Soil Pollution

From Monitoring to Remediation

Armando C. Duarte, Anabela Cachada, Teresa A.P. Rocha-Santos

• Publisher: Academic Press
• Year: 2017
• Topic: Biological Sciences
• eBook ISBN:
  9780128498729
• Subtopic: Botany
• Index: Biological Sciences

Soil Pollution: From Monitoring to Remediation provides comprehensive information on soil pollution, including causes, distribution, transport, the transformation and fate of pollutants in soil, and metabolite accumulation. The book covers organic, inorganic and nanoparticle pollutants and methodologies for their monitoring. Features a critical discussion on ecotoxicological and human effects of soil pollution, and strategies for soil protection and remediation. Meticulously organized, this is an ideal resource for students, researchers and professionals, providing up-to-date foundational content for those already familiar with the field. Chapters are highly accessible, offering an authoritative introduction for non-specialists and undergraduate students alike. - Highlights the relevance of soil pollution for a sustainable environment in chapters written by interdisciplinary expert academics and professionals from around the world - Includes cases studies of techniques used to monitor soil pollution - Includes a chapter on nanoparticles as soil pollutants - Offers comprehensive coverage of soil pollution including types and causes

Chapter 1

Soil and Pollution

An Introduction to the Main Issues

Anabela Cachada^{1, 2}, Teresa Rocha-Santos¹ and Armando C. Duarte¹, ¹CESAM and Department of Chemistry, University of Aveiro, Aveiro, Portugal, ²CIIMAR-UP, University of Porto, Matosinhos, Portugal

Abstract

Soil pollution has increased over the last decades and may pose a risk for human and ecological health. The main causes of soil pollution are associated with human activities, resulting in the accumulation of contaminants in soils that may reach levels of concern. Soil pollutants include a wide variety of contaminants (organic and inorganic chemicals), which can be derived from anthropogenic related activities, or naturally occurring in soil. Soil quality monitoring may be a hard task due to the lack of well-stated monitoring variables and indicators. On the other hand, the pressure on soil quality and the need for sustainability of soil fertility is ever increasing due to the issues related to the world’s population increase. Therefore, due to the combination of all the above-mentioned issues, the soil pollution becomes a hot topic. This chapter overviews the main aspects of soil contamination and demonstrates the main causes and types of soil pollution such as waste disposal, mining, agrochemicals, industry, and atmospheric deposition.

Keywords

Soil; pollution; contamination; types of pollutants; pollution sources

1.1 General Aspects of Soil

1.1.1 Soil as a vital resource

Soil can be defined as “the collection of natural bodies occupying parts of the Earth’s surface that is capable of supporting plant growth and that has properties resulting from the integrated effects of climate and living organisms acting upon parent material, as conditioned by topography, over periods of time” or, in a simplest way, as “a dynamic natural body composed of mineral and organic solids, gases, liquids, and living organisms” [1]. Thus, soil is a dynamic resource formed by an abiotic and a biotic component. The abiotic component includes different sized mineral particles (sand, silt, and clay) and the organic matter. The biotic components are living organisms, including populations of plants, animals, and microorganisms (bacteria and fungi), which differ in size, number, habits, life-cycles, food sources, etc. Thus, soil has biological, chemical, and physical properties, which are, in general, dynamic and respond to changes that may occur.

Soil communities, i.e., complex associations between a variety of organisms and the abiotic component, have an important role in soil formation, organic matter breakdown, nutrient cycling, and degradation of some contaminants. Indeed, soil performs several ecosystem services (key functions) which can be classified into four general categories: productivity and sustainability, environmental quality, biodiversity, and human wellbeing. Some of these functions are: food and biomass production; habitat for a variety of organisms; water regulation and filtering; organic matter breakdown and nutrients cycling; carbon storage; and human’s life support. In urban areas, it has also the function of supporting urban development, in addition to the esthetical and recreational functions in parks and gardens, which contribute to the preservation of biodiversity and play a distinct environmental role.

Soil is the interface between the other ecosystems: biosphere, atmosphere, and hydrosphere. Thus, soil has a direct influence on water and atmospheric quality, and consequently, on human and animal health. It is now recognized that soils are fundamental in the preservation of environmental quality at local, regional, and worldwide level. For example, its buffering capacity contributes to water quality, since the ability to act as a sink for contaminants can have an important role in controlling the negative impacts of pollution on other environmental compartments. For all these reasons, soil is considered a vital resource, and due to its slow formation, it can be considered nonrenewable. Moreover, it has impacts on environmental, economic, and cultural activities.

1.1.2 Soil quality

There are many definitions of soil quality [2], being one of the most used from Karlen et al. [3]: “the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation.” Therefore, soils quality is associated with soils’ fitness for a specific use, and thus other authors suggest the term soil health which is “the capacity of soil to function as a vital living system, within ecosystem and land-use boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and promote plant and animal health” [4]. Thus, the definition of soil quality, and thus of the soil services needed, is extremely related to the land use. For example, the soil services expected for natural areas, or agricultural soils, are much more than for commercial or industrial soils. Hence, the difficulty in establishing a definition is related to the variety of land uses, geographical conditions, types of soil, and lack of understanding of processes occurring within the soil.

If it’s difficult to define soil quality, then it is even more difficult to quantify it. The assessment of soil quality is normally performed through the identification and measurement of chemical, physical, and biological indicators. For example, carbon cycle and nitrogen cycle provide indices of the function of soil communities. However, there are several questions regarding this issue. For example, which and how many indicators should be measured? Thus, the assessment of soil quality may be somewhat subjective, but it is always related to the expected functions for that specific land use. In addition, assessing soil quality can be challenging due to its natural spatial heterogeneity.

1.1.3 Soil contamination as a major pressure

Soil functions may be strongly affected by different anthropogenic pressures such as inadequate agricultural and forestry practices, industrial activities, tourism, urban and industrial sprawl, and construction works. Thus, pressures are generated by the concentration of population and human activities, which will be even greater with the expected increase in world’s population. In mid-2013 the world population was of 7200,000,000, and it is expected to reach 9600,000,000 by 2050, and to rise to 10,900,000,000 by 2100 [5]. Developing countries will be the most important contributors to this increase, in particularly African countries, where the population is projected to increase from the current 1100,000,000 to 2400,000,000 by 2050. This is an issue of special concern due to the general lack of environmental policies in these countries.

The increase in population resulted in an increase of land-use intensity in recent decades, mostly driven by the need to feed and accommodate such a growing population. In addition, land uses have been changed at an incredible rate. The Corine Land Cover database shows significant changes in land use in Europe: between 1990 and 2000, at least 2.8% of Europe’s land was subject to a change in use [6]. By 2000, global cropland cover had reached 11% and pasture cover 24% [7]. Urban sprawl is another big issue, since by 2014, more people were living in urban areas (54%) than in rural areas [5]. Particularly in Europe, America, and Oceania, at least 70%–80% of the population lived in urban areas in 2014 [5,7]. In Africa and Asia, it is expected that by 2050, population living in urban areas will increase from 40% and 48% (in 2014), respectively, to 56% and 64% [5,7]. Indeed, megacities, typically located in developed regions, will also be increasingly found in developing countries. The number of these megacities tripled globally since 1990, being expected that by 2030, it will exist 41 global agglomerations housing more than 10 million inhabitants each [5,7].

According to the EU Soil Thematic Strategy, some of the major threats to soil in Europe are compaction, point and diffuse contamination, sealing, loss of soil organic matter, loss of soil biodiversity and habitats [6]. Other problems that may cause irreversible losses are soil erosion, salinization, floods, problems of slope stability, and acidification. Soil degradation due to contamination is an important issue around the world, and it was accelerated after the Industrial Revolution, through the large-scale use of fertilizers, expansion of industrial production, and the use of fossil fuels (Fig. 1.1). For example, the estimated number of potentially contaminated sites in EU-27 was approximately 4500,000,000 in 2013, with France, Germany, and The Netherlands leading the list [9]. Within these, around 490,000 sites were already identified and another 175,000 were remediated [9]. Regarding the United States, the number of sites on the Superfund National Priorities List (i.e., sites contaminated with complex hazardous substances that impact soil, groundwater, or surface water) was 1322 in 2014 [7]. Measures to deal with the contamination threat were taken in 1163 of these sites. In addition, 540,000 sites and 9300,000,000 ha of contaminated land have been cleaned up and back into use. In Canada, a total of 12,723 sites were identified has contaminated, and within these, 1699 were related to surface soil contamination. In Australia, the total number of contaminated sites is estimated at 80,000 [10]. In China, 19.4% of arable land does not reach national environmental quality standards, while for heavily polluted industrial sites this value is 36.3%, and for mining areas, it is 33.4% [11]. The total number of contaminated sites in China was estimated to be 500,000 [11].

Figure 1.1 History of growth in world population and environmental impact of Homo sapiens, indicated by its surrogates, per capita, and total human energy use. Reprinted from P.R. Ehrlich, P.M. Kareiva, G.C. Daily, Securing natural capital and expanding equity to rescale civilization, Nature 486 (2012) 68–73. Copyright (2012), with permission from Nature Publishing Group.

The numbers presented must be regarded with some caution, since some of these numbers are estimated and the identification of a site as contaminated will depend on the criteria and methodology applied, and it can be different from country to country, as it will be discussed in detail throughout the book. In the interim, the discussion will start by presenting some problems related to the definition soil contamination.

Some authorities restrict the term “contamination” to the consequences of human activity [12]. However, it may be difficult to determine the relative contribution of human versus natural processes. Others consider that a soil is contaminated when the levels of the chemical are above those that would normally occur. However, this raises the question: What is considered to be normal? For organic chemicals with an anthropogenic origin, such as pesticides or polychlorinated biphenyls (PCBs), any detectable levels are abnormal since they do not naturally occur in the environment. However, for others such as metals or polycyclic aromatic hydrocarbons (PAHs), which occur naturally, it is not so easy to define what a “normal level” is.

The European Commission defines contaminated sites as “sites which pose significant risk to human health and the environment” [6]. This leads us to the definition ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Short Biographies
• Preface
• Chapter 1. Soil and Pollution: An Introduction to the Main Issues
• Chapter 2. Distribution, Transport and Fate of Pollutants
• Chapter 3. Changes in Soil Ecosystem Structure and Functions Due to Soil Contamination
• Chapter 4. Pollutants Transformation and Metabolite Accumulation in Soils
• Chapter 5. Organic Pollutants in Soils
• Chapter 6. Inorganic Pollutants in Soils
• Chapter 7. Nanomaterials as Soil Pollutants
• Chapter 8. Ecotoxicological Effects and Risk Assessment of Pollutants
• Chapter 9. Human Health Risks and Soil Pollution
• Chapter 10. Strategies for Soil Protection and Remediation
• Index