Inorganic Contaminants and Radionuclides

Inorganic Contaminants and Radionuclides is a single reference covering common inorganic contaminants in detail, including their distribution in the environment, challenges linked to management, geogenic sources, anthropogenic sources, exposure and effects, international agreements and legislation relating to the contaminant, remediation options and global case studies. In addition, the book provides summaries of contaminated sites and key details about contaminants to present a more comprehensive understanding and improve remediation and management practices. The book's clear, consistent organization makes it a valuable resource for researchers, students and practitioners working in environmental science, environmental management and environmental engineering.

One of the major constraints to assessing and remediating contaminated sites is the lack of awareness of the extent and severity of contaminated sites amongst the community, regulators, policymakers, industry operators, university graduates and environmental managers. This book helps to manage these constraints.

• Provides a one-stop reference on the nature and properties of inorganic contaminants, including a transdisciplinary approach to managing contaminated sites
• Includes global case studies covering contaminated site assessment, management and remediation
• Presents in-depth research and data on specific contaminants, with a separate chapter for each contaminant

• Language: English
• Publisher: Elsevier Science
• Release date: Oct 17, 2023
• ISBN: 9780323906852

Book preview

Chapter 1: Introduction to inorganic contaminants and radionuclides: Global issues and challenges

Ravi Naidua,b; Bhaba Biswasa,b    a Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, The University of Newcastle, Callaghan Campus, Callaghan, NSW, Australia

b crc for Contamination Assessment and Remediation of the Environment (crcCARE), ATC Building, University Drive, Callaghan, NSW, Australia

Abstract

Inorganic contaminants, including heavy metal, metalloid, and radionuclides, are a conventional and emerging group of pollutants. Therefore, much of their effect on human health and environmental quality is known, and lots are emerging. Overall, these groups of contaminants pose health risk once exposed via contact, dust inhalation, or food chain. This risk can be mortality or morbidity. Remediation technologies are available, but considering improvements like climate change adaptation is necessary. This chapter sweeps some insights into inorganic contaminants relating their definition, exposure, guideline values and remediation technologies. Specific members of these contaminant groups are extensively discussed in the subsequent chapters.

Keywords

Inorganic contaminants; Metals; Metalloids; Radionuclides; Risk; Remediation; Soil quality values

Chapter outline

1.Introduction: Extent and severity of global contamination

2.Problems and associated risks of inorganic contaminants and radionuclides

2.1Human health

2.2Environmental quality

3.Soil and groundwater quality criteria

4.Food security and climate change issues

5.Targeting remedial strategies

6.Challenges to remediating sites with inorganic contaminants and radionuclides

7.Concluding remarks

References

1: Introduction: Extent and severity of global contamination

The term inorganic contaminants refers to heavy metal(loid)s and certain nonmetal ions that are noted for their occurrence, exposure, and degree of health risk. Among the heavy metals and metalloids, lead (Pb), cadmium (Cd), arsenic (As), mercury (Hg), chromium (Cr), copper (Cu), manganese (Mn), iron (Fe), silver (Ag), vanadium (V), and zinc (Zn) are frequently reported in contaminated sites of concern (ATSDR, 2022). In addition to these, this book considers a selection of anionic contaminants. Each of these is discussed as a full chapter in this book. Radionuclides, which fall into a special category of contaminants in which the atom of elements undergoes radioactive decay, are discussed in Chapter 16.

This chapter addresses the global issues and challenges associated with chemical pollutants in general, in which inorganics and radionuclides play a part. The disposal of low-level radioactive waste containing different radionuclides, such as uranium (U), radium (Ra), radon (Rn), plutonium (Pu), americium (Am), rubidium (Rb), cesium (Cs), and strontium (Sr) has long been reported around the world, and is an issue of concern for humans and ecology (Payne et al., 2020).

For reading convenience, we use contaminant or contaminants to refer to both inorganic contaminants and radionuclides, unless otherwise specified. The sources of both types of contaminants are geogenic, that is, naturally originated and anthropogenic, emerging from the human intervention of natural deposits or manufacturing. For example, rock-weathered arsenic can migrate to groundwater which further enters the food chain via groundwater sourced irrigation. Therefore, the exposure to humans after its mineral weathering is a natural process in the first place (Rahman et al., 2009). Similarly, volcanic ash adds an excess amount of heavy metal(loid)s and sulfur where emission is high (Ma et al., 2019). In contrast, human activities, such as industrial production, mining, agriculture and livestock, energy, transport, and solid waste generation, are major polluters (FAO; UNEP, 2021). Since in these interventions, humans synthesize, utilize, and release chemicals, the necessity of assessing environmental contaminants and managing them is made even more urgent by the anthropogenic genesis of pollution (FAO; UNEP, 2021).

As the emission and distribution of contaminants have increased in recent decades, their risk assessment and management appear to be a key research theme (Feng et al., 2018; Karahan et al., 2020). Contaminated sites are rarely restricted to a single contaminant; however, because of remediation goals and requirements for regulatory reporting, single contaminants are often pinpointed. Published research and reports often under- or over-report contaminants, depending on the available analytical capabilities. Nevertheless, Fig. 1 shows a glimpse of the occurrence of several types of contaminants in polluted sites. Heavy metal(loid)s, as inorganic contaminants, are the most frequently occurring pollutants in these sites, followed by petroleum hydrocarbons as organic adulterants. Radioactive and explosive types of contaminants are reported the least, amounting to ∼4% of the total.

Fig. 1

Fig. 1 The occurrence of types of contaminants in contaminated sites—a search that provides only a glimpse into the representation in the literature. Search methodology for understanding contaminated sites: To understand the nature of the contaminated site, we used published article’s repository Scopus following searching criteria at our discretion: Year: 2016–Present (date: 10th June 2021), Search documents: contaminated site, Search within: Article title. A total of 196 documents appeared. We then exported these lists and their abstract and keywords into a bibliographic software Endnote. By a thorough reading of each document, we categorized contaminants detected from the real sites, exclusion of any experimental or artificially simulated contaminated site. We also considered only one from multiple lists of the same authors studying the compound from the same contaminated site. These resulted in 164 documents of various contaminated sites studied across the globe. Significance and limitations: Unavailability of many contaminated site data in the public domain limits this presentation. Only the research document’s title was searched for counting the report as the contaminated site. Contaminated sites used for collecting soil or other samples without wording in the research title might have been excluded. It is also possible that some contaminants such as heavy metal(loid)s are analytically convenient to measure than many emerging contaminants; therefore, the occurrence of such well-studied contaminant might be skewed toward a greater percentage. Despite this, the listed 164 documents summarized the diverse contaminated profile among contaminated sites.

2: Problems and associated risks of inorganic contaminants and radionuclides

2.1: Human health

The effects of contaminants on human health are often linked to (i) the specificity of the contaminants and (ii) the human exposure (pathways and duration) to them. While this book touches on specific heavy metal(loid)s’ effects on health, a general picture of deteriorated human health caused by overall contaminants is presented (Balali-Mood et al., 2021).

2.1.1: Health deterioration from heavy metal(loid)s

Short-term exposure with high concentration, even at a single dose, may be fatal to humans, whereas long-term exposure with low concentrations may induce the development of different diseases or disorders. These diseases include gastrointestinal and kidney dysfunction, nervous system disorders, skin lesions, vascular injury, damage to liver and blood, birth defects, and immune system dysfunction, and may eventually cause cancer. Humans can be exposed to inorganic pollutants and radionuclides via different natural and anthropogenic sources, including occupational, environmental, dietary, and medicinal catalysts. Fig. 2 represents a schematic pathway of heavy metal toxicity to humans. In simple terms, these contaminants in the human body accelerate the generation of free radicals, which damage both enzymatic and nonenzymatic immune systems. They affect lipid and protein synthesis as well as cell division and DNA synthesis. They also interfere in the activation of regulatory molecules and neurotransmitter mechanisms. This irreversible cell damage results in carcinogenicity in humans and causing other acute and chronic diseases (Mitra et al., 2022).

Fig. 2

Fig. 2 The human health effects and mechanisms of toxicity caused by heavy metal(loid)s. Adapted after Mitra, S., Chakraborty, A.J., Tareq, A.M., Emran, T.B., Nainu, F., Khusro, A., Idris, A.M., Khandaker, M.U., Osman, H., Alhumaydhi, F.A., Simal-Gandara, J., 2022. Impact of heavy metals on the environment and human health: Novel therapeutic insights to counter the toxicity. J. King Saud Univ. Sci. 34, 101865.

2.1.2: Health deterioration by radioactive contaminants

Radionuclides may enter the human body through air, water, the food chain, or other environmental matrixes, affecting human health, particularly at higher radiation doses. Karahan et al. (2020) reported that radioactivity may cause kidney disorders, cardiovascular disease, hypertension, or stroke; mortality is affected to some degree, particularly at high doses. A large release of radionuclides causes several health-related complications, as reported by Lake et al. (2008). Although the severe health effects of chronic (long-term) exposure of humans to radionuclides are well understood, the acute (short-term) noncarcinogenic health effects are not yet clear. Chronic inhalation exposure to uranium generates chronic lung disease and tumors in the lymphatic and hematopoietic tissue, and eventually causes lung cancer. Radon exposure has been linked to complications such as leukopenia, necrosis of the jaw, and anemia. Inhalation exposure to radium results in lung cancer in humans, and oral exposure provokes bone, head, and nasal passage tumors. Radionuclides in drinking water may also cause stomach cancer (Auvinen et al., 2005; Nayak et al., 2022).

2.2: Environmental quality

Environmental quality is deteriorating due to increased exposure to inorganic contaminants, and the situation has worsened in recent years. Inorganic contaminants in solid, semisolid, and liquid waste are discharged into soil and water, while gas or dust contaminants are emitted into the environment through wet and dry deposition. Inorganic contaminants are pH sensitive, and their mobility and exposure are likely to be increased under an acidic environment (in particular metals). The presence of these pollutants in soils and water can change microbial diversity and metabolic activities of plants, microbes, and biota, affecting their health (Olobatoke and Mathuthu, 2015; Oves et al., 2012).

3: Soil and groundwater quality criteria

The occurrence, contamination, severity of toxicity, and contaminant exposure to receptors are often determined by the degree of threshold guidelines recommended by regulation bodies. However, the guidelines differ from site to site, for example, agriculture soil vs. industrial area or environmental medium, such as soil vs. water. Further, assessment and guideline values for determining these quality criteria can vary among jurisdictions (Provoost et al., 2006).

Soil and water quality criteria are considered during the detailed site investigation (DSI) that involves sampling environmental components like soil, water, sediment, and in some cases, biological receptors, such as plants and biota. Tables 1 and 2 compare various jurisdictions and provide an overall picture of soil and water quality criteria for priority inorganic contaminants and radionuclides.

Table 1

a Guidelines for contaminated soil by Queensland Health (2020).

Table 2

In the case of groundwater quality, the guideline values are often applied relative to its point of expressions, such as drinking water, surface water, and irrigation water (Australian Government, 2013). Table 2 presents a short list of selective heavy metal(loid)s and radionuclides and the maximum permission limit in drinking water.

4: Food security and climate change issues

Food security and safety compromised through site contamination by inorganic contaminants and radionuclides have been reported in many cases around the world; of particular concern is toxicity as a result of soil-to-food links (Fig. 3). For example, a contaminated site can pass its mobile and residual contaminants to exposed crops and livestock. This may pose direct toxicity to the food chain linked to those crops and animals (Zhong et al., 2015). Moreover, an increasing number of registered or unregistered contaminated sites may contribute to the low yield of crops or natural vegetation (Cameron et al., 2015; Tóth et al., 2016). This could be a direct effect of contaminants that damage the seed or germination, or of once fertile land that cannot contribute to food production simply being abandoned (Fig. 3).

Fig. 3

Fig. 3 Food security and safety can be compromised by exposure to chemical pollutants. Schema modified and reprinted with permission from Naidu, R., Biswas, B., Willett, I.R., Cribb, J., Kumar Singh, B., Paul Nathanail, C., Coulon, F., Semple, K.T., Jones, K.C., Barclay, A., Aitken, R.J., 2021. Chemical pollution: a growing peril and potential catastrophic risk to humanity. Environ. Int. 156, 106616.

The concern regarding food security and safety is revisited by managers, while soil properties and the biogeochemical process are deemed to be linked to events caused by climate change (Biswas et al., 2018). There is growing evidence regarding the alteration of soil properties caused by climate change-related events. For example, Gmitrowicz-Iwan et al. (2020) reported that drought could assist in the conversion of river sediment to soil, leading to more heavy metals in the ecosystem. Using a pollutant transport model, Jarsjö et al. (2020) also projected that a model increase in groundwater level would increase metal's mobility in topsoils.

5: Targeting remedial strategies

Remedial strategies depend on many factors, including the outcome of risk assessment, target contaminants to be remediated, cost and duration, regulations and political will, and available clean-up techniques (Yoon et al., 2021). In terms of technology, an overview of the main soil remediation techniques and their modus operandi is presented in Table 3 (Rai et al., 2019; Sanderson et al., 2023; Yoon et al., 2021; US-EPA, 2023).

Table 3

The Australian National Remediation Framework (NRF) developed a platform that can assist remediation practitioners to navigate a decision tree based on the effectiveness and feasibility of technologies applicable to a particular group of contaminants (CRC-CARE, 2019). For example, the first stage involves understanding the regulations and remediation goals. This leads to the remediation options, technology guides, cost-benefit analysis, and validation of the works.

6: Challenges to remediating sites with inorganic contaminants and radionuclides

Despite the significant attention that has been given to the development of remediation technology for contaminated sites in the past decade, there are serious challenges within and surrounding it. Among these, the major challenges are (i) the gap between the knowledge gained by laboratory-based studies and that experienced at the sites, (ii) political will, and (iii) corruption, disputes, and insufficient funding for site clean-up projects.

Among these three challenges, the knowledge gap regarding specific contamination is the most critical one from a scientific point of view. Several inorganic contaminants and radionuclides exhibit separate physicochemical phenomena and can change under a wide range of environmental factors. Multiple contaminants co-exist, which is another challenge to address when dealing with the targeted contaminant. Environmental chemistry, fate, and the behavior of some inorganic contaminants and radionuclides are still not clear, which affects the development of effective remediation technology.

7: Concluding remarks

With nearly 10 million potentially contaminated sites and inorganic contaminants associated with the majority of them, minimizing their exposure risks is crucial for the sustainability of our fragile natural ecosystem and humanity. Contaminants in soil and groundwater presents significant challenges for clean-up technologies that are cost-effective and sustainable. This includes understanding the emerging contaminants, mixed groups of contaminants and the lack of resources in developing countries. The book series the Global Compendium of Contaminated Sites is expected to bring to the fore the nature of such contaminants with Volume 1 focusing on inorganic contaminants and radionuclides. The environmental remediation of contamination with minimal disturbance of its origin is the most challenging work, but it is essential for sustainable environmental protection.

References

ATSDR. The ATSDR 2022 Substance Priority List.https://www.atsdr.cdc.gov/spl/index.html. 2022.

Australian Government. Guidelines for Groundwater Quality Protection in Australia: National Water Quality Management Strategy. Canberra: Department of Agriculture and Water Resources; 2013.86.

Auvinen A., Salonen L., Pekkanen J., Pukkala E., Ilus T., Kurttio P. Radon and other natural radionuclides in drinking water and risk of stomach cancer: A case-cohort study in Finland. Int. J. Cancer. 2005;114:109–113.

Balali-Mood M., Naseri K., Tahergorabi Z., Khazdair M.R., Sadeghi M. Toxic mechanisms of five heavy metals: mercury, lead, chromium, cadmium, and arsenic. Front. Pharmacol. 2021;12:643972.

Biswas B., Qi F., Biswas J.K., Wijayawardena A., Khan M.A., Naidu R. The fate of chemical pollutants with soil properties and processes in the climate change paradigm—a review. Soil Syst. 2018;2:51.

Cameron D., Osborne C., Horton P., Sinclair M. A sustainable model for intensive agriculture. In: Grantham Centre Briefing Note. Sheffield, UK: Grantham Centre for Sustainable Futures; 2015:4.

CRC-CARE. National Remediation Framework. 2019 CRC for Contamination Assessment and Remediation of the Environment.

FAOUNEP. Global Assessment of Soil Pollution—Summary for Policy Makers. Rome, Italy: FAO; UNEP; 2021.84.

Feng M., Zhang P., Zhou H.-C., Sharma V.K. Water-stable metal-organic frameworks for aqueous removal of heavy metals and radionuclides: a review. Chemosphere. 2018;209:783–800.

Gmitrowicz-Iwan J., Ligęza S., Pranagal J., Kołodziej B., Smal H. Can climate change transform non-toxic sediments into toxic soils?. Sci. Total Environ. 2020;747:141201.

Jarsjö J., Andersson-Sköld Y., Fröberg M., Pietroń J., Borgström R., Löv Å., Kleja D.B. Projecting impacts of climate change on metal mobilization at contaminated sites: controls by the groundwater level. Sci. Total Environ. 2020;712:135560. doi:10.1016/j.scitotenv.2019.135560.

Karahan G., Kapdan E., Bingoldag N., Taskin H., Bassari A., Atayoglu A. Environmental health risk assessment due to radionuclides and metal (loid) s for Igdir province in Anatolia, near the Metsamor nuclear power plant. Int. J. Rad. Res. 2020;18:863–874.

Lake J.V., Bock G.R., Cardew G. Health Impacts of Large Releases of Radionuclides. John Wiley & Sons; 2008.

Ma Q., Han L., Zhang J., Zhang Y., Lang Q., Li F., Han A., Bao Y., Li K., Alu S. Environmental risk assessment of metals in the volcanic soil of Changbai Mountain. Int. J. Environ. Res. Public Health. 2019. ;16(11):2047. https://doi.org/10.3390/ijerph16112047.

Mitra S., Chakraborty A.J., Tareq A.M., Emran T.B., Nainu F., Khusro A., Idris A.M., Khandaker M.U., Osman H., Alhumaydhi F.A., Simal-Gandara J. Impact of heavy metals on the environment and human health: Novel therapeutic insights to counter the toxicity. J. King Saud Univ. - Sci. 2022;34:101865.

Nayak T., Basak S., Deb A., Dhal P.K. A systematic review on groundwater radon distribution with human health consequences and probable mitigation strategy. J. Environ. Radioact. 2022;247:106852. doi:10.1016/j.jenvrad.2022.106852.

Olobatoke R.Y., Mathuthu M. Radionuclide exposure in animals and the public health implications. Turkish J. Veter. Anim. Sci. 2015;39:381–388.

Oves M., Khan M.S., Zaidi A., Ahmad E. Soil contamination, nutritive value, and human health risk assessment of heavy metals: an overview. Toxicity Heavy Metals Legum. Bioremed. 2012;1–27.

Payne T.E., Harrison J.J., Cendon D.I., Comarmond M.J., Hankin S., Hughes C.E., Johansen M.P., Kinsela A., Shahin L.M., Silitonga A. Radionuclide distributions and migration pathways at a legacy trench disposal site. J. Environ. Radioact. 2020;211:106081.

Provoost J., Cornelis C., Swartjes F. Comparison of soil clean-up standards for trace elements between countries: why do they differ?. J. Soil. Sediment. 2006;6:173–181.

Queensland Health. Land Contaminated by Radioactive Material—A Guide to Assessment, Management and Remediation. State of Queensland: Queensland Health; 2020.69.

Rahman M.M., Naidu R., Bhattacharya P. Arsenic contamination in groundwater in the Southeast Asia region. Environ. Geochem. Health. 2009;31:9–21.

Rai P.K., Lee S.S., Zhang M., Tsang Y.F., Kim K.-H. Heavy metals in food crops: Health risks, fate, mechanisms, and management. Environ. Int. 2019;125:365–385.

Sanderson P., Bahar M., Biswas B., Naidu R. Remediation of metals and organic contaminants in soil. In: Goss M., Oliver M., eds. Encyclopedia of Soils in the Environment. second ed. Elsevier; 2023. In press https://doi.org/10.1016/B978-0-12-822974-3.00247-0.

Tóth G., Hermann T., Da Silva M.R., Montanarella L. Heavy metals in agricultural soils of the European Union with implications for food safety. Environ. Int. 2016;88:299–309.

US-EPA. Remediation Technologies for Cleaning Up Contaminated Sites.https://www.epa.gov/remedytech/remediation-technologies-cleaning-contaminated-sites. 2023.

WHO. Guidelines for Drinking-Water Quality: Fourth Edition Incorporating the First and Second Addenda. Geneva: World Health Organization; 2022 Licence: CC BY-NC-SA 3.0 IGO.

Yoon I.-H., Park C.W., Kim I., Yang H.-M., Kim S.-M., Kim J.-H. Characteristic and remediation of radioactive soil in nuclear facility sites: a critical review. Environ. Sci. Pollut. Res. 2021;28:67990–68005.

Zhong M.-S., Jiang L., Han D., Xia T.-X., Yao J.-J., Jia X.-Y., Peng C. Cadmium exposure via diet and its implication on the derivation of health-based soil screening values in China. J. Expo. Sci. Environ. Epidemiol. 2015;25:433.

Section 1

Metal(loid) contaminants

Chapter 2: Arsenic

Md. Aminur Rahmana,b; Amal Kanti Deba,b; Sepide Abbasia,b; A.S.M. Fazle Baria,b; Kh Ashraf Uz Zamana,b; Mohammad Mahmudur Rahmana,b; Prosun Bhattacharyac; Ravi Naidua,b    a Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, The University of Newcastle, Callaghan Campus, Callaghan, NSW, Australia

b crc for Contamination Assessment and Remediation of the Environment (crcCARE), ATC Building, University Drive, Callaghan, NSW, Australia

c KTH-International Groundwater Arsenic Research Group, Department of Sustainable Development, Environmental Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden

Abstract

Arsenic (As) is a poisonous metalloid and recognized as a Group I human carcinogen by the International Agency for Research on Cancer (IARC). Arsenic often exists in groundwater and surface water, oceanic and inland deposits, rocks, soils, and biota at variable concentrations. Over the last few decades, As contamination has been augmented noticeably due to both natural and anthropogenic sources. Arsenic contamination in groundwater is currently a major global environmental catastrophe, which affects over 200 million people in 107 countries and causes various health complications including cancer. Therefore, updated information regarding the sources, chemical form, bioavailability, extent and severity, food safety and regulation, remediation, and management of As is essential. In this chapter, we accumulated the detailed sources of As, including point and diffuse sources, various inorganic and organic As species, and their toxicity in the environment. Moreover, the fate of As in the environment, economic implications of As-contaminated food and food products, and the bioavailability and bio-accessibility of As in environmental media are also briefly summarized. Remediation technologies for As-contaminated soil with the latest case study and regulatory limits of As in soil are also presented in this chapter. Overall, this chapter incorporates the past and contemporary knowledge of As, which will be useful for better management of As in the near future.

Keywords

Arsenic; Toxicity; Risks; Human health; Fate and management

Chapter outline

1.Introduction

2.Global sources of arsenic contamination

2.1Geogenic sources

2.2Anthropogenic sources

3.Point and diffuse sources of As pollution

4.Fate of As in the environment

5.Economic implications of As-contaminated food and food products

6.Bioavailability and bioaccessibility of As

7.Technologies for remediating As-contaminated soil

7.1Physical technologies

7.2Chemical technologies

7.3Biological technologies

7.4Case study

8.Regulatory limits of As in soil

9.Conclusion

References

1: Introduction

Arsenic (As) is a toxic metalloid with a bright silver-gray and brittle-crystalline appearance and documented as a Group 1 human carcinogen (International Agency for Research on Cancer, 2004). Arsenic comprises pervasive metal(loid)s broadly spread throughout the earth’s crust and can be released into the environment by natural processes, including water-rock interfaces, soil overspill, wild-land fires, biological activity, volcanic eruption, and the migration and transformation of Sb compounds (Smedley and Kinniburgh, 2002). Likewise, As biogeochemistry is greatly influenced by anthropogenic activities involving the burning of fossil fuels, mining, ore smelting, manufacturing of semiconductors (as a doping agent), coal combustion, wood preservatives, disposal of tannery wastes, well drilling, and consumption of some agricultural pesticides, insecticides, and herbicides (Mandal and Suzuki, 2002; Li et al., 2018). People’s exposure to As occurs primarily through a number of pathways, including potable water, foodstuffs, drinks, soil, dust inhalation, and particulates in the atmosphere (Naidu and Bhattacharya, 2009; Antoniadis et al., 2019; Rahman et al., 2021). In this chapter, we review the point and diffuse sources of As, its destiny in the environment, the bioaccessibility and bioavailability of As, and remediation options for better management of As-contaminated sites.

Arsenic is frequently available in natural groundwater aquifers, oceanic and inland deposits, rocks, soils, and biota at a range of different concentrations (Stanger et al., 2005; Mondal et al., 2006; Luu et al., 2009; Osuna-Martínez et al., 2020). The mean value of As in the globe’s crust is around 5 μg/g but differs according to geological conditions and anthropogenic influences. In the last few decades, adulteration by As has risen significantly due to both natural and anthropogenic contributions (Smedley and Kinniburgh, 2002; Li et al., 2018). Arsenic can severely pollute mine stakeouts, as much as the 0.9–62 g/kg range (Kim et al., 2002). These places are considered to be the main origins of As in groundwater and surface water (Mohan and Pittman Jr., 2007).

Typical As concentrations from 0.5 to 2.5 mg/L in polluted groundwater and more than 100 mg/L in industrial wastewater (Choong et al., 2007; Wang et al., 2015a) are observed. Millions of tube wells are polluted by high As levels (4.8 mg/L); these wells, however, are sometimes the sole drinking water source in many developing countries (Rasheed et al., 2016; Waqas et al., 2017; Hasan et al., 2019). Subsequently, As adulteration in groundwater and surface water is now a major global ecological catastrophe that affects more than 200 million people in 105 countries, and they suffer from prolonged diseases (Naidu et al., 2006; Herath et al., 2016; Chakraborti et al., 2018).

The existence of As in a free-state form in nature is unusual due to the outermost electrons occupying the crystalline structure and being fixed by covalent bonds. It usually combines with iron, oxygen, and sulfur. The atomic mass and elemental crystal electronic configuration of As are 74.9216 u ± 0.00002 u and [Ar] 3d104s24p3 (atomic number 33), respectively. Arsenic belongs to Group VA elements with nitrogen, phosphorous, antimony, and bismuth in the periodic table. The main three allotropes of As include yellow, gray, and black, but only the gray form has a metallic appearance with a specific gravity of 5.73 and is important to various industries. The boiling and melting points of As are 603°C and 817°C (28 atm), respectively; however, the sublimation point is 613°C. Arsenic has isotopes in the As⁶³ to As⁹² range where As⁷⁵ exists in a stable form. Although As is the world’s 54th natural abundant element, natural mineralization processes mean that the level of As can increase in some regions of the world. Arsenic is present in about 245 minerals and is incorporated with other metals in sulfidic ores, for instance lead, gold, copper, gold, and zinc (Nordstrom, 2002; Oremland and Stolz, 2003; Cullen, 2008).

Arsenic existing in various oxidation states (Smedley and Kinniburgh, 2002) occurs either as inorganic or organic types in aquatic and terrestrial ecosystems (Wu et al., 2016; Kumarathilaka et al., 2018). In aqueous media, inorganic As (iAs) is dominant and uniquely subtle to mobilization at the pH range 6.5–8.5 under both oxidative and reductive scenarios (Smedley and Kinniburgh, 2005; Zhang et al., 2016). The two iAs species in natural water are arsenite [ Equation /As(III)] and arsenate [ Equation /As(V)]. As(III) includes As(OH)3, Equation , AsO2OH²−, and Equation , while As(V) subsists as Equation , Equation , and Equation at pH 3–11; their respective pKa values are 2.35, 6.97, and 11.53 (Abbas et al., 2018; Kumarathilaka et al., 2018). Around 50 different As species are thought to exist (Reimer et al., 2010) in the environment. In solution form, iAs speciation is strictly controlled by the pH, adsorption, and redox potential (Eh).

The methyl derivatives of As may be connected with microbial action in natural systems detected in minute amounts due to biological methylation (Wallschläger and London, 2008; Jia et al., 2013; Hu et al., 2021). Organic species of As (oAs) are arsenobetaine (AsB), arsenocholine (AsC), dimethylarsinate (DMA(V)), dimethyl arsenite (DMA(III)), monomethyl arsenate (MMA(V)), monomethyl arsenite (MMA(III)), tetramethylarsonium ion (TMA+), trimethylarsine oxide (TMAO), and arsenosugars (Mestrot et al., 2011a; Jia et al., 2013; Zhai et al., 2017). These species are entirely biotically arbitrated, either in microorganisms (fungi and bacteria) or higher florae (i.e., aquatic plants, most likely originating from the rhizosphere, via the actions of methylating microbes). Examples here include aquatic animals, echinoderms, fish, kelp, bivalves, mollusks, seaweed, shellfish, coelenterates, porifera, and blue mussels (Craig and Jenkins, 2004; Foster et al., 2005; Navas-Acien et al., 2011; Jia et al., 2013; Zhao et al., 2013; Molin et al., 2015; Xu et al., 2016; Taylor et al., 2017). Arsenolipid, which is a lipid-soluble As compound existing mainly in marine organisms, can be as much as 16 mg As/kg fish oil (Taleshi et al., 2010; Sele et al., 2012; Lischka et al., 2013; Molin et al., 2015). AsB is the leading species of As found in sea animals, mostly in finfish and shellfish (Edmonds and Francesconi, 2003; Takeuchi et al., 2005). Meanwhile, large amounts of dimethylarsinoriboses are commonly detected in sea macroalgae in zooplankton (Tukai et al., 2002) and oceanic herbivores (Kirby and Maher, 2002; Kirby et al., 2002).

The release of As from unsaturated zones into groundwater is mediated by a number of physicochemical and biological processes; of principle importance here As sorption behavior and compaction of clayey aquitards (Wang and Mulligan, 2006a; Xue et al., 2019; Mihajlov et al., 2020; Xiao et al., 2020). The destiny and movement of As species in the environment are linked with natural organic matter (NOM) in numerous ways (Wang and Mulligan, 2006a; Langner et al., 2013). Arsenic leakage in the groundwater is made possible by NOM boosting the discharge of As from sediments and soils into the soil solution (van Geen et al., 2003). Furthermore, NOM may function as binding agents, which assists in curtailing As mobility (Langner et al., 2013).

The toxicity of As is measured by several factors such as valence states (+3 and +5), pH, physical state, chemical form, dissolved organic carbon or organic matter, redox potential (Eh), microbial and algal species, as well as its solubility (Mandal and Suzuki, 2002; Smedley, 2008; Hussain et al., 2021). Additionally, immobilization of As in aquifers can be caused by Fe and Mn oxyhydroxides (redox-sensitive metal oxides) (Chen et al., 2016; Anawar et al., 2018; Amirnia et al., 2019; Fakhreddine et al., 2020). Microbes/algae can reduce the toxicity of As by first transforming As(V) into a less toxic methylated species or, second, elevating it through the conversion of arsine (AsH3), which is a poisonous form of As (Bhattacharya et al., 2013; Jia et al., 2015; Wang et al., 2015b; Upadhyay et al., 2018). Organoarsenicals are considered to be less toxic, and only AsB is considered to be nontoxic due to the as yet unestablished LD50 value (Kaise et al., 1985; Nearing et al., 2014).

As(III) overwhelms the functions of more than 200 enzymes after binding with thiol or sulfhydryl groups and can bind to reduced cysteines in peptides and proteins (Ngu and Stillman, 2006; Shen et al., 2013), thus distressing several organs such as the kidneys, liver, or bladder (Rehman and Naranmandura, 2012; Saha et al., 2016). As(V) can be substituted with phosphorous, which affects various biochemical pathways (Hughes, 2002; Duncan et al., 2014; Upadhyay et al., 2018). Thioredoxin reductase/NADPH plays an important role in biochemical pathways. Over many years, numerous studies suggested that the oxidative process plays a vital function in As-induced mutagenesis and carcinogenesis (Hughes and Kitchin, 2006; Kitchin and Wallace, 2008; Sinha and Roy, 2011; Inesta-Vaquera et al., 2021). It does this by developing reactive oxygen species (ROS) including superoxide anion (O2), hydroxyl radical (•OH), hydrogen peroxide (H2O2), and reactive nitrogen species (RNS) (nitric oxide—NO) (Wiseman and Halliwell, 1996; Flora et al., 2008; Obinaju, 2009; Jomova et al., 2011).

According to Vega et al. (2001), the toxicity level of As increases in the following order: AsV > MMAV > DMAV > DMAIII > monomethyl arsine oxide (MMAOIII) > AsIII. However, As(III) forms are the most toxic, followed by As(V) and then organic forms such as DMA(V) and MMA(V) (Jain and Ali, 2000; Wang and Mulligan, 2006b). This is despite the intermediate forms MMA(III) and DMA(III) being more toxic than even arsenate and arsenite (Styblo and Thomas, 2001; Wang et al., 2015b). As(III) is almost 70 times more toxic than organic As and 10 times more toxic than As(V) (Jain and Ali, 2000; Van Herreweghe et al., 2003; Larios et al., 2012). Arsenic is well recognized as a carcinogen due to its genotoxic and mutagenic activity; through clastogenesis, it generates sister chromatid exchange and chromosomal breakage (Samuel et al., 2011; Singh et al., 2011; Maiti et al., 2012; Hsu et al., 2015; Son et al., 2015).

Each year, high background As concentrations, as much as 250,000 mg/kg, are found in new locations (Mahimairaja et al., 2005; Mikutta et al., 2014). In addition, volcanoes’ release of As is calculated at 3000 tonnes/year, and microorganisms’ release of As is 20,000 tonnes/year through volatile methylarsines. However, human activities are much more responsible for 80,000 tonnes/year of As released by the burning of fossil fuels. It is now recognized that at least 200 million people in 105 countries are suffering from different As-related health consequences via the consumption of As-containing water at levels above the WHO’s guideline value of 10 μg/L (Bhowmick et al., 2018). However, this guideline value may not offer actually much protection since studies have documented an association between exposure at 10 μg/L and cardiovascular diseases (Fendorf et al., 2010; Xu et al., 2020). Therefore, As-contaminated sites/sources should pay greater attention to establishing a safe and effective treatment by remediating a range of techniques so that it is below 10 μg/L for people’s safety.

2: Global sources of arsenic contamination

As originates from both geogenic or natural and anthropogenic sources in the global environment. Arsenic (As) is ranked 20th in terms of richness on the earth, 14th in seawater, and 12th in the human body (Woolson, 1975). It occurs in both solid and liquid states with metallic and nonmetallic features and is not available as a native state in the environment. Generally, As is found in all rocks, soils, waters, air, and living species. Essentially, As is generated as a by-product of smelting copper (Cu), gold (Au), lead (Pb), mercury (Hg), zinc (Zn), and other ores (Nriagu and Pacyna, 1988). The global supplies of As are nearly 1.5–3 mg/kg (Mandal and Suzuki, 2002).

2.1: Geogenic sources

As is distributed abundantly in the earth’s crust, sediments, soil, air, water, and biological forms of life.

2.1.1: Occurrence and distribution

Among the extensive widespread forms of As that occur in different minerals, it generally exists as arsenides or sulfides of iron (Fe), Cu, Pb, Au, and silver (Ag). The two common forms of As sulfides are realgar (AS4S4) and orpiment (As2S3), in which As exists in a reduced form. The oxidized form of As is found in the mineral arsenolite (As2O3). The other naturally occurring minerals that contain As include arsenopyrite (FeAsS), loellingite (FeAS2), glaucodot [(Co,Fe)AsS], enargite (Cu3AsS4), niccolite (NiAS), rammelsbergite (NiAs2), gersdorffite (NiAsS), saffordite (CoAs), cobaltite (CoAsS), etc.

2.1.2: Earth’s crust

The average amount of As located in the inland crust is 1–2 mg/kg. Although As content in most rocks varies from 0.5 to 2.5 mg/kg (Kabata-Pendias and Pendias, 1984), more concentrations were found in finer grained argillaceous sediments and phosphorates. Some reducing marine sediments may contain nearly 3000 mg/kg of As, which can also coprecipitate with sulfides and iron hydroxides in sedimentary rocks. Arsenic geogenically occurs in more than 200 types of mineral forms, of which around 605 are arsenates, 20% are sulfides and sulfosalts, and the remaining 20% comprises elemental arsenic, arsenides, arsenites, oxides, and silicate (Rogers et al., 1969). Arsenic is found in different metalliferous deposits in its best recoverable form. These deposits belong to several groups such as enargite-bearing Cu-Zn-Pb deposits, arsenical pyritic Cu deposits, native Ag and Ni-Co arsenide-bearing deposits, arsenical Au deposits, arsenic sulfide and arsenic sulfide Au deposits, arsenical tin deposits, arsenical quartz, Ag, and Pb-Zn deposits. Consequently, many countries are affected by As contamination due to natural erosion of the minerals mentioned earlier (Fig. 1).

Fig. 1

Fig. 1 Map exhibiting the currently known 32 countries that are the major naturally arsenic-contaminated areas of the world ( Mukherjee et al., 2008).

2.1.3: Soil

Soil As concentration is higher than rocks. Arsenic content in the soil depends on some factors, particularly climate, organic and inorganic matter, and soil redox conditions. The amount of As in the soil also varies significantly according to geographic locations, and the concentration range varies from 0.1 to 40 mg/kg, 1 to 50 mg/kg, and a mean of 5 mg/kg (Mandal and Suzuki, 2002). Generally, the level of As in sediments is less than 10 mg/kg dry weight, and worldwide it varies substantially. Arsenic may immobilize in the form of salts of arsenic and arsenous acids. In soils, the nature of As depends largely on the types and amount of adsorbing components in soil pH, and redox potential. Although the inorganic form of As (iAs) in soils is predominant, it can also exist in organic form (oAs) by binding organic materials in soils. iAs are more toxic than oAs species, and—under oxidizing conditions and aerobic environments—stable iAs(V) species are intensely adsorbed by organic matter, clay, iron, and manganese oxides/hydroxides. Conversely, inorganic arsenite [iAs(III)] is a major arsenic compound under reducing conditions. iAs(III) can be methylated by microorganisms to produce mono-, di-, and tri-methylarsonic acid (MMA, DMA, and TMA). The biomethylation of As also occurs in the soil-water and sediment-water interfaces due to bacterial and fungal activities. During biomethylation, iAs(III) is oxidized to iAS(V) and Equation gets reduced to Equation , subsequently generating stable As oxy-species (Fergusson, 1990). The biological availability of As and its toxicological and physiological effects depend on its chemical state (Cullen and Reimer, 1989). iAs(III) is much more toxic, more soluble, and more mobile than iAs(V). The H3AsO3 in the soil can be transformed into H3AsO4 by the oxidizing features. The As levels in the soils of different countries are depicted in Table 1 (Mandal and Suzuki, 2002).

Table 1

2.1.4: Water

Small concentrations of As are found in natural water. The World Health Organization (WHO) and the United States Environmental Protection Agency (US EPA) set the maximum permissible and recommended value of As in drinking water, at 10 μg/L and 50 μg/L, respectively (Interim Primary Drinking Water Standards, 1975; Compounds, 2001). The dominant species of As in both groundwater and sea water is iAs(III). The concentration of As in uncontaminated freshwater usually lies between 1 and 10 μg/L, whereas in contaminated areas such as sulfide mineralization and mining sites, it ranges from 100 to 5000 μg/L (Smedley et al., 1996). Compared to other oxyanion-forming elements, As is one of the most challenging substances in the atmosphere due to its relative mobility under widespread redox conditions. The iAs(V) oxyanions such as H3AsO4, Equation , Equation , and Equation exist at moderate or high redox potentials. Conversely, iAs(III) exists as H3AsO3 under most reducing scenarios. However, As⁰ and As³− are not found in aquatic environments. Although river water contains a small concentration (0.1–0.8 μg/L) of As, large concentrations (10–70 μg/L) are detected in river waters located in geothermal areas; examples are New Zealand, Japan, and the western United States (McLaren and Kim, 1995). Arsenite, arsenate, and methylated forms are available in lake and pond waters, while groundwater does not contain methylated forms of As. Many countries, including Ghana, Thailand, the United States, and Greece, are experiencing serious problems with As in their water due to mining (Fig. 2).

Fig. 2

Fig. 2 Distribution of documented world problems with As in groundwater in major aquifers as well as water and environmental issues related to mining and geothermal sources. Areas in blue (dark gray in print version) are lakes ( Smedley and Kinniburgh, 2002 ).

2.1.5: Air

The arsenite and arsenate forms of As can be exposed to air through particulate matter. Organic forms of As exist on sites where arsenic pesticides are used or due to biotic activity (Davidson et al., 1985). The average concentration of As in air varies from 0.4 to 30 ng/m³. The US EPA set the level of As at 6.0 ng/m³, whereas the European Commission (EC) laid the standard As level for the European zone as 0.2–1.5 ng/m³ in rural areas, 0.5–3.0 ng/m³ in urban areas, and less than 50.0 ng/m³ in industrial zones (Working Group on Arsenic, Cadmium and Nickel Compounds, 2000).

2.1.6: Living species

The As content in plant tissue ranges from below 0.01 to nearly 5.0 μg/g as per dry weight, which can be absorbed from the soil, sediment, and groundwater. Similar to plant tissue, As can accumulate in animal tissue as well. The cumulative levels of As in some sea animals, including coelenterates, a few mollusks, and crustaceans, vary from 0.005 to 0.3 mg/kg, while some shellfish contain more than 100 μg/g (Bowen, 1966). Freshwater fish species contain around 0.54 μg/g of As dry weight basis, but the value can be as much as 77 μg/g in the liver oil of freshwater bass (Whitacre and Pearse, 1974). Arsenic gathers in particular areas of ectodermic tissue of mammals, mainly in the hair and nails. The concentration of As in domestic animals and humans is less than 0.3 μg/g on the basis of wet weight. Anionic and soluble forms of As are absorbed more than insoluble forms of As in the human body. Moreover, iAs exhibits a substantial affinity for hair and the human body’s keratin-rich tissues. The usual As concentrations in human hair and nails are, respectively, 0.08–0.25 μg/g and 0.34 ± 0.25 μg/g (Mazumder et al., 1988). Nondegradable As species such as arsenobetaine and arsenocholine are found extensively in oceanic entities.

2.2: Anthropogenic sources

Human use of natural resources leads to the discharge of As into the environment. The use of As-containing pesticides, fertilizers, dust from fossil fuels, and disposal of industrial and animal wastes are the primary sources of As in soils (Piver, 1983; Woolson, 1983). China, Russia, Mexico, France, Germany, Sweden, Peru, Namibia, and the United States are the main As producers and contribute to around 90% of global As supply. Currently, the amount of As found in products for cultivation purposes is declining. About 97% of As produced enters end product manufacture as white As, while the rest (3%) is in the form of metal for metallurgic activities.

2.2.1: Mining

Mining is one of the major sources of As in the environment. Arsenic is produced and recovered mostly from flue dust, speiss, and sludge linked to the smelting of Cu, Pb, Au, and Ag ores containing As. Worldwide, the amount of As mining produces approximately 37,121 tonnes/year. In the year 2000, the world’s total mined As amounted to 3.3 million tonnes, which was 55.1 times larger than that in 1900. Estimating the world’s As production is very uncertain compared with heavy metals, especially since As is a by-product of the mining and processing of nonferrous metals (Loebenstein, 1994). It is assumed that there is nearly 6.5 kg of As per tonne of copper, and given the postindustrial global Cu production, the alternative accumulative postindustrial As production in 2000 amounted to nearly 3.0 million tonnes (Han et al., 2002).

2.2.2: Coal and petroleum industries

Another prominent As source on the earth is the coal and petroleum industries. Arsenic is volatilized from charred coal but can compress downstream into tiny particulate matter. The global coal and petrochemical industries are responsible for 46% of the world’s gross As production annually. Meanwhile in the year 2000 their overall support for industrial-age gross As production was 27%. Global industrial-age anthropogenic As sources (i.e., cumulative production) are in the following order: As mining production > As generated from coal > As generated from petroleum. The potential industrial-age anthropogenic As added to the world’s arable surface in 2000 was 2.18 mg As/kg, which is 1.2 times greater than that being deposited in the lithosphere. In fact, As concentration in coal varies over a huge range from 0.3 to 93 mg/kg according to one study (Bowen, 1979), while another reported 0.34–130 mg/kg (Piver, 1983).

Some coal from Europe, New South Wales, New Zealand, and the United States contains As varying from trace amounts to 200 mg/kg (Wedepohl et al., 1969). Some coal deposits in China contain several thousand mg As/kg. Compared to this, the production of global petroleum since the 1950s has risen exponentially. Since the As concentration in petroleum is relatively small, ranging from 0.0024 to 1.63 mg/kg (Pacyna, 1987), an average As concentration of 0.26 mg/kg (Bowen, 1979) served to estimate the extent to which petroleum contributes As. Additionally, the amount of As created from petroleum is relatively minimal compared to that originating from coal. Arsenic derived from petroleum was less than 6% of total As generated from petroleum and coal. Aggregate global As production from coal and petroleum in 2000 was 1.24 million tonnes, which was 14 times larger than that in 1900 (Han et al., 2003).

2.2.3: Insecticides and herbicides

For many decades, As was widely employed in the manufacture of insecticides and pesticides. At present, such pesticides are reducing the amounts of lead arsenate, Ca3AsO4, copper acetoarsenite, Paris Green (copper acetoarsenite), H3AsO4, monosodium methanearsonate (MSMA), disodium methanearsonate (DSMA), and cacodylic acid. However, these are still being utilized in the cotton industry as pesticides (Berry et al., 1978). As well, sodium arsenate (NaAsO4) was extensively used as a weed killer, mainly as a nonselective soil sterilant in the 1890s.

2.2.4: Desiccants and wood preservatives

Arsenic acid H3AsO4 has been commonly used as a cotton desiccant for many years. Fluor chrome arsenic phenol (FCAP), chromated copper arsenate (CCA) and ammoniacal copper arsenate (ACA) combined, wolman salts and osmosalts, zinc, and chromium arsenate continue to serve as wood preservatives.

2.2.5: Feed additives, drugs, and poisons

Compounds of As such as H3AsO4, 3-nitro-4-hydroxy phenylarsonic acid, and 4-nitrophenylarsonic acid are prominently used as feed additives. Completely substituted phenylarsonic acids were employed for feed additives under the US Food Additives Law of 1958. Arsenic has been used in medicinal purposes for nearly 2500 years. Arsenic was contained in medical preparations that include Asiatic pills (arsenic trioxide and black pepper), Donovan’s solution (arsenic and mercuric iodides), Fowler’s solution (potassium arsenite), de Valagin’s solution (liquor arsenii chloridi), arsphenamine (Salvarsan), neoarsphenamine, sodium cacodylate, oxophenarsine hydrochloride (Mapharsen), arsthinol (Balarsen), acetarsone, tryparsamide, and carbarsone (Vallee et al., 1960). In spite of its claimed medicinal uses, As compounds are in fact powerful and dangerous toxins, and the poison of choice for those people homicidally or suicidally inclined.

3: Point and diffuse sources of As pollution

Both the point (source of contamination is easily identifiable) and diffuse (land-based sources) sources of As contamination are evident in the environment. The point source of As emission can be an easily identified and confined place such as a pipe, ditch, ship, or factory smokestack. For many decades throughout the world, factories discharged their effluents directly into bodies of water such as rivers, canals, lakes, estuaries, etc., so these were obvious point sources of As pollution. Other major point sources of As pollution include municipal wastewater effluents, industrial wastewater effluents, and gaseous emissions from industries. In contrast, diffuse sources of As contamination may occur from land-based sources of pollution, other than point sources, from which As-containing materials enter the environment due to land runoff, precipitation, atmospheric deposition, groundwater, erosion (load from eroded materials), drainage, seepage or hydrologic modification or destruction of habitats. Typical examples of As diffuse pollution include fertilizers in agriculture and forestry, pesticides applied to a wide variety of land use, contaminants from roads and paved areas, and industries’ deposition of As-containing contaminants into the atmosphere. For future environmental remediation projects and estimating the As pollution outcomes of prior control measures at industrial sites and sources, it is necessary to differentiate between point and diffuse sources. Inventories and basic hydrological relationships between transported load and discharge can serve to distinguish between point and diffuse