Peter Brimblecombe

Thermodynamic modelling of aqueous aerosols containing electrolytes and dissolved organic compounds

Abstract A method for calculating the thermodynamic properties of soluble mixed inorganic/organic aerosols is proposed. It is based upon the use of existing models of inorganic (electrolyte) multicomponent solutions and water/organic mixtures in combination, together with simple thermodynamically consistent terms that express the effects of interactions between ions and organic molecules on the activities of all mixture components. The method is used to calculate the deliquescence properties of the following systems at 298.15 K: sodium chloride/sucrose/water, letovicite/2-butenedioic acid/water, and sodium chloride/butanoic acid/water. The effects of approximations in the ion–organic interaction terms are explored, and it is shown that the method can be used to model liquid/liquid phase separation in sodium chloride/butanoic acid/water mixtures. In this example, it is found that the phase separation results in total water uptake that differs little from that of pure sodium chloride.

Photo-oxidation of dimethylsulphide in aqueous solution

Abstract Dimethylsulphide (DMS) is readily photo-oxygenated in the presence of micromolar amounts of photosensitizers such as methylene blue, rose bengal, anthroquinone and humic acid. Two moles of DMS are oxidized for every mole of molecular oxygen utilized consistent with dimethyl-sulphoxide being the oxidation product. Coastal seawater samples examined contained sufficient naturally occurring photosensitizer to photo-oxygenate DMS in sunlight with a first order rate constant of 2.4 × 10 −5 s −1 . This rate is rapid enough to imply that DMS is oxidized at approximately the same rate as it is lost to the atmosphere.

The composition of museum atmospheres

Indoor pollutants can damage cultural property stored in museums, art galleries, libraries and archives. The paper reviews the atmospheric substances of concern and their sources. A relatively small number of measurements available for the interiors are restricted to just a few gases. The review draws attention to the lack of information about the key factors that control the composition of museum interiors, chemical transformations of pollutants in indoor air, the nature of emissions from materials used in creating displays and deposition velocities onto indoor surfaces.

Historical evidence for a dramatic increase in the nitrate component of acid rain

The concentrations of nitrate and ammonium ion in rainfall have an important effect on precipitation pH. We have collected sets of rainfall analyses from non-urban sites in North America and western Europe, which start from last century, and we show here that there is a marked increase in the annual deposit of nitrate ion compared with relatively stable levels of ammonium ion deposit. The increase apparent in the data from the US parallels the increases in nitrogen oxide emissions from combustion processes and is large enough for the nitrate ion to contribute almost as much to the acidity of rainfall as the sulphate ion.

Iron and sulfur in the pre-biologic ocean.

Tentative geochemical cycles for the pre-biologic Earth are developed by comparing the relative fluxes of oxygen, dissolved iron, and sulfide to the atmosphere and ocean. The flux of iron is found to exceed both the oxygen and the sulfide fluxes. Because of the insolubility of iron oxides and sulfides the implication is that dissolved iron was fairly abundant and that oxygen and sulfide were rare in the atmosphere and ocean. Sulfate, produced by the oxidation of volcanogenic sulfur gases, was the most abundant sulfur species in the ocean, but its concentration was low by modern standards because of the absence of the river-borne flux of dissolved sulfate produced by oxidative weathering of the continents. These findings are consistent with the geologic record of the isotopic composition of sedimentary sulfates and sulfides. Except in restricted environments, the sulfur metabolism of the earliest organisms probably involved oxidized sulfur species not sulfide.

The composition of snowfall, snowpack and meltwater in the Scottish Highlands ― evidence for preferential elution

Abstract Acidic snows in a small, remote, high-altitude snowpack in the Cairngorms, Scotland, give rise to meltwaters which are proportionally rich in sulphate and nitrate. As a consequence, the within-pack snows become proportionally rich in chloride, even though depleted in solute. Preferential elution appears to be a major process in the chemical evolution of snowfall and snowpack.

The solubility and behaviour of acid gases in the marine aerosol

The following Henrys law constants (KH/mol2kg-2atm-1) for HNO3 and the hydrohalic acids have been evaluated from available partial pressure and other thermodynamic data from 0°–40°C, 1 atm total pressure: HNO3, 40°C–5.85×105; 30°C–1.50×106; 25°C–2.45×106; 20°C–4.04×106; 10°C–1.15×107; 0°C–3.41×107. HF, 40°C–3.2; 30°C–6.6; 25°C–9.61; 20°C–14.0; 10°C–32.0; 0°C–76. HCl, 40°C–4.66×105; 30°C–1.23×106; 25°C–2.04×106; 20°C–3.37×106; 10°C–9.71×106; 0°C–2.95×107. HBr, 40°C–2.5×108; 30°C–7.5×108; 25°C–1.32×109; 20°C–2.37×109; 10°C–8.10×109; 0°C–3.0×1010. HI, 40°C–5.2×108; 30°C–1.5×109; 25°C–2.5×109; 20°C–4.5×109; 10°C–1.5×1010; 0°C–5.0×1010. Simple equilibrium models suggest that HNO3, CH3SO3H and other acids up to 10x less soluble than HCl displace it from marine seasalt aerosols. HF is displaced preferentially to HCl by dissolved acidity at all relative humidities greater than about 80%, and should be entirely depleted in aged marine aerosols.

The catalytic oxidation of micromolar aqueous sulphur dioxide—I: Oxidation in dilute solutions containing iron (III)

The rate of oxidation of SO2 by oxygen in “pure” water was found to vary with pH, having a maximum rate at pH 6 where the half life for the reaction was 300 ± 50 min. It is believed that the variable results for the oxidation in “pure” water were due to contamination by trace (about 5 × 10−8M) Fe(III). It was shown that Fe(III) at 10−6 M concentration is a true catalyst for SO2 solution oxidation and that its role can be explained by a free radical chain reaction. Using the rate data obtained in these experiments a calculation of the possible rate of oxidation of SO2 in fog droplets in the atmosphere is described.

Indoor air quality at the Correr Museum, Venice, Italy

Two multidisciplinary field surveys, one in winter and the other in summer have monitored the indoor microclimate, air pollution, deposition and origin of the suspended particulate matter and microorganisms of the Correr Museum, Venice. In addition, this study was focused to identify the problems caused by the heating and air conditioning system (HAC) and the effects due to the presence of carpets. Heating and air conditioning systems (HACs), when chiefly designed for human welfare, are not suitable for conservation and can cause dangerous temperature and humidity fluctuations. Improvements at the Correr Museum have been achieved with the assistance of environmental monitoring. The carpet has a negative influence as it retains particles and bacteria which are resuspended each time people walk on it. The indoor/outdoor pollutants ratio is greater in the summertime, when doors and windows are more frequently open to allow for better ventilation, illustrating that this ratio is mainly governed by the free exchange of the air masses. The chemical composition, size and origin of the suspended particulate matter have been identified, as well as the bacteria potentially dangerous to the paintings. Some general suggestions for improving indoor air quality are reported in the conclusions.

Mapping the impact of climate change on surface recession of carbonate buildings in Europe

Climate change is currently attracting interest at both research and policy levels. However, it is usually explored in terms of its effect on agriculture, water, industry, energy, transport and health and as yet has been insufficiently addressed as a factor threatening cultural heritage. Among the climate parameters critical to heritage conservation and expected to change in the future, precipitation plays an important role in surface recession of stone. The Lipfert function has been taken under consideration to quantify the annual surface recession of carbonate stone, due to the effects of clean rain, acid rain and dry deposition of pollutants. The present paper provides Europe-wide maps showing quantitative predictions of surface recession on carbonate stones for the 21st century, combining a modified Lipfert function with output from the Hadley global climate model. Chemical dissolution of carbonate stones, via the karst effect, will increase with future CO(2) concentrations, and will come to dominate over sulfur deposition and acid rain effects on monuments and buildings in both urban and rural areas. During the present century the rainfall contribution to surface recession is likely to have a small effect, while the increase in atmospheric CO(2) concentration is shown to be the main factor in increasing weathering via the karst effect.