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This chapter revisits the major problems relating to manmade disturbances in the global nitrogen (N) cycle, and links the local findings from the project to the large-scale effects. The human transformationof atmospheric N2 to chemically and biologically more reactive species causes a number of environmental effects. The focus of this project has been budget estimates of N for two large watersheds with a set of subcatchments in southern Norway, accompanied by process studies to explain patterns of retention and runoff of N. Atmospheric inputs were close to 2.5 mg N m- 2 yr-1 and by far the dominant source of N for the sparsely populated, heathlanddominated watershed. Low retention and apparent N saturation could be accredited to high atmospheric inputs of N, but also hydrology, poorly developed soils and terrestrial P limitation. In this acidified watershed, nitrate contributed nearly 50% to surface water acidification, underlining the importance for strong cuts in NOx and NHx emissions. P concentrations were low, frequently < 1 mu g L- 1, causing high N:P ratios in runoff, and promotingP limitation both in freshwater and the nearshore marine recipient. For the agriculturally and forested watershed, atmospheric N deposition was < 1.5 mg N m-2 yr-1, and agricultural activities were the totally dominant source of N, yielding generally high but fluctuating concentrations of N and P in runoff water. Forestry and agricultural practices were major determinants of N runoff. Thehigh concentrations of both N and P in the major outlet of this watershed would be a major source of eutrophication for the recipient fjord. For both watersheds, climatic fluctuations strongly affected annual runoff patterns of N. The fate of ammonium relative to nitrate andlong-term climatic changes with a possible mineralization of soil stores of organic N are unpredictable determinants to future effects ofN. [ABSTRACT FROM AUTHOR]

The deposition of atmospheric pollutants in southern Norway is relatively high, and exceeds the critical load for acid deposition in sensitive ecosystems. While the effects of the sulfur deposition are relatively well known and documented, the fate and effects of oxidized and reduced nitrogen compounds are much less well known. In order to study the cycling of nitrogen in southern Norway, the inter-institutional research program, Nitrogen from Mountains to Fjords, was launched in 1991. The program aims to describe the nitrogen mass balance and the effects of nitrogen deposition in two different watersheds in southern Norway. In this respect, quantification of the atmospheric inputfor comparison with runoff and other transfer data has been an important task. The atmospheric input has been estimated on the basis of available data from the national monitoring of air and precipitation chemistry, and additional measurement activities within the study areas, for the period 1993--1995. In the Bjerkreim watershed topographical effects result in large variation in precipitation amounts within the study area, and between the individual 44 hydrological subcatchments. Annual nitrogen deposition varied between 1400 and 2300 mg N m-2 yr-1, with the highest figures obtained for themountainous areas receiving most precipitation. Similar observationswere made for the atmospheric deposition of sulfur and chloride, which were determined in order to compare input and runoff data as well as a basis for calculation of exceedances of the critical loads. Annual deposition of sulfur and chloride were 900--1500 mg S m- 2 yr-1 and 12 000--21 000 mg Cl- m-2 yr-1. The Auli watershed shows much less variation in the amount of precipitation and, consequently, in the deposition of nitrogen, sulfur and chloride to the 12 subcatchments for which input data were estimated. Annual average deposition of nitrogen was estimated [ABSTRACT FROM AUTHOR]

Abstract: Particle number concentration was measured between June 2009 and June 2010 at Akrotiri research station in a rural/suburban region of western Crete (Greece). Overall, the available data covered 157 days during the aforementioned period of measurements. The objectives were to study the number size distribution characteristics of ambient aerosols and furthermore to identify new particle formation events and to evaluate particle formation rates and growth rates of the newborn particles. Aerosol particles with mobility diameters between 10 and 1100 nm were measured using a Scanning Mobility Particle Sizer (SMPS) system. Measurements were performed at ambient relative humidities. The median total particle number concentration was 525 #/cm3 whereas the number concentration ranged between 130 #/cm3 and 9597 #/cm3. The average percentage of particles with diameters between 10 nm and 100 nm (N10–100) to total particles was 53% during summer and spring, but reached 80% during winter. Maximum average contribution of nano-particles (10 nm < D p < 50 nm) to total particles was recorded also in winter and was attributed partly to the effect of local heating. Furthermore, back trajectories (HYSPLIT model) showed that different air mass origins are linked to different levels of particle number concentrations, with higher values associated with air masses passing from polluted areas before reaching the Akrotiri station. Modal analysis of the measured size distribution data revealed a strong nucleation mode during winter (15–25 nm), which can be correlated with emissions from local sources (domestic heating). The nucleation mode was observed also during the spring campaigns and was partly linked to new particle formation events. On the contrary, an accumulation mode (80–120 nm) prevailed in the measurements during summer campaigns, when the station area was influenced by polluted air masses arriving mainly from Eastern Europe. In total, 13 new particle formation events were recorded during the 157 days of measurements. Nucleation events were associated with low values of N100 particle number concentration and reduced coagulation sinks. Mean growth and formation rates were calculated and showed values equal to 6 nm hr−1 and 13 cm−3 s−1, respectively. [Copyright &y& Elsevier]

Abstract: Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements. In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions. [Copyright &y& Elsevier]

The article focuses on the COST Action ES0602 for effective integration of current assets for the efficient chemical weather forecasting in Europe. The collaboration of different sectors from 2007 to 2011 will concentrate on infrastructure development for near real-time exchange of input data. Moreover, the Action will offer recommendations on the best pattern in presenting and disseminating of chemical weather information for the public and decision makers.