Isotopic composition of sulfur in size‐resolved marine aerosols above the Atlantic Ocean

Abstract

Abstract. Sulfur isotope measurements were performed on size-segregated aerosols collected during the Albatross oceanographic campaign from 61øN to 35øS above the Atlantic Ocean in October and November 1996. Results obviously showed the dependence of the sulfur isotope ratio upon particle size, the finest particles being depleted in*4S compared to coarse particles, suggesting a heavier continental influence in the fine mode. In the coarse mode, 50-90% of the excess sulfate in both hemispheres was found to be of biogenic origin. In the fine mode a different picture was obtained. In the Northern Hemisphere the contribution ofbiogenic sulfur was found to be less than 35% of the excess sulfur even in relatively clean air masses. On the other hand, in the Southern Hemisphere the participation of biogenic sulfur was about 60% of the excess sulfur in purely marine air. The contribution of continental sulfur to the fine fraction in the Southern Hemisphere was up to 40 + 25% even under pure oceanic conditions and far more in the Northern Hemisphere. These results attest to the possible importance of long-range transport of fine sulfate particles or SO2, possibly through the free troposphere, or the importance of anthropogenic emissions due to shipping.

Fractionation of sulfur isotopes during heterogeneous oxidation of SO<sub>2</sub> on sea salt aerosol: a new tool to investigate non-sea salt sulfate production in the marine boundary layer

“…In some samples an isotopically-light "continental" influence was seen although the back trajectories showed a pure marine origin of the air mass (Patris et al, 2000). δ 34 S of nss-sulfate is lower in smaller particles, which has been attributed to a larger continental influence in these particles (Turekian et al, 2001;Patris et al, 2000Patris et al, , 2007.…”

“…Many of these studies have employed a three-source mixing scheme, explaining sulfur isotope observations with mixing between 34 S-enriched sea salt sulfate and marine biogenic nss-sulfate, and a 34 S-depleted source that is attributed to anthropogenic or continental sulfate (Patris et al, 2000;Wadleigh, 2004;Turekian et al, 2001). The general success of this mixing model suggests isotopic fractionation has overall only a small effect on measured δ 34 S of nss-sulfate, thus it is likely the amount of sulfate produced by 34 S-enriching, alkalinity limited pathways (O 3 oxidation and Cl-catalysis) is roughly equal to that from 34 S-depleting pathways (Fecatalysis and hypohalite oxidation).…”

The effect of physical and chemical aerosol properties on warm cloud droplet activation

“…The seasonality is due to variations in the number concentrations in the Aitken and Accumulation mode. Adapted from Weingartner et al (1999). of sulfate can be important far from land (Heintzenberg et al, 2000;Patris et al, 2000;Putaud et al, 2000). Downward mixing is important and frontal passages and other meteorology are very important in determining the number of sulfate particles available (Bates, 1999).…”

Seasonal δ34S variations in two high elevation snow pits measured by 33S–36S double spike thermal ionization mass spectrometry

“…The isotopic composition of marine biogenic SO 4 2À lies between +14& and +22& (Calhoun et al, 1991), which is close to that of sea water (+21 ± 0.2& (1r) 1978). Sulfate aerosols collected from above the Atlantic and Pacific oceans have isotope compositions that fall within this range (Calhoun et al, 1991;Patris et al, 2000b); however, Patris et al (2000b) suggested that the lighter values could be influenced by S sourced from weathered sulfide minerals in continental soils. Based on the measurement of background SO 4 2À contained in snow at the South Pole, which is dominated by marine biogenic inputs and void of continental influences, Patris et al (2000a) suggested that a d 34 S value of +18.6 ± 0.9& (1r) is a better estimate of the marine biogenic component.…”

“…The S isotope composition of remote marine and polar SO 4 2À aerosols sampled directly on filters has been used to identify source inputs to distant regions (Calhoun et al, 1991;Nriagu et al, 1991;Norman et al, 1999;Patris et al, 2000b). The S isotope signatures of both shallow Antarctic ice cores and discontinuous Greenland ice core samples have been used to examine historical variations in SO 4 2À sources (Patris et al, 2000a(Patris et al, , 2002Pruett et al, 2004a,b).…”