| Title | Temporal and spatial patterns in the chemistry of wet deposition in Southern Alps |
| Abstract | In the last decades, in Europe a large effort was carried out to reduce sulphur and nitrogen emission in the atmosphere, in order to improve air quality and reduce the acidity of atmospheric deposition and the amount of nitrogen compounds it carries to terrestrial and aquatic ecosystems. This resulted in a sharp decrease in the deposition of sulphate and acidity, while until recently a decrease of the atmospheric load of nitrogen compounds was not evident. In this paper, we focus on the subalpine and alpine areas in North-Western Italy and Southern Switzerland (Canton Ticino), receiving high deposition of atmospheric pollutants transported from emission sources in the Po Valley, one of the most urbanised and industrialised areas of Europe. Long-term studies, covering a 30-year period (1984-2014), were carried out on the chemistry of atmospheric deposition in this area and its effects on surface water bodies through a cooperation between Swiss and Italian research institutions. A total of 14 atmospheric deposition wet-only sampling sites operate in this area, covering a wide latitudinal and altitudinal range (about 200-1900 m a.s.l.). A spatial gradient in the deposition of sulphate and nitrogen compounds was evident both in the 1990s and in recent times (2008-2012), with highest values in the south-eastern part of the area, close to the major emission sources. Deposition also varied depending on local topography.
The analysis of long-term trends revealed a large proportion of significant decreasing trends in the concentration of both sulphate and nitrogen compounds. Deposition changes were less evident, due to the high interannual variability in the data, caused by the highly variable precipitation amount, ranging from 1200-1300 mm in dry years to 3000 mm in wet years.
Sulphate concentrations and deposition decreased steadily since the 1980s, while ammonium and nitrate showed a widespread decrease only in the most recent period (after 2006). However, nitrogen wet deposition is still high with respect to critical loads: inorganic N deposition ranges from 60-70 meq m-2 y-1 (as the sum of ammonium and nitrate) at the alpine sites to 120-140 meq m-2 y-1 at the southern lowland sites. Deposition of ammonium has acquired an increasing importance in time, especially at the southern, more polluted sites: the relative contribution of reduced N to wet N deposition passed from about 50% in the early 1990s to 56-57% in recent years. The observed temporal changes in nitrogen deposition followed the emission decrease but with a delay. This aspect may be relevant in monitoring the effects of emission reductions as a result of the enforcements of international and national regulations. |
| Source | Atmospheric environment (1994) 146, pp. 44–54 |
| Keywords | atmospheric pollutionrain chemistrynitrogen depositionacidificationlong-term trends |
| Journal | Atmospheric environment (1994) |
| Editor | Pergamon., Oxford, Regno Unito |
| Year | 2016 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.atmosenv.2016.06.025 |
| Authors | Rogora M.; Colombo L.; Marchetto A.; Mosello R.; Steingruber S. |
| Text | 381412 2016 10.1016/j.atmosenv.2016.06.025 Scopus 2 s2.0 84993967094 ISI Web of Science WOS 000388051700005 atmospheric pollution rain chemistry nitrogen deposition acidification long term trends Temporal and spatial patterns in the chemistry of wet deposition in Southern Alps Rogora M.; Colombo L.; Marchetto A.; Mosello R.; Steingruber S. CNR Institute of Ecosystem Study, Largo Tonolli 50, Verbania Pallanza, I 28922, , Italy; University of Applied Sciences and Arts of Southern Switzerland SUPSI , Canobbio, CH 6952, , Switzerland; Ufficio dell aria, del clima e delle energie rinnovabili, Dipartimento del territorio del Cantone Ticino, Bellinzona, CH 6501, , Switzerland In the last decades, in Europe a large effort was carried out to reduce sulphur and nitrogen emission in the atmosphere, in order to improve air quality and reduce the acidity of atmospheric deposition and the amount of nitrogen compounds it carries to terrestrial and aquatic ecosystems. This resulted in a sharp decrease in the deposition of sulphate and acidity, while until recently a decrease of the atmospheric load of nitrogen compounds was not evident. In this paper, we focus on the subalpine and alpine areas in North Western Italy and Southern Switzerland Canton Ticino , receiving high deposition of atmospheric pollutants transported from emission sources in the Po Valley, one of the most urbanised and industrialised areas of Europe. Long term studies, covering a 30 year period 1984 2014 , were carried out on the chemistry of atmospheric deposition in this area and its effects on surface water bodies through a cooperation between Swiss and Italian research institutions. A total of 14 atmospheric deposition wet only sampling sites operate in this area, covering a wide latitudinal and altitudinal range about 200 1900 m a.s.l. . A spatial gradient in the deposition of sulphate and nitrogen compounds was evident both in the 1990s and in recent times 2008 2012 , with highest values in the south eastern part of the area, close to the major emission sources. Deposition also varied depending on local topography. The analysis of long term trends revealed a large proportion of significant decreasing trends in the concentration of both sulphate and nitrogen compounds. Deposition changes were less evident, due to the high interannual variability in the data, caused by the highly variable precipitation amount, ranging from 1200 1300 mm in dry years to 3000 mm in wet years. Sulphate concentrations and deposition decreased steadily since the 1980s, while ammonium and nitrate showed a widespread decrease only in the most recent period after 2006 . However, nitrogen wet deposition is still high with respect to critical loads inorganic N deposition ranges from 60 70 meq m 2 y 1 as the sum of ammonium and nitrate at the alpine sites to 120 140 meq m 2 y 1 at the southern lowland sites. Deposition of ammonium has acquired an increasing importance in time, especially at the southern, more polluted sites the relative contribution of reduced N to wet N deposition passed from about 50% in the early 1990s to 56 57% in recent years. The observed temporal changes in nitrogen deposition followed the emission decrease but with a delay. This aspect may be relevant in monitoring the effects of emission reductions as a result of the enforcements of international and national regulations. 146 Published version https //www.sciencedirect.com/science/article/pii/S1352231016304587 via%3Dihub Rogora_etal_AtmEnvir_2016 Versione pubblicata Rogora_etal_AtmEnv_2016.pdf Articolo in rivista Pergamon. 1352 2310 Atmospheric environment 1994 Atmospheric environment 1994 Atmos. environ. 1994 aldo.marchetto MARCHETTO ALDO michela.rogora ROGORA MICHELA rosario.mosello MOSELLO ROSARIO |
