Bioaccumulation In Food Chain Research Articles

Integration of Nontarget Screening and QSPR Models to Identify Novel Organophosphate Esters of High Priority in Aquatic Environment.

With the development of large numbers of novel organophosphate esters (OPEs) alternatives, it is imperative to screen and identify those with high priority. In this study, surface water, biofilms, and freshwater snails were collected from the flow-in rivers of Taihu Lake Basin, China. Screened by target, suspect, and nontarget analysis, 11 traditional and 14 novel OPEs were identified, of which 5 OPEs were first discovered in Taihu Lake Basin. The OPE concentrations in surface water ranged from 196 to 2568 ng/L, with the primary homologue tris(2,4-ditert-butylphenyl) phosphate (TDtBPP) being newly identified, which was likely derived from the transformation of tris(2,4-ditert-butylphenyl) phosphite. The majority of the newly identified OPEs displayed substantially higher bioaccumulation and biomagnification potentials in the biofilm-snail food chain than the traditional ones. Quantitative structure-property relationship models revealed both hydrophobicity and polarity influenced the bioaccumulation and biomagnification of the OPEs, while electrostatic attraction also had a contribution to the bioaccumulation in the biofilm. TDtBPP was determined as the utmost priority by toxicological priority index scheme, which integrated concentration, bioaccumulation, biomagnification, acute toxicity, and endocrine disrupting potential of the identified OPEs. These findings provide novel insights into the behaviors of OPEs and scientific bases for better management of high-risk pollutants in aquatic ecosystem.

Type-specific inflammatory responses of vascular cells activated by interaction with virgin and aged microplastics

Microplastics (MPs) are recognized as a major environmental problem due to their ubiquitous presence in ecosystems and bioaccumulation in food chains. Not only humans are continuously exposed to these pollutants through ingestion and inhalation, but recent findings suggest they may trigger vascular inflammation and potentially worsen the clinical conditions of cardiovascular patients. Here we combine headspace analysis by needle trap microextraction-gas chromatography-mass spectrometry (HS-NTME-GC-MS) and biological assays to evaluate the effects of polystyrene, high- and low-density polyethylene MPs on phenotype, metabolic activity, and pro-inflammatory status of Vascular Smooth Muscle Cells (VSMCs) the most prominent cells in vascular walls. Virgin and artificially aged MPs (4 weeks at 40 °C and 750 W/m2 simulated solar irradiation) were comparatively tested at 1 mg/mL to simulate a realistic exposure scenario. Our results clearly show the activation of oxidative stress and inflammatory processes when VSMCs were cultured with aged polymers, with significant overexpression of IL-6 and TNF-α. In addition, volatile organic compounds (VOCs), including pentane, acrolein, propanal, and hexanal as the main components, were released by VSMCs into the headspace. Type-specific VOC response profiles were induced on vascular cells from different MPs.

A reversible fluorescent chemosensor based on a naphthalene dyad for Pb(II) ions: Applications in food, water, and bio-imaging

Lead (Pb2+) ions, among heavy toxic metals, are extensively distributed and bioaccumulate in food chains, prompting researchers to monitor their levels in water and biosystems. Consequently, aiming to protect the environment and human health, this study synthesizes a straightforward naphthalene-naphthalene dyad-based "turn-on" fluorescent chemosensor (S) tailored for detecting Pb2+ ions. This selective response to Pb2+ ions over other competing metal ions is characterized by hypsochromic changes in fluorescence enhancement resulting from an intramolecular charge transfer (ICT) process from -OH group (donor) to the naphthyl ring (acceptor) following the complexation of S-Pb2+. Moreover, cross-contamination titration for probe S was conducted in the presence of various distinct competitive metal ions. By employing Job's plot and B-H plot, the complicated stoichiometry (1:2) and association constant (Ka = 9.45×104 M−1) of S-Pb2+ were studied. The probe's interaction with Pb2+ is studied using spectroscopic measurements and DFT calculations. The probe demonstrated exceptional selectivity and sensitivity, achieving a limit of detection (LOD) value of 12.50×10−6 M for Pb2+ in a buffered THF:H2O (50:50, v:v) medium. The applicability of chemosensor S spans across various water, food, and E. coli samples, indicating its potential in monitoring and managing Pb2+ toxicity in wastewater and biosystems.

Soil health as a proxy for long-term reclamation success of metal-contaminated mine tailings using lime and biosolids

Mine lands contaminted with heavy metals pose environmental risks, and thus reclamation is paramount for improving soil, plant, animal, and ecosystem health. A metal-contaminated alluvial mine tailing, devoid of vegetation, received 224 ​Mg ​ha−1 of both lime and biosolids in 1998, and long-term reclamation success was quantified in 2019 with respect to soils, plants, and linkages to animals. Reclamation success was quantified using the Soil Management Assessment Framework (SMAF), in conjunction with bioavailable (0.01 ​M CaCl2 extractable) and plant-available (Mehlich-3 extractable) soil metal concentrations, X-ray absorption spectroscopy, plant metal concentrations, and plant quality characteristics. Results showed that all soil indicators were improved in successfully-reclaimed areas as compared to on-site degraded areas, including increases in soil aggregate stability, pH, plant-available P and K, soil organic C, potentially-mineralizable N, microbial biomass C and β-glucosidase activity and decreases in soil bulk density and electrical conductivity. Of indicators, unitless soil health scores were assigned based on the SMAF, with data suggesting that bulk density, wet aggregate stability, potentially- mineralizable N, microbial biomass C, pH, and electrical conductivity should be monitored in the future. The long-term effects of lime and biosolids application have improved soil physical, biological, and overall soil health. Plant metal concentrations have decreased by an order of magnitude since early reclamation, with most plant metal concentrations being tolerable for domestic livestock consumption. From an animal health perspective, feeding grasses from this site during latter parts of a growing season may need supplemental feed to provide greater protein and energy content, and to reduce potentially-harmful Cd concentrations from food chain bioaccumulation. However, a health concern exists based on soil bioavailable Cd and Zn concentrations that exceed ecological soil screening levels. Still, plants have stabilized the soil and acidity remains neutralized, leading to long-term improvements in soil health, with overall improved ecosystem health.

Cadmium (Cd) influences calcium (Ca) levels in the skeleton of a freshwater fish Channa gachua.

Environmental contamination with heavy metals is a threat to the organisms due to their toxicity, persistence and bioaccumulation in food chains. The study was aimed to assess cadmium (Cd) effect on calcium (Ca) level in bones of a freshwater fish Channa gachua. 42 fish individuals were kept into six (6) aquaria; labelled aq.0, 1, 2, 3,4 and 5 in the laboratory for treatment. Aq.0 was control group and aq.1, 2,3,4,5 were experimental with treatment solution of Cd 0, 0.1ppm, 0.5ppm, 1ppm, 2.5ppm and 5ppm respectively for three months. After exposure, bones tissue were examined for Cd accumulation and Ca concentration. Highest accumulation of Cd were recorded in aq.5 mean 46.86 ± 0.46 mgkg-1 .and lowest in the control group with mean 0.61 ± 0.06 mgkg-1. The order of Cd bioaccumulation in bones were aq.5 > aq.4 >aq.3 > aq.2 > aq.1 > aq.0. Highest concentration of Ca were noted in aq.0 (Control group) mean 7888.06 ± 4827.22 mgkg-1 and lowest were 1132.36 ± 203.73 mgkg-1 in aq.5 (at 5.0 ppm). Generally a pattern of decreasing Ca level were observed with each rise of Cd bioaccumulation aq.0 > aq.1 > aq.2 > aq.3 > aq.4 > aq.5. Current study indicated that Cd accumulation have substantial effect on Ca level in bones and hence on skeleton system. Strict rules must be implemented by government to control metals pollution and exploitations of biota.

Rapid Determination of PCDDs, PCDFs and DL-PCBs in Foods, Feedingstuffs and Vegetable Oils Using New Modified Acid Silica

Polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls are persistent organic pollutants (POPs), which in the recent years received huge attention due to their extreme stability, high potential toxicity and bioaccumulation in food chains.

Dietary intakes of dioxins and polychlorobiphenyls (PCBs) and mortality: EPIC cohort study in 9 European countries

Dioxins and polychlorinated biphenyls (PCBs) are toxic, endocrine disruptors and persistent chemicals for which the main exposure source is diet due to their bioaccumulation and biomagnification in food chains. Cohort studies in the general populations have reported inconsistent associations between these chemicals in serum/plasma and mortality. Our objective was to study the association between dietary intake of 17 dioxins and 35 PCBs and all-cause, cancer-specific and cardiovascular-specific mortalities were assessed in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Dietary intake of dioxins and PCBs was assessed combining EPIC food consumption data with European food contamination data provided by the European Food Safety Authority. We applied multivariable Cox regressions. The analysis included 451,390 adults (mean ± SD age:51.1 ± 9.7 years) with 46,627 deaths and a median follow-up of 17.4 years (IQR = 15.2–19.1). A U-shaped non-linear association with all-cause mortality for dietary intake of dioxins (Pnon-linearity<0.0001), DL-PCB (Pnon-linearity = 0.0001), and NDL-PCBs (Pnon-linearity<0.01) was observed. For example, the hazard ratios (95%Confidance interval) for all-cause mortality obtained with the spline model was equal to 1.03 (1.02–1.05) for low levels of intake to dioxins (7 pg TEQ/day), 0.93 (0.90–0.96) for moderate levels of intake (25 pg TEQ/day), while for high levels of intake (55 pg TEQ/day) it was 1.03 (0.97–1.09). Intake of dioxins, DL-PCBs and NDL-PCBs was not associated with cardiovascular mortality. There was no association between intakes of dioxins and cancer mortality, but a U-shaped association was observed for intake of DL-PCBs and intakes of NDL-PCBs and cancer mortality. The PCBs and dioxins are known to have endocrine disrupting properties which can lead to non-monotonic dose responses. These results need to be interpreted with caution and further studies are needed to better clarify the association between dietary intake of dioxins and PCB and mortality in the general population.

Effect of Chlorpyrifos on Histology of Liver, Gills, and Brain of Oreochromis Mossambicus (Peters)

Most of the river waters in Kerala are found to have several pollutants such as heavy metals, plasticizers, and pesticides. Chlorpyrifos, commonly known as Dursban is a broad-spectrum organophosphate insecticide widely used in Kerala to control insects in crops, termites and to control mosquito larvae. This pesticide is known to reach the aquatic ecosystem causing several damages to aquatic organisms. Fish being on top of the food chain bioaccumulation of these pesticide residues are of concern. This study was to find the histological changes in the liver, brain, and gills of Orechromis mossambicus, commonly called Tilapia, a common freshwater edible fish, on exposure to chlorpyrifos for 7, 14, and 21 days to evaluate the extent of toxicity. For this fish, Orechromis mossambicus of age one to three were procured from a local fish farm of Pathanamthitta district, Kerala, and were acclimatized in tanks in the laboratory and exposed to chlorpyrifos for 7, 14, and 21 days and histology of brain, liver, and gills were carried. The microphotographs of the sections show severe damage to these tissues as early as 14 days of exposure.

Kinetic, Equilibrium and Thermodynamic Study for Adsorptive Detoxification of Pb+2 by Thiocarbamoyl Chitosan

The environmental effect of industrial effluents, including chromium (Cr), lead (Pb), mercury (Hg), copper (Cu), and nickel (Ni) can have harmful impacts, which includes soil, water, and air pollution, bioaccumulation in food chains, degradation of ecosystems, loss of biodiversity, and contaminated drinking water. Biopolymers such as chitosan have been widely used in wastewater treatment. The ability of thiocarbamoyl chitosan to remove lead ions was assessed by combining thio urea and glutaraldehyde (GLA). During the first two hours of interaction with sorbent, 86% of the metal ions were shown to have been eliminated. According to the adsorption investigation, the prepared sorbent had an outstanding removal rate of metal ions, with a Langmuir maximum absorption capacity of 38 mg/gm at 25 degrees Celsius and a pH of 6. With a linear coefficient of 0.9996, the data on adsorption kinetics were predicted using a pseudo-second order kinetic model. The Langmuir isotherm, which suggests favourable adsorption by homogenous monolayer adsorption, might represent the adsorption process effectively. The adsorption procedure was also demonstrated to be exothermic at all temperatures, with spontaneous responses being energetically endorsed as indicated by negative free energy values.

Impacts of autochthonous dissolved organic matter on the accumulation of methylmercury by phytoplankton and zooplankton in a eutrophic coastal ecosystem

The bioaccumulation of methylmercury (MeHg) within the pelagic food webs is a crucial determinant of the MeHg concentration in the organisms at higher trophic levels. Dissolved organic matter (DOM) is recognized for its influence on mercury (Hg) cycling in the aquatic environment because of its role in providing metabolic substrate for heterotrophic organism and serving as a strong ligand for MeHg. However, the impact of DOM on MeHg bioaccumulation in pelagic food chains remain controversial. Here, we explored MeHg bioaccumulation within a pelagic food web in China, in the eutrophic Bohai Sea and adjacent seas, covering a range of DOM concentrations and compositions. Our findings show that elevated concentrations of dissolved organic carbon (DOC) and phytoplankton biomass may contribute to a reduction in MeHg uptake by phytoplankton. Moreover, we observe that a higher level of autochthonous DOM in the water may result in more significant MeHg biomagnification in zooplankton. This can be explained by alterations in the structure of pelagic food webs and/or an increase in the direct consumption of DOM and particulate organic matter (POM) containing MeHg. Our study offers direct field monitoring evidence of dual roles played by DOM in regulating MeHg transfers from water to phytoplankton and zooplankton in coastal pelagic food webs. A thorough understanding of the intricate interactions is essential for a more comprehensive evaluation of ecological risks associated with MeHg exposure in coastal ecosystems.

Heavy metals content in sweet potato (Ipomoea batatas L.) grown on soil contaminated by gold mine tailings with composted cow manure amendment

Artisanal gold miners usually dispose of gold mine tailings in storage ponds or agricultural land used for farming. However, the gold mine tailings still contain heavy metals such as cadmium, copper, lead, and zinc and can lead to bioaccumulation in food chains. This study investigated the influence of composted cow manure as organic fertilizer on heavy metals (Cd, Cu, Pb and Zn) content in sweet potatoes grown on soil contaminated by gold mine tailing. The MZ119 clone sweet potato plants were grown on soils added with mixtures of gold mine tailings at ratios of 0% (control), 30%, 50%, 70%, and 100% (w/w), and composted cow manure (0, 250, 500, and 750 g/10 kg of soil). The results showed that the higher the ratio of gold mine tailings to the soil, the higher the accumulation of metals in sweet potatoes. According to the translocation factor (TF) value, heavy metals (Cd, Cu, Pb and Zn) accumulated higher in the shoots than in the roots of sweet potatoes. Accumulation of heavy metals in sweet potato occurred in the following order: Zn&amp;gt;Cu&amp;gt;Pb&amp;gt;Cd. This study recommends that sweet potatoes could be used for the phytoremediation of heavy metals (Cd, Cu, Pb and Zn) in polluted soils, but the plants may not be used for consumption.

Pyrethroid residues in Indonesian river Citarum: A simple analytical method applied for an ecological and human health risk assessment

Pyrethroid residues in the Citarum River, Indonesia, was first investigated based on their occurrences, water assimilative capacity, and risk assessment. In this paper, first, a relatively simple and efficient method was built and validated for analysis of seven pyrethroids in a river water matrix: bifenthrin, fenpropathrin, permethrin, β-cyfluthrin, cypermethrin, fenvalerate, and deltamethrin. Next, the validated method was used to analyze pyrethroids in the Citarum River. Three pyrethroids, β-cyfluthrin, cypermethrin, and deltamethrin, were detected in some sampling points with concentration up to 0.01 mg/L. Water assimilative capacity evaluation shows that β-cyfluthrin and deltamethrin pollution exceed the Citarum river water capacity. However, due to hydrophobicity properties of pyrethroids, removal through binding to sediments are expected. Ecotoxicity risk assessment shows that β-cyfluthrin, cypermethrin and deltamethrin pose risks to the aquatic organisms in the Citarum River and its tributaries through bioaccumulation in food chain. Based on bioconcentration factors of the detected pyrethroids, β-cyfluthrin poses the highest adverse effect to humans while cypermethrin is the safest. Human risk assessment based on hazard index suggests that acute non-carcinogenic risk associated to consuming fish from the study location polluted with β-cyfluthrin, cypermethrin and deltamethrin is unlikely. However, hazard quotient shows that chronic non-carcinogenic risk associated to consuming fish from the study location polluted with β-cyfluthrin is likely. However, since the risk assessment was performed separately for each pyrethroid, further assessment on the impact of mixture pyrethroid to aquatic organisms and humans should be performed to explore the real impact of pyrethroids to the river system.

Rapid determination of PCDDs, PCDFs and DL-PCBs in foods, feeding stuffs and vegetable oils using new modified acid silica

Polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls are persistent organic pollutants (POPs), which in recent years received huge attention due to their extreme stability, high potential toxicity and bioaccumulation in food chains. The main source of human exposure to these compounds is discovered in foods of animal origin, especially foods rich in fat. The target of the present study was to set up an analytical method for the determination of PCDDs/PCDFs and DL-PCB in vegetable oils, sunflower meals, sunflower seeds, rapeseeds and milk powder. The first step consisted of a semi-automatic Soxhlet extraction for 3 hours, by using a mixture of Hexane: Acetone – 80:20, followed by acid digestion with 55% acid silica and filtration. After concentration, the extract is purified on a multilayer column (silica gel, silica-KOH, silica-H2SO4 anhydrous Na2SO4) followed by an alumina column separation in two fractions (first fraction containing PCDDs/PCDFs and second containing only PCBs). The purified extract was then analyzed by GC/MS/MS. The newly developed approach in our lab was capable to reduce the overall time of sample preparation to seven hours/ per sample. Since the method shows good mean recoveries for all labeled congeners spiked in the samples (for PCDDs/PCDFs – 80% - 110%, for DL-PCBs – 70% - 85%), we assumed the absence of overestimation or underestimation in the analyzed samples.

Specific types of wastewater pollution in Ostrava and possibilities of decontamination through wastewater treatment plants

This paper provides an introduction to the problem of the occurrence of some groups of micropollutants in wastewater, namely pharmaceutically active compounds (PhAC) and drugs in the context of wastewater treatment in Ostrava (290,000 inhabitants). Wastewater treatment is an essential service that ensures the reduction of pollutants in wastewater, while also protecting human health and the environment. In Europe, most wastewater enters the sewerage system and is discharged to a wastewater treatment plant, from where it is further discharged into rivers, lakes or coastal areas. Recently, people have been focusing more on pollutants in wastewater that are not targeted by WWTP, i.e., so-called micropollutants, which are, for example, pharmaceutically active compounds, drugs, or their metabolites. The risk of these groups of micropollutants in water is, for example, the possibility of exposure to aquatic organisms or bioaccumulation in food chains. The discharge of treated wastewater from the WWTP is the central route for PhAC to enter surface waters, as current technologies for decontamination are not yet designed. On the other hand, WWTPs act as primary barriers against the spread of micropollutants. One of the basic steps in designing a decontamination technology is to know the composition of the local wastewater.

A multi-pathway exposure assessment for polycyclic aromatic hydrocarbons among residents in the Athabasca oil sands region, Canada.

Due to increasing emissions from ongoing development of the oil sands in Northern Alberta, Canada, there is concern that local residents and organisms are experiencing elevated exposures to hazardous contaminants. We modified an existing human bioaccumulation model (ACC-Human) to represent the local food chain in the Athabasca oil sands region (AOSR), the focus of oil sands development in Alberta. We used the model to assess the potential exposure to three polycyclic aromatic hydrocarbons (PAHs) among local residents that have a high intake of locally sourced traditional foods. To place these estimates into context, we complemented them with estimated PAH intake through market foods and smoking. Our approach was able to produce realistic body burdens of the PAHs in aquatic and terrestrial wildlife and in humans, both in magnitude and with respect to the relative difference between smokers and non-smokers. Over the model simulation period (1967-2009), market food was the dominant dietary exposure route for phenanthrene and pyrene, while local food, and in particular local fish, dominated the intake of benzo[a]pyrene. Exposure to benzo[a]pyrene therefore was also predicted to increase over time in concert with expanding oil sands operations. Those smoking at the average rate of Northern Albertans take in an additional amount of all three PAHs that is at least as large as dietary intake. Estimated daily intake rates are below toxicological reference thresholds for all three PAHs. However, daily intake of BaP in adults is only ∼20 fold below those thresholds and is predicted to increase. Key uncertainties in the assessment included the effect of food preparation on the PAH content in food (e.g., smoking of fish), the limited availability of market food contamination data specific to Canada, and the PAH content of the vapor phase of first-hand cigarette smoke. Considering the satisfactory model evaluation, ACC-Human AOSR should be suited to making predictions of future contaminant exposure based on development scenarios in the AOSR or in response to potential emission reduction efforts. It should also be applicable to other organic contaminants of concern released by oil sands operations.

Boron and nitrogen co-doped bright yellow fluorescent carbon dots as real-time selective detection of phthalic acid plasticizer in aqueous medium

Excessive usage and discharge of phthalic acid in the environment affect endocrine system of living beings via bioaccumulation in food chain. In this paper, boron and nitrogen co-doped yellow fluorescent carbon dots (B, N-C-dots) have been designed for the rapid recognition of plasticizer phthalic acid. These C-dots were prepared by carbonization of 4-bromo-1,2-diaminobenzene and boric acid mixture. The bright fluorescence (PLQY = 26.4 %) of C-dots showed a significant Stokes shift of 145 nm under 430 nm excitation wavelength. These B, N-C-dots selectively detect phthalic acid in aqueous solution instantaneously and experienced a maximum 95 % fluorescence quenching immediately upon the treatment with phthalic acid with a limit of detection of 91.12 nM. It has been proved that the combined effect of strong intermolecular hydrogen bonding, chemical conjugation, and non-fluorescent ground state complex formation between the probe and analyte led to fluorescence quenching of the C-dots. Static quenching has been confirmed from changes in B, N-C-dots UV–vis absorbance spectroscopy and non-changes in fluorescence lifetime after adding phthalic acid. Furthermore, these B, N-C-dots were successfully applied to recover the analyte in real water samples and showed an average recovery rate of 96.4–102 % with a good relative standard deviation from spiked samples. This study provides selective recognition ability in the field of environmental monitoring and remediation.

An exploratory spatial contaminant assessment for polar bear (Ursus maritimus) liver, fat, and muscle from northern Canada

Since the industrial era, chemicals have been ubiquitous in worldwide ecosystems. Despite the discontinued release of highly toxic persistent organic pollutants (POPs) in the environment, the levels of some POPs are still being measured in the Canadian Arctic. These contaminants are of great concern due to their persistence, toxicity, and levels of bioaccumulation in food chains. Animals occupying top trophic positions in the Canadian Arctic, particularly polar bears, are exposed to these contaminants mainly through their diet. Our study investigated the levels of 30 metals (including total and methyl mercury) alkaline and alkaline earth metals, 15 polycyclic aromatic compounds and their alkyl congeners (PACs), 6 chlordanes (CHLs), and 20 polychlorinated biphenyls (PCBs), in 49 polar bears from the Canadian Arctic. Contaminant burden was measured in liver, muscle, and fat in bears of different sex, age, and locations. A principal component analysis did not distinguish differences between age and sex profiles for most contaminants. However, the concentrations measured and their distribution in the tissues confirm findings observed in past studies. This study highlights the importance of continual monitoring of polar bear health (e.g., newly detected PACs were measured within this study) and evaluating those impacts for the next generations of polar bears.

Growth Responses of Indonesian Foxtail Millet (Setaria italica (L.) Beauv.) to Cadmium Stress

Cadmium (Cd) contamination is considered as one of the most important environmental and human health issues worldwide. The occurrence of Cd in air, water and soil is resulted from massive industrialization, uncontrolled agricultural system and anthropogenic activities in urban lives. The presence of Cd in soil threatens human health through food chain bioaccumulation, negatively affect soil quality and also reduce the productivity of agricultural crops. Foxtail millet ( Setaria italica L.) is an alternative cereal food that is highly tolerant to abiotic stresses such as drought and salinity. However, the mechanism underlying its response to the stress caused by heavy metals, such as Cd, remains unclear. This study aimed to examine the effects of Cd stress on morpho-physiological responses of the foxtail millet accession Buru Merah, cultivated using the hydroponic method. To this end, four levels of Cd concentrations (0, 0.5, 1.0, and 1.5 µM in ABmix™ growth media) were applied for 4 weeks followed by morpho-physiological assessements, including plant height, root length, shoot and leaf number, panicle biomass measurements and chlorophyll content evaluation. Our results demonstrated that Cd stress perturbed the growth of foxtail millet on morpho-physiological parameters, particularly at the highest Cd concentration (1.5 µM). The negative effects of Cd stress included decrease in shoot length, root length, number of leaves and shoots, panicle biomass, and chlorophyll content. Furthermore, our findings showed that Cd stress affected the growth of foxtail millet in a concentration-dependent manner. Taken together, our findings might be useful for further development of strategies to increase plant tolerance to heavy metal stress and ensure sustainable food production. In addition, this study also demonstrated the importance of protecting nature from Cd contamination.

Highly sensitive B, N co-doped carbon dots for fluorescent and colorimetric dual-mode detection of mercury ions in wastewater

Mercury ions (Hg2+) owing to excessive discharge cause serious damage to human health and the water ecosystem via bioaccumulation in food chains. Novel materials employed for the high-performance monitoring of Hg2+ are urgently required. Herein, using sucrose, boric acid, and melamine as raw materials, a new nanomaterial sensor, namely boron and nitrogen co-doped carbon dots (B, N-CDs), was designed for fluorescent and colorimetric dual-mode detection of Hg2+. Because of the occurrence of both dynamic and static quenching, B, N-CDs were utilized to function as fluorescent sensors for detecting Hg2+ with a limit of detection (LOD) of 5.3 nM. B, N-CDs performed an action for catalytic oxidation of 3,3′,5,5′-Tetramethylbenzidine (TMB) to a blue cationic radical via peroxidase mimetic activity. By sequentially adding cysteine and Hg2+ to control the emergence of the TMB cation radical, a sensor for the Hg2+ assay was established through the colorimetric "on-off-on" signal and the LOD was as low as 7.8 nM. Moreover, the application potential of B, N-CDs for complex water environments was demonstrated to be excellent. In summary, the dual-mode detection method delivers some valid strategies for the detection of mercury in aqueous solutions employing the functional nanomaterials mentioned, and opens new avenues in tackling the problem of heavy metal ion pollution for environmental monitoring and remediation.

Determining selenium speciation by graphite furnace atomic absorption spectrometry.

A straightforward method for measuring two aquatic inorganic species of selenium, selenate, Se(VI), and selenite, Se(IV), was developed in this study. Selenium toxicity and bioaccumulation in food chain are strongly dependent on its speciation. Therefore, it is important to measure selenium species as part of any selenium risk assessment practice. In this method, total selenium was first measured using graphite furnace atomic absorption spectrometry, and then, chemical procedures in the literature were used to reduce selenite, Se(IV), to hydrogen selenide (H2Se). Total selenium of the same solution was measured again with the analytical instrument after stripping H2Se from the solution. The difference of total selenium measured gave Se(IV) concentration. The two main species in natural waters are Se(VI) and Se(IV). Therefore, it can be assumed that after removing Se(IV) from the solution, the remaining total selenium is Se(VI). The two inorganic selenium species of (IV) and (VI) in purified waters and synthetic irrigation waters both spiked with Se(VI) and Se(IV) were determined using this method. Recovery of spiked samples in diluted synthetic irrigation water was 97% for Se(VI) and 99% for Se(IV). Detection limits of the method were 0.32µg L-1 for Se(VI) and 0.11µg L-1 for Se(IV). The advantages of the method developed in this study are that it employs a straightforward simple chemical reaction combined with acidification and stripping, requires only one instrument (graphite furnace atomic absorption spectrometry), and does not require extensive sample pretreatment.