Tropospheric nitrogen dioxide inversions based on spectral measurements of scattered sunlight

This thesis describes the development of inversion methods for tropospheric nitrogen dioxide (NO2), based on ground based observations of scattered sunlight with themulti-axis differential optical absorption spectroscopy (MAX-DOAS) technique. NO2 is an atmospheric trace gas which, when present near the surface, is an important component of air pollution. On a global scale, fossil fuel combustion processes (power plants, automobiles) are the main source of NOx (=NO+NO2). NOx has a major impact on air quality, by its essential role in atmospheric photochemistry mechanisms: it influences tropospheric ozone formation as well as the levels of other oxidants (such as the hydroxyl and peroxy radicals), which catalyze the removal of species like carbonmonoxide, methane and other hydrocarbons from the atmosphere. In addition, NOx affects the formation of aerosols. Through the combination of these effects, tropospheric NOx reduces the radiative forcing, and therefore has a cooling effect on climate. A MAX-DOAS instrument measures wavelength spectra in the UV/Vis, with a resolution of less than one nanometer, in multiple viewing directions relative to the horizon. These measurements are analyzed with the differential optical absorption spectroscopy (DOAS) method, which can distinguish between the traces gases absorbing in a certain spectral window by making use of the fact that each gas has a unique spectral fingerprint. MAX-DOAS type of observations are complementary in two ways to other measuring techniques for NO2: Firstly in a temporal sense, relative to space-borne observations from the current generation of polar orbiting satellites, which frequently have no more than one observation per day. Secondly the MAX-DOAS observations are complementary in a spatial sense to in-situ monitors, which can only measure NO2 at the surface. MAX-DOAS instruments are especially suitable to measure tropospheric NO2 columns. This quantity is, more than NO2 concentrations measured at the surface, relevant for studies of transport and of trends in total amounts of tropospheric NO2. In this work it is investigated which information about the total amount and vertical distribution of tropospheric NO2 is contained in the MAX-DOAS measurements, and how this information can be extracted through inversemodeling (retrieval). What are the main error sources and which assumptions have to be made? Special attention is paid to aerosols, which have a large impact on the MAX-DOAS measurements. In addition, the developed retrieval methods are applied to a 14 month data set of MAXDOAS measurements performed in De Bilt. This data set was obtained as part of this research, and is unique for the Netherlands. The results are compared to satellite observations and to an air quality model. The first research described in this thesis (Chapter 3), focuses on the retrieval of tropospheric NO2 columns under clear sky conditions. A method was developed to derive differential air mass factors, by taking into account the effect of aerosols on the NO2 measurements. This was done in a new way: it was demonstrated that the aerosol optical thickness could be derived, for each elevation separately, by solely making use of MAX-DOAS measurements of relative intensity. It was assumed that all NO2 and aerosols were contained in a homogeneously mixed boundary layer of 1 km height. With this method, aerosol corrected air mass factors were derived for the elevations 4 degrees, 8 degrees and 16 degrees. Vertical columns could be derived for each elevation separately. Within this set of elevations, the 4 degrees elevation has the advantage of being most sensitive to trace gases in the boundary layer, but this viewing direction is also most sensitive to errors in the assumed aerosol and NO2 profile shape. With increasing elevation, the sensitivity to traces gases decreases, as well as errors due to wrong assumptions about the profile shapes. The retrieval method was applied to clear sky periods within the 14 month data set of MAX-DOAS observations performed in De Bilt. A comparison with AErosol RObotic NETwork (AERONET) observations of aerosol optical thickness showed good results: correlation of 0.85 was found, and a slope of the linear fit close to one. Comparison with space-borne retrievals of tropospheric NO2 columns retrieved by the OzoneMonitoring Instrument (OMI) shows on average reasonable results (correlations between 0.64 and 0.88 for different subsets), but individual comparisons can differ by more than a factor of two. This was attributed for the largest part to differences in spatial representativity, mostly in the horizontal direction, but also in the vertical. The second study (Chapter 4) focused on the question which information about the vertical distribution of aerosols and NO2 is contained in the MAX-DOAS observations. Vertical profile information derived from MAX-DOAS observations is not only relevant to improve the accuracy of the column retrieval, but it is needed as well in comparisons with other measurement techniques, such as satellite and lidar, and to derive NO2 surface concentrations, which are more directly related to air quality than vertical columns. Profile retrieval is challenging, since the profile information contained in MAX-DOAS measurements is known to be quite low. The topic is currently an active area of research in the MAXDOAS community: a range of approaches is being investigated, and no approach has yet emerged that can be considered a proven concept in all respects, partly because validation is a challenge as well. One of the main research questions addressed in this study, was the question if MAX-DOAS measurements can be used to distinguish between NO2 in the boundary layer and in the free troposphere. The basic retrieval model for tropospheric columns of the first study was expanded with two parameters for NO2, and one for aerosols: the height of the aerosol and NO2 layer above the surface was not longer assumed �fixed, and a second elevated NO2 layer was introduced at a fixed altitude in the free troposphere. In addition O4 measurements were used instead of relative intensity measurements, in order to better characterize the aerosol extinction profile in the boundary layer. Sensitivity studies were performed to investigate the retrieval accuracy for different noise levels, and for aerosol and NO2 profile shapes that were different from those assumed in the retrieval model. This led to the following conclusions: Firstly, if (in reality) NO2 is present above the boundary layer, and if the retrieval model allows an elevated NO2 layer at the same altitude as the real layer, then the amount of elevated NO2 can in principle be retrieved with reasonable accuracy. Secondly, for retrieval models which allow an elevated NO2 layer, tropospheric NO2 may also be retrieved when it is not present in reality. This may be the case for example when the aerosol andNO2 profiles shapes in the boundary layer are not well described by the retrieval model, or when the signal to noise level is low. Finally, despite the fact that MAX-DOAS measurements frequently do not contain more than two or three pieces of information to describe the NO2 profile, a retrieval model with only three free parameters will frequently be too rigid to perform accurate retrievals. In Chapter 6 of this thesis a more flexible approach is proposed. The profile retrieval approach was applied to MAX-DOAS measurements taken at the Cabauw Intercomparison campaign for NItrogen Dioxide measuring Instruments (CINDI). Comparison with independent observations of tropospheric NO2 columns from a lidar and NO2 surface concentrations from an in-situ monitor, showed on average good agreement (an average difference below 5 percent for both), but significant differences for individual cases. The third part of the research (Chapter 5) consisted of a comparison of tropospheric NO2 columns derived from the 14 month data set (that was also used in the first study) with tropospheric columns from the regional air quality model Lotos-Euros, which was run on a resolution of approximately 7x7 km. Whereas the comparison with satellite observations (Chapter 3) could only be performed under cloud free conditions, and at most two times per day, the comparison with the air quality model could be performed by making use of all MAX-DOAS observations. The total data volume therefore increased by a factor of 30, which improved the statistical significance, and allowed more detailed case studies. In order to analyze MAX-DOAS measurements under cloudy conditions, it was required to develop a third retrieval approach. This was based on MAX-DOAS observations at 30 degrees elevation (and the zenith reference), in order to be least sensitive to errors in the assumed NO2 profile shape, and to aerosols (the retrieval of which is difficult under cloudy conditions). Air mass factors were derived using information about the boundary layer height from a meteorological model. In addition, lidar observations of cloud bottom height were used. The comparison between Lotos-Euros and MAX-DOAS showed on average a good agreement (an average difference below 1 percent, and for daily averages over cloud free days a correlation of 0.8). The agreement found was surprising, especially when considering the fact that a bottom-up approach (the model) is compared to a top-down approach (the measurements). Furthermore, a remarkably good agreement was found for the tropospheric NO2 column averaged per sector of the wind direction. This indicates that the average tropospheric NO2 column that is measured in De Bilt, is not dominated by local sources, such as nearby highways with frequent traffic jams (such emissions are difficult to capture in the model), but rather by emissions in densely populated and industrial areas further away, e.g. the cities of Rotterdam, Amsterdam, Antwerp, Brussels and the German Ruhr area. It appears that tropospheric NO2 columns measured with MAX-DOAS can be used for validation of (high resolution) chemistry transport models in urban regions, and the same may be expected for satellite observations with a sufficiently small resolution. This is especially relevant because it is known that comparison between satellite and in-situ is problematic in urban regions (due to the large difference in spatial representativity). No observations were performed in summer months. It may however be expected that because of the shorter lifetime of NO2 in summer, nearby sources would have a larger relative impact on the MAX-DOAS observations, and therefore lead to less agreement with the model than as found in this study. For individual comparisons on an hourly and day-to-day basis, observed differences could be substantial. This is mainly attributed to the fact that within the model actual emissions cannot be described on a high enough spatial and temporal resolution. In addition, differences could be large for example when the observed wind direction or wind speed was different from that in the model, or in the weekend: Observations showed on average a clear decrease in the weekend, compared to the rest of the week, whereas the model showed a less pronounced weekly cycle. The three studies described in this work lead to the following general conclusions about MAX-DOAS observations of NO2: Firstly, it has been demonstrated that long-term MAX-DOAS observations of tropospheric columns are particularly suitable for validation of space-borne observations and air quality models. When averaged over long-enough periods, patterns show up (e.g. as a function of time, wind direction, or another quantity) that would not be seen for individual comparisons, or not even for a few months of observations, due to differences in representativity and limited accuracy. Thorough satellite and model validation therefore requires a large network of MAX-DOAS sites, on locations with a variety of conditions with respect to NO2 and aerosols. There is currently no other ground based method that can provide automated tropospheric NO2 column observations for such a low cost per observation. Secondly, it is concluded that with a simple algorithm, based on a high viewing elevation (e.g. 30 degrees), tropospheric NO2 columns can be retrieved with reasonable accuracy, for a large number of different aerosol and NO2 scenarios, and without strong dependence on a-priori assumptions. With respect to NO2 profile retrieval, the situation is different: due to the many aspects that influence the measurements, the required accuracy, and the relatively low information content, the accuracy of individual retrievals is generally not very high (especially for the free troposphere), and depends strongly on a-priori assumptions, as well as on the atmospheric conditions at the time of measurement. To make optimal use of the information content, it is important that the profile shape parametrization is highly flexible for the lowest 1-2 kilometers of the atmosphere. Profile retrieval accuracy is highest and depends least on a-priori assumptions for cloud free situations, when the aerosol optical thickness is low, when the NO2 is located in a boundary layer of which the top lies between approximately 400 m and 1.5 km altitude, and when in addition the MAX-DOAS instrument is aimed away from the sun. Finally, it is concluded that more validation of MAX-DOAS retrieval methods is needed. This requires long-term observations in the presence of other instruments that can be used for comparisons, such as those present at the CINDI campaign. Such comparisons should be performed in various seasons and under various conditions with respect to the abundance of aerosols and NO2

Tropospheric nitrogen dioxide inversions based on spectral measurements of scattered sunlight

This thesis describes the development of inversion methods for tropospheric nitrogen dioxide (NO2), based on ground based observations of scattered sunlight with themulti-axis differential optical absorption spectroscopy (MAX-DOAS) technique. NO2 is an atmospheric trace gas which, when present near the surface, is an important component of air pollution. On a global scale, fossil fuel combustion processes (power plants, automobiles) are the main source of NOx (=NO+NO2). NOx has a major impact on air quality, by its essential role in atmospheric photochemistry mechanisms: it influences tropospheric ozone formation as well as the levels of other oxidants (such as the hydroxyl and peroxy radicals), which catalyze the removal of species like carbonmonoxide, methane and other hydrocarbons from the atmosphere. In addition, NOx affects the formation of aerosols. Through the combination of these effects, tropospheric NOx reduces the radiative forcing, and therefore has a cooling effect on climate. A MAX-DOAS instrument measures wavelength spectra in the UV/Vis, with a resolution of less than one nanometer, in multiple viewing directions relative to the horizon. These measurements are analyzed with the differential optical absorption spectroscopy (DOAS) method, which can distinguish between the traces gases absorbing in a certain spectral window by making use of the fact that each gas has a unique spectral fingerprint. MAX-DOAS type of observations are complementary in two ways to other measuring techniques for NO2: Firstly in a temporal sense, relative to space-borne observations from the current generation of polar orbiting satellites, which frequently have no more than one observation per day. Secondly the MAX-DOAS observations are complementary in a spatial sense to in-situ monitors, which can only measure NO2 at the surface. MAX-DOAS instruments are especially suitable to measure tropospheric NO2 columns. This quantity is, more than NO2 concentrations measured at the surface, relevant for studies of transport and of trends in total amounts of tropospheric NO2. In this work it is investigated which information about the total amount and vertical distribution of tropospheric NO2 is contained in the MAX-DOAS measurements, and how this information can be extracted through inversemodeling (retrieval). What are the main error sources and which assumptions have to be made? Special attention is paid to aerosols, which have a large impact on the MAX-DOAS measurements. In addition, the developed retrieval methods are applied to a 14 month data set of MAXDOAS measurements performed in De Bilt. This data set was obtained as part of this research, and is unique for the Netherlands. The results are compared to satellite observations and to an air quality model. The first research described in this thesis (Chapter 3), focuses on the retrieval of tropospheric NO2 columns under clear sky conditions. A method was developed to derive differential air mass factors, by taking into account the effect of aerosols on the NO2 measurements. This was done in a new way: it was demonstrated that the aerosol optical thickness could be derived, for each elevation separately, by solely making use of MAX-DOAS measurements of relative intensity. It was assumed that all NO2 and aerosols were contained in a homogeneously mixed boundary layer of 1 km height. With this method, aerosol corrected air mass factors were derived for the elevations 4 degrees, 8 degrees and 16 degrees. Vertical columns could be derived for each elevation separately. Within this set of elevations, the 4 degrees elevation has the advantage of being most sensitive to trace gases in the boundary layer, but this viewing direction is also most sensitive to errors in the assumed aerosol and NO2 profile shape. With increasing elevation, the sensitivity to traces gases decreases, as well as errors due to wrong assumptions about the profile shapes. The retrieval method was applied to clear sky periods within the 14 month data set of MAX-DOAS observations performed in De Bilt. A comparison with AErosol RObotic NETwork (AERONET) observations of aerosol optical thickness showed good results: correlation of 0.85 was found, and a slope of the linear fit close to one. Comparison with space-borne retrievals of tropospheric NO2 columns retrieved by the OzoneMonitoring Instrument (OMI) shows on average reasonable results (correlations between 0.64 and 0.88 for different subsets), but individual comparisons can differ by more than a factor of two. This was attributed for the largest part to differences in spatial representativity, mostly in the horizontal direction, but also in the vertical. The second study (Chapter 4) focused on the question which information about the vertical distribution of aerosols and NO2 is contained in the MAX-DOAS observations. Vertical profile information derived from MAX-DOAS observations is not only relevant to improve the accuracy of the column retrieval, but it is needed as well in comparisons with other measurement techniques, such as satellite and lidar, and to derive NO2 surface concentrations, which are more directly related to air quality than vertical columns. Profile retrieval is challenging, since the profile information contained in MAX-DOAS measurements is known to be quite low. The topic is currently an active area of research in the MAXDOAS community: a range of approaches is being investigated, and no approach has yet emerged that can be considered a proven concept in all respects, partly because validation is a challenge as well. One of the main research questions addressed in this study, was the question if MAX-DOAS measurements can be used to distinguish between NO2 in the boundary layer and in the free troposphere. The basic retrieval model for tropospheric columns of the first study was expanded with two parameters for NO2, and one for aerosols: the height of the aerosol and NO2 layer above the surface was not longer assumed �fixed, and a second elevated NO2 layer was introduced at a fixed altitude in the free troposphere. In addition O4 measurements were used instead of relative intensity measurements, in order to better characterize the aerosol extinction profile in the boundary layer. Sensitivity studies were performed to investigate the retrieval accuracy for different noise levels, and for aerosol and NO2 profile shapes that were different from those assumed in the retrieval model. This led to the following conclusions: Firstly, if (in reality) NO2 is present above the boundary layer, and if the retrieval model allows an elevated NO2 layer at the same altitude as the real layer, then the amount of elevated NO2 can in principle be retrieved with reasonable accuracy. Secondly, for retrieval models which allow an elevated NO2 layer, tropospheric NO2 may also be retrieved when it is not present in reality. This may be the case for example when the aerosol andNO2 profiles shapes in the boundary layer are not well described by the retrieval model, or when the signal to noise level is low. Finally, despite the fact that MAX-DOAS measurements frequently do not contain more than two or three pieces of information to describe the NO2 profile, a retrieval model with only three free parameters will frequently be too rigid to perform accurate retrievals. In Chapter 6 of this thesis a more flexible approach is proposed. The profile retrieval approach was applied to MAX-DOAS measurements taken at the Cabauw Intercomparison campaign for NItrogen Dioxide measuring Instruments (CINDI). Comparison with independent observations of tropospheric NO2 columns from a lidar and NO2 surface concentrations from an in-situ monitor, showed on average good agreement (an average difference below 5 percent for both), but significant differences for individual cases. The third part of the research (Chapter 5) consisted of a comparison of tropospheric NO2 columns derived from the 14 month data set (that was also used in the first study) with tropospheric columns from the regional air quality model Lotos-Euros, which was run on a resolution of approximately 7x7 km. Whereas the comparison with satellite observations (Chapter 3) could only be performed under cloud free conditions, and at most two times per day, the comparison with the air quality model could be performed by making use of all MAX-DOAS observations. The total data volume therefore increased by a factor of 30, which improved the statistical significance, and allowed more detailed case studies. In order to analyze MAX-DOAS measurements under cloudy conditions, it was required to develop a third retrieval approach. This was based on MAX-DOAS observations at 30 degrees elevation (and the zenith reference), in order to be least sensitive to errors in the assumed NO2 profile shape, and to aerosols (the retrieval of which is difficult under cloudy conditions). Air mass factors were derived using information about the boundary layer height from a meteorological model. In addition, lidar observations of cloud bottom height were used. The comparison between Lotos-Euros and MAX-DOAS showed on average a good agreement (an average difference below 1 percent, and for daily averages over cloud free days a correlation of 0.8). The agreement found was surprising, especially when considering the fact that a bottom-up approach (the model) is compared to a top-down approach (the measurements). Furthermore, a remarkably good agreement was found for the tropospheric NO2 column averaged per sector of the wind direction. This indicates that the average tropospheric NO2 column that is measured in De Bilt, is not dominated by local sources, such as nearby highways with frequent traffic jams (such emissions are difficult to capture in the model), but rather by emissions in densely populated and industrial areas further away, e.g. the cities of Rotterdam, Amsterdam, Antwerp, Brussels and the German Ruhr area. It appears that tropospheric NO2 columns measured with MAX-DOAS can be used for validation of (high resolution) chemistry transport models in urban regions, and the same may be expected for satellite observations with a sufficiently small resolution. This is especially relevant because it is known that comparison between satellite and in-situ is problematic in urban regions (due to the large difference in spatial representativity). No observations were performed in summer months. It may however be expected that because of the shorter lifetime of NO2 in summer, nearby sources would have a larger relative impact on the MAX-DOAS observations, and therefore lead to less agreement with the model than as found in this study. For individual comparisons on an hourly and day-to-day basis, observed differences could be substantial. This is mainly attributed to the fact that within the model actual emissions cannot be described on a high enough spatial and temporal resolution. In addition, differences could be large for example when the observed wind direction or wind speed was different from that in the model, or in the weekend: Observations showed on average a clear decrease in the weekend, compared to the rest of the week, whereas the model showed a less pronounced weekly cycle. The three studies described in this work lead to the following general conclusions about MAX-DOAS observations of NO2: Firstly, it has been demonstrated that long-term MAX-DOAS observations of tropospheric columns are particularly suitable for validation of space-borne observations and air quality models. When averaged over long-enough periods, patterns show up (e.g. as a function of time, wind direction, or another quantity) that would not be seen for individual comparisons, or not even for a few months of observations, due to differences in representativity and limited accuracy. Thorough satellite and model validation therefore requires a large network of MAX-DOAS sites, on locations with a variety of conditions with respect to NO2 and aerosols. There is currently no other ground based method that can provide automated tropospheric NO2 column observations for such a low cost per observation. Secondly, it is concluded that with a simple algorithm, based on a high viewing elevation (e.g. 30 degrees), tropospheric NO2 columns can be retrieved with reasonable accuracy, for a large number of different aerosol and NO2 scenarios, and without strong dependence on a-priori assumptions. With respect to NO2 profile retrieval, the situation is different: due to the many aspects that influence the measurements, the required accuracy, and the relatively low information content, the accuracy of individual retrievals is generally not very high (especially for the free troposphere), and depends strongly on a-priori assumptions, as well as on the atmospheric conditions at the time of measurement. To make optimal use of the information content, it is important that the profile shape parametrization is highly flexible for the lowest 1-2 kilometers of the atmosphere. Profile retrieval accuracy is highest and depends least on a-priori assumptions for cloud free situations, when the aerosol optical thickness is low, when the NO2 is located in a boundary layer of which the top lies between approximately 400 m and 1.5 km altitude, and when in addition the MAX-DOAS instrument is aimed away from the sun. Finally, it is concluded that more validation of MAX-DOAS retrieval methods is needed. This requires long-term observations in the presence of other instruments that can be used for comparisons, such as those present at the CINDI campaign. Such comparisons should be performed in various seasons and under various conditions with respect to the abundance of aerosols and NO2

Decision aids to improve informed decision-making in pregnancy care: a systematic review

Rapid development in health care has resulted in an increasing number of screening and treatment options. Consequently, there is an urgency to provide people with relevant information about benefits and risks of healthcare options in an unbiased way. Decision aids help people to make decisions by providing unbiased non-directive research evidence about all treatment options. To determine the effectiveness of decision aids to improve informed decision making in pregnancy care. We searched MEDLINE (1953-2011), EMBASE (1980-2011), CENTRAL (CENTRAL, the Cochrane Library; 2011, Issue 4), Psycinfo (1806-2011) and Research Registers of ongoing trials (www.clinicaltrials.gov, www.controlled-trials.com). We included randomised controlled trials comparing decision aids in addition to standard care. The study population needed to be pregnant women making actual decisions concerning their pregnancy. Two independent researchers extracted data on quality of the randomised controlled trial (GRADE criteria), quality of the decision aid (IPDAS criteria), and outcome measures. Data analysis was undertaken by assessing group differences at first follow up after the interventions. Ten randomised controlled trials could be included. Pooled analyses showed that decision aids significantly increased knowledge, (weighted mean difference 11.06, 95% confidence interval 4.85-17.27), decreased decisional conflict scores (weighted mean difference -3.66, 95% confidence interval -6.65 to -0.68) and decreased anxiety (weighted mean difference -1.56, 95% confidence interval -2.75 to -0.43). Our systematic review showed the positive effect of decision aids on informed decision making in pregnancy care. Future studies should focus on increasing the uptake of decision aids in clinical practice by identifying barriers and facilitators to implementatio

Haalbaarheid van de ontwerp-GHP-code voor varkensbedrijven

In 1998 is door de Productschappen Vee, Vlees en Eieren een ontwerpcode 'Goede Hygiënische Praktijken voor het exploiteren van varkenshouderijen 1998' (ontwerp-GHP-code) opgesteld. Voordat de code definitief kan worden gemaakt, wil de sector duidelijkheid over de haalbaarheid ervan voor bedrijven

Nitrogen Oxide Emissions from U.S. Oil and Gas Production: Recent Trends and Source Attribution

U.S. oil and natural gas production volumes have grown by up to 100% in key production areas between January 2017 and August 2019. Here we show that recent trends are visible from space and can be attributed to drilling, production, and gas flaring activities. By using oil and gas activity data as predictors in a multivariate regression to satellite measurements of tropospheric NO2 columns, observed changes in NO2 over time could be attributed to NOx emissions associated with drilling, production and gas flaring for three select regions: the Permian, Bakken, and Eagle Ford basins. We find that drilling had been the dominant NOx source contributing around 80% before the downturn in drilling activity in 2015. Thereafter, NOx contributions from drilling activities and combined production and flaring activities are similar. Comparison of our topâ down source attribution with a bottomâ up fuelâ based oil and gas NOx emission inventory shows agreement within error margins.Plain Language SummaryU.S. oil and natural gas production volumes have grown by up to 100% in key production areas between January 2017 and August 2019. Here we show that recent trends are visible from space as increases in NO2, an air pollutant that is released from combustion engines associated with the oil and gas industry. For three select regions, the Permian (TX and NM), Bakken (ND), and Eagle Ford (TX) basins, we report that the trend in NO2 columns over time can be explained by a combination of drilling activity, production numbers, and flared gas volume, which allows us to quantify the contributions from these sources to the total NOx (= NO + NO2) emissions from these areas. We find that drilling had been the dominant NOx source contributing around 80% before the downturn in drilling activity in 2015. But now, NOx contributions from drilling activities and combined production and flaring activities are similar. Both Permian and Bakken oil and gas production volumes are at an allâ time high and if current growth rates continue in the Eagle Ford basin, maximum production volumes will be exceeded in about 1 year.Key PointsRecent increases in U.S. oil and gas production are seen from space as increased tropospheric NO2 columns and increased gas flaringChanges in NO2 over time can be attributed to oil and gas NOx emissions associated with drilling, production, and gas flaring activitiesTopâ down and bottomâ up source attributions agree that drilling and, to a lesser extent, production are the main sources of NOx emissionsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153757/1/grl60007_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153757/2/grl60007.pd

Haalbaarheid van de ontwerp-GHP-code voor varkensbedrijven

Medio 1995 is onder leiding van de Productschappen voor Vee, Vlees en Eieren (PVE) een GHP (Goede Hygiënische Praktijken)-code opgesteld voor varkensbedrijven en transportbedrijven. Deze code is in nauw overleg met bedrijfsleven en overheid tot stand gekomen. De code heeft betrekking op de inrichting, bedrijfsvoering en administratie van het varkens- en transportbedrijf. De landelijke minimumeisen voor varkenshouderijbedrijven zijn hierin verwerkt. De code is sinds die tijd, onder andere naar aanleiding van de varkenspestproblematiek, verder uitgewerkt en voor varkensbedrijven neergelegd in een ontwerp: “Goede Hygiënische Praktijken voor het exploiteren van varkenshouderijen 1998”. Voordat de code definitief kan worden gemaakt wil de sector duidelijkheid over de praktijksituatie op dit moment en een indruk van de haalbaarheid van invoering ervan op varkensbedrijven. Het Praktijkonderzoek Varkenshouderij heeft van de PVE de opdracht gekregen een onderzoek uit te voeren, met als doel inzicht te verkrijgen in hoeverre de verschillende voorschriften van de ontwerp-GHP-code nu al in de praktijk worden toegepast en welke consequenties een verplichte invoer ervan voor praktijkbedrijven zou hebben qua uitvoerbaarheid, kosten en benodigde investeringe

Effectiveness of vaginal breech birth training strategies: an integrative review of the literature

Background: The safety of vaginal breech birth depends on the skill of the attendant. The objective of this review was to identify, synthesise and report the findings of evaluated breech birth training strategies. Methods: A systematic search of the following on-line databases: Medline, CINAHL Plus, PsychINFO, EBM Reviews/Cochrane Library, EMBASE, Maternity and Infant Care, and Pubmed, using a structured search strategy. Studies were included in the review if they evaluated the efficacy of a breech birth training programme or particular strategies, including obstetric emergency training evaluations that reported differentiated outcomes for breech. Out of 1040 original citings, 303 full-text articles were assessed for eligibility, and 17 methodologically diverse studies met the inclusion criteria. A data collection form was used to extract relevant information. Data were synthesised using an evaluation levels framework, including reaction, learning (subjective and objective assessment) and behavioural change. Results: No evaluations included clinical outcome data. Improvements in selfassessed skill and confidence were not associated with improvements in objective assessments or behavioural change. Inclusion of breech birth as part of an obstetric emergencies training package without support in practice was negatively associated with subsequent attendance at vaginal breech births. Conclusions: Due to the heterogeneity of the studies available, and the lack of evidence concerning neonatal or maternal outcomes, no conclusive practice recommendations can be made. However, the studies reviewed suggest that vaginal breech birth training may be enhanced by reflection, repetition and experienced clinical support in practice. Further evaluation studies should prioritise clinical outcome data

Atosiban versus fenoterol as a uterine relaxant for external cephalic version: randomised controlled trial

Objective To compare the effectiveness of the oxytocin receptor antagonist atosiban with the beta mimetic fenoterol as uterine relaxants in women undergoing external cephalic version (ECV) for breech presentation. Design Multicentre, open label, randomised controlled trial. Setting Eight hospitals in the Netherlands, August 2009 to May 2014. Participants 830 women with a singleton fetus in breech presentation and a gestational age of more than 34 weeks were randomly allocated in a 1:1 ratio to either 6.75 mg atosiban (n=416) or 40 μg fenoterol (n=414) intravenously for uterine relaxation before ECV. Main outcome measures The primary outcome measures were a fetus in cephalic position 30 minutes after the procedure and cephalic presentation at delivery. Secondary outcome measures were mode of delivery, incidence of fetal and maternal complications, and drug related adverse events. All analyses were done on an intention-to-treat basis. Results Cephalic position 30 minutes after ECV occurred significantly less in the atosiban group than in the fenoterol group (34% v 40%, relative risk 0.73, 95% confidence interval 0.55 to 0.93). Presentation at birth was cephalic in 35% (n=139) of the atosiban group and 40% (n=166) of the fenoterol group (0.86, 0.72 to 1.03), and caesarean delivery was performed in 60% (n=240) of women in the atosiban group and 55% (n=218) in the fenoterol group (1.09, 0.96 to 1.20). No significant differences were found in neonatal outcomes or drug related adverse events. Conclusions In women undergoing ECV for breech presentation, uterine relaxation with fenoterol increases the rate of cephalic presentation 30 minutes after the procedure. No statistically significant difference was found for cephalic presentation at delivery