COMET: a Lagrangian transport model for greenhouse gas emission estimation ? forward model technique and performance for methane

International audienceThe Lagrangian transport model COMET has been developed to evaluate emission estimates based on atmospheric concentration observations. This paper describes the model and its application in modelling the methane concentrations at the European stations Cabauw and Macehead. The COMET model captures in most cases both synoptic and diurnal variations of the concentrations as a function of time and in absolute size quite well. The explained variability by COMET of the mixed layer concentration for Cabauw varies from 50% to 84%; for all hourly observations in 2002 the explained variability is 71% with a RMSE of 112 ppb. The explained variability for Macehead is 48%. The most important model parameters were tested for their influence on model performance, but in general the model is not very sensitive to variations within acceptable limits. For a regionally and locally polluted continental site the COMET model shows only a small bias and a moderate random error, and therefore is considered to capture the influence of the sources on the concentration variations quite well. It is therefore concluded that inverse methods and more specifically the COMET model is suitable to be applied in deriving independent estimates of greenhouse gas emissions using Source-Receptor relationships

Greenhouse gas observations from Cabauw Tall Tower (1992–2010)

Since 1992 semi-continuous in-situ observations of greenhouse gas concentrations have been performed at the tall tower of Cabauw (4.927° E, 51.971° N, −0.7 m a.s.l.). Through 1992 up to now, the measurement system has been gradually extended and improved in precision, starting with CO<sub>2</sub> and CH<sub>4</sub> concentrations from 200 m a.g.l. in 1992 to vertical gradients at 4 levels of the gases CO<sub>2</sub>, CH<sub>4</sub>, SF<sub>6</sub>, N<sub>2</sub>O, H<sub>2</sub>, CO and gradients at 2 levels for <sup>222</sup>Rn. In this paper the measurement systems and measurement results are described for the main greenhouse gases and CO, for the whole period. The automatic measurement system now provides half-hourly concentration gradients with a precision better than or close to the WMO recommendations. <br><br> The observations at Cabauw show a complex pattern caused by the influence of sources and sinks from a large area around the tower with significant contributions of sources and sinks at distances up to 500–700 km. The concentration footprint area of Cabauw is one the most intensive and complex source areas of greenhouse gases in the world. Despite this, annual mean trends for the most important greenhouse gases, compatible with the values derived using the global network, can be reproduced from the measured concentrations at Cabauw over the entire measurement period, with a measured increase in the period 2000–2009 for CO<sub>2</sub> of 1.90 ± 0.1 ppm yr<sup>−1</sup>, for CH<sub>4</sub> of 4.4 ± 0.6 ppb yr<sup>−1</sup>, for N<sub>2</sub>O of 0.86 ± 0.04 ppb yr<sup>−1</sup>, and for SF<sub>6</sub> of 0.27 ± 0.01 ppt yr<sup>−1</sup>; for CO no significant trend could be detected. <br><br> The influences of strong local sources and sinks are reflected in the amplitude of the mean seasonal cycles observed at Cabauw, that are larger than the mean Northern Hemisphere average; Cabauw mean seasonal amplitude for CO<sub>2</sub> is 25–30 ppm (higher value for lower sampling levels). The observed CH<sub>4</sub> seasonal amplitude is 50–110 ppb. All gases except N<sub>2</sub>O show highest concentrations in winter and lower concentrations in summer, N<sub>2</sub>O observations show two additional concentration maxima in early summer and in autumn. <br><br> Seasonal cycles of the day-time mean concentrations show that surface concentrations or high elevation concentrations alone do not give a representative value for the boundary layer concentrations, especially in winter time, but that the vertical profile data along the mast can be used to construct a useful boundary layer mean value. The variability at Cabauw in the atmospheric concentrations of CO<sub>2</sub> on time scales of minutes to hours is several ppm and is much larger than the precision of the measurements (0.1 ppm). The diurnal and synoptical variability of the concentrations at Cabauw carry information on the sources and sinks in the footprint area of the mast, that will be useful in combination with inverse atmospheric transport model to verify emission estimates and improve ecosystem models. For this purpose a network of tall tower stations like Cabauw forms a very useful addition to the existing global observing network for greenhouse gases

High-risk HPV type-specific clearance rates in cervical screening

We assessed clearance rates of 14 high-risk human papillomavirus (hrHPV) types in hrHPV-positive women with normal cytology and borderline/mild dyskaryosis (BMD) in a population-based cervical screening cohort of 44 102 women. The 6-month hrHPV type-specific clearance rates, that is, clearance of the same type as detected at baseline, in women with normal and BMD smears were 43% (95% confidence interval (CI) 39–47) and 29% (95% CI 24–34), respectively. Corresponding 18-month clearance rates were markedly higher, namely 65% (95% CI 60–69) and 41% (95% CI 36–47), respectively. The lowest clearance rates in women with normal cytology were observed for HPV16, HPV18, HPV31, and HPV33. Significantly reduced 18-month clearance rates at a significance level of 1% were observed for HPV16 (49%, 95% CI 41–59) and HPV31 (50%, 95% CI 39–63) in women with normal cytology, and for HPV16 (19%, 95% CI 12–29) in women with BMD. Among women who did not clear hrHPV, women with HPV16 persistence displayed an increased detection rate of ⩾CIN3 (normal P<0.0001; BMD, P=0.005). The type-specific differences in clearance rates indicate the potential value of hrHPV genotyping in screening programs. Our data support close surveillance (i.e. referral directly, or within 6 months) of women with HPV16 and are inconclusive for surveillance of women with HPV18, HPV31, and HPV33. For the other hrHPV-positive women, it seems advisable to adopt a conservative management with a long waiting period, as hrHPV clearance is markedly higher after 18 months than after 6 months and the risk for ⩾CIN3 is low

Preferential risk of HPV16 for squamous cell carcinoma and of HPV18 for adenocarcinoma of the cervix compared to women with normal cytology in The Netherlands

We present the type-distribution of high-risk human papillomavirus (HPV) types in women with normal cytology (n=1467), adenocarcinoma in situ (ACIS) (n=61), adenocarcinoma (n=70), and squamous cell carcinoma (SCC) (n=83). Cervical adenocarcinoma and ACIS were significantly more frequently associated with HPV18 (ORMH 15.0; 95% CI 8.6–26.1 and 21.8; 95% CI 11.9–39.8, respectively) than normal cytology. Human papillomavirus16 was only associated with adenocarcinoma and ACIS after exclusion of HPV18-positive cases (ORMH 6.6; 95% CI 2.8–16.0 and 9.4; 95% CI 2.8–31.2, respectively). For SCC, HPV16 prevalence was elevated (ORMH 7.0; 95% CI 3.9–12.4) compared to cases with normal cytology, and HPV18 prevalence was only increased after exclusion of HPV16-positive cases (ORMH 4.3; 95% CI 1.6–11.6). These results suggest that HPV18 is mainly a risk factor for the development of adenocarcinoma whereas HPV16 is associated with both SCC and adenocarcinoma

Age-dependent prevalence of 14 high-risk HPV types in the Netherlands: implications for prophylactic vaccination and screening

We determined the prevalence of type-specific hrHPV infections in the Netherlands on cervical scrapes of 45 362 women aged 18–65 years. The overall hrHPV prevalence peaked at the age of 22 with peak prevalence of 24%. Each of the 14 hrHPV types decreased significantly with age (P-values between 0.0009 and 0.03). The proportion of HPV16 in hrHPV-positive infections also decreased with age (OR=0.76 (10-year scale), 95% CI=0.67–0.85), and a similar trend was observed for HPV16 when selecting hrHPV-positive women with cervical intraepithelial neoplasia grade 2 or worse (CIN2+) (OR=0.76, 95% CI=0.56–1.01). In women eligible for routine screening (age 29–61 years) with confirmed CIN2+, 65% was infected with HPV16 and/or HPV18. When HPV16/18-positive infections in women eligible for routine screening were discarded, the positive predictive value of cytology for the detection of CIN2+ decreased from 27 to 15%, the positive predictive value of hrHPV testing decreased from 26 to 15%, and the predictive value of a double-positive test (positive HPV test and a positive cytology) decreased from 54 to 41%. In women vaccinated against HPV16/18, screening remains important to detect cervical lesions caused by non-HPV16/18 types. To maintain a high-positive predictive value, screening algorithms must be carefully re-evaluated with regard to the screening modalities and length of the screening interval

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

The performance of eight fast-response methane (CH4) gas analysers suitable for eddy covariance flux measurements were tested at a grassland site near the Cabauw tall tower (Netherlands) during June 2012. The instruments were positioned close to each other in order to minimise the effect of varying turbulent conditions. The moderate CH4 fluxes observed at the location, of the order of 25 nmol m-2 s-1, provided a suitable signal for testing the instruments' performance. Generally, all analysers tested were able to quantify the concentration fluctuations at the frequency range relevant for turbulent exchange and were able to deliver high-quality data. The tested cavity ringdown spectrometer (CRDS) instruments from Picarro, models G2311-f and G1301-f, were superior to other CH4 analysers with respect to instrumental noise. As an open-path instrument susceptible to the effects of rain, the LI-COR LI-7700 achieved lower data coverage and also required larger density corrections; however, the system is especially useful for remote sites that are restricted in power availability. In this study the open-path LI-7700 results were compromised due to a data acquisition problem in our data-logging setup. Some of the older closed-path analysers tested do not measure H2O concentrations alongside CH4 (i.e. FMA1 and DLT-100 by Los Gatos Research) and this complicates data processing since the required corrections for dilution and spectroscopic interactions have to be based on external information. To overcome this issue, we used H2O mole fractions measured by other gas analysers, adjusted them with different methods and then applied them to correct the CH4 fluxes. Following this procedure we estimated a bias of the order of 0.1 g (CH4) m-2 (8% of the measured mean flux) in the processed and corrected CH4 fluxes on a monthly scale due to missing H2O concentration measurements. Finally, cumulative CH4 fluxes over 14 days from three closed-path gas analysers, G2311-f (Picarro Inc.), FGGA (Los Gatos Research) and FMA2 (Los Gatos Research), which were measuring H2O concentrations in addition to CH4, agreed within 3% (355–367 mg (CH4) m-2) and were not clearly different from each other, whereas the other instruments derived total fluxes which showed small but distinct differences (±10%, 330–399 mg (CH4) m-2)

A school-based intervention to reduce overweight and inactivity in children aged 6–12 years: study design of a randomized controlled trial

Background Effective interventions to prevent overweight and obesity in children are urgently needed especially in inner-city neighbourhoods where prevalence of overweight and inactivity among primary school children is high. A school based intervention was developed aiming at the reduction of overweight and inactivity in these children by addressing both behavioural and environmental determinants. Methods/design The main components of the intervention (Lekker Fit!) are the re-establishment of a professional physical education teacher; three (instead of two) PE classes per week; additional sport and play activities outside school hours; fitness testing; classroom education on healthy nutrition, active living and healthy lifestyle choices; and the involvement of parents. The effectiveness of the intervention is evaluated through a cluster randomized controlled trial in 20 primary schools among grades 3 through 8 (6–12 year olds). Primary outcome measures are BMI, waist circumference and fitness. Secondary outcome measures are assessed in a subgroup of grade 6–8 pupils (9–12 year olds) through classroom questionnaires and constitute of nutrition and physical activity behaviours and behavioural determinants. Multilevel regression analyses are used to study differences in outcomes between children in the intervention schools and in control schools, taking clustering of children within schools into account. Discussion Hypotheses are that the intervention results in a lower prevalence of children being overweight and an improved mean fitness score, in comparison with a control group where the intervention is not implemented. The results of our study will contribute to the discussion on the role of physical education and physical activity in the school curriculum. Trial registration [ISRCTN84383524

H2 vertical profiles in the continental boundary layer : Measurements at the Cabauw tall tower in the Netherlands

In-situ, quasi-continuous measurements of atmospheric hydrogen (H 2) have been performed since October 2007 at the Cabauw tall tower station in the Netherlands. Mole fractions of H2, CO and several greenhouse gases are determined simultaneously in air sampled successively at four heights, between 20 and 200 m above ground level. 222Rn measurements are performed in air sampled at 20 and 200 m. This H2 dataset represents the first in-situ, quasi-continuous long-term measurement series of vertical profiles of H2 in the lower continental boundary layer. Seasonal cycles are present at all heights in both H2 and CO, and their amplitude varies with the sampling height. The seasonality is evident in both the baseline values and in the short term (diurnal to synoptic time scales) variability, the latter being significantly larger during winter. The observed H2 short term signals and vertical gradients are in many cases well correlated to other species, especially to CO. On the other hand, H2 has at times a unique behaviour, due to its particular distribution of sources and sinks. Our estimation for the regional H2 soil uptake flux, using the radon tracer method, is (1.89 ± 0.26) × 10 5 g/(m2 h), significantly smaller than other recent results from Europe. H2/CO ratios of the traffic emissions computed from our data, with an average of 0.54 ± 0.07 mol:mol, are larger and more variable than estimated in some of the previous studies in Europe. This difference can be explained by a different driving regime, due to the frequent traffic jams in the influence area of Cabauw. The H2/CO ratios of the large scale pollution events have an average of 0.36 ± 0.05 mol:mol; these ratios were observed to slightly increase with sampling height, possibly due to a stronger influence of soil uptake at the lower sampling heights. © 2011 Author(s)

Defecation patterns in infants: a prospective cohort study

Data regarding prevalence and natural history of infant dyschezia, defined by the Rome III criteria as straining and crying for at least 10 min before successful passage of soft stools, are lacking. We aimed to investigate prevalence and natural history of infant dyschezia. In 2003, 124 youth healthcare doctors participated in a national study on defecation patterns of infants. Using standardised questionnaires and bowel diaries, these were recorded of infants aged 1, 3 and 9 months old. Out of 1292 infants, 46.4% had no gastrointestinal complaints. At 1 and 3 months old, 3.9% and 0.9% infants, respectively, fulfilled the Rome III criteria for infant dyschezia. However, at the same time points, parents of 17.3% and 6.5% of infants, respectively, reported symptoms preceding defecation while not strictly fulfilling the Rome III criteria ('modified Rome III criteria'). Dyschezia-like symptoms (Rome III criteria) were also reported in 0.9% of 9-month-old infants, with 5.7% having symptoms (modified Rome III criteria). Only 3/61 (4.9%) Rome III dyschezia infants and 1/306 (0.3%) infants with modified Rome III criteria at 1 or 3 months had symptoms fitting the diagnosis of infant functional constipation at 9 months old. The present definition of infant dyschezia seems too strict. We propose to widen the definition in terms of symptoms as well as age in order to better fit the appreciation of the parents. The prevalence of infant dyschezia declines with age. There seems to be no relation to the development of functional constipatio

The need for a supply of high quality organic vegetable seeds

Abstract -Production of high quality organic vegetable seeds encounters several challenges. Research is performed to support seed companies in producing vigorous and healthy organic vegetable seeds. Examples are provided with respect to research on seed vigour, determining critical control points to avoid disease transmission to the seeds, seed treatments with natural compounds, new seed sorting techniques and enhancement of the natural plant defence. It is noticed that the restrictions in EU regulation 2092/91 on organic production are at present blocking the use of promising natural and sustainable components for seed treatments