Sorption of benzo[a]pyrene to sediment contaminated by acid mine drainage: contrasting particle concentration-dependencies in river water and seawater

The sorption of benzo[a]pyrene (BaP) to sediment contaminated by acid mine drainage from the River Carnon, SW England, has been studied as a function of particle concentration in river water and seawater. The sediment is iron-rich and has a high specific surface area, and previous studies have demonstrated that it exhibits positive surface charge when suspended in native river water (pH approximately 5), and, through an increase in pH (to about 8) and the adsorption of organic matter, negative charge when suspended in seawater. Unit sorption of BaP exhibited an inverse dependency on particle concentration (particle concentration effect. PCE) in seawater, but was relatively invariant in river water. Consequently, BaP was apparently salted out at particle concentrations below about 100 mg l(-1), and salted in at higher particle concentrations. The absence of a PCE (and inherent salting in) for such a hydrophobic compound is an unusual, and possibly unique observation, and is inconsistent with a third (e.g. colloidal) phase model. More likely, a PCE in seawater is caused, in part, by salt induced particle-particle or particle-organic matter interactions which result in increasing particle aggregation or sorption irreversibility with increasing particle concentration. Although the results have limited environmental application and do not conclusively resolve any causal mechanisms for the PCE, they suggest that, with respect to neutral organic compounds, adsorbed organic matter is a pre-requisite for a PCE in the natural environment, and the effect should not solely or generally be attributed to the existence of a third phase.     

A contribution to environmental risk assessment for transport of cadmium through groundwater layers. Case study of the Sava river (near Zagreb, Croatia) region

Adsorption capacities of cadmium on aquifer material of the Sava River alluvial sediment were determined as a function of flow rate, pH and presence of organic coating using laboratory column technique. In a permeameter with constant hydrostatic pressure, a laboratory coefficient of permeability, K_l, and a specific coefficient of permeability, K_s, have been determined. The value of 28.6 Darcy for specific permeability shows that the sediment belongs to a good aquifer (permeability >1 Darcy). The adsorption capacity of cadmium at the bottom of the breakthrough curve, C_sb, of a fresh sediment at pH 5.8 varied from 0.40 to 0.45 mg g⁻¹ at axial flow rate between 98 and 501 cm h⁻¹. Capacity values of maximum adsorption, C_s, were in the range from 0.67 to 0.72 mg g⁻¹. This implies a significance of C_sb values in risk assessment studies concerning a discharge of cadmium into rivers and lakes and its input to groundwater layers. Distribution coefficients, K_d, were between 26.3 and 28.2 ml g⁻¹. In order to create a more reproducible column, a fraction between 125 and 250 μm was used. In that case C_s values varied from 0.25 mg g⁻¹ at pH 2.5 (organic coating present) to 1.12 mg g⁻¹ at pH 5.8 (organic coating removed).     

Sorption of chlorinated C1- and C2-hydrocarbons and monocyclic aromatic hydrocarbons on sea sediment

The sorption of chlorinated C₁- and C₂-hydrocarbons and monocyclic aromatic hydrocarbons on sea sediment was studied with a miscible displacement technique. Detection was done either by on-line UV-detection or off-line GC-analysis. Equilibrium partitioning coefficients between the salt water phase and the marine sediment were determined for 11 compounds by fitting their breakthrough curves to a local sorption equilibrium model. Based on the obtained partitioning coefficients and on the measurement of the organic carbon content of the sediment, the sorption into the organic carbon fraction was considered. Log K_oc data (K_oc = organic carbon-water partitioning coefficient) were calculated. A linear relationship between the log K_oc values and the log K_ow data (K_ow = octanol-water partitioning coefficient) was found (r = 0.94, n = 11). However, the sorption was lower than expected from the log K_ow data. Finally, the implications of the experimental results for the sorption behaviour of the compounds in the marine environment were evaluated. It was concluded that the sea sediment does not act as an important sink for these anthropogenic compounds.     

Seasonal variation of phosphorus release from the sediments of Shallow Lake Balaton (Hungary)

Phosphorus release was low from intact sediment cores of the mesotrophic area of the lake throughout the year, and amounted to 0.3 mg P m⁻² day⁻¹ during autumn in short-term incubations. In the hypertrophic area maximum release (2.8 mg Pm⁻² day⁻¹) was measured during summer.

Phosphorus release showed a rapid increase from long-term incubated intact sediment cores with the increasing pH of the overlying water. At the ecologically real maximum pH the release may amount to 0.8 and 4.0 mg P m⁻² day⁻¹ in the mesotrophic and hypertrophic areas, respectively. A release of 2.0–3.9 mg P m⁻² day⁻¹ was estimated from sediment suspensions of the hypertrophic area within a pH range of 8–9. These values are similar to the external phosphorus loadings of the respective areas.

The most important phosphorus mobilizing factors are pH and the decomposition of the organic matter in the sediments. Redox conditions may play a significant indirect role in the regulation of the internal loading.

A positive feedback is hypothesized between the internal phosphorus loading and primary production both processes being affected by the external loading in different ways.     

Sediment-water exchange in Lough Ennell with particular reference to phosphorus

The significance and evaluation of sediment phosphorus in the continuing eutropic conditions noted in Lough Ennell was assessed. A high positive correlation exists between the concentrations of total Fe, citrate dithionite bicarbonate (CDB) extractable Fe, organic content, total Al and a number of phosphorus fractions (total P, inorganic P, organic P, apatite P and CDB extractable P) for all samples recovered. A significant inverse correlation was noted between CaCO₃ and most of the other parameters measured whereas no correlations were found for Mn. The sediment adsorption capacity for orthophosphate was found to be about 450 μg P g⁻¹ sediment. Phosphate release from hypolimnetic anaerobic sediments was considered unimportant in the biological sense due to the lack of mobility of this nutrient to the photic zones. Bioavailable P in the littoral zones (assumed to be non-apatite inorganic phosphorus, NAIP) comprised 14.5 tonnes in the uppermost 2 cm sediment layer, which is about 2.5 times the average annual external total P load. Littoral zone sediments, which are normally aerobic, accounted for an internal areal loading of 134 mg P m⁻² yr⁻¹ which is equivalent to 17 and 30% of the average external total P and inorganic P loadings respectively. This internal loading is a major contributory factor in the continuing eutrophic status of the lake.     

Evaluating phenanthrene sorption on various wood chars

A certain amount of wood char or soot in a soil or sediment sample may cause the sorption of organic compounds to deviate significantly from the linear partitioning commonly observed with soil organic matter (SOM). Laboratory produced and field wood chars have been obtained and analyzed for their sorption isotherms of a model solute (phenanthrene) from water solution. The uptake capacities and nonlinear sorption effects with the laboratory wood chars are similar to those with the field wood chars. For phenanthrene aqueous concentrations of 1 microg l(-1), the organic carbon-normalized sorption coefficients (log K(oc)) ranging from 5.0 to 6.4 for field chars and 5.4-7.3 for laboratory wood chars, which is consistent with literature values (5.6-7.1). Data with artificial chars suggest that the variation in sorption potential can be attributed to heating temperature and starting material, and both the quantity and heterogeneity of surface-area impacts the sorption capacity. These results thus help to corroborate and explain the range of logK(oc) values reported in previous research for aquifer materials containing wood chars.     

Removal of As(III) and As(V) from water using a natural Fe and Mn enriched sample

The arsenic removal capacity of a natural oxide sample consisting basically of Mn-minerals (birnessite, cryptomelane, todorokite), and Fe-oxides (goethite, hematite), collected in the Iron Quadrangle mineral province in Minas Gerais, Brazil, has been investigated. As-spiked tap water and an As-rich mining effluent with As-concentrations from 100 μg L⁻¹ to 100 mg L⁻¹ were used for the experiments. Sorbent fractions of different particle sizes (<38 μm to 0.5 mm), including spherical material (diameter 2 mm), have been used. Batch and column experiments (pH values of 3.0, 5.5, and 8.5 for batch, and about pH 7.0 for column) demonstrated the high adsorption capacity of the material, with the sorption of As(III) being higher than that of As(V). At pH 3.0, the maximum uptake for As(V) and for As(III)-treated materials were 8.5 and 14.7 mg g⁻¹, respectively. The Mn-minerals promoted the oxidation of As(III) to As(V), for both sorbed and dissolved As-species. Column experiments with the cFeMn-c sample for an initial As-concentration of 100 μg L⁻¹ demonstrated a very efficient elimination of As(III), since the drinking water limit of 10 μg L⁻¹ was exceeded only after 7400 BV total throughput. The As-release from the loaded samples was below the limit established by the toxicity characteristic leaching procedure, thus making the spent material suitable for discharge in landfill deposits.     

Partitioning of [C]PCB between water and particulates with various organic contents

The use of [¹⁴C]PCB was an effective technique for evaluating the partitioning of PCB between water and particulates. The sorption of [¹⁴C]PCB to clay and/or organic particulates and its subsequent degree of retention on the particles in clean medium was directly related to the particle organic content. Concentration factors (PCB on particles/PCB in water) ranged from 1.1 × 10⁴ for 100% inorganic illite clay to 4.9 × 10⁴ for 100% organic matter.     

Uptake and release of phosphate by a pure culture of Acinetobacter calcoaceticus

Uptake and release of phosphate by a pure culture of Acinetobacter calcoaceticus were investigated under aerobic and anaerobic conditions. The total phosphorus content of this bacterium varied from 0.3 to 1.7 mmol g⁻¹ dry cells or from 0.93 to 5.3% of dry cell weight under various culture conditions. The log-phase cells accumulated polyphosphates of 0.33−0.64 mmol P g⁻¹ dry cells. ³¹P NMR spectra suggested that a portion of polyphosphates was likely bonded to some sort of structural components of the cell. A. calcoaceticus release phosphate linearly with time when transferred from aerobic to anaerobic conditions. The release rate was in the range of 5.9–14.7 × 10⁻³ mmol P g⁻¹ dry cells h⁻¹ and about 4–8% of cellular phosphorus was released during the initial 6 h. During the process of phosphate release acetate was not taken up by this bacterium.     

Sorption of dichlorodiphenyltrichloroethane (DDT) and its metabolites by activated carbon in clean water and sediment slurries

Polyethylene-water partitioning coefficients (K_PE) and mass transfer coefficients (k_PE) for the ortho and para isomers of the organochlorine pesticide dichlorodiphenyltrichloroethane (DDT) and its metabolites dichlorodiphenyldichloroethane (DDD), dichlorodiphenyldichloroethylene (DDE) and, dichlorodiphenylmonochloroethylene (DDMU) were measured. These data were used to derive activated carbon (AC) sorption isotherms in clean water in the sub-nanogram per litre free aqueous concentration range for a virgin and a regenerated AC. The sorption strength of AC for DDT and its metabolites was very high and logarithmic values of the AC-water partitioning coefficients, log K_AC, ranged from 8.47 to 9.26. A numerical mass transfer model was calibrated with this data to interpret previously reported reductions in DDT uptake by semipermeable membrane devices after AC amendment of sediment from Lauritzen Channel, California, USA. The activated carbon-water partitioning coefficient values (K_AC) measured in clean water systems appear to overestimate the AC sorption capacity in sediment up to a factor 32 for DDT and its metabolites at long contact time with fine-sized AC. Modelling results show decreased attenuation of the AC sorption capacity with increased sediment-AC contact time. We infer that increased resistance in mass transfer of DDTs to sorption sites in the microporous region likely caused by deposits of dissolved organic matter in the macro- and mesopores of AC appears to be the most relevant fouling mechanism. These results suggest that DDTs may diffuse through possible deposits of dissolved organic matter over time, implying that the effects of sediment on the sorption of DDTs by AC may be more kinetic than competitive.     

Modified amperometric membrane probes for determining free and total residual chlorine in saline cooling waters

Modifications have been made to a Delta Scientific model 82124 free available chlorine probe so that it can be used to determine either the free or the total residual chlorine in cooling waters at coastal and estuarine power stations. For measurements of free residual chlorine, the internal filling solution of the probe was changed for one containing potassium bromide at pH 4. When the sample solution was dosed with potassium bromide and pH 4 buffer, the probe had a linear response over the range 0.04–1.0 μg ml⁻¹ Cl₂ and errors caused by changes in salinity were negligible. Total standard deviations for the analysis of 1.0 and 0.1 μg ml⁻¹ Cl₂ solutions were 0.055 and 0.01 μg ml⁻¹ Cl₂ respectively. For measurements of total residual chlorine a potassium iodide solution at pH 4 was used as the probe's internal filling solution and the sample solution was dosed with potassium iodide and pH 4 buffer. The probe had a linear response over the range 0.02-0.5 μg ml⁻¹ Cl₂, with total standard deviations of 0.05 and 0.01 μg ml⁻¹ Cl₂ at concentrations of 0.5 and 0.1 μg ml⁻¹ Cl₂ respectively.     

Denitrification rates in relation to stream sediment characteristics

Potential rates of nitrate removal were studied in sediments from three Ontario rivers that differed in texture, organic carbon contents and other characteristics. Intact 0–5 cm depth sediment cores from 22 sites on each river were overlain with aerated 5 mg 1⁻¹ NO₃⁻-N solution and incubated in the laboratory at 21°C for 48 h. Rates of nitrate-N loss from the overlying solutions varied from 37 to 412 mg m⁻² day⁻¹ for a 24 h incubation period. The acetylene blockage technique was used with nitrate amended sediments to evaluate the relative importance of denitrification and nitrate reduction to ammonium. Denitrification accounted for 80–100% of the nitrate loss in the majority of sediment samples tested. Rates of nitrate loss for the 24 h period exhibited a highly significant positive correlation (r = 0.82–0.89) with the water-soluble carbon content of the sediments in each river. Significant relationships were also observed between nitrate loss and organic carbon, total nitrogen and sediment ammonium. A decline in nitrate loss via denitrification and increased nitrate reduction to ammonium was correlated with the organic carbon and water-soluble carbon content of the stream sediments.     

The extent of reversibility of polychlorinated biphenyl adsorption

The extent of reversibility of PCB bonding to sediments has been characterized in studies on the partitioning behavior of a hexachlorobiphenyl isomer. Linear non-singular isotherms have been observed for the adsorption and desorption of 2.4.5.2′,4′,5′ hexachlorobiphenyl (HCBP) to 1100 ppm sediment suspensions. Partition coefficients, π(1 kg−1), for desorption from lake sediments (Saginaw Bay. Lake Huron. Michigan) are substantially greater (π_d 20.000–35.000) than those obtained for adsorption (π₄ 9000–14,000). HCBP was found to be more weakly adsorbed to montmorillonite (π_a − 3000, π_d 9000) and kaolinite (π_a 1000, π_d 3000) clay samples than to the natural sediment samples. Desorption results (π_d) for Saginaw Bay sediments were quite similar to π values (15,000–35.000) calculated from field measurements of aqueous and particulate PCB concentrations. For Saginaw Bay sediments and clay minerals partitioning appeared to be correlated both to sediment surface area and to sediment organic content. A regression analysis using both of these variables explained 90% of the observed variations. HCBP adsorption at 40 C (π_a 14,000) was significantly greater than at 1° C (π_a 6500) resulting in a calculated enthalpy of adsorption of +3.3 kcal mol⁻¹. Non-singular isotherm behavior was not found to be readily attributable to microbiological, kinetic or experimental effects. Evidence from consecutive desorption studies suggests that while HCBP adsorption may ultimately be reversible. release from sediments appeared to involve desorption along two distinct isotherms. These results have been interpreted in terms of possible similarities between the sorption properties observed in the distilled water systems of the present study and PCB bonding processes in natural water systems.     

Transformation of organic matter and bank filtration from a polluted stream

A case study of the examination of the changes of organic matter in a small, highly polluted stream and the adjacent alluvial aquifer is presented. The investigated stream was actually a collector of effluents from baker's yeast and pharmaceutical industries. The stream was characterized by a COD of several thousands of mg O₂ l⁻¹, most of which was biodegradable organic matter. Biodegradation processes took place in the surface water, with consequent oxygen depletion in the stream. The organic matter content of the river sediment was more than 10% of its dry weight. Bank filtration of organic substances was investigated in a number of observation wells at distances of 5–150 m from the river (under different hydrological conditions). The infiltration of organic matter from the polluted stream into the aquifer was found to be significant only at hydrological conditions where the water level exceeds the altitude of the stream bed. The organic matter present in groundwater samples was mainly a humic/fulvic type, and was not degraded during the 64 days of the laboratory biodegradation experiment.     

Anaerobic biological treatment of phenol at 9.5-15 degrees C in an expanded granular sludge bed (EGSB)-based bioreactor

The aims of this study were to demonstrate the (1) feasibility of psychrophilic, or low-temperature, anaerobic digestion (PAD) of phenolic wastewaters at 10–15 °C; (2) economic attractiveness of PAD for the treatment of phenol as measured by daily biogas yields and (3) impact on bioreactor performance of phenol loading rates (PLRs) in excess of those previously documented (1.2 kg phenol m⁻³ d⁻¹). Two expanded granular sludge bed (EGSB)-based bioreactors, R1 and R2, were employed to mineralise a volatile fatty acid-based wastewater. R2 influent wastewater was supplemented with phenol at an initial concentration of 500 mg l⁻¹ (PLR, 1 kg m⁻³ d⁻¹). Reactor performance was measured by chemical oxygen demand (COD) removal efficiency, CH₄ composition of biogas and phenol removal (R2 only). Specific methanogenic activity, biodegradability and toxicity assays were employed to monitor the physiological capacity of reactor biomass samples. The applied PLR was increased to 2 kg m⁻³ d⁻¹ on day 147 and phenol removal by day 415 was 99% efficient, with 4 mg l⁻¹ present in R2 effluent. The operational temperature of R1 (control) and R2 was reduced by stepwise decrements from 15 °C through to a final operating temperature of 9.5 °C. COD removal efficiencies of c. 90% were recorded in both bioreactors at the conclusion of the trial (day 673), when the phenol concentration in R2 effluent was below 30 mg l⁻¹. Daily biogas yields were determined during the final (9.5 °C) operating period, when typical daily R2 CH₄ yields of c. 3.3 l CH₄ g⁻¹ COD_removed d⁻¹ were recorded. The rate of phenol depletion and methanation by R2 biomass by day 673 were 68 mg phenol g VSS⁻¹ d⁻¹ and 12–20 ml CH₄ g VSS⁻¹ d⁻¹, respectively.     

Solubility of polychlorinated biphenyls and capacitor fluid in water

A quantitative method to determine the solubility of polychlorinated biphenyls (PCBs) and used capacitor fluid in water was developed employing high-resolution glass capillary-column gas chromatography. The responses of the electron capture detector to mono-, di-, tri- and tetra-chlorobiphenyls and an internal standard were used to estimate the solubility of the PCBs. Results of the rate of dissolution of Aroclor 1242 and used capacitor fluid in water indicated that a period of five months was required to reach equilibrium. The water-solubile fractions of Aroclor 1242 and used capacitor fluid (Aroclor 1242-impregnated) were found to be identical. Certain isomers of the mono-, di- and poly-biphenyls in Aroclor 1242 were relatively soluble and were identified as 2-mono-, 2,4′-di-, 2,5.2′-tri-, 2.3,2′-tri-, 2,5.4′-tri-, 2,5.2′,5′-tetra-, 2,4.2′,5′-tetra-, 2,4.2′,4′-tetra-, 2,3.2′,5′-tetra- and 2,4.3′,4′-tetra-chlorobiphenyl. In general, the water-soluble fractions of the PCB mixtures were richer in the lower chlorinated isomers than the original PCB mixtures. The solubilities of Aroclor 1016, 1221, 1242, and 1254 were 906. 3516, 703 and 70μg1⁻¹, respectively, whereas the solubility of the used capacitor fluid was the same as that of Aroclor 1242.     

Mode d'action du bioxyde de chlore sur les composes organiques en milieu aqueux Consommations de bioxyde de chlore et reactions sur les composes phenoliquesMode of action of chlorine dioxide on organic compounds in an aqueous medium en|Chlorine dioxide consumption and reactions on phenolic compounds

The aim of our work was to study the reaction between chlorine dioxide (ClO₂) and organic substances. In the first part of our survey, chlorine dioxide demands were measured in diluted aqueous solutions of various kinds of organic compounds (5 × 10⁻⁵ −10 M) at pH 7. In the second part, the study of the action of chlorine dioxide on phenols (phenol, di and triphenols) was undertaken by observing the change of the organic substance through global parameter controls (COT, u.v. spectrum) and by trying to identify a certain number of oxidation products by means of chromatographic analysis (HPLC and GC), of mass spectrometry and of Nuclear Magnetic Resonance spectrometry (NMR).     

Partitioning of selected polychlorinated biphenyls to natural sediments

The partitioning of two polychlorinated biphenyl mixtures (Aroclor 1016 and 1242) and two tetrachlorobiphenyl isomers (2,5,3′,4′ and 2,6,2′,6′ tetrachlorobiphenyl) between water and four natural sediments was evaluated in laboratory investigations. For both Aroclor mixtures, the extent of adsorption was comparable on all four natural sediments studied. For individual isomers, partitioning was comparable with that observed for the mixtures. Both particle size distribution and total organic carbon were important factors in determining the extent of partitioning for the two isomers; but in the case of the mixtures, there was no correlation with organic content.     

Sorption and accumulation of cadmium in the sediment of the Tama River

Cadmium contents in the water and the sediment samples collected from the Tama River and several branches were measured. Cadmium (above 0.005mgl⁻¹) was detected in only four of the water samples, while the sediment samples showed cadmium content of 1.0–9.8 μg g⁻¹ dry sediment. Cadmium concentration in the sediments of the main stream was correlated against ignition loss of the samples and it was found that 1 g of ignition loss (organic matter) corresponded to 35 μg of cadmium.The batch adsorption experiment in the laboratory using an aqueous solution of cadmium for 14 sediment samples with a higher concentration of cadmium indicated that the amount adsorbed by the sediment is highly dependent on the ignition loss. The amount adsorbed on unit mass of ignition loss q_IL could be correlated by a Freundlich-type equilibrium relation as where C is the equilibrium concentration in the aqueous phase ranging between 7 × 10⁻³ and 10 mg l⁻¹, while k_IL and n are equilibrium constants.The adsorption rate measurement showed that the intraparticle diffusion coefficient of cadmium in the sediment was about 1.1 × 10⁻⁶ cm²s⁻¹, which is of a reasonable order of magnitude assuming the pore diffusion mechanism inside the particle.The results suggest that suspended solid particles of high organic content in flowing water contribute significantly to the transport of cadmium along the river.     

Influence of ionic surfactants on the flocculation and sorption of palladium and mercury in the aquatic environment

The influence of sub-micellar concentrations of an anionic surfactant (sodium dodecyl sulphate; SDS) and a cationic surfactant (hexadecyl trimethylammonium bromide; HDTMA) on the aquatic behaviour of the strongly complexing metals, Pd(II) and Hg(II), has been investigated. In river water, flocculation of organic complexes of metal was suppressed by SDS but accentuated by HDTMA, effects that are consistent with electrostatic and hydrophobic interactions between ionic surfactants and natural polyelectrolytes. In sea water, flocculation of metal complexes was enhanced by both surfactants because of the shielding and salting effects of inorganic ions on these interactions. Particle surface modification engendered by sorbed surfactant strongly influenced the sorption of Pd and Hg to estuarine particles. Thus, hydrophobically bound SDS enhances the negative charge at the particle surface and favours specific sorption of metal, while specifically sorbed HDTMA enhances the solvency of the particle surface, favouring non-specific sorption of metal complexes. Given the relatively short environmental half-life of SDS, its impacts on strongly complexing metals are predicted to be localised. However, greater stability of HDTMA suggests that its effects on such metals, including enhanced flocculation and sorption, are likely to be more pervasive.