Dynamics of atmospheric ammonia exchange with intensively-managed grassland

Continuous measurements o f atmospheric ammonia (NH3) exchange were conducted for a period o f 19 months (May 1998-November 1999) over intensively managed grassland (cut twice for silage and grazed) in southern Scotland using the aerodynamic gradient method. The mean NH3 concentration and flux for the whole measurement period were 1.52 pg m ' and 13.9 ng n f s’ , respectively.Enhanced emissions o f NH3 were observed following four separate grass cutting events (June 1998, August 1998, June 1999 and May 2000) with peak emissions o f 380, 200, 539 and 508 ng m’2 s '1, respectively. The magnitude o f these emissions was up to an order o f magnitude greater than the emissions observed from the grassland prior to cutting. Enhanced NH3 emissions from cut grassland have been observed, but not quantified prior to this study.The NH3 exchange was bi-directional with large diurnal and seasonal variation, which was strongly linked to grassland management in addition to meteorological conditions. The grassland varied from being a net sink for NH3 during winter months (-6.0 g NH3-N ha' 1 d '1) and prior to cutting o f the grass (-4.9 g NH3-N ha' 1 d’1) to being a net source after the grass was cut (29.3 g NH3-N ha' 1 d '1) and after nitrogen fertilisation (153.6 g NH3-N ha' 1 d’1). Net emission was also observed during grazing periods (33.0 g NH3-N ha' 1 d '1). The pattern o f NH3 exchange was similar for 1998 and 1999.The net annual budget o f NH3 exchange for the grassland for May 1998-April 1999 was emission o f NH3 o f 1.9 kg N ha' 1 y r'1, equating to 1.6% o f the fertiliser N applied. The gross emission flux for the year was 4.2 kg N ha' 1 yr’1. Scaling up these gross emissions across the whole o f the UK improved grassland (60,500 km2) would lead to 25 kt NH3-N, equivalent to 9.5% o f the UK total emissions. These results indicate that the gross emission from all processes in fertilised grassland, including emissions from fertilisation, grazing and from cutting, make a significant contribution to the NH3 emission budget o f the UK.A two-layer canopy compensation point resistance model was applied to the NH3 measurements. Close agreement between measured and modelled fluxes was obtained by introducing seasonally dependent functions o f the foliar and ground layer emission potentials (rs, rg) for key periods. This is a significant improvement on the current use o f constant emission potentials within national deposition models.In addition to the resistance modelling approach, a fully dynamic grassland ecosystem model (PaSim) was applied to the NH3 measurements. In PaSim, the emission potentials and NH3 exchange are linked functionally to dynamic plant and soil N pools. Scenarios o f changing climate and management were explored with the model. The simulated NH3 emissions did not follow the expected thermodynamic response to a rise in temperature and demonstrated the complexity o f the ecosystem level response o f NH3 exchange to climate change. Simulated NH3 emissions were reduced by 15% by delaying the timing o f fertiliser applications by two weeks, indicating the potential o f this measure as an NH3 abatement option.The first major intercomparison o f NH3 gradient measurements was conducted during a field campaign over intensively managed grassland in Germany. Enhanced emissions o f NH3 after grass cutting were also observed at this site, providing additional corroboration for this emission source, while the temporal pattern of exchange was similar to that observed in Scotland

Process-based modelling of NH3 exchange with grazed grasslands

In this study the GAG model, a process-based ammonia (NH3) emission model for urine patches, was extended and applied for the field scale. The new model (GAG_field) was tested over two modelling periods, for which micrometeorological NH3 flux data were available. Acknowledging uncertainties in the measurements, the model was able to simulate the main features of the observed fluxes. The temporal evolution of the simulated NH3 exchange flux was found to be dominated by NH3 emission from the urine patches, offset by simultaneous NH3 deposition to areas of the field not affected by urine. The simulations show how NH3 fluxes over a grazed field in a given day can be affected by urine patches deposited several days earlier, linked to the interaction of volatilization processes with soil pH dynamics. Sensitivity analysis showed that GAG_field was more sensitive to soil buffering capacity (β), field capacity (θfc) and permanent wilting point (θpwp) than the patch-scale model. The reason for these different sensitivities is dual. Firstly, the difference originates from the different scales. Secondly, the difference can be explained by the different initial soil pH and physical properties, which determine the maximum volume of urine that can be stored in the NH3 source layer. It was found that in the case of urine patches with a higher initial soil pH and higher initial soil water content, the sensitivity of NH3 exchange to β was stronger. Also, in the case of a higher initial soil water content, NH3 exchange was more sensitive to the changes in θfc and θpwp. The sensitivity analysis showed that the nitrogen content of urine (cN) is associated with high uncertainty in the simulated fluxes. However, model experiments based on cN values randomized from an estimated statistical distribution indicated that this uncertainty is considerably smaller in practice

Impacts of desert dust outbreaks on air quality in urban areas

Air pollution has many adverse effects on health and is associated with an increased risk of mortality. Desert dust outbreaks contribute directly to air pollution by increasing particulate matter concentrations. We investigated the influence of desert dust outbreaks on air quality in Santa Cruz de Tenerife, a city located in the dust export pathway off the west coast of North Africa, using air-quality observations from a six-year period (2012–2017). During winter intense dust outbreaks PM10 mean (24-h) concentrations increased from 14 µg m−3 to 98 µg m−3 , on average, and PM2.5 mean (24-h) concentrations increased from 6 µg m−3 to 32 µg m−3 . Increases were less during summer outbreaks, with a tripling of PM10 and PM2.5 daily mean concentrations. We found that desert dust outbreaks reduced the height of the marine boundary layer in our study area by >45%, on average, in summer and by ∼25%, on average, in winter. This thinning of the marine boundary layer was associated with an increase of local anthropogenic pollution during dust outbreaks. NO2 and NO mean concentrations more than doubled and even larger relative increases in black carbon were observed during the more intense summer dust outbreaks; increases also occurred during the winter outbreaks but were less than in summer. This has public health implications; local anthropogenic emissions need to be reduced even further in areas that are impacted by desert dust outbreaks to reduce adverse health effects.This activity has been undertaken in the framework of the World Meteorological Organisation Global Atmosphere Watch Urban Research Meteorology and Environment (GURME) project

Modelling PM2.5 chemical composition with CAMx in southwest Spain

Comunicación presentada en: 2012 European Aerosol Conference (EAC-2012), B-WG01S2P30, celebrada del 2 al 7 de septiembre de 2012 en Granada

Measurements and simulation of speciated PM2.5 in south-west Europe

Chemically speciated concentrations of PM2.5 (sulphate, ammonium, nitrate, elemental and organic carbon) were simulated in south-west Europe using the three-dimensional air quality model CAMx driven by the MM5 meteorological model. The inner domain covered the south-west region of Spain with a high spatial (2 km × 2 km) and temporal resolution (1 h). The simulation results were evaluated against experimental data obtained in four intensive field campaigns performed in 2008 and 2009 at urban and rural sites. PM2.5 measurements of secondary inorganic compounds and carbonaceous aerosol plus a suite of major and trace elements were determined. High time resolution (10 min) measurements of Black Carbon (BC) were also conducted. The model captured the variability in the ammonium concentrations in both summer and winter periods, although it tended to underestimate the magnitude of concentrations, while for sulphate the performance was better during the summer periods. Particulate ammonium nitrate was only simulated in significant concentrations in the wintertime campaign. This was found to be consistent with the measured composition of PM2.5 where most of nitrate (79–94%) and a significant fraction of sulphate (24–37%) were estimated to be present as non-ammonium salts. These non-ammonium nitrate salts were attributed to the formation of NaNO3. The model PM2.5 primary elemental carbon simulations, evaluated with hourly resolution, captured the diurnal and seasonal variability of PM2.5 BC concentrations at the urban site while poorer performance was observed at the rural site. A large underestimation was observed for simulated PM2.5 organic carbon concentrations during all campaigns. Scenarios of pollution events linked to emissions from south-west Spain, shipping and contributions from more distant emission sources such as Portugal were identified. These results highlight how the distinct features of PM2.5 composition in southern Europe regions, such as the large contribution of non-ammonium salts, need to be taken into account both in model evaluation and in future implementation of aerosol modelling systems.The authors gratefully acknowledge funding from the Department of Innovation, Science and Enterprise of the Government of Andalusia through the research projects AER-REG (P07-RNM- 03125) and SIMAND (P07-RNM-02729) and from the Department of Environment, Andalusian Regional Government (project: 199/ 2011/C/00). In addition, we thank the Spanish Ministry of Economy and Competitiveness for funding through the project POLLINDUST (CGL2011-26259)

Aerosol characterisation in the subtropical eastern North Atlantic region using long-term AERONET measurements

A comprehensive characterisation of atmospheric aerosols in the subtropical eastern North Atlantic has been carried out using long-term ground-based Aerosol Robotic NETwork (AERONET) photometric observations over the period 2005–2020 from a unique network made up of four stations strategically located from sea level to 3555 m on the island of Tenerife. This site can be considered a sentinel for the passage of airmasses going to Europe from Africa, and therefore the aerosol characterisation performed here adds important information for analysing their evolution during their path toward Northern Europe. Two of these stations (Santa Cruz de Tenerife – SCO – at sea level and La Laguna – LLO – at 580 m a.s.l.) are located within the marine atmospheric boundary layer (MABL), and the other two (Izaña – IZO – at 2373 m a.s.l. and Teide Peak – TPO – at 3555 m a.s.l.) are high mountain stations within the free troposphere (FT). Monthly climatology of the aerosol optical depth (AOD), Ångström exponent (AE), aerosol concentration, size distribution and aerosol optical properties has been obtained for the MABL and FT. Measurements that are quite consistent across the four sites have been used to categorise the main atmospheric scenarios, and these measurements confirm an alternation between predominant background conditions and predominant dust-loaded Saharan air mass conditions caused by seasonal dust transport over the subtropical North Atlantic. Background conditions prevail in the MABL and FT for most of the year, while dust-laden conditions dominate in July and August.The authors also acknowledge the support from ACTRIS, Ministerio de Ciencia e Innovación, Spain, through the projects SYNERA (PID2020-118793GA-I00) and ePOLAAR (RTI2018-097864-BI00) and from Junta de Castilla y León (grant no. VA227P20)

Impact of the 2021 La Palma volcanic eruption on air quality: Insights from a multidisciplinary approach

The La Palma 2021 volcanic eruption was the first subaerial eruption in a 50-year period in the Canary Islands (Spain), emitting ~1.8 Tg of sulphur dioxide (SO2) into the troposphere over nearly 3 months (19 September-13 December 2021), exceeding the total anthropogenic SO2 emitted from the 27 European Union countries in 2019. We conducted a comprehensive evaluation of the impact of the 2021 volcanic eruption on air quality (SO2, PM10 and PM2.5 concentrations) utilising a multidisciplinary approach, combining ground and satellite-based measurements with height-resolved aerosol and meteorological information. High concentrations of SO2, PM10 and PM2.5 were observed in La Palma (hourly mean SO2 up to ~2600 μg m−3 and also sporadically at ~140 km distance on the island of Tenerife (> 7700 μg m−3) in the free troposphere. PM10 and PM2.5 daily mean concentrations in La Palma peaked at ~380 and 60 μg m−3. Volcanic aerosols and desert dust both impacted the lower troposphere in a similar height range (~ 0–6 km) during the eruption, providing a unique opportunity to study the combined effect of both natural phenomena. The impact of the 2021 volcanic eruption on SO2 and PM concentrations was strongly influenced by the magnitude of the volcanic emissions, the injection height, the vertical stratification of the atmosphere and its seasonal dynamics. Mean daily SO2 concentrations increased during the eruption, from 38 μg m−3 (Phase I) to 92 μg m−3 (Phase II), showing an opposite temporal trend to mean daily SO2 emissions, which decreased from 34 kt (Phase I) to 7 kt (Phase II). The results of this study are relevant for emergency preparedness in all international areas at risk of volcanic eruptions; a multidisciplinary approach is key to understand the processes by which volcanic eruptions affect air quality and to mitigate and minimise impacts on the population.The authors also acknowledge the support from ACTRIS and ACTRIS-Spain, the Spanish Ministry of Science and Innovation and the support from the European Union H2020 program through the following projects (PID2019-104205GB-C21/AEI/10.13039/501100011033, EQC2018-004686-P, PID2019-103886RB-I00/AEI/10.13039/501100011033 and PID2020-521-118793GA-I00) and programs (GA No. 654109, 778349, 871115, 101008004 and 101086690). Research activities of the CSIC staff during the eruption were funded by CSIC through the CSIC-PIE project with ID numbers PIE20223PAL009 and PIE20223PAL013 (Real Decreto 1078/2021, de 7 de diciembre). Part of this study was performed within the framework of the project AERO-EXTREME (PID2021-125669NB-I00) funded by the Spanish State Research Agency (AEI) and ERDF funds

Desert dust outbreak in the Canary Islands (February 2020): assessment and impacts

World Weather Research Programme (WWRP 2021–1

Izaña Atmospheric Research Center. Activity Report 2019-2020

Editors: Emilio Cuevas, Celia Milford and Oksana Tarasova.[EN]The Izaña Atmospheric Research Center (IARC), which is part of the State Meteorological Agency of Spain (AEMET), is a site of excellence in atmospheric science. It manages four observatories in Tenerife including the high altitude Izaña Atmospheric Observatory. The Izaña Atmospheric Observatory was inaugurated in 1916 and since that date has carried out uninterrupted meteorological and climatological observations, contributing towards a unique 100-year record in 2016. This reports are a summary of the many activities at the Izaña Atmospheric Research Center to the broader community. The combination of operational activities, research and development in state-of-the-art measurement techniques, calibration and validation and international cooperation encompass the vision of WMO to provide world leadership in expertise and international cooperation in weather, climate, hydrology and related environmental issues.[ES]El Centro de Investigación Atmosférica de Izaña (CIAI), que forma parte de la Agencia Estatal de Meteorología de España (AEMET), representa un centro de excelencia en ciencias atmosféricas. Gestiona cuatro observatorios en Tenerife, incluido el Observatorio de Izaña de gran altitud, inaugurado en 1916 y que desde entonces ha realizado observaciones meteorológicas y climatológicas ininterrumpidas y se ha convertido en una estación centenaria de la OMM. Estos informes resumen las múltiples actividades llevadas a cabo por el Centro de Investigación Atmosférica de Izaña. El liderazgo del Centro en materia de investigación y desarrollo con respecto a las técnicas de medición, calibración y validación de última generación, así como la cooperación internacional, le han otorgado una reputación sobresaliente en lo que se refiere al tiempo, el clima, la hidrología y otros temas ambientales afines

Izaña Atmospheric Research Center. Activity Report 2015-2016

This report is a summary of the many activities at the Izaña Atmospheric Research Center to the broader community. The combination of operational activities, research and development in state-of-the-art measurement techniques, calibration and validation and international cooperation encompass the vision of WMO to provide world leadership in expertise and international cooperation in weather, climate, hydrology and related environmental issues