Search

Available literature data on the aqueous chemistry of radium are compiled. There are limited available experimental data and a significant portion of the data has been estimated using electrostatic techniques, typically based on the corresponding data of barium. The available data are compared with the corresponding data of barium (and strontium) and a methodology for estimating additional radium thermochemical data is described.

The AKUFVE techniques were developed by Rydberg and co-workers in the 1960s. The main aim was to be able to perform a series of liquid-liquid extraction data varying one or more parameters ...

The hydrolysis of Ba2+and Ra2+was studied at 25 °C in aqueous mixtures of NaOH and NaClO4using an ion exchange method and radiotracer and batch techniques. The distribution of133Ba and226Ra between solid (ion exchange resin) and aqueous (mixture of NaOH and NaClO4) phases was measured via gamma spectrometry and liquid scintillation counting. The total ionic strength was kept constant and the concentration of NaOH in the aqueous phase was varied from 0 (pure NaClO4) to pure NaOH from sample to sample. It was shown that an increase of the Ba2+or Ra2+concentration in the aqueous phase with an increase of the NaOH concentration cannot be explained solely by Ba2+or Ra2+activity coefficient differences in the NaOH and NaClO4media (salting out) and that weak BaOH+and RaOH+ion pairing occurs in the systems studied. A model for weak ion association was developed and apparent BaOH+and RaOH+stability constants were derived assuming the formation of weak aqueous NaOH(aq) ion pairs via non-linear curve fitting. It was demonstrated that systematic uncertainties have a much greater contribution to the NaOH(aq), BaOH+and RaOH+stability constant uncertainty budget compared to stochastic uncertainties and a method for estimation of the systematic uncertainties was proposed. The method combines fitting, restricted primitive model computations with surveyed literature data that resulted in a stability constant for NaOH(aq) that ranged from 0 to 1 at ionic strengths below 5 mol·kg−1(i.e. KNaOH= 0.5 ± 0.5, where the uncertainty is a systematic 95% confidence interval). The variation of KNaOHallowed the estimation of the systematic 95% confidence interval in the apparent stability constants of BaOH+and RaOH+. The specific ion interaction theory was used to extrapolate the derived logarithms of the BaOH+and RaOH+apparent stability constants to zero ionic strength (log10K = 0.7 ± 0.2 for both ion pairs) and obtain the relevant ion interaction parameters. It was shown that both the Ba2+and Ra2+ions have similar activity coefficients and undergo similar short-range interactions in aqueous NaOH-NaClO4media.

The speciation of Ra 2+ and Ba 2+ with EDTA was investigated at 25 °C in aqueous alkaline NaCl media as a function of ionic strength (0.2–2.5 mol·L −1 ) in two pH regions where the EDTA 4− and HEDTA 3− species dominate. The stability constants for the formation of the [BaEDTA] 2− and [RaEDTA] 2− complexes were determined using an ion exchange method. Barium-133 and radium-226 were used as radiotracers and their concentrations in the aqueous phase were measured using liquid scintillation counting and gamma spectrometry, respectively. The specific ion interaction theory (SIT) was used to account for [NaEDTA] 3− and [NaHEDTA] 2− complex formation, and used to extrapolate the logarithms of the apparent stability constants (log 10 K) to zero ionic strength (BaEDTA 2− : 9.86 ± 0.09; RaEDTA 2− : 9.13 ± 0.07) and obtain the Ba 2+ and Ra 2+ ion interaction parameters: [e(Na + , BaEDTA 2− ) = − (0.03 ± 0.11); e(Na + , RaEDTA 2− ) = − (0.10 ± 0.11)]. It was found that in the pH region where HEDTA 3− dominates, the reaction of Ba 2+ or Ra 2+ with the HEDTA 3− ligand also results in the formation of the BaEDTA 2− and RaEDTA 2− complexes (as it does in the region where the EDTA 4− ligand dominates) with the release of a proton. Comparison of the ion interaction parameters of Ba 2+ and Ra 2+ strongly indicates that both metal ions and their EDTA complexes have similar activity coefficients and undergo similar short-range interactions in aqueous NaCl media.

The numerical modeling of ZnII speciation amongst the environmental inorganic ligands Cl–, OH–, CO3 2–, SO4 2–, and PO4 3– requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10 β p,q,r ° valid at I m = 0 mol·kg–1 and 25 °C (298.15 K), and reports the empirical reaction ion interaction coefficients, ∆ε, required to calculate log10 β p,q,r values at higher ionic strengths using the Brønsted–Guggenheim–Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ∆r H, are reported where available. There is scope for additional high-quality measurements for the Zn2+ + H+ + CO3 2– system and for the Zn2+ + OH– and Zn2+ + SO4 2– systems at I > 0. In acidic and weakly alkaline fresh water systems (pH < 8), in the absence of organic ligands (e.g., humic substances), ZnII speciation is dominated by Zn2+(aq). In this respect, ZnII contrasts with CuII and PbII (the subjects of earlier reviews in this series) for which carbonato- and hydroxido- complex formation become important at pH > 7. The speciation of ZnII is dominated by ZnCO3(aq) only at pH > 8.4. In seawater systems, the speciation at pH = 8.2 is dominated by Zn2+(aq) with ZnCl+, Zn(Cl)2(aq), ZnCO3(aq), and ZnSO4(aq) as minor species. This behaviour contrasts with that for CuII and PbII for which at the pH of seawater in equilibrium with the atmosphere at 25 °C (log10 {[H+]/c°} ≈ 8.2) the MCO3(aq) complex dominates over the MCl n (2–n)+ species. The lower stability of the different complexes of ZnII compared with those of CuII, PbII, and CdII is also illustrated by the percentage of uncomplexed M2+ in seawater, which is ca. 55, 3, 2, and 3.3 % of [MII]T, respectively.

This article describes a 10-year cooperative effort between the U.S. National Institute of Standards and Technology (NIST) and five major journals in the field of thermophysical and thermochemical properties to improve the quality of published reports of experimental data. The journals are Journal of Chemical and Engineering Data, The Journal of Chemical Thermodynamics, Fluid Phase Equilibria, Thermochimica Acta, and International Journal of Thermophysics. The history of this unique cooperation is outlined, together with an overview of software tools and procedures that have been developed and implemented to aid authors, editors, and reviewers at all stages of the publication process, including experiment

Thermodynamic sorption models (TSMs) offer the potential to improve the incorporation of sorption in environmental modelling of contaminant migration. One specific application is safety cases for radioactive waste repositories, in which radionuclide sorption on mineral surfaces is usually described using distribution coefficients (K"d values). TSMs can be utilised to provide a scientific basis for the range of K"d values included in the repository safety case, and for assessing the response of K"d to changes in chemical conditions. The development of a TSM involves a series of decisions on model features such as numbers and types of surface sites, sorption reactions and electrostatic correction factors. There has been a lack of consensus on the best ways to develop such models, and on the methods of determination of associated parameter values. The present paper therefore presents recommendations on a number of aspects of model development, which are applicable both to radioactive waste disposal and broader environmental applications. The TSM should be calibrated using a comprehensive sorption data set for the contaminant of interest, showing the impact of major geochemical parameters including pH, ionic strength, contaminant concentration, the effect of ligands, and major competing ions. Complex natural materials should be thoroughly characterised in terms of mineralogy, surface area, cation exchange capacity, and presence of impurities. During the application of numerical optimisation programs to simulate sorption data, it is often preferable that the TSM should be fitted to the experimentally determined K"d parameter, rather than to the frequently used percentage sorbed. Two different modelling approaches, the component additivity and generalised composite, can be used for modelling sorption data for complex materials such as soils. Both approaches may be coupled to the same critically reviewed aqueous thermodynamic data sets, and may incorporate the same, or similar, surface reactions and surface species. The quality of the final sorption model can be assessed against the following characteristics: an appropriate level of complexity, documented and traceable decisions, internal consistency, limitations on the number of adjustable parameter values, an adequate fit to a comprehensive calibration data set, and capability of simulating independent data sets. Key recommendations for the process of TSM development include: definition of modelling objectives, identification of major decision points, a clear decision-making rationale with reference to experimental or theoretical evidence, utilisation of a suitable consultative and iterative model development process, testing to the maximum practicable extent, and thorough documentation of key decisions. These recommendations are consistent with international benchmarks for environmental modelling.

ThermoML is an XML-based approach for storage and exchange of experimental, predicted, and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the representation of speciation, complex equilibria, and properties of biomaterials are described. The texts of 14 data files illustrating the new extensions are provided as Supplementary Information together with the complete text of the updated ThermoML schema.

The numerical modeling of CdII speciation amongst the environmental inorganic ligands Cl–, OH–, CO3 2–, SO4 2–, and PO4 3– requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10 β p,q,r ° valid at I m = 0 mol kg–1 and 25 °C (298.15 K), along with the equations and empirical reaction ion interaction coefficients, ∆ε , required to calculate log10 β p,q,r values at higher ionic strengths using the Brønsted–Guggenheim–Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ∆r H, are reported where available. Unfortunately, with the exception of the CdII-chlorido system and (at low ionic strengths) the CdII-sulfato system, the equilibrium reactions for the title systems are relatively poorly characterized. In weakly acidic fresh water systems (–log10 {[H+]/c°} < 6), in the absence of organic ligands (e.g., humic substances), CdII speciation is dominated by Cd2+(aq), with CdSO4(aq) as a minor species. In this respect, CdII is similar to CuII [2007PBa] and PbII [2009PBa]. However, in weakly alkaline fresh water solutions, 7.5 < –log10 {[H+]/c°} < 8.6, the speciation of CdII is still dominated by Cd2+(aq), whereas for CuII [2007PBa] and PbII [2009PBa] the carbonato- species MCO3(aq) dominates. In weakly acidic saline systems (–log10 {[H+]/cϒ} < 6; –log10 {[Cl–]/c°} < 2.0) the speciation is dominated by CdCl n (2– n )+ complexes, (n = 1–3), with Cd2+(aq) as a minor species. This is qualitatively similar to the situation for CuII and PbII. However, in weakly alkaline saline solutions, including seawater, the chlorido- complexes still dominate the speciation of CdII because of the relatively low stability of CdCO3(aq). In contrast, the speciation of CuII [2007PBa] and PbII [2009PBa] in seawater is dominated by the respective species MCO3(aq). There is scope for additional high-quality measurements in the Cd2+ + H+ + CO3 2– system as the large uncertainties in the stability constants for the Cd2+-carbonato complexes significantly affect the speciation calculations.

Complex formation between CuII and the common environmental ligands Cl-, OH-, CO3 2-, SO4 2-, and PO4 3- can have a significant effect on CuII speciation in natural waters with low concentrations of organic matter. Copper(II) complexes are labile, so the CuII distribution amongst these inorganic ligands can be estimated by numerical modeling if reliable values for the relevant stability (formation) constants are available. This paper provides a critical review of such constants and related thermodynamic data. It recommends values of log10β p,q,r ° valid at I m = 0 mol kg-1 and 25 °C (298.15 K), along with the equations and specific ion interaction coefficients required to calculate log10β p,q,r values at higher ionic strengths. Some values for reaction enthalpies, ΔrHm, are also reported where available. In weakly acidic fresh water systems, in the absence of organic ligands, CuII speciation is dominated by the species Cu2+(aq), with CuSO4(aq) as a minor species. In seawater, it is dominated by CuCO3(aq), with Cu(OH)+, Cu2+(aq), CuCl+, Cu(CO3)OH-, Cu(OH)2(aq), and Cu(CO3)2 2- as minor species. In weakly acidic saline systems, it is dominated by Cu2+(aq) and CuCl+, with CuSO4(aq) and CuCl2(aq) as minor species.

The mobility and bioavailability of metal ions in natural waters depend on their chemical speciation, which involves a distribution of the metal ions between different complex (metal-ligand) species, colloid-adsorbed species and insoluble phases, each of which may be kinetically labile or inert. For example, in fresh water the metal ions are distributed among organic complexes (e.g., humates), colloids (e.g., as surface-adsorbed species on colloidal phases such as FeOOH), solid phases (e.g., hydroxide, oxide, carbonate mineral phases), and labile complexes with the simple inorganic anionic ligands commonly present in natural waters (e.g., for Zn

This document presents a critical evaluation of the equilibrium constants and reaction enthalpies for the complex formation reactions between aqueous Hg(II) and the common environmental inorganic ligands Cl–, OH–, CO3 2–, SO4 2–, and PO4 3–. The analysis used data from the IUPAC Stability Constants database, SC-Database, focusing particularly on values for 25 °C and perchlorate media. Specific ion interaction theory (SIT) was applied to reliable data available for the ionic strength range Ic < 3.0 mol dm–3. Recommended values of log10 βp,q,r ° and the associated reaction enthalpies, ∆r H m°, valid at Im = 0 mol kg–1 and 25 °C, were obtained by weighted linear regression using the SIT equations. Also reported are the equations and specific ion interaction coefficients required to calculate log10 βp,q,r ° values at higher ionic strengths and other temperatures. A similar analysis is reported for the reactions of H+ with CO3 2– and PO4 3–. Diagrams are presented to show the calculated distribution of Hg(II) amongst these inorganic ligands in model natural waters. Under typical environmental conditions, Hg(II) speciation is dominated by the formation of HgCl2(aq), Hg(OH)Cl(aq), and Hg(OH)2(aq).

The stability constants of zirconium(IV) hydrolysis species have been measured at 15, 25, and 35 °C [in 1.0 mol-dm−3 (H,Na)ClO4] using both potentiometry and solvent extraction. In addition, the solubility of [Zr(OH)4(am)] has been investigated in a 1 mol-dm−3 (Na,H)(ClO4,OH) medium at 25 °C over a wide range of −log [H+] (0-15). The results indicate the presence of the monomeric species Zr(OH)3+, Zr(OH)2 2+, Zr(OH)3 +, and Zr(OH)4 0(aq) as well as the polymeric species Zr4(OH)8 8+ and Zr2(OH)6 2+. The solvent extraction measurements required the use of acetylacetone. As such, the stability constants of zirconium(IV) with acetylacetone were also measured using solvent extraction. All stability constants were found to be linear functions of the reciprocal of temperature (in kelvin) indicating that Δ H o and Δ S o are both independent of temperature (over the temperature range examined in the study). The results of the solubility experiments have shown four distinctly different solubility regions. In strongly acidic solutions, the solubility is controlled by the formation of polynuclear hydrolysis species in solution whereas in less acidic solution the formation of mononuclear hydrolysis species becomes dominant. The largest portion of the solubility curve is controlled by equilibrium with aqueous Zr(OH)4 0(aq) where the solubility is independent of the proton concentration. In alkaline solutions, the solubility increases due to formation of the zirconate ion. The middle region was used to determine the solubility constant (log *K s10) of Zr(OH)4(s). From the data in the alkaline region, a value of the stability of the zirconate ion has been determined. This is the first time that the possible evidence for the zirconate ion has been identified in aqueous solution that has previously been found only in the solid phase.

Whole soft tissue concentrations of Mn, Co, Ni, Cu, Zn, Pb, Cd and U were measured in two species of freshwater (unionid) bivalves (Hyridella depressa and Velesunio ambiguus) from a minimally polluted site in the Hawkesbury-Nepean River, south-eastern Australia. Although the mean concentrations of metals in the tissue were similar for each bivalve species, their patterns of accumulation were dissimilar. For each metal, positive linear relationships between tissue concentration and shell length (r2 = 0.37-0.77; P < or = 0.001) and tissue dry weight (r2 = 0.29-0.51; P < or = 0.01) were found in H. depressa, but not in V. ambiguus. However, for both species, positive linear relationships were found between the tissue concentration of each divalent metal and Ca tissue concentration (r2 = 0.59-0.97; P < or = 0.001). For both bivalve species, the normalised rates of accumulation of the metals relative to increasing Ca concentration and/or size, were U approximately = Cd > or = Pb > or = Mn > Co > or = Zn > Cu > Ni. The differential rates of accumulation of divalent metals are interpreted as being predominantly governed by their varying loss rates, which are controlled by the differing solubilities (log Ksp values) of the metals in the phosphatic extracellular granules, the demonstrated major sites of metal deposition in the tissue of H. depressa and V. ambiguus. The rates of accumulation of Mn, Co, Zn, Cu and Ni were linearly and inversely related (r2 = 0.91-0.97; P < or = 0.001) to their solubilities as hydrogen phosphates, a finding consistent with the bioaccumulation model previously developed for the alkaline-earth metals. However, for U, Cd and Pb, this linear inverse relationship did not continue to hold, i.e. their rates of accumulation did not increase with decreasing solubility. However, these results are still consistent with the model if U, Cd and Pb are so insoluble in the granules of H. depressa and V. ambiguus over their lifetime (up to approx. 50 years) that there is effectively no loss of these metals, and hence, no differential between their rates of accumulation. The present results reaffirm the use of Ca tissue concentration to predict the tissue concentrations of other divalent metals by explaining up to 94 and 97% of the variability between individual bivalves of H. depressa and V. ambiguus, respectively. The use of Ca tissue concentration to effectively minimise the inherent variability between individuals in their metal tissue improves the ability of an investigator to discern smaller spatial and/or temporal differences in the metal tissue concentrations of these bivalves, and thus to detect metal pollution.

The veracity of the free ion activity model (FIAM) was tested by examining the acute (48 h) valve movement responses (VMR) (measured in terms of the duration of valve opening) of the Australian tropical freshwater unionid bivalve, Velesunio angasi to increasing concentrations of total Mn or U, in a standard synthetic water under conditions of varying pH (5.0-6.0) and/or dissolved organic carbon (model fulvic acid, FA) concentrations (0-8.9 mg l(-1)). Valve movement behaviour, measured using an automated data acquisition system, was shown to be a quantifiable and rapid, real-time endpoint for assessing the toxic effects of Mn and U exposures. For Mn, the VMR of V. angasi were independent (P>0.05) of pH and/or model FA concentration. In contrast, VMR to U exposures were highly dependent (P< or =0.05) on pH and/or model FA concentration; individuals were more sensitive to U at low pH and model FA concentrations. Valve movement responses to Mn were directly proportional to the activity of the free metal ion (Mn(2+)), which is consistent with the FIAM. In contrast, VMR to U were regarded as an 'exception' to the FIAM, since they were a weighted function of the activities of the free metal ion and the 1:1 metal hydroxide species (i.e. 1.86 x UO2(2+) + UO2OH(+)). Additionally, the effect of U on V. angasi demonstrates the importance of examining VMR at more than one pH. At a fixed pH, the results for U were consistent with the FIAM (i.e. response was directly proportional to UO2(2+)); only when pH was altered, were the results inconsistent with the FIAM. The inconsistency in the VMR of V. angasi to U exposures in this study, together with similar examples from other studies using different metals (e.g. Al or Zn), raises questions regarding the veracity of the FIAM. A detailed examination of the conceptual development of the FIAM is required to probe its apparent failure to describe several metal-organism interactions.

The stability constants of thorium(IV) hydrolysis species have been measured at15, 25, and 35°C (in 1.0 mol dm−3 NaClO4) using both potentiometry and solventextraction. The results indicate the presence of the monomeric speciesTh(OH)3+, Th(OH)2+2, Th(OH)+3, and Th(OH)4, in addition to the polymericspecies Th4(OH)8+8 and Th6(OH)9+15. The polymeric species were found to beimportant, although the total thorium concentration was limited to 0.01–0.1mmol-dm−3. The solvent extraction measurements required the use of acetylacetone.As such, the stability constants of thorium(IV) with acetylacetone were alsomeasured using both potentiometry and solvent extraction. All logarithms of thestability constants were found to be linear functions of the reciprocal absolutetemperature indicating that ΔHo and ΔSo of reaction are both independent oftemperature (over the temperature range examined in the study).

Hydrogeochemical modelling (utilising the modelling tools MODFLOW, MT3D and HARPHRQ) has been used in conjunction with laboratory-based experiments and a field monitoring program to investigate the fate of uranium and other contaminants in excess water sprayed on a 33 ha region of the Ranger Uranium Mine (RUM), northern Australia. The results indicate that uranium is retained in the surficial layer of the lateritic soils of the area. Conservative contaminants are not retained by the soils and are transported into the groundwater. Subsequently, they migrate relative to the groundwater flow rate towards the river system down hydraulic gradient of the irrigation area.

Geochemical kinetic modelling codes have been utilised in the assessment of the potential for contaminant release during the rehabilitation of mine sites. Two uranium mines in eastern Germany have been used as study sites for the application of the kinetic models. Results from the study will be used in the formulation of options for the rehabilitation of the two sites. The predicted results are in good agreement with results from other studies using different techniques and can also predict the water quality of pilot-scale flooding experiments.

A mechanistic model explains the differential rates of accumulation of alkaline-earths in the tissue of the freshwater mussel Velesunio angasi as being determined by their different loss rates. These rates of loss are hypothesised to be directly related to the solubility of the alkaline-earth metal when deposited in phosphate-bearing, extracellular granular deposits that are dispersed throughout the tissue. This model is further tested by an experimental determination and comparison of the biological half-lives of the non-alkaline earths 2t°pb, 6°Co with that of 45Ca in the mussel's tissue, that are predicted to vary in their solubilities as phosphates. The experimental results indicated that the ranking of biological half-lives of these elements is 21°pb > 6°C0 ~ 45Ca. These results are in accord with their predicted solubility constants and previous experimental studies, and hence are consistent with the model. Several assumptions that are implicit in this model are presented and compared for consistency with findings from other studies on V. angasi and other species of freshwater mussels.

In the present study, a detailed examination of tailings cores and pore waters, kinetic column test work and geochemical modelling was combined with results from earlier studies to examine the key processes governing the geochemical stability of the Ranger tailings. Conclusions drawn from the work clearly demonstrates that the solid state speciation and mobility of metals and radionuclides in the tailings pile are governed by the processes of oxidative dissolution of sulfide minerals, weathering of phyllosilicates and organic matter diagenesis.

The extended free ion activity model (FIAM) was developed by integrating concepts from the original FIAM into biological receptor theory, to obtain a conceptual model that more precisely quantifies the interaction of chemical species at biological receptor sites. The extended FIAM was tested by determining the acute (48 h) valve movement behavior (VMB) (measured in terms of the duration of valve opening) of the Australian freshwater bivalve, Hyridella depressa, to increasing concentrations of total Cd or Cu, in a standard synthetic water under conditions of varying pH (6.5-7.5) and/or dissolved organic carbon (as model fulvic acid (FA)) concentrations (0-11.2 mg L(-1)). Valve movement behavior, measured using an automated data acquisition system, was shown to be a quantifiable and rapid, real-time endpoint for assessing the toxic effects of Cd and Cu exposures. The VMB of H. depressa to Cd was independent (p > 0.05) of pH and/or model FA concentration. In contrast, the VMB of H. depressa to Cu was highly dependent (p < 0.001) on pH and/or model FA concentration; individuals were more sensitive to Cu at low pH and model FA concentrations. The VMB of H. depressa was directly proportional to the activity of the free metal ion (Cd2+), for the linear region of the concentration-response curves. In contrast, the VMB of H. depressa was a weighted function of the activities of the free metal ion and the 1:1 metal hydroxide species (i.e. 2.02 x Cu2+ + CuOH+), whereby Cu2+ had a two-fold greater binding affinity than CuOH+ at the cell membrane surface. Moreover, the results for Cd and Cu are consistent with the extended FIAM, as opposed to the original FIAM, where the result for Cu would be regarded as an exception. The extended FIAM explained 98% of the variability in VMB, whereas the original FIAM explained only 63% (i.e. an improvement of 35%). The improved predictability of organism response to Cu is relevant to advancing water quality guidelines for protecting aquatic biota.

The present study integrates the concepts of the free ion activity model (FIAM) into biological receptor theory (BRT; i.e. pharmacodynamic principles) to obtain a more rigorous conceptual model; one that more precisely quantifies the interaction of chemical species at biological receptor sites. The developed model, which is viewed as an extended FIAM, explains the conditions under which the FIAM will be effective in explaining biological response (BR). It establishes that BR is directly proportional to the activity of the free metal ion in the linear regions of concentration-response curves only. Additionally, it indicates that [X-cell], the activity of free surface sites on the cell membrane, does not need to be constant in the region of BR, as assumed by the original FIAM. The extended FIAM was tested by re-examining concentration-response data from the literature on aquatic organisms exposed to several ecotoxicologically-relevant trace metals. These data, which would be considered exceptions to the original FIAM, were found to be consistent with the extended FIAM. Due to its more rigorous conceptual basis, the extended FIAM is capable of modelling concentration-response experiments from a wider range of water chemistry conditions (i.e. varying pH, hardness and dissolved organic matter) than the original model and, as such, potentially provides a more useful tool for evaluating metal-organism interactions. This study proposes, for the first time, a quantitative method of uncoupling the biological effects of a metal hydroxide (1:1) complex from that of amelioration of the free metal ion (M(z+)) by H(+). Since the activities of H(+) and metal-hydroxide cannot be independently varied, it has been previously very difficult to evaluate whether metal-hydroxide species contribute to eliciting a BR. Furthermore, the extended FIAM can directly derive fundamental information from concentration-response curves, such as the binding constants of H(+) or the hardness cations (Ca(2+) and/or Mg(2+)) to the cell membrane surface of aquatic organisms.

Fish (dusky flathead – Platycephalalus fuscus and luderick – Girella tricuspidata) and shellfish (Anadara trapezia and Saccostrea commercialis) samples from Lake Illawarra in south-eastern Australia were collected in 1993 and 2000 and analysed for a range of metals. Sediments with which the shellfish were in contact were also examined. The results were compared with shellfish data collected in 1976 and in an independent study in 1993. No reported data were available for comparison with the fish metal results. The results showed that trace metal concentrations in both fish and shellfish were generally low and represented minimal health risk. The dusky flathead, a predator species, had detectable concentrations of mercury, while the luderick, a herbivore, had values below detection limits. Metal concentrations in shellfish were in general agreement with those found in other studies, and showed that no apparent changes were occurring over time, except those that could be explained by changes in the age of the shellfish. Only copper in Lake Illawarra oysters showed greater concentrations than found in other south-eastern Australian estuaries. It is recommended that future studies focus on organic and microbial contamination.

Reliable acquisition of the pigeon's key-peck response resulted from repeated unconditional (response-independent) presentations of food after the response key was illuminated momentarily. Comparison groups showed that acquisition was dependent upon light-food pairings, in that order.

Rats were trained to criterion to respond to 1 dimension of a 2-dimensional discrimination and then to respond either (a) to the previously negative stimulus or (b) to the previously irrelevant dimension. One half of the Ss received 200 training trials beyond criterion before undergoing the discrimination shifts. Overtraining had no effect, and (b) was accomplished faster than (a) by both criterion and overtrained Ss.

The crayfish described here was discovered while the author was carrying out an investigation on the biology of the crayfishes of central and southeastern Illinois.2 According to the collection data compiled during this investigation, this crayfish is limited in distribution to the southern part of Illinois and was not found in the collections which were made in the eastern and central parts of the state.