Dairy production systems are often criticized as being major emitters of greenhouse gases (GHG). In this context, the extension of the length of the productive life of dairy cows is gaining interest ...as a potential GHG mitigation option. In the present study, we investigated cow and system GHG emission intensity and profitability based on data from 30 dairy cows of different productive lifetime fed either no or limited amounts of concentrate. Detailed information concerning productivity, feeding and individual enteric methane emissions of the individuals was available from a controlled experiment and herd book databases. A simplified GHG balance was calculated for each animal based on the milk produced at the time of the experiment and for their entire lifetime milk production. For the lifetime production, we also included the emissions arising from potential beef produced by fattening the offspring of the dairy cows. This accounted for the effect that changes in the length of productive life will affect the replacement rate and thus the number of calves that can be used for beef production. Profitability was assessed by calculating revenues and full economic costs for the cows in the data set. Both emission intensity and profitability were most favourable in cows with long productive life, whereas cows that had not finished their first lactation performed particularly unfavourably with regard to their emissions per unit of product and rearing costs were mostly not repaid. Including the potential beef production, GHG emissions in relation to total production of animal protein also decreased with age, but the overall variability was greater, as the individual cow history (lifetime milk yield, twin births, stillbirths, etc.) added further sources of variation. The present results show that increasing the length of productive life of dairy cows is a viable way to reduce the climate impact and to improve profitability of dairy production.
Despite their importance, current scientific knowledge on non-exhaust emissions by road traffic is scarce, severely hampering a reliable description of these particles in atmospheric dispersion ...models. Consequently, it is still very difficult to convincingly evaluate population exposure to traffic-related components in large cities, especially given the significant variation in traffic-related air pollution concentrations on a small scale (e.g. within 100–1000 m of a busy road). One factor contributing to this uncertainty is the lack of a reliable emission estimate for vehicular non-exhaust emissions. Emissions vary from location to location due to the impact of climate, road surface characteristics and traffic conditions, but the geographical coverage for which Emission Factors are available and the amount of knowledge regarding the variability within a city environment are very limited.
The present study investigates the spatial and chemical properties of the strength of the emission source (road dust particles below 10 μm) in three contrasting European urban environments: two Spanish cities (Barcelona and Girona), and a Swiss city (Zürich). Loadings of road dust <10 μm from the 8 sites sampled in Zürich ranged from 0.2 to 1.3 mg m
−2, the lowest loadings of the study. The minimum loadings in Girona (Spain) were as high as the maximum in Zürich, with a range of 1.3–7.1 mg m
−2. By far the most polluted site in terms of road dust <10 μm mass loading is Barcelona (Spain), where a range of 3.7–23.1 mg m
−2 was recorded in the city center samples. Four main sources were found to drive the variability of road dust particles <10 μm: Mineral (road wear and urban dust generated mostly by construction emissions), Motor Exhaust, Brake wear and Tire wear. Road wear/Mineral is the dominating source in Spanish cities (∼60%), but represents only 30% of road dust loadings in Zürich where contributions are more equally distributed among the four main sources of road dust. Regardless of the city categories loadings of OC, EC, Fe, Cr, Mn, Cu, Zn, Mo, Sn, Sb, Cs, Ba, W, Pb and Bi (μg m
−2) increase by a factor of 1.2–2.2, from streets with <15 kveh to streets with 15–40 kveh day
−1. At highly trafficked sites (>40 kveh day
−1) loadings were again increasing by a further factor of 2.6–10.1. Finally, agreement was found between the composition of sampled materials and the composition (available from literature) of PM10 material emitted by vehicles via resuspension (both in Zürich and Barcelona). This permitted to find a relationship, potentially able to calculate emission factors from known amount of deposited pollutants in those cities/environment where no real-world EFs are available from literature.
► In this study we investigate loadings and sources of inhalable (<10 μm) road dust particles, in three European cities. ► Dry Mediterranean cities showed higher particles loadings with respect to a Central European city. ► The road wear/Mineral source was found to be dominant in Spanish cities. ► In the Swiss city contributions from different sources are similar. ► Loadings of OC, EC, Fe, Cr, Mn, Cu, Zn, Mo, Sn, Sb, Cs, Ba, W, Pb and Bi were found to increase with traffic intensity.
Nitrous acid measurements were carried out during the MEGAPOLI summer and winter field campaigns at SIRTA observatory in Paris surroundings. Highly variable HONO levels were observed during the ...campaigns, ranging from 10 ppt to 500 ppt in summer and from 10 ppt to 1.7 ppb in winter. Significant HONO mixing ratios have also been measured during daytime hours, comprised between some tenth of ppt and 200 ppt for the summer campaign and between few ppt and 1 ppb for the winter campaign. Ancillary measurements, such as NOx, O3, photolysis frequencies, meteorological parameters (pressure, temperature, relative humidity, wind speed and wind direction), black carbon concentration, total aerosol surface area, boundary layer height and soil moisture, were conducted during both campaigns. In addition, for the summer period, OH radical measurements were made with a CIMS (Chemical Ionisation Mass Spectrometer). This large dataset has been used to investigate the HONO budget in a suburban environment. To do so, calculations of HONO concentrations using PhotoStationary State (PSS) approach have been performed, for daytime hours. The comparison of these calculations with measured HONO concentrations revealed an underestimation of the calculations making evident a missing source term for both campaigns. This unknown HONO source exhibits a bell-shaped like average diurnal profile with a maximum around noon of approximately 0.7 ppb h−1 and 0.25 ppb h−1, during summer and winter respectively. This source is the main HONO source during daytime hours for both campaigns. In both cases, this source shows a slight positive correlation with J(NO2) and the product between J(NO2) and soil moisture. This original approach had, thus, indicated that this missing source is photolytic and might be heterogeneous occurring at ground surface and involving water content available on the ground.
Trace element measurements in PM10-2.5, PM2.5-1.0 and PM1.0-0.3 aerosol were performed with 2 h time resolution at kerbside, urban background and rural sites during the ClearfLo winter 2012 campaign ...in London. The environment-dependent variability of emissions was characterized using the Multilinear Engine implementation of the positive matrix factorization model, conducted on data sets comprising all three sites but segregated by size. Combining the sites enabled separation of sources with high temporal covariance but significant spatial variability. Separation of sizes improved source resolution by preventing sources occurring in only a single size fraction from having too small a contribution for the model to resolve. Anchor profiles were retrieved internally by analysing data subsets, and these profiles were used in the analyses of the complete data sets of all sites for enhanced source apportionment. A total of nine different factors were resolved (notable elements in brackets): in PM10-2.5, brake wear (Cu, Zr, Sb, Ba), other traffic-related (Fe), resuspended dust (Si, Ca), sea/road salt (Cl), aged sea salt (Na, Mg) and industrial (Cr, Ni); in PM2.5-1.0, brake wear, other traffic-related, resuspended dust, sea/road salt, aged sea salt and S-rich (S); and in PM1.0-0.3, traffic-related (Fe, Cu, Zr, Sb, Ba), resuspended dust, sea/road salt, aged sea salt, reacted Cl (Cl), S-rich and solid fuel (K, Pb). Human activities enhance the kerb-to-rural concentration gradients of coarse aged sea salt, typically considered to have a natural source, by 1.7-2.2. These site-dependent concentration differences reflect the effect of local resuspension processes in London. The anthropogenically influenced factors traffic (brake wear and other traffic-related processes), dust and sea/road salt provide further kerb-to-rural concentration enhancements by direct source emissions by a factor of 3.5-12.7. The traffic and dust factors are mainly emitted in PM10-2.5 and show strong diurnal variations with concentrations up to 4 times higher during rush hour than during night-time. Regionally influenced S-rich and solid fuel factors, occurring primarily in PM1.0-0.3, have negligible resuspension influences, and concentrations are similar throughout the day and across the regions.
Size and time-resolved roadside enrichments of atmospheric particulate pollutants in PM10 were detected and quantified in a Mediterranean urban environment (Barcelona, Spain). Simultaneous data from ...one urban background (UB), one traffic (T) and one heavy traffic (HT) location were analysed, and roadside PM10 enrichments (RE) in a number of elements arising from vehicular emissions were calculated. Tracers of primary traffic emissions (EC, Fe, Ba, Cu, Sb, Cr, Sn) showed the largest REs (>70%). Other traffic tracers (Zr, Cd) showed lower but still consistent REs (25–40%), similar to those obtained for mineral matter resulting from road dust resuspension (Ca, La, Ce, Ti, Ga, Sr, 30–40%). The sum of primary and secondary organic carbon showed a RE of 41%, with contributions of secondary OC (SOC) to total OC ranging from 46% at the HT site, 63% at the T site, and 78% in the UB. Finally, other trace elements (As, Co, Bi) showed unexpected but consistent roadside enrichments (23% up to 69%), suggesting a link to traffic emissions even though the emission process is unclear. Hourly-resolved PM speciation data proved to be a highly resourceful tool to determine the source origin of atmospheric pollutants in urban environments. At the HT site, up to 62% of fine Mn was attributable to industrial plumes, whereas coarse Mn levels were mainly attributed to traffic. Similarly, even though Zn showed on average no roadside enrichment and thus was classified as industrial, the hourly-resolved data proved that at least 15% of coarse Zn may be attributed to road traffic emissions. In addition, our results indicate that secondary nitrate formation occurs within the city-scale, even in the absence of long atmospheric residence times or long-range atmospheric transport processes. Characteristic tracer ratios of road traffic emissions were identified: Cu/Sb = 6.8–8.0, Cu/Sn = 4.7–5.4 and Sn/Sb = 1.5.
Recent studies have shown clear contributions of non-exhaust emissions to the traffic related PM10 load of the ambient air. These emissions consist of particles produced by abrasion from brakes, road ...wear, tire wear, as well as vehicle induced resuspension of deposited road dust. The main scope of the presented work was to identify and quantify the non-exhaust fraction of traffic related PM10 for two roadside locations in Switzerland with different traffic regimes. The two investigated locations, an urban street canyon with heavily congested traffic and an interurban freeway, are considered as being typical for Central Europe. Mass-relevant contributions from abrasion particles and resuspended road dust mainly originated from particles in the size range 1–10 μm. The results showed a major influence of vehicle induced resuspension of road dust. In the street canyon, the traffic related PM10 emissions (LDV: 24 ± 8 mg km
−1 vehicle
−1, HDV: 498 ± 86 mg km
−1 vehicle
−1) were assigned to 21% brake wear, 38% resuspended road dust and 41% exhaust emissions. Along the freeway (LDV: 50 ± 13 mg km
−1 vehicle
−1, HDV: 288 ± 72 mg km
−1 vehicle
−1), respective contributions were 3% brake wear, 56% resuspended road dust and 41% exhaust emissions. There was no indication for relevant contributions from tire wear and abrasion from undamaged pavements.
Chemical Ionisation Mass Spectrometer measurements of hydroxyl radical (OH) and the sum of hydroperoxy and organic peroxy (HO2+RO2) radicals were conducted during the MEGAPOLI summer field campaign ...at the SIRTA observatory near Paris, France, in July 2009. OH and (HO2+RO2) showed a typical diurnal variation with averaged daytime maxima values around 5×106 and 1.2×108 molecule cm−3, respectively. Simultaneously, a large number of ancillary measurements, such as NOx, O3, HONO, HCHO and other VOCs were also conducted. These data provide an opportunity to assess our understanding of the radical chemistry in a suburban environment by comparing the radical observations to calculations. First, OH mixing ratios were estimated by a simple Photo Stationary State (PSS) calculation. PSS calculations overestimate the OH mixing ratio by 50%, especially at NOx mixing ratios lower than 10 ppb, suggesting that some loss processes were missing in the calculation at low NOx. Then, a photochemical box model simulation based on the Master Chemical Mechanism (MCM) and constrained by ancillary measurements was run to calculate radical concentrations. Three different modelling procedures were tested, varying the way the unconstrained secondary species were estimated, to cope with the unavoidable lack of their measurements. They led to significant differences in simulated radical concentrations. OH and (HO2+RO2) concentrations estimated by two selected model version were compared with measurements. These versions of the model were chosen because they lead, respectively, to the higher and lower simulated radical concentrations and are thus the two extremes versions. The box model showed better results than PSS calculations, with a slight overestimation of 12% and 5%, for OH and (HO2+RO2) respectively, in average for the reference model, and an overestimation of approximately 20% for OH and an underestimation for (HO2+RO2) for the other selected model version. Thus, we can conclude from our study that OH and (HO2+RO2) radical levels agree on average with observations within the uncertainty range. Finally, an analysis of the radical budget, on a daily basis (06:00–18:00 UTC), indicates that HONO photolysis (~35%), O3 photolysis (~23%), and aldehydes and ketones photolysis (~16% for formaldehyde and 18% for others) are the main radical initiation pathways. According to the MCM modelling, the reactions of RO2 with NO2 (~19%), leading mainly to PAN formation, is a significant termination pathway in addition to the main net loss via reaction of OH with NO2 (~50%).
Previous studies indicated that absolute CH4 emissions and CH4 yield might increase and that milk production efficiency might decrease with age in cattle. Both would make strategies to increase ...longevity in dairy cattle less attractive. These aspects were experimentally determined in Brown Swiss cattle distributed continuously across a large age range. Thirty lactating dairy cows (876–3,648 d of age) received diets consisting of hay, corn silage, and grass pellets supplemented with 0 or 5kg of concentrate per day. Twelve heifers (199–778 d of age) received hay only. Cows and heifers were members of herds subjected to the 2 different feeding regimens (with or without concentrate) for the past 10 yr. Methane emissions were measured individually for 2 d in open-circuit respiration chambers, followed by quantifying individual feed intake and milk yield over 8 d. Additional data on digestibility, rumination time, and passage time of feed of all experimental animals were available. Regression analyses were applied to evaluate effects of age and feeding regimen. Body weight, milk yield, and the hay proportion of forage dry matter intake were considered as covariates. Methane emissions per unit of intake, body weight, and milk yield were significantly related to age. Their development in the cows with age was characterized by an increase to maximum at around 2,000 d of age, followed by a decline. This response was not accompanied by corresponding age-related changes in intake, chewing activity, digesta passage time, and digestibility of organic matter, which would have explained shifts in CH4. However, fiber digestibility showed a similar change with age as methane emissions, resulting in quite stable methane emissions per unit of digestible fiber. As expected, methane emissions intensity per unit of milk produced was greater by 8% without concentrate than with concentrate, but no difference was noted in the response to age when the animals were subjected to different feeding regimens. The efficiency of milk production was only marginally influenced by age and diet, and no different response was observed for age in the 2 dietary regimens. In conclusion, life cycle analyses of milk production systems focusing on longevity should consider changing methane yields with age in addition to the variation in environmental costs for replacements of culled cows.
Fourteen years of meteorological parameters, aerosol variables (absorption and scattering coefficients, aerosol number concentration) and trace gases (CO, NOx, SO2) measured at the Jungfraujoch (JFJ, ...3580 m a.s.l.) have been analyzed as a function of different synoptic weather types. The Schüepp synoptic weather type of the Alps (SYNALP) classification from the Alpine Weather Statistics (AWS) was used to define the synoptic meteorology over the whole Swiss region. The seasonal contribution of each synoptic weather type to the aerosol concentration was deduced from the aerosol annual cycles while the planetary boundary layer (PBL) influence was estimated by means of the diurnal cycles. Since aerosols are scavenged by precipitation, the diurnal cycle of the CO concentration was also used to identify polluted air masses. SO2 and NOx concentrations were used as precursor tracers for new particle formation and growth, respectively. The aerosol optical parameters and number concentration show elevated loadings during advective weather types during the December–March period and for the convective anticyclonic and convective indifferent weather types during the April–September period. This study confirms the consensus view that the JFJ is mainly influenced by the free troposphere during winter and by injection of air parcels from the PBL during summer. A more detailed picture is, however, drawn where the JFJ is completely influenced by free tropospheric air masses in winter during advective weather types and largely influenced by the PBL also during the night in summer during the subsidence weather type. Between these two extreme situations, the PBL influence at the JFJ depends on both the time of year and the synoptic weather type. The fraction of PBL air transported to the JFJ was estimated by the relative increase of the specific humidity and CO.
Using an unprecedentedly large geochemical database, we compare temporal and spatial variations in inhalable trace metal background concentrations in a major city (Barcelona, Spain) and at a nearby ...mountainous site (Montseny) affected by the urban plume. Both sites are contaminated by technogenic metals, with V, Pb, Cu, Zn, Mn, Sn, Bi, Sb and Cd all showing upper continental crust (UCC) normalised values >1 in broadly increasing order. The highest metal concentrations usually occur during winter at Barcelona and summer in Montseny. This seasonal difference was especially marked at the remote mountain site in several elements such as Ti and Rare Earth Elements, which recorded campaign maxima, exceeding PM10 concentrations seen in Barcelona. The most common metals were Zn, Ti, Cu, Mn, Pb and V. Both V and Ni show highest concentrations in summer, and preferentially fractionate into the finest PM sizes (PM1/PM10 > 0.5) especially in Barcelona, this being attributed to regionally dispersed contamination from fuel oil combustion point sources. Within the city, hourly metal concentrations are controlled either by traffic (rush hour double peak for Cu, Sb, Sn, Ba) or industrial plumes (morning peak of Ni, Mn, Cr generated outside the city overnight), whereas at Montseny metal concentrations rise during the morning to a single, prolonged afternoon peak as contaminated air transported by the sea breeze moves into the mountains. Our exceptional database, which includes hourly measurements of chemical concentrations, demonstrates in more detail than previous studies the spatial and temporal variability of urban pollution by trace metals in a given city. Technogenic metalliferous aerosols are commonly fine in size and therefore potentially bioavailable, emphasising the case for basing urban background PM characterisation not only on physical parameters such as mass but also on sample chemistry and with special emphasis on trace metal content.
PDF
