Stream chemistry response to changing nitrogen and sulfur deposition in two mountain areas in the Iberian Peninsula

A Avila; R Molowny-Horas; L Camarero

doi:10.1016/j.scitotenv.2019.134697

Stream chemistry response to changing nitrogen and sulfur deposition in two mountain areas in the Iberian Peninsula

Sci Total Environ. 2020 Apr 1:711:134697. doi: 10.1016/j.scitotenv.2019.134697. Epub 2019 Nov 22.

Authors

A Avila¹, R Molowny-Horas², L Camarero³

Affiliations

¹ CREAF, Bellaterra (Cerdanyola del Vallès), Catalonia E08193, Spain. Electronic address: anna.avila@uab.cat.
² CREAF, Bellaterra (Cerdanyola del Vallès), Catalonia E08193, Spain.
³ CEAB-CSIC, C/Accés Cala Sant Francesc 14, Blanes, Catalonia E17300, Spain.

PMID: 31818551
DOI: 10.1016/j.scitotenv.2019.134697

Abstract

Sulfur (S) and nitrogen (N) increasing anthropogenic emissions in the last century has arisen wide concern on the ecological effects of S and N deposition. In this paper, we use bulk deposition and stream water measurements in the central Pyrenees (PYR-C and PYR-AT sites) and Montseny (MSY-TM0) covering different time lengths in the period 1983-2017 to investigate how these mountain environments respond to ongoing changes of regional emissions to the atmosphere. PYR-C, in spite of its position far away from urban and industrial areas, presented higher SO₄-S, NO₃-N and NH₄-N bulk deposition than the Montseny site closer to Barcelona and the inclusion of dry deposition only reversed this pattern for NO₃-N. This indicates that distance to pollution sources does not protect these mountain sites from a considerable impact of pollution. Time-trends in SO₄^2- and NO₃^- concentrations in bulk deposition were similar between sites: SO₄^2- monotonically decreased, while NO₃^- increased until the mid-2000 s and decreased thereafter. In the period 1983 to 2017, SO₂ emissions in Europe (EU-28) decreased by 95%, while in the SO₄^2- concentrations in bulk deposition declined by 35-50% in Pyrenees and Montseny respectively and SO₄^2- concentrations in the streams by 25-35%, respectively. Other sources of SO₄^2- (e.g. episodic African dust) may explain the different reduction rate between anthropogenic emissions and bulk deposition. Net S budget was positive for MSY-TM0 (indicating flushing from the catchment) and negative for the PYR-C site (indicating retention), while it was close to zero for the other Pyrenean site, but in the PYR-C site net retention showed a significant increasing trend tending to lower retention in recent years. Bulk N deposition in the Pyrenees was lower but stream concentrations and export was higher than at Montseny, this leading to less N retention in the Pyrenean sites. However, the MSY-TM0 site showed a trend towards less N retention in recent years. This was driven by higher exports during the wet months, which would correspond to a first stage of N saturation according Stoddard's classification.

Keywords: Air pollution; Atmospheric deposition; Emissions; Mountain ecosystems; Nitrogen; Stream water chemistry; Sulfur.