Introduction on Emerging Contaminants in Rivers and Their Environmental Risk

Origin, types, and contribution of emerging pollutants to environmental degradation and their remediation by physical and chemical techniques

The growing presence of emerging pollutants (EPs) in aquatic environments, as well as their harmful impacts on the biosphere and humans, has become a global concern. Recent developments and advancements in pharmaceuticals, agricultural practices, industrial activities, and human personal care substances have paved the way for drastic changes in EP concentrations and impacts on the ecosystem. As a result, it is critical to mitigate EP's harmful effects before they jeopardize the ecological equilibrium of the overall ecosystem and the sustainable existence of life on Earth. This review comprehensively documented the types, origins, and remediation strategies of EPs, and underscored the significance of this study in the current context. We briefly stated the major classification of EPs based on their organic and inorganic nature. Furthermore, this review systematically evaluates the occurrence of EPs due to the fast-changing ecological scenarios and their impact on human health. Recent studies have critically discussed the emerging physical and chemical processes for EP removal, highlighting the limitations of conventional remediation technologies. We reviewed and presented the challenges associated with EP remediation and degradation using several methods, including physical and chemical methods, with the application of recent technologies. The EP types and various methods discussed in this review help the researchers understand the nature of present-day EPs and utilize an efficient method of choice for EP removal and management in the future for sustainable life and development activities on the planet.

Mechanistic explanation and influence of molecular structure on chemical degradation and toxicity reduction by hydroxyl radicals

This study explored the influence of structural characteristics of organic contaminants on the degradation during an advanced oxidation process (AOP). The target contaminants were acetaminophen (ACT), bisphenol A (BPA), and tetracycline (TC). The Fenton process was selected as the model process in which major reactive species of hydroxyl radicals in most AOPs are generated for target compound degradation. The optimal reagent concentration ratio was [Fe2+]/[H2O2] = 0.5 mM/0.5 mM in an acidic condition, resulting in 83.49%, 79.01%, and 91.37% removals of ACT, BPA, and TC, respectively. Contrarily, the mineralization rates were apparently lower compared to their respective removal efficiencies. Experimental observation also suggested that the aromatic structure was rather difficult to degrade since their unsaturated electron clouds would hinder the attack of hydroxyl radicals due to electric repulsion. The preferred attacking sites of an aromatic ring differ due to the functional groups and structure symmetry. However, the electrophilic attack of the hydroxyl radical is the major reaction for decomposing aliphatic structures of cyclic or branched organics, resulting in the highest removal and mineralization of TC among these three tested chemicals. In addition, an apparent removal of a contaminant may not necessarily reduce its toxic impact on the environment.

Pharmaceuticals and endocrine disrupting compounds modulate adverse effects of climate change on resource quality in freshwater food webs

Freshwater biodiversity, ecosystem functions and services are changing at an unprecedented rate due to the impacts of vast number of stressors overlapping in time and space. Our study aimed at characterizing individual and combined impacts of pollution with pharmaceuticals (PhACs) and endocrine disrupting compounds (EDCs) and increased water temperature (as a proxy for climate change) on primary producers and first level consumers in freshwaters. We conducted a microcosm experiment with a simplified freshwater food web containing moss (Bryophyta) and shredding caddisfly larvae of Micropterna nycterobia (Trichoptera). The experiment was conducted with four treatments; control (C), increased water temperature + 4 °C (T2), emerging contaminants' mix (EC = 15 PhACs & 5 EDCs), and multiple stressor treatment (MS = EC + T2). Moss exhibited an overall mild response to selected stressors and their combination. Higher water temperature negatively affected development of M. nycterobia through causing earlier emergence of adults and changes in their lipidome profiles. Pollution with PhACs and EDCs had higher impact on metabolism of all life stages of M. nycterobia than warming. Multiple stressor effect was recorded in M. nycterobia adults in metabolic response, lipidome profiles and as a decrease in total lipid content. Sex specific response to stressor effects was observed in adults, with impacts on metabolome generally more pronounced in females, and on lipidome in males. Thus, our study highlights the variability of both single and multiple stressor impacts on different traits, different life stages and sexes of a single insect species. Furthermore, our research suggests that the combined impacts of warming, linked to climate change, and contamination with PhACs and EDCs could have adverse consequences on the population dynamics of aquatic insects. Additionally, these findings point to a potential decrease in the quality of resources available for both aquatic and potentially terrestrial food webs.

Trophodynamic of endocrine disrupting compounds in the aquatic food webs: Association with hydrophobicity and biota metabolic rate

Increasing concentration of endocrine disrupting compounds (EDCs) are released into the aquatic environment, resulting in irreversible effects on the endocrine and reproductive systems of biota. How the liver enzymes affect metabolic rate of these compounds and thus their structure-related trophic transfer in aquatic food webs remains largely unknown. In this study, the concentrations of seven common EDCs were measured in 15 species of fish, 7 invertebrate species and plankton collected from Liuxi River to Pearl River, South China. The mean ΣEDC concentrations generally were found to increase as follows: plankton (29.59 ng g^-1 dw) < invertebrate species (50.69 ng g^-1 dw) < fish (122.56 ng g^-1 dw), with 4-nonylphenol (4-NP) and bisphenol S (BPS) as the predominant components. Trophic magnification factors (TMFs) values were >1.0 ranged from 1.30 (BPS) to 4.07 (4-NP), indicating trophic magnification potential. Measurement of metabolism and activities of microsomal CYP450 enzymes were performed in the fish liver microsomes of Hypophthalmichthys molitrix ([TL] = 2.27), Cirrhinus mrigala (TL = 3.87) and Odontamblyopus rubicundus (TL = 4.73). TMFs were significantly negatively correlated with the obtained in vitro biotransformation clearance rates (CL _{in vitro}) of EDCs and CYP450 enzymes activities. A multiple linear regression model indicated that biotransformation clearance is a more powerful predictor for TMFs than the hydrophobicity (Kow) to drive changes in the studied aquatic food web trophodynamics.

Emerging contaminants of high concern for the environment: Current trends and future research

Wastewater is contaminated water that must be treated before it may be transferred into other rivers and lakes in order to prevent further groundwater pollution. Over the last decade, research has been conducted on a wide variety of contaminants, but the emerging contaminants are those caused primarily by micropollutants, endocrine disruptors (EDs), pesticides, pharmaceuticals, hormones, and toxins, as well as industrially-related synthetic dyes and dye-containing hazardous pollutants. Most emerging pollutants did not have established guidelines, but even at low concentrations they could have harmful effects on humans and aquatic organisms. In order to combat the above ecological threats, huge efforts have been done with a view to boosting the effectiveness of remediation procedures or developing new techniques for the detection, quantification and efficiency of the samples. The increase of interest in biotechnology and environmental engineering gives an opportunity for the development of more innovative ways to water treatment remediation. The purpose of this article is to provide an overview of emerging sources of contaminants, detection technologies, and treatment strategies. The goal of this review is to evaluate adsorption as a method for treating emerging pollutants, as well as sophisticated and cost-effective approaches for treating emerging contaminants.

A review on effective removal of emerging contaminants from aquatic systems: Current trends and scope for further research

Wastewater is water that has already been contaminated by domestic, industrial and commercial activity that needs to be treated before it could be discharged into some other water bodies to avoid even more groundwater contamination supplies. It consists of various contaminants like heavy metals, organic pollutants, inorganic pollutants and Emerging contaminants. Research has been doing on all types of contaminates more than a decade, but this emerging contaminants is the contaminants which arises mostly from pharmaceuticals, personal care products, hormones and fertilizer industries. The majority of emerging contaminants did not have standardized guidelines, but may have adverse effects on human and marine organisms, even at smaller concentrations. Typically, extremely low doses of emerging contaminants are found in the marine environment and cause a potential risk to the aquatic animals living there. When contaminants emerge in the marine world, they are potentially toxic and pose many risks to the health of both man and livestock. The aim of this article is to review the Emerging contaminate sources, detection methods and treatment methods. The purpose of this study is to consider the adsorption as a beneficial treatment of emerging contaminants also advanced and cost effective emerging contaminates treatment methods.