No abstract

Measurements of atmospheric sulphur species made in Southern Ocean air, at the Cape Grim Baseline Air Pollution Station, are reviewed in an attempt to discern the role played by oceanic emissions of dimethyl sulphide (DMS) as a source of cloud condensation nuclei (CCN). Consistent with conclusions reached by others, our data indicate that the connection between DMS concentration and CCN concentration is neither simple nor direct, being mediated through a range of chemical pathways and intermediate species that are subject to considerable variability over timescales ranging from minutes to months. Physical and meteorological processes are no less important than chemical processes as sources of complexity in the DMS CCN transformation process. Moreover, the considerable uncertainty that currently exists about both the number of chemical pathways involved in DMS oxidation, and the kinetic coefficients associated with the proposed pathways, make quantitative modelling studies problematic. Nevertheless, synthesis of a large body of data available from Cape Grim and other Southern Ocean sites does permit some refinement of our understanding of the DMS-CCN connection. Here, these data are employed to illustrate the current state of knowledge about the connections between DMS, CCN and cloud properties at Cape Grim, and to highlight the many complexities that underlie these connections.

Concentrations of dimethylsulfoniopropionate (DMSP), dimethylsulfide (DMS), and DMS flux are reported for the Great Barrier Reef (GBR), Great Barrier Reef Lagoon (GBRL), and Coral Sea. Generally higher concentrations of dimethylsulfoniopropionate and DMS occurred in coral reef waters, compared with GBRL concentrations. DMS flux from GBR coral reefs in summer ranged from nondetectable to 153 μmol m−2 d−1 (mean 6.4), while winter fluxes ranged from 0.02 to 15 μmol m−2 d−1 (mean 2.4). No significant seasonal difference in DMS flux occurred for the GBRL. High DMSw concentrations and DMS fluxes periodically occur at coral reefs during very low tides and elevated sea surface temperatures (SSTs). For the GBRL and GBR coral reefs there was a significant correlation between seawater DMSw concentrations and SST (p < 0.001), up to temperatures of 30 °C. During coral bleaching DMS flux from reefs almost completely shuts down when SSTs are >30 °C. The GBRL and associated coral reefs emit 439 and 32 MmolS per year, respectively. Cyclones on average produce 170 MmolS to the GBR atmosphere in summer. This amount can markedly increase during severe cyclones such as severe tropical Cyclone Debbie in March 2017. Overall, the annual DMS emission estimate from the GBRL and coral reefs in the GBR is 0.64 GmolS, with cyclones contributing 27% or greater of the annual emission estimate, depending on the cyclone intensity. Oxidation of atmospheric DMS can potentially affect solar radiation, SSTs, low‐level cloud cover, and rainfall causing cooling and warming of the climate in the GBR region as recent modeling predicts.

Although sufficient progenitor cells for hematopoietic rescue following high-dose therapy may be obtained in a single leukapheresis, the majority of patients require multiple procedures. In an attempt to minimize the number of leukapheresis and maximize collection efficiency, we undertook large-volume leukapheresis in 17 patients with a variety of hematologic malignancies. Twenty-four procedures were performed over a 6-h period, with a mean of 21 L of blood processed. By employing a modified collection set, three separate 2-h collection bags were analyzed for a number of variables. CD34+ cells are collected at a steady rate throughout the procedure, with no evidence of exhaustion of progenitor cells. There was evidence of progenitor cell recruitment, with 1.4-fold more CD34+ cells in the collected product than were present in the blood at the beginning of the procedure. Initiation of leukapheresis was based on the blood CD34+ count, and this value was strongly correlated with the number of CD34+ cells in the collected product. The procedure is safe and relatively simple and minimizes the number of leukaphereses required to collect adequate progenitors for autologous transplantation.

High-volume aerosol filters, exposed in maritime air masses at Cape Grim since late 1976, were analysed for excess sulfate (not of seasalt origin) and methanesulfonate. The mean c~ncentratlons (standard errors) of 2.80(0.59) and 0.176(0.027) nmole/m J respectively are about half those reported in a recent study of aerosol samples from various locations in the Atlantic and Pacific oceans.Methanesulfonate concentration varied seasonally by at least an order of magnitude with a summer maximum and winter minimum.No comparable cycle was found for excess sulfate.KEY WORDS. Aerosol sulfate, aerosol methanesulfonate, marine aerosol.