Recent Developments in Species Sensitivity Distribution Modeling.

The species sensitivity distribution (SSD) is a statistical approach that is used to estimate either the concentration of a chemical that is hazardous to no more than x% of all species (the HCx) or the proportion of species potentially affected by a given concentration of a chemical. Despite a significant body of published research and critical reviews over the past 20 yr aimed at improving the methodology, the fundamentals remain unchanged. Although there have been some recent suggestions for improvements to SSD methods in the literature, in general, few of these suggestions have been formally adopted. Furthermore, critics of the approach can rightly point to the fact that differences in technical implementation can lead to marked differences in results, thereby undermining confidence in SSD approaches. Despite the limitations, SSDs remain a practical tool and, until a demonstrably better inferential framework is available, developments and enhancements to conventional SSD practice will and should continue. We therefore believe the time has come for the scientific community to decide how it wants SSD methods to evolve. The present study summarizes the current status of, and elaborates on several recent developments for, SSD methods, specifically, model averaging, multimodality, and software development. We also consider future directions with respect to the use of SSDs, with the ultimate aim of helping to facilitate greater international collaboration and, potentially, greater harmonization of SSD methods. Environ Toxicol Chem 2021;40:293-308. © 2020 SETAC.

Revisions to the derivation of the Australian and New Zealand guidelines for toxicants in fresh and marine waters.

The Australian and New Zealand Guidelines for Fresh and Marine Water Quality are a key document in the Australian National Water Quality Management Strategy. These guidelines released in 2000 are currently being reviewed and updated. The revision is being co-ordinated by the Australian Department of Sustainability, Environment, Water, Population and Communities, while technical matters are dealt with by a series of Working Groups. The revision will be evolutionary in nature reflecting the latest scientific developments and a range of stakeholder desires. Key changes will be: increasing the types and sources of data that can be used; working collaboratively with industry to permit the use of commercial-in-confidence data; increasing the minimum data requirements; including a measure of the uncertainty of the trigger value; improving the software used to calculate trigger values; increasing the rigour of site-specific trigger values; improving the method for assessing the reliability of the trigger values; and providing guidance of measures of toxicity and toxicological endpoints that may, in the near future, be appropriate for trigger value derivation. These changes will markedly improve the number and quality of the trigger values that can be derived and will increase end-users' ability to understand and implement the guidelines in a scientifically rigorous manner.

Hardness corrections for copper are inappropriate for protecting sensitive freshwater biota.

Toxicity testing using a freshwater alga (Chlorella sp.), a bacterium (Erwinnia sp.) and a cladoceran (Ceriodaphnia cf. dubia) exposed to copper in synthetic and natural freshwaters of varying hardness (44-375 mg CaCO3/l), with constant alkalinity, pH and dissolved organic carbon concentration, demonstrated negligible hardness effects in the pH range 6.1-7.8. Therefore, the use of a generic hardness-correction algorithm, developed as part of national water quality guidelines for protecting freshwater biota, is not recommended for assessing the toxicity of copper to these, and other, sensitive freshwater species. Use of the algorithm for these sensitive species will be underprotective because the calculated concentrations of copper in water that cause a toxic effect will be higher.

Freezing of sediments inappropriate for pore water selenium analysis.

The common practice of freezing sediment cores for later chemical investigation was shown to be inappropriate for samples containing selenium. Pore waters from frozen estuarine sediment cores contained up to eighty times the selenium content of those extracted from chilled but unfrozen cores. Experiments suggested that the increase in selenium concentrations resulted from rupturing the cells of selenium-accumulating bacteria present in the samples.

Corer-reactors for contaminant flux measurement in sediments.

Design details and operating instructions are provided for a sediment corer that can be converted into a reactor for the measurement of the fluxes of contaminants from sediments to overlying waters. The corer-reactor permits measurements, under controlled laboratory conditions, on intact, largely undisturbed sediment cores, without significantly perturbing the physical and chemical conditions found in the field. The design can be constructed in-house for around US dollar 240 (A dollar 400) (excluding motor and corer lid), making it a relatively inexpensive system.

Sample storage artifacts affecting the measurement of dissolved copper in sulfidic waters.

Sample preservation and storage procedures (acidification with HNO(3) and storage in plastic bottles) normally employed prior to the determination of dissolved Cu in sulfidic waters were compared with sample preservation involving the initial oxidation of sulfide with H(2)O(2) or S(2)O(5)(2-) followed by acidification. Acidification alone was demonstrated to be inadequate and resulted in a significant underestimation of dissolved Cu (losses ranging from 50% to >90%). Similar losses were observed in both polyethylene and Teflon storage bottles. Experiments suggest that losses of copper occur following sample acidification owing to the formation of stable copper sulfide phases which adsorb onto container surfaces. It is therefore recommended that an oxidative pretreatment step is carried out prior to the acidification of porewaters collected for metal analysis. The results of this study suggest that much of the previous data reporting dissolved Cu concentrations in sulfidic waters and porewaters may be in error.

The fate of endosulfan in aquatic ecosystems.

Endosulfan, one of the major pesticides used in cotton-growing, is of environmental concern because of its toxicity to fish and its apparent persistence in the environment. This study examines the distribution and degradation pathways for endosulfan in an aquatic system and the processes by which it is removed. In the alkaline waters of the cotton region, hydrolysis is the dominant degradation process. By this mechanism alone, the expected half-lives for the alpha- and beta-endosulfan isomers were found to be 3.6 days and 1.7 days, respectively. Partitioning studies showed, however, that the major proportion of endosulfan would associate with the sediments (log Koc(alpha) 3.6 and log Koc(beta) 4.3). Field studies confirmed the presence of high concentrations in sediments. Microcosm experiments showed that loss of endosulfan was slower than predicted from hydrolysis rates. Models are presented to explain how desorption from sediment limits the loss of endosulfan from a system.

The impact of the banning of tributyltin-based antifouling paints on the Sydney rock oyster, Saccostrea commercialis.

Two years after the banning in New South Wales (Australia) of tributyltin (TBT)-based antifouling paints for vessels under 25 metres in length, the impact on the Sydney rock oyster, Saccostrea commercialis, has been assessed. Reduced growth and shell deformities present before banning were found to be absent and healthy oysters contained TBT at concentrations close to the detection limit of 0.2 micrograms Sn kg-1. High tissue concentrations of both copper and zinc, prior to banning were also significantly reduced. This behaviour was predicted by field experiments which showed that TBT had a synergistic effect on the uptake of copper. The distribution of both TBT and copper in the various organs of the oyster were examined in an attempt to explain this synergism.

Investigations of the impact of effluent from the Ok Tedi copper mine on the fisheries resource in the Fly River, papua new guinea.

The Ok Tedi copper mine currently discharges overburden and partially treated ore residues into the Ok Tedi, a major tributary of the Fly River. At peak production these discharges will result in an increase in the suspended solids levels in the Fly River from a background of 76 mg L(-1) to approximately 800 mg L(-1), and an increase in median particulate copper levels from 90 µg g(-1) to 1220 µg g(-1). The dissolved copper levels are not expected to exceed 10 µg L(-1). The Strickland River, a tributary of the Fly River, has natural suspended solids levels in excess of 500 mg L(-1) and provided a natural bioassay for the impacts of elevated suspended solids levels. The fish communities of the Strickland River were dominated by the sediment-tolerant Ariidae catfish, but the levels of biomass caught per standard sampling effort were comparable to those in the Fly River. Laboratory bioassays were performed to assess the impact of particulate associated copper. The fish fauna of the Fly River does not include any standard test species, and it is unlikely that standard species would be unaffected by the high suspended solids levels of the Fly River. Test species were selected on the basis of ecological importance. Two freshwater prawns,Macrobrachium rosenbergii andMacrobrachium sp., a catfish,Neosilurus ater, and a cladoceran,Ceriodaphnia dubia, were tested for acute toxicity and bioaccumulation of copper from particulates. There was no evidence of acute toxicity to prawns or fish, nor for bioaccumulation by prawns. Acute toxicity toC. dubia and bioaccumulation byN. ater were probably due to dissolved copper in the test environments. The test results indicated that provided dissolved copper levels did not exceed the predicted levels, there should not be toxic affects of particulate-associated copper in the Fly River.

Solvent-induced photodegradation as a source of error in the analysis of polycyclic aromatic hydrocarbons.

The photodegradation of seven common polycyclic aromatic hydrocarbons (PAHs) has been examined in a range of organic solvents. Reactions followed a first order equation with benzo[a]pyrene and benzo[a]anthracene being the most rapidly photodegraded. Generally, the more polar the solvent the faster is the degradation process. A number of photodegradation products were identified by gas chromatography-mass spectrometry. The identification of compounds such as 4-amino-1-naphthalenecarbonitrile and 1H,3H-naphtho[1,8-cd]pyran-1-one clearly indicated that the solvent molecules have taken part in the formation of these compounds. Solvent-induced photodegradation is shown to be an important consideration in choosing the optimum solvent for the best analytical recoveries of PAHs from various matrices.

Electrolytic preconcentration in instrumental analysis.

The use of electrolytic deposition as a separation and preconcentration step in trace metal analysis is reviewed. Both the principles and applications of the technique are dealt with in some detail. Electrolytic preconcentration can be combined with a variety of instrumental techniques. Special attention is given to stripping voltammetry, potentiometric stripping analysis, different combinations with atomic-absorption spectrometry, and the use of flow-through porous electrodes. It is pointed out that the electrolytic preconcentration technique deserves more extensive use as well as fundamental investigation.

Determination of the chemical forms of trace metals in natural waters, with special reference to copper, lead, cadmium and zinc.

Methods used to differentiate between the various chemical forms of a metal in a natural water are critically reviewed. The methods range from simple procedures which discriminate between weakly and strongly complexed forms of the metal, to comprehensive analytical schemes which can determine as many as seven species of each metal. The many problems involved in this exacting area of trace analysis are discussed in detail.

Trace metals species in sea-water-I: removal of trace metals from sea-water by a chelating resin.

A significant fraction of the copper, lead, cadmium and zinc in sea-water exists in a form which is not retained by a chelating resin (Chelex-100) or extracted by ammonium pyrrolidinedithiocarbamate. Anodic stripping voltammetric results suggest that the major part of the unavailable trace metal is adsorbed on, or occluded in, organic or inorganic colloidal particles. An ionic equilibria computer program was used to predict the effect of various complexing agents on trace metal species in sea-water. Citric acid and amino-acids, with the exception of l-cysteine, were shown to be unimportant as complexing agents, and the ability of an EDTA-like ligand to complex Cu, Pb, Cd and Zn is controlled entirely by the concentrations of the ligand and of "labile" Fe(III) and Cr(III) in sea-water, since these two ions together will react quantitatively with EDTA. l-Cysteine, if present in sea-water, would also complex the trace metals.

Fluorimetric method for the determination of long-chain amines in water.

A method is presented for the determination of long-chain quaternary ammonium salts, tertiary amines and secondary amines in water or aqueous raffinates, based on their extraction and fluorimetric determination as amine salts with Eosine Yellowish in toluene-hexanol (4:1) as solvent. No interferences were obtained from metal ions, or chloride, nitrate or phosphate ions when a back-washing method was applied to the sample extract. The method allows the determination of long-chain tertiary amines down to 4 ppM.

A catalytic method for the determination of cobalt impurities in reactor cooling-water circuits.

Metal impurities in reactor cooling-water circuits must be kept to a minimum. A method is described for the determination of trace levels of cobalt in water samples, based on catalysis of the hydrogen peroxide oxidation of Alizarin Red S. The determination is carried out at pH 11.0 in a phosphate buffer under conditions where the reaction rate is a maximum. Interfering impurities are removed by an ion-exchange separation. The method enables cobalt to be determined in water samples down to 10(-4)mug ml , or 5 x 10(-5)mug ml in samples where an ion-exchange separation is not required.