Preface

Soil is a living, active and nonrenewable reserve and a crucial ecosystem component. Soil presents absorbing and emitting capabilities and is susceptible to contamination by a multiplicity of exogenous and endogenous sources. The study of soil resources and environmental problems is a broad, fascinating field that can take numerous dissimilar directions. Today, many anthropogenic ,as well as geogenic activities, are pressing in soil health, generating a strong ecological concern that requires an interdisciplinary approach involving both regulatory organizations and institutions for promptly resolving this situation. Soil contamination is very complex, and it is also often unsafe and harmful to all living species, including human beings specifically. It most frequently occurs from urban development, agricultural practices, military activities, mine tailings, metal industries, industrial accidents, deposits, or the transport of hazardous chemicals, among several other sources. Like pesticides, chlorinated compounds, and nitrogen, certain trace elements such as arsenic, lead, cadmium, copper, mercury, silver, or nickel pollutants can both be naturally present in the soil and be the consequence of human-made activities that nature cannot—or can only very slowly—decompose or degrade. These interventions can fragment, change, or even destroy soil habitats, significantly modifying the biota that lives in the soil. Whereas soil has a marked self-purification capacity, cleaning up contaminated sites is a long and expensive process. Nonetheless, environmental remediation is an important focus of the green economy, and a wide variety of conventional and emerging technologies must rapidly be employed to remove contaminants from polluted sites in order to restore the soil environment and protect the health of living species, including humans. Finally, ensuring long-term management as a final step is mandatory to evaluate the effectiveness of remedial strategies.

This single volume comprises fifteen high-quality chapters, organized into two sections, describing several issues related to soil contamination. The first section, *Contamination Sources*, comprises seven excellent and detailed chapters, starting with an update in the first chapter about the toxicity of heavy metals in several matrices including soil, water, air, and living organisms, presenting this problem as the main cause of environmental deterioration. This is followed by a second chapter providing information about the advantages and disadvantages of using microbial indices for heavy metal–contaminated and restored soils, highlighting the importance of understanding the mechanism(s) of responding to heavy metal stress and the methods available for the microbial diagnosis of heavy metal–contaminated soils. The third chapter presents an overview of the effect of pentachlorophenol pesticide contamination on microbial diversity, enzymatic activities, microbial biomass, and physicochemical soil characteristics, including a description of a bioremediation process. The fourth chapter summarizes the various sources of cadmium present in the environment and its toxic effects on plants and humans. It also includes a description of some bioremediation approaches to mitigate cadmium pollution in the environment. The fifth chapter provides information about how the prolonged use of high doses of fertilizers of

animal origin, such as swine manure, can result in the accumulation of metals and phosphorus in the soil. These accumulations potentially contaminate both the soil and surface water resources, mainly due to losses from runoff and subsurface leaching. The sixth chapter depicts one of the potential sources of soil contamination in agricultural production worldwide: the application of chemical fertilizers employed in excessive and disproportionate quantities. The chapter also summarizes the evidence regarding the employment of biofertilizers as an eco-friendly alternative for improving soil quality. Lastly, the seventh chapter of this section provides information about the application of fine materials from different rock types, such as basalt, trachyte, and volcanic pyroclastic fragments, in addition to sedimentary rocks like limestone and gneiss, as potential fertilizers on tropical soils from Cameroon. The chapter focuses on strategies for soil acidity management and the employment of this type of material as a potential source of phosphorus.

The second section of this book, *Remediation Technologies,* emphasizes integrated remediation approaches for detecting potentially biohazardous contaminants. The eighth chapter evaluates the phytoremediation potential of two ornamental plants, namely *Basella alba* and *Codiaeum variegatum*, in heavy metal–contaminated soils collected from several sites in Nigeria. The study reveals the ability of both plants to remove heavy metals, the heaviest concentration found to be accumulated in the roots rather than the shoots. The ninth chapter reviews the particularities of hexachlorocyclohexane (HCH)-contaminated soils and critically examines the bases and results of the technologies applied, paying special attention to physicochemical remediation processes. The tenth chapter aims to highlight the huge potential of several types of microorganisms being used as an attractive way of removing or remediating pollutants in landfill leachates, emphasizing their cost-effective and environmentally friendly benefits. The eleventh chapter discusses how to take phytoremediation approaches from a proven technology to accepted practice in an urban context. Additionally, it presents an overview of urban soil types following the application of phytoremediation to urban soils, focusing on inorganic and organic pollutants, to provide a frame of reference for the subsequent discussion on the better utilization of phytoremediation. The twelfth chapter aims to highlight the importance of the synergistic association between plants and microbes for the remediation of petroleum hydrocarbons as an effective tool for reclaiming the soil and the environment. The thirteenth chapter offers an interesting overview of the environmental role of nanophytoremediation in the elimination of the bioaccumulation of toxic nanoparticles. This innovative and encouraging technology has gained greater attention due to its current use in research on plants. This chapter describes several plant families that act in the biosynthesis of nanoparticles as well as the physiological process of nanophytoremediation. The fourteenth chapter provides an interesting overview of the role of soil management and conservation in enhancing microbial activity for soil ecological intensification as well as in buffering the soil to neutralize contaminants. The final, fifteenth chapter highlights the employment of green technologies like phytoremediation, biostimulation, and biodegradation for soil sustainable remediation, including information about nanotechnology in the degradation of contaminants.

The editors of *Soil Contamination - Threats and Sustainable Solutions* are enormously grateful to all the contributing scientists for sharing their knowledge

**V**

and insights in this interdisciplinary book project. They have made an extensive effort to arrange the information included in every chapter. The publication of this book is of high importance for researchers, scientists, and engineers with expertise in diverse fields of soil science, health, toxicology, policy making, and other disciplines, who can contribute and share their findings in order to take this area of

**Sonia Soloneski Ph.D. and Marcelo L. Larramendy Ph.D.**

School of Natural Sciences and Museum,

National University of La Plata,

La Plata, Argentina

study forward for future investigations.

and insights in this interdisciplinary book project. They have made an extensive effort to arrange the information included in every chapter. The publication of this book is of high importance for researchers, scientists, and engineers with expertise in diverse fields of soil science, health, toxicology, policy making, and other disciplines, who can contribute and share their findings in order to take this area of study forward for future investigations.

> **Sonia Soloneski Ph.D. and Marcelo L. Larramendy Ph.D.** School of Natural Sciences and Museum, National University of La Plata, La Plata, Argentina

**1**

Section 1

Contamination Sources

Section 1
