Advances in Agronomy

1. Auflage 2014
ISBN: 978-0-12-802352-5
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 128, 294 Seiten

Reihe: Advances in Agronomy

Advances in Agronomy continues to be recognized as a leading reference and a first-rate source for the latest research in agronomy. As always, the subjects covered are varied and exemplary of the myriad of subject matter dealt with by this long-running serial - Timely and state-of-the-art reviews - Distinguished, well recognized authors - A venerable and iconic review series - Timely publication of submitted reviews

Autoren/Hrsg.

Inhaltsverzeichnis

1;Front Cover;1
2;ADVANCES IN AGRONOMY;3
3;Advances in Agronomy;4
4;Copyright;5
5;CONTENTS;6
6;CONTRIBUTORS;8
7;PREFACE;10
8;Chapter One - Advances in Portable X-ray Fluorescence (PXRF) for Environmental, Pedological, and Agronomic Applications;12
8.1;1. INTRODUCTION;13
8.2;2. HISTORICAL DEVELOPMENT OF XRF SPECTROSCOPY;15
8.3;3. PORTABLE X-RAY FLUORESCENCE (PXRF);23
8.4;4. APPLICATIONS OF PORTABLE XRF IN SOIL AND ENVIRONMENTAL SCIENCES;32
8.5;5. ADVANTAGES AND LIMITATIONS OF PXRF;43
8.6;6. NEW ELEMENTS OF INTEREST AND RECOMMENDATIONS;47
8.7;7. SUMMARY;47
8.8;DISCLAIMER;48
8.9;REFERENCES;48
9;Chapter Two - Environmental Chemistry and Toxicology of Iodine;58
9.1;1. INTRODUCTION;59
9.2;2. INDIGENOUS SOURCES;59
9.3;3. ANTHROPOGENIC SOURCES;63
9.4;4. IODINE TOXICITY;65
9.5;5. IMPACTS ON HUMAN HEALTH;67
9.6;6. ENVIRONMENTAL CHEMISTRY OF IODINE;69
9.7;7. IODINE SORPTION IN HUMIC SUBSTANCES AND SOIL MINERALS;76
9.8;8. REMEDIATION OF IODINE CONTAMINATION;99
9.9;9. CONCLUSION AND FUTURE CHALLENGES;101
9.10;REFERENCES;102
10;Chapter Three - Guttation: New Insights into Agricultural Implications;108
10.1;1. INTRODUCTION;110
10.2;2. PLANT SECRETIONS;111
10.3;3. BOTANICAL DISTRIBUTION OF GUTTATION;113
10.4;4. AGRICULTURAL IMPLICATIONS;116
10.5;5. CONCLUSIONS AND REFLECTIONS FOR FUTURE RESEARCH;138
10.6;ACKNOWLEDGMENTS;140
10.7;REFERENCES;140
11;Chapter Four - Assessing Nutrient Use Efficiency and Environmental Pressure of Macronutrients in Biobased Mineral Fertilizers: a Review of Rece...;148
11.1;1. INTRODUCTION;150
11.2;2. FIELD EXPERIMENTS: GUIDELINES FOR GOOD PRACTICE;153
11.3;3. IMPACT OF FERTILIZATION STRATEGY ON CROP PRODUCTION AND BIOGAS POTENTIAL;163
11.4;4. IMPACT OF FERTILIZATION STRATEGY ON NUTRIENT DYNAMICS IN THE ENVIRONMENT;164
11.5;5. IMPACT OF FERTILIZATION STRATEGY ON GENERAL SOIL QUALITY;181
11.6;6. FERTILIZER MARKETS, LEGISLATIONS, AND RECOMMENDATIONS;186
11.7;7. ECONOMIC AND ECOLOGICAL EVALUATION;187
11.8;8. CONCLUSIONS AND FURTHER RESEARCH;188
11.9;ACKNOWLEDGMENTS;188
11.10;REFERENCES;189
12;Chapter Five - Exploring Options for Lowland Rice Intensification under Rain-fed and Irrigated Ecologies in East and Southern Africa: The Poten...;192
12.1;1. INTRODUCTION;193
12.2;2. DIVERSITY OF NUTRIENT SOURCES;197
12.3;3. REDUCING ENVIRONMENTAL DAMAGE THROUGH IMPROVED NUTRIENT USE EFFICIENCY;214
12.4;4. PROFITABLE PRACTICES WITH HIGH RETURNS TO INVESTMENT;217
12.5;5. ISFM IN RICE SYSTEMS;218
12.6;6. RESEARCH AREAS;220
12.7;7. CONCLUSIONS;221
12.8;ACKNOWLEDGMENTS;222
12.9;REFERENCES;222
13;Chapter Six - Management of Soil Acidity of South American Soils for Sustainable Crop Production;232
13.1;1. INTRODUCTION;233
13.2;2. SOIL TYPES IN SOUTH AMERICA;236
13.3;3. CAUSES OF SOIL ACIDIFICATION;237
13.4;4. MANAGEMENT STRATEGIES;242
13.5;5. CONCLUSIONS;276
13.6;REFERENCES;277
14;INDEX;288

Leseproben

Chapter Two

Environmental Chemistry and Toxicology of Iodine

Ethan M. Cox* and Yuji Arai§,1     *School of Agricultural, Forest and Environmental Sciences, Clemson University, Clemson, SC, USA     §Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana–Champaign, Urbana, IL, USA
1 Corresponding author: E-mail: [e-mail] 

Abstract

Iodine is a trace halide found in the environment. A majority of global iodine budget resides in ocean while lithosphere and pedosphere contain the rest limiting the bioavailability of iodine in terrestrial environment. Iodine cycles involve the multivalence state chemical speciation at the air–water–sediment interfaces. The mobility and reactivity of these inorganic and organic iodine species are impacted by changes in physicochemical factors (e.g., pH and ionic strength), and macro- and micro-biological activities. Although iodine aqueous biogeochemistry has been extensively investigated in marine systems in the past, the partitioning mechanisms of iodine at the geomedia–water interface remained poorly understood. This chapter covers environmental soil chemistry of iodine and the impact to human and ecological health.

Keywords

Environmental chemistry; Iodine; Radioiodine; Remediation; Soil chemistry; Sorption; Toxicity

1. Introduction

Iodine belongs to the group of elements known as halogens. It is the least reactive of the halogens because of its large atomic size besides astatine, but can exist in several different chemical states in low-temperature geochemical environment namely iodide (I-), elemental iodine (I2), iodate IO3-), and periodate IO4-). This redox sensitive chemical speciation makes the iodine cycle in environment extremely complex. Among 37 isotopes, nonradioactive iodine-127 is the most stable and common isotope. Approximately 70% of global iodine is present in marine systems, and iodine in lithosphere and pedosphere is often limited, causing iodine deficiency in some parts of world. The two most common radioactive isotopes are iodine-129 (t1/2: 16millionyears) and iodine-131 (around 13days) (Downs and Adams, 1973; Grogan, 2012) that are anthropogenically produced through the fission of uranium and plutonium at nuclear reactors (Michel et al., 2005). Many attempted to understand the environmental chemistry of iodine in predicting the transport of radioiodine in subsurface environment and in developing the best remediation technologies. This chapter provides an overview of iodine environmental chemistry and toxicity as well as an extensive review of iodine sorption reaction in inorganic and organic soil components.

2. Indigenous Sources

As a trace nutrient, iodine is scarce in the environment. The concentrations of other halogens, fluorine, chlorine, and bromine greatly outnumber iodine concentrations. Iodine can be found naturally in minerals known as lautarite (Ca(IO3)2) and dietzeite (7Ca(IO3)28CaCrO4). These minerals occur naturally in the Caliche beds of Chile where they are mined and sold. The Caliche beds are the number one source of commercial iodine in the world (Downs and Adams, 1973). The various structures of halogen compounds are clear to scientists except for the structure of iodate. Chlorate and bromate crystallize with distorted lattices like those found in sodium chloride, but iodate’s structure is different than its halogen relatives. Studies have found that there are large intermolecular forces at play in between the oxygen and iodine. These interactions give the molecule a trigonally distorted octahedral area around the iodine. This configuration can also be seen in lithium iodate, ammonium iodate, and cerium iodate (Downs and Adams, 1973). The isotope of iodine in the environment that is most abundant naturally is iodine-127, but radioactive isotopes also occur naturally in the environment. Iodine-129 (129I) is produced naturally in the upper atmosphere when cosmic rays from the solar system hit the element xenon. Xenon degrades into this radioactive iodine and beta particles and gamma radiation (Edwards and Rey, 1969).

2.1. The Global Iodine Cycle

The iodine cycle on Earth involves many different geological and biological stages. The most common forms of iodine are found in the ocean as iodate, iodide, and elemental iodine. Ocean sediment accounts for 68% of the iodine in the natural environment while sedimentary rock consists of 27.7%. Table 2.1 provides the relative concentrations and percentages of iodine in the environment. Sedimentary rocks and igneous rocks have higher iodine concentrations compared to metamorphic rocks. Leaching of iodine from sedimentary rocks is high and researchers hypothesize that iodine can be lost from the interstitial spaces in the sediments (Christiansen and Carlsen, 1989).

Table 2.1

Distribution of global iodine budget in environment

Seawater

7.00×1010

0.81

2.66×1013

72.2

Oceanic sediment

5.90×1012

68.2

3.38×1011

0.92

Mafic oceanic crust

5.40×1010

0.62

4.20×1011

1.1

Sedimentary rocks (continent)

2.40×1012

27.7

4.40×1012

11.9

Metamorphic and magmatic rocks

2.30×1011

2.7

5.10×1012

13.8

Total

8.65×1012

100

3.69×1013

100

After Downs and Adams (1973).

Figure 2.1 The global iodine cycle. After Muramatsu et al. (2004).

Iodine species are readily emitted into the atmosphere from the ocean as methyl iodine (CH3I) and mix with precipitation in the atmosphere to fall back onto the soil as iodate and iodide. Researchers have also suggested that methyl iodide can be emitted from the soil solution via soil microbes and plant emissions (Amachi et al., 2001). Figure 2.1 shows the complete global iodine cycle (Muramatsu et al., 2004).

2.2. Marine Iodine

Iodine is also accumulated in the ocean by brown algae, mostly the Laminaria genus, red algae, Rhodophyta, and some sponges. Brown and red algae have a higher affinity to bioaccumulate iodine, but the reason why is not currently understood. Red and brown algae can have levels of iodine as high as 7000mgkg-1 of body mass compared to terrestrial plants such as mosses, deciduous trees, and grasses that only have around 3.5, 3.0, and 6.0mgkg-1 respectively (Fuge and Johnson, 1986). Marine animals also have a strong affinity for iodine although this affinity is not as high as the marine plants.

The distribution of iodide is varied at the ocean depth because iodide is at the highest concentrations in shallow waters near the continental shelf, but iodate concentrations dominate at deeper levels beneath the photic zone. The iodate concentration is at almost a constant level in these areas of the ocean (Wong, 1991). The higher levels of iodide in the shallow waters are attributed to the abundance of organisms near the continental shelf that are able to reduce iodate to iodide for use.

Marine algae have been shown to utilize inorganic iodine (I-) as an antioxidant. The process is complex, and Laminaria have been the first organism shown to use an inorganic product as an antioxidant. When Laminaria are submerged, the algae can use an enzyme called vanadium haloperoxidase to accumulate iodide from the seawater. When low tides occur and the algae are exposed to atmospheric oxygen, the accumulated iodide is released to scavenge reactive oxygen species (ROS) as well as hydrogen peroxide and ozone. The scavenging properties of iodide are involved in a cyclic reaction with hydrogen peroxide and are regenerated. The release of iodide by the Laminaria also releases some elemental iodine (I2) which goes into the coastal atmosphere, adding excess iodine to the atmosphere. Organoiodide complexes are also formed, and this process is thought to increase the concentration of organoiodide complexes (such as methyl iodide) in the marine environment (Küpper et al., 2008).

2.3. Iodine in Soils

There are...