Perennial plant communities in the proximity of metal smelters and refineries may receive substantial inputs of base metal particulate as well as sulphate from the co-emission of sulphur dioxide. The Ni refinery at Port Colborne (Canada) operated by Inco (now Vale Canada Ltd.) emitted Ni, Co and Cu, along with sulphur dioxide, between 1918 and 1984. The objectives were to determine if vascular plant community composition, including standing litter, in twenty-one woodlots on clay or organic soil, were related to soil Ni concentration which decreased in concentration with distance from the Ni refinery. The soil Ni concentration in the clay woodlots ranged from 16 to 4130 mg Ni/kg, and in the organic woodlots, ranged from 98 to 22,700 mg Ni/kg. The concentrations of Co and Cu in the soils were also elevated, and highly correlated with soil Ni concentration. In consequence, each series of woodlots constituted a ‘fixed ratio ray’ of metal mixture exposure. For each of the woodlots, there were 16 independent measurements of ‘woodlot status’ which were correlated with elevated soil Ni concentration. Of the 32 combinations, there were eight linear correlations with soil Ni concentration, considerably more than would be expected by chance alone at a p-value of 0.05. With the exception of mean crown rating for shrubs at the clay sites, the correlations were consistent with the hypothesis that increased soil metal concentrations would be correlated with decreased diversity, plant community health or fitness, and increased accumulation of litter. Only five of the eight linear correlations were from the organic woodlots, suggesting that the observations were not confounded with soil type nor range in soil metal concentrations.

The characteristics and mechanisms of competitive adsorption of trace metals on bacteria-associated clay mineral composites have never been studied, despite their being among the most common organic–mineral complexes in geological systems. Herein, competitive adsorption of Pb and Cd on Pseudomonas putida–montmorillonite composite was investigated through adsorption–desorption experiment, isothermal titration calorimetry (ITC), and synchrotron micro X-ray fluorescence (μ-XRF). From the experiment, stronger competition was observed on clay mineral than on bacteria–clay composite because more non-specific sites accounted for heavy metal adsorption on clay mineral surface at the studied pH 5. Both competing heavy metals tended to react with bacterial fractions in the composite, which was verified by the higher correlation of Cd (and Pb) with Zn (R2 = 0.41) elemental distribution than with Si (R2 = 0.10). ITC results showed that competitive adsorption exhibited a lower entropy change (ΔS) at the metal-sorbent interfaces compared with single-metal adsorption, revealing that Cd and Pb are bound to the same types of adsorption sites on the sorbent. The competitive effect on bacteria–clay composite was found to be helpful for a better understanding on the fixation, remobilization and subsequent migration of heavy metals in multi-metal contaminated environments.

Many lakes and rivers are enriched with high levels of suspended sediments (SPS). Denitrification occurring on suspended sediments (DSS) may play an important role in nitrogen removal in water columns with high SPS concentrations. Poyang Lake, with dramatic hydrologic variations, has high spatial and seasonal variation of SPS, and we hypothesized that DSS and nitrogen removal in this lake would vary similarly. DSS in Poyang Lake was determined by the traditional acetylene-inhibition method combined with a batch mode assay. Laboratory simulation experiments were also conducted to examine the factors controlling denitrification occurring on SPS. Seasonally, DSS rates at 15 sampling sites in Poyang Lake were 0.63 ± 0.24, 0.29 ± 0.17, 0.25 ± 0.18, and 0.52 ± 0.37 μmol N·L−1·d−1, respectively in spring, summer, autumn, and winter. Spatially, average DSS rates were higher in the northern lake area, which is connected to the Yangtze River, than in the upstream and central lake area. Lowest DSS rates occurred in semi-closed bay and dish lakes. Spatial and seasonal variations of DSS rates were affected by a combination of factors, in which nitrate concentrations, SPS composition, and concentrations of organic-SPS were the most important. These influencing factors were seasonally dependent, with nitrate concentrations having stronger effects on DSS during wet seasons than dry seasons. Results from a multiple stepwise regression model also demonstrated that DSS tended to occur on fine particles (e.g., clay particles, <4 μm). Evaluation of annual nitrogen loss by DSS was estimated according to the seasonal water budget and DSS rates in Poyang Lake. The total nitrogen loss by DSS was estimated to be 10800 ± 6090 t, which accounted for 2.8–9.9% of the nitrogen input, and this proportion was comparable to nitrogen removal by sediment denitrification. This result confirms that DSS was an important nitrogen sink in this large, turbid lake.

Addressing the challenge that phosphorus is the key factor and cause for eutrophication, we evaluated the phosphorus release control performance of a new phosphorus inactive clay (PIC) and compared with Phoslock®. Meanwhile, the impacts of PIC and Phoslock® on phytoplankton abundance and community structure in eutrophic water were also discussed. With the dosage of 40 mg/L, PIC effectively removed 97.7% of total phosphorus (TP) and 98.3% of soluble reactive phosphorus (SRP) in eutrophic waters. In sediments, Fe/Al-phosphorus and organic phosphorus remained stable whereas Ca-phosphorus had a significant increase of 13.1%. The results indicated that PIC may form the active overlay at water-sediment interface and decrease the bioavailability of phosphorus. The phytoplankton abundance was significantly reduced by PIC and decreased from (1.0–2.4) × 107 cells/L to (1.3–4.3) × 106 cells/L after 15 d simultaneous experiment. The phytoplankton community structure was also altered, where Cyanobacteria and Bacillariophyceae were the most inhibited and less dominant due to their sensitivity to phosphorus. After PIC treatment, the residual lanthanum concentration in water was 1.44–3.79 μg/L, and the residual aluminium concentration was low as 101.26–103.72 μg/L, which was much less than the recommended concentration of 200 μg/L. This study suggests that PIC is an appropriate material for phosphorus inactivation and algal bloom control, meaning its huge potential application in eutrophication restoration and management.

The performances of aluminum chloride modified clay (AC-MC), aluminum sulfate modified clay (AS-MC) and polyaluminum chloride modified clay (PAC-MC) in the removal of Aureococcus anophagefferens were compared, and the potential mechanisms were analyzed according to the dispersion medium, suspension pH and clay surface charges. The results showed that AC-MC and AS-MC had better efficiencies in removing A.anophagefferens than PAC-MC. The removal mechanisms of the three modified clays varied. At optimal coagulation conditions, the hydrolysates of AC and AS were mainly monomers, and they transformed into Al(OH)3(am) upon their addition to algae culture, with the primary mechanism being sweep flocculation. The PAC mainly hydrolyzed to the polyaluminum compounds, which remained stable when added to the algae culture, and the flocculation mainly occurred through polyaluminum compounds. The suspension pH significantly influenced the aluminum hydrolysate and affected the flocculation between the modified clay and algae cells.

Hurricane Sandy made landfall in Barnegat Bay, October, 29, 2012, damaging shorelines and infrastructure. Estuarine sediment chemistry and toxicity were investigated before and after to evaluate potential environmental health impacts and to establish post-event baseline sediment-quality conditions. Trace element concentrations increased throughout Barnegat Bay up to two orders of magnitude, especially north of Barnegat Inlet, consistent with northward redistribution of silt. Loss of organic compounds, clay, and organic carbon is consistent with sediment winnowing and transport through the inlets and sediment transport modeling results. The number of sites exceeding sediment quality guidance levels for trace elements tripled post-Sandy. Sediment toxicity post-Sandy was mostly unaffected relative to pre-Sandy conditions, but at the site with the greatest relative increase for trace elements, survival rate of the test amphipod decreased (indicating degradation). This study would not have been possible without comprehensive baseline data enabling the evaluation of storm-derived changes in sediment quality.

Sediment samples from the ballast water tanks of ships calling at the port of Rijeka in the Northern Adriatic were analysed using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) using caesium, argon and oxygen ion beams. The research was carried out in order to determine the sediment composition and relative abundance of the dominant elements. The results indicate that the sediment samples mostly consisted of compounds that originated from the deterioration of tank plates, tank coating residues and ballast operations such as clay, silt, sand and organic materials. No significant heavy metals or highly toxic elements were found. The research revealed some advantages and significant drawbacks of using XPS and SIMS for the routine analysis of sediment composition as a decision supporting tool for ballast water and sediment management.

Acid mine drainage (AMD) is a persisting environmental problem and a grievous nuisance in the mining sector. In this study, iron (Fe(II)) removal was tested in AMD samples collected from the Enugu Okpara abandoned coal mine (Nigeria), having iron concentrations of ∼1300 mg/l. Digestion, toxicity characteristic leaching procedure (TCLP), and batch adsorption tests using coal bottom ash (BA), bentonite clay (BC), and coal fly ash (FA) were performed. Apart from elucidating the effects of adsorbent dose and initial Fe(II) concentrations on the maximum adsorption capacity (q ₑ) of the adsorbents, the experimental data were also fitted to well-known adsorption isotherms and kinetic models. The results from batch tests showed that the optimum adsorbent dosages for BA, BC, and FA were found to be 3, 4, and 4 g per 100 ml, respectively. Among the different adsorption isotherm models tested, the Temkin model fitted the experimental data well for Fe(II) removal. Results from kinetic analysis showed that the Fe(II) removal efficiency increased with an increase in the contact time and then remained almost constant after 30 min for the three tested adsorbents.

The effectiveness of gemini-modified palygorskite (PGS) as the novel remediation material in polycyclic aromatic hydrocarbons (PAHs)-contaminated water remediation was revealed and examined. The sorption behavior of gemini surfactants at the PGS/aqueous interface was addressed using a developed two-step adsorption and partition model (TAPM). The characterizations of gemini-modified PGS were investigated using infrared spectroscopy, cationic exchange capacity, and surface area analysis. The effects of pH, ionic strength, humic acid, and temperature on sorption of phenanthrene (PHE) to untreated and modified PGS were systematically studied. Analysis of the equilibrium data indicated that the sorption isotherms of gemini fitted TAPM well. The modification of PGS with gemini surfactants provided a favorable partition medium for PHE and enhanced PHE retention in solid particles. The solution parameters played significant effects on PHE sorption to the modified PGS. The sorption isotherms of PHE on PGS at different temperatures well fitted the Freundlich equation. Thermodynamic calculations confirmed that the sorption process of PHE on modified PGS was spontaneous and exothermic from 293 to 303 K. It is revealed that the modification with gemini surfactants probably offered some unique surface characteristics to the clay mineral as a new type of remediation material. This can provide a reference to the potential application of PGS in PAH-contaminated water remediation process.

Fibrous mats of polymer/clay were obtained by electrospinning method, and their capacity for heavy metals removal from water was evaluated. Four different fibrous mats were prepared from a corresponding polymer/clay solutions. The precursor materials employed were poly-ε-caprolactone, polyvinyl alcohol polymers, kaolin, and metakaolin clays. Raw materials and the prepared fiber mats characterization were carried out using scanning electron microscopy, Fourier transformed infrared spectroscopy, X-ray diffraction, termogravimetric analysis, differential thermal analysis, and differential scanning calorimetry. Elemental composition of the materials was obtained using energy-dispersive X-ray spectroscopy. The environmental applications of polymer/clay materials were tested for water treatment by heavy metals (cadmium (Cd⁺²), chromium (Cr⁺³), copper (Cu⁺²), and lead (Pb⁺²)) sorption. Kinetic adsorption studies were conducted employing heavy metal solutions with initial concentration of 200 mg/L, and the amount of heavy metal adsorbed and kinetics parameters was determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES). According to the kinetic data, the adsorption process of Cd⁺², Cr⁺³, Cu⁺², and Pb⁺² onto polymer/clay is favorable for the prepared materials and they follow a pseudo-first-order model according to the kinetic analysis. Additionally, the intraparticle diffusion was evaluated by applying the Morris and Weber model; in order to investigate the contribution of film resistance to the kinetics of the heavy metals adsorption, the adsorption kinetic data was further analyzed by Boyd’s film-diffusion model.