Fluorescence behaviour of Zn and Ni complexes of humic acids from different sources

Conventional fluorescence spectroscopy in the excitation, emission and synchronous scan modes and three-dimensional fluorescence spectroscopy in the form of an excitation-emission matrix (EEM) of fluorescence intensity as a function of excitation and emission wavelengths have been applied to the study of three humic acids (HAs) extracted from soil (SHA), peat (PHA) and compost (CHA) and their interaction products with Zn(II) and Ni(II) ions. Fluorescence spectra of HAs appear to be related to the nature and origin of the sample. A strong reduction of intensity of all peaks is observed in the spectra of HAs-metal complexes as compared to those of untreated HAs. Ni(II) exhibits greater quenching ability than Zn(II). Fluorescence quenching measured for complexes of HAs at increasing Ni(II) concentrations was linearly correlated with metal ion concentration. The different capacity to interact with metal ions showed by various HAs is attributed to their different molecular complexity.     

Fate of cancerostatic platinum compounds in biological wastewater treatment of hospital effluents

The present work focuses on the fate of two cancerostatic platinum compounds (CPC), cisplatin and carboplatin, as well as of two inorganic platinum compounds, [PtCl₄]²⁻ and [PtCl₆]²⁻ in biological wastewater treatment. Laboratory experiments modelling adsorption of these compounds onto activated sludge showed promising specific adsorption coefficients K_D and K_OC and Freundlich adsorption isotherms. However, the adsorption properties of the investigated substances were differing significantly. Adsorption decreased following the order cisplatin > [PtCl₆]²⁻ > [PtCl₄]²⁻ > carboplatin. Log K_D-values were ranging from 2.5 to 4.3 , log K_OC from 3.0 to 4.7.

A pilot membrane bioreactor system (MBR) was installed in a hospital in Vienna and fed with wastewater from the oncologic in-patient treatment ward to investigate CPC-adsorption in a sewage treatment plant. During three monitoring periods Pt-concentrations were measured in the influent (3–250 μg l⁻¹ Pt) and the effluent (2–150 μg l⁻¹ Pt) of the treatment plant using ICP-MS. The monitoring periods (duration 30 d) revealed elimination efficiencies between 51% and 63% based on averaged weekly input–output budgets. The derived log K_D-values and log K_OC-values ranged from 2.4 to 4.8 and from 2.8 to 5.3, respectively. Species analysis using HPLC-ICP-MS proofed that mainly carboplatin was present as intact drug in the influent and – due to low log K_D – in the effluent of the MBR.     

Synchronous-scan fluorescence spectra of Chlorella vulgaris solution

The characterization of the Chlorella vulgaris solution was carried out using synchronous-scan spectroscopy. The range of concentration of algae and Fe(III) in aqueous solutions were 5 × 10⁸–8 × 10⁹ cells l⁻¹ and 10–60 μM, respectively. Effective characterization method used was synchronous-scan fluorescence spectroscopy. The wavelength difference (Δλ) of 90 nm was maintained between excitation and emission wavelengths; 90 nm was found to be the best Δλ for effective characterization of Chlorella vulgaris solution with or without quencher species (e.g., Fe(III), humic acid (HA)) for the first time. The peak was observed at about EX 236.6 nm/EM 326.6 nm for synchronous-scan fluorescence spectra. The fluorescence quenching of algae in system of algae–Fe(III)–HA was studied using synchronous-scan spectroscopy for the first time. Fe(III) was clearly the effective quencher. The relationship between I₀/I (quenching efficiency) and c (concentration of Fe(III) added) was a linear correlation for the algae solution with Fe(III). Also, Aldrich humic acid was found to be an effective quencher. pH effect on synchronous-scan fluorescence intensity of algal solution with Fe(III) and/or HA was evident.     

Evaluating the impacts of some environmentally relevant factors on the availability of bisphenol A with negligible-depletion SPME

The effect of some environmentally relevant factors including salinity, pH, and humic acids on the availability of bisphenol A (BPA) was evaluated by using the negligible-depletion solid-phase microextraction (nd-SPME) biomimetic method. With the variation of salinity (0–500 mM NaCl) and pH (5.0–8.5) of aqueous solutions, the partition coefficients of BPA between the nd-SPME fiber and the aqueous solution varied in the range of log D = 3.55–3.86, which indicates that the salinity and pH can influence the availability of BPA. By using Acros humic acid as model dissolved organic matter (DOM), it was also demonstrated that the environmental factors such as salinity and pH could affect the partitioning of BPA between DOM and aqueous solutions. The determined partition coefficients of BPA between dissolved organic carbon (DOC) and aqueous solutions were in the range of log D_DOC = 4.03–5.60 for Acros humic acid solutions with 1–50 mg l⁻¹ DOC. The influence of salinity and pH on log D_DOC was more significant at low concentration (0–5 mg l⁻¹) of DOC.     

Physicochemical substance properties as indicators for unreliable exposure in microplate-based bioassays

In the last years many efforts were made to transform standardized algal test protocols into low-cost microplate assays. While advantages were pointed out frequently, limitations are not systematically addressed, thus hindering a widespread utilisation. In this study a group of organic substances with a wide distribution of volatility (log K_AW from −6.53 to −2.13) and lipophilicity (log K_OW from 1.26 to 4.92) was investigated with respect to the influence of these physicochemical properties on their algal toxicity in different assays. Therefore the EC₅₀ values were determined with a microplate assay based on ISO 8692 protocol and the results were compared with those of an established algal growth inhibition test conducted in air tight glass vessels. Using the ratio of the EC₅₀ values, a clear connection between biological response and volatility as well as lipophilicity of test substances could be detected. Chemicals with a log K_OW higher than 3 or a Henry coefficient log K_AW higher than −4 were identified as less effective in the microplate assay than in the comparative assay. The loss in nominal concentration due to physicochemical properties could be shown to contribute to this using HPLC analysis. Consequently, when using microplate assay’s one should be aware that lipophilic and volatile chemicals might be underestimated in their toxicity, which could be indicated from evaluating related physicochemical properties modelled from structural information prior to an experimental investigation.     

The complexation of Cu(II) by anthropogenic fulvic acids extracted from composted urban and livestock wastes

Abstract

The fulvic acid (fua) fractions of two samples of composted solid wastes [urban (urfua) and livestock (lsfua) wastes], commercialized to be used in agriculture as organic correctives or fertilizers, were analyzed for their affinity towards Cu(II) at pH=6. Molecular fluorescence spectroscopy (synchronous mode) was used to monitor the quenching caused by the complexation upon addition of Cu(II) to fua. Spectral data were preprocessed by a chemometric self‐modeling mixture analysis method (SIMPLISMA) to detect the number of different types of fluorescent binding sites that exist in each fua, their spectra and the corresponding quenching profiles [fluorescence intensity as function of the total Cu(II) concentration]. From the analysis of the quenching profiles, the amount of binding sites (Cl) and the corresponding conditional stability constants (K') were calculated. Both fua samples have approximately Cl = 0.21 mmol/g and the logarithms of K’ are 4.21(3) and 4.51(8), respectively for urfua and lsfua. The differences detected between these fua samples and those extracted from natural soils can be attributed mainly to the relatively small humification extent of the present anthropogenic fua samples.     

Copper complexation by tannic acid in aqueous solution

The speciation of titrated copper in a dissolved tannic acid (TA) solution with an initial concentration of 4 mmol organic carbon (OC)/l was investigated in a nine-step titration experiment (Cu/OC molar ratio = 0.0030–0.0567). We differentiated between soluble and insoluble Cu species by 0.45 μm filtration. Measurements with a copper ion selective electrode (ISE) and diffusive gradients in thin films (DGT) were conducted to quantify unbound Cu(II) cations (‘free’ Cu) and labile soluble Cu complexes. For the DGT measurements, we used an APA hydrogel and a Chelex 100 chelating resin (Na form). Insoluble organic Cu complexes (>0.45 μm) was the dominant Cu species for Cu/OC = 0.0030–0.0567 with a maximum fraction of 0.96 of total Cu. At Cu/OC > 0.0100, Cu-catalysed degradation of aggregate structures resulted in a strong increase of free Cu and (labile) soluble Cu complexes with a maximum fraction of 0.28 and 0.32 of total Cu, respectively. Labile (i.e. DGT-detectable) soluble Cu complexes had a relatively high averaged diffusion coefficient (D) in the APA hydrogel (3.50 × 10⁻⁶– 5.58 × 10⁻⁶ cm² s⁻¹).     

Pre-concentration and separation of heavy metal ions by chemically modified waste paper gel

Iminodiacetic acid was immobilized on waste paper by chemical modification in order to develop a new type of adsorption gel for heavy metal ions. Adsorption behavior of the gel was investigated for a number of metal ions, specifically Cu(II), Pb(II), Fe(III), Ni(II), Cd(II), and Co(II) at acidic pH. From batch adsorption tests, the order of selectivity was found to be as follows: Cu(II)  Fe(III) > Pb(II) > Ni(II)  Co(II) > Cd(II). Column tests were carried out for pairs of metal ions to understand the separation and pre-concentration behavior of the gel. It was found that mutual separation of Ni(II) from Co(II) and that of Pb(II) from Cd(II) can be achieved at pH 3. Similarly, selective separation of Cu(II) from Cu(II)–Fe(III) and Cu(II)–Pb(II) mixtures at pH 1.5 and 2, respectively, was observed by using this new adsorption gel. In all cases, almost complete recovery of the adsorbed metal was confirmed by elution tests with HCl.     

Characterizing the interactions between polycyclic aromatic hydrocarbons and fulvic acids in water

Polycyclic aromatic hydrocarbons (PAHs) are persistent, bioaccumulative, and toxic chemicals and are listed as priority pollutants by the US EPA. Although they are sparsely soluble in water, their solubility can be increased by binding to dissolved organic matter in natural waters, which will further increase their environmental risk as toxic pollutants. In this study, the interaction between PAHs, exemplified by fluorene and anthracene, and fulvic acid (FA) was studied using fluorescence quenching titration method with fluorescence emission spectra, respectively. The association of FA with the mixture of fluorene and anthracene was also evaluated by excitation–emission matrix (EEM) fluorescence spectrometry combined with parallel factor (PARAFAC) analysis. Results demonstrate that EEM fluorescence spectrometry with PARAFAC analysis was sensitive and reliable to determine the binding properties of PAHs with FA in a mixed aqueous solution. The conditional stability constants and binding capacities show that both PAHs bind to FA tightly.     

Quantification of the interactions between Ca,Hg and extracellular polymeric substances (EPS) of sludge

The interactions between metals (Ca²⁺ and Hg²⁺) and extracellular polymeric substances (EPS) extracted from the aerobic and anaerobic sludge in wastewater treatment reactors were investigated using a combination of zeta potential measurement and 3-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analysis. Results show that Ca²⁺ had no substantial effects on the EEM fluorescence spectra of the EPS, but their zeta potentials increased with the increasing Ca²⁺ dosage. However, Hg²⁺ had a significant effect on the EEM fluorescence spectra of the EPS, while their zeta potentials seemed not to be affected by the dose of Hg²⁺. The interactions between Hg²⁺ and EPS were elucidated using the fluorescence quenching with PARAFAC analysis, while the interactions between Ca²⁺ and EPS were evaluated by the zeta potential technique. The binding constants for Hg²⁺ and EPS were two orders of magnitude higher than those for Ca²⁺ and EPS, suggesting that the binding mechanisms between Ca²⁺ and EPS were different from those between Hg²⁺ and EPS. The results might be useful for understanding the roles of EPS in bacterial self-protection against heavy metals and the aggregate formation mechanisms through ionic bridging interactions.     

Use of diffuse reflectance spectrometry in spot test reactions for quantitative determination of cations in water

Diffuse reflectance spectroscopy can be successfully used for the quantitative determination of small amounts of pollutants like metals. The remission function was found to be linearly proportional to the concentration, when we applied the Kubelka–Munk equation. The color reactions of Cu(II), Co(II), and Ni(II) with dithiooxamide, were realised on filter paper. Reaction between Fe(III) and ammonium thiocyanate was realized on filter paper and gelatine matrix. All measurements were accomplished with a laboratory-constructed reflectometer. We have obtained a calibration curve by plotting the optical density of reflectance A_R vs log of the mol l⁻¹ concentration. Limits of detection at the 10⁻⁴ M level were estimated for all the compounds. Linear dynamic range extend over one order of magnitude and shows the potential of device for the quantitative analysis of environmental pollutants.     

Dissolved organic matter with multi-peak fluorophores in landfill leachate

Dissolved organic matter (DOM) sampled from municipal landfill leachate of different ages with/without anoxic or aerobic treatment, was intensively fractionated via size exclusion chromatography (SEC) and hydrophobic resins, and was studied with fluorescence excitation and emission matrix (EEM). Six fluorophores with multiple EEM peaks (fluorophore A-F) were identified based on the collected EEM spectra and validated by bi-variate analysis, principal component analysis, and parallel factor analysis, as follows (excitation wavelength Ex and emission wavelength Em): (Ex 240, 310, 360 nm, Em 460 nm), (Ex 220, 280 nm, Em 340 nm), (Ex 220, 270 nm, Em 300 nm), (Ex 220, 280 nm, Em 360 nm), (Ex 230, 320 nm, Em 420 nm) and (Ex 220, 310 nm, Em 400 nm). The spectral characteristics of these fluorophores were discussed using fractional EEM and apparent molecular weight (AMW) data obtained via SEC analysis. The triple peak flurophore A was pointed at a hydrophobic acid or hydrophobic neutral compound with a pyrenyl functional group of AMW 2500-3500 Da, which displayed an excitation wavelength at 360 nm and a fluorescence intensity ratio of 6.70(+/-1.79):1.70(+/-0.41):1 (fluorescent intensities of Ex 240:Ex 310:Ex 360 nm at Ex 460 nm). This compound is observed to be refractory in landfilling or in anoxic/aerobic treatments, and is specific to this leachate contamination. This paper revealed that the coupling of SEC and EEM can be useful to track the fluorescent DOM fraction in landfill leachate.     

Removal of Ni(II) and Cu(II) ions using native and acid treated Ni-hyperaccumulator plant Alyssum discolor from Turkish serpentine soil

Alyssum discolor biomass was collected from serpentine soil and was used for removal of metal ions. The plant species grown on serpentine soils are known to be rich with metals ions and thus have more capability for accumulating heavy metals. Native and acid-treated biomass of A. discolor (A. discolor) were utilized for the removal of Ni(II) and Cu(II) ions from aqueous solutions. The effects of contact time, initial concentration, and pH on the biosorption of Ni(II) and Cu(II) ions were investigated. Biosorption equilibrium was established in about 60 min. The surface properties of the biomass preparations were varied with pH, and the maximum amounts of Ni(II) and Cu(II) ions on both A. discolor biomass preparations were adsorbed at pH 5.0. The maximum biosorption capacities of the native, and acid-treated biomass preparations for Ni(II) were 13.1 and 34.7 mg g⁻¹ and for Cu(II) 6.15 and 17.8 mg g⁻¹ dry biomass, respectively. The biosorption of Ni(II) and Cu(II) ions from single and binary component systems can be successfully described by Langmuir and Freundlich isotherms. When the heavy metal ions were in competition, the amounts of biosorbed metal ions on the acid treated plant biomass were found to be 0.542 mmol g⁻¹ for Ni(II) and 0.162 mmol g⁻¹ for Cu(II), the A. discolor biomass was significantly selective for Ni(II) ions. The information gained from these studies was expected to indicate whether the native, and acid-treated forms can have the potential to be used for the removal and recovery of Ni(II) ions from wastewaters.     

Characterizing the heavy metal-complexing potential of fluorescent water-extractable organic matter from composted municipal solid wastes using fluorescence excitation–emission matrix spectra coupled with parallel factor analysis

To investigate the effect of organic matter evolution on heavy metal sorption, fluorescence excitation–emission matrix (EEM) spectra combined with parallel factor (PARAFAC) analysis were employed to characterize the evolution and metal-complexing potential of fluorescent water-extractable organic matter (WEOM) from composted municipal solid wastes (MSWs). The WEOMs examined comprised humic-, fulvic-, tryptophan-, and tyrosine-like substances. Composting treatment increased the content of humic- and fulvic-like matter, and changed the existence pattern of tryptophan- and tyrosine-like substances (i.e., the tryptophan- and tyrosine-like substances from uncomposted MSWs were mainly bound in protein-like matter, whereas those from composted MSWs were primarily bound in humic- and fulvic-like substances). Furthermore, composting treatment increased the polar functional group, aromaticity, and humification degree of the WEOMs, but decreased the aliphatic and hydroxyl group. These evolutions decreased the Cu(II) affinities of fulvic- and humic-like substances and the Pb(II) affinities and complexing capacities of fulvic-like substances, but increased the Cu(II) complexing capacities of fulvic- and humic-like substances. These results reveal that mature composts from the MSWs can be used for the remediation of Cu- and Pb-contaminated soils in situ, whereas immature composts can enhance the metal transferability from soil to plant.     

Copper complexation by dissolved organic matter and uncertainty assessment of their stability constants

The interaction of Cu with dissolved organic matter (DOM, extracted from an organic forest floor) was investigated and the resulting data was evaluated in terms of their uncertainty. The speciation of Cu over ‘free’ Cu (as analysed by diffusive gradients in thin films (DGT)), dissolved Cu–DOM complexes and precipitated Cu–DOM was determined as a function of pH (3.5, 4.0 and 4.5) and Cu/C ratio. The dissolved organically bound fraction was highest at pH 4.5, but this fraction decreased with increasing Cu/C ratio, which was observed for all pH levels. In the range of Cu/C=7×10⁻⁵–2.3×10⁻² (mol/mol) the precipitated fraction was very small. The speciation of both Al and Fe was not affected by increasing Cu concentrations. From a continuous distribution model using the Scatchard approach, we calculated the optimal fit and corresponding upper and lower 95% uncertainty bounds of the overall stability constants (K_o) with the shuffled complex evolution Metropolis (SCEM) algorithm. Although the optimal equation fitted the data very well, the uncertainty of the, according to literature, most reliable approach to establish stability constants, was still large. Accordingly, the usually reported intrinsic stability constants exhibited large uncertainty ranging from logK_i=6.0–7.1 (optimal 6.7) for pH 3.5, logK_i=6.5–7.1 (optimal 6.8) for pH 4.0, and logK_i=6.4–7.2 (optimal 6.8) for pH 4.5 and showed only little effect of pH.     

Characterization of primary precipitate composition formed during co-removal of Cr(VI) with Cu(II) in synthetic wastewater

BACKGROUND, AIMS AND SCOPE: Hexavalent chromium [Cr(VI)] cannot react with either carbonate or hydroxide to form chromium precipitates. However, by using a precipitation technology to treat plating wastewater containing Cr(VI), Cu(II), Ni(II) and Zn(II), approximately 78% of Cr(VI) (initial 60 mg/L) was co-removed with the precipitation of Cu(II), Ni(II) and Zn(II) (each 150 mg/L) by dosing with Na2CO3 (Sun 2003). Direct precipitation by forming Cu(II)-Cr(VI) precipitates followed by adsorption of Cr(VI) onto freshly formed Cu-precipitates was subsequently found to be the main mechanism(s) involved in Cr(VI) co-removal with Cu(II) precipitation by dosing Na2CO3 stepwise to various pH values (Sun et al. 2003). This study was. carried out to further characterize the formation of primary precipitates during the early stages of copper precipitation and simultaneous removal of Cr(VI) with Cu(II). METHODS: Test metal-solutions were prepared with industrial grade chemicals: CuCl2 x 2H2O, Na2SO4 and K2Cr2207. NaCO3 was added drop-wise to synthetic metal-solution to progressively increase pH. For each pH increment, removal of soluble metals was detected by atomic absorption spectrophotometer (AAS) and surface morphology of precipitates was analyzed by scanning electron microscope (SEM). To further characterize the formation of primary precipitates, a series of MINEQL+ thermodynamic calculations/analyses and equilibrium calculations/ analyses were conducted. RESULTS AND DISCUSSION: MINEQL+ thermodynamic calculation indicated that, for a system containing 150 mg/L Cu(II) and 60 mg/L Cr(VI) with gradual Na2CO3 dosing, if any precipitates can be formed at pH 5.0 or lower, it should be in the form of CuCrO4. Comparison tests using systems containing the same equivalent of Cu(II) plus Cr(VI) and Cu(II) plus SO4(2-) showed that the precipitation occurred at a pH of around 5.0 in the Cu(II)-Cr(VI) system and around 6.0 in the Cu(II)-SO4(2-) system. The discrepancy of the precipitation was indeed caused by the formation of Cu-Cr precipitates. The initiation of copper removal at pH around 5.0 for the Cu-Cr co-removal test was not attributable to the formation of Cu-CO3 precipitates, instead, it was most likely through the formation of insoluble Cu-Cr precipitates, such as CuCrO4 and CuCrO4 x 2Cu(OH)2. Experimental tests, equilibrium calculations, MINEQL+ thermodynamic calculations and surface morphologies for systems using higher concentrations of Cu(II) and Cr(VI) further verified the most probable composition of primary precipitates is copper-chromate. CONCLUSION: In the Cu-Cr co-removal test with Na2O3 dosing to increase pH and induce metal precipitation, copper-chromate precipitates are the primary precipitates produced and contribute to the initial simultaneous removal of copper and chromium.     

Baseline study of methane emission from open digesting tanks of palm oil mill effluent treatment

Anthropogenic release of greenhouse gases, especially CO₂ and CH₄ has been recognized as one of the main causes of global warming. Several measures under the Kyoto Protocol 1997 have been drawn up to reduce the greenhouse gases emission. One of the measures is Clean Development Mechanisms (CDM) that was created to enable developed countries to cooperate with developing countries in emission reduction activities. In Malaysia, palm oil industry particularly from palm oil mill effluent (POME) anaerobic treatment has been identified as an important source of CH₄. However, there is no study to quantify the actual CH₄ emission from the commercial scale wastewater treatment facility. Hence, this paper shall address the CH₄ emission from the open digesting tanks in Felda Serting Hilir Palm Oil Mill. CH₄ emission pattern was recorded for 52 weeks from 3600 m³ open digesting tanks. The findings indicated that the CH₄ content was between 13.5% and 49.0% which was lower than the value of 65% reported earlier. The biogas flow rate ranged between 0.8 l min⁻¹ m⁻² and 9.8 l min⁻¹ m⁻². Total CH₄ emission per open digesting tank was 518.9 kg day⁻¹. Relationships between CH₄ emission and total carbon removal and POME discharged were also discussed. Fluctuation of biogas production was observed throughout the studies as a result of seasonal oil palm cropping, mill activities, variation of POME quality and quantity discharged from the mill. Thus only through long-term field measurement CH₄ emission can be accurately estimated.     

Bioaccumulation of anthropogenic contaminants by detritivorous fish in the Río de la Plata estuary: 1-aliphatic hydrocarbons

The temporal variability and bioaccumulation dynamics of C_12–25 n-alkanes, isoprenoids and unresolved aliphatic hydrocarbons (UCM) were studied in a detritivorous fish (Sábalo: Prochilodus lineatus) collected from 1999 to 2005 in the sewage impacted Buenos Aires coastal area. Fish muscles contain huge amounts of n-C_12–25 (165 ± 93, 70 ± 48 or 280 ± 134 μg g⁻¹, dry, fresh and lipid weight, respectively) and UCM (931 ± 560, 399 ± 288 and 1567 ± 802 μg g⁻¹) reflecting the chronic bioaccumulation of fossil fuels from sewage particulates. On a temporal basis, lipid normalized aliphatic concentrations peaked by the end of 2001–2002 during the rainiest period over the last four decades (1750 vs. 1083 ± 4.6 mm in 1999, 2004 and 2005), reflecting an enhanced exposition due to massive anthropogenic fluxes from Metropolitan Buenos Aires in wet years. The hydrocarbon composition in fish muscles is enriched in n-C_15–17 and isoprenoids relative to a fresh crude oil and settling particulates, with fresher signatures during the 2001–2002 maxima. Fish/settling material bioaccumulation factors (BAFs: 0.4–6.4 dry weight or 0.07–0.94 lipid-organic carbon) plotted against K_ow showed a parabolic pattern maximizing at n-C_14–18 and isoprenoids. The optimal bioaccumulation window corresponds to highly hydrophobic (log K_ow: 7.2–9.9), intermediate-size C_14–18 n-alkanes and C_15–20 isoprenoids (MW: 198–282; length: 17.9 to 25.4 Å) with melting points ranging from −19.8 to 28 °C. The uptake efficiency is inversely correlated to melting points and increased from 75% for n-C₂₅ to above 90% for n-C_14–15 and isoprenoids.