Sde Boker, in the Negev Desert of Israel, is a long-term station for investigating anthropogenic and natural aerosols in the eastern Mediterranean in the framework of the Aerosol, Radiation and ...Chemistry Experiment (ARACHNE). Ground-level measurements of physical and chemical properties of aerosols and supporting trace gases were performed during an intensive campaign in summer 1996 (ARACHNE-96). Fine non sea salt (nss)-SO4(2-) averaged 8 +/- 3 micro-g/cu m and fine black carbon averaged 1.4 +/- 0.5 micro-g/cu m, comparable to values observed off the east coast of the U.S. Optical parameters relevant for radiative forcing calculations were determined. The lack of correlation between SO2 and nss-SO4(2-) indicates that the conversion of regional SO2 into the particulate phase is not an efficient process in summerm, and that aged pollution dominates the accumulation mode particle concentrations. (Author)
Carbonyl sulfide (COS) mixing ratioswere measured in the marine atmosphere and in airequilibrated with surface sea water during severalcruises in the North Sea and western NorthAtlantic. In April ...1994, North Sea waters weresupersaturated with respect to the atmosphere,resulting in oceanic emissions of COS. Saturationratios varied between the equilibrium value of one inthe central North Sea and high values of >15 in theElbe Estuary. We observed weak diel cycles of surfacewater COS during a three day drift station. During theunderway parts of the cruise, diel COS variations weremasked by the high geographical variability of COSconcentrations in the German Bight. In August 1994, weobserved a pronounced diel cycle of COS off theFlorida coast with saturation ratios varying betweenthe equilibrium value of one in the early morning andmaximum values of four to five in the afternoon. InMarch 1995, we found COS supersaturation as well asextensive undersaturation in the western NorthAtlantic between Norfolk, VA, and Bermuda. Suchundersaturation in marine surface waters results inregional and seasonal uptake of atmospheric COS. Basedon our data and those of other researchers, weestimate the global oceanic COS net emission to bebetween 1.3 and 2.5 Gmol yr^sup -1^. This estimate is significantly smaller than previous ones which had notconsidered the possibility of COS uptake by theoceans. COS hydrolysis in the ocean has a significantinfluence on the atmospheric turnover time of COS,which we estimate to be 5.7 yr. This may contribute tothe lack of an observable increase in atmospheric COSlevels despite substantial anthropogenic emissions.PUBLICATION ABSTRACT
The uptake of arsenate from sea water, the biosynthesis of organo-arsenic compounds and the release of arsenite, methyl arsonate and dimethyl arsinate were studied in pure cultures of bacteria-free ...marine phytoplankton. Substantial amounts of arsenic became bound to cell structures, and up to 12 soluble organo-arsenic compounds were also formed by the algae. All species released methyl arsonate and dimethyl arsinate and production of arsenite was also common .
The concentration of dimethylsulfide (DMS) and supporting parameters were determined on longshore and cross-shelf traverses in the Peru upwelling area. Vertical DMS profiles were measured at several ...stations in the marine water column and in the sedimentary porewaters. The distribution of DMS in surface waters is related to the patchiness of the upwelling process and of the resulting phytoplankton biomass. Substantial concentrations of DMS were found in the sedimentary porewaters, with a sharp maximum a few centimeters below the sediment-water interface. The source of this DMS is most likely the decomposition of algal material which settles to the bottom beneath the upwelling areas. The rates of DMS production in the water column and its flux into the atmosphere across the air-sea interface are only a small fraction of the rate of sulfate assimilation by the plankton community. The concentrations of DMS in the surface waters of the Peru shelf are similar to those found in other coastal areas; the fluxes of reduced sulfur gases to the atmosphere from this upwelling region do not require special consideration in the global atmospheric sulfur budget.
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