Vertical distribution of dimethylsulfide, sulfur dioxide, aerosol ions, and radon over the Northeast Pacific Ocean

Abstract

Dimethylsulfide (DMS), sulfur dioxide (SO2), methanesulfonate (MSA), nonsea-salt sulfate (nss-SO~4-), sodium (Na+), ammonium (NH~), and nitrate (NO~) were determined in samples collected by aircraft over the open ocean in postfrontal maritime air masses off the northwest coast of the United States (3-12 May 1985). Measurements of radon daughter concentrations and isentropic trajectory calculations suggested that these air masses had been over the Pacific for 4-8 days since leaving the Asian continent. The DMS and MSA profiles showed very similar structures, with typical concentrations of 0.3-1.2 and 0.25-0.31 nmol m -3 (STP) respectively in the mixed layer, decreasing to 0.01-0.12 and 0.03-0.13 nmol m -3 (STP) at 3.6 km. These low atmospheric DMS concentrations are consistent with low levels of DMS measured in the surface waters of the northeastern Pacific during the study period.The atmospheric SO2 concentrations always increased with altitude from <0.16-0.25 to 0.44-1.31 nmol m -3 (STP). The nonsea-salt sulfate (nss-SO~4-) concentrations decreased with altitude in the boundary layer and increased again in the free troposphere. These data suggest that, at least under the conditions prevailing during our flights, the production of SO2 and nss-SO~4-from DMS oxidation was significant only within the boundary layer and that transport from Asia dominated the sulfur cycle in the free troposphere. The existence of a 'sea-salt inversion layer' was reflected in the profiles of those aerosol components, e.g., Na + and NO~, which were predominantly present as coarse particles. Our results show that long-range transport at mid-tropospheric levels plays an important role in determining the chemical composition of the atmosphere even in apparently 'remote' northern hemispheric regions.

Size distribution, shape, and composition of mineral dust aerosols collected during the African Monsoon Multidisciplinary Analysis Special Observation Period 0: Dust and Biomass‐Burning Experiment field campaign in Niger, January 2006

“…It is described in detail by Andreae et al [2000]. The aerosol inlet consists of a thin-walled inlet nozzle with a curved leading edge; the design was based on criteria for aircraft engine intakes at low Mach numbers [Andreae et al, 1988]. This design reduces distortion of the pressure field at the nozzle tip and the resulting problems associated with flow separation and turbulence.…”

Physico‐chemical and optical properties of Sahelian and Saharan mineral dust: in situ measurements during the GERBILS campaign

“…The aerosol sampling system onboard the BAe-146 consists of a thin-walled inlet nozzle with a curved leading edge (Andreae et al, 1988). Sampling is conducted under sub-isokinetic conditions.…”

Motivation, rationale and key results from the GERBILS Saharan dust measurement campaign

“…Corrections were made for refractive index by assuming the refractive index of Balkanski et al (2007) with a haematite content of 1.5%, and shape by assuming irregular shaped particles and using combinations of Mie scattering, T-matrix, and ray tracing techniques 3-wavelength nephelometer and particle soot absorption photometer (PSAP), which were corrected for non-ideal scattering (Anderson and Ogren, 1998), and absorption artefacts (Bond et al, 1999). The filter measurement system (Klaver et al, 2011) consists of thin-walled nozzles (Andreae et al, 1998) with curved leading edges leading to two stacked filter units under sub-isokinetic conditions. Each stacked filter unit consisted of a Nucleopore filter of 47 mm diameter and nominal pore size 0.4 µm.…”