Short-term Laboratory Experiments Research Articles

Coastal inundation regime moderates the short-term effects of sediment and soil additions on seawater oxygen and greenhouse gas dynamics: a microcosm experiment

The frequency and persistence of tidal inundation varies along the coastal terrestrial-aquatic interface, from frequently inundated wetlands to rarely inundated upland forests. This inundation gradient controls soil and sediment biogeochemistry and influence the exchange of soils and sediments from terrestrial to aquatic domains. Although a rich literature exist on studies of the influence of tidal waters on the biogeochemistry of coastal ecosystem soils, few studies have experimentally addressed the reverse question: How do soils (or sediments) from different coastal ecosystems influence the biogeochemistry of the tidal waters that inundate them? To better understand initial responses of coastal waters that flood coastal wetlands and uplands, we conducted short-term laboratory experiments where seawater was amended with sediments and soils collected across regional gradients of inundation exposure (i.e., frequently to rarely inundated) for 14 sites across the Mid-Atlantic, USA. Measured changes in dissolved oxygen and greenhouse gas concentrations were used to calculate gas consumption or production rates occurring during seawater exposure to terrestrial materials. We also measured soil and water physical and chemical properties to explore potential drivers. We observed higher oxygen consumption rates for seawater incubated with soils/sediments from frequently inundated locations and higher carbon dioxide production for seawater incubated with soils from rarely inundated transect locations. Incubations with soil from rarely inundated sites produced the highest global warming potential, primarily driven by carbon dioxide and secondarily by nitrous oxide. We also found environmental drivers of gas rates varied notably between transect locations. Our findings indicate that seawater responses to soil and sediment inputs across coastal terrestrial-aquatic interfaces exhibit some consistent patterns and high intra- and inter-site variability, suggesting potential biogeochemical feedback loops as inundation regimes shift inland.

Testing countermeasures to reduce 90Sr content in fish products

Activity concentrations of 90Sr in fish in lakes located within the Chornobyl Exclusion Zone (ChEZ) reach 100 kBq kg−1, which is several thousand times higher than the permissible level in Ukraine (35 Bq kg−1). This study was conducted in the natural conditions of the ChEZ to determine the effectiveness of keeping radioactively contaminated fish in “clean” water to reduce the 90Sr content of their muscle tissue, as previously shown in short-term laboratory experiments. It was found that transferring tench (Tinca tinca (Linnaeus, 1758)) from Lake Glubokoye one of the most contaminated lakes in the ChEZ, to a cage in the “clean” Lake Starukha for 45 days did not lead to a significant decrease in 90Sr content in both bone and muscle tissues.Establishing permissible levels of 90Sr concentration only in fish fillet, and not in the whole fish body (with bone tissue), is appropriate for human radiation protection, since the retention factors of 90Sr treatment for boiled bone tissue of crucian carp from the Chornobyl exclusion zone are less than 0.01, and up to 97% of strontium is contained in bone tissue.

Evaluation of Siderophore Production by Different Promising Microbial Isolates

Indian alkaline soils are deficient in iron due to high pH, high calcium carbonate, highly permeable coarse textured soils, and soils low in organic carbon content. This study is carried out to increase the iron use efficiency of soil by using promising microbial isolates. Production of siderophore by promising microbial isolates is a greatest invention which help in increasing uptake of iron. A short-term laboratory experiment was carried “To evaluate the siderophore productions by different promising microbial isolates using chrome azurol S assay technique”. Ten microbial isolates were inoculated on plate as well as in broth medium. Plates were observed for orange halo formation around the bacterial growth. The size of orange halo around the colony of each microbial isolates was measured. The broth cultures inoculated with inoculum, incubated at 28 ± 20C for 24-72 hr with constant shaking at 120 rpm. After the incubation, the culture broths were centrifuged at 10,000 rpm for 10 min. The cell free supernatants were subjected to quantitative estimation of siderophores by CAS-shuttle, absorbance was measured at 630 nm against a reference consisting of 0.5 ml of uninoculated broth and 0.5 ml of CAS reagent. Obtained results indicated that in both plate and broth assays medium inoculated with strain Pseudomonas fluorescens show significantly higher orange halo formation around the growth and maximum siderophore content in aliquot. Inoculation of this plant growth promoting microbial isolates will be the great achievement in replacing chemical fertilizers in agriculture.

Examining Participant Adherence with Wearables in an In-the-Wild Setting.

Wearable devices offer a wealth of data for ubiquitous computing researchers. For instance, sleep data from a wearable could be used to identify an individual's harmful habits. Recently, devices which are unobtrusive in size, setup, and maintenance are becoming commercially available. However, most data validation for these devices come from brief, short-term laboratory studies or experiments which have unrepresentative samples that are also inaccessible to most researchers. For wearables research conducted in-the-wild, the prospect of running a study has the risk of financial costs and failure. Thus, when researchers conduct in-the-wild studies, the majority of participants tend to be university students. In this paper, we present a month-long in-the-wild study with 31 Japanese adults who wore a sleep tracking device called the Oura ring. The high device usage results found in this study can be used to inform the design and deployment of longer-term mid-size in-the-wild studies.

Sources, seasonal cycling, and fate of plutonium in a seasonally stratified and radiologically contaminated pond

Unlike short-term laboratory experiments, studies at sites historically contaminated with radionuclides can provide insight into contaminant migration behavior at environmentally-relevant decadal timescales. One such site is Pond B, a seasonally stratified reservoir within Savannah River Site (SC, USA) has low levels (μBq L−1) of plutonium in the water column. Here, we evaluate the origin of plutonium using high-precision isotope measurements, investigate the impact of water column geochemistry on plutonium cycling during different stratification periods, and re-evaluate long-term mass balance of plutonium in the pond. New isotopic data confirm that reactor-derived plutonium overwhelms input from Northern Hemisphere fallout at this site. Two suggested mechanisms for observed plutonium cycling in the water column include: (1) reductive dissolution of sediment-derived Fe(III)-(oxyhydr)oxides during seasonal stratification and (2) plutonium stabilization complexed strongly to Fe(III)-particulate organic matter (POM) complexes. While plutonium may be mobilized to a limited extent by stratification and reductive dissolution, peak plutonium concentrations are in shallow waters and associated with Fe(III)-POM at the inception of stratification. This suggests that plutonium release from sediments during stratification is not the dominant mechanism driving plutonium cycling in the pond. Importantly, our analysis suggests that the majority is retained in shallow sediments and may become increasingly recalcitrant.

Automation complacency on the road

Given that automation complacency, a hitherto controversial concept, is already used to blame and punish human drivers in current accident investigations and courts, it is essential to map complacency research in driving automation and determine whether current research can support its legitimate usage in these practical fields. Here, we reviewed its status quo in the domain and conducted a thematic analysis. We then discussed five fundamental challenges that might undermine its scientific legitimation: conceptual confusion exists in whether it is an individual versus systems problem; uncertainties exist in current evidence of complacency; valid measures specific to complacency are lacking; short-term laboratory experiments cannot address the long-term nature of complacency and thus their findings may lack external validity; and no effective interventions directly target complacency prevention. The Human Factors/Ergonomics community has a responsibility to minimise its usage and defend human drivers who rely on automation that is far from perfect. Practitioner summary: Human drivers are accused of complacency and overreliance on driving automation in accident investigations and courts. Our review work shows that current academic research in the driving automation domain cannot support its legitimate usage in these practical fields. Its misuse will create a new form of consumer harms.

Sunscreen exposure interferes with physiological processes while inducing oxidative stress in seagrass Posidonia oceanica (L.) Delile

The effects of a commercial sunscreen mixture on the Mediterranean seagrass Posidonia oceanica were investigated, evaluating its response in physiological processes and biochemical indicators of oxidative stress. Short-term laboratory experiments were conducted recreating summer conditions, and two sunscreen concentrations were tested in whole P. oceanica plants placed inside aquaria. Although primary productivity of leaf segments seemed to benefit from sunscreen addition, probably due to inorganic nutrients released, the rest of the biological parameters reflected possible impairments in the overall functioning of P. oceanica as a result of oxidative damages. Chlorophyll production and nitrogen fixation associated with old leaves were inhibited under high sunscreen concentrations, which concurred with elevated reactive oxygen species production, catalase activity and polyphenols content in the seagrass leaves. These results emphasize the importance of directing future investigations on determining which specific components of sunscreen products are likely threatening the wellbeing of critical species, such as P. oceanica.

DFT Analysis of Ethanol Electro-Oxidation on Fe(110) and Fe3c(110) and Its Correlation with the Stress Corrosion Cracking of Carbon Steel

Stress Corrosion Cracking (SCC) of carbon steel in fuel-grade ethanol is typically intergranular in service, but it is nearly always transgranular, in short-term laboratory experiments. While this might be considered an inconvenience, it provides an important clue about the SCC mechanism. The important point is that the transgranular cracking occurs under much milder mechanical conditions than any known form of hydrogen embrittlement in ordinary carbon steel. For this and other reasons, hydrogen is not considered to be the cause of this form of SCC. Transgranular SCC of carbon steel occurs in a very particular set of environments. Anhydrous liquid ammonia, anhydrous ammonia-methanol and CO-CO2-H2O are the key systems to be considered, apart from alcohols. High-temperature water containing oxygen also causes transgranular SCC, but is a less severe environment, probably because a magnetite film imposes a compressive stress that partially opposes any embrittlement effect. In our view, the important factor connecting these examples is embrittlement by interstitials. Just as hydrogen can embrittle iron, so can nitrogen or carbon (or oxygen). The main distinction is the diffusivity of the interstitial in iron. Ammonia can be oxidized to N, and CO can be reduced to C (or, in the language of surface chemistry, this could be dissociative adsorption). Still, at ambient temperature, those interstitials can only diffuse a few nm in relevant times of seconds. But we know little about the effect of such near-surface embrittlement on the propagation of a crack, and research on such surface effects is very important. Striking mechanical and morphological similarities of the SCC of carbon steel in ethanolic media with those governed by a cleavage-like mechanism in CO-CO2 aqueous solutions prompted the investigation of the possibility of ethanol electrochemical oxidation into CO on ferrite (Fe) and cementite (Fe3C) surfaces. Density functional theory computations on (110) surfaces revealed that the catalytic activity of Fe and Fe3C through the α dehydrogenation pathway can significantly reduce the energy barrier of electro-oxidation of ethanol and production of CO to 0.575 and 0.480 eV, respectively. These first principle calculations indicate that at the anodic potentials applied during potentiostatic slow strain rate testing, ethanol electro-oxidation to CO is thermodynamically viable on carbon steel, giving further credit to the involvement of cleavage type SCC of carbon steel in ethanolic environments.

Bentonite–Concrete Interactions in Engineered Barrier Systems during the Isolation of Radioactive Waste Based on the Results of Short-Term Laboratory Experiments

Bentonite clays have unique properties that determine their use as the main component of engineered barrier systems (EBS) for the isolation of radioactive waste. At present, the Russian Federation is elaborating the concept of deep geological disposal of radioactive waste in crystalline rocks of the Yeniseisky site, where bentonite clays play an important role in ensuring the safety of the repository for a long period of time. This work demonstrates the first results of short-term laboratory experiments (1 and 3 months) on the thermochemical interaction of bentonite and concrete in the presence of synthetic water at an elevated temperature. These experiments will help predict the effect of EBS materials on montmorillonite. Bentonite from the 10th Khutor deposit (Russia) and Portland cement were used in the experiments. At the first stage of the experiments, solutions were obtained after leaching the concrete with a synthetic groundwater solution for 1 month at 90 °C. At the second stage, the interactions of the obtained solutions with bentonite at 90 °C were studied. As a result of the experiments, the processes of concrete leaching were revealed, which changed the composition and acidity (an increase in the pH from 6.1 to 12.1) of the synthetic water and led to an increase in the porosity of the material in contact with the solution. However, no dissolution of montmorillonite was observed, and the changes were quite small. The research results show the high stability of bentonite from the 10th Khutor deposit under model conditions, which was confirmed by modeling. Thus, we can say that at pH ≈ 12 and at elevated temperatures, montmorillonite retains a stable structure for a long time, which is important for ensuring the safety of disposal in general.

Recent weathering promotes C storage inside large phyllosilicate particles in forest soil

Mineral weathering in soils is expected to promote chemical and physical interactions between soil organic matter and mineral phases, which are known to enhance the protection of organic matter from decomposition. The investigation of mineral-organic associations (MOAs) formation during weathering is therefore crucial to understanding carbon storage processes in soils. Until now studies have been mainly conducted by building inferences from soil characteristics, through short-term laboratory experiments in simplified conditions, or over very long-term time scales using soil chronosequences. Weathering can significantly alter the mineral matrix at the annual timescale, but knowledge regarding MOA formation processes occurring in situ, over short time scales and during the first stage of mineral weathering is lacking.To fill this gap, we performed a mesh bag incubation containing large Na-saturated and organic carbon-free vermiculite particles (200–400 µm in size) in acidic soil of a Douglas-fir forest, in the Beaujolais area (France). The vermiculite bags were deposited at the interface between the forest floor and the mineral soil, where intense weathering occurs. After 20 years of soil incubation, the weathered vermiculite particles were collected and characterized at the macroscale (X ray diffraction and physicochemical analyses), at the microscale (scanning electron microscopy-SEM imaging and element mapping) and at the nanoscale (transmission electron microscopy-TEM imaging, element mapping and speciation by electron energy loss spectroscopy-EELS) on a focus ion beam (FIB) section exposing the inside section of vermiculite particles.Cation exchange capacity, exchangeable cations and elemental analysis of the vermiculite particles showed important changes after 20 years of incubation. The initial exchangeable Na pool was completely depleted. The cation exchange capacity strongly decreased from 178.1 cmolc kg−1 to 49.2 cmolc kg−1 due to interlayer hydroxylation of the weathered vermiculite. The weathering budget indicated a 10% vermiculite dissolution and an organic carbon (C) enrichment of 5 mg g−1.Microscope images and elemental mapping of control vermiculite particles (nonincubated) showed a flat, smooth surface morphology with no detected C. In contrast, 20-year weathered vermiculite particles showed irregular outer- and inner-surfaces marked by multiple cracks from chemical dissolution. Some nano- and microscale exfoliation spaces filled with C were observed inside the weathered particles. C in association with Ca occurred in nanoscale exfoliation spaces. C also occurred entrapped in nanocrystalline Mn oxides (hausmannite) or K-rich aluminosilicates, which precipitated in micro-sized exfoliation spaces. These observations indicated that C storage inside the altered vermiculite particles was both mediated by chemical binding and physical entrapment. The functional groups of the organic matter revealed by EELS spectroscopy strongly differed between nano- and microscale exfoliation spaces.This study using the mineral bag incubation method provides evidence of new processes driving C storage inside large phyllosilicate particles during their initial and recent weathering, which could contribute to long-term C stabilization.

Effects of ammonium levels on growth and accumulation of antioxidative flavones of the submerged macrophyte Ceratophyllum demersum

Field data on the occurrence of the common and cosmopolitan submerged macrophyte Ceratophyllum demersum in relation to the water ammonium content were compared with the response of the plants to different ammonium treatments performed in the laboratory. Ammonium concentrations above 10 μM in the monitored area were found to be a strong limiting factor on the presence of C. demersum in water bodies. On the other hand, no adverse effect of nitrate was observed. In short-term laboratory experiments, the plants grew well even at 100 μM ammonium at pH 7.5, but higher concentrations affected the plant. Laboratory experiments showed that the accumulation of flavonoids with antioxidant properties was induced by ammonium. The detailed LC/MS analysis of the major flavonoids showed that the most abundant compound was tricetin present mainly as a monoglycoside in crude extracts. Luteolin, selgin, apigenin, tricin and chrysoeriol glycosides were also present in considerable amounts. Tricetin, a flavonoid having strong antioxidative properties, was most induced by higher ammonium levels. At high ammonium concentrations, plant tissues exhibited notable damage and the production of antioxidants declined.

Molybdenum, phosphorus, and pH do not constrain nitrogen fixation in a tropical forest in the southeastern Amazon.

High rates of biological nitrogen fixation (BNF) are commonly reported for tropical forests, but most studies have been conducted in regions that receive substantial inputs of molybdenum (Mo) from atmospheric dust and sea-salt aerosols. Even in these regions, the low availability of Mo can constrain free-living BNF catalyzed by heterotrophic bacteria and archaea. We hypothesized that in regions where atmospheric inputs of Mo are low and soils are highly weathered, such as the southeastern Amazon, Mo would constrain BNF. We also hypothesized that the high soil acidity, characteristic of the Amazon Basin, would further constrain Mo availability and therefore soil BNF. We conducted two field experiments across the wet and dry seasons, adding Mo, phosphorus (P), and lime alone and in combination to the forest floor in the southeastern Amazon. We sampled soils and litter immediately, and then weeks and months after the applications, and measured Mo and P availability through resin extractions and BNF with the acetylene reduction assay. The experimental additions of Mo and P increased their availability and the lime increased soil pH. While the combination of Mo and P increased BNF at some time points, BNF rates did not increase strongly or consistently across the study as a whole, suggesting that Mo, P, and soil pH are not the dominant controls over BNF. In a separate short-term laboratory experiment, BNF did not respond strongly to Mo and P even when labile carbon was added. We postulate that high nitrogen (N) availability in this area of the Amazon, as indicated by the stoichiometry of soils and vegetation and the high nitrate soil stocks, likely suppresses BNF at this site. These patterns may also extend across highly weathered soils with high N availability in other topographically stable regions of the tropics.

Short-term lab assessments and microcolonies are insufficient for the risk assessment of insecticides for bees

Risk assessment studies addressing effects of agrochemicals on bumblebees frequently use microcolonies. These are queenless colonies consisting of workers only in which typically one worker will lay unfertilized male-destined eggs. In the first tier of risk assessment for bees, short-term laboratory experiments (e.g. microcolonies) are used, the results of which will determine whether higher tier (semi-)field experiments are needed. To evaluate the suitability of microcolonies for risk assessment, a direct comparison between different assessment methods for the neonicotinoid pesticides acetamiprid and thiacloprid was made: microcolonies and queenright colonies under short-term laboratory conditions, queenright colonies under long-term laboratory conditions, and queenright colonies under field conditions. Here, we demonstrate that results from microcolonies contradict results from queenright colonies. While thiacloprid negatively impacted gyne production in queenright colonies, it had a positive effect on microcolony size. By contrast, thiacloprid had no significant effect on fitness parameters of queenright colonies under short-term laboratory conditions when mostly workers are produced. These results thus highlight both the need for long term assessments, allowing evaluation of gyne production, and the risk of reaching erroneous conclusions when using microcolonies. The negative effect of thiacloprid on colony fitness was confirmed under field conditions, where thiacloprid affected the production of reproductives, colony weight gain, worker weight, and foraging behaviour. For acetamiprid, a negative trend on colony fitness could only be shown in a field setup. Therefore, field-realistic setups, which allow colonies to forage freely, are most appropriate to assess sublethal effects of pesticides affecting behaviour and learning.

The effects of parasite exposure on mortality from aquatic contaminants, carbaryl and elevated salinity, in a freshwater crustacean

Abstract Freshwater pollution is a major global concern. Common methods for determining the effects of contaminants on freshwater organisms involve short-term laboratory experiments with otherwise healthy organisms. However, in natural systems, organisms are commonly exposed to parasites, which could alter their ability to survive exposure to aquatic contamination. We used a freshwater crustacean (Daphnia dentifera) to quantify the effects of parasite exposure on mortality from two common freshwater contaminants (elevated salinity [NaCl] and carbaryl). In our salinity trial, both parasite exposure and elevated salinity reduced survival in an additive manner. In our carbaryl trial, exposure to carbaryl reduced survival and we found a less-than-additive (i.e. antagonistic) interaction between carbaryl and the parasite; the parasite only reduced survival in the control (no carbaryl) treatments. Our results demonstrate that parasites and contaminants can jointly affect mortality in aquatic organisms in an additive or less-than-additive manner.

Short-term effects of hypoxia are more important than effects of ocean acidification on grazing interactions with juvenile giant kelp (Macrocystis pyrifera)

Species interactions are crucial for the persistence of ecosystems. Within vegetated habitats, early life stages of plants and algae must survive factors such as grazing to recover from disturbances. However, grazing impacts on early stages, especially under the context of a rapidly changing climate, are largely unknown. Here we examine interaction strengths between juvenile giant kelp (Macrocystis pyrifera) and four common grazers under hypoxia and ocean acidification using short-term laboratory experiments and field data of grazer abundances to estimate population-level grazing impacts. We found that grazing is a significant source of mortality for juvenile kelp and, using field abundances, estimate grazers can remove on average 15.4% and a maximum of 73.9% of juveniles per m2 per day. Short-term exposure to low oxygen, not acidification, weakened interaction strengths across the four species and decreased estimated population-level impacts of grazing threefold, from 15.4% to 4.0% of juvenile kelp removed, on average, per m2 per day. This study highlights potentially high juvenile kelp mortality from grazing. We also show that the effects of hypoxia are stronger than the effects of acidification in weakening these grazing interactions over short timescales, with possible future consequences for the persistence of giant kelp and energy flow through these highly productive food webs.

Field biotite weathering rate determination using U-series disequilibria

The chemical weathering rate of silicates is a key parameter of several geochemical processes; however, the long-term field measurement of these rates remains challenging. Currently, there are several methods for quantifying field weathering rates, but each presents it's own unique set of difficulties. In this study uranium-series nuclides were used to investigate long-term biotite weathering in a soil profile. For this purpose, pseudomorph grains of biotites (including weathering products) were hand-picked from four horizons of a soil profile and from underlying granitic saprolite from the experimental Breuil-Chenue site (France).Unexpected behaviors of U and Th nuclides were recorded from these samples. An unambiguous leaching of 232Th occurs during the weathering of biotite, while reduced U release relative to Th was observed, implying an efficient redistribution of U between the primary mineral and weathering products within the pseudomorphs. The measured U-series activity ratios reflect a regular and self-consistent pattern evolution. However, the “U-series-derived-weathered-stage” is not always coherent with the weathering features of major elements and/or with the location of the samples within the soil profile. For instance, biotite from the saprolite displays U-series activity ratios typical of significantly weathered samples, while major elements present rather limited signs of weathering. These results suggest an incongruent leaching of U and Th isotopes and suggest that U- and Th-series nuclides probe some water-mineral interactions that occur before macroscopic mineral tansformation.Using an open-system leaching model, coupled (234U/238U), (234U/230Th), and (226Ra/230Th) disequilibria measured from the samples allow us to calculate a weathering duration range of 6–52 ky for most weathered samples of this soil profile. The biotite weathering rate deduced from these data ranges from 7.8 × 10−17 mol·m−2·s−1 to 6.5 × 10−16 mol·m−2·s−1, which is consistent with the range of field rates previously reported. This rate was compared to the weathering rate of biotites induced by the substitution of vegetation occuring 35 years ago in a nearby soil profile, which was about 2–3 orders of magnitude higher than the long-term rate reported above. This feature is perfectly consistent with the decrease in the weathering rate with time that was previously widely documented but that still remains debated. Our results allude to a valuable use of U-series isotopes for mineral-weathering field rate determination and report a decrease in silicate weathering rates over long- (10,000s of years) and short-term (10s of years) weathering events recorded from the same site. The results show that short term laboratory experiments can be representative of field processes, and suggest that some forms of mineral weathering reactivation, similar to that observed during laboratory experiments, may naturally occur in soils in response to high frequency perturbation processes such as land cover change.

Sulfur Development in the Water-Sediment System of the Algae Accumulation Embay Area in Lake Taihu

Sulfur development in water-sediment systems is closely related to eutrophication and harmful algae blooms (HABs). However, the development of sulfur in water-sediment systems during heavy algae accumulation still remains unclear, especially in hyper-eutrophic shallow lakes. In this study, a quarterly field investigation was carried out for a year in the algae accumulated embay area of Lake Taihu, accompanied by a short-term laboratory experiment on algae accumulation. The results show that hydrogen sulfide and methanethiol dominated the volatile sulfur compounds (VSCs) in the water during non-accumulation seasons, whereas the concentrations of dimethyl sulfides increased during heavy algae accumulation, both in the field and the laboratory. An increase in the acid volatile sulfide (AVS) in the surface sediments was also discovered together with the increase in dimethyl sulfides. The depletion of oxygen in the overlying water and sediment–water interface during the heavy algae accumulation and decomposition was found to be closely related to both the increase in VSCs in the overlying water and increase in AVS in the sediment. The increased concentrations of these reductive sulfocompounds might aggravate the eutrophication and HABs and should be given more consideration in future eutrophication control plans for lakes.

Mechanistic Effect Modeling Approach for the Extrapolation of Species Sensitivity.

In the higher-tier environmental risk assessment of chemicals, species sensitivity distributions (SSDs) are used to statistically describe differences in sensitivity between species and derive community level endpoints. SSDs are usually based on the results from short-term laboratory experiments performed under constant environmental conditions. However, different species may be kept at different "optimal" temperatures, which influence their apparent sensitivity and thus the derivation of endpoints. Also, the extrapolation capacity of SSDs is largely limited to the tested species and conditions. Time-variable exposures and effects at higher levels of biological organization, including biological interactions, are not considered. The quantitative effect prediction at higher tiers would ultimately require the extrapolation of toxicokinetics and toxicodynamics to untested species and the involvement of population and community modeling. In this regard, we tested a toxicokinetic-toxicodynamic modeling approach to mechanistically consider and correct endpoints for ambient temperature and demonstrate the significance for SSDs. We explored correlations in toxicokinetic-toxicodynamic model parameters which would allow for the extrapolation of sensitivities to untested species. Finally, we illustrate the applicability of the approach for higher level effect predictions using an individual-based model. Our results suggest that mechanistic effect modeling approaches can reduce the uncertainties in higher tier effect assessments related to knowledge gaps.

INFLUENCE OF HUMIC PREPARATIONS ON DEGRADED SOILS PROPERTIES OF TECHNOGENIC BARRENS

This research aim was testing the applicability of exogenic organic matter – extracted humic substances – for the remediation of technogenic barrens soils near Cu-Ni smelter (Kola Peninsula). In short-term laboratory experiments we studied the possibility of stabilization of heavy metals labile forms by commercial humic substances (HS) of different origin (peat humate “Flexom” and coal humate “Extra”) in comparison with HS, inoculated by microorganisms – nitrogen fixers and mycorrhizae-forming fungi and mineral fertilizers (NPK и CaCO3). Experiments were provided during 45 days after 14 days of pre-incubation under controlled conditions in climate chamber with light, temperature and humidity imitating the polar day conditions in Kola Subarctic. After experiments we evaluated changes in soil chemical properties, soil microbial community and test-culture (Deschampsia cespitosa). Peat humate application is ineffective without additional manipulations (e.g. combination with CaCO3), cooperation with biological applicants cannot be pointed out. Application of coal humate favours to metals stabilization, soil microorganism’s activation, test-culture growth. It may be effective to combine coal humate with biological applicants like mycorrhizae-forming fungi. So, coal-humates may be perspective growth-stimulator, ameliorant and detoxicant in remediation of degraded soils in conditions of polymetallic contamination.

Long-term outdoor lysimeter study with cerium dioxide nanomaterial

Fate and impact of cerium dioxide nanomaterials (CeO2 NM) in soil remains uncertain. Most of the recent environmental studies used high doses of CeO2 NM in short-term laboratory experiments and stated soil as large sink for NM. Recent studies covering the life cycle of plants found evidence for particle uptake in crop plants, and triggered concern about NM entering the food chain. Here, we present a 25 months outdoor lysimeter study that investigates the translocation, biological impact, and transformation of CeO2 NM in soils cultivated with different crops (wheat (Triticum aestivum L.), canola (Brassica napus L.), and barley (Hordeum vulgare L.)). Low doses of CeO2 NM (NM-212, 10 and 50 mg CeO2 NM kg−1 soil) were applied to a Cambisol by sewage sludge or artificial rainwater. To simulate ploughing, the CeO2 NM was mixed into the first 20 cm of the lysimeter soil. Three weeks after the NM application by sewage sludge and five days after the latest NM application by artificial rainwater wheat seeds were sown.We found no vertical Ce translocation to deeper soil layers as well as negligible release of Ce into percolating water, confirming that soil is a sink for CeO2 NM. Furthermore, no inhibition of the NM sensitive ammonium oxidizing bacteria (AOB) was observed which implies a low bioavailability of CeO2 NM in soil. The detected Ce root uptake for canola (Ce < 35.7 mg kg−1) and barley (Ce < 61.8 mg kg−1) indicates that physico-chemical conditions in the rhizosphere or the aging of the NM in soil can remobilize the applied CeO2 NM to some extent. One can speculate that the obtained reduction of Ce4+ to Ce3+ (≈ 50% after 25 months) was coupled to different conditions (ionic strength, pH, water content, soil organic matter content) in the rhizosphere and necessary for the root accumulation of Ce.Due to negligible mobility in the soil-water interface, as well as non-toxicity to AOB, the environmental risk of the tested CeO2 NM appears to be low, compared to other highly mobile emergent pollutants. Nonetheless, further long-term investigations need to focus on the speciation and localization of NM in plants to clarify uptake and impact of NM to crops.