A preliminary study on the ecotoxic potency of wastewater treatment plant sludge combining passive sampling and bioassays.

Sewage sludge is an inevitable byproduct produced in wastewater treatment. Reusing nutrient-rich sludge will diminish the amount of waste ending in soil dumping areas and will promote circular economy. However, during sewage treatment process, several potentially harmful organic chemicals are retained in sludge, but proving the safety of processed sludge will promote its more extensive use in agriculture and landscaping. Environmental risk assessment of sludge requires new methods of characterizing its suitability for various circular economy applications. Bioavailable and bioaccessible fractions are key variables indicating leaching, transport, and bioaccumulation capacity. Also, sludge treatments have a significant effect on chemical status and resulting environmental risks. In this study, the concentrations of polyaromatic hydrocarbons (PAHs), triclosan (TCS), triclocarban (TCC), methyl triclosan (mTCS), and selected active pharmaceutical ingredients (APIs) were determined in different sludge treatments and fractions. Passive samplers were used to characterize the bioavailable and bioaccessible fractions, and the sampler extracts along the sludge and filtrate samples were utilized in the bioassays. The TCS and PAH concentrations did not decrease as the sludge was digested, but the contents diminished after composting. Also, mTCS concentration decreased after composting. The API concentrations were lower in digested sludge than in secondary sludge. Digested sludge was toxic for Aliivibrio fischeri, but after composting, toxicity was not observed. However, for Daphnia magna, passive sampler extracts of all sludge treatments were either acutely (immobility) or chronically (reproduction) toxic. Secondary and digested sludge sampler extracts were cytotoxic, and secondary sludge extract was also genotoxic. The measured chemical concentration levels did not explain the toxicity of the samples based on the reported toxicity thresholds. Bioassays and sampler extracts detecting bioavailable and bioaccessible contaminants in sludge are complementing tools for chemical analyses. Harmonization of these methodswill help establish scientifically sound regulative thresholds for the use of sludge in circular economy applications.

Assessing the influence of confounding biological factors when estimating bioaccumulation of PCBs with passive samplers in aquatic ecosystems.

Passive samplers are promising surrogates for organisms, mimicking bioaccumulation. However, several biological characteristics disturb the passive partitioning process in organisms by accelerating or restraining bioaccumulation, resulting in species-specific body residues of hydrophobic organic contaminants (HOCs). In addition to site-specific characteristics and HOC concentrations, age, sex, diet, biotransformation capability and habitat-specific characteristics may affect body residues. Two passive sampler types, polyethylene (PE) and polydimethylsiloxane (PDMS) were deployed in a PCB-contaminated freshwater lake water and sediment, respectively, to assess their bioaccumulation prediction capacity. In order to understand the importance of biological characteristics in the bioaccumulation process, we explored bioaccumulation in biota from plants and plankton to mussels and fish. The PCB concentrations in the PE sheet reflected the bioavailable concentration of PCBs slightly better than those in the PDMS samplers. Passive samplers were good predictors of PCB concentrations in fish, whereas concentrations in algae and invertebrates were overestimated. When comparing the measured concentrations in biota to the estimated concentrations using the PE samplers, the average regression slope was 0.87 for all biota and 1.22 for fish, and average modeling efficiency (EF) was 3.02 for all biota and 0.6 for fish. The best model performance was achieved for fish in trophic levels 3-4. Bioaccumulation was species-specific and dependent on the trophic level and diet. Closer examination revealed that metabolic capability changes during the life span, and source of nutrition determined the biomagnification of HOCs, which differed between the fish species. Thus, species composition and available prey selection compose a unique bioaccumulation scenario and the resulting body residues. Due to the existing variation in body residues derived from passive samplers, extrapolating the results from one to another ecosystem must be done with caution. Passive samplers, however, offer a very powerful tool for risk assessment on the ecosystem level.

Mixing and capping techniques for activated carbon based sediment remediation - Efficiency and adverse effects for Lumbriculus variegatus.

Activated carbon (AC) has been proven to be highly effective for the in-situ remediation of sediments contaminated with a wide range of hydrophobic organic contaminants (HOCs). However, adverse biological effects, especially to benthic organisms, can accompany this promising remediation potential. In this study, we compare both the remediation potential and the biological effects of several AC materials for two application methods: mixing with sediment (MIX) at doses of 0.1 and 1.0% based on sediment dw and thin layer capping (TLC) with 0.6 and 1.2 kg AC/m2. Significant dose dependent reductions in PCB bioaccumulation in Lumbriculus variegatus of 35-93% in MIX treatments were observed. Contaminant uptake in TLC treatments was reduced by up to 78% and differences between the two applied doses were small. Correspondingly, significant adverse effects were observed for L. variegatus whenever AC was present in the sediment. The lowest application dose of 0.1% AC in the MIX system reduced L. variegatus growth, and 1.0% AC led to a net loss of organism biomass. All TLC treatments let to a loss of biomass in the test organism. Furthermore, mortality was observed with 1.2 kg AC/m2 doses of pure AC for the TLC treatment. The addition of clay (Kaolinite) to the TLC treatments prevented mortality, but did not decrease the loss in biomass. While TLC treatments pose a less laborious alternative for AC amendments in the field, the results of this study show that it has lower remediation potential and could be more harmful to the benthic fauna.

Effects of activated carbon amended sediment on biological responses in Chironomus riparius multi-generation testing.

The biological effects of activated carbon (AC) amendments in sediments were studied with the midge Chironomus riparius. The effects on larvae growth were studied using three different AC particles sizes (PAC: 90% <63µm, MAC: ø 63-200µm and GAC: ø 420-1700µm). The long- term effects of MAC were studied in an emergence experiment over two generations (P, F1), together with larvae growth experiment over three generations (P, F1, F2). Retarded growth and development of the larvae were observed in the two smallest particle sizes (PAC and MAC), as well as morphological changes in the gut wall microvilli layer studied from transmission electron micrographs. In addition, at high AC treatments the larvae reaching fourth instar stage were of a smaller size compared to the controls. With PAC treatment AC amendment dosages higher than 1% of sediment dry weight induced mortality. In the emergence experiment there was an indication of a delay in F1 generation emergence. Male dry weight (dw) in P generation was significantly reduced in the 2.5% MAC treatment. The effects of AC amendments were more obvious in the C. riparius larvae compared to the effects seen in emerging adults exposed to AC-amended sediment during the larval stage.

Toxicity Testing of Silver Nanoparticles in Artificial and Natural Sediments Using the Benthic Organism Lumbriculus variegatus.

The increased use of silver nanoparticles (AgNP) in industrial and consumer products worldwide has resulted in their release to aquatic environments. Previous studies have mainly focused on the effects of AgNP on pelagic species, whereas few studies have assessed the risks to benthic invertebrates despite the fact that the sediments act as a large potential sink for NPs. In this study, the toxicity of sediment-associated AgNP was evaluated using the standard sediment toxicity test for chemicals provided by the Organization of Economic Cooperation and Development. The freshwater benthic oligochaete worm Lumbriculus variegatus was exposed to sediment-associated AgNP in artificial and natural sediments at concentrations ranging from 91 to 1098 mg Ag/kg sediment dry weight. Silver nitrate (AgNO3) was used as a reference compound for Ag toxicity. The measured end points of toxicity were mortality, reproduction, and total biomass. In addition, the impact of sediment-associated AgNP on the feeding rate of L. variegatus was studied in a similar test set-up as mentioned previously. The addition of AgNP into the sediment significantly affected the feeding rate and reproduction of the test species only at the highest concentration (1098 mg/kg) of Ag in the natural sediment with the lowest pH. In comparison, the addition of AgNO3 resulted in reproductive toxicity in every tested sediment, and Ag was more toxic when spiked as AgNO3 than AgNP. In general, sediments were observed to have a high capacity to eliminate the AgNP-derived toxicity. However, the capacity of sediments to eliminate the toxicity of Ag follows a different pattern when spiked as AgNP than AgNO3. The results of this study emphasize the importance of sediment-toxicity testing and the role of sediment properties when evaluating the environmental effects and behavior of AgNP in sediments.

Effects of Activated Carbon on PCB Bioaccumulation and Biological Responses of Chironomus riparius in Full Life Cycle Test.

The nonbiting midge Chironomus riparius was used to study the remediation potential and secondary effects of activated carbon (AC, ø 63-200 µm) in PCB contaminated sediments. AC amendments efficiently reduced PCB bioavailability determined by Chironomus riparius bioaccumulation tests and passive samplers. PCBs were shown to transfer from larvae to adults. Lower PCB concentrations were observed in adult midges emerging from AC amended compared to unamended sediments. Increased reproduction, survival, larval growth and gut wall microvilli length were observed with low AC dose (0.5% sediment dw) compared to unamended sediment, indicating an improved success of larvae in the sediment with low organic carbon content. On the other hand, higher AC doses (2.5% sediment dw) caused adverse effects on emergence and larval development. In addition, morphological changes in the gut wall microvilli layer were observed. This study showed that the secondary effects of AC amendments are dependent on the dose and the sediment characteristics. Metamorphic species, such as C. riparius, may act as a vector for organic pollutants from aquatic to terrestrial ecosystems and according to this study the AC amendments may reduce this transport.

Effects of activated carbon ageing in three PCB contaminated sediments: Sorption efficiency and secondary effects on Lumbriculus variegatus.

The sorption efficiency and possible secondary effects of activated carbon (AC) (ø 63-200 µm) was studied with Lumbriculus variegatus in three PCB contaminated sediments applying long AC-sediment contact time (3 years). AC amendment efficiently reduced PCB bioavailability as determined with both, L. variegatus bioaccumulation test and passive samplers. However, dose related secondary effects of AC on egestion rate and biomass were observed (applied doses 0.25% and 2.5% sediment dry weight). The sorption capacity and secondary effects remained similar when the experiments were repeated after three years of AC-sediment contact time. Further, transmission electron microscopy (TEM) samples revealed morphological changes in the L. variegatus gut wall microvilli layer. Sediment properties affected both sorption efficiency and secondary effects, but 2.5% AC addition had significant effects regardless of the sediment. In, conclusion, AC is an efficient and stable sorbent to decrease the bioavailability of PCBs. However, sediment dwelling organisms, such as Oligochaete worms in this study, may be sensitive to the carbon amendments. The secondary effects and possible morphological changes in benthic organisms should not be overlooked as in many cases they form the basis of the aquatic food webs.

Fate of polychlorinated biphenyls in a contaminated lake ecosystem: combining equilibrium passive sampling of sediment and water with total concentration measurements of biota.

Equilibrium sampling devices can be applied to study and monitor the exposure and fate of hydrophobic organic chemicals on a thermodynamic basis. They can be used to determine freely dissolved concentrations and chemical activity ratios and to predict equilibrium partitioning concentrations of hydrophobic organic chemicals in biota lipids. The authors' aim was to assess the equilibrium status of polychlorinated biphenyls (PCBs) in a contaminated lake ecosystem and along its discharge course using equilibrium sampling devices for measurements in sediment and water and by also analyzing biota. The authors used equilibrium sampling devices (silicone rubber and polyethylene [PE]) to determine freely dissolved concentrations and chemical activities of PCBs in the water column and sediment porewater and calculated for both phases the corresponding equilibrium concentrations and chemical activities in model lipids. Overall, the studied ecosystem appeared to be in disequilibrium for the studied phases: sediment, water, and biota. Chemical activities of PCBs were higher in sediment than in water, which implies that the sediment functioned as a partitioning source of PCBs and that net diffusion occurred from the sediment to the water column. Measured lipid-normalized PCB concentrations in biota were generally below equilibrium lipid concentrations relative to the sediment (CLip ⇌Sed ) or water (CLip ⇌W ), indicating that PCB levels in the organisms were below the maximum partitioning levels. The present study shows the application versatility of equilibrium sampling devices in the field and facilitates a thermodynamic understanding of exposure and fate of PCBs in a contaminated lake and its discharge course.

Sorptive capacity of membrane lipids, storage lipids, and proteins: a preliminary study of partitioning of organochlorines in lean fish from a PCB-contaminated freshwater lake.

Knowledge on the internal distribution of halogenated organic chemicals (HOCs) would improve our understanding of dose-effect relationships and subsequently improve risk assessment of contaminated sites. Herein, we determine the concentrations of HOCs based on equilibrium partitioning in storage lipids, membrane lipids, and proteins in field-contaminated fish using equilibrium sampling devices. The study shows the importance of protein as a sorptive phase in lean fish. Our results provide a basis for using species-specific equilibrium partitioning coefficients between sorptive tissues and fish internal water as a substitute for K(ow) in, for example, upgrading models that simulate food-chain accumulation of the chemical.

Trophic transfer of polychlorinated biphenyls (PCB) in a boreal lake ecosystem: testing of bioaccumulation models.

Understanding the fate of persistent organic chemicals in the environment is fundamental information for the successful protection of ecosystems and humans. A common dilemma in risk assessment is that monitoring data reveals contaminant concentrations in wildlife, while the source concentrations, route of uptake and acceptable source concentrations remain unsolved. To overcome this problem, different models have been developed in order to obtain more precise risk estimates for the food webs. However, there is still an urgent need for studies combining modelled and measured data in order to verify the functionality of the models. Studies utilising field-collected data covering entire food webs are particularly scarce. This study aims to contribute to tackling this problem by determining the validity of two bioaccumulation models, BIOv1.22 and AQUAWEBv1.2, for application to a multispecies aquatic food web. A small boreal lake, Lake Kernaalanjärvi, in Finland was investigated for its food web structure and concentrations of PCBs in all trophic levels. Trophic magnification factors (TMFs) were used to measure the bioaccumulation potential of PCBs, and the site-specific environmental parameters were used to compare predicted and observed concentrations. Site-specific concentrations in sediment pore water did not affect the modelling endpoints, but accurate site-specific measurements of freely dissolved concentrations in water turned out to be crucial for obtaining realistic model-predicted concentrations in biota. Numerous parameters and snapshot values affected the model performances, bringing uncertainty into the process and results, but overall, the models worked well for a small boreal lake ecosystem. We suggest that these models can be optimised for different ecosystems and can be useful tools for estimating the bioaccumulation and environmental fate of PCBs.

Pentachlorophenol (PCP) bioaccumulation and effect on heat production on salmon eggs at different stages of development.

In this study, pentachlorophenol (PCP) bioaccumulation and its effect on heat dissipation was studied in eggs of the lake salmon (Salmo salar m. sebago). In bioaccumulation studies, the eggs were exposed to low concentrations (0.051-0.056 micromol/l, 13.583-14.915) of waterborne [14C]-labeled PCP at two developmental stages: (1) 3 weeks after fertilization, and (2) just before hatching. The effect of PCP on egg heat dissipation was measured by a microcalorimeter after exposing the eggs to gradual concentrations (0-0.992 micromol/l) of PCP for 48 h. After both the bioaccumulation and heat dissipation experiments, the eggs were dissected and the concentrations of PCP in tissue were determined separately for eggshell, yolk and embryo. The bioaccumulation studies showed that PCP accumulates more in the eggs at the late developmental stage. Bioconcentration factors (BCF) for different tissues were 3-42 times higher for the eggs at the late developmental stage compared with the eggs that were incubated only for 3 weeks. In early developmental stage, the eggshell adsorbs a large portion of the chemical. In late developmental stage, the actual embryo accumulated both proportionately and totally more than other dissected tissues in the beginning of the exposure, but eventually the yolk accumulated highest total amount of the chemical. A probable reason for the higher PCP body burden in the late developmental stage is that the respiration rate and metabolic activity of the embryo increases as it grows. The salmon eggs responded to an exposure to PCP with an elevated rate of heat dissipation. The threshold concentration above which the embryo heat dissipation was amplified was 29.64 micromol/kg embryo wet weight (ww) or 0.28 micromol/l. The highest embryo heat production was measured at the exposure concentration of 0.992 micromol/l. At higher exposure concentrations the heat dissipation decreased. The basic findings of the study are that PCP accumulates in growing embryonic tissue and is able to change the physiology of developing embryo.

Bioaccumulation and toxicity of sediment associated herbicides (ioxynil, pendimethalin, and bentazone) in Lumbriculus variegatus (Oligochaeta) and Chironomus riparius (Insecta).

The benthic macroinvertebrates Lumbriculus variegatus and Chironomus riparius were used in toxicity and bioaccumulation tests to determine the toxic concentrations and accumulation potential of sediment associated herbicides. The tested chemicals were ioxynil, bentazone, and pendimethalin. The bioaccumulation tests with L. variegatus were performed in four different sediments, each having different characteristics. Water-only LC(50) tests were performed with both L. variegatus and C. riparius. A sublethal effect of model compounds in sediments was assessed by a C. riparius larvae growth-inhibition test. Of the model compounds, ioxynil appeared to be the most toxic, with LC(50) values 1.79 and 2.79 mgL(-1) for L. variegatus and C. riparius, respectively. The LC(50) water concentrations for bentazone were 79.11 and 62.31 mgL(-1) for L. variegatus and C. riparius, respectively. Similarly, ioxynil revealed the highest bioaccumulation potential in bioaccumulation tests. The most important characters affecting chemical fate in the sediment seemed to be the organic matter content and the particle size fraction. The sediments with low organic material and coarse particle size consistently showed high bioaccumulation potential and vice versa. In C. riparius growth tests bentazone had a statistically significant effect on larval growth at sediment concentrations of 1160 and 4650 mgkg(-1) (P<0.05). It is noteworthy that standard deviations tend to be greater at high chemical concentrations, which addresses the fact that part of the individuals started to suffer. Ioxynil had an effect on the larval growth in other test sediment at the highest concentration (15.46 mgkg(-1)dw), in which head capsule length correlated with larval weight, decreasing toward higher exposure concentrations. The current results show the importance of sediment organic matter as a binding site of xenobiotics.