Bioconcentration Research Articles

Effect of Co-exposure to Additional Substances on the Bioconcentration of Per(poly)fluoroalkyl Substances: A Meta-Analysis Based on Hydroponic Experimental Evidence.

A consensus has yet to emerge regarding the bioconcentration responses of per(poly)fluoroalkyl substances under co-exposure with other additional substances in aqueous environments. This study employed a meta-analysis to systematically investigate the aforementioned issues on the basis of 1,085 published datasets of indoor hydroponic simulation experiments. A hierarchical meta-analysis model with an embedded variance covariance matrix was constructed to eliminate the non-independence and shared controls of the data. Overall, the co-exposure resulted in a notable reduction in PFAS bioaccumulation (cumulative effect size, CES = - 0.4287, p < 0.05) and bioconcentration factor (R2 = 0.9507, k < 1, b < 0) in hydroponics. In particular, the inhibition of PFAS bioconcentration induced by dissolved organic matter (percentage form of the effect size, ESP = - 48.98%) was more pronounced than that induced by metal ions (ESP = - 35.54%), particulate matter (ESP = - 24.70%) and persistent organic pollutants (ESP = - 18.66%). A lower AS concentration and a lower concentration ratio of ASs to PFASs significantly promote PFAS bioaccumulation (p < 0.05). The bioaccumulation of PFASs with long chains or high fluoride contents tended to be exacerbated in the presence of ASs. Furthermore, the effect on PFAS bioaccumulation was also significantly dependent on the duration of co-exposure (p < 0.05). The findings of this study provide novel insights into the fate and bioconcentration of PFAS in aquatic environments under co-exposure conditions.

Novel insights into the mechanisms of bioaccumulation and tissue-specific distribution of hexafluoropropylene oxide homologues, novel PFOA alternatives, in zebrafish (Danio rerio)

Hexafluoropropylene oxide trimer acid (HFPO-TA) and hexafluoropropylene oxide tetramer acid (HFPO-TeA) are two novel alternatives of perfluorooctanoic acid (PFOA). However, their toxicokinetics and accumulation mechanisms in fish are still unknown. This study provides the first line of in vivo uptake and depuration kinetic, bioaccumulation mechanism and tissue-specific distribution for HFPO-TA and HFPO-TeA, upon a 28-day water exposure and a 14-day depuration in zebrafish (Danio rerio). HFPO-TeA and HFPO-TA could quickly accumulate in zebrafish, and the highest concentrations of HFPO-TeA (15.4 ± 1.6 nmol/g ww), HFPO-TA (4.95 ± 0.19 nmol/g ww) and PFOA (0.47 ± 0.03 nmol/g ww) were consistently present in the blood, which was followed by liver, kidney, intestine, gill, gonad and brain, while the lowest were observed in the muscle (1.01 ± 0.11, 0.16 ± 0.02, and 0.01 ± 0.001 nmol/g ww, respectively), indicating both higher accumulation potentials of both HFPO homologs than their predecessor PFOA. The tissue protein content, rather than lipid content, played an enhancing role in the enrichment of three target chemicals, exhibiting a significant positive correlation (r = 0.735, p = 0.038 for HFPO-TeA; r = 0.770, p = 0.026 for HFPO-TA and r = 0.942, p = 0.001 for PFOA) between the tissue bioconcentration factor (BCF) and the protein contents in corresponding tissues. This phenomenon was validated by the equilibrium dialysis experiment, molecular docking analysis and molecular dynamics simulation, which consistently indicated that the binding affinities of serum and liver proteins were greatest with HFPO-TeA, followed by HFPO-TA and least with PFOA. These results suggested that the binding of the target chemicals to specific proteins determined their tissue-specific accumulation potentials. Nontarget screening by high resolution mass spectrometry (HRMS) did not identify suspicious degradation products for HFPO-TA, implying the strong persistence of HFPO-TA in fish.

The Bioaccumulative Potential of Heavy Metals in Five Forest Species Living in Mining Environments in the Ecuadorian Amazon Region.

Heavy metal contamination of soils and ecosystems is an environmental problem that requires urgent attention due to the ecological problems that it generates. Forest species can be used to mitigate contamination because of their potential to bioaccumulate contaminating metals. The objective of this work was to evaluate the bioaccumulator potential of heavy metals in five forest species that live in mining environments in the Ecuadorian Amazon region. The bioconcentration factor for five forest species, such as: Cedrela odorata, Parkia multijuga, Inga edulis, Cecropia ficifolia and Pourouma cecropiifolia, commonly found in the Ecuadorian Amazon was analysed, based on the relationship between the concentration of the heavy metal in leaves and the soil. Atomic absorption spectrometry was used to analyse heavy metals in leaves and soil samples of each plant specie. The results showed that P. cecropiifolia had the highest bioconcentration factor for lead, C. odorata for cadmium and nickel, and I. edulis had the highest potential for iron and aluminium absorption. No correlation was found between the concentration of each element in the soil and the leaves, which shows that the bioaccumulation capacity of the species studied does not depend on the concentration of the element in the soil. This provides relevant information for the inclusion of these species for phytoremediation purposes.

Evaluation of the growth, enzymatic activity, electrolyte leakage, and phytoremediation efficiency of Conocarpus erectus under cadmium and lead stress.

Contamination of agricultural soil by heavy metals poses a significant threat to soil quality and crop yields. Using plants as a natural remediation approach attracts researchers' attention around the world. A 16-month pot experiment was conducted using Conocarpus erectus in a randomized complete block design. The growth, enzymatic activity, electrolyte leakage, and remediation potential were estimated under Cd nitrate]40 low (L), 60 medium (M), 80 high (H) mg/kg soil [and Pb nitrate]400 (L), 700 (M), 1,000 (H) mg/kg soil [applied individually and in combination. Conocarpus erectus demonstrated a good tolerance (over 70%) against lower and medium cadmium (Cd) and lead (Pb) levels and a medium resistance against high Cd and Pb levels, with a survival rate of 100% under all the treatments used. The most negative treatment on the growth traits and tolerance of C. erectus was (H) Cd and (H) Pb, which reduced plant height; chlorophyll index; dry weights of the leaves, stems, and roots; root length; and tolerance index of biomass and roots by 25.87%, 48.97%, 50.56%, 47.25%, 58.67%, 50.18%, 51.00%, and 50% in comparison to the respective control, consecutively. Relative to the control, all Cd and Pb applications increased polyphenol oxidase (PPO), peroxidase (POD), and catalase (CAT) activities, and the increment was parallel up to medium Cd and Pb levels and then decreased with their high levels but still higher than the control. Electrolyte leakage (EL) was upheaved by raising the levels of Cd and Pb, and it reached the maximum (52.79%) at the (H) Cd (H) Pb treatment. Cd and Pb in the leaves, stems, and roots were boosted by raising their levels in the treatments. Conocarpus erectus is considered a phytoextractor for the Cd levels used because the bioconcentration factor of the stem (BCFs) and the translocation factor (TF) of Cd were >1, and it is a suitable plant for Pb phytoextraction at (L) Pb, (M) Pb, and (M) Cd (M) Pb levels because its Pb BCFs and bioconcentration factor of the root (BCFr) were <1 and its Pb TF was >1. On the other hand, C. erectus is considered a phytostabilizator for Pb at (H) Pb, (L) Cd, (L) Pb, and (H) Cd (H) Pb levels because its Pb BCFs, BCFr, and TF were <1.

Combining SiO2 NPs with biochar: a novel composite for enhanced cadmium removal from wastewater and alleviation of soil cadmium stress.

Cadmium (Cd) pollution in water and soil seriously threatens human health. Biochar and nanomaterials have high potential for solving the cadmium pollution problem due to their abundant pores and high specific surface area. Here, the preparation of the composite material SiO2NPs@BC (SBC) using SiO2 NPs (SN) and silkworm excrement biochar (BC) is described, along with its application in the remediation of cadmium-contaminated water and soil. Characterization experiments (SEM&EDS, BET, FTIR, XRD, and XPS) demonstrated that SiO2NPs@BC has a high specific surface area (46.5767m2/g), a well-developed pore structure (0.608375cm3/g), and abundant surface functional groups (Si-C, Si-O, Si-O-Si), providing active sites for the adsorption of Cd. Batch adsorption experiments in water showed that the adsorption capacity of SBC is higher than that of biochar (BC) and SN, with a maximum Langmuir adsorption capacity of 141.99mg/g. After five adsorption cycles, the removal rate of SBC was 73.04%, significantly higher than the 64.97% obtained for BC. The application of SBC not only improved the soil physicochemical properties by increasing the soil pH, the cation exchange capacity, and the soil organic matter content but also by reducing the amount of DTPA-Cd (24.6%) and the plant bioconcentration factor (28.28%) in the soil, converting Cd into more stable fractions (Red-Cd, Ox-Cd). Based on the results, SBC can effectively reduce Cd pollution.

First national mapping of cadmium in cacao beans in Colombia

Cacao crops in Colombia play a fundamental role in its economy. Cacao bean exports have a rising tendency due to increased area and production. However, cadmium (Cd) in cacao beans has affected market in Colombia. The aim of this study is to assess Cd distribution hotspots for cacao beans, Cd in beans and soil relationships, geological ages and soil chemical parameters, overall Cd dynamics, soil-to-plant translocation, and EU regulation impacts on Cd presence in Colombian cacao production. A hot and cold spot analysis combined with a cluster and outlier analysis was used to build the geographic Cd distribution in cacao beans in Colombia. Cadmium in the subsurface and the relationship with Cd in the soil surface of cacao farms were analysed using the geoaccumulation index (Igeo). The bioconcentration factor (BCF) and soil chemical features in cacao beans were quantified. Positive correlations were observed within all the studied variables except for Mn and Fe. The highest correlation was observed within Ca, pH, and Cd in soil. The Valanginian-Albian and Albian-Maastrichtian geological ages are directly related to Cd in beans, Zn, P, soil Cd, and Fe. Regions with the highest cacao productivity and export registered an average Cd concentration in beans of 2.39_ ± _2.82 mg kg−1. Two municipalities in Santander were ‘partially contaminated’ according to Igeo. The BCF was not directly proportional to soil and bean Cd level and did not fully coincide with hot spots. This evidence reinforces the idea that even areas with apparently low Cd levels may register a latent problem associated with genetic/ontogenetic, climatic, or management factors. This first distribution map of Cd in cacao beans constitutes a tool to implement actions to minimize risks and face challenges posed by the imposed regulations that may limit raw cacao bean exports in Colombia.

Machine learning and structural equation modeling for revealing the influence factors and pathways of different water management regimes acting on brown rice cadmium

Excessive cadmium (Cd) in brown rice has detrimental effects on rice growth and human health. Water management is a cost-effective, eco-friendly measure to suppress Cd accumulation in rice. However, there is no acknowledged water management regime that reduces Cd accumulation in brown rice without compromising the yield. Meanwhile, the major factors affecting brown rice Cd and the pathways of water management affecting rice Cd are not clear. This study explored major factors affecting brown rice Cd using machine learning (ML) and examined the pathways of water management affecting rice Cd using a structural equation model (SEM). Three water management systems were set up, namely flooding, water-saving, and wetting irrigation. Results showed that water-saving irrigation increased dry matter and reduced Cd content and translocation. Root uptake during the grain filling stage and Cd remobilization before the grain filling stage contributed 36 % and 64 % of the Cd accumulation in brown rice, respectively. ML explained 97 % of the variance, suggesting that crop covariates were the most important (e.g., the brown rice bioconcentration factor (12 %), stem Cd (9 %), root-to-stem translocation factor (7 %)), followed by soil covariates (e.g., reducing substances 12 %) and water management (3 %). All SEM explanatory variables collectively explained 94 % of the variation, with a predictive power of 76 %. Water treatments indirectly affected soil available Fe and Mn (indirect effect coefficient = 0.909), iron plaques (indirect effect coefficient = 0.866), soil available Cd (indirect effect coefficient = −0.671), and Cd intensity of xylem sap (BICd, indirect effect coefficient = −0.664) via pH and reducing substances. BICd significantly positively affected stem Cd (path coefficient = 0.445). These findings provide insight into the agronomic and environmental effects of water management on brown rice Cd and influence pathways in soil–rice systems, suggesting that water-saving irrigation may alleviate Cd contamination in the paddy soil.

Assessment of trace element occurrence in Nile Tilapia from the Rosetta branch of the River Nile, Egypt: Implications for human health risk via lifetime consumption

River pollution can harm human health through direct contact, drinking water, and the consumption of contaminated fish and irrigated agricultural products. Surface water and Nile tilapia (Oreochromis niloticus) samples were collected monthly from July 2022 to June 2023 at three sites (El-Rahawy, Sabal, and Tala) along the Rosetta Nile branch in Egypt to monitor the presence of eight trace elements. The potential human health risks from consuming contaminated fish were also assessed. Iron and manganese were consistently detected in all water samples across most seasons and locations, with concentrations generally below the WHO permissible levels. All 72 analyzed fish muscle samples were found to contain trace elements. The mean concentrations of metals in the fish muscle samples, in descending order, were: iron > zinc > copper > manganese > tin > antimony > lead > mercury. Significant spatial and seasonal variations were observed in both water and fish samples. El-Rahawy was identified as the most contaminated site, with summer exhibiting the highest contamination rate compared to other seasons. Fish samples collected from El-Rahawy demonstrated the highest bioconcentration factor (BCF) values for most elements, particularly mercury, lead, iron, manganese, and antimony. Target hazard quotient (THQ) calculations for the trace elements in Nile tilapia muscles revealed that all trace elements, except antimony, had THQ values below 1, suggesting that consuming Nile tilapia from these sites is unlikely to cause adverse health effects. However, THQ values for antimony exceeded the threshold of 1, indicating a potential health risk for consumers. Although the detected trace elements in the fish were below the permissible toxicity limits, some could pose a future threat to human health, necessitating further studies, ongoing monitoring, and preventive measures.

Effects of Organic Manure on Wheat Yield and Accumulation of Heavy Metals in a Soil—Wheat System

The application of organic manure is an effective way to develop sustainable agriculture. However, the application of organic manure may be associated with a potential risk of heavy metal pollution for soil and crops. In this study, the effects of organic cow manure (T1) (as base fertilizer), organic pig manure (T2) (as base fertilizer) and chemical fertilizer (T3) on winter wheat grain yields, grain quality, heavy metal concentrations and heavy metal bioconcentration factors (BCFs) in a soil–wheat system were studied from November 2021 to June 2023. The results showed that the winter wheat grain yields in the T1 and T2 treatments were lower than those in the T3 treatment by 2.57–38.0% and 10.5–25%, respectively. There were no significant differences in quality indexes of winter wheat grain among different fertilizer treatments. The concentrations of heavy metals in topsoil and winter wheat were 0.12–76.11 μg/g and 0.01–43.25 μg/g, respectively. The BCFs of heavy mental in the soil–wheat grain system was 0–2.92. In general, there were no significant differences in heavy metals’ concentrations in topsoil and wheat grain among different fertilizer treatments. In summary, compared with chemical fertilizer, the short-term application of organic manures had no significant effect on heavy metals concentrations in topsoil and wheat.

Butterfly species vary in sex‐specific sodium accumulation from larval diets

Abstract Sodium is essential for animals, and its heterogeneous distribution can cause a range of phenomena, from sodium‐seeking behaviours to impacting their performance. Although sodium content in soils and plants is relatively well documented, data for higher trophic levels are limited. Knowledge of the variation in sodium in lower trophic levels could have implications for understanding the behaviour and physiology of species at higher levels. We investigated the variation in tissue sodium concentration between males and females of four butterfly species. Puddling behaviour of Lepidoptera suggests sodium needs of males are generally greater than females, thus, we predicted males would accumulate more sodium than females on a given diet. Larvae were reared on plants (for Battus philenor, Chlosyne lacinia and Danaus plexippus) and an artificial diet (for Pieris rapae) under Low Na (no added sodium) and High Na (sodium added) conditions. Among species and sexes, we quantified and compared adult absolute tissue sodium concentrations and bioconcentration factors, which indicate net sodium accumulation or excretion relative to individuals' diets. On average, individuals on low‐sodium diets had higher bioconcentration values across all species. Male butterflies accumulated significantly higher sodium concentrations than females in two sodium treatments for B. philenor, and P. rapae and only in the High Na treatment for C. lacinia. However, in D. plexippus, individuals accumulate sodium in the High Na treatment, but males and females responded in the same way. Our study revealed sex‐ and species‐specific patterns of butterfly sodium accumulation, which could be linked to variations in behaviour and/or performance. Differences in sodium content across species have implications for variation in predation and trophic‐level interactions, an interesting avenue for future ecological and evolutionary research.

ACCUMULATION OF HEAVY METALS IN APPLES AND PEARS FROM THE SUBURBS OF MITROVICA, KOSOVO

Intake of heavy metals through the food is a food safety problem that seriously affects consumer health. Therefore, information is needed on the intake of food contaminated with heavy metals and their concentrations, to assess the potential risk for human health. This paper aims to determine the accumulation of metals in apples and pears grown in the surroundings of Kosovska Mitrovica (Republic of Kosovo) and the bioconcentration factor (BF). With the help of the ICP-MS technique, were determined the amounts of Cu, Fe, Co, Mn, Ni, and Cr in apples and pears grown in three regions - Zvečan , Frashër, and Polski. From the conducted tests, the highest concentrations in apples and pears were determined for iron (on average 100.67 mg/kg for apples and 107.4 mg/kg for pears) and the lowest concentrations for cobalt (on average 0.13 mg/kg for apples and 0.18 mg/kg for pears). The lowest bioconcentration factor in apples is 0.01 (for Fe, Co, and Mn in all three regions), and the highest is 0.32 (for Cr in Zvečan). When determining the bioconcentration factor in pears, the lowest (0.01) was determined for iron (in all three regions) and manganese (in Zvečan and Frashër regions), and the highest bioconcentration factor was determined for copper – 0.46 (Polski region). There is a very high correlation between the values obtained for the analyzed metals in apples and pears. According to BF values, pears extract twice as much Cu and Co from the soil compared to apples, and the extraction of other metals from the soil is the same for both types of fruit.

BIOACCUMULATION OF CU AND CO IN LEAFY AND FRUIT VEGETABLES FROM THE SUBURBS OF MITROVICA, KOSOVO

Contamination of vegetables with heavy metals is one of the basic environmental problems, especially in developing cities, primarily due to the uncontrolled level of pollution caused by industrial growth and the increase in the number of vehicles using petroleum fuels. This paper aims to determine the bioconcentration of heavy metals Cu and Co in leafy and fruit vegetables grown near Kosovska Mitrovica (Republic of Kosovo). Three places near Kosovska Mitrovica (Zvečan, Frashër, and Polski) are grown: parsley, spinach, lettuce, peppers, eggplant, and cucumber. All analyzed crops are from the 2023 harvest. In the same period, an analysis was made of the soil on which the crops were grown. The bioconversion factor (BF)of the selected leafy and fruit vegetables was also determined. The ICP-MS technique was used to determine the concentration of Cu and Co in soil and leafy and fruit vegetables. From the obtained analyzes it was determined that the soil in Frashër contains the highest amount of Cu and Co - 58.4 mg/kg and 11.6 mg/kg respectively. The amount of Cu in the examined dry leafy and fruit vegetables is in the range from 5.38 mg/kg to 22.4 mg/kg, and of Co from 0.27 mg/kg to 2.99 mg/kg. The bioconcentration factor of the studied leafy and fruit vegetables of Cu and Co is in the range of 0.04 to 0.26 and 0.15 to 0.65 respectively. The accumulation of Co in the analyzed vegetables is higher than the accumulation of Cu, due to the higher BF values for Co. The statistical processing of the results (t-test) showed that there is a difference in the concentration of Cu and Co between leafy and fruit vegetables, but there is no statistically significant difference because the obtained p-values are greater than the marginal p-values.

Potential use of gammarus (Pontogammarus maeoticus) and shrimp (Palaemon elegans) as biomonitors of microplastics pollution in coastal environments

Microplastics (MPs) pose a significant threat to marine ecosystems, necessitating robust biomonitoring to assess aquatic risks and inform effective policymaking. In this study we investigated MPs pollution in gammarus (Pontogammarus maeoticus), shrimp (Palaemon elegans), sediment and water samples of southern coast of the Caspian Sea to assess the potential use of these two crustaceans as biomonitors of MPs pollution, bioconcentration of MPs in organisms’ tissue and the pollution risks of MPs in environmental matrices. Samples were collected from 6 stations during June to August 2023. MPs were found in all compartments with an average of 100 ± 45.34 items/kg dry weight, 0.45 ± 0.06 items/L, 0.38 ± 0.21 items/individual or 0.58 ± 0.34 items/g wet weight (ww) and 0.26 ± 0.15 items/individual or 8.69 ± 7.88 items/g ww, for sediments, seawaters, P. elegans and P. maeoticus, respectively. MPs were prevailed by class 300−1000 μm in size, polyamide in polymer, fiber in shape and black in color. P. maeoticus and P. elegans did not meet the selection criteria as MPs biomonitors. However, bioconcentration factor (BCF) illustrated that both crustaceans can absorb and accumulate MPs from their surrounding water (BCF >1). Based on contamination factors (CF) values, sampling stations were polluted with MPs (1 ≤ CF < 6). The overall pollution load index (PLI) for sediment and seawater stations were 2.47 and 1.88, respectively, indicating minor contamination with MPs in the risk level I. Current research provides useful information on MPs pollution in crustaceans species and the risk level of MPs in environmental matrices that can be suitable for bioaccumulation hazard assessment and future monitoring programs.

Fertilized soils enhance the efficiency of phytoremediation by tropical grasses in cadmium-contaminated soils

The effectiveness of phytoremediation in Cd-contaminated soils is crucial for enhancing nutrient availability and plant tolerance to Cd. We simulated soil contamination with varying textures and fertilization conditions. Two experiments were conducted: one without liming and fertilization and another with soil fertilization for grasses. The soil types used were Oxisol and Entisol, and the grasses tested were Megathyrsus maximus and Urochloa brizantha at three Cd levels: 0 mg kg−1 (Control), 2 mg kg−1 (Low), and 12 mg kg−1 (High). Soil amendments and fertilization did not significantly change Cd availability. Soil chemical attributes were unaffected by Cd contamination but were influenced by fertilization, which kept the pH below optimal levels. Cd availability was higher in more contaminated soils, with Entisol showing greater concentrations than Oxisol. Dry matter production of the grasses decreased with higher contamination, with U. brizantha being more productive than M. maximus in fertilized soils. Cd accumulation was higher in highly contaminated soils, particularly for U. brizantha. The bioconcentration factor was higher in Entisol, while the translocation factor exceeded 1.0 only for M. maximus in low-contamination Oxisol. Fertilization can mitigate Cd contamination effects, with U. brizantha showing greater tolerance and accumulation capacity in fertilized soils.

Mediterranean mussels (Mytilus galloprovincialis) exposure to fluoxetine: Bioaccumulation and biotransformation products

The significant rise in antidepressant consumption in recent years was accentuated by COVID-19 pandemic. Among these antidepressant, fluoxetine, a selective serotonin re-uptake inhibitor (SSRI), is the most prescribed worldwide. The present study investigated its bioaccumulation and metabolization in the mussel Mytilus galloprovincialis, generally recognized as a reliable bioindicator for assessing environmental quality and the accumulation of various contaminants. Mussels were exposed to a nominal concentration of fluoxetine (3.1 μg/L) for 28 days. Mussels were sacrificed at day 2, 7, 14 and 28 of exposure. The order of accumulation level was gills > digestive glands > soft tissues, and a regular increase in fluoxetine and norfluoxetine was observed across the various sampling days for both digestive glands and soft tissues. The calculated bioconcentration factor (BCF) ranged from 253 at D2 to 1734 at D28 for fluoxetine, and pseudo-BCF from 7 at D2 to 64 at D28 for norfluoxetine. Non-targeted approaches highlighted ten metabolites, which are reported for the first time in Mytilus, in addition to norfluoxetine. Notably, this study highlighted two phase I metabolites and one phase II metabolite previously unreported. These findings contribute to the understanding of fluoxetine accumulation and metabolism in Mytilus and enhance the knowledge of pharmaceuticals detoxification processes in non-target organisms.

Invasive Amaranthus spp. for heavy metal phytoremediation: Investigations of cadmium and lead accumulation and soil microbial community in three zinc mining areas

Amaranthus spp. are a group of strongly invasive and vigorous plants, and heavy metal phytoremediation using alien invasive Amaranthus spp. has been a popular research topic. In this study, the bioconcentration factor (BCF) and translocation factor (TF) of Amaranthus spp. were evaluated, focusing on the accumulation potential of cadmium (Cd) and lead (Pb) by plants from three different zinc mining areas, namely Huayuan (HYX), Yueyang (LYX), and Liuyang (LYX). The HYX area has the most severe Cd contamination, while the LYX area has the most apparent Pb contamination. The results showed that Amaranthus spp. had a strong Cd and Pb enrichment capacity in low-polluted areas. To elucidate the underlying mechanisms, we used high-throughput sequencing of 16S rRNA and internal transcribed spacer (ITS) regions to analyze rhizosphere bacterial and fungal communities in three areas. The results showed significant differences in the structure, function, and composition of microbial communities and complex interactions between plants and their microbes. The correlation analysis revealed that some key microorganisms (e.g., Amycolatopsis, Bryobacterium, Sphingomonas, Flavobacterium, Agaricus, Nigrospora, Humicola) could regulate several soil factors such as soil pH, organic matter (OM), available nitrogen (AN), and available phosphorus (AP) to affect the heavy metal enrichment capacity of plants. Notably, some enzymes (e.g., P-type ATPases, Cysteine synthase, Catalase, Acid phosphatase) and genes (e.g., ZIP gene family, and ArsR, MerR, Fur, NikR transcription regulators) have been found to be involved in promoting Cd and Pb accumulation in Amaranthus spp. This study can provide new ideas for managing heavy metal-contaminated soils and new ways for the ecological resource utilization of invasive plants in phytoremediation.

Micronutrient and heavy metal bioaccumulation in Bermuda grass (Cynodon dactylon L. Pers) grown in calcareous soil using stabilized and dried sewage sludge

This study examines the micronutrients and heavy metal bioaccumulation in Bermuda grass (Cynodon dactylon L. Pers), grown in two different types of calcareous soil (CS) with the application of stabilized and dried sewage sludge (SS). At the end of the growth period, the Fe, Zn, Mn and Cu (micronutrients) concentrations in the substrate have increased. Furthermore, it was determined that the total Fe, Zn, Mn and Cu concentrations were higher in CS1 compared to CS2. For the heavy metals the concentrations of Ni and Cr have increased, and the concentration of total Cd has slightly but significantly decreased. The total Pb concentration was below the detection limit (DL for Pb &lt;0.03 mg kg-1). It was determined that the total Ni, Cr and Cd concentrations were higher in CS1 than in CS2. In the aerial biomass of the Bermuda grass, the Fe and Zn concentrations have increased with increasing SS applications, whereas Mn concentrations have decreased. Ni, Cr, Cd and Pb concentrations were unaffected by SS applications for both types of CS. The bioconcentration factor (BCF) values for the shoot of the plant (BCFFe, BCFZn, BCFMn, BCFCu, BCFNi, BCFCr, BCFCd) were determined to be below the critical limit of 1. The application of sewage sludge has not resulted in bioaccumulation above critical limits in the shoot of the plant. However, considering Bermuda grass substrate, it can be suggested to add sewage sludge to the calcareous soil in amounts between 20–40 t ha-1, considering its long-term remanence.

The Potential of Helichsryum splendidum (Thunb.) Less. for the Restoration of Sites Polluted with Coal Fly Ash.

The disposal of coal fly ash (CFA) generated from coal-fired power stations has serious impact on the ecosystem, by converting large pieces of land to barren ash dams with the potential to contaminate groundwater, surface water, air and soil. The aim of this study was to clarify the potential of phytoremediation using Helichrysum splendidum (Thunb.) Less. in areas polluted by CFA through conduction of pot trial experiments for 14 weeks. Plants of the same age were cultivated in CFA to assess their growth, photosynthetic rate and tolerance towards metal toxicity. This study revealed that the CFA was moderately polluted with heavy metals, and a lower photosynthetic rate was recorded for the CFA plants in comparison to the controls (plants grown in soil). Although the CO2 assimilation rate was lower for the CFA plants, increased growth was recorded for all the plants tested. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify the amount of trace elements in samples and parameters including translocation factor (TF) and bioconcentration factor (BCF) were used to evaluate the phytoremediation potential of H. splendidum (Thunb.) Less. The results revealed that higher concentrations of Cd, Co, Cr, Cu, Mn and Pb were accumulated in the roots, while As, Ni and Zn were found in the shoots. Elements including As, Cr and Zn reported TF values above 1, indicating the plants' phytoextraction potential. The BCF values for As, Cu and Zn were 1.22, 1.19 and 1.03, indicating effectiveness in the phytostabilization processes. A removal rate efficiency ranging from 18.0 to 56.7% was recorded confirming that, H. splendidum (Thunb.) Less. can be employed for restoration of CFA dams.

Effects of perfluoroalkyl sulfonic acids on developmental, physiological, and immunological measures in northern leopard frog tadpoles

The chronic toxicity of short chain perfluoroalkyl sulfonic acids (PFSAs), such as perfluorobutanesulfonic acid (PFBS) and perfluorohexanesulfonic acid (PFHxS), are relatively understudied despite the increasing detection of these compounds in the environment. We investigated the chronic toxicity and bioconcentration of PFBS and PFHxS using northern leopard frog (Rana [Lithobates] pipiens) tadpoles. We exposed Gosner stage (GS) 25 tadpoles to either PFBS or PFHxS at nominal concentrations of 0.1, 1, 10, 100, and 1000 μg/L until metamorphosis (GS42). We then assessed tadpole growth, development, stress, and immune metrics, and measured fatty acid (FA) composition and PFSA concentrations in liver and whole-body tissues. Tadpole growth and development measures were relatively unaffected by PFSA exposure. However, tadpoles exposed to 1000 μg/L PFBS or PFHxS had significantly increased hepatosomatic indexes (HSI) relative to controls. Further, tadpoles from the 1000 μg/L PFHxS treatment had altered FA profiles relative to controls, with increased total FAs, saturated FAs, monounsaturated FAs, and omega-6 polyunsaturated FAs. In addition, tadpoles from the 1000 μg/L PFHxS treatment had a higher probability of waterborne corticosterone detection. These results suggest that PFBS and PFHxS influence the hepatic health of tadpoles, and that PFHxS may alter lipid metabolism in tadpoles. We also observed a higher probability of tadpoles being phenotypically female after exposure to an environmentally relevant concentration (0.1 μg/L) of PFHxS, suggesting that PFHxS may exert endocrine disrupting effects on tadpoles during early development. The measured bioconcentration factors (BCFs) for both compounds were ≤10 L kg−1 wet weight, suggesting low bioconcentration potential for PFBS and PFHxS in tadpoles. Many of the significant effects observed in this study occurred at concentrations several orders of magnitude above those measured in the environment; however, our work shows effects of PFSAs exposure on amphibians and provides essential information for ecological risk assessments of these compounds.

Combined physiological, metabolomic and response surface approaches to analyze copper stress resistance mechanisms and repair potential of Epipremnum aureum

Phytoremediation is commonly used to remediate copper (Cu) pollution in water bodies. Epipremnum aureum is often used as a restoration plant because of its rapid reproduction, high population density and high landscape value. However, neither its ability to remediate Cu-polluted water nor its mechanism of resistance to Cu stress has been fully clarified. Therefore, the present study revealed the Cu removal ability and resistance mechanism of E. aureum through physiology and metabolomics. And based on the results of this study, the response surface was applied to the application of plant growth regulator (PGR) to propose a precise restoration program. We first examined the growth physiological indices and repair of Cu in E. aureum under different Cu stress levels and found that the resistance mechanism of E. aureum to Cu was significantly initiated at 400 mg·L-1. And as the level of Cu stress increased, the Cu content in the plant also increased, and the underground part was the main accumulating part. The translocation factor of E. aureum was <1, and the bioconcentration factor was greater than 1 at all different Cu concentrations. Subsequently, metabolomics studies on E. aureum concluded that arginine and proline metabolism, indole alkaloid synthesis and brassinosteroid biosynthesis are the major pathways involved in the mechanism of Cu stress resistance in E. aureum. Based on these results, we proposed that salicylic acid, sodium nitroprusside and 2,4-epibrassinolide could be selected as PGRs, and further optimized the administration of PGRs using response surfaces. The optimized scheme allowed E. aureum to reach a maximum Cu removal of 84.39 % under 400 mg·L-1 Cu stress, which was 35.61 % higher than the non-fortified treatment. This study provides supporting materials and application options for the Cu repair capacity and resistance mechanisms of E. aureum.