Non-seasalt

Fig. 1-2 Chemical data from the Vostok ice core. The graph of 5D can be taken as a proxy for temperature changes, as described in Chapter 18. CO2 and CH4 are greenhouse gases and vary in the same direction as temperature. Non-seasalt sulfate and methane sulfonic acid are both sulfur species existing in the particle phase, and are positively correlated with each other, but negatively with T. Major variations for all of these variables seem to correlate either positively or negatively with each other, indicating a coupled system. <5D, non-seasalt sulfate, and methane sulfonic acid data kindly provided by Dr Eric Saltzman. CO2 data are from Bamola et al. (1987) and Jouzel et al. (1993). CH4 data are from Chappellaz et al. (1990) and Jouzel et al. (1993). (ppmv = parts per million by volume ppbv = parts per billion by volime)...

The definition of turnover time is total burden within a reservoir divided by the flux out of that reservoir - in symbols, t = M/S (see Chapter 4). A typical value for the flux of non-seasalt sulfate (nss-SOl"") to the ocean surface via rain is 0.11 g S/m per year (Galloway, 1985). Using this value, we may consider the residence time of nss-S04 itself and of total non-seasalt sulfur over the world oceans. Appropriate vertical column burdens (derived from the data review of Toon et ai, 1987) are 460 fxg S/m for nss-801 and 1700 jig S/m for the sum of DMS, SO2, and nss-S04. These numbers yield residence times of about 1.5 days for nss-S04 and 5.6 days for total non-seasalt sulfur. We might infer that the oxidation process is frequently... 

To determine the non-seasalt (nSS) contributions of trace elements we have normalized mean concentrations of ions to Cl and subtracted the contributions from seasalt (Nozaki, 1997). We assume that all of the Cl" in the sample was from marine aerosol or marine-derived salt and nSS major ions and trace elements can be calculated. For example the percentage of nSS-S042 is calculated as ... 

WA water quality labs by atomic absorption and autoanalyzer techniques. Charge balance calculations Indicated that all dissolved species of significance were analyzed. Comparison of filtered and unflltered aliquots suggested that un-lonlzed species were not present In appreciable quantities. Sampling and analysis uncertainties were determined by the operation of two co-located samplers for 16 weeks. The calcium and sulfate data were corrected for the Influence of sea salt to aid In the separation of the factors. This correction was calculated from bulk sea water composition and the chloride concentration In rainwater (11). Non seasalt sulfate and calcium are termed "excess" and flagged by a ... 

The two EUSAAR/ACTRIS stations in the Britain and Irish stations show not only a significant inter-station variability, but also many similarities. The stations have high seasonal variation and large variance in intra-seasonal concentrations. The station data show a prominent spring-summer maximum in all sizes from 30 to 70 nm. The variability was probably due to occurrences of both clean Atlantic and polluted local air masses, and the maximum value at Mace Head during summer months can be attributed to enchanted marine biota activity, which increases the sub-micron particle mass concentration of non-seasalt sulfate and organic aerosol [21],... 

The presence of non-seasalt sulfate particles in the remote marine atmosphere has important environmental consequences. As a result of their size and hydrophylicity, sulfate particles make good cloud condensation nuclei... 

Atmospheric Aerosol Non-Seasalt Sulfate Non-Remote Marine -10 to +13 San Francisco Bay -10 to +12 N.W. Atlantic + 7 to +13 HBEF, non-urban US +1 to +4 Miami, Florida +1 to +2 Mauna Loa Observatory +4 to +6 Ludwig (22) Gravenhorst (22) Saltzman et al. (24) Saltzman (pers. commun.) Zoller Kelly (pers. commun.)... 

Atmospheric Aerosol Sulfate. Isotope measurements of non-seasalt sulfate in marine aerosols (24.52.631 require that sulfate from sea spray be either physically or mathematically removed from the sample medium. Mathematically, mass balance relationships are used to correct the value for the presence of seasalt sulfate in the sample. Physical means employ impactors or cyclone separators to segregate particles based on size so that value for non-seasalt sulfate can be directly measured. 

It is already possible to measure the values for seawater sulfate, DMSP, and seawater DMS, but only minimal data exist. Coordinated measurements of these compounds, along with simultaneous 634S measurements of atmospheric DMS, S02, methane sulfonate and non-seasalt sulfate, from atmospheres free of continental influence, are needed. These data will help in the isotopic interpretation of sulfur sources so that their relative contributions to the remote atmosphere can be assessed. 

Figure 22 Observed annual average concentrations of non-seasalt sulfate (cf. text) at stations in the North and South Atlantic (triangles) and predictions from several chemical transport models (line codes and acronyms are shown at upper right). Data were provided by D. Savoie and J. Prospero (University of Miami). Stations along the bottom axis refer to Heimaey, Iceland (HEI) Mace Head, Ireland (MAH) Bermuda (BER) Izania (IZO) Miami, Florida (RMA) Ragged Point, Barbados (BAR) Cape Point, South Africa (CPT) King George Island (KGI) and Palmer Station, Antarctica (PAL). From Penner et al. (2001) (reproduced by permission of Intergovernmental Panel...

The sulfate that derives from seasalt is called seasalt sulfate. It is important to distinguish it from sulfates that are found in the marine aerosol from the oxidation of gaseous sulfur compounds, which are known as non-seasalt sulfate. 

These marine sources of reduced sulfur gases can be important as a source of sulfur to the continents. The gypsum accumulations of the hyper-arid Central Namib Desert seem to be mainly derived from non-seasalt sulfur, in particular oxidation products of marine DMS (Eckardt and Spiro, 1999). 

Dimethylsulfoxide can readily be removed onto particles and there it can undergo an efficient oxidation through to methanesulfonate. This adds a significant pathway to the gas-phase production of methanesulfonic acid, which is present largely in the submicron aerosol fraction. Peak summer concentrations are 0.6 0.3 nmol m and at times this can amount to almost a quarter of the non-seasalt sulfate in the remote marine atmosphere (Jourdain and Legrand, 2001). 

Dimethylsulfoxide is also oxidized to SO2, which can then be converted onto non-seasalt sulfate. The yield probably ranges from 50% to 100% in the tropics with the potential for it to be somewhat lower, perhaps 20-40% in mid-latitudes (de Bruyn et al, 2002). 

Jourdain B. and Legrand M. (2001) Seasonal variations of atmospheric dimethylsulfide, dimethylsulfoxide, sulfur dioxide, methanesulfonate, and non-seasalt sulfate aerosols at Dumont d Urville (coastal Antarctica) (December 1998 to July 1999). J. Geophys. Res. Atmos. 106(D13), 14391-14408. 

Lacustrine Pertaining to development in lakes Mesic This term has a very broad meaning. In ecology, it refers to moderate conditions with respect to both temperature and moisture. In soil, specifically in soil taxonomy, mesic is used to represent a soil temperature (mean annual) that falls in the range 8-15° C Mole fraction The ratio of the moles of a substance to the total number of moles in the sample. In the atmosphere this is the same as the volume fraction Non-seasalt (nss) The amount of an element or compound in the bulk aerosol mass that is in excess of its seawater ratio with sodium or chloride. Often applied to sulfate Obligatory anaerobes Organisms restricted to life in anaerobic environments... 

Savoie, D. L., and Prospero, J. M. (1989) Comparison of oceanic and continental sources of non-seasalt sulfate over the Pacific ocean, Nature 339, 685-687. 

Zhuang, H., C. K. Chan, M. Fang, and A. S. Wexler (1999) Formation of nitrate and non-seasalt sulfate on coarse particles. Atmospheric Environment 33, 4223-4233... 

Recently, several articles have appeared on the combined use of different other microanalysis techniques for atmospheric aerosols. Let us mention one. Hopkins et al. successfully used CC SEM/EDX, time-of-flight secondary ion mass spectrometry (TOF-SIMS) and scanning transmission X-ray microscopy/near-edge X-ray absorption fine structure analysis (STXM/NEXAFS) to study quantitatively methanesulphonate (CHsSOs") and non-sea salt sulphate in individual marine aerosol particles. This indicated e.g. that CHsSOs" salts were the dominant source of non-seasalt sulphur in large particles, while sulphate was more common in smaller particles. Quantitative assessment of these two forms is important for kinetic modelling concerning the pathways of natural dimethylsulphide oxidation and the impact on the number and size of cloud condensation nuclei in the marine environment. 

---