Kinetics of heavy metal vaporization from model wastes in a fluidized bed

Metal vaporization experiments were carried out in an atmospheric fluidized bed to study the influence of operating conditions on the extent of heavy metal (HM) release in fumes from municipal solid waste incinerators. Modelwastes spiked with compounds of Pb, Cd, and Zn were used. The parameters studied were temperature, treatment duration, matrix of the model waste (mineral and organic), HM initial speciation, and gas composition (N2, air, air + HCl, gas mixture simulating the incinerators). The extent of vaporization was measured by solid sample analysis and on-line analysis of the gaseous effluent, after customization of the ICP technique for gas analysis. The results indicate the metal vaporization rate is very high initially and then slows. The results with mineral matrices give the decreasing order of volatility Cd > Pb > Zn, but in industrial incinerators Zn volatilizes slightly more than Pb. Temperature (especially for porous alumina) and mineral matrix have a strong influence on the HM vaporization, but HCl concentration and HM initial speciation do not. The gas composition and the initial metal concentration are significant parameters. The matrix influence clearly denoted the mass transfer limitations in the vaporization process from mineral matrix.     

Resuspension of soil as a source of airborne lead near industrial facilities and highways

Geologic materials are an important source of airborne particulate matter less than 10 microm aerodynamic diameter (PM10), but the contribution of contaminated soil to concentrations of Pb and other trace elements in air has not been documented. To examine the potential significance of this mechanism, surface soil samples with a range of bulk soil Pb concentrations were obtained near five industrial facilities and along roadsides and were resuspended in a specially designed laboratory chamber. The concentration of Pb and other trace elements was measured in the bulk soil, in soil size fractions, and in PM10 generated during resuspension of soils and fractions. Average yields of PM10 from dry soils ranged from 0.169 to 0.869 mg of PM10/g of soil. Yields declined approximately linearly with increasing geometric mean particle size of the bulk soil. The resulting PM10 had average Pb concentrations as high as 2283 mg/kg for samples from a secondary Pb smelter. Pb was enriched in PM10 by 5.36-88.7 times as compared with uncontaminated California soils. Total production of PM10 bound Pb from the soil samples varied between 0.012 and 1.2 mg of Pb/kg of bulk soil. During a relatively large erosion event, a contaminated site might contribute approximately 300 ng/m3 of PM10-bound Pb to air. Contribution of soil from contaminated sites to airborne element balances thus deserves consideration when constructing receptor models for source apportionment or attempting to control airborne Pb emissions.     

PBCDD and PBCDF from incineration of waste-containing brominated flame retardants

Brominated organic flame retardants comprise a large, heterogeneous group of compounds that are useful but also potentially damaging to the environment. In this investigation, three common brominated flame retardants were co-combusted with an artificial municipal solid waste in a pilot-scale fluidized bed incinerator. Combustion conditions ensured degradation of the flame retardants, but stable brominated organic compounds such as polybrominated dibenzo-p-dioxins and polybrominated dibenzofurans were formed in the cooling flue gases. The incineration of fuels that contain both chlorine and bromine leads to the formation of a complex mixture of polybrominated/chlorinated dibenzo-p-dioxins and dibenzofurans. More bromination than chlorination was observed in these experiments, and the chlorination levels increased when bromine was added to the fuel. The most favored reactions led to the formation of dibromodichlorodibenzo-p-dioxin and dibromodichlorodibenzofuran. Theoretical calculations show that there is more Br2 than Cl2 in the flue gas when the two halogens are present at equimolar levels, because chlorine is mainly found in the form of HCl. This may explain the higher bromination level. BrCl is also present, which drives the chlorination observed when bromine is added.     

Brominated flame retardants in archived serum samples from Norway: a study on temporal trends and the role of age

The temporal trends and influence of age and gender on levels of selected brominated flame retardants (BFRs) in human serum have been assessed by analyzing archived samples from Norway. Serum from 40 to 50 year old men collected at six time periods during 1977 to 1999 and from eight groups of differing age and gender sampled in 1998 were pooled into six and eight samples, respectively. The BFRs were isolated using solid-phase extraction (SPE) and the serum lipids decomposed bytreatmentwith concentrated sulfuric acid directly on the polystyrene-divinylbenzene SPE column, prior to elution of the BFRs. Following diazomethane derivatization, the samples were analyzed by gas chromatography-electron capture mass spectrometry. Eight BFRs were quantified in the serum samples: 2,4,4'-tribromodiphenyl ether (BDE-28), 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), 2,2',4,4',5-pentabromodiphenyl ether (BDE-99), 2,2',4,4',6-pentabromodiphenyl ether (BDE-100), 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153), 2,2',4,4',5,6'-hexabromodiphenyl ether (BDE-154), 2,4,6-tribromophenol (TriBP), and tetrabromobisphenol A (TBBP-A). The serum concentrations of all the BFRs, increased during the entire period with the exception of TriBP, and the sum of the six polybrominated diphenyl ethers increased from 0.44 ng/g lipids in 1977 to 3.3 ng/g lipids in 1999. The BFR concentrations in the serum from the different age groups were relatively similar, except for the age group 0-4 years, which had 1.6-3.5 times higher serum concentrations. Women older than 25 years had lower serum concentrations of BFRs compared to the corresponding group of men. No trend related to age or gender, nor time during the period 1977 to 1999 was observed for TriBP. The present study indicates an ongoing increase in human exposure to BFRs, and the current body burden appears to be independent of age, except for infants (0-4 years old), who seem to experience elevated exposure.     

Calibrating the uptake kinetics of semipermeable membrane devices in water: impact of hydrodynamics

The use of lipid-containing semipermeable membrane devices (SPMDs) is becoming commonplace, but the potential effects of environmental variables affecting the accumulation of contaminants into SPMDs had not been characterized sufficiently, yet. To characterize the effect of hydrodynamic conditions on the contaminant uptake kinetics, accumulation of pentachlorobenzene, hexachlorobenzene, and hexachlorocyclohexane isomers from water into SPMD was studied at various water flow rates. The accumulation kinetics of hydrophobic compounds (log Kow > 4) are governed by the aqueous boundary layer in linear flow velocity range from 0.06 to 0.28 cm s(-1) and sensitive to slight changes in flow rate. The effect of flow velocity on the exchange kinetics increases with increasing hydrophobicity. Under faster, but still laminar flow conditions (0.28-1.14 cm s(-1)), the sensitivity to changes in flow decreases to a nonsignificant level for the substances under consideration. The results of this study confirm that the use of the laboratory-derived calibration data for estimation of analyte concentrations in the ambient environment is limited unless flow-sensitive performance reference compounds are used.     

Specific UV absorbance of Aldrich humic acid: changes during transport in aquifer sediment

This study examined the transport behavior of Aldrich humic acid (AHA) in low natural organic carbon content sediment contaminated with tetrachloroethene (PCE), for comparison to a nonionic surfactant mixture previously examined in the same system. Tracking of individual molecular weight (MW) fractions of AHA was attempted by UV absorbance, followed by conversion to mass of carbon using specific ultraviolet absorbance (SUVA) (UV absorbance per mass of carbon) measurements. The analysis required determination of variations of SUVA with MW, which showed a maximum at 10 000 Daltons. Furthermore, SUVAs of AHA MW fractions greater than about 10 000 Daltons increased following AHA interaction with sediment in batch experiments, and this was associated with AHA-driven leaching of cations from the sediment. AHA transport was examined in a series of three columns representing the up-gradient, residual-zone, and down-gradient portions of a DNAPL contaminated site. SUVAs of larger MW AHA fractions cycled through decreased, increased, and eventual return to influent values during the early, intermediate, and final stages of breakthrough, respectively. These variations were attributable to a combination of preferential adsorption of low MW fractions of the AHA during early breakthrough and AHA-driven leaching of sediment cations during intermediate breakthrough, with eventual exhaustion of sediment cation complexation during the final stage of breakthrough. The complex variations in SUVA precluded accurate conversion of measured UV absorbance to carbon mass. However, the effect of AHA loss to sediment on the solubilizing capacity of the AHA solution was indicated by the breakthrough behavior of AHA-solubilized PCE, which showed that AHA loss from the aqueous phase during transport in this system did not decrease the solubilizing capacity of the AHA mixture.     

Adsorption of Pb(ll) and Eu(III) by oxide minerals in the presence of natural and synthetic hydroxamate siderophores

Trihydroxamate siderophores have been proposed for use as mediators of actinide and heavy metal mobility in contaminated subsurface zones. These microbially produced ligands, common in terrestrial and marine environments, recently have been derivatized synthetically to enhance their affinity for transuranic metal cations. However, the interactions between these synthetic derivative and adsorbed trace metals have not been characterized. In this paper we compare a natural siderophore, desferrioxamine-B (DFO-B), with its actinide-specific catecholate derivative, N-(2,3-dihydroxy-4-(methylamido)benzoyl)desferrioxamine-B (DFOMTA), as to their effect on the adsorption of Pb(II) and Eu(III) by goethite and boehmite. In the presence of 240 microM DFO-B, a strongly depleting effect on Eu(III) adsorption by goethite and boehmite occurred above pH 6. By contrast, almost total removal of Eu(III) from solution in the neutral to slightly acidic pH range was observed in the presence of either 10 or 100 microM DFOMTA, due primarilyto the formation of metal-DFOMTA precipitates. Addition of DFOMTA caused an increase in Pb(II) adsorption by goethite below pH 5, but a decrease above pH 5, such that the Pb(II) adsorption edge in the presence of DFOMTA strongly resembled the DFOMTA adsorption envelope, which showed a maximum near pH 5 and decreasing adsorption toward lower and higher pH.     

Effects of coxsackievirus B3 infection on the acute-phase protein metallothionein and on cytochrome P-4501A1 involved in the detoxification processes of TCDD in the mouse

During acute infections, the synthesis of acute-phase proteins and other proteins participating in the host defence are stimulated in the liver and kidney. In previous studies of coxsackievirus B3 (CB3) infection in mice, we found that cadmium (Cd) accumulates in the kidney, whereas 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) accumulates in the liver. To study if CB3 infection affects the synthesis of the Cd-binding protein metallothionein (MT) and the TCDD-binding/detoxifying cytochrome P-450 (CYP-450) isozyme CYP1A1, the basal and TCDD-induced levels of serum MT and liver CYP1A1 isozyme were determined in healthy and CB3-infected A/J mice. Furthermore, because interferons affect CYP450 activity, the serum levels of the interferons alpha (IFN-alpha) and -beta (IFN-beta) were measured in CB3-infected mice and in mice treated with the interferon-inducer polyinosinic/polycytidylic acid (poly I/C). Virus or poly I/C was administered intraperitoneally (i.p.) on day 0 and 500 ng TCDD/kg bodyweight on day 1. On day 4, CB3 infection had induced MT approximately 10-fold, regardless of TCDD treatment (P < 0.01 in infected mice and P < 0.001 in infected, TCDD-treated mice). TCDD alone induced a 10-fold increase in CYP1A1 activity (P < 0.001), whereas infection alone suppressed the normal CYP1A1 activity by 75% (P < 0.001). Infection also suppressed the TCDD-induced CYP1A1 activity by approximately 30% (n.s.). Poly I/C suppressed CYP1A1 by 20-25% (n.s.) at both basal and TCDD-induced levels. Serum IFN-alpha and IFN-beta levels were undetectable in controls, in TCDD-treated and in the poly I/C-treated groups on day 4, probably because the short IFN peak is detectable only hours after injection. Conversely, on day 4 of the infection, IFN-alpha and IFN-beta were consistently raised in the TCDD-treated infected mice, whereas increased IFNs as a result of infection alone could be detected in only one individual. These results suggest that the normal host responses during acute infections down-regulate detoxifying processes in favour of acute-phase protein synthesis. This may explain the observed changed pattern of accumulation, excretion and toxicity of the environmental pollutants cadmium and TCDD during this common virus infection.     

Prediction of the effects of soil-based countermeasures on soil solution chemistry of soils contaminated with radiocesium using the hydrogeochemical code PHREEQC

For agriculturally used areas, which are contaminated by the debris from a nuclear accident, the use of chemical amendmends (e.g. potassium chloride and lime) is among the most common soil-based countermeasures. These countermeasures are intended to reduce the plant uptake of radionuclides (mainly 137Cs and 90Sr) by competitive inhibition by chemically similar ions. So far, the impacts of countermeasures on soil solution composition - and thus, their effectiveness - have almost exclusively been established experimentally, since they depend on mineral composition and chemical characteristics of the soil affected. In this study, which focuses on caesium contamination, the well-established code PHREEQC was used as a geochemical model to calculate the changes in the ionic compositions of soil solutions, which result from the application of potassium or ammonium in batch equilibrium experiments. The simple ion exchange model used by PHREEQC was improved by taking into account selective sorption of Cs+, NH4+ and K+ by clay minerals. Calculations were performed with three different initial soil solution compositions, corresponding to particular soil types (loam, sand, peat). For loamy and sandy soils, our calculational results agree well with experimental data reported by Nisbet (Effectiveness of soil-based countermeasures six months and one year after contamination of five diverse soil types with caesium-134 and strontium-90. Contract Report NRPB-M546, National Radiation Protection Board, Chilton, 1995.). For peat, discrepancies were found indicating that for organic soils a reliable set of exchange constants of the relevant cations still has to be determined experimentally. For cesium, however, these discrepancies almost disappeared if selective sites were assumed to be inaccessible. Additionally, results of sensitivity analyses are presented by which the influence of the main soil parameters on Cs+ concentrations in solution after soil treatment has been systematically studied. It is shown that calculating the impacts of soil-based chemical countermeasures on soil solution chemistry using geochemical codes such as PHREEQC offers an attractive alternative to establishing these impacts by often time-consuming and site-specific experiments.