TITLE:

Surface Kosan Chemistry, Dimethylsulfide & Carbondisulfide (DMS & CS₂)

Hilton B. Swan

Australian Government Analytical Laboratories (AGAL)

1 Suakin Street (PO Box 385) Pymble, New South Wales 2073, Australia.

Tel: 61 2 94490111 Fax 61 2 94491653

Real-time DMS and CS₂ for the period April 5-26 (DOY 95-116) 2001.

Collected at Kosan, Cheju Island (33°17’N, 126°10’E). Sample intake 10m above ground level (~70m ASL).

Sampling was undertaken using automated cryogenic concentration with analysis by gas chromatography with pulsed flame photometric detection (GC-PFPD). Reference to this instrumentation, also used during ACE-1, is;

Swan HB & Ivey JP (1999), Evaluation of two sulfur specific detectors for the measurement of dimethylsulfide gas concentrations at Macquarie Island and Cape grim during ACE-1, in Baseline Atmospheric Program (Australia) 1996, pages 15-23. Bureau of Meteorology and CSIRO Division of Atmospheric Research, Melbourne Australia.

Samples were collected over 15 minutes followed by a 7-minute analysis time. The time assignment for each sample is at the beginning of the 15-minute collection period while each sample is separated by 22 minutes. Some gaps in the data exist as a result of instrument maintenance and operation checks. The instrument was able to run up to 7 hours unattended and as a result there is a missing data period of ~5 hours per day due to the cryogenic reservoir running dry overnight.

There are 910 entries each of DMS & CS₂ in the dataset. Concentrations are expressed as ng (as Sulfur) per cubic meter, and as nmol (compound) per cubic meter. A zero (0) entry in the dataset means that the concentration was less than the detection limit of ~5ng(as S)/m³. Date/time is in UTC in the recommended format YYYYMMDDHHmm.

Calibration was achieved using internal standardisation via a NIST certified permeation standard of methylethylsulfide (MES). This standard was gravimetrically checked over the year prior to its use during the ACE-Asia IOP (see accompanying chart) and found to be consistent with its certified value. The PFPD response linearity for DMS, CS₂ and MES was checked prior to the IOP using calibration loops of different volumes.

During the IOP periodic checks were made of the correct operation of the instrument, and DMS & CS₂ chromatographic retention times were checked, by standard addition of permeation standards at the sample inlet. Also during the IOP many repeated measurements were made to determine variations in the parameters contributing to the determination of the sulfur-gas concentrations. From these parameters and their measured uncertainties, the overall measurement uncertainty for the dataset was calculated using Eurachem/Citac principles. The expanded relative measurement uncertainty was determined to be 9.4% (at 95% ci) for the dataset collected, (refer to accompanying Eurachem spreadsheet examples for details).