Thallium in aquatic environments and the factors controlling Tl behavior

The Determination of Thallium in the Environment: A Review of Conventional and Advanced Techniques and Applications

Thallium (Tl) is a potential toxicity element that poses significant ecological and environmental risks. Recently, a substantial amount of Tl has been released into the environment through natural and human activities, which attracts increasing attention. The determination of this hazardous and trace element is crucial for controlling its pollution. This article summarizes the advancement and progress in optimizing Tl detection techniques, including atomic absorption spectroscopy (AAS), voltammetry, inductively coupled plasma (ICP)-based methods, spectrophotometry, and X-ray-based methods. Additionally, it introduces sampling and pretreatment methods such as diffusive gradients in thin films (DGT), liquid-liquid extraction, solid phase extraction, and cloud point extraction. Among these techniques, ICP-mass spectrometry (MS) is the preferred choice for Tl detection due to its high precision in determining Tl as well as its species and isotopic composition. Meanwhile, some new materials and agents are employed in detection. The application of novel work electrode materials and chromogenic agents is discussed. Emphasis is placed on reducing solvent consumption and utilizing pretreatment techniques such as ultrasound-assisted processes and functionalized magnetic particles. Most detection is performed in aqueous matrices, while X-ray-based methods applied to solid phases are summarized which provide non-destructive analysis. This work improves the understanding of Tl determination technology while serving as a valuable resource for researchers seeking appropriate analytical techniques.

Assessing Metal Toxicity on Crustaceans in Aquatic Ecosystems: A Comprehensive Review

Residual concentrations of some trace elements and lightweight metals, including cadmium, copper, lead, mercury, silver, zinc, nickel, chromium, arsenic, gallium, indium, gold, cobalt, polonium, and thallium, are widely detected in aquatic ecosystems globally. Although their origin may be natural, human activities significantly elevate their environmental concentrations. Metals, renowned pollutants, threaten various organisms, particularly crustaceans. Due to their feeding habits and habitat, crustaceans are highly exposed to contaminants and are considered a crucial link in xenobiotic transfer through the food chain. Moreover, crustaceans absorb metals via their gills, crucial pathways for metal uptake in water. This review summarises the adverse effects of well-studied metals (Cd, Cu, Pb, Hg, Zn, Ni, Cr, As, Co) and synthesizes knowledge on the toxicity of less-studied metals (Ag, Ga, In, Au, Pl, Tl), their presence in waters, and impact on crustaceans. Bibliometric analysis underscores the significance of this topic. In general, the toxic effects of the examined metals can decrease survival rates by inducing oxidative stress, disrupting biochemical balance, causing histological damage, interfering with endocrine gland function, and inducing cytotoxicity. Metal exposure can also result in genotoxicity, reduced reproduction, and mortality. Despite current toxicity knowledge, there remains a research gap in this field, particularly concerning the toxicity of rare earth metals, presenting a potential future challenge.

Understanding the role of manganese oxides in retaining harmful metals: Insights into oxidation and adsorption mechanisms at microstructure level

The increasing intensity of human activities has led to a critical environmental challenge: widespread metal pollution. Manganese (Mn) oxides have emerged as potentially natural scavengers that perform crucial functions in the biogeochemical cycling of metal elements. Prior reviews have focused on the synthesis, characterization, and adsorption kinetics of Mn oxides, along with the transformation pathways of specific layered Mn oxides. This review conducts a meticulous investigation of the molecular-level adsorption and oxidation mechanisms of Mn oxides on hazardous metals, including adsorption patterns, coordination, adsorption sites, and redox processes. We also provide a comprehensive discussion of both internal factors (surface area, crystallinity, octahedral vacancy content in Mn oxides, and reactant concentration) and external factors (pH, presence of doped or pre-adsorbed metal ions) affecting the adsorption/oxidation of metals by Mn oxides. Additionally, we identify existing gaps in understanding these mechanisms and suggest avenues for future research. Our goal is to enhance knowledge of Mn oxides' regulatory roles in metal element translocation and transformation at the microstructure level, offering a framework for developing effective metal adsorbents and pollution control strategies.

Thallium - poisoner's poison: An overview and review of current knowledge on the toxicological effects and mechanisms

Thallium (Tl) is one of the most toxic metals and its historic use in homicides has led it to be known as "the poisoner's poison." This review summarizes the methods for identifying Tl and determining its concentrations in biological samples in recently reported poisoning cases, as well as the toxicokinetics, toxicological effects, toxicity mechanisms, and detoxication methods of Tl. Recent findings regarding Tl neurotoxicological pathways and toxicological effects of Tl during pregnancy are also presented. Confirmation of elevated Tl concentrations in blood, urine, or hair is indispensable for diagnosing Tl poisoning. The kidneys show the highest Tl concentration within 24 h after ingestion, while the brain shows the highest concentration thereafter. Tl has a very slow excretion rate due to its large distribution volume. Following acute exposure, gastrointestinal symptoms are observed at an early stage, and neurological dysfunction is observed later: Tl causes the most severe damage in the central nervous system. Alopecia and Mees' lines in the nails are observed within 1 month after Tl poisoning. The toxicological mechanism of Tl is considered to be interference of vital potassium-dependent processes with Tl+ because its ionic radius is similar to that of K+, as well as inhibition of enzyme reactions by the binding of Tl to -SH groups, which disturbs vital metabolic processes. Tl toxicity is also related to reactive oxygen species generation and mitochondrial dysfunction. Prussian blue is the most effective antidote, and metallothionein alone or in combination with Prussian blue was recently reported to have cytoprotective effects after Tl exposure. Because Tl poisoning cases are still reported, early determination of Tl in biological samples and treatment with an antidote are essential.

Anodic Stripping Voltammetric Procedure of Thallium(I) Determination by Means of a Bismuth-Plated Gold-Based Microelectrode Array

This article presents a new working electrode based on a bismuth-plated, gold-based microelectrode array, which is suitable for determining thallium(I) species using anodic stripping voltammetry (ASV). It allowed a significant increase in the sensitivity as compared to other voltammetric sensors. The main experimental conditions and the instrumental parameters were optimized. A very good proportionality between the Tl(I) peak current and its concentration was evidenced in the range from 5 × 10-10 up to 5 × 10-7 mol L-1 (R = 0.9989) for 120 s of deposition and from 2 × 10-10 up to 2 × 10-7 mol L-1 (R = 0.9988) for 180 s. A limit of detection (LOD) of 8 × 10-11 mol L-1 for a deposition time of 180 s was calculated. The effects of interfering ions on the Tl(I) analytical signal were studied. The proposed method was applied for quantitative Tl(I) detection in water certified reference material TM 25.5 as well as in spiked real water samples, for which satisfactory recovery values between 98.7 and 101.8% were determined.

Mechanisms for thallium(I) adsorption by zinc sulfide minerals under aerobic and anaerobic conditions

The highly toxic heavy metal thallium is widely distributed in sulfide ores and released into the environment by sulfide mining. However, the interface between the sulfide minerals and Tl(I) is unclear. In this study, the capacity for adsorption of thallium(I) by a common sulfide mineral (zinc sulfide) was investigated in aerobic and anaerobic environments, which revealed three mechanisms for adsorption on the ZnS surface (surface complexation, electrostatic action and oxidation promotion). Batch experiments indicated that the Tl(I) adsorption capacity of ZnS in an aerobic environment was approximately 9.3% higher than that in an anaerobic environment and was positively correlated with the pH. The adsorption kinetic data showed good fits with the pseudosecond-order model and the Freundlich isotherm model. The Tl(I) adsorption mechanism varied in different oxidative and pH environments. XPS, FTIR, and EDS results implied that complexation with surface hydroxyl groups was involved in the adsorption process. pH experiments and zeta analyses suggested that electrostatic attraction was also involved. Surface complexation and electrostatic attraction were the dominant mechanisms at pH values above 6. Furthermore, oxidative dissolution of ZnS and hydrolysis of Zn2+ enhanced the complexation with hydroxyl groups on the mineral surface and facilitated Tl adsorption. In this study, this interface mechanism provided new insights into thallium migration in sulfurized mineral environments in aerobic and anaerobic transition regions.

Thallium toxicity to temperate and tropical marine organisms: Derivation of water quality guidelines to protect marine life

A lack of thallium (Tl) toxicity data for marine organisms has hampered the development of water quality guidelines for protecting marine life and assessing ecological hazard/risk. This study assessed the toxicity (EC10/EC50) of Tl in natural seawater (salinity 34 psu and pH 8.05) to 26 functionally diverse marine organisms (19 phyla from five trophic levels) from a variety of temperate and tropical coastal marine habitats. EC10 values ranged from 3.0 μg/L (copepod, Acartia tranteri) to 489 μg/L (cyanobacterium, Cyanobium sp.), while EC50 values ranged from 9.7 μg/L to 1550 μg/L. Thallium(I) was the dominant (86-99 %) oxidation state in test waters across the range of EC10 and EC50 values. Thallium toxicity (EC10/EC50) did not differ between temperate and tropical marine organisms. New, reliable, long-term Tl water quality guidelines were derived using species sensitivity distributions (with model-averaging) to protect marine life in Australia (e.g., 3.9 μg/L for 95 % species protection).

Dynamic retention of thallium(I) on humic acid: Novel insights into the heterogeneous complexation ability and responsiveness

Widely distributed soil humic acid (HA) would significantly affect the environmental migration behavior of Tl(I), but a quantitative and mechanistic understanding of the dynamic Tl(I) retention process on HA is limited. A unified kinetic model was established by coupling the humic ion-binding model with a stirred-flow kinetic model, which quantified the complexation constants and responsiveness coefficients during dynamic Tl(I)-HA complexation. Furthermore, the heterogeneous complexation mechanism of HA and Tl(I) was revealed by batch adsorption experiments, stirred-flow migration experiments, and 2D-FTIR-COS analysis. An increase in pH significantly improved the responsiveness of HA organic binding sites, promoting Tl(I) dynamic retention. Monodentate carboxyl groups induced rapid Tl(I) complexation (k_d = 1.9 min^-1) in strongly acidic environments. Under weakly acidic conditions, Tl(I) retention on HA was mainly attributed to the synergistic complexation effect of carboxyl and amide groups. Among the groups, multidentate carboxyl-phenolic hydroxyl sites could achieve sustained Tl(I) retention due to their stable complexing properties (logK = 4.48∼7.46) and slow response (k_d = 1.1 × 10^-3 min^-1). These findings are crucial for a comprehensive understanding of the environmental interactions of Tl(I) with humic substances in swamp environments.

Association of Endocrine-Disrupting Chemicals with All-Cause and Cause-Specific Mortality in the U.S.: A Prospective Cohort Study

Wide exposure to endocrine-disrupting chemicals (EDCs) poses a great risk on human health. However, few large-scale cohort studies have comprehensively estimated the association between EDCs exposure and mortality risk. This study aimed to investigate the association of urinary EDCs exposure with mortality risk and quantify attributable mortality and economic loss. Multivariable Cox proportional hazards regression models were performed to investigate the association of 38 representative EDCs exposure with mortality risk in the National Health and Nutrition Examination Survey (NHANES). During a median follow-up of 7.7 years, 47,279 individuals were enrolled. All-cause mortality was positively associated with 1-hydroxynaphthalene, 2-hydroxynaphthalene, cadmium, antimony, cobalt, and monobenzyl phthalate. Cancer mortality was positively associated with cadmium. Cardiovascular disease (CVD) mortality was positively associated with 1-hydroxynaphthalene, 2-hydroxynaphthalene, and 2-hydroxyfluorene. Nonlinear U-shaped relationships were found between all-cause mortality and cadmium and cobalt, which was also identified between 2-hydroxyfluorene and CVD mortality. J-shaped association of cadmium exposure with cancer mortality was also determined. EDCs exposure may cause 56.52% of total deaths (1,528,500 deaths) and around 1,897 billion USD in economic costs. Exposure to certain phthalates, polycyclic aromatic hydrocarbons, phytoestrogens, or toxic metals, even at substantially low levels, is significantly associated with mortality and induces high economic costs.