Monitorización y tendencias de la deposición de N en España, incluyendo polvo sahariano

The chemical composition of the atmosphere has significantly changed in the last century, mostly due to increased emissions of gases and particles derived from human activities. Several studies have analyzed the trends in the chemical composition of rainwater and atmospheric deposition in recent decades in central and northern Europe. However, for Spain there is a lack of studies at national level. Up to now, analyses of decadal trends are only available from a few individual stations.In this paper we first present the different methods to measure atmospheric deposition. Then we compile a list of atmospheric deposition monitoring stations in Spain and review the available time series, for series longer than 10 years, with special attention to the trends of N, S and African dust. Finally, we indicate future research directions to fill the gaps in knowledge about patterns and trends of atmospheric deposition at a national level.La composición química de la atmósfera ha cambiado significativamente en los últimos 100 años principalmente debido al aumento de las emisiones de gases y partículas derivadas de las actividades humanas. Numerosos estudios han descrito las tendencias de la composición química de la lluvia y la deposición atmosférica en países del centro y norte de Europa. Sin embargo, para España no existen estudios a escala nacional y actualmente sólo disponemos de análisis de las tendencias en algunas estaciones individuales en puntos concretos del territorio.En este trabajo primero presentamos los distintos métodos de medida de la deposición atmosférica. A continuación, realizamos una recopilación de estaciones de monitoreo de la deposición atmosférica en España y revisamos las tendencias de las series temporales largas disponibles (más de 10 años) con especial atención a las tendencias de N, S y del polvo africano. Finalmente, indicamos futuras direcciones de investigación para completar las lagunas en el conocimiento sobre pautas y tendencias de la deposición atmosférica a nivel nacional

Long-term effects of changing atmospheric pollution on throughfall, bulk deposition and streamwaters in a Mediterranean forest

The abatement programs implanted in Europe to reduce SO₂, NO₂ and NH³ emissions are here evaluated by analyzing the relationships between emissions in Spain and neighboring countries and atmospheric deposition in a Mediterranean forest in the Montseny mountains (NE Spain) for the last 3decades. A canopy budget model was applied to throughfall data measured during a period of high emissions (1995-1996) and a period of lower emissions (2011-2013) to estimate the changes in dry deposition over this time span. Emissions of SO₂ in Spain strongly decreased (77%) and that was reflected in reductions for nssSO4² in precipitation (65% for concentrations and 62% for SO4²-S deposition). A lower decline was found for dry deposition (29%). Spanish NO₂ emissions increased from 1980 to 1991, remained constant until 2005, and decreased thereafter, a pattern that was paralleled by NO3(-) concentrations in bulk precipitation at Montseny. This pattern seems to be related to a higher share of renewable energies in electricity generation in Spain in recent years. However, dry deposition increased markedly between 1995 and 2012, from 1.3 to 6.7kgha¯¹year¯¹. Differences in meteorology between periods may have had a role, since the recent period was drier thus probably favoring dry deposition. Spanish NH³ emissions increased by 13% between 1980 and 2012 in Spain but NH₄⁺ concentrations in precipitation and NH₄⁺-N deposition showed a decreasing trend (15% reduction) at Montseny, probably linked to the reduction ammonium sulfate and nitrate aerosols to be scavenged by rainfall. NH₄⁺-N dry deposition was similar between the compared periods. The N load at Montseny (15-17kgha¯¹year¯¹) was within the critical load range proposed for Mediterranean sclerophyllous forests (15-17.5kgha¯¹year¯¹). The onset of N saturation is suggested by the observed increasing N export in streamwaters

Effects of teleconnection patterns on the atmospheric routes, precipitation and deposition amounts in the north-eastern Iberian Peninsula

The North Atlantic Oscillation (NAO) has been identified as one of the atmospheric patterns which mostly influence the temporal evolution of precipitation and temperature in the Mediterranean area. Recently, the Western Mediterranean Oscillation (WeMO) has also been proposed to describe the precipitation variability in the eastern Iberian Peninsula. This paper examines whether the chemical signature and/or the chemical deposition amounts recorded over NE Iberian Peninsula are influenced by these climatic variability patterns. Results show a more relevant role of the WeMO compared to NAO in the deposition of either marine (Cl⁻, Na⁺, Mg²⁺) or anthropogenic pollutants (H⁺, NH⁺/4, NO-/3 and SO2/4−). A cluster classification of provenances indicated that in winter (December to March) fast Atlantic air flows correspond to positive WeMO indices, while negative WeMOi are associated to Northeastern and Southwestern circulations. The negative phase of WeMO causes the entry of air masses from the Mediterranean into the Iberian Peninsula, that are enriched with marine ions and ions of anthropogenic origin (NH⁺/4, NO-/3 and SO2/4−). For these later, this suggests the advection over the Mediterranean of polluted air masses from southern Europe and the scavenging and deposition of this pollution by precipitation during the WeMO negative phases. This will carry transboundary pollutants to the NE Iberian Peninsula. However, local pollutants may also contribute, as precipitation events from the Mediterranean and the Atlantic (associated to both WeMO phases) may incorporate emissions that accumulate locally during the winter anticyclonic episodes typical of the region

Nitrogen deposition at Mediterranean holm-oak forests : loads and indicators /

En esta tesis presentamos información sobre la deposición de N en los bosques de encinar (Quercus ilex) en España para contribuir a mejorar la falta de estudios sobre el depósito de N en la cuenca del Mediterráneo. Se seleccionaron tres encinares cercanos a fuentes de contaminación urbanas (CB, CA y TC) y un cuarto sitio representativo de ambientes menos contaminados (LC). El sitio a priori menos afectado por las fuentes urbanas presentó cargas similares de contaminantes antropogénicos (N y S) que los más expuestos. Los resultados indican un transporte de contaminantes de las áreas metropolitanas, del tráfico marítimo y del transporte a larga distancia hacia las zonas de muestreo. Los valores de K+ en las muestras de trascolación procedieron de lixiviación desde el dosel, el SO42--S y NO3--N se originan por deposición seca, mientras que el NH4+-N fue absorbido en las copas. La deposición seca estimada supuso un 74 y 84 % del deposito total de N de 17 y 20 kg N ha-1 año-1 en LC y CB, respectivamente. Los resultados de esta tesis indican por lo tanto, que el total de depósito de N en varios bosques de España excede las cargas críticas propuestas para estos ecosistemas. Se estudió la variación de la química de la lluvia en el Montseny durante las últimas 3 décadas con el objetivo de entender cómo los programas de reducción de las emisiones de SO2, NO2 y NH3 implementados por El Convenio sobre la Contaminación Atmosférica Transfronteriza a Larga Distancia (CLRTAP) de la UN/ECE, afectan a la deposición atmosférica. Las fuertes reducciones de SO2 en España y países vecinos (75-85%) se reflejan en la reducción del nssSO42--S en la lluvia (65% en concentración, 62% en depósito) y en la deposición seca (29%) en el Montseny comparando mediciones en 1995-96 y 2011-13. Las emisiones de NO2 en España aumentaron de 1980 a 1991, fueron constantes hasta 2005 y luego disminuyeron, patrón que se refleja de forma paralela en los valores de NO3- en la precipitación del Montseny. Esto contrasta con los valores más elevados de NO3--N en depósito seco en 1995-96 comparado con los valores de 2011-12 (de 1.3 a 6.7 kg ha-1año-1), que se puede atribuir a las condiciones climáticas particulares de cada período. El aumento de las emisiones de NH3 en España durante los últimos 30 años (13%) no se reflejó en la tendencia del contenido de NH4+ en la lluvia en el Montseny. Como las emisiones de NH3 en España no han disminuido son necesarios acerca de los indicadores que mejor reflejan los síntomas en el ecosistema. Aquí proponemos un valor umbral <2.5 mg m-3 de NH3 en el aire para proteger las comunidades liquénicas en encinares. Este valor se obtuvo a partir del estudio de las relaciones entre el NH3 en el aire y la diversidad de líquenes por grupos funcionales (oligotrófico y nitrofílos) en un gradiente de distancia a una fuente emisora (granja). Además, otros parámetros (% N, δ15N, C: N, δ13C) medidos en diferentes compartimentos del ecosistema (hojas de árboles, musgos y suelos) resultaron buenos indicadores de contaminación por NH3. La variación de δ15N en hojas y musgos a lo largo del gradiente refleja la señal isotópica de la fuente N. El % N y el δ15N en musgo y hojas se correlacionó significativamente con la diversidad de líquenes nitrofílos y con los niveles de NH3, destacando así la especificidad de las especies nitrofílas a este compuesto. En el suelo, los mejores indicadores fueron la señal de δ15N y la ratio C:N. Esta última (<25) indicó un importante riesgo de lixiviación de N en la zona y la consecuente eutrofización de las aguas subterráneas. Por último, la variación en el contenido δ13C en muestras de hojas y musgos refleja la respuesta fisiológica de la vegetación a una mayor deposición de N.With the present PhD we provide new information on N deposition to holm oak (Quercus ilex) forests in Spain, in order to contribute to fill the gap about N deposition in the Mediterranean Basin. Three forest sites were selected for their proximity to traffic/urban pollution sources and a fourth site was chosen as representative of less polluted environments. Results showed that the site farthest from pollution had similar anthropogenic pollutant (N and S) deposition loads than two of the more exposed sites. A widespread transport of pollutants from metropolitan areas, maritime traffic and long-range transport affected the sampling areas. In throughfall samples, K+ was explained by leaching from the canopies, SO42--S and NO3--N were generally derived from dry deposition while NH4+-N was absorbed in the tree canopies. The estimated dry deposition provided a 74 and 84 % to the total deposition of 17 and 20 kg N ha-1 yr-1 at LC and CB, respectively. The results of this PhD indicate that total N deposition at various sites in Spain exceeds (about 30%) the proposed critical load for sclerophyllous forests. The chemistry of bulk deposition at the Montseny mountains during the past 3 decades was analysed in order to understand how the abatement programs implemented by the Convention on Long Range Transboundary Atmospheric Pollution (CLRTAP) from UN/ECE to reduce SO2, NO2 and NH3 emissions have affected atmospheric deposition at this site. Strong reductions of SO2 emissions in Spain and neighbouring countries (75-85%) were reflected in reductions of non-sea salt-SO42- in precipitation (65% for concentrations and 62% for SO42-S deposition) and dry deposition (29%) at Montseny comparing measurements in 1995-96 and 2011-13. The NO2 emissions in Spain increased from 1980 to 1991, remained constant until 2005, and decreased thereafter, similar as NO3- in bulk precipitation at Montseny. This contrasted with an increase of NO3- -N dry deposition from 1995-96 compared to 2011-2012 (from 1.3 to 6.7 kg ha-1y-1), attributed to the particular climatic conditions of each period. The increase of NH3 emissions in Spain during the last 30 years (13%) was not reflected in the NH4+ bulk deposition trends at Montseny, probably related to a decrease of the formation of ammonium sulphate and nitrate aerosols due to declining SO2 and NOx emissions. In Spain, NH3 emissions have not been reduced. Therefore, studies are needed for early warning of its effects on ecosystems. Here, we propose a critical level value of < 2.5 µg m-3 NH3 air concentrations to protect lichen communities at semi-natural holm oak forest. This value was calculated by studying the relationships between air NH3 concentrations and lichen diversity values separated by functional groups (oligotrophic and nitrophytic) in a distance gradient from an emission point source (cattle farm). Besides, other parameters (%N, δ15N, C:N, δ13C) measured in different compartments (tree leaves, moss tissue and soil) of the ecosystem also respond to NH3 pollution and serve as indicators of pollution. The leaves and moss δ15N signal variation along the gradient reflected the N isotopic signal of the NH3 source. The %N and δ15N signal values in moss and leaves were significantly correlated with the relative nitrophytic functional group diversity and air NH3 concentrations, which highlights the specific response of nitrophytic species to NH3 pollution. In soils, the δ15N signal and C:N ratios were significantly related to NH3 pollution, with soil C:N values (C:N<25) indicative of the onset of N leaching and alerting about the potential N saturation and the risk of groundwater eutrophication at this forest. Finally, the variation in δ13C content in foliar and moss samples reflected the physiological response of vegetation to enhanced N deposition

The Critical levels of atmospheric ammonia in a Mediterranean holm-oak forest in North-Eastern Spain

Altres ajuts: PM would like to thank COSTAction FP0903 for financial support of a short-term scientific mission through contract ECOST-STSM-FP0903-120912-019761. PM, PP, and CB acknowledge FCT-MEC support by contracts BD/51419/2011, BPD/75425/2010, and Investigador FCT. The comments of one reviewer are greatly appreciated.Despite recent regulations, atmospheric ammonia (NH₃) emissions have not changed much over the last decades and excessive nitrogen remains as one of the major drivers for biodiversity changes. To prevent deleterious effects on species and ecosystems, it is very important to establish safety thresholds, such as those defined by the Critical Level (CLE) concept, "the concentration above which direct adverse effects on receptors may occur, based on present knowledge." Empirical critical levels of atmospheric NH₃ have mainly been reported for temperate forests and there is a lack of information for Mediterranean forests. Here, we provide a case study on NH₃ CLEs for a typical Mediterranean ecosystem, the holm-oak (Quercus ilex) forest. To derive the CLE value, we measured NH₃ concentrations for 1 year at a distance gradient in the forest surrounding a point source (cattle farm) and used diversity changes of lichen functional groups to indicate the onset of adverse effects. We estimate a NH₃ CLE threshold of 2.6 μg m⁻³, a value that is higher than that reported in other Mediterranean ecosystems and suggests that the site has been already impacted by NH₃ pollution in the past. In a more general context, this study confirms the validity of lichen functional groups to derive CLEs in Mediterranean forests and woodlands and contribute to the body of knowledge regarding the impacts of NH₃ on ecosystems

Dry deposition and canopy uptake in Mediterranean holm-oak forests estimated with a canopy budget model : a focus on N estimations

Bulk/wet and throughfall fluxes of major compounds were measured from June 2011 to June 2013 at four Mediterranean holm-oak (Quercus ilex) forests in the Iberian Peninsula. Regression analysis between net throughfall fluxes and precipitation indicated that the best defined canopy process was leaching for K⁺ and uptake for NH₄⁺ at all sites. A more variable response between sites was found for Na⁺, Ca²⁺, SO₄²⁻ and Cl⁻, which suggests that the interplay of dry deposition, leaching and uptake at the canopy was different depending on site climate and air quality characteristics. A canopy budget model (CBM) was used to try to discriminate between the canopy processes and enable to estimate dry deposition and uptake fluxes at three of the sites that complied with the model specifications. To derive N uptake, an efficiency factor of NH₄⁺ vs. NO₃⁻ uptake (xNH₄) corresponding to moles of NH₄⁺ taken up for each NO₃⁻ mol, has to be determined. Up to now, a value of 6 has been proposed for temperate forests, but we lack information for Mediterranean forests. Experimental determination of N absorption on Quercus ilex seedlings in Spain suggests efficiency factors from 1 to 6. Based on these values, a sensitivity analysis for xNH₄ was performed and the NH₄N and NO₃N modeled dry deposition was compared with dry deposition estimated with independent methods (inferential modeling and washing of branches). At two sites in NE Spain under a milder Mediterranean climate, the best match was obtained for xNH4 = 6, corroborating results from European temperate forests. Based on this value, total DIN deposition was 12-13 kg N ha−1 y−1 at these sites. However, for a site in central Spain under drier conditions, variation of the NH4+ efficiency factor had little effect on DD estimates (which ranged from 2 to 2.6 kg N ha⁻¹ y⁻¹ with varying xNH₄); when added to wet deposition, this produced a total N deposition in the range 2.6-3.4 kg N ha⁻¹ y⁻¹. Dry deposition was the predominant pathway for N, accounting for 60-80% of total deposition, while for base cations wet deposition dominated (55-65%). Nitrogen deposition values at the northwestern sites were close to the empirical critical load proposed for evergreen sclerophyllous Mediterranean forests (15-17 kg N ha⁻¹ y⁻¹). When organic N deposition at these forests is added (3 kg N ha⁻¹ y⁻¹), the total N input to the sites in NE Spain are close to the critical loads for Mediterranean evergreen oak forests

Quantitative study on nitrogen deposition and canopy retention in Mediterranean evergreen forests

Altres ajuts: This research was also funded by the project from Autonomous Government of Madrid AGRISOST-CM (P2013/ABI-2717). CIEMAT work in this study was partially supported by an agreement between the Spanish Ministry of Agriculture, Food and Environment and CIEMAT on Critical loads and levels. The utilization of Tres Cantos monitoring site was possible thanks to an agreement between CIEMAT and Ayuntamiento de Madrid.To assess the impact of nitrogen (N) pollutants on forest ecosystems, the role of the interactions in the canopy needs to be understood. A great number of studies have addressed this issue in heavily N-polluted regions in north and central Europe. Much less information is available for the Iberian Peninsula, and yet this region is home to mountain forests and alpine grasslands that may be at risk due to excessive N deposition. To establish the basis for ecology-based policies, there is a need to better understand the forest response to this atmospheric impact. To fill this gap, in this study, we measured N deposition (as bulk, wet, and throughfall fluxes of dissolved inorganic nitrogen) and air N gas concentrations from 2011 to 2013 at four Spanish holm oak (Quercus ilex) forests located in different pollution environments. One site was in an area of intensive agriculture, two sites were influenced by big cities (Madrid and Barcelona, respectively), and one site was in a rural mountain environment 40 km north of Barcelona. Wet deposition ranged between 0.54 and 3.8 kg N ha⁻¹ year⁻¹ for ammonium (NH₄⁺)-N and between 0.65 and 2.1 kg N h⁻¹ year⁻¹ for nitrate (NO₃⁻)-N, with the lowest deposition at the Madrid site for both components. Dry deposition was evaluated with three different approaches: (1) a canopy budget model based in throughfall measurements, (2) a branch washing method, and (3) inferential calculations. Taking the average dry deposition from these methods, dry deposition represented 51-67% (reduced N) and 72-75% (oxidized N) of total N deposition. Canopies retained both NH₄⁺-N and NO₃⁻N, with a higher retention at the agricultural and rural sites (50-60%) than at sites located close to big cities (20-35%, though more uncertainty was found for the site near Madrid), thereby highlighting the role of the forest canopy in processing N pollutant emissions

Atmospheric deposition of inorganic nitrogen in Spanish holm oak forests measured with ion-exchange resins and conventional collectors

Atmospheric nitrogen deposition is one of the main threats for biodiversity and ecosystem functioning. Measurement techniques like ion-exchange resin collectors (IECs), which are less expensive and timeconsuming than conventional methods, are gaining relevance in the study of atmospheric deposition and are recommended to expand monitoring networks. In the present work, bulk and throughfall deposition of inorganic nitrogen were monitored in three different holm oak forests in Spain during two years. The results obtained with IECs were contrasted with a conventional technique using bottle collectors and with a literature review of similar studies. The performance of IECs in comparison with the conventional method was good for measuring bulk deposition of nitrate and acceptable for ammonium and total dissolved inorganic nitrogen. Mean annual bulk deposition of inorganic nitrogen ranged 3.09 e5.43 kg N ha1 according to IEC methodology, and 2.42e6.83 kg N ha1 y1 using the conventional method. Intra-annual variability of the net throughfall deposition of nitrogen measured with the conventional method revealed the existence of input pulses of nitrogen into the forest soil after dry periods, presumably originated from the washing of dry deposition accumulated in the canopy. Important methodological recommendations on the IEC method and discussed, compiled and summarized

Atmospheric pollutants in peri-urban forests of Quercus ilex : evidence of pollution abatement and threats for vegetation

Peri-urban vegetation is generally accepted as a significant remover of atmospheric pollutants, but it could also be threatened by these compounds, with origin in both urban and non-urban areas. To characterize the seasonal and geographical variation of pollutant concentrations and to improve the empirical understanding of the influence of Mediterranean broadleaf evergreen forests on air quality, four forests of Quercus ilex (three peri-urban and one remote) were monitored in different areas in Spain. Concentrations of nitrogen dioxide (NO₂), ammonia (NH₃), nitric acid (HNO₃) and ozone (O₃) were measured during 2 years in open areas and inside the forests and aerosols (PM₁₀) were monitored in open areas during 1 year. Ozone was the only air pollutant expected to have direct phytotoxic effects on vegetation according to current thresholds for the protection of vegetation. The concentrations of N compounds were not high enough to directly affect vegetation but could be contributing through atmospheric N deposition to the eutrophization of these ecosystems. Peri-urban forests of Q. ilex showed a significant below-canopy reduction of gaseous concentrations (particularly NH₃, with a mean reduction of 29-38 %), which indicated the feasibility of these forests to provide an ecosystem service of air quality improvement. Well-designed monitoring programs are needed to further investigate air quality improvement by peri-urban ecosystems while assessing the threat that air pollution can pose to vegetation

Monitorización y tendencias de la deposición de N en España, incluyendo polvo sahariano

The chemical composition of the atmosphere has significantly changed in the last century, mostly due to increased emissions of gases and particles derived from human activities. Several studies have analyzed the trends in the chemical composition of rainwater and atmospheric deposition in recent decades in central and northern Europe. However, for Spain there is a lack of studies at national level. Up to now, analyses of decadal trends are only available from a few individual stations.In this paper we first present the different methods to measure atmospheric deposition. Then we compile a list of atmospheric deposition monitoring stations in Spain and review the available time series, for series longer than 10 years, with special attention to the trends of N, S and African dust. Finally, we indicate future research directions to fill the gaps in knowledge about patterns and trends of atmospheric deposition at a national level.La composición química de la atmósfera ha cambiado significativamente en los últimos 100 años principalmente debido al aumento de las emisiones de gases y partículas derivadas de las actividades humanas. Numerosos estudios han descrito las tendencias de la composición química de la lluvia y la deposición atmosférica en países del centro y norte de Europa. Sin embargo, para España no existen estudios a escala nacional y actualmente sólo disponemos de análisis de las tendencias en algunas estaciones individuales en puntos concretos del territorio.En este trabajo primero presentamos los distintos métodos de medida de la deposición atmosférica. A continuación, realizamos una recopilación de estaciones de monitoreo de la deposición atmosférica en España y revisamos las tendencias de las series temporales largas disponibles (más de 10 años) con especial atención a las tendencias de N, S y del polvo africano. Finalmente, indicamos futuras direcciones de investigación para completar las lagunas en el conocimiento sobre pautas y tendencias de la deposición atmosférica a nivel nacional