REVIEWS 1479

Microclimate andspray dispersion. By D. H. Bache and D. R. Johnstone. Ellis Horwood, 1992. Pp. 238. Price f45 (hardback). ISBN 13-217910-5.

The importance of spraying crops with insecticides, fungicides and herbicides must be evident to everyone who travels through the countryside, and is emphasized by estimates that between a quarter and a third of the world’s production of food is lost because of weed, disease and pest invasion. Spraying is also undertaken to control insects which are vectors of human disease. Controversy continues regarding the adverse environmental and health effects of spraying, therefore it is clearly imperative that spraying is controlled to achieve the required effect with a minimum of material and to avoid spray drift.

Against this background, Bache and Johnstone have assembled the physical fundamentals required to understand the fate of material released during crop spraying operations, and to evaluate and develop spraying strategies. They do not venture into the properties of the chemical substances in use that determine their efficacy or persistence, but summarize the meteorological requirements, spray design and application methodology for controlled placement of the active ingredients. The subject matter comprises the meteorology of the boundary layer and the dispersion of material emitted from sprays within the turbulent surface layer, the description of drop size distribution and physical properties of sprays including sedimentation, inertial behaviour and evaporation, and deposition to plant canopies and insects. The application of the collecting information to the planning of spraying operations is discussed, in which respect the estimation and control of drift is emphasized, and information on the influence of evaporation of spray drops and deposited material is included. The chapter on applications is helpfully structured to summarize and cross-reference the previous material and may serve as a reading guide for those with a particular application in mind; this is supplemented in a brief epilogue which indicates where the basic concepts and results are contained in the text.

The achievement of the book is the presentation of mathematical and practical descriptions of the factors relevant to the dispersal of sprays in the near-surface atmosphere and deposition within crop canopies. The compact volume provides brief descriptions of many of the processes, and some features would not be readily apparent to a student coming fresh to the area. For others it will serve as a valuable summary of a substantial range of subject matter. Unfortunately there are also some minor errors and discrepancies in mathematical notation. My final quibble is that one mathematical description of canopy deposition is given, without any mention of those of other workers which provide additional insights or differing results that would be of benefit to many readers. Despite these caveats, I believe that this volume will provide a valuable introduction and structured approach to an important subject area.

The text will clearly be of value to engineers and researchers in the agricultural and agrochemical industries and related sciences, In addition, it should be a useful source of reference to those concerned with contamination of crops by air pollution, in so far as the topics of dispersion and deposition are directly relevant.

JOHN GARLAND

Aerosol effects on climate. Edited by S . G. Jennings. University of Arizona Press, 1993. Pp. 304. ISBN 0-8165- 1362-7. Price $40. Interest in the potential impact of aerosols on climate has waxed and waned over the past two or three decades and, in recent years, has reached new heights. One current hypothesis is that sulphate aerosols resulting from human activity may be acting to cool the climate, substantially offsetting the warming due to the enhanced greenhouse effect. Two mechanisms may be involved. One, the so-called direct effect, is simply due to the enhanced scatter by the aerosols increasing the planetary albedo. The second, the indirect effect, operates via an increase in cloud condensation nuclei decreasing mean cloud droplet sizes, which enhances the cloud albedo for a given liquid water path.

This book, published in 1993, promised to be an up-to-date assessment of the effect of both tropospheric and stratospheric (mainly volcanic) aerosols. A further welcome feature was that many of the chapters were written by Soviet authors, allowing an easily accessible entry into the vast Soviet literature.

My use of ‘Soviet’ in the previous paragraph was deliberate. Alas! It transpires that the vast majority of this book must have been written in the early 1980s. for references to any literature after this are rare and, where they occur, rather superficial. It seems that the project has taken around a decade to bring to fruition. The editor’s introduction alludes to the fact that the ‘international nature . . . delayed publication of the book’ but he does not let on quite how long it was delayed. Much has happened in the aerosol world since then. El Chichon had clearly only just erupted, Pinatubo was almost a decade away; the invaluable SAGE I1 satellite instrument had yet to be launched and the Gulf War, with its ghastly plume, was yet to occur. Attention on sulphate and biomass emissions was in its infancy.

The editor was brave to proceed with such an exercise given the delays and, one suspects, some increasingly irate contributors. In a six-page introduction he attempts to bring the subject into the 1990s, but this is not long enough to do justice to the developments.

Is a decade-old overview of the subject worthwhile? I would give a qualified ‘yes’. It forced me to think again about some of the current paradigms, and I was surprised how well developed some of the ‘new’ areas were at that time. The areas that suffered most from the delay are concerned with stratospheric aerosols.