Periphyton is ubiquitous in Florida Everglades and has a profound effect on mercury (Hg) cycling. Enhanced methylmercury (MeHg) production in periphyton has been well documented, but the re-distribution of MeHg from periphyton remains unknown. In this study, periphyton, sediments, surface water, periphyton overlying water, and periphyton porewater were collected from Everglades for analyzing the distribution of MeHg and total Hg (THg). Results showed that there were no significant differences in THg and MeHg in different types of periphyton, but they all displayed higher MeHg levels than sediments. MeHg distribution coefficients (logkd) in periphyton were lower than in sediments, suggesting that periphyton MeHg could be more labile entering aquatic cycling and bioaccumulation. In water, the more the distance of water samples taken from periphyton, the lower the MeHg and dissolved organic carbon concentrations were detected. In extracellular polymeric substances of periphyton, MeHg in colloidal fractions was significantly higher than that in capsular fractions. It was estimated that approximately 10% (or 1.35 kg) of periphyton MeHg were passed on to mosquitofish entering the food web during wet season, contributing 73% of total Hg stocked in mosquitofish. These results revealed the importance of periphyton on water MeHg distribution and MeHg bioaccumulation in Everglades.

This work describes the electroanalytical determination of pendimethalin herbicide levels in natural waters, river sediment and baby food samples, based on the electro-reduction of herbicide on the hanging mercury drop electrode using square wave voltammetry (SWV). A number of experimental and voltammetric conditions were evaluated and the best responses were achieved in Britton–Robinson buffer solutions at pH 8.0, using a frequency of 500s⁻¹, a scan increment of 10mV and a square wave amplitude of 50mV. Under these conditions, the pendimethalin is reduced in an irreversible process, with two reduction peaks at −0.60V and −0.71V, using a Ag/AgCl reference system. Analytical curves were constructed and the detection limit values were calculated to be 7.79μgL⁻¹ and 4.88μgL⁻¹, for peak 1 and peak 2, respectively. The precision and accuracy were determinate as a function of experimental repeatability and reproducibility, which showed standard relative deviation values that were lower than 2% for both voltammetric peaks. The applicability of the proposed methodology was evaluated in natural water, river sediments and baby food samples. The calculated recovery efficiencies demonstrate that the proposed methodology is suitable for determining any contamination by pendimethalin in these samples. Additionally, adsorption isotherms were used to evaluate information about the behavior of pendimethalin in river sediment samples.

Weaknesses of current monomedium aproach of environmental exposure limits determination for socalled „threshold substances“, independently for water and food, are analyzed from the aspect of impact on the human health. Using the examples of mercury pollution in two geographic areas, the inconsistency and ineffectiveness of the risk assessment for the people is demonstrated if exposure limits are derived for each environmental medium independently. Using the example of air,water and food pollution by phenol in two areas, an attempt is made to prove that different exposure limits can be justifiably used for the same environmental pollutant in the same environmental medium if the multimedia approach is applied for deriving exposure limits. It is not necessary to apply the same exposure limit for a pollutant in an environmental medium neglecting exposure levels in other media; not to exceed the tolerable daily intake of the chemical in the human organism from all environmental media is essential.

In this study, Hg²⁺ ions were found to quench the fluorescence of glutathione (GSH)-capped copper clusters (Cu NCs). The Cu NCs were prepared by a simple reduction of CuSO4 in the presence of GSH serving both as a reducing and protecting agents, and characterized by ultraviolet–visible absorption spectroscopy (UV–vis), high resolution scanning electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectrometer (XPS). The GSH-Cu NCs displayed a small size, excellent water-dispersibility, good storage stability, good photostability and were stable in the presence of high concentrations of salt. The GSH-Cu NCs possessed strong blue fluorescence with a quantum yield of 10.6% and exhibited an excitation-independent fluorescence behavior. The zeta potential, TEM, resonance light scattering and dynamic light scattering measurements demonstrated that the Hg²⁺ ion-induced aggregation of the Cu NCs contributed to the fluorescence quenching of the dispersed Cu NCs. On these findings, a sensitive and selective fluorescent probe was developed for detecting Hg²⁺ in the linear range from 10nM to 10μM with a detection limit of 3.3nM (S/N=3). The proposed method has been successfully applied to determine Hg²⁺ content in water sample and food stuff. The results of the proposed method were in good agreement with those obtained by a hydride generation atomic fluorescence spectrometry (HG-AFS).

A new biosorbent material from eggshell membrane was synthesized through thiol functionalization, which is based on the reduction of disulfide bonds in eggshell membrane by ammonium thioglycolate. The thiol-functionalized eggshell membrane was characterized, and its application as an adsorbent for removal of Cr(VI), Hg(II), Cu(II), Pb(II), Cd(II), and Ag(I) from aqueous water has been investigated. The experimental results revealed that the adsorption abilities of the thiol-functionalized eggshell membrane toward Cr(VI), Hg(II), Cu(II), Pb(II), Cd(II), and Ag(I) improved 1.6-, 5.5-, 7.7-, 12.4-, 12.7-, and 21.1-fold, respectively, compared with that of the eggshell membrane control. The adsorption mechanism and adsorption performance, including the adsorption capacity and the kinetics of the thiol-functionalized eggshell membrane for the target heavy metals, were investigated. The effects of solution pH, coexisting substances, and natural water matrices were studied. The thiol-functionalized eggshell membrane can be used as column packing to fabricate a column for real wastewater purification.

The Three Gorges Reservoir (TGR) of China, the largest hydropower project over the world, has attracted much attention to the water impoundment and water-level manipulation. In this study, we evaluated potential effects of water impoundment and seasonal water-level manipulation on the bioaccumulation, trophic transfer and health risk of HMs (Cu, Fe, Zn, Hg, Cd and Pb) in food web components (seston, aquatic invertebrate and fish) in TGR. Our results show that, after the impoundment for eight years (2003–2010), all of the six metal concentrations in aquatic biota fell within the criteria of safety quality guidelines. The concentrations of Cu, Fe, Zn and Hg in fish and aquatic invertebrates were higher than those before impoundment, whereas Cd and Pb were lower than those before impoundment. Nonetheless, Hg, Cd and Pb in aquatic consumers underwent an increasing trend during the entire impoundment, implying potential reservoir effect in the future. Only the concentrations of Hg, Cd and Pb in aquatic consumers exhibited a declining trend towards the dam, showing consistent with the background level at the three reaches. Seasonal variations in HM concentrations of fish and aquatic invertebrates were ascribed to the water-level manipulation associated with reservoir management. Our findings show that Hg or Cd biomagnified through aquatic food web during different hydrological periods, whereas Pb, Cu, Fe and Zn exhibited weak biomagnification power. Overall, Hg, Cd and Pb showed a higher risk than that of Cu, Fe and Zn.

A new bio-MSPE sorbent based on the use of C. micaceus and γ-Fe₂O₃ magnetic nanoparticle was prepared for the preconcentrations of Co(II) and Hg(II). Critical parameters including pH, flow rate, quantity of C. micaceus, quantity of γ-Fe₂O₃ magnetic nanoparticle, eluent (type, concentration and volume), sample volume, and foreign ions were examined. Surface structure and variations after interaction with Co(II) and Hg(II) of bio-MSPE sorbent were investigated by FT-IR, SEM, and EDX. The impact of bio-MSPE column reusage was also tested. The biosorption capacities were determined as 24.7 mg g⁻¹ and 26.2 mg g⁻¹, respectively for Co(II) and Hg(II). Certified reference materials were utilized to find out the accuracy of the prepared bio-MSPE method. This novel bio-MSPE method was accomplished by being applied to real food and water samples. In particular, it will be possible to make use of C. micaceus as new alternatives, in environmental biotechnology applications.

To develop an accurate and precise method for separation and pre-concentration of Hg(II), a novel thionin functionalised core shell structure magnetic material has been prepared and characterised. The extraction ability of the material was evaluated by magnetic solid-phase extraction coupled with inductively coupled plasma mass spectrometry determination of Hg(II) in food and water samples. Combining the advantages of magnetic separation with selective extraction of thionin towards Hg(II), the material exhibits enhanced enrich selectivity and efficiency for Hg(II). The experimental parameters influencing Hg(II) extraction efficiency, including pH of the aqueous solution, the dosage of the adsorbent, extraction time and sample volume, were systematically investigated. Under the optimised conditions, concentration of Hg(II) at 1.0 μg L⁻¹ can be successfully enriched by the material without the interference of the common co-existing ions. The enrichment factor and adsorption capacity were 250 and 75.2 mg g⁻¹, and precise of the method was confirmed by analysing the spiked food, water samples and standard water reference samples with the recoveries of 92.5–101.8%.

A rapid and efficient method based on a novel nitrogen-doped porous graphene nanostructure (NDPG) was used for the speciation of mercury in water and human blood samples by the CV-AAS. The mixture of the NDPG, ionic liquid, and acetone was rapidly injected into the human blood, water, and food samples for mercury separation by the cloud point assisted dispersive ionic liquid-micro solid-phase extraction (CPA-DIL-μ-SPE) at pH 7.5. The UV-microwave accessory converted the organic mercury (R-Hg) to inorganic mercury, and total mercury (TM) was determined. Finally, the organic mercury was calculated by subtracting the inorganic and entire mercury contents. By optimizing, the linear range, LOD, and enrichment factor were obtained (0.01–6.80 µg/L; 0.005–3.60 µg/L), (2.6 ng/L; 1.2 ng/L) and (9.8; 20.2) for the mercury species in human blood and water/food samples, respectively (Mean of RSD < 1.9 %). The CRM samples obtained the validation of the procedure.

A simple and highly selective and sensitive catalytic adsorptive stripping voltammetric procedure for determination of ultra trace levels of chromium(VI) on hanging mercury drop electrode is reported. The method is based on the adsorptive preconcentration of the Cr(III)–dithiooxamide (rubeanic acid) complex and the utilization of the catalytic reaction in the presence of nitrate. At optimized conditions the calibration graph is linear from 0.01 to 6ng/ml and detection limit is 0.002ng/ml for accumulation time of 50s. The interference of some common ions was studied and this method has been applied to the determination of chromium in food and waste water samples with satisfactory results.