Investigating predictive tools for refinery effluent hazard assessment using stream mesocosms.

Hazard assessment of refinery effluents is challenging because of their compositional complexity. Therefore, a weight-of-evidence approach using a combination of tools is often required. Previous research has focused on several predictive tools for sophisticated chemical analyses: biomimetic extraction to quantify the potentially bioaccumulative substances, 2-dimensional gas chromatography, modeling approaches to link oil composition to toxicity (PETROTOX), and whole-effluent toxicity assessments using bioassays. The present study investigated the value of these tools by comparing predicted effects to actual effects observed in stream mesocosm toxicity studies with refinery effluents. Three different effluent samples, with and without fortification by neat petroleum substances, were tested in experimental freshwater streams. The results indicate that the biological community shifted at higher exposure levels, consistent with chronic toxicity effects predicted by both modeled toxic units and potentially bioaccumulative substance measurements. The present study has demonstrated the potential of the predictive tools and the robustness of the stream mesocosm design to improve our understanding of the environmental hazards posed by refinery effluents. Environ Toxicol Chem 2019;38:650-659. © 2018 SETAC.

Effects of Seven Fungicides on Non-Target Aquatic Fungi.

Aquatic risk assessments for fungicides are carried out without information on their toxicity to non-target aquatic fungi. This might cause an underestimation of the toxic effects to the aquatic fungal community. This study focuses on the question whether recently derived concentrations limits for fungicides considered to protect populations of primary producers and (in)vertebrates also do protect the aquatic fungi. A panel of fungal species and Oomycetes was isolated and identified from unpolluted surface waters in the Netherlands. Toxicity tests were used to determine effects of seven fungicides with different modes of actions. For the triazoles epoxiconazole and tebuconazole, the chronic lowest observable effect concentration was lower than the regulatory acceptable concentration based on acute HC5 values.

Impact of biodegradation on the potential bioaccumulation and toxicity of refinery effluents.

Whole effluent assessments (WEA) are being investigated as potential tools for controlling aqueous industrial discharges and minimizing environmental impact. The present study investigated how toxicity and the presence of potentially bioaccumulative substances altered when refinery effluents were subjected to biodegradation tests. Three petrochemical effluents were assessed, two freshwater and one saline, and subjected to two different types of biodegradation tests, resembling either a ready style (dissolved organic carbon (DOC)-die away) or an inherent style (Zahn-Wellens) test and the toxicity and potential to bioaccumulate parameters were re-analysed during and after biodegradation. A high proportion of the potentially bioaccumulative substances (PBS) in these effluents was easily biodegradable. Biodegradation not only lowered the PBS concentration but also toxicity. Appropriate controls are required however, as some increases in toxicity were observed after 4 h. In the present study, six other petrochemical effluents were also assessed for their PBS content and toxicity to increase the understanding of the relationship between PBS and toxicity. The results showed that the PBS concentrations in these samples were lower than the estimated benchmarks of acute toxicity for algae, fish and crustacean, although two samples were above the critical PBS values for chronic narcotic toxicity for Daphnia magna, which support the assumption that narcotic effects are mainly responsible for the observed toxicity in refinery effluents. It can be concluded that for facilities processing petroleum products that the measurement of PBS is a suitable surrogate for toxicity tests at the screening stage. Finally, the combination of persistency, bioaccumulation, and toxicity tests was shown to have additional value compared to an approach using only toxicity tests.

Sediment toxicity of a rapidly biodegrading nonionic surfactant: Comparing the equilibrium partitioning approach with measurements in pore water.

The equilibrium partitioning theory (EqP) assumes that the toxicity of nonionic surfactants in sediment can be predicted from water-only toxicity data as long as the effect concentrations are properly normalized for chemical activity. Therefore, in marine sediment toxicity tests with the model alcohol ethoxylate (AE), C12EO8, freely dissolved concentrations were both measured via solid-phase microextraction and predicted using sorption coefficients. In fully equilibrated test systems (including the overlying water), both methods showed that concentrations in the pore water of the spiked sediment layer causing 50% mortality (LC50) to the amphipod Corophium volutator were in the same range as LC50 values for amphipods exposed to AE in seawater only. In the sediment systems, AE concentrations in the pore water remained constant up to 15 days, while concentrations in the water overlying the sediment decreased to less than 1% of initial concentrations within 6 days due to biodegradation. In such disequilibrated test systems, C. volutator survived pore water dissolved concentrations that were above the LC50. Apparently, this burrowing amphipod is able to exploit the low chemical activity in the overlying water as a refuge from sediment exposure.

A chronic bioassay with the estuarine amphipod Corophium volutator: test method description and confounding factors.

Methods of conducting a chronic sediment toxicity test with the estuarine amphipod Corophium volutator are described. They consist of a 49-day exposure, after which mortality, growth and reproduction are determined. Pilot experiments were used to optimize test design parameters such as temperature, duration, feeding and refreshing regimes, and effects of indigenous organisms. By way of further validation, the present study focused on the effects of four different parameters: oxygen saturation, salinity, ammonium and nitrite. These confounding factors might play an important role especially if the test is used for risk assessment of field-contaminated sediments. It is concluded that the present experimental design is well suited for chronic sediment exposures with C. volutator. The test can be performed at a broad range of salinity values, provided that controls are performed at the same salinity. Results further demonstrate that with the endpoints growth and reproduction this chronic test procedure is a factor 7-18 more sensitive to ammonium and nitrate than the standardized acute bioassay (endpoint mortality).

Ammonium toxicity at high pH in a marine bioassay using Corophium volutator.

Two forms of ammonium exist in water: un-ionized ammonia NH3 and ionized ammonium NH4+. The toxicity to many aquatic organisms is primarily attributed to the NH3 (un-ionized) species, with the NH4+ ion (ionized) species being relatively less toxic. The pH level influences the degree of ionization. It is therefore very important that quality criteria be derived for total ammonium levels at several pH values in order to allow correct interpretation of the sediment bioassay with Corophium volutator. The responses of Corophium to total ammonium were studied in a series of pH-controlled experiments. The LC50 of total ammonium showed a significant decrease with increasing pH, in both water-only and sediment experiments. The results indicated a combined NH4+ and NH3 toxicity at pH levels less than 8.3. The results can be used to set pH-dependent water quality criteria for total ammonium in overlying water in a 10-day sediment bioassay with Corophium volutator.

Tenax extraction mimics benthic and terrestrial bioavailability of organic compounds.

Biota to sediment accumulation factors (BSAFs) are widely used to describe the potential accumulation of organic contaminants in organisms. From field studies it is known that these BSAFs can vary dramatically between sediments of different origin, which is possibly explained by the variation in bioavailability of organic contaminants in sediments. In the present study it is shown that the variability in BSAF values for different sediment samples obtained at two Dutch freshwater sites could largely be explained by the variation in Tenax-extractable concentrations in these sediments. Variations of a factor of about 50 could be explained. The ratio between concentrations in biota and Tenax-extractable concentrations in sediment varied slightly between sediments and contaminant class, but was close to the theoretically expected value of 2. This is a strong indication that Tenax-extractable concentrations of contaminants in sediments are an excellent indicator of available concentrations.

Using marine bioassays to classify the toxicity of Dutch harbor sediments.

A procedure was developed to assess contaminated marine sediments from Dutch harbors for possible adverse biological effects using three laboratory bioassays: A 10-d survival test with the amphipod Corophium volutator, a 14-d survival test with the heart urchin Echinocardium cordatum (adults), and the bioluminescence inhibition test with the bacterium Vibrio fischeri (Microtox solid phase test LSP]). Microtox results were mathematically corrected for the modifying influence of fine sediment particles. After a validation procedure on test performance and modifying factors, respectively, 81%, 99%, and 90% of the amphipod, heart urchin, and Microtox results were approved. Lower and upper threshold limits for biological effects were set at respectively 24 and 30% mortality for C. volutator, 27 and 35% mortality for E. cordatum, and 24 and 48 toxic units for the Microtox SP based on significant differences with control sediment and the performance of reference sediments. The bioassays clearly distinguished harbor sediments that give rise to acute effects and those that do not. Threshold limits for the amphipods, heart urchins, and bacteria were exceeded in, respectively, 9 to 17%, 33 to 40%, and 23 to 50% of the sediment samples. Highest effects were observed in sediments from the northerly harbors; there was significantly less response in sediments from the Delta Region and the port of Rotterdam (The Netherlands). The procedure outlined in this paper can be used for routine screening of contaminated dredged material that is proposed for open water disposal.