In this work, the potential removal of Cd, Cu, and Zn ions by non-living macrophytes Egeria densa has been studied. The adsorption kinetic and equilibrium experiments of these three metals on E. densa were performed in batch systems with controlled temperature and constant shaking. It was observed that all metal adsorption rates have increased when the pH was increasing. A pH threshold of 5 was established for use in adsorption experiments in order to avoid the metal precipitation. For adsorption kinetic tests, the equilibrium times for all metals were around 45 to 60 min. The equilibrium data at pH 5 were better described by the Langmuir isotherm than the Freundlich one, with the adsorption rate and maximum metal content values of 0.43 L g⁻¹ and 1.25 mequiv g⁻¹ for Cd, 4.11 L g⁻⁻¹ and 1.43 mequiv g⁻¹ for Cu, and 0.83 L g⁻¹ and 0.93 mequiv g⁻¹ for Zn. These adsorption parameters for E. densa resemble or are better than those for other biosorbents already studied, suggesting that the macrophytes E. densa as a biosorbent has a good metal removal potential for applications in effluent treatment systems.

The concentrations and distribution of selected heavy metals in epipelic and benthic sediments of Cross River Estuary mangrove swamp were studied to determine the extent of anthropogenic inputs from industrial activities and to estimate the effects of seasonal variations on geochemical processes in this tropical estuarine ecosystem. The analysis shows that the mean concentrations (mg/kg, dw) of Cu, Cr, Fe, Ni, Pb, V and Zn vary from 24.1-32.4, 19.9-27.4, 666.7-943.5, 15.2-30.3, 8.8-24.7, 2.2-6.9 and 140.1-188.9, respectively. An important observation is that, in general, lowest metal concentrations are found during the dry season, compared to wet season. Pollution load index (PLI) and index of geoaccumulation (I geo) revealed overall low values but the enrichment factors (EFs) for Cr, Zn, and V were high, and this reflects the intensity of anthropogenic inputs related to industrial discharge into the estuary. The mean concentrations of Zn, Cu and to some extent Ni exceeded the Effects Range--Low (ERL) and Threshold Effect Level (TEL) values in majority of the samples studied, indicating that there may be some ecotoxicological risk to organisms living in these sediments. The inter-element relationship revealed the identical source of elements in the sediments of the studied area. The concentration of heavy metals reported in this work will be useful as baselines for comparison in future sediment quality studies.

Naphthenic acids (NAs) are a complex group of naturally occurring oil sands constituents that constitute a significant portion of the dissolved organic carbon (DOC) pool available for microbial degradation in the process-related waste water associated with oil sands mine sites. One approach to understanding the biological fate of oil sands process-derived carbon and nitrogen in aquatic reclamation of the mine sites involves the use of stable isotope analyses. However, for stable isotope analyses to be useful in such field-based assessments, there is a need to determine how microbial degradation of a complex mixture of NAs might change the stable isotope values (δ ¹³C, δ ¹⁵N). In batch cultures and semi-continuous laboratory microcosms, utilization of a commercial mixture of NAs by oil sands-derived microbial cultures resulted in microbial biomass that was similar or slightly ¹³C enriched (1.4[per thousand] to 3.0[per thousand]) relative to the DOC source, depending on the length of incubation. Utilization of a NA-containing extract of oil sands processed water resulted in greater ¹³C enrichment of microbial biomass (8.5[per thousand]) relative to the DOC source. Overall, the δ ¹³C of the DOC comprised of complex mixtures of NAs showed minimal change (-0.5[per thousand] to -0.1[per thousand]) during the incubation period whereas the δ ¹³C of the dissolved inorganic carbon (DIC) was more variable (-5.0[per thousand] to +5.4[per thousand]). In tests where the concentration of available nitrogen was increased, the final biomass values were ¹⁵N enriched (3.8[per thousand] to 8.4[per thousand]) relative to the initial biomass. The isotope trends established in this study should enhance our ability to interpret field-based data from sites with hydrocarbon contamination, particularly in terms of carbon source utilization and ¹⁵N enrichment.

A box-core 3576 (PO287-26-1B) collected from the Tagus Prodelta in 2002 was analysed for organic carbon, ²¹⁰Pb, ²²⁶Ra, major (Al, Fe, Ca, Ti, Mg and Mn) and trace elements (Ba, Hg, Cr, Cu, Li, Ni, Pb, Sb, Sn, Sr, and Zn). Maximum concentrations of contaminants in ²¹⁰Pb-dated samples were reached in the decades between 1960 and 1980, followed by a slightly decrease in up-core metal trends. Trace metal concentrations increased in the bottom of the core (²¹⁰Pb dated as 1925) to maximum values during the 1970s. Factor analysis of geochemical data was used to reduce the 18 variables into four factors that reveal distinct origins or accumulation mechanisms controlling the chemical composition in the study area. Changes in the dominance of these factors through the time indicate not only changes in industrial activity, but also the increase of biological productivity towards the present.

To evaluate the phytoremediation capability of some poplar and willow clones a hydroponic screening for cadmium tolerance, accumulation and translocation was performed. Rooted cuttings were exposed for 3 weeks to 50 μM cadmium sulphate in a growth chamber and morpho-physiological parameters and cadmium content distribution in various parts of the plant were evaluated. Total leaf area and root characteristics in clones and species were affected by cadmium treatment in different ways. Poplar clones showed a remarkable variability whereas willow clones were observed to be more homogeneous in cadmium accumulation and distribution. This behaviour was further confirmed by the calculation of the bio-concentration factor (BCF) and the translocation factor (Tf). Mean values of all the clones of the two Salicaceae species showed that willows had a far greater ability to tolerate cadmium than poplars, as indicated by the tolerance index (Ti), calculated on the dry weight of roots and shoots of plants. As far as the mean values of Tf was concerned, the capacity of willows to translocate was double that of poplars. On the contrary, the mean values of total BCF in poplar clones was far higher with respect to those in willows. The implications of these results in the selection of Salicaceae clones for phytoremediation purposes were discussed.

The lability and mobility of Zn(II)-, Cd(II)-, Pb(II)-, and Cu(II)-humic acid complexes were studied using diffusive gradients in thin films (DGT). A unique feature of this research was (1) the use of DGTs with diffusive layer thicknesses ranging from 0.4 to 2.0 mm to study lability and mobility of Zn(II)-, Cd(II)-, Pb(II)-, and Cu(II)-humic acid complexes, combined with (2) the application of a competing ligand exchange (CLE) method using Chelex 100, the same chelating resin that is used in DGT, to study the kinetic speciation. The CLE experiments were run immediately after the completion of the DGT experiments, thereby allowing effects of the competing ligand to be separated from the effects introduced by the use of the polyacrylamide gel that is used in DGT. The results indicate that Zn(II) and Cd(II) tend to form more labile and more mobile complexes with humic acid than Pb(II) or Cu(II). The dissociation rate constants of Zn(II), Cd(II), and Pb(II) were found to increase with the ionic potential of the metal, suggesting that the binding between some trace metals and humic acid has a significant covalent component. Furthermore, the results suggest that the Eigen mechanism may not be strictly obeyed for metals such as Cu(II) which have high rate constants of water exchange, k w. Consequently, the markedly slow kinetics of Cu(II)-HA species suggests that the usual equilibrium assumption may not be valid in freshwaters.

The solubility and the enthalpy of dicarboxylic acids have been determined in water at intervals between 278.5 and 543.5 K. At 298.15 K, the values derived were: Δsol H m (m = 1.33 mol kg⁻¹) = 29.80 kJ mol⁻¹for oxalic acid; Δsol H m (m = 16.03 mol kg⁻¹) = 12.82 kJ mol⁻¹ for malonic acid; Δsol H m (m = 0.75 mol kg⁻¹) = 28.20 kJ mol⁻¹ for succinic acid; Δsol H m (m = 8.77 mol kg⁻¹) = 48.01 kJ mol⁻¹ and Δsol H m (m = 0.17 mol kg⁻¹) = 40.30 kJ mol⁻¹ for glutaric and adipic acid respectively. The solubility value exhibits a prominent odd-even effect with respect to terms with even number of carbon atoms with the odd carbon numbers showing much higher solubility. Observations made in the atmospheres suggest that this odd-even effect may have implications for the relative abundance of these acids in aerosols.

The use of vermicompost was expanded as natural adsorbent for cationic dyes retention. The adsorption profiles in batch and flow modes for crystal violet and methylene blue on vermicompost material were evaluated. In batch mode, a retention index higher than 97% was obtained for both compounds, while in flow condition, 40 g of dried adsorbent material were enough to remove 100 mg of crystal violet or methylene blue at column flow rates of 5 and 20 mL min⁻¹. Adsorption isotherms showed adsorptive maximum capacities for vermicompost of 0.78 and 5.47 mg g⁻¹, respectively, which were compatible with the literature. Due to this good efficiency capacity, incineration steps can be considered as acceptable disposal procedures for enriched vermicompost. From these characteristics, economical and environmental advantages of the proposed material for the evaluated cationic dyes retention were evidenced.

Lura stream flows in the populated and industrialized conurbation North of Milan, Italy. The area suffers a sprawling urbanization which is leading to major alterations in water quality, hydrology and morphology of streams. These water bodies are known as effluent-dominated streams, because most of the baseflow is given by Wastewater Treatment Plant (WWTP) discharges. In this paper, a 5 year long assessment of Lura stream is presented and the collected data is discussed to understand overall ecological quality. Multivariate analysis carried out on macroinvertebrate assemblages and environmental variables suggests that invertebrate communities suffer severe alteration both upstream and downstream WWTP discharges. Results indicate that the high polluting loads coming from WWTP discharges affect seriously the stream water quality, but the most important cause of impairment are pulse perturbations related to the modified hydrology, causing droughts and flash floods, and to the spills of untreated sewage from overflows during rain events.

Sediment cores were collected from the central and northern parts of Lake Dianchi, a large and shallow eutrophic lake situated in southwest China. Total organic carbon, total nitrogen (TN), and total phosphorus (TP) as well as the δ¹³C and δ¹⁵N were analyzed in the sediment cores. Age model of the sediment cores were established according to ¹³⁷Cs geochronology, which reveals that the sedimentary record covers a period of the last 50 years. During that time, Dianchi had been undergoing a distinct conversion from oligotrophic to eutrophic, as a result of increasing nutrient loadings. The two cores displayed similar increases for values of TN and δ¹⁵N, and the variations of the both parameters matched well with that of TP, which presumably suggested that δ¹⁵N is a reliable proxy for anthropogenic nutrient input. Also, dynamics of δ¹⁵N and TP showed that anthropogenic nutrients input seemed to start in the 1970s. The upward elevation of δ¹⁵N might be ascribed to the increasing input of isotopically heavier dissolved inorganic nitrogen and the accelerated denitrification process when the lake water was oxygen-depleted. The less variation of δ¹⁵N in the uppermost several centimeters of both cores were probably the result of pollution controls carried out by the local government in the recent decade. The upward increasing of δ¹³C in the two cores seemed to be induced by the enhanced productivity since 1980, which was in accordance with limnological observation. Therefore, δ¹³C values were believed to be an effective proxy for reconstructing the history of eutrophication in Lake Dianchi. In addition, this study also suggested that carbon and nitrogen isotopes are applicable to large, shallow lakes in interpreting the past environmental change.