Emerging Contaminants and Plants

With the advancement of science, better monitoring of soil and water quality has become possible. Many contaminants have been reported in the recent past that influence the quality of soil and water negatively. However, the consideration of these pollutants or contaminants is still in the initial stage and needs to be explored in detail for a better understanding of their activity as contaminants. Emerging contaminants such as agrochemicals, nanomaterials, pharmaceuticals, personal care products, and micro- or nanoplastics have been found to show several harmful impacts on soil or water quality. Emerging contaminants are known to have adverse effects on plants and human beings too. The risk of their entry into the crops, food chain, and any possible interaction to human health should be properly monitored. The concentration of these contaminants in soil and water should also be monitored on a regular basis to avoid the significant damages arising from them. Future study may also be taken into consideration to avoid the possible concerns to natural resources, plants, and human wellbeing.

Metal-based nanoparticles (NPs) are one of the most manufactured nanomaterials and deserve singular attention given their continuous input to the environment, lack of degradation, and accumulation risk. In agricultural soils, the use of organic amendments and wastewater and the application of nanotechnology are important NP inputs. Metal-based NPs have beneficial applications as fertilizers and increase plant resistance to pathogens and environmental abiotic stressors. Ag-, Zn-, Cu-, Ti-, and Ce-based NPs are the most widely used to improve crop production. NPs can also have negative impacts, including phytotoxicity, lower nutrient content in plants, and soil microorganism toxicity. The potential NP interaction with other soil contaminants, including metals and organic compounds, is a major concern because it can modify the bioconcentration or affect the intrinsic toxicity of both substances with the consequent biological impact on plants. Exposure to NP-contaminant mixtures may induce unexpected toxic effects via several different mechanisms that affect the availability, uptake, and metabolic processes involved in the detoxification and degradation of compounds. However, the mechanisms underlying the effects of the NP-contaminant interaction on joint toxicity are poorly understood. This chapter covers some of the most relevant issues concerning the effects of metal-based NPs on plants.

The development of nanotechnology via the enormous utilization of engineered nanoparticles (ENPs) in agriculture sector including metal (M) or metallic (MT) nanoparticles (NPs) has increased. Although, large surface area and particular sizes of NPs are some of the desired traits to ameliorate the environmental stress factors and modify the plant physiological processes, thereby leads to improve the crop production. The potential toxic nature of M or MT NPs (mainly depends upon their characteristics) sometimes causes toxic effects by inducing the extra production of reactive oxygen species, thus causing oxidative stress. Moreover, the M or MT NP–induced oxidative stress impairs the cellular biomolecules and causes imbalance in plant biological and metabolic processes. In this way, it is crucial to explore the mechanisms involved in M or MT NP–mediated phytotoxicity along with NP detoxification strategies that can be helpful to understand the various morpho-physiological, biochemical, and metabolic responses of plants. To address this, recent studies concerning the M or MT NP toxicity at morpho-physiological, biochemical, cellular, and molecular levels have been discussed in this chapter. Factors affecting M or MT NP toxicity have also been overviewed. In addition, the potential detoxification strategies such as the applications of antioxidants, phytohormones, surface modifications, and omics approaches to minimize or ameliorate M or MT NP toxicity in different plants have been reviewed.

Emerging contaminants are targeted as primary pollutants of great concern for the ecosystem health. The evaluation of their effects on biota by non-destructive and reliable techniques is an issue receiving growing interest within the scientific community, particularly for plants. Beside commonly used proxies such as growth parameters and chlorophyll content, a set of non-standard endpoints has been proposed to be effectively used for the evaluation of the toxicity effects of xenobiotics on plants. Among them, chlorophyll fluorescence and leaf reflectance spectra analyses were reported as information-rich, non-destructive, and real-time mode technologies to assess the physiological status of plants. To verify their applicability for the ecotoxicology assessment in plants, a case study was set up by investigating the effects of dimethyl phthalate (DMP), an emerging contaminant in the aquatic environment, on two aquatic model plants (Lemna minor L. and Spirodela polyrhiza (L.) Schleid.), paralleling standard and non-standard toxicity endpoints. Results of a 7-day toxicity assay highlighted the effectiveness of chlorophyll fluorescence parameters and leaf reflectance spectra to assess the toxicity status of plants. Specifically, it was evidenced a lack of toxicity effects at 3 (DMP1) and 30 (DMP2) mg/L DMP in both Lemna and Spirodela plants, while at the highest DMP concentration (600 mg/L, DMP3), biometric and physiological endpoints revealed a toxicity status in both plant species, particularly in Spirodela. Thus, the performed case study evidenced the suitability of the targeted non-standard endpoints in assessing the ecotoxicity of DMP in aquatic plants, also contributing to shed light on the environmental risk posed by phthalates in the freshwater compartment.

Pesticides are noxious organic and inorganic compounds used to kill or restrict the population expansion of harmful organisms. Pesticides have been used for a long period to kill pests and protect crops. Pesticides have been in use since the early 1940s, when dichlorodiphenyltrichloroethane (DDT) was first launched, ushering in a new era in man’s struggle against pests and pathogens. Pesticide technologies have continued to generate a wide range of pesticides, providing adequate food supply to meet consumer demand, and these pesticides are considered an important tool for crop protection and growth, but they are harmful to the environment. Pesticide overuse can lead to biodiversity loss and destruction. Biodiversity is critical to human survival on our planet. Pesticides are harmful to a variety of creatures, including birds, aquatic animals, and mammals. Pesticides are a key source of anxiety for the long-term survival of our planet. This chapter will discuss the pesticide groups, their use, and impact on the environment. This chapter also discusses pesticide contamination and the long-term consequences of pesticides on the entire ecosystem. An alternative pest management and control strategy, such as integrated pest management (IPM), can be helpful to minimize the number and volume of pesticide treatments by integrating several control measures, like cultural control, the use of resistant genotypes, and physico-mechanical control along with chemical control. Furthermore, advances in biotechnology and nanotechnology may make it simpler to develop herbicides with fewer adverse effects or resistant genotypes along with a lower dose of herbicides.

Persistent organic pollutants (POPs) are a group of organic molecules that resist natural degradation, bioaccumulate in the food web and organisms, and have serious health consequences. POPs are vulnerable to long-range atmospheric transport (LRAT), resulting in transboundary deposition, due to their lengthy residence duration in the climate and semi-volatility nature. POPs are poisonous, resistant to degradation, and bioaccumulative and have a wide spatial distribution, all of which have been related to mutagenic, reproductive, and immunological diseases. A global accord was reached at the Stockholm Convention to reduce and eventually eradicate the discharge of POPs directly into the environment. Organohalogenated chemicals, polycyclic aromatic hydrocarbons (PAHs), and pesticides are examples of persistent organic pollutants (POPs) that can be produced in a wide range of environmental compartments. Their existence in the aquatic environment is a global issue, with sediments serving as a store and hence a source of hydrophobic, stubborn, and toxic substances. Furthermore, because these pollutants vary in their capacity to bioaccumulate in tissues, they may impact the reproduction and death of living species. Organochlorine insecticides, polychlorinated biphenyls, and dioxins are among the synthetic compounds classified as persistent organic pollutants. Environmental persistence, transboundary movement, lipophilicity, and bioaccumulation are all characteristics of these organic pollutants, which might result in biomagnification-induced death, especially in top-ranked biota. POPs accumulate in the oceanic ecosystems, which is why they are so important. Despite the ubiquity of POPs and the biotic impacts they induce, there is a lack of information on their occurrences and their destiny in the environment. Organohalogenated chemicals, polycyclic aromatic hydrocarbons, and pesticides are examples of persistent organic pollutants (POPs) that can be found in a variety of environmental compartments. Their existence in the aquatic environment is a global issue, with sediments serving as a storehouse and, as a result, a source of hydrophobic, persistent, and toxic substances. The presence of these persistent hazardous compounds in sediments indicates that aquatic contamination has occurred as a result of agricultural, industrial, and urban discharges, raising concerns about possible dangers to aquatic species, wildlife, and humans. This chapter aims to provide an updated comprehensive overview of the occurrence, distribution, and fate aspects of POPs. In addition, the chemical structures and properties of specific POPs are discussed.

The developing new technologies and urbanization make ease to livelihood but also create new challenges to mankind and living creatures. There are several toxic compounds rigorously released in the environment, and due to their high hydrophobic nature as well as their non-degradable properties, they become a major concern to human health. There are several techniques introduced to treat these emerging contaminants like endocrine-disrupting compounds, pharmaceutical compounds, antiepileptic drugs, antibiotics, dyes, wastewater contaminants, organic and household wastes, and personal care products. The remediation processes are introduced using plants, fungi, and bacteria. The algae such as microalgae and cyanobacteria are found more reliable and good biological tool to remediate these contaminants. The process of removal of these emerging contaminants using algae is called phyco-remediation. New technologies like genetic engineering incorporated with these microalgae are a promising tool to cope up with these emerging contaminants and help in detoxifying these contaminants from the ecosystem. The present chapter discusses all aspects related to the concept of emerging contaminants and its types and the role of microalgae and cyanobacteria in the removal of these contaminants with proper mechanisms. Also, this chapter provides some future prospects regarding the applications of phyco-remediation with respect to some other fields like advanced oxidation processes and genetic engineering.

The rapid population expansion in recent years, level of urbanization, and accessibility to healthcare are the main causes of rising active pharmaceutical ingredient (API) emission in the environment. The primary drivers of rising pharmaceutical production—poor laws, self-medication, the dispensing of antibiotics without a prescription, and the use of illicit drugs—lead to their appearance as quickly growing natural pollutants. For the past three decades, pharmaceutical residues have been discovered in nearly every natural setting on every continent, including groundwater, wastewater treatment facilities, effluent, and influent as well as surface water (lakes, rivers, streams, estuaries, and ocean). According to reports, pharmaceutical contamination is currently present in the tropical regions and adjacent areas of the world. Sludge and wastewater from municipal wastewater treatment plants, as well as businesses, hospitals, and homes, are the primary sources of APIs. Significant amounts of pharmaceuticals are released and accumulate in the environment as a result of wastewater application for irrigation and biosolids used as organic fertilizers. The fact that APIs tend to be less volatile, highly polar, and hydrophilic makes them “compounds of rising concern.” APIs can become inactive by soil contact, sorption, discharge, or environmental or microbiological change. The potentially dangerous consequences of these active compounds on the ecosystem have just recently come to light because they constitute a life-threatening hazard to soil biota, aquaculture, plants, animals, and ultimately humans. There must be a variety of legal, therapeutic, and disposal solutions that are not only effective but also technically and financially feasible because there are so many different types of APIs. The entry of APIs into the food chain must also be carefully investigated in order to develop methods to decrease their impact on biodiversity.

Nanoparticles are emerging plant contaminants applied through soil or foliarly to deliver plant nutrients to the plants for growth development and stress tolerance. Nanoparticles capable of entering into plant cells and leaves can transport nutrients into different parts of the plant. Nanoparticles contain magic bullets such as nano-fertilizer and nano-pesticides. Naturally occurring nanoparticles are found in volcanic ash and ocean biological matter such as viruses and dust. The prime application of nanotechnology is to increase crop production with minimum losses and to activate plant defense mechanism against pests, insects and other environmental challenges. In this chapter we will discuss nanoparticles, their fate in plants, and their role in physiological and molecular stress tolerance in plants.

During growth and development, plants uptake a wide range of mineral nutrients from soil, including some non essential toxic elements such as arsenic (As), cadmium (Cd), etc. These contaminants inhibit uptake and translocation of essential solutes and nutrients as well as water, induce oxidative damage and disrupt plant metabolism. Such toxicity directly affects health of human individuals relying on such plants as a primary food source. As and Cd generally follow relatively similar pathway for entry in plant systems, as well as in terms of toxicological effects and sequestration machineries. They utilize certain common routes and membrane transporters for cellular uptake and translocation; however, some machinery also differs in this regard. Biomagnifications of As and Cd in the food chain is an important area of research to implement mitigation strategies. As a defense and detoxification mechanism, plants have evolved adaptive features such as efflux mechanisms, complexation with thiol-rich compounds and vacuolar sequestration. Plasma-membrane efflux transporters, phytochelatin-complexation and subsequent vacuolar sequestration have been reported to render As and Cd tolerance in important crop plants like rice. Although Cd levels are generally not high enough to cause phytotoxicity, Cd accumulation in edible plant parts is unsafe for human consumption. On the other hand, As-contamination in soil can cause massive phytotoxicity. Besides the traditional methods like soil amendments, use of soil microorganisms and plant growth regulators, modern-day-approaches like genetic engineering and/or priming techniques, especially with nanoparticles can significantly augment plant tolerance against metal stress and the associated biogeochemical calamities. This book chapter provides a comprehensive overview on agro-ecotoxicological aspects of the two emerging contaminants, namely, As and Cd along with adaptive mechanisms of plants and scientific approaches for metal stress alleviation.

Persistent organic pollutants (POPs) have adverse effects on the environment as they accumulate in the fatty acids and have a half-life on the scale of years to decades. These pollutants are contaminants of emerging concern (CECs) owing to their biological concerns related to health impacts and also economic benefits. In the US, UK, and Asia about 20% of the food is reported to be contaminated with low levels of POPs and there is no scientific accord on whether these low-level POPs are a matter of concern for humans. The treatment and removal of these organic pollutants are difficult as they travel to far areas through different mediums such as food, air, water, and soil. Remediation of POPs from air, water, soil, and other environmental compartments is crucial and a fundamental concern. For the remediation of POPs conventional treatments such as physio-chemical methods, i.e., coagulation, flocculation, oxidation, and adsorption have been utilized extensively in past decades. However, one of the useful methods of remediating POP pollution in the environment is bioremediation. Biological methods are expected to be a tremendous accomplishment in the cleanup of POPs by having advantages over conventional process. There are different methods that are used to remove these pollutants such as bioremediation, osmosis, adsorption process, membrane technology, and AOPs. For the implementation of these techniques there is a need to consider other factors such as economy, potential, and technical feasibility. Different research projects have been carried out and attempts have been made to find alternatives that are more cost effective. POPs are of great importance for some industries; thus, they are not totally avoidable. The only solution to this problem is to adapt techniques that can degrade the POPs effectively.

The increase in the world’s population in the twentieth century resulted in the subsequent increase in the demand for food. To enhance the constant supply of food for this large population and sustainable crop production, different types of agrochemicals such as fertilizers, pesticides, fungicides, and herbicides were used by farmers for decades. Pesticides are mainly categorized as herbicides, fungicides, and insecticides based on the target they killed. Pesticides and herbicides are designed to kill and prevent pests and unwanted weeds respectively. As their mode of action is not species specific, they often harm other organisms including crops in the agricultural field when used in excess amounts. Over time, insects and weeds become adapted and develop resistance to such chemicals, which necessitates the excessive amount of usage and development of new chemical compounds to protect crops. In many developing countries cheap compounds, such as dichloro-diphenyl-trichloroethane (DDT), hexachlorocyclohexane (HCH), and lindane are popular among farmers, even though they are environmentally persistent and have a toxic effect on soil flora and fauna. Thus, the pesticide and herbicide compounds have emerged as a new global concern owing to their several phytotoxic effects. Moreover, the development of leaf and crop growth rate, and the nutritive composition of seeds, specifically the content of proteins, fall sharply following pesticide treatment. The herbicides and pesticides cause several cytotoxic and genotoxic effects which ultimately challenge the stability of the plant genome through the production of reactive oxygen compounds. To combat these stress conditions, plants have evolved several biochemical, physiological, transcriptional, and epigenetic strategies that together help to maintain the growth and development of plants. In this present book chapter, we summarize the harmful effects of pesticides and herbicides on crop plants and the different strategies evolved by plants to combat these emerging stress compounds to sustain growth and eventually survivability.

Emerging contaminations (ECs) have been discovered in water (municipal, drinking, and groundwater), food sources, soil, and aquatic bodies. These ECs may be from industrial, agriculture, hospital, and laboratory waste. ECs might alter reproductive functions in males and females, increase the chance of breast cancer, alter growth patterns, cause changes in immune function, and delay neurodevelopment in children. In this context, several nanomaterials (NMs), mainly carbon-based nanomaterials (CNMs) like carbon nanotubes (CNTs), carbon nanofibers (CNFs), and graphene have been effectively used in the removal of ECs from water due to their unique characteristics. This chapter focuses on synthesizing CNMs using the chemical vapor deposition (CVD) and liquid-phase exfoliation processes. We also discuss the removal ECs, mainly pharmaceutical compounds, endocrine disruptor compounds, and personal care products based on metal incorporation, surface functionalization, and polymeric composite materials.