2Vlanuals of mineral dressing or more precisely those of comminution-classifi cation treat in particular the mechanics of the machines, and generally their handling. In this way the plant engineer becomes acquainted with the equip ment but is given no help in learning something of the processes taking place in the material to be comminuted even though the purpose of the operation is to enhance wanted and to avoid unwanted physical or physico-chemical processes. Neglecting the description or representation of generally used and well known equipment the object of this monograph is to supply information on the processes taking place in grinding installations. It explains the sometimes complicated phemonena by applying quite simple means; it requires only an elementary knowledge of mathematics, mechanics and physical chemistry. The ideas are applicable to the grinding of all brittle raw materials or semi finished industrial products. The special problems of cement grinding and thm;e of hall mills are explained in more detail; in cement grinding we have to meet special requirements with regard to ball mills apart from other con siderations -, since these now demand the greatest overall energy consumption. Currently disputed problems are dealt with, and naturally the views of the author are given in detail, but contrary views are also mentioned and the ample list of references ensures that these opposing views can be considered.

Our motivation for calling a conference on climatic change was to stimulate interdisciplinary exchange between researchers in various fields concerned with climatic research, which include meteorology, oceanography, limnology, palynology, glaciology, dendrochronology, and climate modeling. The philosophy behind this attempt at cross- fertilization is much the same as that of previous conferences on cli- matic change in the NATO-series ("Climatic variations and variability, facts and theories", Berger, 1981; "Milankovitch and climate", Berger et al., 1984). The past is the key to the range of future possibilities. It is for this reason that we stressed history and case studies in convening the present symposium on abrupt climatic change, without however forget- ting that modeling, conceptual and mathematical, ultimately provides the understanding necessary for prediction. We attempted to strike a bal- ance between these complementary aspects of current climatological re- search, aiming at a symposium situated in scope about halfway between "Climate in Earth history" (Berger and Crowell, 1982) and "Climate pro- cesses and climate sensitivity" (Hansen and Takahashi, 1984). We con- centrated, therefore, on the last 20,000 years, where the time-scales are potentially good enough to document rapid change.

The content of this book are lectures and research papers presented at the NATO Advanced Study Institute on -Chemistry of the Unpolluted and Polluted Troposphere-held from September 28 to October 10, 1981, on the Island of Corfu, Greece. The realization of the scientific event was made possible by the sponsorship of the NATO Scientific and Environmental Affairs Division. We must express our gratitude first to this Institution for the important assistance and cooperation we received. For additional assistance we are much obliged to our distinguished co sponsors: Carl Zeiss Werk, Oberkochen, FRGj Biotronik GmbH, Frankfurt, FRGj Bodenseewerk Perkin Elmer u. Co GmbH, Ueberlingen, FRGj and TSI Deutschland Inc., Aachen, FRG. To Mr. Dimitris Bouas, the Director of the Grand Hotel Glyfada, we would like to express our thanks and appreciation for the excellent services. The Center of Environmental Protection of the University of Frankfurt, FRG, conducted the NATO Advanced Study Institute because of the rapidly increased interest in the problems of air chemistry and air pollution. This development has contributed in recent years to a significant expansion of knowledge in the field of atmospheric chemistry, where several of the classic disciplines like meteorology, physics and chemistry have joined in combined research. The Advanced Study Institute offered an ideal opportunity to give a comprehensive survey of the present knowledge in this relatively new field of atmospheric science.

This was the fourth postgraduate summer school on remote sensing to be held in Dundee. These summer schools were originated by, and continue to remain in, the programme of EARSel (European Association of Remote Sensing Laboratories) Working Group 3 on Education and Training in Remote Sensing. The first of these summer schools was held in 1980 on "Remote Sensing in Meteorology, Oceanography and Hydrology." This was followed in 1982 by a more specialised summer school on "Remote Sensing Applications in Marine Science and Technology" which built on the foundation laid in 1980 and then concentrated on the marine applications of remote sensing techniques. The present summer school was another follow-up of the original 1980 summer school but this time concentrating on the atmospheric rather than the marine applications of remote sensing techniques. The 1984 summer school had not specifically involved atmospheric and marine applications but had been involved with the use of remote sensing in the field of civil engineering. This year's summer school was extremely successful. First of all, this was due to our sponsors, for without their very significant material contributions there would have been no summer school. These sponsors included the Scientific Affairs Division of NATO, together with the European Association of Remote Sensing Laboratories, the Council of Europe, the European Space Agency, the German Aerospace Establishment (DFVLR) and the Natural Environment Research Council.

The development of numerical integration techniques and the pioneering efforts of Von Neumann and his associates at the Institute for Advanced Studies (Princeton) have spurred the renewed interest of many leading fluid dynamicists and meteorologists in the theory and numerical simulation of planetary atmosphere and oceans circulations. Their work during the last 15 years, now culminating in the Global Atmospheric Research Program, has led to the possibility of vastly improved weather forecasts as wei I as the development of a ful I fledged branch of the physical sciences: geophysical fluid dynamics. Simultaneously, great strides have been made in developing new instruments, operating from earth orbiting satel I ites, to powerful observe the meteorological phenomena and to determine the state of motion of the atmosphere. Centre National d'Etudes Spatiales (CNES) of France has very significantly contributed to this effort by developing the EOLE navigation and data collection satell ite, launched on 16 August 1971 to interrogate 500 instrumented platforms measuring meteorological para meters. It is fitting then, that CNES should have brought together lead ing scientists in the field of dynamic meteorology, to participate in its 1970 Summer School on Space Physics.

The present monograph is dedicated to a new branch of the theory of climate, which is titled by the authors, "Mathematical Theory of Climate. " The foundation of this branch is the investigation of climate models by the methods of the qUalitative theory of differential equa tions. In the Russian edition the book was named "Fundamentals of the Mathematical Theory of Climate. " Respecting the recommenda tions of Wayne Yuhasz (we are truly grateful to him for this advice), we named the English edition of the book "Mathematics of Climate Modelling. " This title appears to be more appropriate, since the con structive results of the theory are at present preliminary and have not been fully tested with experiments in climate modelling. This branch of science is yet developing and its practical results will be obtained only in the near future. Nevertheless, we want to keep the terminology which we have used in the introduction to the Russian edition of the book, since the authors hope that this term will be accepted by the scientific community for identification of a given branch of climate theory. On preparing the English edition, new ideas were established con necting some significant new research results obtained by the author. We are deeply grateful to G. Marchuk for continual encourage ment of this scientific enterprise and fruitful discussions, to our young colleagues A. Gorelov, E. Kazantsev, A. Gritsun, and A."

Geysers. What makes them work? Many who have seen a geyser in action know only that it spouts hot water into the air. Many others have never seen one. Chapter 1, Geysers of the World, delineates their distinguishing features, locates the geyser regions of the world, and places investigations by world travelers and scientists in historic perspective. One of the quickest ways to become acquainted with a geyser is to observe it. The descriptions of several well known geysers, some based on past observations by others, but frequently by me, do not neces sarily portray current behavior. They do, however, represent general features. Geysers exist as a result of a delicate and unique interplay among the heat, the water, and the rocks of the earth. In essence, heat and water must be available, transported, distributed, stored, and finally released. Chapter 2, The Geologic, Thermal, and Hydrologic State of the Earth, especially that close to its surface, sets the stage for Chapter 3, Fundamentals of Geyser Operation. The geyser is treated here as a simple system consisting of three major interacting elements: a source of water, a source of heat, and a reservoir for storing water. The discus sion centers around the actions occurring within idealized columnar and pool geysers, and more complex systems. Some of the more workable geyser theories are evaluated."

In Nordic literature a remarkable discussion of the northern light appears in Kongespeilet (The King's Mirror) a thirteenth-century Norwegian chronicle. It is described in vivid detail as the following translated excerpts demonstrate: These northern lights have this peculiar nature, that the darker the night is, the brighter they seem, and they always appear at night but never by day, most frequently in the densest darkness and rarely by moonlight. In appearance they resemble a vast flame of fire viewed from a great distance. It also looks as if sharp points were shot from this flame up into the sky; these are of uneven height and in constant motion, now one, now another darting highest; and the light appears to blaze like a living flame. Three different theories for the origin of the northern light were suggested in this book. Numerous naturally occurring heavenly phenomena have been observed and enjoyed as long as the Earth has been inhabited, but hardly any of them has stirred man's imagination, curiosity and fear as much as the northern light. The northern light is certainly one of the most spectacular of nature's phenomena.

These proceedings are based upon the review lectures, the re search talks and the accompanying discussion from the NATO Advanced Study Institute on "The Dynamical and Chemical Coupling of the Neutral and Ionized Atmosphere" held at Spatind, Norway April 12-22, 1977. In recent years, in spite of the many subdivisions of atmospher ic physics it has become clear that a complete understanding of the subject matter requires an interdisciplinary effort of the scien tists working on a variety of atmospheric phenomena. This Advanced Study Institute was organized in order to meet this demand. A number of eminent scientists were invited to review the major subfields in atmospheric physics and expose the areas where the coupling between the neutral and ionized atmosphere is evident. These review papers were supported by current research results. However, the material covered here is by no means complete con sidering the range of subject matter covered by the title. The re sponsibility for this inadequacy lies with the editors and the pro gram committee, rather than with the individual contributors. Oslo, June 1977. B. Grandal J.A. Holtet. PARTICIPANTS Max-Planck-Institute for Nuclear Physics Arnold, F. P.O.Box 1248, D-0069 Heidelberg F.R.G. Bj centsrn, L. Uppsala Ionospheric Observatory S-755 90 Uppsala Sweden The Institute for Mathematical and Physical Brekke, A."

The ideas in this book have been developed over the past three or four years while I was working at the Institute of Geological Sciences and later for Golder Associates. During that time all of the geological modelling and resource estimation studies I participated in had data that were non-ideal in one respect or another (or just plain 'dirty'): the standard ways of handling the data with kriging or with simpler parametric methods gave reason able results, but always there were nagging doubts and some lack of confidence because of the corners that had to be cut in generat ing a model. The bimodal distribution that was assumed to be 'close enough' to normal; the pattern of rich and poor zones that was not quite a trend yet made the data very non-stationary; and the many plotted variograms that would not fit any standard model variogram: these all contributed to the feeling that there should be something that statistics could say about the cases where hardly any assumptions could be made about the properties ofthe parent population."

Solar and geomagnetic variability are of considerable interest for scientists of many different persuasions and indeed one has the distinct impression that for the sun at least, there is direct relevance for mankind in general as the interrelation between solar and terrestrial phenomena is starting to be appreciated. From the vast time scale of interest in the variability field, attention was confined to the last 10,000 years in a NATO Advanced Research Workshop held from April 6 - 10, 1987 in Durham, England, and the present publication comprises the lectures given there. Such a Workshop was very timely in view of the impressive new data available from 14C analysis in dated tree rings and lOBe in polar ice cores, from natural palaeomagnetic records in lacustrine sediments and from archaeomagnetic material. Also to be mentioned are new studies of historical accounts of naked-eye sunspots and aurorae. All the data have contributed to improvements in under standing the relative variations of solar properties, the geomagnetic field and climate and it is hoped that this volume will convey the flavour of these advances in knowledge. A feature of the Workshop was the lively discussions which followed so many of the papers. There were several instances of healthy disagreement and this is reflected in the opposing views presented inanumber of the papers published here."

This self-contained text/reference provides a basic foundation for practitioners, researchers, and students interested in any of the diverse areas of multiscale (geo)potential theory. New mathematical methods are developed enabling the gravitational potential of a planetary body to be modeled using a continuous flow of observations from land or satellite devices. Harmonic wavelets methods are introduced, as well as fast computational schemes and various numerical test examples. Presented are multiscale approaches for numerous geoscientific problems, including geoidal determination, magnetic field reconstruction, deformation analysis, and density variation modelling With exercises at the end of each chapter, the book may be used as a textbook for graduate-level courses in geomathematics, applied mathematics, and geophysics. The work is also an up-to-date reference text for geoscientists, applied mathematicians, and engineers.

The main aim of this paper is to present some new and general results, ap plicable to the the equations of two phase flow, as formulated in geothermal reservoir engineering. Two phase regions are important in many geothermal reservoirs, especially at depths of order several hundred metres, where ris ing, essentially isothermal single phase liquid first begins to boil. The fluid then continues to rise, with its temperature and pressure closely following the saturation (boiling) curve appropriate to the fluid composition. Perhaps the two most interesting theoretical aspects of the (idealised) two phase flow equations in geothermal reservoir engineering are that firstly, only one component (water) is involved; and secondly, that the densities of the two phases are so different. This has led to the approximation of ignoring capillary pressure. The main aim of this paper is to analyse some of the consequences of this assumption, especially in relation to saturation changes within a uniform porous medium. A general analytic treatment of three dimensional flow is considered. Pre viously, three dimensional modelling in geothermal reservoirs have relied on numerical simulators. In contrast, most of the past analytic work has been restricted to one dimensional examples."

The contents of this volume are based largely on a symposium on cloud dynamics held in Hamburg, Germany, as a part of the Third General Assembly of the International Association of Mete- orology and Atmospheric Physics (IAMAP), 17-28 August-1981. Plans for this symposium were initiated by the Cloud Dynamics Group, appointed through the International Commission for Dynam- ic Meteorology (ICDM), IAMAP. Members of this group are Bruce Morton - Chairman, Australia; Tomio Asai - Secretary, Japan; E. M. Agee, USA; V. Andreyev, Bulgaria; K. Fradrich, FRG; M. W. Moncrieff, UK; R. S. Pastushkov, USSR; J. P. Chao, PR China; Bh. V. Ramanamurti, India; W. Roach, UK; J. Simpson, USA; J. T. Steiner, New Zealand; M. Yanai, USA. E. M. Agee served as con- vener of the symposium in Hamburg. Dynamic meteorology has grown rapidly and covered a great variety of fields since the foundation of ICDM, making it increas- ingly difficult for the Commission to manage all activities. In order to improve this situation, some ad-hoc Working Groups within ICDM were organized at the 1977 IAMAP meeting in Seattle. Each of these working groups, such as the one in Cloud Dynamics, deals with a particular sub-field of dynamic meteorology.

Long-Range Transport of Airborne Pollutants and Acid Rain Conference This issue of Water, Air, and Soil Pollution is devoted to the collection of papers presented at the Long-Range Transport of Airborne Pollutants and Acid Rain Con ference held at Albany, N.Y., April 27-30, 1981. The issue includes most of the invited papers as well as a good number of the poster papers. The conference consisted of seven plenary sessions at which the invited papers were presented. After each session the participants discussed the session topic in the poster area where the subject was further explored and expanded. The seven technical sessions were: (1) Networks. (2) Models of Delivery. (3) Interactions with Soils and Ground Water. (4) Calibrated Water Sheds. (5) Effects on Aquatic Biota. (6) Effects on Terrestrial Biota. (7) Health implications. The closing session was devoted to the topic 'The Application of Scientific and Technical Data to the Development of Government Policy; Acid Rain - A Case Study'. The four papers given are not included here."

On the 6th, 7th' and 8th April 1983, a conference entitled "Magnetism, planetary rotation and convection in the Solar System" was held in the School of Physics at the University of Newcastle upon Tyne. The purpose of the meeting was to celebrate the 60th birthday of Prof. Stanley Keith Runcorn and his, and his students' and associates', several decades of scientific achievement. The social programme, which consisted of excursions in Northumberland and Durham with visits to ancient castles and churches, to Hexham Abbey and Durham Cathedral, and dinners in Newcastle and Durham, was greatly enjoyed by those attending the meeting and by their guests. The success ofthe scientific programme can be judged by this special edition of Geophysical Surveys which is derived mainly from the papers given at the meeting. The story starts in the late 1940s when the question of the origin of the magnetic field of the Earth and such other heavenly bodies as had at that time been discovered as having a magnetic field, was exercising the minds of several scientists; notably P. M. S. Blackett at Manchester, W. M. Elsasser at the University of Pennsylvania and E. C. Bullard at Cambridge. Two alternative mechanisms were proposed. In one the magnetic field was in some way connected with the distributed angular momentum of a rotating body; in the other, electric currents in conducting parts within the body were proposed as the source of magnetic field.

This IMA Volume in Mathematics and its Applications STOCHASTIC MODELS IN GEOSYSTEMS is based on the proceedings of a workshop with the same title and was an integral part of the 1993-94 IMA program on "Emerging Applications of Probability." We would like to thank Stanislav A. Molchanov and Wojbor A. Woyczynski for their hard work in organizing this meeting and in edit ing the proceedings. We also take this opportunity to thank the National Science Foundation, the Office of N aval Research, the Army Research Of fice, and the National Security Agency, whose financial support made this workshop possible. A vner Friedman Willard Miller, Jr. v PREFACE A workshop on Stochastic Models in Geosystems was held during the week of May 16, 1994 at the Institute for Mathematics and Its Applica tions at the University of Minnesota. It was part of the Special Year on Emerging Applications of Prob ability program put together by an organiz ing committee chaired by J. Michael Steele. The invited speakers represented a broad interdisciplinary spectrum including mathematics, statistics, physics, geophysics, astrophysics, atmo spheric physics, fluid mechanics, seismology, and oceanography. The com mon underlying theme was stochastic modeling of geophysical phenomena and papers appearing in this volume reflect a number of research directions that are currently pursued in these areas."

Hurricanes of the North Atlantic Ocean have left their imprint on the landscape and human cultures for thousands of years. In modern times, fewer lifes have been lost due, in part, to the development of modern communication systems, and to improved understanding of the mechanisms of storm formation and movement. However, the immense growth of human populations in coastal areas, which are at risk to hurricanes, has resulted in very large increases in the amount of property damage sustained in the last decade in the Atlantic, Gulf of Mexico and Caribbean regions. This book is of interest to climatologists and meteorologists and as source of information for policymakers and emergency management planners.

Practical reservoir engineering techniques have been adequately described in various publications and textbooks, and virtually all useful techniques are suit able for implementation on a digital computer. Computer programs have been written for many of these techniques, but the source programs are usually not available in published form. The purpose of this book is to provide a central source of FORTRAN-coded algorithms for a wide range of conventional reservoir engineering techniques. The book may be used as a supplementary text for courses in practical reservoir engineering. However, the book is primarily intended for practicing reservoir engineers in the hope that the collection of programs provided will greatly facil itate their work. In addition, the book should be also helpful for non-petroleum engineers who are involved in applying the results of reservoir engineering analysis. Sufficient information is provided about each of the techniques to allow the book to be used as a handy reference. ix INTRODUCTION This book provides many of the useful practical reservoir engineering (conven tional) techniques used today in the form of FORTRAN codes. The primaI: y objectives have been to provide the simplest possible method for obtaining reli able answers to practical problems. Unfortunately, these codes can usually be applied by simply following a cookbook approach. However, if at all possible, the solutions obtained should be verified and cross-checked by some other means and, most important, should be checked for reasonability."

Tropical atmosphere and ocean are receiving increased attention in relation to the functioning of the global climate system, the remarkable climatic variability in low latitudes, and the associated manifold environmental and societal consequences. Beyond the traditional emphasis of meteor ology on weather analysis and forecasting, there is a growing interest in the climate and large scale circulation of the tropics. This book may serve as a text for graduate and upper-division undergraduate students in meteorology, and is also intended as a reference work for practicing meteorologists, and researchers in the atmospheric, oceanic, and other environmental sciences. I began writing this book in 1979, but the roots reach further back. Early experiences in North Africa fuelled my curiosity about the low latitudes. In 1960 I seized the opportunity to work in the National Meteorological Service of El Salvador in Central America. My interest in the tropics continued after joining the University of Wisconsin in 1963. Field research brought me to the equatorial Pacific, and many times to the tropical Americas and Africa. This involved visits and correspondence with many weather services. My acquaintance with Australasia and South Asia is limited to short study visits, but includes continuous contacts with colleagues at key research institutions in India, namely the India Meteorological Department, the Indian Institute of Tropical Meteorology, and Andhra University. A guest semester at the University of the Witwatersrand in 1971 and related travels provided a perspective on the problems of Southern Africa."

Numerous experts including ecologists, geneticists, paleontologists and climatologists, investigate the response of terrestrial organisms to changes in their environment. The volume comprises an introductory and a final chapter by the editors as well as another 35 contributions. These are divided into six sections: 1. past environmental changes - the late-Quaternary; 2. spatial responses to past changes; 3. mechanisms enabling spatial responses; 4. evolutionary responses to past changes; 5. mechanisms enabling evolutionary responses; 6. predicted future environmental changes and simulated responses. The overwhelming and unanimous conclusion of all contributors is that forecasted global environmental changes pose a severe threat to the integrity of ecosystems worldwide and to the survival of at least some species.

Coweeta is one of the oldest continuously operating laboratories of its type in the world. For the first time, a complete review and summary of more than 50 years study of the hydrological and ecological responses of baseline and managed Southern Appalachian hardwood forests at Coweeta is now supplied by this volume. The long-term research approach represents a continuum of theory, experimentation and application using watersheds as landscape units of investigation. Thus, the information encompasses a wide range of interpretations and interests. In addition to in-depth analyses of terrestrial and stream processes, the breadth of coverage includes historical perspectives and relevance of ecosystem science to management needs. In a broader sense, the Coweeta research effort is considered from a perspective of national and international forest hydrology and ecology programs.

This book contains a selection of papers that have been prepared for the NATO Advanced Research Workshop on the Economics of Atmospheric Pollution, that took place in Wageningen, The Netherlands, November 1994, hosted by Wageningen Agricultural University and sponsored by NATO Scientific and Environmental Affairs Division. Participants from the USA and a large number of countries in Western, Central and Eastern Europe have participated to discuss the economic aspects of transboundary air pollution and climate change. A number of selected papers have been reviewed and revised on the basis of the comments provided. The editors kindly acknowledge the support of Prof. Charles Kolstad, University of California, Santa Barbara, and Prof. Stef Proost, Center for Economic Studies, Catholic University Leuven, for reviewing several chapters of the book. Also the assistance of several anonymous reviewers is kindly acknowledged. We hope that the book will contribute to a better understanding of the most relevant issues in the area of international policymaking on transboundary pollution and climate change, and that it contributes to further economic analysis in this interesting research area. The topic of transboundary pollution related to climate change, acidification and tropospheric ozone will in the coming decades continue to be relevant for all countries in the world. Ekko van Ierland Kazimierz Gorka WageningeniCracow, June 1996 CONTENTS 1 On tbe Economics of Atmospberic Pollution Ekko van IerJand Wageningen Agricultural University, The Netherlands.

In 1986, an International Symposium on Monitoring of Gaseous Pollut- ants by Tunable Diode Lasers was organized by the Fraunhofer-Institut fuer Physikalische Messtechnik in Freiburg, FRG, and held at this institution on November 13-14, 1986. The papers presented at that occasion extensively covered the applications of tunable diode laser spectroscopy (TDLS) to the analysis of trace and exhaust gases together with the latest improvements brought to the tech- niques used. It was generally consented by the participants that meetings of this kind are of major importance and should take place on a regular basis. The organizers were thus encouraged to plan a Second International Sympo- sium on Monitoring of Gaseous Pollutants by Tunable Diode Lasers which was held two years later on October 17-18, 1988, again in Freiburg. In addi- tion to the main subjects treated in the first Symposium, the Scientific Programme this time presented a session on the development of lead chalco- genide lasers. Once more, only a limited attention was given to applica- tions in high resolution molecular spectroscopy. In order to complete the update, sessions on components and techniques were included in the Pro- gramme. As for the previous Symposium, some space was also given to alter- native optical techniques. This time, in particular contributions on laser photoacoustic detection were included.

'Ibis volt.nne contains the proceedings of a \\Orkshop on "Acid Deposition" held on September 9, 1982 at the Reichstag in Berlin. 'Ibe \\Orkshop was organized within the frame\\Ork of project COST 61a bis* of the Commission of the European Communities (CEC), as a satellite meeting to the joint meeting of WOrking Parties 4 (Pollutant Cycles) and 5 (Transport and Modelling - Field Experiments) which was held on September 7 - 8 at the Federal Environmental Agency in Berlin. 'Ibe organisation of the scientific \\Orkshop programme was in the hands of a CEC Acid Deposition Task Force consisting of nine scientists actively participating in projects COST 61a or COST 61a bis : Beilke (Federal Republic of Germany), Brosset (Sweden), Elshout (The Netherlands), Graven- horst (France), Liberti (Italy), ott (CEC, Belgium), Penkett (United Kingdan), Sandroni (CEC, Italy) and Zephoris (France). 'Ibe \\Orkshop progrcmne consisted of the presentation and discussion of five invited review papers covering different areas of the acid deposition problem and of ongoing \\Ork on topics which are relevant to acid depo- sition. Emphasis was placed on new scientific ideas and on indicating the most important areas of uncertainty, including the specification of a series of key research needs in the field of acid deposition. 'Ibis was done out of concern for danage to forest and freshwater ecosystems in various European regions attributed at least in part to acid deposition originating fran air pollution.