Electrochemical Evidence of non-Volatile Reduced Sulfur Species in Water-Soluble Fraction of Fine Marine Aerosols

Abstract

The traditional voltammetric method at the mercury electrode, and an acidification step developed for the determination of reduced sulfur species (RSS) in natural waters, was for the first time used for the quantification of RSS in the water-soluble fraction of fine marine aerosols collected at the Middle Adriatic location (Rogoznica Lake). The evidence of two types of non-volatile RSS that have different interaction with the Hg electrode was confirmed: mercapto-type which complexes Hg as RS–Hg and sulfide/S0-like compounds which deposits HgS. The analytical protocol that was used for RSS determination in aerosol samples is based on separate voltammetric studies of a methyl 3-mercaptopropionate (3-MPA) as a representative of mercapto-type compounds and sulfide as a representative of inorganic RSS. Our preliminary study indicates the presence of mainly RS–Hg compounds in spring samples, ranging from 2.60–15.40 ng m−3, while both, the mercapto-type (0.48–2.23 ng m−3) and sulfide and/or S0-like compounds (0.02–0.26 ng m−3) were detected in early autumn samples. More expressed and defined RS–Hg peaks recorded in the spring potentially indicate their association with biological activity in the area. Those samples were also characterized by a higher water-soluble organic carbon content and a more abundant surface-active fraction, pointing to enhanced solubility and stabilization of RSS in the aqueous atmospheric phase.

Physico-Chemical Characterization of an Urban Rainwater (Zagreb, Croatia)

“…The oligomers, organosulfates, and nitrooxy organosulfates obtained in the atmospheric samples could play a significant part in the HULIS fraction of atmospheric organic matter [27] and could contain electrochemically active sulfur as already shown for the same type of organic materials isolated from the lagoon and marine sediments [72,75]. Such complex organic material could contribute to higher solubility and stabilization of volatile RSS in the atmospheric aqueous-phase, as is similarly obtained for natural organic macromolecules and S 0 in the seawater and water-soluble fraction of marine aerosol particles [72,73]. Sulfur-containing compounds in the class of carbohydrates and proteins have been recently identified in HULIS extracts of atmospheric aerosol particles collected in the coastal area of South Korea [76].…”

“…The study of RSS was performed by voltammetric measurements at the Hg electrode. The presence of two different types of RSS that have different interactions with the Hg was confirmed: tiol-type, which forms a complex with Hg, i.e., RS-Hg and sulfide/S 0 -like compounds which deposit the HgS [72,73]. The compounds that contribute to the RS-Hg interaction were removed by acidification and purging of the samples, indicative of their volatile nature.…”

“…The compounds that contribute to the RS-Hg interaction were removed by acidification and purging of the samples, indicative of their volatile nature. The acidification and purging step is usually used as an essential methodological step in the characterization of volatile and non-volatile RSS [41,72,73]. S 0 -like compounds that correspond to nonvolatile RSS contributed to the HgS behavior [41,72,73].…”

“…The acidification and purging step is usually used as an essential methodological step in the characterization of volatile and non-volatile RSS [41,72,73]. S 0 -like compounds that correspond to nonvolatile RSS contributed to the HgS behavior [41,72,73]. Concentration of volatile and nonvolatile RSS in all studied precipitation samples ranged between 2-8 nM (Table S4 in Supplementary Materials) equivalent to sulfide calibration [41].…”

Atmospheric Aqueous-Phase Chemistry

“…The articles of this Special Issue can be divided into three groups: (i) the first is mostly based on field measurements and/or combined field and modeling studies giving insights into the chemical characterization of different atmospheric liquid water samples from various environments [1][2][3][4]; (ii) the second group is focused on studies of aqueousphase reactivity of some important atmospheric organic compounds [5][6][7][8]; (iii) and the final group comprises articles based on predictive modeling and/or combined modeling and laboratory studies providing insight into aqueous secondary organic aerosol (SOA) formation [9,10].…”