Trace Metals Research Articles

Evaluation of the Contamination of Four Metal Trace Elements (ETM) of Tilapia Fish (Oreochromis niloticus) from Two Types of Fish Ponds in an Aquaculture Production Center in Côte d’Ivoire

Trace Metal Element (ETMs) pollution in fish farming is becoming a concern due to difficult production conditions. This study investigated the level of contamination by four trace metals: lead (Pb), mercury (Hg), arsenic (As) and cadmium (Cd). ETM research focused on Oreochromis niloticus from two types of fish ponds in the Haut-Sassandra region of Côte d'Ivoire. The health risk associated with tilapia consumption in this major production area was assessed. The concentration of Trace Metal Elements in fish was measured using a Perkin Elmer argon plasma emission spectrometer, Optima 3000 DV model. The physicochemical parameters of pond water were taken in situ with a multi-parameter. The physicochemical characteristics show that the Haut-Sassandra region is an area favorable to fish farming activity with a neutral pH, an average temperature of 30°C and a conductivity less than 300. As for ETMs, Low concentrations ranging from 0 to 0.040 mg/kg for tilapia, from 0 to 3.0147 mg/kg for sediments and from 0 to 0.3262 mg/kg for ponds water were observed in the matrices studied. Mercury and arsenic were found to be absent in Tilapia. The statistical analyzes carried out showed that the average concentrations of these ETMs are lower than the standards recommended by FAO and European Union. However, bioconcentration factors between 2 and 6 indicate that chemical pollutants in pond water and sediments have a negative impact on Oreochromis niloticus production, As for dam ponds / retentions basins, values less than 1 were obtained. This study reveals that the consumption of Tilapia from fish ponds in the Haut-Sassandra region could presents a low risk. The work has also shown that tilapia from bypass ponds / diversion basin are the most vulnerable to the ETMs studied.

Optimizing combustion efficiency and environmental impact: the influence of SUPERTHERM K2R coal catalyst

ABSTRACT In the contemporary energy landscape, coal remains a dominant choice due to its widespread availability and cost efficiency. However, addressing the pressing need to mitigate fuel expenses and emissions demands enhanced operational efficiency. Enter SUPERTHERM K2R, a versatile combustion catalyst meticulously crafted to optimize the combustion process of Coal/Petcoke, the primary fuels across various industries. This innovative solution aims to curtail direct fuel consumption by 10–15%, offering efficacy across diverse coal variants including Indian, Indonesian, Australian, South African, US Coal, and Petcoke. The key advantages of this coal additive encompass reduced coal usage, diminished pollutant emissions, decreased trace metal presence, and mitigated land degradation resulting from mining activities. There are some auxiliary advantages with this product like – reduction in coal crusher power consumption, reduce forced draft (FD) fan power consumption, reduce coal handling cost because of less coal consumption as compare to normal operation of industry. In case of power plant increased consumption of demineralized (DM) water has been observed.

A Comparative Study on Chemical Speciation of Trace Metals as a Function of Solution pH: A Multivariate Analysis and Simulation Approach

ABSTRACT Biogeochemical activity of trace elements in the environment significantly relies on their chemical speciation. Solution pH influences the chemical speciation and biogeochemical activity of trace elements in the soil-plant continuum. The current study was conducted to simulate the influence of solution pH on chemical fractions of 11 trace elements (arsenic, lead, zinc, copper, chromium, cadmium, mercury, nickel, strontium, antimony, and selenium) using Visual Minteq, a chemical equilibrium model used for the calculation of metal speciation, sorption etc. Results delineated that pH-mediated variations in the chemical speciation of trace elements differed with their type. The results of the current study revealed a dominance of chemical trace element species at acidic (1–6), neutral (7.0), and alkaline (8–14) pH. Divalent trace elements (zinc, cadmium, copper, chromium, nickel, and lead) were the dominant species at acidic pH. However, mercury dominance has a narrow pH range (1–3), while strontium dominance has a wider pH range (1–13). Nitrate, sulfate, and phosphate fractions of trace elements also occurred at pH <8. However, at pH >8, trace elements existed in hydroxide (OH) fractions. In the case of arsenic (arsenite As3+ and arsenate As5+), selenium (selenite Se4+ and selenate Se6+), and antimony (antimonite Sb3+ and antimonate Sb5+), their dominant species get oxidized with increasing pH. Multivariate analysis was conducted for various metals for their dominance as a function of pH. Moreover, Principal Component Analysis verified a linear relation of trace element fractions with pH. Results revealed that solution pH affects the chemical fractions and the phytoavailable fraction of trace elements in growth culture and associated health hazards through soil-plant transfer.

Tracing metal sources and groundwater flow paths in the Upper Animas River watershed using rare earth elements and stable isotopes

Groundwater flow paths and processes that govern metal mobility and transport are difficult to characterize in mountainous bedrock watersheds. Despite the difficulty in holistic characterization, conceptual understanding of subsurface hydrologic and geochemical processes is key to developing remediation plans for locations affected by acid mine drainage, such as the Upper Animas River watershed in southwestern Colorado, USA. Stable isotopes of water and rare earth elements were utilized to evaluate groundwater flow and metal sources within this complex catchment. Stable isotope samples collected from draining mine adits and springs display systematic spatial variation wherein sample sites at higher elevations have greater seasonal variability than sites at lower elevations. The Upper Cement Creek watershed, where multiple draining mines are present, displays the lowest seasonal variation in stable isotopic signatures, potentially indicating the presence of a large, well-mixed volume of groundwater storage or interbasin groundwater flow. Rare earth elements display statistically significant variation between different alteration styles in the catchment. Overprinting of regional propylitic alteration is evident based on enrichment of middle rare earth elements in acidic springs and mines that are not spatially associated with surficial exposures of acid generating alteration styles. Europium anomaly and middle rare earth enrichment signatures from two flooded mine tunnels on opposite sides of a watershed divide indicate connections to the same subsurface flooded mine workings.

The mediating role of inflammatory biomarkers in the association between serum copper and sarcopenia

This study aims to investigate the association between serum copper (Cu), selenium (Se), zinc (Zn), Se/Cu and Zn/Cu ratios and the risk of sarcopenia. In this study, which involved 2766 adults aged ≥ 20 years enrolled in the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2016, multivariable logistic regression, restricted cubic spline (RCS) models and mediation analyses were used. After full adjustment, multivariable logistic regression revealed that higher serum copper levels were correlated with an increased risk of sarcopenia. Conversely, higher serum Se/Cu (OR 0.45, 95% CI 0.23–0.89, P = 0.023) and Zn/Cu (OR 0.49, 95% CI 0.27–0.90, P = 0.024) were associated with a decreased risk of sarcopenia. The RCS curve indicated a non-linear, roughly inverted L-shaped relationship between serum Cu and sarcopenia risk (P non-linear < 0.001). Additionally, Se/Cu (P non-linear = 0.179) and Zn/Cu (P non-linear = 0.786) showed negative linear associations with sarcopenia risk. Furthermore, white blood cell (WBC) count, neutrophil count, and systemic inflammation index (SII) were identified as significant mediators in the relationship between serum Cu and the risk of sarcopenia, with mediation proportions of 6.34%, 6.20%, and 4.37%, respectively (all P < 0.05). Therefore, balancing essential trace metals is crucial for maintaining muscle health.

Land-derived metals impact the survival and settlement of larval mussels.

Global declines in wild mussel populations and production have been linked to the impacts of climate change and pollution. Summer die-offs of mussels (Perna canaliculus), spat retention issues, and a severe decline in mussel spat settlement have been reported in the Marlborough Sounds, an important area for mussel farming in New Zealand. Preliminary evidence suggests that naturally occurring contaminants and changing land use in the surrounding areas, could contribute to the decline of this species. The aim of this study was to determine whether trace metals affect the larval survival and settlement of mussels. Concentrations of trace elements in surface waters, mussel gill tissues and sediments were characterized across the Marlborough Sounds. Over a two-year period, diffusive gradients in thin film (DGT) passive samplers were deployed at three locations, to estimate trace metal levels in the water column. Mussel gills and sediment were also collected to complement metal monitoring. Lead and zinc were the most abundant bioavailable metals detected during in-situ monitoring, with strong temporal variability. Ecotoxicity thresholds affecting P. canaliculus embryo-larval development and settlement were determined for these metals and overlapped with levels of lead and zinc found in the field during the reproductive season of mussels. Furthermore, high concentrations of zinc and lead in waters were strongly correlated with rain events, suggesting land runoff in the surrounding catchments as their main source. We hypothesize that vulnerable early life stages of mussels are exposed to these metals, especially following summer rainfalls, delivering pulses of these metals into the environment while triggering mussel spawning events. Climate-associated stressors (intense storms, marine heatwaves, freshwater and sedimentation inputs, acidification) are likely to exacerbate any toxic effects from land-derived inputs; a better understanding of these complex interactions is essential to prevent further P. canaliculus recruitment declines occurring in NZ, and in other mussel species globally.

Organic ligands in whale excrement support iron availability and reduce copper toxicity to the surface ocean

Nutrient recycling by marine megafauna is a key ecosystem service that has been disturbed by anthropogenic activity. While some hypotheses attribute Southern Ocean ecosystem restructuring to disruptions in micronutrient cycling after the elimination of two million great whales, there is little knowledge of trace metal lability in whale excrement. Here we measured high concentrations of dissolved iron and copper in five baleen whale fecal samples and characterized micromolar levels of organic metal-binding ligands as a proxy for their availability. The iron-ligand pool consisted of weakly-binding ligands and intermediate-binding ligands which enhanced iron stability and potential bioavailability. In comparison, 47 novel strongly-binding metallophores dominated copper-binding, curtailing its potential toxicity. These results illustrate how marine megafauna transform prey biomass into highly-labile micronutrients that they inject directly into the surface ocean, a mechanism whaling reduced by over 90%. Thus, the rapid restructuring of pelagic ecosystems through overharvesting may cause large biogeochemical feedbacks, altering primary productivity and carbon sequestration processes in the ocean.

Compositional heterogeneity of secondary minerals in mine waste rock: Origins and implications for water quality.

Secondary minerals in mine waste materials impose strong controls on water quality by scavenging solutes of concern. This study investigates the mineralogical and compositional characteristics of secondary Fe(oxy)hydroxides and Ca-sulfates, two globally ubiquitous secondary precipitates, in weathered mine waste rock. Bulk analyses show that Si, Ca, Fe, Al, and S-bearing primary phases were the most abundant in the entire samples, but up to a few wt% of secondary Fe(oxy)hydroxides and Ca-sulfates were present as well. In these secondary phases, trace metal impurities like V (37 mg/kg in Ca-sulfates), Cr (23 mg/kg in Fe-oxides and 21 mg/kg in Ca-sulfates), and Cd (up to 15 mg/kg in Fe-oxides and Ca-sulfates) could not be detected by bulk techniques (XRF and XRD), but their deportment to some extent characterized by automated mineralogy, and their spatial distribution assessed at high-resolution through microscale LA-ICP-MS analysis. Element mapping revealed that metal(loid)s were generally enriched at grain rims, reflective of peripheral sequestration through surface adsorption. An exception was V, which was uniformly distributed in the studied secondary Fe-oxides, suggestive of isomorphic substitution during co-precipitation. Factor analysis revealed distinct groups of elements co-associated within each secondary mineral (e.g., divalent transition metal cations versus oxyanionic metalloids), likely caused by similar primary mineral sourcing or a comparable sequestration mechanism. Our results demonstrate the importance of secondary mineral precipitates for scavenging (trace) elements and the insights that can be gained from complementary mineralogical and element analyses for the interpretation of trace element dynamics in waste rock.

Impacts of seasonality on mercury concentrations, polyunsaturated fatty acids, and stable isotopes: implications for the use of tetragnathid spiders as sentinels.

Riparian spiders are used in ecotoxicology as sentinels of bioavailable contaminants that are transferred from aquatic to terrestrial habitats via emergent aquatic insects. Spiders in the family Tetragnathidae are particularly of interest because a high proportion of their diet consists of emergent aquatic insects and their contaminant loads reflect the amount transferred through the food web to riparian predators. The transfer of contaminants can be determined through food web tracers such as stable isotopes and polyunsaturated fatty acids; however, it is unclear how contaminants and tracers vary over the course of a year. The objective of this study was to determine whether seasonality affected size, carbon and nitrogen stable isotopes, polyunsaturated fatty acid biomarkers, mercury, and other trace metal concentrations in tetragnathid spiders. Spiders were sampled fortnightly from a single site on the Stones River in Tennessee, USA, for an entire active season (April through October). Spider mass and length steadily increased from April to September to a maximum average value of 0.078 ± 0.03 g, then decreased in October. Seasonal trends were observed for carbon and nitrogen stable isotopes, with significantly decreased signatures occurring late in the active season. Overall, methyl mercury concentrations (range: 12.1-134.4 ng/g) and the methyl-total mercury ratio (range: 49%-98%) increased throughout the active season, with higher variability observed at the end of the active season. Collectively, our results indicate that seasonality affected several important endpoints and that spiders collected during the end of the active season may not be representative of spiders during the entire active season.

Plasticity of metamorphic traits in the Asiatic toad Bufo gargarizans: interactive effects of food quality and zinc pollution

Organisms with complex life cycles, like amphibians, are greatly affected by environmental factors and maternal effects, which in turn influence their morphological variation. The Asiatic toad Bufo gargarizans is found throughout East Asia and is not only valued for its economic medicinal properties in China but also considered a potential indicator species for assessing environmental pollution in inland rivers. However, the specific responses of this species to environmental toxicants, including trace metals, are not well comprehended at present. In this study, we experimentally examined the plasticity in larval period, body mass and size, and survival at metamorphosis in tadpoles of B. gargarizans under different combinations of food quality and zinc (Zn). We found that larval period, survival, SVL and mass at metamorphosis were sensitive to food quality, larval period increased significantly with increasing Zn concentration. The interaction between food quality and zinc primarily influenced the larval period. Tadpoles that were fed a high-energy diet, rich in protein and lipids, tended to have a shorter larval period as zinc concentration increased. Conversely, tadpoles fed a low-energy diet had a longer larval period with increasing zinc concentration. Thus, zinc plays a role in determining the extent to which food quality affects development of B. gargarizans. Additionally, larvae that consume a low-energy diet tend to have higher survival rates as zinc concentration increases, suggesting that moderate levels of zinc concentration (below 150 μg/L) are beneficial for normal physiological and biochemical processes in these organisms. The findings from this study provide valuable insights into the toxicological responses of this species to trace metals, contributing to a better understanding of their impact. Keywords: Bufo gargarizans, acute toxic effect, zinc, interaction effects, age and size at metamorphosis, phenotypic plasticity

The dead can talk: Investigating trace element and organic pollutant exposure in mammalian roadkill under contrasting habitats.

Urban environments are exposed to a substantial range of anthropic pressures, including chemical exposure. While trace metals and legacy pollutants have been well documented, the extent of wildlife exposure to emerging contaminants has received little attention, in terrestrial mammals. Concentrations of trace elements (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Pb and Zn) and 48 organic pollutants (Polychlorinated Biphenyls: PCBs, Organochlorine Pesticides: OCPs, Polycyclic Aromatic Hydrocarbons: PAHs, phthalates and pyrethroid pesticides) were measured in tissues of European hedgehogs (Erinaceus europaeus) in southern Sweden. Road kills and carcasses collected in 2021 and 2022by citizen science participants were used to characterize the level, tissue distribution and composition of mixtures in liver, spines and teeth samples. Phthalate diesters and PCBs were the most prevalent compounds in liver samples, with mean concentrations (±SD) of 1090±681 and 284±231ngg-1 of dry weight, respectively. Bioaccumulation patterns were observed for some organochlorine compounds but were hampered by the small sample size. Trace element concentrations and tissue distribution were strikingly equivalent between tissue type and age-classes (juveniles and adults) of hedgehogs, except for a handful of elements (e.g., Pb, Al, As), but contamination profiles differed between habitat types. While no adverse health effects are expected to occur from the body burdens measured for most of the target analytes, concerns might be expressed for the exposure to PCBs, phthalates and some non-essential trace metals (e.g., lead >15μgg-1 dw), which were found at levels above or approximating toxic thresholds in mammal tissues. The present study demonstrates the suitability of road kills as an alternative approach for environmental monitoring and the relevance of nondestructive biomonitoring to evaluate endogenous exposure in hedgehogs and possibly other terrestrial mammals and humans.

Copper and zinc isotope fractionation during phototrophic biofilm growth.

Copper (Cu) and zinc (Zn) are two trace metals that exhibit both limiting and toxic effects on aquatic microorganisms. However, in contrast to good knowledge of these metal interactions with individual microbial cultures, the biofilm, complex natural consortium of microorganisms, remains poorly understood with respect to its control on Cu and Zn in the aquatic environments. Towards constraining the magnitude and mechanisms of Cu and Zn isotope fractionation in the presence of phototrophic biofilms composed of different proportion of diatoms, green algae and cyanobacteria, we studied long-term growth in a rotating annular bioreactor and quantified the uptake of metals and their isotope fractionation at environmentally-relevant Cu and Zn concentrations. An enrichment of the biofilm in heavy Cu isotope at the beginning of growth suggests the dominance of adsorption processes, followed by intracellular uptake leading to progressive enrichment in light isotope and an excretion of heavy isotope, likely linked to Cu(II) reduction. In the case of Zn, we evidenced only weak isotope fractionation which implies the presence of heavier isotope adsorption (notably in the case of cyanobacteria-dominated biofilm) followed by intracellular incorporation of lighter isotopes. The microbial community plays important role in overall magnitude and even direction of fractionation, suggesting sizable complexity of the processes controlling metal isotope fractionation during phototrophic biofilm growth. However, Cu and Zn isotopes during long-term metal accumulation in riverine biofilm can be used for monitoring the source of environmental pollution in aquatic systems, provided that variations within different sources exceed the natural isotopic fractionation between the biofilm and aqueous solution.

Widespread presence of metallic compounds and organic contaminants across Pacific coral reef fish.

Coral reef fishes represent an invaluable source of macro- and micro-nutrients for tropical coastal populations. However, several potentially toxic compounds may jeopardize their contribution to food security. Concentrations of metallic compounds and trace elements (MTEs), and persistent organic pollutants (POPs, including pesticides and polychlorobiphenyls PCBs), totalizing 36 contaminants, were measured in coral reef fish from several Pacific islands. The objective of this study was to describe the spatial distribution of these compounds and contaminants in order to identify potential variables explaining their distribution at a Pacific-wide scale. To achieve this, we applied Boosted Regression Trees to model species-specific and community-level contaminant and inorganic compound concentrations at the scale of the tropical Pacific Ocean. Overall, using 15 easily accessible explanatory variables, we successfully explained between 60 and 87% of the global variation, with fish body size being the most important correlate of MTEs and POPs concentrations in reef fish. Our modeling approach allowed us to estimate and map the distribution of the community-level concentration of 19 contaminants and inorganic compounds at the scale of the equatorial and south Pacific Ocean. Spatial patterns varied significantly depending on the compound, with modeled quantities per 100g of fish flesh generally being higher in the central and southwest Pacific than in the eastern part of the basin. These patterns were influenced by a combination of biological, environmental, anthropogenic and biogeographical variables. Overall, this approach represents an important step toward the estimation of concentrations of the main compounds on the basis of species identity and fishing location. Our results enhance our understanding of the extent of contamination in the Pacific while underscoring the urgent need for long-term and large-scale spatial monitoring of diverse compounds in this region.

Enhanced emission spectra from flame-assisted LIBS for high-sensitivity detection of Pb in water

The flame-assisted method significantly enhances LIBS signal intensity, and the combination with dry droplet pretreatment improves the sensitivity for analyzing trace metal elements in water.

4D-printed programmable sample-/eluent-actuated solid-phase extraction device for trace metal analysis.

To integrate valves, manifolds, and solid-phase extraction (SPE) columns into a compact device is technically difficult. Four-dimensional printing (4DP) technologies, employing stimuli-responsive materials in three-dimensional printing (3DP), are revolutionizing the fabrication, functionality, and applicability of stimuli-responsive analytical devices that can show time-dependent shape programming to enable more complex geometric designs and functions. However, 4D-printed stimuli-responsive actuators and valves utilized to control flowing streams in SPE applications remain rare. The tunable stimuli-responsive 4D-printed flow control actuators and valves with the capability of the programmable actuation can be used to manipulate flowing streams and simplify the automation of a conventional SPE scheme. We employed digital light processing three-dimensional printing (3DP), bisphenol A ethoxylate dimethacrylate-based photocurable resins, and 2-carboxyethyl acrylate (CEA)-incorporated flexible photocurable resins to fabricate an SPE column positioned between two [H+]-responsive flow-actuated needle valves. The two valves sequentially close after loading an alkaline sample (pH>pKa of CEA) due to swelling of the stem. Subsequently, they sequentially open upon loading an acidic eluent (pH<pKa of CEA; deswelling of the stem). The optimized device enabled a semi-automatic SPE scheme for Mn, Co, Ni, Cu, Zn, Cd, and Pb ions and showed competitive performance when coupled with inductively coupled plasma mass spectrometry-with the method detection limits ranging from 0.5 to 5.9ngL-1. We validated the reliability and applicability of this method by analyzing the metal ions in reference materials (CASS-4, SLRS-5, 1643f, and Trace Elements Urine L-2) and spike analyses of natural water and human urine samples. To the best of our knowledge, our device is the first demonstration of an SPE scheme performed by the programmable actuation of 4D-printed stimuli-responsive flow control valves, highlighting the analytical applicability of the tunable stimuli-responsive 4D-printed parts and the promising capability of 4DP technologies in advancing conventional sample pretreatment devices.

Investigating the Formation of Trace Metal Contamination in Insulating Oil: From Electrical Erosion and Chemical Corrosion Perspectives

Investigating the Formation of Trace Metal Contamination in Insulating Oil: From Electrical Erosion and Chemical Corrosion Perspectives

Modeling the global ocean distribution of dissolved cadmium based on machine learning-SHAP algorithm.

Cadmium (Cd) is a bio-essential trace metal in the ocean that can be toxic at high concentrations, significantly impacting the marine environment and phytoplankton growth. Its distribution pattern is closely proportional to that of phosphate (PO4), although the mechanism is not fully understood. At low concentrations, evidence indicates Cd is able to act as an enzyme cofactor in biological processes. An understanding of the spatial distribution of dissolved cadmium (dCd) remains lacking and is constrained by the limitations of current observational data. Based on the observational data, this study applied advanced machine learning methods to reconstruct a global dataset of dCd, aiming to improve the accuracy and comprehensiveness of dCd cycling analyses. A comparison of five machine learning algorithms (artificial neural network, support vector machine, Lasso regression, k-nearest neighbors, and random forest) found that the random forest model showed the best performance (Rsq=0.99, RMSE=0.035nmolkg-1, MAE=0.019nmolkg-1, MAPE=0.345), reducing bias by 25% compared to previous studies. Using SHapley Additive exPlanations approach (SHAP), this study explored the factors influencing the dCd distribution at various depths and discussed the potential causes of changes in the Cd-PO4 relationship. The results showed that the temporal and spatial variability of Cd was influenced by surface biological processes, deep-sea mineralization, and seawater stratification. Variations in the Cd-PO4 relationship were linked to differences in biological fractionation inside and outside high-nutrient, low-chlorophyll (HNLC) regions, as well as the mixing of water masses with different Cd:PO4 ratios. Further analysis indicated that >80% of particles degraded into Cd and PO4 were produced in HNLC regions. This study highlights the broad potential of machine learning in oceanography, offering a global perspective on Cd cycling and new insights into the mechanisms driving element cycling.

Ecological quality assessment of estuarine macrobenthic communities using an integrative approach

Macrobenthic communities play a crucial role in the functioning of estuarine ecosystems and serve as bioindicators of environmental quality. This study assessed the ecological quality of an estuarine system using the AMBI and M-AMBI indices. The following parameters were considered: (i) environmental factors (total organic matter, organic carbon, grain size, calcium carbonate), (ii) sediment trace metals (Pb, Zn, Cu, Cr, Co, Ni, Hg, Li, As), (iii) species composition (morphological and molecular identification), and (iv) anthropogenic activities. The results demonstrated notable differences between study areas, reflecting hydrodynamic processes and human activities. The AMBI index indicated that all areas exhibited conditions classified as “slightly disturbed.” However, the composition of the ecological groups and M-AMBI results differed according to the identification method. This approach allowed for a more complete understanding of communities, by integrating the influence of anthropogenic activities on the sediment and macrobenthic communities, highlighting the importance of using both identification methodologies.

Mechanisms activating trace heavy metals in the rhizosphere microenvironment of Amaranthus hypochondriacus L.

Soil heavy metal activation is closely related to rhizosphere soil pH, O2 and enzyme activity levels. In this study, we used laser ablation inductively coupled plasmamass spectrometry (ICPMS), planar optode (PO), soil in situ enzyme spectrum analysis, and the diffusive gradients in thin films (DGT) method to investigate heavy metal accumulation in Amaranthus hypochondriacus L. growing in polluted soil (Cd, Pb and Zn) and unpolluted soil, as well as dissolved oxygen (DO), pH, soil enzyme activity, and trace heavy metal dynamics in rhizosphere and nonrhizosphere soils. The results revealed that the growth of A. hypochondriacus was significantly inhibited under combined Cd, Pb, and Zn stress, with the most pronounced effects on root and branch biomass. Radial oxygen loss (ROL) and alkalization occurred in the roots of A. hypochondriacus, which were influenced primarily by root growth and environmental conditions. The enzyme activity patterns indicated that acid phosphatase (ACP), alkaline phosphatase (ALP), and β-glucosidase (BG) activities were primarily associated with the root system and that the activities of these enzymes were relatively low in nonrooted soil. Under heavy metal stress, the ACP, ALP and BG activities in the hotspots of soil increased. DO, pH, and soil enzyme activity were significantly correlated with the presence of heavy metals Cd, Pb, and Zn, influencing the mobilization mechanisms of trace metals in the rhizosphere. These findings lay the groundwork for understanding the impact of root-induced alterations in O2, pH, and soil enzyme activity on the mobility of trace heavy metals in soil.

Active biomonitoring of river pollution using an ex-situ exposure system with two model species.

In the context of increasing pollution pressure on aquatic ecosystems, it is essential to improve our knowledge of habitat quality and its suitability for organisms. It is particularly relevant to better integrate early life stages of fish into pollution biomonitoring programs, as they are reliable indicators of ecosystem integrity and because of their high sensitivity to pollutants. To avoid the influence of environmental parameters on their development, a lab-on-field approach, called the ex-situ exposure method, was developed. Aquatic organisms were exposed to a continuous flux of water under semi-controlled temperature, oxygen, and photoperiod conditions to avoid the influence of these confounding factors when interpreting the results. To investigate the potential role of water contamination, this active biomonitoring method was applied to the Garonne River (Southwest France), where migratory fish populations have declined. Two model species from different taxa were used: embryos of the Japanese medaka (Oryzias latipes) and adults of the crustacean Gammarus fossarum. The results showed a significant impact of water quality on embryo mortality and early hatching in two separate experiments on Japanese medaka. In addition, an induction of feeding rate was observed in exposed gammarids, but no impact on their embryo survival, suggesting differences in sensitivity between the two species selected. Chemical and biological analyses did not identify trace metals, pesticides, or microorganisms as potential sources of toxicity in medaka embryos or G. fossarum. These results raise concerns about the quality of the water in the Garonne River and its toxicity to aquatic organisms.