Equilibrium Partitioning Method Research Articles

Forms of polycyclic aromatic hydrocarbon in the formation of sewage sludge toxicity to Heterocypris incongruens

The aim of the present study was to evaluate to what degree polycyclic aromatic hydrocarbon (PAH) determines sewage sludge toxicity in relation to Heterocypris incongruens. Six differing sewage sludges with increasing contents of polycyclic aromatic hydrocarbons were selected for the present study. As well as total PAH content, the content of the potentially bioavailable fraction was also determined in the sewage sludges using a method of mild-solvent extraction (with n-butanol). The PAH content was also calculated in the sewage sludge pore water by the equilibrium partitioning method. The total PAH content in the sewage sludges studied were in the range 3.60 to 27.95 mg kg − 1 . The contribution of the n-butanol extracted fraction was in the range 38.7 to 75.4%. In the group of individual PAHs, 4- and 5-ring compounds had the highest content in the potentially bioavailable group. H. incongruens mortality in the range 6.7 to 100%, depending both on the sewage sludge and the dose applied. An increase of the sewage sludge dose usually resulted in an increase in toxicity. At the highest dose, a 100% mortality of H. incongruens was found in half of the sludges. The lowest dose, irrespective of the sludge type, caused over 40% growth inhibition. However, the results obtained did not allow for the establishing of an unambiguous relationship between various sludge toxicity levels and the content of potentially bio-available PAHs. In some cases only, the extraction using n-butanol explained the high difference in toxicity despite a slight differentiation in the PAH content.

Environmental levels of Linear alkylbenzene Sulfonates (LAS) in sediments from the Tagus estuary (Portugal): environmental implications

Sediments from the Tagus estuary (Portugal) were collected at 40 stations in July and December 2004. Total LAS concentrations ranged between 0.03 and 17.76 mg LAS.kg(-1) dry weight in July, and between 0.09 and 9.57 mg LAS.kg(-1) in December. Highest LAS concentrations were found at the upper northern part of the estuary, coincident with the localisation of an important waste water treatment station. According to the Predicted No Effect Concentration (PNEC) of 8.1 mg.kg(-1) derived for this compound, Environmental Risk Assessment (ERA) identified a hazard for the ecosystem at the station with the highest LAS concentration, and similar results are obtained by Equilibrium Partitioning Method (EPM). Nevertheless, LAS concentrations decreased significantly between samplings in the stations with the highest LAS concentrations in July, whereas increased LAS concentrations at adjacent stations were found in December. In the remaining stations, LAS concentrations were up to three orders of magnitude lower, representing no hazard for the sediment community.

Potential for Plastics to Transport Hydrophobic Contaminants

Plastic debris litters marine and terrestrial habitats worldwide. It is ingested by numerous species of animals, causing deleterious physical effects. High concentrations of hydrophobic organic contaminants have also been measured on plastic debris collected from the environment, but the fate of these contaminants is poorly understood. Here, we examine the uptake and subsequent release of phenanthrene by three plastics. Equilibrium distribution coefficients for sorption of phenanthrene from seawater onto the plastics varied by more than an order of magnitude (polyethylene >> polypropylene > polyvinyl chloride (PVC)). In all cases, sorption to plastics greatly exceeded sorption to two natural sediments. Desorption rates of phenanthrene from the plastics or sediments back into solution spanned several orders of magnitude. As expected, desorption occurred more rapidly from the sediments than from the plastics. Using the equilibrium partitioning method, the effects of adding very small quantities of plastic with sorbed phenanthrene to sediment inhabited by the lugworm (Arenicola marina) were evaluated. We estimate that the addition of as little as 1 microg of contaminated polyethylene to a gram of sediment would give a significant increase in phenanthrene accumulation by A. marina. Thus, plastics may be important agents in the transport of hydrophobic contaminants to sediment-dwelling organisms.

Terrestrial ecotoxicity and effect factors of metals in life cycle assessment (LCA).

Life cycle impact assessment aims to translate the amounts of substance emitted during the life cycle of a product into a potential impact on the environment, which includes terrestrial ecosystems. This work suggests some possible improvements in assessing the toxicity of metals on soil ecosystems in life cycle assessment (LCA). The current available data on soil ecotoxicity allow one to calculate the chronic terrestrial HC50(EC50) (hazardous concentration affecting 50% of the species at their EC50 level, i.e. the level where 50% of the individuals of the species are affected) of nine metals and metalloids (As(III) or (V), Be(II), Cr(III) or (VI), Sb(III) or (V), Pb(II), Cu(II), Zn(II) and Ni(II)). Contrarily to what is generally advised in LCIA, the terrestrial HC50 of metals shall not be extrapolated from the aquatic HC50, using the Equilibrium Partitioning method since the partition coefficient (K(d)) of metals is highly variable. The experimental ecotoxicology generally uses metallic salts to contaminate artificial soils but the comparison of the EC50 or NOEC obtained for the same metal with different salts reveals that the kind of salt used insignificantly influences these values. In contrast, depending on the metallic fraction of concern, the EC50 may vary, as for cadmium: the EC50 of Folsomia candida, expressed as free Cd in pore water is almost 2.5 orders of magnitude lower than that expressed as total metal. A similar result is obtained with Eisenia fetida, confirming the importance of metals speciation in assessing their impact on soils. By ranking the metals according to the difference between their terrestrial and aquatic HC50 values, two groups are distinguished, which match the hard soft acids and bases (HSAB) concept. This allows to estimate their affinity for soil components and potential toxicity according to their chemical characteristics.

Derivation of predicted no effect concentrations (PNEC) for marine environmental risk assessment: Application of different approaches to the model contaminant Linear Alkylbenzene Sulphonates (LAS) in a site-specific environment

Four sediment-dwelling marine organisms were exposed to sediments spiked with increasing concentrations of Linear Alkylbenzene Sulphonate (LAS). The selected endpoint mortality was reported daily and acute LC 50 (96 h), as well as final LC 10 values were calculated for the derivation of environmentally safe predicted no effect concentrations (PNEC) for the sediment compartment. PNECs were estimated by both application of assessment factors (AF) and the equilibrium partitioning method (EPM) as proposed by the EU TGD. Finally, environmental risk assessment in a site-specific environment, the Sancti Petri Channel, South Iberian Peninsula, was carried out at three different sampling stations with known environmental LAS concentrations. PNECs obtained by the assessment factor approach with acute toxicity data were one to two orders of magnitude lower than those from the equilibrium partitioning method. On the other hand, when applying lower AFs to the estimated LC 10 values, the PNECs obtained by both approaches were more similar. Environmental risk assessment carried out with the estimated PNECs in a site specific environment with known sediment LAS concentrations revealed that PNECs obtained with acute toxicity data were over conservative whereas those obtained with AF = 10 on LC 10 data and EPM produced more realistic results in accordance with field observations carried out in the study area.

Environmental risk limits for antifouling substances

In 1989, the EU restricted the use of tributyl-tin (TBT) and the International Maritime Organisation (IMO) decided for a world-wide ban on TBT in 2003. As a replacement for TBT, new antifouling agents are entering the market. Environmental risk limits (ERLs) are derived for substances that are used as TBT-substitutes, i.e. the compounds Irgarol 1051, dichlofluanid, ziram, chlorothalonil and TCMTB. ERLs represent the potential risk of the substances to the ecosystem and are derived using data on (eco)toxicology and environmental chemistry. Only toxicity studies with endpoints related to population dynamics are taken into account. For Irgarol 1051 especially plants appear to be sensitive; the mode of action is inhibition of photosynthetic electron transport. Despite the higher sensitivity of the plants, the calculated ERL for water based on plants only is higher than the ERL based on all data due to the lower variability in the plant only dataset. Because there is a mechanistic basis to state that plants are the most sensitive species, we propose to base the ERL for water on the plants only dataset. As dichlofluanid is highly unstable in the water phase, it is recommended to base the ERL on the metabolites formed and not on the parent compound. No toxicity data of the studied compounds for organisms living in sediments were found, the ERLs for sediment are derived with help of the equilibrium partitioning method. For dichlofluanid and chlorothalonil the ERL for soil is directly based on terrestrial data, for Irgarol 1051 and ziram the ERL for soil is derived using equilibrium partitioning. Except for Irgarol 1051, no information was encountered in the open literature on the environmental occurrence in The Netherlands of the chemicals studied. The measured concentrations for Irgarol 1051 are close to the derived ERL. For this compound it is concluded that the species composition and thereby ecosystem functioning cannot be considered as protected.

The evaluation of the equilibrium partitioning method using sensitivity distributions of species in water and soil

The equilibrium partitioning method (EqP-method) can be used to calculate soil quality standards (expressed in mg/kg) from aquatic quality standards (expressed in μg/l) using a partitioning coefficient. The validity of this application of the EqP-method was studied comparing aquatic with terrestrial toxicity data. The data set collected for deriving environmental quality standards in the Netherlands, was used for this study. For 10 organic substances (chlorpyrifos, atrazine, carbofuran, pentachlorophenol, chlordane, aldrin, trichlorobenzene, heptachlor, trichlorophenol and trichloroethene) and for 8 metals, sufficient data were available. The aquatic toxicity data were multiplied by the partitioning coefficient in order to obtain aquatic data expressed in mg/kg. For some compounds the terrestrial toxicity data were significantly higher than the aquatic data but for other compounds it was the other way around. These differences indicate that the EqP-method can give significant over-or underestimations, due to inaccurate partitioning coefficients or differences in species sensitivities. These over- or underestimations can have an impact on the setting of environmental quality standards which are based on the hazardous concentration 5% (HC5) values. The uncertainty in the calculation of HC5 values attributed to the use of the EqP-method, was quantified. The HC5 values derived using the EqP-method were in 5% of the cases more than 20 times higher than the corresponding HC5 values that were derived directly from soil toxicity tests. Despite of this uncertainty the use of the EqP-method can still be advocated for setting soil quality guidelines when only a very limited number of terrestrial toxicity data are available.

Strategies for risk assessment of existing chemicals in soil

In the risk assessment of industrial chemicals, an assessment of the risk to soil should be performed whenever relevant inputs occur via the following pathways: application of sewage sludge, wet or dry deposition, application as a pesticide constituent (e.g. solvent or metabolite), irrigation. An evaluation of the results for 34 chemicals from the first EU priority list showed that only 35% of the risk assessments for the terrestrial compartment were performed on the basis of at least 2 valid tests with soil organisms. In the vast majority of cases, the equilibrium partitioning method was used to extrapolate from aquatic to soil toxicity. However, no indications exist for a correlation between aquatic and terrestrial toxicity. Moreover, the exposure routes for soil organisms (uptake via pore water, air included in soil pores, ingestion of soil particles) are much more complex than those for aquatic organisms. As a new approach, it is therefore suggested that, in cases of relevant exposure (e.g. estimated or measured concentrations of >10 µg/kg), an assessment should generally be performed on the basis of valid terrestrial tests rather than on an extrapolation from the aquatic toxicity. It is recommended that prolonged exposure tests should be used already for an initial assessment of substances that have a strong tendency to adsorb on soil particles and thus a long residence time in soil. A decision scheme for the risk assessment of industrial chemicals in soil is presented, trigger values, testing strategies as well as assessment factors for derivation of a Predicted No Effect Concentration (PNECsoil) are discussed. An example of a terrestrial risk assessment for substances from the first EU priority list is given in order to illustrate current practice.

The newly proposed EU risk assessment concept for the sediment compartment

Within the frame of the EU Existing Chemicals Regulation (793/93/EEC), a new concept for the assessment of the sediment compartment has been developed. During the assessment process it has become clear that for substances that strongly adsorb or bind to sediment the equilibrium partitioning method (EPM) presently employed is not sufficient. The new approach is therefore based on long-term sediment tests with benthic organisms. A testing strategy has been developed which considers species which represent different habitats and feeding strategies in order to adequately address all possible routes of exposure. The new concept has proven to be valuable in risk assessments, two examples (3,4-DCA, DODMAC) of which are shown in more detail.

Maximum permissible and negligible concentrations for metals and metalloids in the Netherlands, taking into account background concentrations

The aim of the paper is to provide interested parties the methods that were used for generic hazard assessment in The Netherlands, and the resulting so-called Maximum Permissible Concentrations (MPCs) and the Negligible Concentrations (NCs) for 18 metals and metalloids. The MPCs and NCs were derived for water, sediment, soil and air. The concentration in the environment above which the risk of adverse effects was considered unacceptable to ecosystems is called the MPC. The MPCs take into account that the substances are distributed among the different environmental compartments, and are harmonised accordingly. Included in the MPC and NC are existing background concentrations in The Netherlands following the so-called ‘added risk approach’. The MPCs served as a basis for the Dutch government to set generic Environmental Quality Standards (EQS) in The Netherlands. EQS in turn are used by the Dutch Government to assess the environmental quality and for other environmental policy purposes.Depending on the number of ecotoxicological data, the reliability of the MPCs differed. For water only, MPCs were based on sufficient data, but for the other compartments, there is a great demand for further ecotoxicity data. For soil and sediment, almost no ecotoxicological data were available, and MPCs for those compartments have, in many cases, been derived from MPCs in water applying a modified equilibrium partitioning method (modified EqP-method), resulting in MPCs with greater uncertainty.Some of the methods and underlying assumptions that have been used may warrant further discussion. For example, the lack of data, the factor 100 between MPC and NC, the background concentration, the essential elements, the modified EqP-method and bioavailability, speciation and water chemistry, acid volatile sulfide, and the method that is used for harmonising MPCs for air.Interested parties may use the information and methods on the MPCs and NCs as a general guideline for deriving generic environmental quality standards.

Maximum permissible and negligible concentrations for some organic substances and pesticides

The aim of the paper is to provide interested parties the methods that were used for generic hazard assessment in The Netherlands, and the resulting so-called maximum permissible concentrations (MPCs) and the negligible concentrations (NCs) for approximately 150 organic substances and pesticides. The MPCs and NCs were derived for water, sediment, and soil. The concentration in the environment above which the risk of adverse effects was considered unacceptable to ecosystems is called the MPC. The MPCs take into account that the substances are distributed among the different environmental compartments, and are harmonized accordingly. The MPCs served as a basis for the Dutch government to set generic environmental quality standards (EQS) in The Netherlands (IWINS,15). EQS in turn are used by the Dutch Government to assess the environmental quality and for other environmental policy purposes. Concentrations in the environment below which the occurrence of adverse effects is considered to be negligible are called NCs. Hazards must be reduced when the environmental concentration of a substance exceeds its MPC. In-between this limits reduction of hazards is preferable. The MPC is a scientifically derived hazard limit. The NC is simply defined as 1% of the MPC. In general, there is a great demand for ecotoxicological data that currently limits a more reliable estimate of many MPCs. For water, approximately half of the MPCs are derived on the basis of four or more NOECs (no observed effect concentrations). For the other half, MPCs are based on only a few chronic or acute tests. For soil and sediment, however, almost no ecotoxicological data are available, and MPCs for those compartments have, in many cases, been derived from MPCs in water applying the equilibrium partitioning method (EqP-method), resulting in MPCs with greater uncertainty. Some of the methods and underlying assumptions that have been used may need improvement. For example, the factor between MPC and NC, the statistical extrapolation method, the method that is used for secondary poisoning, the role of the background concentrations of ‘naturally’ occurring substances, and the bioavailability and the EqP-method. There is a great need for hazard limits, and the present compilation tries to provide those as well as identifying research gaps.

組換え型ヒト血清アルブミンの多分子結合能及びエステラーゼ類似作用

The ligand binding properties and esterase-like activity of recombinant human serum albumin (rHSA) expressed by Pichia pastoris were compared with those of plasma derived human albumin (pHSA). The binding of long fatty acid ions was determined by the equilibrium partition method using radiolabeled palmitate. The association constants and the number of binding sites of diazepam, salicylate and warfarin were determined by specific and nonspecific binding models. The high affinity binding of bilirubin was kinetically determined from the oxidation rate of free bililubin in the binding mixture. The binding parameters of these five ligands obtained with rHSA were within the same range observed with pHSA preparations. The kinetic parameters for hydrolytic activity of rHSA toward p-nitrophenyl acetate was also similar to pHSA. These results indicate that rHSA and pHSA have the same functional property.

An evaluation of current methods for developing sediment quality guidelines for 2,3,7,8-tetrachlorodibenzo-p-dioxin

There are currently few proposed sediment quality guidelines and no promulgated regulatory criteria for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in sediments. Among the eight major approaches used to develop sediment quality guidelines, only three have been used to date in developing proposed guidelines for TCDD: the background method, the equilibrium partitioning (EqP) method, and the tissue-residue based (TRB) method. At present, nineteen proposed sediment quality guidelines for TCDD have been proposed in the U.S. and other countries, including seven derived exclusively for the protection of human health, seven derived exclusively for the protection of aquatic organisms and/or wildlife, and five that were derived for the protection of both human and ecological receptors. In this paper, the technical basis and proposed regulatory objectives of these guidelines were evaluated in an effort to assess the feasibility of deriving a national sediment quality guideline for TCDD. Guidelines derived from the background method inferred that TCDD concentrations in sediments should not exceed the detection limit (1 to 10 parts per trillion; pg/g) of the currently accepted high resolution gas chromatography/mass spectroscopy analytical method, and for one guideline, an outdated analytical detection limit of 1,000 parts per trillion. Guidelines developed by the EqP and TRB methods varied over several orders of magnitude (0.014 to 210 parts per trillion, dry weight basis; and 200 to 1×107 pg/gOC). These large variations are the result of data gaps in our knowledge of TCDD toxicity, and the physical and chemical parameters that govern its fate and transport in aquatic systems.

Deriving quality criteria for water and sediment from the results of aquatic toxicity tests and product standards: Application of the equilibrium partitioning method

The present paper summarizes an approach recently proposed in The Netherlands to use the equilibrium partitioning (EP) method to derive a coherent set of quality criteria for aquatic systems. The quality criteria refer to dissolved concentrations, the concentrations in the suspended particles, the total (dissolved + particulate) concentrations and the concentrations in the sediment. The quality criteria have been derived for standard sediment, standard water and standard suspended matter. Emphasis is laid on the relation between effect data and physicochemical data. Two types of effect data have been used, i.e. effects on aquatic toxicity (direct effects) and health related effects (product standards). Both types of data have been translated into the above mentioned criteria by means of EP. For the calculation of criteria in sediment and suspended matter solids-water partition coefficient K sw have been used. Examples have been given for cadmium and hexachlorobenzene. The handled equations have been summarized in diagrams.

Partitioning of Hydrophobic Nonpolar Volatile Organics between the Aqueous and Surfactant Aggregate Phases on Alumina

Abstract The partitioning of three hydrophobic volatile organic compounds (VOCs)-chloroform, benzene, and 1,3-dichlorobenzene—between the aqueous and two surfactant aggregate phases (sodium dodecylsulfate and sodium dodecylbenzene-sulfonate) on alumina was studied using the technique of equilibrium partitioning method in closed systems. Facile incorporation of these compounds into hemimicelles were observed. The partition constants correlated well with traditional hydrophobicity indicators such as octanol-water partition constants and molar solubilities of the hydrophobic compounds in the aqueous phase.

Current approaches to developing sediment quality criteria

AbstractCurrent approaches to developing sediment quality criteria are reviewed and separated into two major groups: those approaches that provide only chemical‐by‐chemical criteria and those that provide criteria for chemical mixtures also. The individual approaches include background sediment chemistry, water quality criteria, sediment/water equilibrium partitioning, sediment bioas‐say, screening level concentration, apparent effects threshold and sediment quality triad. Based on the evaluation of the two groups and seven individual approaches, it is concluded that, for chemical‐by‐chemical criteria, the equilibrium partitioning method shows promise; for criteria that are also applicable to chemical mixtures, the apparent effects threshold/sediment quality triad approaches appear to be most appropriate. Recommendations are made concerning specific immediate research needs, related to developing effective, usable sediment quality criteria.

Binding of Levonorgestrel, Norethisterone and Desogestrel to Human Sex Hormone Binding Globulin and Influence on Free Testosterone Levels

The progestogens desogestrel, levonorgestrel, lynestrenol and norethisterone are known to display certain androgenic effects. Apart from direct androgen receptor interaction, binding to sex hormone binding globulin (SHBG) and displacement of testosterone could lead to an increase in free, metabolically active testosterone. The affinities for SHBG binding of some progestogens including levonorgestrel, norethisterone and the active metabolite of desogestrel, 3-keto-desogestrel, were compared using an equilibrium partition method, and the distribution between free and protein-bound testosterone during progestogen therapy was calculated with the use of a computer program. During treatment with desogestrel, levonorgestrel and norethisterone alone, testosterone displacement could account for a slight increase in free testosterone, though the decrease in serum SHBG following treatment was found to be more important in this respect. Also during treatment with combinations of ethinyl estradiol and levonorgestrel for oral contraception, testosterone displacement could theoretically have a slight influence on free testosterone levels. Combinations with ethinyl estradiol and desogestrel or norethisterone, on the other hand, cause an increase in SHBG concentration and as a result a fall in free testosterone which could not be compensated via testosterone displacement.

Partitioning of chloromethanes between aqueous and surfactant micellar phases

The partition constants for three volatile organic chemicals (VOCs)—methylene chloride, chloroform and carbon tetrachloride—between aqueous and surfactant micellar phases were determined using an equilibrium partitioning method. The surfactants used were sodium dodecylbenzene sulfonate (DDBS), sodium dodecylsulfate (DDS) and hexadecyltrimethyl ammonium bromide (HTAB). The vapor concentration of the VOCs remained unchanged until the critical micellar concentration (CMC) of the surfactant was reached. Above the CMC the vapor concentration decreased linearly with increasing surfactant concentration in the aqueous phase. The partition constants ( K m) were observed to increase with increasing ionic strength of the solution. The partition constants also increased with increasing hydrophobicity of the VOCs. A pseudo-two-phase model was used to determine the K m values and was found to fit the experimental data well. Cationic micelles of HTAB gave larger K m values than anionic micelles of DDS and DDBS surfactants. K m values also increased with increasing temperature. From a thermodynamic treatment of the equilibrium process the values of the partition constants for transfer of VOCs from an ideal vapor phase to the micellar phase were calculated. These values were found to fall in between the values for aliphatic hydrocarbons and alcohols.

Interacting Binding Sites of Isoleucyl‐tRNA Synthetase from Escherichia coli Studied by Equilibrium Partition

The binding of tRNAIIe to isoleucyl-tRNA synthetase in the presence of isoleucine or ATP was investigated using the equilibrium partition method. Isoleucine decreased the affinity of tRNAIIe for the enzyme by a factor of about 5. For the free standard energy of interaction a value of about 1 kcal/mol (4.2 kJ/mol) was calculated. ATP exhibits qualitatively the same effect as isoleucine. A binding of two molecules isoleucine per molecule of enzyme could not be demonstrated even in the presence of ATP and pyrophosphatase.

Testosterone binding capacity in relation to the production and metabolism of testosterone in dogs, experiences of a new method

Testosterone dynamics were studied in vivo in five male dogs using constant infusion techniques, for the first time comparing conscious dogs with anesthetized ones. Barbiturate narcosis was shown to inhibit testosterone production drastically so that plasma levels were near zero for at least 24 h. This causes a 50% reduction of the specific testosterone binding globulin demonstrated in the male dog using a new two-phase equilibrium partition method[5]. An increased association constant was observed at the same time. This protein was shown not to be identical with transcortin. It bound testosterone but not estradiol-17β. The testosterone-protein complex was efficiently extracted by the liver (85–100%). The hepatic metabolic clearance rate was however only 13–20% of the total MCR. It was unaffected by barbiturate anesthesia but showed a small decrease during halothane + oxygen anesthesia, while the extrahepatic MCR decreased to a greater extent during halothane narcosis or laparotomy.