Particle balance and return loops for microplastics in a tertiary-level wastewater treatment plant.

Microplastics (MPs) from households, stormwater, and various industries are transported to wastewater treatment plants (WWTPs), where a high proportion of them are captured before discharging their residuals to watersheds. Although recent studies have indicated that the removed MPs are mainly retained in wastewater sludge, sludge treatment processes have gained less attention in MP research than water streams at primary, secondary, and tertiary treatments. In this study, we sampled 12 different process steps in a tertiary-level municipal WWTP in central Finland. Our results showed that, compared to the plant influent load, three times more MPs circulated via reject water from the sludge centrifugation back to the beginning of the treatment process. Fibrous MPs were especially abundant in the dewatered sludge, whereas fragment-like MPs were observed in an aqueous stream. We concluded that, compared to the tertiary effluent, sludge treatment is the major exit route for MPs into the environment, but sludge treatment is also a return loop to the beginning of the process. Our sampling campaign also demonstrated that WWTPs with varying hydraulic conditions (such as the one studied here) benefit from disc filter-based tertiary treatments in MP removal.

Optical Monitoring of Microplastics Filtrated from Wastewater Sludge and Suspended in Ethanol.

The abundance of microplastics (MPs) in the atmosphere, on land, and especially in water bodies is well acknowledged. In this study, we establish an optical method based on three different techniques, namely, specular reflection to probe the medium, transmission spectroscopy measurements for the detection and identification, and a speckle pattern for monitoring the sedimentation of MPs filtrated from wastewater sludge and suspended in ethanol. We used first Raman measurements to estimate the presence and types of different MPs in wastewater sludge samples. We also used microscopy to identify the shapes of the main MPs. This allowed us to create a teaching set of samples to be characterized with our optical method. With the developed method, we clearly show that MPs from common plastics, such as polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and polyethylene (PE), are present in wastewater sludge and can be identified. Additionally, the results also indicate that the density of the plastics, which influences the sedimentation, is an essential parameter to consider in optical detection of microplastics in complex natural environments. All of the methods are in good agreement, thus validating the optics-based solution.

Sulfate toxicity to early life stages of European whitefish (Coregonus lavaretus) in soft freshwater.

Sulfate occurs naturally in the aquatic environment but its elevated levels can be toxic to aquatic life in freshwater environments. We investigated the toxicity of sulfate in humic, soft freshwater to whitefish (Coregonus lavaretus) from fertilization of eggs to hatching i.e. during the critical phases of whitefish early development. Anadromous Kokemäenjoki whitefish eggs and sperm during fertilization, embryos and larvae were exposed in the long-term 175-day incubation to seven different sodium sulfate (Na2SO4) concentrations from 44 to 2 000 mg SO4 L-1. Endpoint variables were the fertilization success, offspring survival and larval growth. Egg fertilization and early embryonic development were the most sensitive developmental stages of whitefish to sulfate, although the fertilization success and survival of embryos decreased only in the highest concentration of 2 000 mg SO4 L-1. The survival during late embryonic period, hatching and the 5-day larval period was high and no difference between the control and sulfate treatments were observed. LC50-values of sulfate for early embryonic period and for the entire embryonic and larval period was 1 413 and 1 161 mg L-1, respectively. The NOEC (No-observed Effect Concentration) of sulfate for the both periods was 1 207 mg L-1. The tolerance of whitefish early stages to sulfate toxicity seems to be on the same level as the tolerance of other salmonids' early stages.

Condition and Sperm Characteristics of Perch Perca fluviatilis inhabiting Boreal Lakes Receiving Metal Mining Effluents.

One of the world's largest, but low-grade, sulfide nickel deposits in northeastern Finland has been exploited by a bioheapleaching technology since 2008. Bioheapleaching is a relatively new, cost-effective technology, but humid climate, e.g., in boreal temperate environments, causes challenges to the management of the water balance in the ore heaps with wide catchment area, and the mining effluents have caused substantial metal and salting contamination of the receiving waterbodies. In our study, the impacts of metal-extracting bioheapleaching mine effluents on muscle and liver element concentrations, body condition, liver and testes mass, and sperm count and motility of male perch Perca fluviatilis were analysed. Liver, testes, and carcass mass of perch in relation to their length were lower in the mining-impacted lakes than in the reference lake, which may be due to the metal contamination, food availability, and energy demand under multistressor conditions. The sperm counts of the males in the mining-impacted lakes were lower, but the endurance of their sperm motility was longer than the endurance of sperm of the reference males. These findings suggested that the condition and sperm characteristics of perch were altered in lakes receiving metal mining effluents. Measured variables seem to be useful indicators for metal mining impacts on freshwater fish but only if high natural variation in these characteristics can be controlled by multiyear monitoring scheme.

Ecotoxicity assessment of boreal lake sediments affected by metal mining: Sediment quality triad approach complemented with metal bioavailability and body residue studies.

There are several methods for studying metal-contaminated freshwater sediments, but more information is needed on which methods to include in ecological risk assessment. In this study, we compliment the traditional Sediment Quality Triad (SQT) approach - including information on chemistry, toxicity and ecological status - with studies on metal bioavailability and metal body residues in local organisms. We studied four mining-affected boreal lakes in Finland by conducting chemical analyses of sediment and water, toxicity tests (L. variegatus, V. fischeri, C. riparius, L. stagnalis), and analysis of benthic organism community structure. In addition, we studied the relationships between metal loading, toxicity, metal bioavailability, and metal body residues in the field-collected biota. Chemistry and benthic organism community structures show adverse effects in those lakes, where the metal concentrations are the highest. However, toxicity was connected to low sediment pH during the experiment, rather than to high metal concentrations. Toxicity was observed in 4 out of 6 toxicity tests including growth test with L. variegatus, bulk sediment test with V. fischeri, and the L. stagnalis toxicity test. The C. riparius test did not show toxicity. Metal body residues in biota were not high enough to induce adverse effects (0.1-4.1 mg Cu/kg fw, 0.01-0.3 mg Ni/kg fw, 2.9-26.7 mg Zn/kg fw and 0.01-0.7 mg As/kg fw). Chemical analyses, metal bioavailability assessment and benthic community structures survey revealed adverse effects in the sediments, where metal concentrations are highest (Lake SJ and Lake KS). Standard toxicity tests were not suitable for studying acid, sulfide-rich sediments and, therefore, benthic structure study and chemical analyses are believed to give more reliable results of the ecological status of these sediments.

Assessment of Fish Embryo Survival and Growth by In Situ Incubation in Acidic Boreal Streams Undergoing Biomining Effluents.

The applicability of an in situ incubation method in monitoring the effects of metal mining on early life stages of fish was evaluated by investigating the impacts of a biomining technology utilizing mine on the mortality, growth, and yolk consumption of brown trout (Salmo trutta) and whitefish (Coregonus lavaretus) embryos. Newly fertilized eggs were incubated from autumn 2014 to spring 2015 in six streams under the influence of the mine located in North-Eastern Finland and in six reference streams. Although the impacted streams clearly had elevated concentrations of several metals and sulfate, the embryonic mortality of the two species did not differ between the impacted and the reference streams. Instead, particle accumulation to some cylinders had a significant impact on the embryonic mortality of both species. In clean cylinders, mortality was higher in streams with lower minimum pH. However, low pH levels were evident in both the reference and the mine-impacted groups. The embryonic growth of neither species was impacted by the mining activities, and the growth and yolk consumption of the embryos was mainly regulated by water temperature. Surprisingly, whitefish embryos incubated in streams with lower minimum pH had larger body size. In general, the applied in situ method is applicable in boreal streams for environmental assessment and monitoring, although in our study, we did not observe a specific mining impact differing from the effects of other environmental factors related to catchment characteristics.

Lumbriculus variegatus (Annelida) biological responses and sediment sequential extractions indicate ecotoxicity of lake sediments contaminated by biomining.

We assessed potential ecotoxicity of lake sediments affected by biomining effluents in northeastern Finland. Growth, reproduction and behavior of the sediment-dwelling oligochaete Lumbriculus variegatus (Müller 1774) were used as ecotoxicity endpoints. Standardized chronic bioassays were used for growth and reproduction, and acute and chronic tests with Multispecies Freshwater Biomonitor (MFB) for behavior assessments. Sequential extractions were used to characterize metal bioavailability and exposure conditions in the sediments, which indicated mining-induced contamination gradients of S, Cu, Ni and U and also bioavailability gradients of S and Ni. Among the ecotoxicity endpoints, growth and reproduction responses of the standard bioassays appeared more sensitive than the behavioral responses at 21 d. In the two most mining-affected test sediments, mean number of worms and dry biomass decreased 35-42% and 46-51% in comparison to the reference sediment, respectively. The behavioral changes of worms, i.e. peristaltic and overall locomotory activity, decreased on average 20-70% and 2-61% at 21 d in the same sediments. However, these behavioral changes were observed at the onset of exposure indicating MFB technique is a suitable and rapid screening level ecotoxicity assessment tool.

Toxicity of biomining effluents to Daphnia magna: Acute toxicity and transcriptomic biomarkers.

Increasing metal consumption is driving the introduction of new techniques such as biomining to exploit low grade ores. The biomining impacts notably aquatic ecosystems, yet, the applicability of ecotoxicological tests to study the complex mixture effects of mining waters is insufficiently understood. The aim of the present work was to test if transcriptomic biomarkers are suitable and sensitive for the ecotoxicity assessment of biomining affected waters. The study site had been affected by a multimetal biomine, and the studied water samples formed a concentration gradient of contamination downstream from the biomining site. Cadmium and nickel were used as positive controls in the toxicity tests. Selected transcriptomic biomarkers, previously shown to be differentially regulated by metals, were used to evaluate the ecotoxicity of the water samples. Parallel samples were used to compare the transcriptomic biomarkers with the conventional acute D. magna toxicity test. In the acute test, one sample was acutely toxic to D. magna, when pH was adjusted according to the standard, whereas, in the native pH, three samples caused total immobility. Monooxygenase was up-regulated by the highest concentration of Cd in control samples and three of the water samples. Vtg-SOD was up-regulated by one of the water samples, and catalase by the second highest concentration of Cd. The results show that transcriptomic biomarkers in D. magna can be used as sensitive bioindicators for metal mixture toxicity assessment in complex environmental water samples.

Assessing ecotoxicity of biomining effluents in stream ecosystems by in situ invertebrate bioassays: A case study in Talvivaara, Finland.

Mining of sulfide-rich pyritic ores produces acid mine drainage waters and has induced major ecological problems in aquatic ecosystems worldwide. Biomining utilizes microbes to extract metals from the ore, and it has been suggested as a new sustainable way to produce metals. However, little is known of the potential ecotoxicological effects of biomining. In the present study, biomining impacts were assessed using survival and behavioral responses of aquatic macroinvertebrates at in situ exposures in streams. The authors used an impedance conversion technique to measure quantitatively in situ behavioral responses of larvae of the regionally common mayfly, Heptagenia dalecarlica, to discharges from the Talvivaara mine (Sotkamo, Northern Finland), which uses a biomining technique. Behavioral responses measured in 3 mine-impacted streams were compared with those measured in 3 reference streams. In addition, 3-d survival of the mayfly larvae and the oligochaete Lumbriculus variegatus was measured in the study sites. Biomining impacts on stream water quality included increased concentrations of sulfur, sulfate, and metals, especially manganese, cadmium, zinc, sodium, and calcium. Survival of the invertebrates in the short term was not affected by the mine effluents. In contrast, apparent behavioral changes in mayfly larvae were detected, but these responses were not consistent among sites, which may reflect differing natural water chemistry of the study sites. Environ Toxicol Chem 2017;36:147-155. © 2016 SETAC.

Tolerance of whitefish (Coregonus lavaretus) early life stages to manganese sulfate is affected by the parents.

European whitefish (Coregonus lavaretus) embryos and larvae were exposed to 6 different manganese sulfate (MnSO4 ) concentrations from fertilization to the 3-d-old larvae. The fertilization success, offspring survival, larval growth, yolk consumption, embryonic and larval Mn tissue concentrations, and transcript levels of detoxification-related genes were measured in the long-term incubation. A full factorial breeding design (4 females × 2 males) allowed examination of the significance of both female and male effects, as well as female-male interactions in conjunction with the MnSO4 exposure in terms of the observed endpoints. The MnSO4 exposure reduced the survival of the whitefish early life stages. The offspring MnSO4 tolerance also was affected by the female parent, and the female-specific mean lethal concentrations (LC50s) varied from 42.0 mg MnSO4 /L to 84.6 mg MnSO4 /L. The larval yolk consumption seemed slightly inhibited at the exposure concentration of 41.8 mg MnSO4 /L. The MnSO4 exposure caused a significant induction of metallothionein-A (mt-a) and metallothionein-B (mt-b) in the 3-d-old larvae, and at the exposure concentration of 41.8 mg MnSO4 /L the mean larval mt-a and mt-b expressions were 47.5% and 56.6% higher, respectively, than at the control treatment. These results illustrate that whitefish reproduction can be impaired in waterbodies that receive Mn and SO4 in concentrations substantially above the typical levels in boreal freshwaters, but the offspring tolerance can be significantly affected by the parents and in particular the female parent. Environ Toxicol Chem 2017;36:1343-1353. © 2016 SETAC.

Weight-of-evidence approach in assessment of ecotoxicological risks of acid sulphate soils in the Baltic Sea river estuaries.

Acidity and leaching of metals from acid sulphate soils (ASSs) impair the water quality of receiving surface waters. The largest ASS areas in Europe are found in the coasts of the northern Baltic Sea. We used weight-of-evidence (WoE) approach to assess potential risks in 14 estuary sites affected by ASS in the Gulf of Finland, northern Baltic Sea. The assessment was based on exposure and effect profiles utilizing sediment and water metal concentrations and concurrent pH variation, sediment toxicity tests using the luminescent bacterium Vibrio fischeri and the midge Chironomus riparius, and the ecological status of benthic macroinvertebrate communities. Sediment metal concentrations were compared to national sediment quality criteria/guidelines, and water metal concentrations to environmental quality standards (EQSs). Hazard quotients (HQs) were established for maximum aluminium, cadmium and zinc concentrations at low pH based on applicable US EPA toxicity database. Sediment metal concentrations were clearly elevated in most of the studied estuaries. The EQS of cadmium (0.1 µg/l) was exceeded in 3 estuaries out of 14. The pH-minima were below the national threshold value (5.5) between good and satisfactory water quality in 10 estuaries. V. fischeri bioluminescence indicated toxicity of the sediments but toxic response was not observed in the C. riparius emergence test. Benthic invertebrate communities were deteriorated in 6 out of 14 sites based on the benthic invertebrate quality index. The overall ecotoxicological risk was assessed as low in five, moderate in three and high in five of the estuary sites. The risk assessment utilizing the WoE approach indicated that harmful effects of ASSs are likely to occur in the Baltic Sea river estuaries located at the ASS hotspot area.

Estimated intake levels for Finnish children of methylmercury from fish.

Methylmercury (MeHg) is a well-known neurotoxic agent, and consumption of contaminated fish is the principal environmental source of MeHg exposure in humans. Children are more susceptible to adverse effects than adults. No previous specific data exist for intake by Finnish children of methylmercury from fish. We estimated fish consumption and MeHg intakes from species most commonly consumed by Finnish children aged 1-6 years. The total mercury concentrations were determined in fish species consumed, and age-specific methylmercury intakes were derived. We also examined safety margins and the proportion of children exceeding the tolerable daily intakes set by international expert bodies. The daily intake of MeHg ranged from 0 to 0.33 µg/kg bw. The strictest reference value 0.1 µg/kg bw/day for MeHg, proposed by USEPA, was exceeded by 1-15% of the study population, and FAO/WHO JECFA provisional tolerable weekly intake of 1.6 µg/kg bw was exceeded by 1% of boys and 2.5% of girls aged 6 years. Intakes of 1-year old girls were higher than of boys, whereas for 3-year olds they were the opposite. The highest intakes were observed for 6-year-old boys and girls. There was great variation in the estimated MeHg intakes among Finnish children.

Long-term daily intake estimates of polychlorinated dibenzo-p-dioxins and furans, polychlorinated biphenyls and polybrominated diphenylethers from food in Finnish children: risk assessment implications.

Food is contaminated by polychlorinated dibenzo-p-dioxins and furans (PCDD/F), polychlorinated biphenyls (PCB) and polybrominated diphenylethers (PBDE) worldwide. Previous data show elevated intakes in children. We determined intakes of POPs in Finnish children. Because no children-specific safe limit values exist, we used tolerable daily intakes (TDIs) set for adults by international expert bodies to examine the proportion of the study population that exceed those limits. We utilised dietary monitoring data with food consumption of Finnish boys and girls aged 1-6 years, measured the contaminant concentrations in all the main food items and calculated age-specific contaminant sum and congener-specific long-term daily intake levels. Our food intake and contaminant data correspond to years 2002-2005. The long-term upper-bound dioxin intakes ranged between 0.1 and 12.8 pg WHO(PCDD/F-PCB)-TEQ/kg bw/d (min and max). An immediate TDI for WHO(PCDD/F-PCB)-TEQs of 4.0 pg/kg bw/d were exceeded by 2.5%-7.5% of the children. PBDE long-term upper-bound intake was between 0.1 and 5.8 ng/kg bw/d (min and max). Congener-specific analyses indicated a typical Finnish adult exposure pattern of the children to PCDD/Fs, PCBs and PBDEs. The highest POP intakes were observed in children aged 3 years. Long-term daily PCDD/F, PCB and PBDE intakes among Finnish children varied greatly between individuals and ages. In each age group of the study population, there was a proportion of children with their WHO(PCDD/F-PCB)-TEQ intake exceeding considered safe limits set for adults. Based on the exposure profile reported herein, children should be clearly considered as a specific sub-population in food-mediated contaminant risk assessment.