I. Colbeck

A solar pond for London

Formulas which were used to make predictions for several locations in the U.S. were applied to the conditions in southern England, near London. The calculations indicate that a house near London would need a pond area equal to its floor space. (MHR)

The Jungfraujoch high-alpine research station (3454 m) as a background clean continental site for the measurement of aerosol parameters

The first annual data set of climatically important aerosol parameters, measured at the Jungfraujoch (JFJ) high-alpine research station (3454 m, Switzerland) from an ongoing field campaign since July 1995, is presented. Analysis of diurnal variations in continuous measurements of the total and backward hemispheric scattering coefficients (σSP, σBSP), the absorption coefficient (σAP, from aethalometer data), condensation nuclei (CN) concentration, and epiphaniometer signal (related to surface area (S) concentration) established the diurnal period 0300 – 0900 as being representative of the free tropospheric background aerosol. The annual data set was then edited to omit (1) the period 0900–0300 (i.e., 18 hours), taken to represent possible planetary boundary layer influenced conditions and (2) in-cloud conditions using a cloud liquid-water monitor. The seasonal aerosol cycle exhibited a July maximum and a December minimum in most aerosol parameters. Typical monthly median values for the free troposphere exhibit the following seasonal maxima and minima, respectively: σSP (550 nm) ∼ 16.1 and 0.43 × 10−6 m−1, σBSP (550 nm) ∼ 2.10 and 0.09 × 10−6 m−1, σAP (550 nm) ∼ 10.4 and 0.76 × 10−7 m−1 (≈ 104 and 7.6 ng m−3 black carbon), CN concentration ∼ 670 and 280 cm−3, and epiphaniometer signal ∼ 9.26 and 0.67 counts s−1 (S concentration ≈24.1 and 1.7 μm2 cm−3). Aerosol parameters were found to be comparable in magnitude to other NOAA baseline and regional stations and suggest that a clean continental designation for the JFJ site is applicable, when removing the planetary boundary layer influenced period.

The morphology and optical properties of soot produced by different fuels

Abstract Measurements have been made of the morphology and optical properties of soot produced by the combustion, in the laboratory, of petrol, diesel, fuel oil, paraffin, butane and wood in still air. The specific extinction coefficients of all the hydrocarbons fall in the range 9.1–11.6 m2 g−1, whilst that for wood was found to be 7.8 m2 g−1. The results indicate that the soots, except that from wood, are fractal-like. Electro-optical scattering was used to study the non-sphericity of the various smokes. These measurements agree with textural and density fractal analysis. Electro-optical scattering and fractal analysis are both excellent indicators of particle morphology.

Dry deposition of ozone: some measurements ofdeposition velocity and of vertical profiles to 100 metres

Abstract Deposition velocities for O3 to grassland have been measured by the gradient method. Values range from 0.08 to 0.91 cms−1 and are shown to be influenced most substantially by changes in surface conditions. O3 deposition is inhibited by the presence of snow or moisture at the surface and tends to decrease as the afternoon progresses. Vertical profiles of O3 and temperature to 100 m height are indicative of surface depletion of O3 by dry deposition and a diminution of concentration at ground-level due to inhibition of vertical mixing from aloft during periods of atmospheric stability. Dry deposition fluxes are shown to be adequate to account for the diurnal variation of O3 observed at ground-level in rural areas during summer anticyclonic conditions.

Environmental Chemistry of Aerosols

1. Physical and Chemical Properties of Atmospheric Aerosols. 2. Nucleation. 3. Mass Transfer to Aerosols. 4. Organic Aerosols. 5. Metals in Aerosols. 6. Thermodynamics of aqueous systems. 7. Stratospheric Chemistry: aerosols and the ozone layer. 8. Aerosol Chemistry in Remote Locations.

Atmospheric aerosol and gaseous species in Athens, Greece

Abstract Measurements of aerosol species including Cl - , NO - 3 , SO 2- 4 , NH + 4 , Na + , K + , Mg 2+ and Ca 2+ and gaseous pollutants like HCl, HNO 3 , NO 2 , SO 2 and O 3 were conducted at the centre of Athens. Results show moderate levels of pollution with aerosol species typical of dust emissions and secondary aerosol of anthropogenic origin. Most gaseous pollutants correlate well with aerosol species. There is a pronounced elevation in the concentration of acidic trace gases HCl and HNO 3 arriving at the city from the direction of the Saronikos gulf, indicating poor neutralisation of such species over the sea. On the contrary, air masses coming from inland are characterised by considerably higher ammonium aerosol. It was concluded that in addition to heavier aerosol load pollution episodes in Athens during the summer period are associated with higher concentrations of gaseous acids.

The optical properties and morphology of cloud-processed carbonaceous smoke

The effects of high relative humidity and low supersaturations of water vapour on the morphology of fractal clusters of carbonaceous smoke are examined. Under supersaturation conditions, characteristic of those found in the atmosphere, smoke still consists of fractal clusters, although the fractal dimension has been substantially increased. The result of cloud processing (repeated compression/expansion cycles) upon the optical properties of the clusters indicates little change for small clusters (N 103 primary spherules). This is qualitatively consistent with the predictions of theory if the particles change from clusters of fractal dimension D < 2 to compact spheres as a result of such processing.

Characteristics of indoor/outdoor particulate pollution in urban and rural residential environment of Pakistan

UNLABELLED Particulate pollution has emerged as a serious environmental health concern in Pakistan. The use of biomass fuels in traditional stoves produces high levels of indoor air pollutants. In Pakistan, 94% of rural and 58% of urban households depend on biomass fuel. This study investigates variations in indoor/outdoor concentrations of particulate matter during various activities for three different micro-environments in Pakistan. At a rural site, the average indoor/outdoor ratios for PM(10), PM(2.5), and PM(1), in kitchens using biomass fuels were 3.80, 4.36, and 4.11, respectively. A large variation was recorded in the mass concentration of particulate matter during cooking with concentrations in the range 4000-8555 microg/m(3). In a living room at a rural site, the average indoor/outdoor ratios for PM(10), PM(2.5), and PM(1) were 1.74, 2.49, and 3.01, respectively. At the urban site, the average indoor/outdoor ratios for the same size fractions were 1.71, 2.88, and 3.47, respectively. Cooking, cleaning and smoking were identified as principal contributors to the high indoor levels of particulate matter. This study showed considerably high concentrations of particulate matter, particularly in kitchens using biomass fuels, as compared to living areas. Thus women and children face the greatest exposure due to the amount of time they spend in the kitchen. PRACTICAL IMPLICATIONS In the developing world, particulate air pollution, both indoor and outdoor, is a substantial health hazard to the public. The very high concentrations of particulate matter in both rural and urban sites, particularly in kitchens using biomass fuels, emphasize the severity of this issue in Pakistan. Women and children are extensively at risk due to amount of time spent in kitchens. This state of affairs calls for a large-scale intervention to reduce the exposure to indoor air pollution.

Optical and dynamical properties of fractal clusters of carbonaceous smoke

Abstract Fractal clusters of > 95% elemental carbon have been produced from the combustion of liquefied petroleum gas. The effect of ageing the smoke for various periods resulted in the individual primary smoke particles forming into branched chains, which were up to 30 μm in length after 16 h. These aggregates are fractal clusters with a fractal dimension of ∼ 1.8. Variations in the optical properties of this smoke resulting from changes in cluster size and morphology with ageing time were examined. The specific extinction coefficient and single scatter albedo were found to be almost constant for ageing times up to 16 h. The variation of the specific absorption and scattering coefficients with cluster size was compared with the prediction of the Mie theory and the recent theory of Berry and Percival [Berry, M. V. and Percival, I. C. (1986) Optica Acta 33, 577–591.] relating to fractal clusters. The latter theory gives a better overall description of the optical properties. The coagulation coefficient was determined by measuring the rate of change of particle number density at an ageing time of 2 h. At longer ageing times the loss rate by sedimentation is the dominant mechanism affecting the rate of change of particle number density and values for the dynamic shape factors were calculated. The measurements indicate that the coagulation coefficient remains constant, with a value of ∼ 8 × 10 −10 cm 3 s −1 . The aerodynamic diameter is much less than the volume equivalent diameter of the clusters, indicating that the fractal clusters sediment more slowly than compact spheres of the same mass.

The background aerosol size distribution in the free troposphere: An analysis of the annual cycle at a high‐alpine site

Measurements during free tropospheric (FT) and planetary boundary layer (PBL) conditions were conducted over an annual cycle at the Jungfraujoch high-Alpine research station (3454 m), Switzerland, in order to establish diurnal and seasonal cycles of the background continental aerosol over central Europe. Using a condensation nucleus counter (TSI 3025) and an optical particle counter (PMS Las-X) from June 1996 to May 1997, the following were determined: (1) accumulation mode lognormal parameters and (2) number concentrations for the nucleation (diameter d < 0.1 μm), accumulation (0.1 ≤ d ≤ 1.0 μm), and part of the coarse (1.0 < d ≤ 7.5 μm, designated “coarse”) modes. Lognormal parameters were found to be similar for FT and PBL conditions, and exhibited a weak seasonality in geometric median diameter dGN =0.13 and 0.10 μm, and standard deviation σG = 1.73 and 1.64 for summer and winter, respectively. Aerosol number concentrations in each mode exhibited a more pronounced seasonality, with FT concentrations being lower than those for PBL. Summer and winter FT median concentrations for the nucleation, accumulation, and “coarse” modes were 405 and 195 cm−3, 114 and 26 cm−3, and 0.052 and 0.014 cm−3, respectively. These results provide tentative support of other long-term observations that the FT background aerosol mode appears to vary mainly in concentration rather than accumulation mode shape. Further analysis indicated that only the total concentration in each mode varied with weather type and a classification between that of a remote continental and polar aerosol model was found for the Jungfraujoch.