Marnix Vangheluwe

The toxicity of metal mixtures to the estuarine mysid Neomysis integer (Crustacea: Mysidacea) under changing salinity

Water quality criteria are mainly based on data obtained in toxicity tests with single toxicants. Several authors have demonstrated that this approach may be inadequate as the joint action of the chemicals is not taken into account. In this study, the combined effects of six metals on the European estuarine mysid Neomysis integer (Leach, 1814) were examined. Acute 96-h toxicity tests were performed with mercury, copper, cadmium, nickel, zinc and lead, and this as single compounds and as a mixture of all six. The concentrations of the individual metals of the equitoxic mixtures were calculated using the concentration-addition model. The 96-h LC50s for the single metals, at a salinity of 5 per thousand, ranged from 6.9 to 1140 microg/l, with the following toxicity ranking: Hg>Cd>Cu>Zn>Ni>Pb. Increasing the salinity from 5 to 25 per thousand resulted in lower toxicity and lower concentrations of the free ion (as derived from speciation calculations) for all metals. This salinity effect was strongest for cadmium and lead and could be attributed to complexation with chloride ions. The toxicity of nickel, copper and zinc was affected to a smaller extent by salinity. The 96-h LC50 for mercury was the same for both salinities. In order to evaluate the influence of changing salinity conditions on the acute toxicity of metal mixtures, tests were performed at different salinities (5, 10, 15 and 25 per thousand ). The 96-h LC50 value (1.49 T.U.) of the metal mixture, at a salinity of 5 per thousand, was clearly lower than the expected value (6 T.U.) based on the non-additive hypothesis, thus confirming the additive effect of these metals in the marine/estuarine environment. Changing salinity had a profound effect on the toxicity of the mixture. The toxicity clearly decreased with increasing salinity until 15 per thousand. Higher salinities (25 per thousand ) had no further influence on the 96-h LC50 of the mixture which is situated at a value between 4.4 and 4.6. Finally, the relative sensitivity to the selected metals was compared with the relative sensitivity of the commonly used mysid Americamysis (=Mysidopsis) bahia.

Uncertainties in the Environmental Risk Assessment of Metals

As life has evolved in the presence of metals, the assessment of the potential adverse effects of metals on ecosystems requires a different approach than those presently used for man-made organic substances. This article provides a brief review of applications and limitations of current techniques and presents, based on recent research results, suggestions for improving the scientific relevance and accuracy of environmental risk assessments of metals. The importance of the following factors responsible for major uncertainties in current environmental risk assessments of metals are discussed: factors affecting metal bioavailability and toxicity, the potential importance of deficiency effects (for essential metals), and field extrapolation of laboratory toxicity data. Possible (regulatory) consequences of inaccurately assessing the natural background concentrations of metals and acclimatization/adaptation potential of laboratory organisms and resident communities are illustrated using examples of recent research, hypothesis development, and a probabilistic environmental risk assessment.

Probabilistic environmental risk assessment of zinc in dutch surface waters

In the framework of the European Union (EU) New and Existing Chemicals Policy, a regional risk assessment for Zn according to the current technical guidance documents and a probabilistic approach, by mathematically integrating both best-fitting exposure concentrations and species-sensitivity distributions into a probabilistic risk quotient distribution using Monte Carlo analysis, was explored for The Netherlands. Zinc is an essential element, and the current probability distributions may not adequately deal with this property. The threshold Pareto distribution provided the best fit to the chronic Zn toxicity data, resulting in a predicted-no-effect concentration (PNECadd) for dissolved Zn of 34.2 microg/L, whereas use of the conventional normal distribution resulted in a PNECadd for dissolved Zn of 14.6 microg/L. The extracted exposure data resulted in a regional predicted environmental concentration (PEC) for dissolved Zn in the Dutch surface waters of 20.1 microg/L and in PECadd values for dissolved Zn of between 15.5 and 17.3 microg/L, depending on the background correction used. The conventional deterministic risk characterization identified a regional risk for Zn in the Dutch surface waters. The more comprehensive probabilistic approach used in the present study, however, identified only very limited potential risks for the Dutch region. A probabilistic median risk, that the environmental concentration is greater than the no-observed-effect concentration of a species in Dutch surface waters (0.5-0.6%), depending on the inclusion of background correction, was obtained from the best-fitting distributions. Because probabilistic approaches provide a quantifiable and improved assessment of risk and quantification of the uncertainty associated with that assessment, these techniques may be considered as a way to improve the EU risk assessment procedures for data-rich substances.

Mobility and toxicity of metals in sandy sediments deposited on land

A times series of laboratory experiments were conducted to investigate the effect of land deposition of contaminated sediments on the bioavailability and mobility of metals. Four sandy sediments were sampled at sites expected to have elevated levels of cadmium and zinc. The physical and chemical characteristics and ecotoxicity of sediments, pore waters, and leachates were evaluated after periods ranging from 1 to 45 days of land deposition. Cd and Zn retardation and leaching potential were calculated and this simulation gave good predictions of subsequently observed Cd and Zn mobility. The mobility and leaching of Cd and Zn in the sediments increased with decreasing pH and with decreasing content of organic matter. During the deposition an increase in sediment toxicity to plants and an increase in eluate toxicity to invertebrates were observed. A high rate of water flow through the sediment resulted in a lower toxicity enhancement of the sediments and a higher toxicity enhancement of the eluates. This result suggests that water flow through the sediment reduces the actual toxicity of the upper layer of deposited sediment but at the same time intensifies the risk of groundwater contamination.

IMPROVING SEDIMENT-QUALITY GUIDELINES FOR NICKEL: DEVELOPMENT AND APPLICATION OF PREDICTIVE BIOAVAILABILITY MODELS TO ASSESS CHRONIC TOXICITY OF NICKEL IN FRESHWATER SEDIMENTS

Within the framework of European Union chemical legislations an extensive data set on the chronic toxicity of sediment nickel has been generated. In the initial phase of testing, tests were conducted with 8 taxa of benthic invertebrates in 2 nickel-spiked sediments, including 1 reasonable worst-case sediment with low concentrations of acid-volatile sulfide (AVS) and total organic carbon. The following species were tested: amphipods (Hyalella azteca, Gammarus pseudolimnaeus), mayflies (Hexagenia sp.), oligochaetes (Tubifex tubifex, Lumbriculus variegatus), mussels (Lampsilis siliquoidea), and midges (Chironomus dilutus, Chironomus riparius). In the second phase, tests were conducted with the most sensitive species in 6 additional spiked sediments, thus generating chronic toxicity data for a total of 8 nickel-spiked sediments. A species sensitivity distribution was elaborated based on 10% effective concentrations yielding a threshold value of 94 mg Ni/kg dry weight under reasonable worst-case conditions. Data from all sediments were used to model predictive bioavailability relationships between chronic toxicity thresholds (20% effective concentrations) and AVS and Fe, and these models were used to derive site-specific sediment-quality criteria. Normalization of toxicity values reduced the intersediment variability in toxicity values significantly for the amphipod species Hyalella azteca and G. pseudolimnaeus, but these relationships were less clearly defined for the mayfly Hexagenia sp. Application of the models to prevailing local conditions resulted in threshold values ranging from 126 mg to 281 mg Ni/kg dry weight, based on the AVS model, and 143 mg to 265 mg Ni/kg dry weight, based on the Fe model.

Toxicity determination of the sediments of the river Seine in France by application of a battery of microbiotests

This study reports on the potential of the Toxkit microbiotests and the bacterial luminescence test Microtox, to detect and quantify the toxicity of the sediments of the river Seine and a few tributary rivers in France. The objective of the research was to try to identify a minimum test battery for routine toxicity screening of river sediments. Attempts were also made to correlate the ecotoxicological findings with their chemical cause(s) and to evaluate the suitability of the microbiotests as tools for hazard assessment of river sediments. During a 12 months period in 1996–1997, sediments were collected from 12 stations on the river Seine, from Paris to the estuary in Le Havre, and from 7 stations along the rivers Marne, Eure and Commerce. Pore waters were extracted by centrifugation for performance of the bioassays on the interstitial waters. The test battery comprised the following freshwater and estuarine/marine microbiotests: the Microtox® with Vibrio fischeri, the Algaltoxkit F™ with Selenastrum caphcornutum, the Rotoxkit F™ and Rotoxkit M™ with the rotifers Brachionus calyciflorus and B. plicatilis respectively, the Daphtoxkit F™ magna with the cladoceran crustacean Daphnia magna, the Thamnotoxkit F and the Artoxkit M with the anostracan crustaceans Thamnocephalus platyurus and Artemia franciscana respectively, and the Spirostomum assay, an experimental new microbiotest with the ciliate protozoan Spirostomum ambiguum. From all the freshwater stations on the Seine, only one did not give a toxic signal with any of the microbiotests used. No toxicity was detected either in 2 out of the 7 stations on the tributary rivers, nor in the 3 estuarine pore waters. In most stations, toxic efects were observed with several if not all of the microbiotests of the battery, except the Microtox® assay for which only one pore water sample appeared to be toxic. The intensity of the toxicity signal varied substantially from one station to the other, but none of the Toxkit tests was either the most or the least sensitive for all stations. Principal component analysis (PCA) was applied on the data set which allowed to select a minimum battery of only 2 microbiotests, accounting for 90% of the observed variance in the data set: the Thamnotoxkit F and the Algaltoxkit F™. Attempts to correlate the chemical data with the ecotoxicolgical results were biased by the fact that the chemical analyses had been performed only on the sediments (total pollutant load) and not on the pore waters (“bioavailable” contaminants). Comparison of the outcome of the PCA analysis on both the ecotoxicological and chemical data sets revealed positive correlation between the toxic effects and the metal content of the sediments. The study corroborates analogous findings made by the same laboratory on a very large number of sediment pore waters from rivers in Flanders, Belgium. The investigations confirm that a small battery of Toxkit microbiotests is a suitable tool for low cost routine ecotoxicity evaluation of contaminated river sediments.

A brief review and critical evaluation of the status of microbiotests

A review is given on some of the current trends in the field of alternative, small-scale aquatic toxicity tests. Examples of recently developed microbiotests with bacteria, algae and invertebrates are used to illustrate potential applications and short-comings of some of these assays. The major drawback of the majority of new microbiotests is the lack of published data on various aspects of their test development and application possibilities. Consequently many of these tests do not receive the regulatory recognition which they may deserve. It is concluded that for most microbiotests further research and test evaluation is needed before they will gain widespread acceptance as valid alternatives to the currently used conventional test procedures.

Development of a bioavailability-based risk assessment approach for nickel in freshwater sediments

To assess nickel (Ni) toxicity and behavior in freshwater sediments, a large-scale laboratory and field sediment testing program was conducted. The program used an integrative testing strategy to generate scientifically based threshold values for Ni in sediments and to develop integrated equilibrium partitioning-based bioavailability models for assessing risks of Ni to benthic ecosystems. The sediment testing program was a multi-institutional collaboration that involved extensive laboratory testing, field validation of laboratory findings, characterization of Ni behavior in natural and laboratory conditions, and examination of solid phase Ni speciation in sediments. The laboratory testing initiative was conducted in 3 phases to satisfy the following objectives: 1) evaluate various methods for spiking sediments with Ni to optimize the relevance of sediment Ni exposures; 2) generate reliable ecotoxicity data by conducting standardized chronic ecotoxicity tests using 9 benthic species in sediments with low and high Ni binding capacity; and, 3) examine sediment bioavailability relationships by conducting chronic ecotoxicity testing in sediments that showed broad ranges of acid volatile sulfides, organic C, and Fe. A subset of 6 Ni-spiked sediments was deployed in the field to examine benthic colonization and community effects. The sediment testing program yielded a broad, high quality data set that was used to develop a Species Sensitivity Distribution for benthic organisms in various sediment types, a reasonable worst case predicted no-effect concentration for Ni in sediment (PNECsediment ), and predictive models for bioavailability and toxicity of Ni in freshwater sediments. A bioavailability-based approach was developed using the ecotoxicity data and bioavailability models generated through the research program. The tiered approach can be used to fulfill the outstanding obligations under the European Union (EU) Existing Substances Risk Assessment, EU Registration, Evaluation, Authorisation, and Regulation of Chemicals (REACH), and other global regulatory initiatives. Integr Environ Assess Manag 2016;12:735-746.

Selection of bioassays for sediment toxicity screening

A large monitoring study of 80 freshwater sediments, using the TRIAD approach, was conducted in Flanders, Belgium using a battery of microbiotests and conventional assays. The test battery covered several phylogenenic groups and included acute or short-term chronic tests on the sediments’ porewater with bacteria (Vibrio fischeri), algae (Raphidocelis subcapitata), crustaceans (Thamnocephalus platyurus and Daphnia magna) and fish (Clarias gariepinus). Whole sediment tests with Hyalella azteca and Chironomus riparius were conducted concurrently. Uni- and multivariate statistical techniques were used to determine the discriminatory power, the toxicity detection capacity and the redundancy of the different assays. A battery composed of a minimal set of porewater and whole sediment assays is proposed for the initial toxicity screening of contaminated sediments.

The toxicity identification of inorganic toxicants in real world samples

The toxicity of a sediment pore water and an effluent was characterized using Toxicity Identification Evaluation (TIE) procedures. Both samples exhibited acute toxicity to the freshwater crustacean Thamnocephalus platyurus. The TIE approach was conducted using an enlarged battery of fractionation tests. Toxicity of the pore water sample was removed or reduced significantly by the cation exchange procedure and the air-stripping test at pH 11. Additionally, reduced toxicity was found at a reduced pH. Based on this TIE study and chemical analysis, ammonia was identified as the main toxic agent. Toxicity of the effluent sample was reduced significantly by the anion exchange resin. Additionally, an increased toxicity was found at a decreased pH. It was concluded from this TIE study and chemical analysis of the effluent that metal chromium was the causative toxicant.