of almost all the species – with the exception of ozone levels associated to long-range transport – were measured
    TransCom model simulations of methane: Comparison of vertical profiles with aircraft measurements
    Saito, R. ; Patra, P.K. ; Sweeney, C. ; Machida, T. ; Krol, M.C. ; Houweling, S. ; Bousquet, P. ; Agusti-Panareda, A. ; Belikov, D. ; Bergmann, D. ; Bian, H.S. ; Cameron-Smith, P. ; Chipperfield, M.P. ; Fortems-Cheiney, A. ; Fraser, A. ; Gatti, L.V. ; Gloor, E. ; Hess, P. ; Kawa, S.R. ; Law, R.M. ; Locatelli, R. ; Loh, Z. ; Maksyutov, S. ; Meng, L. ; Miller, J.B. ; Palmer, P.I. ; Prinn, R.G. ; Rigby, M. ; Wilson, C. - \ 2013
    Journal of Geophysical Research: Atmospheres 118 (2013)9. - ISSN 2169-897X - p. 3891 - 3904.
    chemical-transport model - atmospheric co2 - troposphere - stratosphere - variability - sensitivity - version - ozone - flux - air
    To assess horizontal and vertical transports of methane (CH4) concentrations at different heights within the troposphere, we analyzed simulations by 12 chemistry transport models (CTMs) that participated in the TransCom-CH4 intercomparison experiment. Model results are compared with aircraft measurements at 13 sites in Amazon/Brazil, Mongolia, Pacific Ocean, Siberia/Russia, and United States during the period of 2001-2007. The simulations generally show good agreement with observations for seasonal cycles and vertical gradients. The correlation coefficients of the daily averaged model and observed CH4 time series for the analyzed years are generally larger than 0.5, and the observed seasonal cycle amplitudes are simulated well at most sites, considering the between-model variances. However, larger deviations show up below 2 km for the model-observation differences in vertical profiles at some locations, e.g., at Santarem, Brazil, and in the upper troposphere, e.g., at Surgut, Russia. Vertical gradients and concentrations are underestimated at Southern Great Planes, United States, and Santarem and overestimated at Surgut. Systematic overestimation and underestimation of vertical gradients are mainly attributed to inaccurate emission and only partly to the transport uncertainties. However, large differences in model simulations are found over the regions/seasons of strong convection, which is poorly represented in the models. Overall, the zonal and latitudinal variations in CH4 are controlled by surface emissions below 2.5 km and transport patterns in the middle and upper troposphere. We show that the models with larger vertical gradients, coupled with slower horizontal transport, exhibit greater CH4 interhemispheric gradients in the lower troposphere. These findings have significant implications for the future development of more accurate CTMs with the possibility of reducing biases in estimated surface fluxes by inverse modeling.
    Organophosphorus flame-retardant and plasticizer analysis, including recommendations form the first worldwide interlaboratory study
    Brandsma, S.H. ; Boer, J. de; Leonards, P.E.G. ; Cofino, W.P. ; Covaci, A. - \ 2013
    TrAC : Trends in Analytical Chemistry 43 (2013). - ISSN 0165-9936 - p. 217 - 228.
    tandem mass-spectrometry - indoor environments - gas-chromatography - population characteristics - chemical-ionization - organic-compounds - phthalate-esters - water samples - new-model - air
    The first worldwide interlaboratory study on organophosphorus flame retardants (PFRs) was organized to improve the quality of the data reported in the literature. The study involved standard solutions, dust, fish oil and sediment samples. The differences in coefficients of variation (CV) between the samples were related more to PFR concentration (with high blanks being reported by some laboratories) and less to matrix type. Not all participating laboratories suffered from blank problems, which indicated that it was possible to control the blanks. We include recommendations on how to improve analytical performance, especially to reduce contamination of blanks.
    Praktijkexperiment ontvochtigen met zouten: Gebruik en regeneratie van hygroscopisch zout in een kasproef bij Lans Zeeland
    Raaphorst, M.G.M. - \ 2013
    Bleiswijk : Wageningen UR Glastuinbouw (Rapporten GTB 1228) - 30
    glastuinbouw - kasproeven - hygroscopische materialen - zouten - ontvochtiging - lucht - warmteterugwinning - energiebesparing - nederland - teelt onder bescherming - greenhouse horticulture - greenhouse experiments - hygroscopic materials - salts - dehumidification - air - heat recovery - energy saving - netherlands - protected cultivation
    Door kaslucht langs een geconcentreerde zoutoplossing te blazen wordt vocht uit de kaslucht onttrokken. Bij dit proces komt warmte vrij dat direct aan de (gedroogde) kaslucht kan worden afgegeven. Met dit principe kan in theorie 50% energie worden bespaard omdat de latente warmte (verdampingswarmte van water) die normaliter wordt afgelucht, nu kan worden gebruikt om de kaslucht te verwarmen. Deze energiebesparing past bij de doelen van het programma Kas als Energiebron, die daarom onderzoek hierover financieel ondersteunt. Bij de gesloten kas van Lans Zeeland is een proefinstallatie van een tralie breed, gedurende een jaar getest door de lucht in de kas te blazen via een padwall met een continu stromende zoutoplossing. Bij dit systeem is de zoutoplossing geregenereerd (gedroogd) door middel van een vacuümverdamper en een warmtepomp, waarbij het uitgedampte water en de daarbij vrijkomende energie weer wordt teruggewonnen.
    The stable isotopic signature of biologically produced molecular hydrogen (H-2)
    Walter, S. ; Laukenmann, S. ; Stams, A.J.M. ; Vollmer, M.K. ; Gleixner, G. ; Rockmann, T. - \ 2012
    Biogeosciences 9 (2012)10. - ISSN 1726-4170 - p. 4115 - 4123.
    atmospheric hydrogen - stratosphere - economy - budget - model - cycle - air - fractionation - troposphere - photolysis
    Biologically produced molecular hydrogen (H-2) is characterised by a very strong depletion in deuterium. Although the biological source to the atmosphere is small compared to photochemical or combustion sources, it makes an important contribution to the global isotope budget of H-2. Large uncertainties exist in the quantification of the individual production and degradation processes that contribute to the atmospheric budget, and isotope measurements are a tool to distinguish the contributions from the different sources. Measurements of delta D from the various H-2 sources are scarce and for biologically produced H-2 only very few measurements exist. Here the first systematic study of the isotopic composition of biologically produced H-2 is presented. In a first set of experiments, we investigated delta D of H-2 produced in a biogas plant, covering different treatments of biogas production. In a second set of experiments, we investigated pure cultures of several H-2 producing microorganisms such as bacteria or green algae. A Keeling plot analysis provides a robust overall source signature of delta D = -712 parts per thousand (+/-13 parts per thousand) for the samples from the biogas reactor (at 38 degrees C, delta D-H2O = +73.4 parts per thousand), with a fractionation constant epsilon H-2-H2O of -689 parts per thousand (+/-20 parts per thousand) between H-2 and the water. The five experiments using pure culture samples from different microorganisms give a mean source signature of delta D = -728 parts per thousand (+/-28 parts per thousand), and a fractionation constant epsilon H-2-H2O of -711 parts per thousand (+/-34 parts per thousand) between H-2 and the water. The results confirm the massive deuterium depletion of biologically produced H-2 as was predicted by the calculation of the thermodynamic fractionation factors for hydrogen exchange between H-2 and water vapour. Systematic errors in the isotope scale are difficult to assess in the absence of international standards for delta D of H-2. As expected for a thermodynamic equilibrium, the fractionation factor is temperature dependent, but largely independent of the substrates used and the H-2 production conditions. The equilibrium fractionation coefficient is positively correlated with temperature and we measured a rate of change of 2.3 parts per thousand/degrees C between 45 degrees C and 60 degrees C, which is in general agreement with the theoretical prediction of 1.4%/degrees C. Our best experimental estimate for epsilon H-2-H2O at a temperature of 20 degrees C is -731 parts per thousand (+/-20 parts per thousand) for biologically produced H-2. This value is close to the predicted value of -722 parts per thousand, and we suggest using these values in future global H-2 isotope budget calculations and models with adjusting to regional temperatures for calculating delta D values.
    Air handling units and forced ventilation
    Nederhoff, E.M. ; Weel, P.A. van - \ 2012
    Practical Hydroponics & Greenhouses 2012 (2012)125. - ISSN 1321-8727 - p. 24 - 29.
    kastechniek - lucht - bewerking - ontvochtiging - kunstmatige ventilatie - kassen - greenhouse technology - air - handling - dehumidification - artificial ventilation - greenhouses
    Air Handling Units (AHUs) generate forced ventilation and assist in drying, warming, humidifying and potentially cooling of a greenhouse.
    Uncertainty modelling to evaluate nitrogen balances as a tool to determine N2 and N2O formation in ammonia bioscrubbers
    Estelles, F. ; Calvet, S. ; Melse, R.W. ; Ogink, N.W.M. - \ 2012
    Environmental Engineering Science 29 (2012)6. - ISSN 1092-8758 - p. 520 - 525.
    sensitivity-analysis - biotrickling filter - ventilation rates - waste gases - air - removal - emissions - netherlands - buildings - europe
    Biological scrubbers aim at reducing gaseous ammonia emissions by transferring it to a water phase followed by conversion to nitrite and nitrate. A small part of the removed nitrogen may be emitted as N2 and N2O produced as a result of denitrification processes. Due to the large greenhouse warming potential of N2O, even a small emission could be a point of concern. Determining these N losses in form of N2 and N2O via nitrogen balance is an alternative, but little is known about the uncertainty associated to this method. The main aim of this work was to develop an uncertainty model that evaluated N-balances in biological scrubbers in terms of result uncertainty. Secondary objectives were to provide a methodology to determine individual uncertainties involved, and to conduct a sensitivity analysis to identify the main contributors to the final uncertainty. For a defined scenario (biotrickling scrubber, 70% NH3 removal; 5% of inlet N-NH3 lost as N2 and N2O), the standard uncertainty expressed in relative terms of the average was 132% (released N in form of N2 and N2O). Main contributors to the final uncertainty were airflow rate and water volume in the scrubber basin. Uncertainty of the measurements of gaseous NH3 concentrations and N compounds in water had a reduced effect on the final uncertainty. Based on these results, N balances are not recommended to evaluate N2 and N2O formation in biological scrubbers, at least for the conditions considered in this work.
    Case study of the diurnal variability of chemically active species with respect to boundary layer dynamics during DOMINO
    Stratum, B.J.H. van; Vilà-Guerau de Arellano, J. ; Ouwersloot, H.G. ; Dries, K. van den; Laar, T.W. van; Martinez, M. ; Lelieveld, J. ; Diesch, J.M. ; Drewnick, F. ; Fischer, H. ; Hosaynali Beygi, Z. ; Harder, H. ; Regelin, E. ; Sinha, V. ; Adame, J.A. ; Sörgel, M. ; Sander, R. ; Bozem, H. ; Song, W. ; Williams, J. ; Yassaa, N. - \ 2012
    Atmospheric Chemistry and Physics 12 (2012). - ISSN 1680-7316 - p. 5329 - 5341.
    volatile organic-compounds - tropical forest - oh reactivity - isoprene - chemistry - campaign - air - segregation - turbulence - gabriel
    We study the interactions between atmospheric boundary layer (ABL) dynamics and atmospheric chemistry using a mixed-layer model coupled to chemical reaction schemes. Guided by both atmospheric and chemical measurements obtained during the DOMINO (Diel Oxidant Mechanisms in relation to Nitrogen Oxides) campaign (2008), numerical experiments are performed to study the role of ABL dynamics and the accuracy of chemical schemes with different complexity: the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4) and a reduced mechanism of this chemical system. Both schemes produce satisfactory results, indicating that the reduced scheme is capable of reproducing the O3-NOx-VOC-HOx diurnal cycle during conditions characterized by a low NOx regime and small O3 tendencies (less than 1 ppb per hour). By focusing on the budget equations of chemical species in the mixedlayer model, we show that for species like O3, NO and NO2, the influence of entrainment and boundary layer growth is of the same order as chemical production/loss. This indicates that an accurate representation of ABL processes is crucial in understanding the diel cycle of chemical species. By comparing the time scales of chemical reactive species with the mixing time scale of turbulence, we propose a classification based on the Damk¨ohler number to further determine the importance of dynamics on chemistry during field campaigns. Our findings advocate an integrated approach, simultaneously solving the ABL dynamics and chemical reactions, in order to obtain a better understanding of chemical pathways and processes and the interpretation of the results obtained during measurement campaigns.
    Impact of CO2 measurement bias on CarbonTracker surface flux estimates
    Masarie, K.A. ; Petron, G. ; Andrews, A. ; Bruhwiler, L. ; Conway, T.J. ; Jacobson, A.R. ; Miller, J.B. ; Tans, P.P. ; Worthy, D.E. ; Peters, W. - \ 2011
    Journal of Geophysical Research: Atmospheres (2011). - ISSN 2169-897X - 13 p.
    carbon-dioxide exchange - tall tower - model tm5 - atmospheric co2 - inversions - scale - air
    For over 20 years, atmospheric measurements of CO2 dry air mole fractions have been used to derive estimates of CO2 surface fluxes. Historically, only a few research laboratories made these measurements. Today, many laboratories are making CO2 observations using a variety of analysis techniques and, in some instances, using different calibration scales. As a result, the risk of biases in individual CO2 mole fraction records, or even in complete monitoring networks, has increased over the last decades. Ongoing experiments comparing independent, well-calibrated measurements of atmospheric CO2 show that biases can and do exist between measurement records. Biases in measurements create artificial spatial and temporal CO2 gradients, which are then interpreted by an inversion system, leading to erroneous flux estimates. Here we evaluate the impact of a constant bias introduced into the National Oceanic and Atmospheric Administration (NOAA) quasi-continuous measurement record at the Park Falls, Wisconsin (LEF), tall tower site on CarbonTracker flux estimates. We derive a linear relationship between the magnitude of the introduced bias at LEF and the CarbonTracker surface flux responses. Temperate North American net flux estimates are most sensitive to a bias at LEF in our CarbonTracker inversion, and its linear response rate is 68 Tg C yr-1 (~10% of the estimated North American annual terrestrial uptake) for every 1 ppm of bias in the LEF record. This sensitivity increases when (1) measurement biases approached assumed model errors and (2) fewer other measurement records are available to anchor the flux estimates despite the presence of bias in one record. Flux estimate errors are also calculated beyond North America. For example, biospheric uptake in Europe and boreal Eurasia combined increases by 25 Tg C yr-1 per ppm CO2 to partially compensate for changes in the North American flux totals. These results illustrate the importance of well-calibrated, high-precision CO2 dry air mole fraction measurements, as well as the value of an effective strategy for detecting bias in measurements. This study stresses the need for a monitoring network with the necessary density to anchor regional, continental, and hemispheric fluxes more tightly and to lessen the impact of potentially undetected biases in observational networks operated by different national and international research programs.
    Investigation of the Efficiencies of Bioaerosol Samplers for Collecting Aerosolized Bacteria Using a Fluorescent Tracer. II: Sampling Efficiency and Half-Life Time
    Zhao, Y. ; Aarnink, A.J.A. ; Doornenbal, P. ; Huynh, T.T.T. ; Groot Koerkamp, P.W.G. ; Landman, W.J.M. ; Jong, M.C.M. de - \ 2011
    Aerosol Science and Technology 45 (2011)3. - ISSN 0278-6826 - p. 432 - 442.
    escherichia-coli-b - relative-humidity - enterococcus-faecalis - airborne survival - performance - viruses - air - microorganisms - enumeration - rotavirus
    Using uranine as a physical tracer, this study assessed the sampling efficiencies of four bioaerosol samplers (Andersen 6-stage impactor, all glass impinger “AGI-30,” OMNI-3000, and Airport MD8 with gelatin filter) for collecting Gram-positive bacteria (Enterococcus faecalis), Gram-negative bacteria (Escherichia coli and Campylobacter jejuni), and bacteria without cell wall (Mycoplasma synoviae) which were aerosolized in a HEPA isolator. In addition, the half-life times of these bacteria in aerosols were estimated. The uranine concentrations collected by the samplers were used for calculating the physical efficiencies, and the bacteria/uranine ratios were used for calculating the biological efficiencies. The results show the Airport MD8 had the highest physical efficiency. Compared with the Airport MD8, the physical efficiencies of the AGI-30 and the OMNI-3000 were 74% and 49%, respectively. A low physical efficiency of the Andersen impactor (18%) was obtained, but it was mainly caused by the incomplete recovery of uranine when handling the air samples, so could not be ascribed to the sampler efficiency. Both the Andersen impactor and the AGI-30 showed high biological efficiencies for all four bacterial species. The biological efficiencies of the OMNI-3000 for C. jejuni (1%) and of the Airport MD8 for E. coli (38%) and C. jejuni (2%) were significantly lower than 100%, indicating that their sampling stresses inactivated the bacterial culturability. The half-life times at 21-23°C temperature and 80-85% relative humidity were 43.3 min for E. faecalis, 26.7 min for M. synoviae, 21.2 min for E. coli, and 4.0 min for C. jejuni in the air.
    Investigation of the Efficiencies of Bioaerosol Samplers for Collecting Aerosolized Bacteria Using a Fluorescent Tracer. I: Effects of Non-sampling Processes on Bacterial Culturability
    Zhao, Y. ; Aarnink, A.J.A. ; Doornenbal, P. ; Huynh, T.T.T. ; Groot Koerkamp, P.W.G. ; Jong, M.C.M. de; Landman, W.J.M. - \ 2011
    Aerosol Science and Technology 45 (2011)3. - ISSN 0278-6826 - p. 423 - 431.
    airborne particles - relative-humidity - survival - rotavirus - swine - air - microorganisms - temperature - enumeration - barns
    By sampling aerosolized microorganisms, the efficiency of a bioaerosol sampler can be calculated depending on its ability both to collect microorganisms and to preserve their culturability during a sampling process. However, those culturability losses in the non-sampling processes should not be counted toward the sampling efficiency. Prior to the efficiency assessment, this study was designed to investigate the culturability losses in three non-sampling processes: (1) the tracer uranine induced loss; (2) the loss during aerosolization (pre-sampling process); and (3) the bacteria and uranine recovery in air sample handling procedures for the samples of the Andersen 6-stage impactor and the Airport MD8 (post-sampling process). The results indicated that uranine had no significant effect on the culturability of Enterococcus faecalis, Escherichia coli, and Mycoplasma synoviae in suspensions (P > 0.05), but negatively affected the culturability of Campylobacter jejuni (P = 0.01). The culturability of E. faecalis, E. coli, and M. synoviae was not affected by stresses caused by aerosolization (P > 0.05). Only 29% of C. jejuni were still culturable during aerosolization (P = 0.02). In the air sample handling procedures, the four species of bacteria were recovered without significant losses from the samples of the Andersen impactor, but only 33-60% uranine was recovered. E. faecalis, E. coli, and M. synoviae were recovered without significant losses from the samples of the Airport MD8. More C. jejuni was recovered (172%), probably due to multiplication or counting variation. It is suggested that tracer and bacteria should be aerosolized separately when the tracer negatively affects the bacterial culturability. In both pre- and post-sampling processes, losses of bacterial culturability (or multiplication) may occur, which should be taken into account when assessing the efficiencies of bioaerosol samplers.
    Buitenluchtaanzuiging en schermen
    Kempkes, Frank - \ 2011
    greenhouse horticulture - greenhouses - blinds - ventilation - temperature - air - humidity - greenhouse technology - energy saving
    Algenkweek op stallucht = Cultivation of algae on ventilation air from animal houses
    Buisonjé, F.E. de; Aarnink, A.J.A. - \ 2011
    Wageningen : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 451) - 17
    algenteelt - teeltsystemen - varkensstallen - lucht - ammoniak - kooldioxide - kosten-batenanalyse - algae culture - cropping systems - pig housing - air - ammonia - carbon dioxide - cost benefit analysis
    The feasibility was studied of producing algae on compounds in the exhaust air of pig houses. The application of ventilation air in algae growing systems will not lead to a significant decrease of production costs of algae.
    Continuous measurements of atmospheric oxygen and carbon dioxide on a North Sea gas platform
    Laan-Luijkx, I.T. van der; Neubert, R.E.M. ; Laan, S. van der; Meijer, H.A.J. - \ 2010
    Atmospheric Measurement Techniques 3 (2010)1. - ISSN 1867-1381 - p. 113 - 125.
    klimaatverandering - kooldioxide - emissie - meting - noordzee - climatic change - carbon dioxide - emission - measurement - north sea - o-2/n-2 ratio - co2 - air - o-2 - cycle - sinks - analyzer - trend
    A new atmospheric measurement station has been established on the North Sea oil and gas production platform F3, 200 km north off the Dutch coast (54°51' N, 4°44' E). Atmospheric concentrations of O2 and CO2 are continuously measured using fuel cell technology and compact infrared absorption instruments, respectively. Furthermore, the station includes an automated air flask sampler for laboratory analysis of the atmospheric concentrations of CO2, CH4, CO and O2 and isotope measurements of d13C, d18O and ¿14C from CO2. This station is the first fixed sea based station with on-site continuous O2 and CO2 measurements and therefore yields valuable information about the CO2 uptake in coastal marine regions, specifically the North Sea. This paper presents the measurement station and the used methodologies in detail. In comparison to land-based stations, the data show low day-to-day variability, as they are practically free of nightly inversions as well as human influences, due to the station’s remoteness. Therefore, the data set collected at this measurement station serves directly as background data for the coastal northwest European region. Additionally, the first data are presented showing the seasonal cycle as expected during August 2008 through June 2009. Furthermore, some short-term O2 and CO2 signals are presented. The observations at the platform include several large and fast changing negative atmospheric O2 excursions without an accompanying change in the CO2 signal, which most likely indicate marine O2 uptake
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