- Email: [email protected]
Computer-assisted structure elucidation
at the time of writing. In addition Clerjaud provides an addendum which brings his article up to date, a procedure which the other authors could usefully have followed. However, there is still a great deal of valuable material in this collection. Overall, I am not convinced that this book performs a useful service. Professionals will already have copies of most of these articles in their possession and yet without some introductory chapters there is not the teaching element necessary for it to be of use to graduate students. .I. c Inkson The Ghost in the Atom. Edited by P. C. W. Davies and J. R. Brown. Pp. 157. Cambridge University Press. 7986. Hard Cover f 17.50, Paperback f6.50. TheForcesofNature.2ndEd.ByP.C. W. Davies. Pp. 775. Cambridge University Press. 1986. Hardbackf22.50, Paperback
f7.95. When introduced to the basic ideas of quantum mechanics most people are intrigued and confused by concepts such as wave-particle duality and Heisenberg’s uncertainty principle. Later they may learn that the detailed rules can be used to predict the outcome of incredibly precise experiments and so they might think that, at least for the experts, the confusion has been resolved. The Ghost in the Atom consists largely of transcribed interviews with several scientists who hold fundamentally different views on the interpretation of quantum mechanics. The book starts with a clear presentation of the conceptual difficulties, particularly those posed by wave-particle duality and by the effects produced by measurement. In the interviews it becomes clear that there is no accepted establishment position, particularly as to the significance of the conscious observer. This leaves the door open for more radical suggestions such as the existence of an infinite set of parallel universes or the need for hidden variables. I found it a stimulating book; the transcribed discussions are easy to read and work well. Not surprisingly, the book draws no conclusions. The past few years have seen major advances in the theory of particle physics and new experimental discoveries such as the Z and W bosons. There has also been great interest in the connections between particle physics and cosmology. The second edition of The Forces of Nuture covers all these recent developments. It is written for non-specialists; starting from basic ideas it provides a clear, readable, nonmathematical account of the historical. developments leading to the current state of particle physics. It does not include much experimental detail but there are a few photographs which show the scale of today’s accelerators and experiments. It should interest most physics students as well as the general reader looking for an accurate up-to-date picture. T. McMahon
introduction to Physical Chemistry. By M. F. C. Ladd and W. H. Lee. Pp. 347. Cambridge University Press, 1986. Hard cover f27.50 ($49.50), Paperback 19.95 ($19.95).
tithe of the subject, even if this causes the incongruous split of chapters on catalysis between A. Brenner and B. C. Gates.
The seven chapters of this book present the principal topics of physical chemistry which would be discussed in almost any first year degree course in chemistry: atoms, molecules, and bonding; thermochemistry and thermodynamics; states of matter; chemical equilibrium; physical properties of systems; electrochemistry; kinetics of chemical reactions. The omission of a number of subjects which one would expect to find in a comprehensive text-book, indicates that it is expected that the reader will proceed to widen his studies, with further books in later years, The basis of physical chemistry, dealing with the structure of matter and the kinetics and energetics of chemical processes, is presented here with admirable clarity and precision. The book is therefore useful also as a work of reference to supplement more advanced or specialised works. S.I. units are employed but where others are commonly used, such as the electron-volt, they are not avoided, and the authors have given guidance on the interconversion of units and the value of dimensional analysis in verifying mathematical equations for chemical processes. The book contains many references to authoritative sources; problems are given at the end of each chapter, and there is a subject index. It can be strongly recommended to first-year students, who will find in it the answer to many of the questions which they might otherwise have to put to their tutors.
Ultratrace Analysis of Pharmaceuticals and other Compounds of Interest. Edited by Satinder Ahuja. Pp. 384. Wiley, Chichester. 1986. f57.50.
Aitken Couper
Metal Clusters. Edited by Martin Moskovits. Pp. 213. Wiley, Chichester. 1986. f47.95.
The study of small molecular conglomerates containing metal-to-metal bonds dates from the 1950sbut only in the last 10 years has it become a ‘recognised discipline’ as Martin, Moskovits calls it in his introduction. Metal clusters certainly are fascinating entities with structures reminiscent of those in the geometrical works of M. C. Escher but without the mythical beasts. They do have magic numbers of atoms. For example, why clusters of sodium atoms containing 2, 8,20, 40, 58, or 92 atoms are particularly stable may be explained by the curious ‘jellium’ model. The book is for researchers in the field or in related disciplines, not for those who do not know what a metal cluster is. The only definition I found appeared in the final chapter in which B. C. Gates discusses supported metal clusters as catalysts. Each chapter, by a different author, is well written, with a comprehensive bibliography, although the index to the book as a whole could be longer. The editor has chosen well to ask active scientists to cover their own
D. B. Hibbert
This professional book is well presented, with few errors and is fully referenced. Chapter 1 defines ultratrace analysis and shows there is a need for detection and estimation at the picrogram level. There is an interesting section on sampling error, and also data on the limits of detection. (Table 1.2) Although abreviations are defined, it would be convenient to have them listed on one page, as much use is made of these throughout the text. Chapter 2, dealing with derivatization, although excellent, should also mention the manipulative limits for amount of sample as distinct from the column detection limit. Tabulated data of derivatives (Tables 2.12/ 2.13) could with advantage be expanded to show names and conditions of each reaction. The third chapter adopts a historical viewpoint to trace the symbiotic joining together of GLC, MS, and Computer up to the present state of the art machines, The recent shift towards capillary and open tubular columns is made clear. Thought provoking examples, such as the use of possible mutagenic chemicals as clothing fire retardants, detected in children’s urine, are given. Chapter 4 on HPLC with and without MS evaluates both practically (Fig. 4.2) and mathematically the components of a given system. Touchstone in Chapter 5 reviews the continuing contribution made by TLC and its modern variant HPTLC. Chapter 6 examines selected instrumental aspects of atomic spectrometric analysis. Chapter 7 deals with impurity levels in 14 groups of pharmaceuticals, and shows the value of analysis in the detection of illicit drugs. Chapters 8, 9, 10, and 11 evaluate impurity levels in excipients, drugs, animal feeds, and animal products, while Chapter 12 deals with forensic work. Overall a stimulating and worthwhile book. R. J. Washington Computer-Assisted Structure Elucidation. By Neil’A. B. Gray. Pp. 536. Wiley, Chichester. 1986. f52.70.
Every major pharmaceutical company now employs specialists in the area of computer graphics and molecular modelling: many also use programs to plan synthetic routes. Students need to know about this area and yet there is a notable shortage of texts which go into the basics. Gray’s book on Computer-Assisted
Structure
Elucidation
satisfies a part of the requirement. There is a full and very helpful account of 107
graph theory, three main themes being covered: computer-assisted recognition and interpretation of spectral data; representation and manipulation of structural information; and the prediction of spectral properties and the analysis of chemical transformations. The introduction to artitical intelligence methods will be particularly welcomed by the many who are starting to grapple with these concepts. What the book does not contain is anything about theoretical calculations on molecules, distance geometry calculations, or the current state of molecular graphics. Nonetheless, a 500-page work with an excellent and full bibliography can hardly be criticised for its omissions. In the area in which it specializes this is an original and seminal work. W. G. Richards
Introduction to Industrial Chemistry. Howard L. White. Pp. 247. Wiley, Chichester, 7986. f38.50.
By
The author says in his Preface that undergraduate education in chemistry is mainly theoretical, and lacks the details of industrial processes. To remedy this, he urges that his book should be used in a one-semester course in Industrial Chemistry. His statement about undergraduate courses is certainly true, but there are differing opinions among chemists as to whether remedial action along the lines he advocates should be made. If it should, then the first four chapters of this book could be useful. These chapters describe the industrial production of some inorganic and organic chemicals (26 and 58 pages respectively), the fermentation approach to chemical manufacture, and waste treatment (22 pages). This accounts for less than half the book. The remaining eight chapters (116 pages) are individually sketchy, and, taken as a whole, lack coherence. They cover aspects of equipment, costs, scale-up, pollution, catalysts, pesticides, herbicides, soaps and detergents (2% pages), pharmaceuticals (2% pages), and careers. Finally, there is a chapter (9 pages) on the elementary physical chemistry of distillation, and solvent extraction, and it is only here that we encounter some simple calculations. Therefore one impression created by this book is that industrial chemistry proceeds without serious chemical calculations; this is certainly not the case. T. B. Grimley
Spectroscopy of Biological Systems. Edited by R. J. H. Clark and R. E. Hester. Pp. 547. Wiley, Chichester. 1986. f83.00.
This book appears as Volume 13 of Advances in Spectroscopy, a series devoted to critical review articles in fundamental and applied aspects of a wide range of spectroscopic techniques. This is the first volume devoted wholly to biological systems, though other volumes have contained occasional excursions into biological topics. It
108
deals almost exclusively with various forms of infrared and Raman methods and concentrates on their applications to the more important biological systems which are troublesome partly because of the predominant presence of water with its obscuring absorption bands but also because of the complexity arising from the presence of so many overlapping bands. Ten chapters are included by authors chosen worldwide. Chapter 1 is devoted to resolution enhancement upon which much of the later experimental work depends and the serious learner will probably start here. Chapter 7 deals with normal coordinate analysis for macromolecules, of undoubted importance for a deeper understanding of spectra. The remaining chapters deal with important members of the proteins, with nucleic acids, and with their interactions with one another and other substances. The standard of the writing is high and its role as a reference work on library shelves seems assured. Its price effectively removes its uses as a personal text. Paley Johnson
Mass Spectrometry. Applications in Science and Engineering. By Frederick White and George M. Wood. Pp. 773. Wiley, Chichester. 7986. f69.45.
A.
The authors have set themselves two principal objectives in producing this book: first to present an overview of modern mass spectrometry in its many manifestations and second to stimulate further innovative mass spectrometric measurements. No reader of this fascinating book could fail to be impressed by the range and sophistication of the mass spectrometers developed to date and the enormous range of applications to which mass spectrometry is being successfully applied. The first 236 pages present an extensive introductory survey of the mass analysers, detectors, and ion sources which have been developed since the early experiments of Thomson and Aston. The most modern advances in MS/MS, SIMS, FABMS, LC and GC-MS, RBS etc are described. Just enough theory and technical detail is presented to give the reader a clear conceptual understanding of how mass spectrometry is performed. A good though not exhaustive bibliograhy will enable interested readers to extend their knowledge. Parts 2 and 3 present representative accounts of an astonishing range of applications in Engineering, the Physical Sciences, Environmental Monitoring, and the Life Sciences. The mass spectrometry specialist will have his horizon broadened and the non-specialist student or scientist will gain an exciting insight into the tremendous power of the technique. The authors succeed admirably in their first objective and deserve to succeed in their second. J. C. Vickerman
Air Composition and Chemistry. By Peter Brimblecombe. Pp. 224. Cambridge University Press. 1986. Hardback f25.00, Paperback f8.95.
To those interested in the air we breathe and environmental matters concerning the pollution of our atmosphere, Dr Brimblecombe’s book is a welcome addition and worthwhile purchase. After a basic physical consideration of the atmosphere, it discusses the geochemical, biological, and maritime sources of trace gases. Attention is then devoted to atmospheric chemistry - reaction rates and photochemistry in the gas phase with a gentle introduction to the importance of the hydroxyl radicals and other reactive species. The elucidation of the complexities of aerosols and cloud water chemistry that follows is particularly valuable because these topics are rarely explained with such clarity elsewhere - which partially accounts for many of the misconceptions concerning acid rain. The book then returns to the theme of sources specifically in terms of man-made pollution with separate considerations of combustion chemistry, emission control systems, and dispersion mechanisms. The weakest section deals with the effects of air pollution. Nevertheless, this properly conveys a synoptic overview of the scale of the various problems induced in the biosphere and upon the materials used by man. The theme of atmospheric chemistry is concluded by considerations of reactions in the upper atmosphere and, most interestingly, on other planets. Alan Wellburn Atmospheric Chemistry. Fundamentals and Experimental Techniques. By Barbara J. Finlayson-Pitts and James N. Pitts, Jr. Pp. 1098. Wiley, Chichester. 1986. f57.45.
Last year saw the publication of at least four new texts in atmospheric chemistry. In many fields this would pass unnoticed, but in an area of science of such importance, so devoid until now of adequate treatments, 1986 will long be remembered. The books by Wayne (Oxford University Press) and Brimblecombe (Cambridge University Press) provide excellent coverage of the subject at undergraduate level. That by Seinfeld (Wiley-Interscience) provides a comprehensive and detailed treatment of the chemistry, physics, and mathematics of air pollution at an advanced level and is an invaluable reference book. However, it is the book under review here which must be regarded as describing the state-of-the-art in atmospheric chemistry. Concentrating on the troposphere, this massive volume describes the chemistry of both the unperturbed and the polluted atmosphere, emphasising the importance of from first principles photochemistry, through to experimental measurement and modelling techniques currently in use. So much other material is covered, including the theory and applications of spectroscopy and kinetics, acid deposition, organic pollu-
f7.95. When introduced to the basic ideas of quantum mechanics most people are intrigued and confused by concepts such as wave-particle duality and Heisenberg’s uncertainty principle. Later they may learn that the detailed rules can be used to predict the outcome of incredibly precise experiments and so they might think that, at least for the experts, the confusion has been resolved. The Ghost in the Atom consists largely of transcribed interviews with several scientists who hold fundamentally different views on the interpretation of quantum mechanics. The book starts with a clear presentation of the conceptual difficulties, particularly those posed by wave-particle duality and by the effects produced by measurement. In the interviews it becomes clear that there is no accepted establishment position, particularly as to the significance of the conscious observer. This leaves the door open for more radical suggestions such as the existence of an infinite set of parallel universes or the need for hidden variables. I found it a stimulating book; the transcribed discussions are easy to read and work well. Not surprisingly, the book draws no conclusions. The past few years have seen major advances in the theory of particle physics and new experimental discoveries such as the Z and W bosons. There has also been great interest in the connections between particle physics and cosmology. The second edition of The Forces of Nuture covers all these recent developments. It is written for non-specialists; starting from basic ideas it provides a clear, readable, nonmathematical account of the historical. developments leading to the current state of particle physics. It does not include much experimental detail but there are a few photographs which show the scale of today’s accelerators and experiments. It should interest most physics students as well as the general reader looking for an accurate up-to-date picture. T. McMahon
introduction to Physical Chemistry. By M. F. C. Ladd and W. H. Lee. Pp. 347. Cambridge University Press, 1986. Hard cover f27.50 ($49.50), Paperback 19.95 ($19.95).
tithe of the subject, even if this causes the incongruous split of chapters on catalysis between A. Brenner and B. C. Gates.
The seven chapters of this book present the principal topics of physical chemistry which would be discussed in almost any first year degree course in chemistry: atoms, molecules, and bonding; thermochemistry and thermodynamics; states of matter; chemical equilibrium; physical properties of systems; electrochemistry; kinetics of chemical reactions. The omission of a number of subjects which one would expect to find in a comprehensive text-book, indicates that it is expected that the reader will proceed to widen his studies, with further books in later years, The basis of physical chemistry, dealing with the structure of matter and the kinetics and energetics of chemical processes, is presented here with admirable clarity and precision. The book is therefore useful also as a work of reference to supplement more advanced or specialised works. S.I. units are employed but where others are commonly used, such as the electron-volt, they are not avoided, and the authors have given guidance on the interconversion of units and the value of dimensional analysis in verifying mathematical equations for chemical processes. The book contains many references to authoritative sources; problems are given at the end of each chapter, and there is a subject index. It can be strongly recommended to first-year students, who will find in it the answer to many of the questions which they might otherwise have to put to their tutors.
Ultratrace Analysis of Pharmaceuticals and other Compounds of Interest. Edited by Satinder Ahuja. Pp. 384. Wiley, Chichester. 1986. f57.50.
Aitken Couper
Metal Clusters. Edited by Martin Moskovits. Pp. 213. Wiley, Chichester. 1986. f47.95.
The study of small molecular conglomerates containing metal-to-metal bonds dates from the 1950sbut only in the last 10 years has it become a ‘recognised discipline’ as Martin, Moskovits calls it in his introduction. Metal clusters certainly are fascinating entities with structures reminiscent of those in the geometrical works of M. C. Escher but without the mythical beasts. They do have magic numbers of atoms. For example, why clusters of sodium atoms containing 2, 8,20, 40, 58, or 92 atoms are particularly stable may be explained by the curious ‘jellium’ model. The book is for researchers in the field or in related disciplines, not for those who do not know what a metal cluster is. The only definition I found appeared in the final chapter in which B. C. Gates discusses supported metal clusters as catalysts. Each chapter, by a different author, is well written, with a comprehensive bibliography, although the index to the book as a whole could be longer. The editor has chosen well to ask active scientists to cover their own
D. B. Hibbert
This professional book is well presented, with few errors and is fully referenced. Chapter 1 defines ultratrace analysis and shows there is a need for detection and estimation at the picrogram level. There is an interesting section on sampling error, and also data on the limits of detection. (Table 1.2) Although abreviations are defined, it would be convenient to have them listed on one page, as much use is made of these throughout the text. Chapter 2, dealing with derivatization, although excellent, should also mention the manipulative limits for amount of sample as distinct from the column detection limit. Tabulated data of derivatives (Tables 2.12/ 2.13) could with advantage be expanded to show names and conditions of each reaction. The third chapter adopts a historical viewpoint to trace the symbiotic joining together of GLC, MS, and Computer up to the present state of the art machines, The recent shift towards capillary and open tubular columns is made clear. Thought provoking examples, such as the use of possible mutagenic chemicals as clothing fire retardants, detected in children’s urine, are given. Chapter 4 on HPLC with and without MS evaluates both practically (Fig. 4.2) and mathematically the components of a given system. Touchstone in Chapter 5 reviews the continuing contribution made by TLC and its modern variant HPTLC. Chapter 6 examines selected instrumental aspects of atomic spectrometric analysis. Chapter 7 deals with impurity levels in 14 groups of pharmaceuticals, and shows the value of analysis in the detection of illicit drugs. Chapters 8, 9, 10, and 11 evaluate impurity levels in excipients, drugs, animal feeds, and animal products, while Chapter 12 deals with forensic work. Overall a stimulating and worthwhile book. R. J. Washington Computer-Assisted Structure Elucidation. By Neil’A. B. Gray. Pp. 536. Wiley, Chichester. 1986. f52.70.
Every major pharmaceutical company now employs specialists in the area of computer graphics and molecular modelling: many also use programs to plan synthetic routes. Students need to know about this area and yet there is a notable shortage of texts which go into the basics. Gray’s book on Computer-Assisted
Structure
Elucidation
satisfies a part of the requirement. There is a full and very helpful account of 107
graph theory, three main themes being covered: computer-assisted recognition and interpretation of spectral data; representation and manipulation of structural information; and the prediction of spectral properties and the analysis of chemical transformations. The introduction to artitical intelligence methods will be particularly welcomed by the many who are starting to grapple with these concepts. What the book does not contain is anything about theoretical calculations on molecules, distance geometry calculations, or the current state of molecular graphics. Nonetheless, a 500-page work with an excellent and full bibliography can hardly be criticised for its omissions. In the area in which it specializes this is an original and seminal work. W. G. Richards
Introduction to Industrial Chemistry. Howard L. White. Pp. 247. Wiley, Chichester, 7986. f38.50.
By
The author says in his Preface that undergraduate education in chemistry is mainly theoretical, and lacks the details of industrial processes. To remedy this, he urges that his book should be used in a one-semester course in Industrial Chemistry. His statement about undergraduate courses is certainly true, but there are differing opinions among chemists as to whether remedial action along the lines he advocates should be made. If it should, then the first four chapters of this book could be useful. These chapters describe the industrial production of some inorganic and organic chemicals (26 and 58 pages respectively), the fermentation approach to chemical manufacture, and waste treatment (22 pages). This accounts for less than half the book. The remaining eight chapters (116 pages) are individually sketchy, and, taken as a whole, lack coherence. They cover aspects of equipment, costs, scale-up, pollution, catalysts, pesticides, herbicides, soaps and detergents (2% pages), pharmaceuticals (2% pages), and careers. Finally, there is a chapter (9 pages) on the elementary physical chemistry of distillation, and solvent extraction, and it is only here that we encounter some simple calculations. Therefore one impression created by this book is that industrial chemistry proceeds without serious chemical calculations; this is certainly not the case. T. B. Grimley
Spectroscopy of Biological Systems. Edited by R. J. H. Clark and R. E. Hester. Pp. 547. Wiley, Chichester. 1986. f83.00.
This book appears as Volume 13 of Advances in Spectroscopy, a series devoted to critical review articles in fundamental and applied aspects of a wide range of spectroscopic techniques. This is the first volume devoted wholly to biological systems, though other volumes have contained occasional excursions into biological topics. It
108
deals almost exclusively with various forms of infrared and Raman methods and concentrates on their applications to the more important biological systems which are troublesome partly because of the predominant presence of water with its obscuring absorption bands but also because of the complexity arising from the presence of so many overlapping bands. Ten chapters are included by authors chosen worldwide. Chapter 1 is devoted to resolution enhancement upon which much of the later experimental work depends and the serious learner will probably start here. Chapter 7 deals with normal coordinate analysis for macromolecules, of undoubted importance for a deeper understanding of spectra. The remaining chapters deal with important members of the proteins, with nucleic acids, and with their interactions with one another and other substances. The standard of the writing is high and its role as a reference work on library shelves seems assured. Its price effectively removes its uses as a personal text. Paley Johnson
Mass Spectrometry. Applications in Science and Engineering. By Frederick White and George M. Wood. Pp. 773. Wiley, Chichester. 7986. f69.45.
A.
The authors have set themselves two principal objectives in producing this book: first to present an overview of modern mass spectrometry in its many manifestations and second to stimulate further innovative mass spectrometric measurements. No reader of this fascinating book could fail to be impressed by the range and sophistication of the mass spectrometers developed to date and the enormous range of applications to which mass spectrometry is being successfully applied. The first 236 pages present an extensive introductory survey of the mass analysers, detectors, and ion sources which have been developed since the early experiments of Thomson and Aston. The most modern advances in MS/MS, SIMS, FABMS, LC and GC-MS, RBS etc are described. Just enough theory and technical detail is presented to give the reader a clear conceptual understanding of how mass spectrometry is performed. A good though not exhaustive bibliograhy will enable interested readers to extend their knowledge. Parts 2 and 3 present representative accounts of an astonishing range of applications in Engineering, the Physical Sciences, Environmental Monitoring, and the Life Sciences. The mass spectrometry specialist will have his horizon broadened and the non-specialist student or scientist will gain an exciting insight into the tremendous power of the technique. The authors succeed admirably in their first objective and deserve to succeed in their second. J. C. Vickerman
Air Composition and Chemistry. By Peter Brimblecombe. Pp. 224. Cambridge University Press. 1986. Hardback f25.00, Paperback f8.95.
To those interested in the air we breathe and environmental matters concerning the pollution of our atmosphere, Dr Brimblecombe’s book is a welcome addition and worthwhile purchase. After a basic physical consideration of the atmosphere, it discusses the geochemical, biological, and maritime sources of trace gases. Attention is then devoted to atmospheric chemistry - reaction rates and photochemistry in the gas phase with a gentle introduction to the importance of the hydroxyl radicals and other reactive species. The elucidation of the complexities of aerosols and cloud water chemistry that follows is particularly valuable because these topics are rarely explained with such clarity elsewhere - which partially accounts for many of the misconceptions concerning acid rain. The book then returns to the theme of sources specifically in terms of man-made pollution with separate considerations of combustion chemistry, emission control systems, and dispersion mechanisms. The weakest section deals with the effects of air pollution. Nevertheless, this properly conveys a synoptic overview of the scale of the various problems induced in the biosphere and upon the materials used by man. The theme of atmospheric chemistry is concluded by considerations of reactions in the upper atmosphere and, most interestingly, on other planets. Alan Wellburn Atmospheric Chemistry. Fundamentals and Experimental Techniques. By Barbara J. Finlayson-Pitts and James N. Pitts, Jr. Pp. 1098. Wiley, Chichester. 1986. f57.45.
Last year saw the publication of at least four new texts in atmospheric chemistry. In many fields this would pass unnoticed, but in an area of science of such importance, so devoid until now of adequate treatments, 1986 will long be remembered. The books by Wayne (Oxford University Press) and Brimblecombe (Cambridge University Press) provide excellent coverage of the subject at undergraduate level. That by Seinfeld (Wiley-Interscience) provides a comprehensive and detailed treatment of the chemistry, physics, and mathematics of air pollution at an advanced level and is an invaluable reference book. However, it is the book under review here which must be regarded as describing the state-of-the-art in atmospheric chemistry. Concentrating on the troposphere, this massive volume describes the chemistry of both the unperturbed and the polluted atmosphere, emphasising the importance of from first principles photochemistry, through to experimental measurement and modelling techniques currently in use. So much other material is covered, including the theory and applications of spectroscopy and kinetics, acid deposition, organic pollu-