Textbook ofEnvironmental Biotechnology

Pradipta K. Mohapatra

I.K. International Publishing House Pvt. Ltd.New Delhi • Mumbai • Bangalore

Published byI.K. International Publishing House Pvt. Ltd.S-25, Green Park ExtensionUphaar Cinema MarketNew Delhi 110 016 (India)E-mail: ik_in@vsnl.net

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Preface

The advancement of technology and increase in the rate of consumption ofresources has led to the overexploitation of all possible natural resources onthe earth. As a result, despite variable levels of advancement of processingtechnologies, each industrial and consumption activity is causing the loss ofsome part of the resource as waste. In addition, many unwanted byproductsare produced and released to the environment, causing many problems, themost important being water pollution, the addition of xenobiotics into theenvironment, land degradation and biodiversity loss due to global climaticchanges.

The growing awareness of environmental problems has made us thinkabout alternative technologies that are less polluting and more environmentalfriendly. The focus is now on the development and use of processes that areless chemical and based mostly on renewable resources. The pure chemicalpathways are now considered environmentally unsustainable, forcing us tosearch for biological alternatives. Environmental biotechnology has emergedas a solution to improve the quality of the environment and productionstandards. The importance is on the use of renewable raw materials as anenergy source, especially wastes, that have hitherto been considered uselessand have required expenditure to dispose them.

The emerging areas of environmental biotechnology are (i) developmentof novel and environmentally improved production technologies with goodquality end-products, but fewer byproducts (or wastes), (ii) use of less purifiedsubstrates (and wastes) for the production of required products of good qualitywith acceptable costs without causing any problems to the environment, (iii)improved methods of resource use with substantial reduction of wastegeneration, (iv) controlled production of very specific biocatalysts, (v) plannedand efficient consumption of bioresources to get maximum benefit from thelimited biomass, (vi) development of technology for the protection andcontinuance of the existing local as well as global biodiversity, (vii) recyclingof the industrial byproducts to reduce the problem of pollution, and (viii) useof biological organisms to reclaim the contaminated habitats.

Many publications have warned about the global shortage of energy andresources in the future due to unsustainable usage of non-renewable naturalresources. In addition, the limits for an ecologically and economicallycompatible disposal of production residues and stabilised wastes have to betaken into consideration, more and more. The limits for disposal of solid andliquid pollutants into soil and water or of waste gases into the atmosphere area major issue, since soil, water and air are no longer able to absorb/adsorb

these emissions without negative consequences on ecology and life. Theultimate oxidation product of organic residues by physicochemical degradationand/or biological respiration has led to a significant increase in the carbondioxide content of the atmosphere, in the last few centuries, and thus influencedthe overall climate through global climate change. The increase is abundantlyattributed to combustion of fossil fuels for industrial production processes,and transport, in addition to the reduced rate of carbon utilisation.

The pollution of soil with domestic and industrial wastes and their(bio)conversion products generally remains a locally restricted, regional ornational problem. However, if the evaporation of volatile compounds into theair or solubilisation of solids in rain or groundwater is not prevented, air andwater pollution will soon reach a international dimensions. A disturbance ofthe equilibrium of the natural cycles of carbon, nitrogen, phosphorus, sulphuror halogen compounds causes an ecological imbalance and endangers nature.In the Brundtland report “Our common future” a discussion was made about“sustainable development.” The practical realisation of this concept wassuggested at the “Conference on Environment and Development” of the Unitednations, in Rio de Janeiro, in 1992 and enforced as an action programme inAgenda 21. A sustainable development to maintain the basis for futuregenerations is contraindicated by exploitation of non-regenerative energy andmaterial resources and a shortening of life cycles.

Substantial progress has been made in the field of industrial biotechnologyand this has caused significant reduction of the cost of many industrialproducts, like proteins, enzymes, vitamins and antibiotics. However, suchprocesses are also generating production residues which require furtherinvestment and infrastructure to treat them. Environmental biotechnologyhas emerged as an associated technology the industrial production processesso as to make the latter environment friendly. Environmental biotechnology,initially started with wastewater treatment in urban areas, has been extended,among others to soil remediation, off gas purification, pesticide degradation,heavy metal removal, surface and groundwater cleaning, industrial wastewaterpurification, deposition techniques of wastes in sanitary landfills, compostingof bioorganic residues, environmental risk analysis and biopesticidedevelopment. This book “Environmental Biotechnology” covers many of theabove aspects in a comprehensive form. The book contains 18 chapters coveringdifferent environmental problems and presents up to date developments inthat field. I hope that the presented comprehensive overview on processes ofenvironmental biotechnology for liquid, solid and gaseous waste treatment,pesticides and heavy metal removal and biodiversity management will helpstudents and professional experts to obtain fast fundamental information andan overview the biological background and general process alternatives. Inmy assessment, this book will definitely be a good textbook for the studentsof environmental sciences, biotechnology, environmental engineering andmicrobiology.

Author

iv Preface

Contents

Preface iii

1. Issues and Scope of Environmental Biotechnology 11.1 Introduction 11.2 Issues for Environmental Biotechnology 21.3 Scope of Environmental Biotechnology 81.4 Conclusion 24

2. Management and Remediation of Problem Soils 252.1 Introduction 252.2 The Management Steps for Problem Soil Remediation 262.3 Management of Coastal Saline Soil 272.4 Management of Alkali Soils 362.5 Management of Mine Waste Soil 392.6 Remediation of Soil Polluted with Organic Pollutants 442.7 Management of Other Problem Soils 612.8 Conclusion 66

3. Bioaccumulation of Toxicants 673.1 Introduction 673.2 Characteristics of Xenobiotics 673.3 Evolution of the Concept 733.4 Relationship of Bioaccumulation with Chemical Structure 753.5 Ecophysiology of Bioaccumulation 803.6 The Process of Toxicants’ Uptake: Kinetic Aspect 843.7 Factors Affecting Bioaccumulation of Xenobiotics 903.8 Measurement of Bioaccumulation 923.9 Kinetic Modeling of Bioaccumulation 963.10 Conclusion 100

4. Biological Treatment of Wastewater 1014.1 Introduction 1014.2 Microbial Processes in Wastewater Treatment 1024.3 The Microbial Biofilm and Wastewater Treatment 1044.4 Operational Practicalities of Biological Oxidation of Wastewater 1104.5 Secondary Treatment Systems 1134.6 Microbial Removal of Nitrogen and Phosphorus 1314.7 Nutrient Removal through Biomass Production 1394.8 Conclusion 147

5. Treatment of Wastewater of the Food Processing Industries 1485.1 Introduction 1485.2 Sugar Factories 1495.3 Starch Factories 152

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5.4 Vegetable Oil Industries 1535.5 Potato Processing Industry 1565.6 Slaughterhouses 1585.7 Dairy Industry 1595.8 Fruit Juice and Beverage Industry 1615.9 Breweries 1635.10 Distilleries 1645.11 Conclusion 166

6. Biotechnological Approaches to Microalgal Culture 1676.1 Introduction 1676.2 Why Microalgae? 1686.3 Microalgal Species for Aquaculture 1716.4 Mass Cultivation Technique 1736.5 The Culture Systems 1846.6 Closed and Semi-closed Outdoor Culture Systems 1896.7 Immobilisation of Cells 1936.8 Harvesting and Drying of Algal Biomass 1966.9 Bioaugmentation for Commercial Production of Algae 1976.10 Conclusion 199

7. Biodegradation of Organic Pollutants 2017.1 Introduction 2017.2 Biodegradable Organic Pollutants 2027.3. Principles of Bacterial Degradation 2127.4. Aerobic Bacterial Degradation of Biopolymers 2227.5. Anaerobic Bacterial Degradation of Biopolymers 2347.6. Cometabolic Degradation of Organopollutants 2537.7. Degradative Capacities of Fungi 2567.8. Conclusion 262

8. Biotechnology for Solid Waste Management 2648.1 Introduction 2648.2 Basic Aspects of Solid Waste Management 2658.3 The General Composition of Urban Solid Wastes 2658.4 Current Practice of Solid Waste Management in India 2688.5 Waste disposal by Sanitary Landfilling 2708.6 Aerobic Treatment of Solid Wastes: Composting 2838.7 Aerobic Treatment of Solid Wastes: Vermiculture 2948.8 Anaerobic Treatment of Solid Wastes and Biogas Generation 2978.9 Comparison of Aerobic and Anaerobic Solid Waste Treatment 3078.10 Treatment of Hazardous Wastes 3098.11 Biomedical Waste Management 3138.12 Conclusion 314

9. Biodegradation of Pesticides in the Environment 3169.1 Introduction 3169.2 Types of Pesticides 3179.3 Fate of Pesticides in the Environment 3249.4 Microbial Adaptation to Pesticide Contaminated Environment 3269.5 Microorganisms and Pesticide Waste Treatment 3289.6 Enzymes Catalysing Pesticide Degradation Reactions 336

Contents vii

9.7 Molecular Aspects of Pesticide Degradation 3509.8 Conclusion 355

10. Microbial Transformation of Heavy Metals 35710.1 Introduction 35710.2 Heavy Metal Toxicity in the Environment 35810.3 Microbes in Metal Containing Habitat 36110.4 Heavy Metal Tolerance 36410.5 Metal-Microbe Interactions 36510.6 Microbial Immobilisation and Transformation of Metals 36910.7 Genetic Aspects of Heavy Metal Resistance 37710.8 Microbial Applications for Metal Removal 38810.9 Conclusion 393

11. Bioleaching and Biomining for Recovery of Resources 39511.1 Introduction 39511.2 Microbes in Bioleaching Process 39611.3 Metal Recovery by Bioleaching Process 39711.4 Microbial Recovery of Phosphate 40611.5 Microbial Extraction of Petroleum 40711.6 Microbial Production of Fuels 41011.7 The Problems and Prospects of Biomining and Biofuel Production 41311.8 Conclusion 414

12. Microbial Transformations of Pesticides 41512.1 Introduction 41512.2 Fundamental Reactions of Pesticide Metabolism 41612.3 β-Oxidation 41712.4 Oxidative Dealkylation 41812.5 Thioether Oxidation 42212.6 Decarboxylation 42312.7 Epoxidation 42312.8 Aromatic Hydroxylation 42412.9 Aromatic Non-heterocyclic Ring Cleavage 42612.10 Aromatic Heterocyclic Ring Cleavage 42812.11 Hydrolysis 43212.12 Halogen Reactions 43412.13 Nitro Reduction 43812.14 Miscellaneous Reactions 43812.15 Conclusion 439

13. Aquatic Bioassay for Analysis of Pollutants in Surface Waters 44013.1 Introduction 44013.2 Bioassay for Acute Toxicity Test 44013.3 Experimental Approach for Sub-acute and Chronic Toxicity Tests 44613.4 Enzymatic Tests for Bioindication 46013.5 Biosensors for Bioindication 46413.6 In Place Studies for Bioindication 46913.7 Conclusion 475

14 Environmental Impact of Pollutants and Analysis ofDose-Effect Relationship 47614.1 Introduction 476

viii Contents

14.2 Doses of Toxicants 47614.3 Uptake and Retention 47914.4 Dose Commitment 48714.5 Dose-Effect Relationship 48914.6 Quantal Response 49314.7 The Graded Response 50014.8 Application of Dose-Effect Relationship 50114.9 Conclusion 503

15. Management of Biological Diversity andEcosystem Restoration 50415.1 Introduction 50415.2 The Values of Biodiversity 50515.3 Threats to Biodiversity Conservation 50915.4 Management of Biodiversity Hot-Spots 52015.5 Biosphere Reserves and Ecosystem Conservation 52315.6 Socio-Economic Approach to Management of Local Plant Biodiversity52815.7 The Modified Approach to Bioresource Conservation Programme 53215.8 International Initiatives for Biodiversity Management 53615.9 Conclusion 544

16. Biotechnology in Biodiversity Conservation 54516.1 Introduction 54516.2 Biotechnological Processes for Bioresource Assessment 54616.3 Biotechnology in ex situ Conservation of Biodiversity 54816.4 Biotechnology and its Role in Utilisation of Biodiversity 55416.5 Biotechnology vs Biodiversity 55716.6 Conclusion 560

17. Modeling of Bioreactors 56117.1 Introduction 56117.2 Modelling of Activated Sludge Process 56117.3 Modelling of Biogas Reactors 57017.4 Modelling of Biogas Tower Reactor 57817.5 Mass Transport from the Liquid Phase to the Gas Phase in BTR 58717.6 Modelling of Solid Waste Bioreactors 58817.7 Conclusion 600

18. Biopesticides and Integrated Pest Management 60118.1 Introduction 60118.2 Pest Control: The Past 60218.3 Genesis of IPM Concept 60418.4 Why IPM? 60618.5 Ecology and IPM 60718.6 Practical Implementation of IPM 61018.7 National and International Perspectives of IPM 61418.8 IPM: Theory to Practice 61818.9 Biopesticides in IPM Programme 62118.10 Conclusion 634

References 635

Index 655

1

Issues and Scope of EnvironmentalBiotechnology

1.1 INTRODUCTION

Biotechnology has emerged as a new area of research and developmentin the field of biological sciences, through the integration of technologywith biology. This technological integration has been made for theaugmentation of agricultural production, accelerated production of plantand animal biomass, optimisation of production, extraction and processingof bioproducts, and application of biology for human welfare. This hasbeen felt necessary in the last few decades so as to augment world foodproduction, to improve human health through production and make foreasy availability of drugs. Many plant and animal products, which werenot affordable to common people a few years before, are now availableat every corner of the world, only due to decrease in prices and accelerationof their production. For example, drugs like insulin, which were notaffordable to the common man of third world countries a few years back,can now be purchased by anybody due to its accelerated and cost effectiveproduction through the application of biotechnology from geneticallyengineered microorganisms (GEM). The cost of many enzymes, proteins,antioxidants and antibiotics have decreased substantially due to theimprovement in production, extraction and processing. However, thetraditional biotechnological approach has not able to solve many problemsof the environment, like resource depletion, global warming, habitatdegradation and environmental pollution.

The ever-increasing temptation of man to lead an improved andcomfortable life has caused significant damage to his own environment.Large-scale industrialisation, release of industrial and domestic wastes tothe environment, depletion of natural resources, faster rate of consumptionof natural resources, degradation in the quality of land, air and water and

2 Textbook of Environmental Biotechnology

scarcity of potable water are the result of overuse and abuse of theenvironment, by man-made processes. Gradual increase in the per capitaconsumption, mechanisation of life, decrease in the per capita arable land,and worldwide increase of population are the principal causes of resourcescarcity and environmental degradation. Environmental degradation hasnow become an unavoidable problem and it is now necessary to think ofnew technologies for the reclamation of degraded resources andminimisation of the degradation process of the existing resources toprovide man a safer environment.

1.2 ISSUES FOR ENVIRONMENTAL BIOTECHNOLOGY

1.2.1 International Issues

The problems like climate changes and global warming, marine pollution,oil spill, air pollution and energy crisis have emerged as internationalissues for attention through environmental biotechnology.

(a) Global Warming and Climate Change

During the 1990s, climate changes emerged as the major threat to thesurvival of the existing biodiversity and have threatened the quality ofthe present-day environment. The International Panel on Climate Change(IPCC) concluded that climate changes could lead to a severe adverseimpact on ecosystems, and on the goods and services they provide (IPCC2001). Some ecosystems might disappear while some others couldexperience dramatic changes in species composition.

The impact of climate changes is quite clear from the recentabnormalities in the global environment. Increased irregularities inmonsoon rains in India and East Asia, frequent occurrence of warm oceaniccurrents, and consequent drought and forest fires, decline of amphibiansin the tropical montane forest (Pounds et al. 1999) and decline in theground water reserve in the tropics are the result of global warming andclimate changes. The major causes of global warming have been attributedto the worldwide increase of energy consumption, deforestation andmethane emission from rice fields and swampy habitats. A reduction,over time, of the productivity of the tropical rain forest has been recorded,in addition to the lowering of the addition of organic litters to forest soil.

(b) Marine Pollution

An increasing incidence of coral bleaching has been reported and attributedto the global increase in ocean temperature. Reports of coral bleachinghave increased in the last decade, with all records of mass bleachingoccurring after 1989. The most significant mass bleachings have beenassociated with the 1997–98 ENSO event, in which all ten reef provinces

Issues and Scope of Environmental Biotechnology 3

of the world were affected. In some areas, most notably the Indian ocean,this event was followed by mass mortality, where up to 90% of all thecorals died over 1000s of square kilometres (Goreau et al. 2000). Suchworldwide bleaching of corals has not only been attributed to acomparatively elevated ocean temperature, but also to the toxicantsreleased into the ocean environment through dangerous fishing activities.

The greatest degree of pollution has been noted in the coastal oceanswhich contribute most of the biomass to the terrestrial and oceanic foodchain. Entry of the nutrient loaded freshwater from the land is the majorcause of changes in the density and diversity of life forms in the coastaloceans. Eutrophication, appearance of toxic algal bloom and sedimentationare the major threats to the aquatic flora and fauna of coastal oceans.There are reports that in many coasts of the world there is a higher rateof sedimentation due to the entry of colloidal clay particles throughfreshwater inflow from the land. More amounts of biomass are beingadded to the sediment and there is a greater degree of anaerobic activityin the sediment, than in the past. Significant emission of methane hasbeen reported not only in the coastal habitat, but also from the floor ofthe deep ocean.

(c) Air Pollution

Increased incidence of air pollution in last few decades has been attributedto three major areas: (i) industrialisation, (ii) vehicular ehaustion and (iii)deforestation. The least emphasis minor importance is on waste depositionand soil erosion. Though numerous gases are being emitted into theatmosphere, the most important gases, which need attention for theirreduction to acceptable levels are the oxides of nitrogen and sulphur,volatile carbon compounds and the greenhouse gases.

(d) Energy Crisis

Of late it has been realised that conventional energy sources cannot supporthuman activities for an indefinite period and, more or less, a global crisisis being felt in the energy sector. The crude oil price has gone to an alltime high in the recent past as it crossed $50 a barrel in 2005. There is alsoa proportionate decrease in the coal and mineral reserves and a declineof forest cover in the developing countries, due to due the collection offirewood. There is a search to reduce energy consumption through efficienttechnology and to generate as much as energy possible, from non-conventional sources, so as to reduce the burden on the traditional energyreserves. There is a search for and attempt to develop an environmentfriendly technology for the production of energy, to satisfy energy demandswhich are increasing exponentially everyday.

4 Textbook of Environmental Biotechnology

(e) Oil Spills

Oil spills have also been considered as a major threat to the worldenvironment, in general and the marine ecosystem, in particular. Thealarming rate of decline in the mangrove forests in the West Asiancountries is due to oil withdrawal and oil spills in the coastal soil andocean. There are also accidental releases of oil into the ocean environmentduring exploration, removal and/or transport. In 1998 alone, a total of108000 tons of oil were spilled worldwide into marine and inlandenvironment as a result of 215 incidents (Etkin 1999). The oil pollution ofthe Gulf region during USA-Iraq war is also the in the minds ofenvironmental scientists.

(f) Decline and Loss of Species

There is an unprecedented change in global biodiversity due to a varietyof ecosystem unfriendly events. The most important amongst them areland conversion, pollution, unsustainable harvesting of natural resourcesand the introduction of exotic species. The relative importance of thesedrivers events differs between ecosystems. For example, land conversionis more intensive in tropical forests, but less intensive in temperate, borealand Arctic regions. Atmospheric nitrogen deposition is more in northerntemperate areas close to cities, but it has less impact on diversity in innerforests. Introduction of exotic species is related to patterns of humanactivity—those areas away from human intervention generally receivefewer introduced species. The ultimate causes of species loss are humanpopulation growth, together with the unsustainable pattern ofconsumption, increasing production of wastes and pollution, urbandevelopment and inequities in the distribution of wealth and resources.

Over the past decades, decline and extinction of species have emergedas major environmental issues. The current rate of extinction is manytimes higher than the “background rate”(estimates based on the fossilrecords suggests that the background extinction rate in mammals andbirds has been 1 species lost in every 500–1000 years; May et al. 1995). Thelatest IUCN red list indicates that about 24% (1130) of mammals and 12%(1183) of bird species are currently regarded as threatened (Hilton-Taylor2000). Since the ‘Red List’ assessment in 1996, the number of criticallyendangered species has increased from 169 to 180 mammals, and from168 to 182 birds (Hilton-Taylor 2000). Analysists suggest that over thenext 100 years, the extinction rate of vertebrate groups could be as highas 15–20%. However, species trends derived from the Red List datashould be interpreted with caution, because the criteria for listing havechanged over time and some of the changes in status reflect taxonomicrevision.

Issues and Scope of Environmental Biotechnology 5

1.2.2 National Issues

The issues that warrant national attention are land degradation, erosionof top soil, siltation of reservoirs, deforestation, formation of degradedsoil, nitrogen deposition in plains, and solid waste problems in urbanareas and conglomerations. The attempt to deal with such issues requiresthe involvement of the national government and development of strategiesat the national level to solve these problems.

(a) Land Degradation

Land degradation has been the cause of reduction in the productivecapacity of arable land. The degradation processes of particular concern,in Asia and Pacific, include erosion, compaction, acidification, decline ofsoil organic matter, weed infestation, soil fertility depletion and biologicaldegradation. Poor agricultural practices contribute to a decline in landproductivity. For example, excessive use of fertilisers and other chemicalshas an adverse effect on soil microflora and they are considered as agentsof soil, as well as water pollution. FAO (2001) estimation indicates that inthe past two decades (1980–2000), fertiliser use has increased at a rate ofaround 4% per year. Government Policies have supported farmers bysubsidising agricultural inputs such as irrigation, fertilisers and pesticidesand have also led to the overuse of such agents, leading to an unhealthyatmosphere in the soil layer for soil dwelling organisms and soil microbialassemblage to act cohesively. Pesticides continue to be usedindiscriminately (some times illegally) in places, and disposed off casually.A survey published by FAO, of countries in Africa and the Near East,reported stocks of unwanted or banned pesticides amounting to morethan 16500 tons at some 1000 sites, in 49 countries (FAO 1995). There aremany pesticides which have been banned for use by the Union AgricultureMinistry (UAM), Govt of India, under its IPM programme but are still inrampant use in India for agricultural and post-harvest pest control.

Degradation of land has also been caused due to several other activities,such as mining, industrialisation, effluent release from the urban areasand weed infestation. Salinity, sea water inundation and water loggingare also found to cause significant damage to arable land in the coastalregions of the country.

(b) Soil Erosion

Soil erosion, a major factor in land degradation, is associated with manyother degradation processes in the environment. The most importantamongst them are increased siltation of reservoirs and minor irrigationprojects, eutrophication of surface waters, reduction of forest regenerationand depletion of productivity of arable land. It also has severe effects on

6 Textbook of Environmental Biotechnology

soil functions, such as the soil’s ability to act as a buffer and filter forpollutants, its role in the hydrological and nitrogen cycle, and its abilityto provide habitat and support life. About 2000 million ha of soil, equivalentto 15% of the earth’s land area, have been degraded through humanactivities. The main types of soil degradation are water erosion, chemicaldegradation, and physical degradation. Overgrazing, deforestation,agricultural activities, overexploitation of vegetation and industrialactivities have acted as positive forces in the erosion of fertile topsoil.

(c) Water Pollution

Water pollution has become a common problem in all areas of the world,in developing and developed counties, alike. The sources of pollutioninclude untreated sewage, chemical discharges, petroleum leaks and spills,dumping in old mines and pits, and agricultural chemicals that are washedoff or seep downwards from crop fields. More than half of the world’smajor rivers are seriously depleted and polluted, degrading and poisoningthe surrounding ecosystems, and threatening the health and livelihood ofthe people who depend on them (World Commission on Water 1999).

There is worldwide degradation of wetlands, in terms of depletion ofthe species, reduction in secondary productivity, abnormal flow of energyin the food webs, eutrophication, shrinking of water bodies andmethanogenic activity in the sediment. Human activities, includingagriculture and settlements, have caused serious damage to thesebiodiversity reserves and contributed to the loss of about 50% of theworld’s wetland, during the 20th century (Finlayson et al. 1999). The bigwetland habitats of the country, Chilka lagoon, Dal lake, lakes of theNorth East, Bharatpur bird sanctuary, etc., are seriously threatened, mainlydue to human activities and pollution. This damage to the ecosystems hasreduced water quality and quantity, leading to a reduction in the effectiveavailability of water for human use.

(d) Nitrogen Deposition

Nitrogen deposition has become a major cause of environmentaldegradation. It has increased substantially in the recent decades, primarilyas a result of deforestation, increased use of fertilisers and burning offossil fuels. Increased nitrogen in soil and water can lead to a loss ofspecies, and shifts in the composition of plant communities. Aquaticecosystems are the most vulnerable, due to the entry of heavy loads ofnitrogen through surface runoff, and discharge of domestic and industrialeffluents. Nitrogen deposition has led to eutrophication, currently one ofthe most serious threats to the aquatic environment, particularly on inshorewaters. It has also been associated with the increase in toxic algal blooms.

In hills and slopes, nitrogen deposition has created problems as inplains and water bodies of lower altitudes. Due to deforestation, nitrogen

Textbook Of EnvironmentalBiotechnology

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