SO2 measurements in a clean coastal environment of the southwestern Europe: Sources, transport and influence in the formation of secondary aerosols

J A Adame; L Lope; M Sorribas; A Notario; M Yela

doi:10.1016/j.scitotenv.2020.137075

SO₂ measurements in a clean coastal environment of the southwestern Europe: Sources, transport and influence in the formation of secondary aerosols

Sci Total Environ. 2020 May 10:716:137075. doi: 10.1016/j.scitotenv.2020.137075. Epub 2020 Feb 1.

Authors

J A Adame¹, L Lope², M Sorribas², A Notario³, M Yela²

Affiliations

¹ Atmospheric Sounding Station - El Arenosillo, Atmospheric Research and Instrumentation Branch, National Institute for Aerospace Technology, INTA, Mazagón, Huelva, Spain. Electronic address: adamecj@inta.es.
² Atmospheric Sounding Station - El Arenosillo, Atmospheric Research and Instrumentation Branch, National Institute for Aerospace Technology, INTA, Mazagón, Huelva, Spain.
³ Universidad de Castilla-La Mancha, Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Ciudad Real, Spain; Universidad de Castilla La Mancha, Instituto de Investigación en Combustión y Contaminación Atmosférica, Camino de Moledores s/n, Ciudad Real, Spain.

PMID: 32044490
DOI: 10.1016/j.scitotenv.2020.137075

Abstract

Two years of SO₂ measurements at El Arenosillo observatory located in the Gulf of Cadiz (Atlantic Ocean) were investigated. Annual hourly averages of 1.9 ± 1.5 μg m^-³ and p95 between 3 and 4.4 μg m^-³ were recorded, showing clean and background environments. Monthly means vary between 1.5 and 2.4 μg m^-³, a monthly evolution was not found. SO₂ fields from the MERRA2 model were used to identify SO₂ sources and its transport, which could be affecting the studied region. Although SO₂ records were low, major conductive for SO₂ increases were observed in specific periods. A selection methodology was applied to extract these events, which showed a mean of ~11 μg m^-³. Surface meteorological observations and ERA5 meteorological fields from the ECMWF model were used to assess the weather conditions. SO₂ increases, in cold months occurred under conditions governed by synoptic-scale. Two types of transport scenarios were identified: SO₂ transport defined as direct impact, which is the sum of the plumes from Portugal and the Huelva area; and indirect impact, where SO₂ and sulphate particle emissions from Portugal were transported and accumulated in the Gulf of Cadiz and then carried inland, where new particle formation were observed. Episodes with high SO₂ concentrations were also reported in warm periods associated with pure sea-land breezes. The SO₂ peaks under sea-land breezes were associated with the transport of SO₂ from the south of Portugal to the Gulf of Cadiz, whereas SO₂ from the east of the Iberian Peninsula and north of Africa reached the Mediterranean Sea and were then transported to the Atlantic Ocean following the Strait of Gibraltar. Blocking of the airflows from the Mediterranean Sea to the Atlantic Ocean turns the Gulf of Cadiz into a chemical reservoir, where chemical species such as SO₂ can accumulate, triggering new particle formation processes.

Keywords: ERA5; MERRA2 model; New particle formation; SO(2) measurements; Sulphate particles.