Tropospheric arsenic over marine and continental regions

Abstract

Particulate and vapor concentrations of atmospheric as have been measured over various marine and continental areas. Particulate samples were collected on double Whatman 41 filters. Particulate‐vapor samples were collected using an in‐line filter system with a 0.45‐μm pore size Nuclepore filter as a particle prefilter in front of two Whatman 41 filters impregnated with tetrabutylammonium hydroxide and glycerol for vapor As collection. Arsenic determinations were by destructive neutron activation. The data from the Nuclepore‐impregnated filter samples indicates that the major fraction of As in the atmosphere is particulate but a vapor component of As is detectable, most frequently associated with high sampling temperatures and high total As concentrations. With the data presented here, estimates of representative global near‐surface concentrations of atmospheric arsenic have been made.

Considerations of the enrichment, sources, and flux of arsenic in the troposphere

“…For these estimates, arsenic is assumed to be entirely in particulate form and contained totally within the troposphere. Walsh et al [ 1979] have shown that vapor phase As constitutes less than 10% of the As present in near-surface air over marine and continental areas and that the major mass of As in these regions is on relatively small particles (d _< 1 #m). Representative surface concentrations of atmospheric arsenic in marine and continental areas have been estimated from measurements Area, m:…”

“…The arsenic emission factor of 5.7 X 10 -8 is the amount of arsenic per gram of sea salt [Pytkowicz and Kester, 1971]. The percent of less than 5-#m diameter particulates for this source is based on a mass rnediam diameter (MMD) of 5-#m for atmospheric sea-salt particles [Duce et at., 1976;Walsh et at., 1979]. The total arsenic production for this size range is calculated to be 0.028 X 10 •' g/yr.…”

“…The potential significance of arsenic emission as vapor or small particles from the ocean can be estimated from ambient measurements of arsenic in marine aerosols. Arsenic concentrations in marine aerosols are much lower than continental aerosols, and there is no evidence of a significant As vapor component in the marine atmosphere [Walsh et al, 1979]. If the ocean were a major source of the global burden of atmospheric arsenic, then the concentrations of arsenic in marine aerosols would be higher than observed.…”

“…In a previous paper [Walsh et al, 1979] the distribution of vapor phase and particulate As and the enrichment of arsenic in continental and marine aerosols, relative to crustal and marine sources, was discussed. The enrichment of arsenic in these aerosols is most likely due to some combination of anthropogenic and natural volatilization processes.…”

Arsenic Speciation in Atmospheric Aerosols at The Geysers

“…In the air, arsenic Is primarily associated with particles, although II also has been observed at much tower levels In the gas phase (Johnson and Braman 1975;Walsh et al 1977Walsh et al , 1979Appel et al 1984 (Solomon 1984), and the City of Industry, Los Angeles County, CaiHomla (Rabano et al 1989). The City of Industry slle was located wllhln 1 kilometer of a known high temperature IOUfCe of arsenic (a secondary lead smeller (ARB 1t90bJ).…”