Results 1 - 10 of 7513
Results 1 - 10 of 7513. Search took: 0.027 seconds
|Sort by: date | relevance|
[en] Surveying toxicity of complex geochemical media as aquatic sediments often yields results that are either difficult to interpret or even contradictory to acknowledged theory. Multi-level biomarkers were investigated in a benthic fish exposed to estuarine sediments through laboratory and in situ bioassays, to evaluate their employment either in ecological risk assessment or in more mechanistic approaches to assess sediment-bound toxicity. Biomarkers reflecting lesions (such as genotoxicity or histopathology), regardless of their low or absent specificity to contaminants, are efficient in segregating exposure to contaminated from uncontaminated sediments even when classical biomarkers like CYP1A and metallothionein induction are inconclusive. Conversely, proteomics and gene transcription analyses provided information on the mechanics of toxicity and aided explaining response variation as a function of metabolic imbalance and impairment of defences against insult. In situ bioassays, although less expedite and more affected by confounding factors, produced data better correlated to overall sediment contamination. Highlights: ► Sediment-bound contaminant mixtures can yield unexpected biomarker responses in fish. ► Biomarkers reflecting lesions are sturdier predictors of pollution by mixed xenobiotics. ► Proteomics and gene transcription analyses disclosed the existence of complex patterns of response to toxicity. ► Laboratory bioassays are less impacted by noise variables but tend to lose ecological relevance. - Evaluation of multi-level biomarker responses in fish for ecological risk assessment
[en] Organochlorine compounds (OC) were determined in Arctic bivalves (Mya truncata, Serripes groenlandicus, Hiatella arctica and Chlamys islandica) from Svalbard with regard to differences in geographic location, species and variations related to their size and age. Higher chlorinated polychlorinated biphenyls (PCB 101–PCB 194), chlordanes and α-hexachlorocyclohexane (α-HCH) were consistently detected in the bivalves and PCBs dominated the OC load in the organisms. OC concentrations were highest in Mya truncata and the lowest in Serripes groenlandicus. Species-specific OC levels were likely related to differences in the species’ food source, as indicated by the δ13C results, rather than size and age. Higher OC concentrations were observed in bivalves from Kongsfjorden compared to the northern sampling locations Liefdefjorden and Sjuøyane. The spatial differences might be related to different water masses influencing Kongsfjorden (Atlantic) and the northern locations (Arctic), with differing phytoplankton bloom situations. - Highlights: ► Organochlorine compounds (OC) were analyzed in 4 bivalve species from Svalbard. ► Polychlorinated biphenyls dominated the OC load observed in the bivalves. ► Atlantic water influenced bivalves had higher OC levels than those from Arctic water. ► Location and species, rather than size and age, determined the OC pattern found. - New findings of organochlorines in Arctic bivalves that are central for evaluating the importance of geographical location and species for the organochlorine pattern in benthic organisms.
[en] Trophic transfer of Hg across lakes within a region has been related to multiple environmental factors, but the nature of these relationships across distinct basins within individual large lakes is unknown. We investigated Hg bioaccumulation in zooplankton in basins of differing trophic status in Lake Champlain (Vermont, USA) to determine the strongest predictors of Hg bioaccumulation. Zooplankton were sampled in Malletts Bay (oligotrophic) and Missisquoi Bay (eutrophic) in 2005–2008. Zooplankton in the eutrophic basin had lower concentrations of total Hg and MeHg than those in the oligotrophic basin in all years but 2007, when no bloom occurred in Missisquoi. In addition, Hg concentrations in seston and small zooplankton, sampled during 2009 at 12 sites spanning the lake, decreased with increasing phytoplankton and zooplankton biomass. Thus, Hg bioaccumulation in zooplankton across basins in Lake Champlain is related to trophic status, as observed previously in multiple lake studies. - Highlights: ► Lake Champlain zooplankton Hg was lower in the eutrophic than the oligotrophic basin. ► Algal blooms in years present biodiluted Hg in plankton. ► Lake-wide spatial patterns of Hg in plankton decreased with increasing biomass. ► Lake-wide Hg bioaccumulation patterns are consistent with multiple lake studies. - Large spatiotemporal variations in MeHg bioaccumulation in zooplankton within a single large lake were linked to spatial variation in trophic status across basins and to inter-annual variation in algal density.
[en] To determine if long-term equilibration may alleviate molybdenum toxicity, earthworms, enchytraeids, collembolans and four plant species were exposed to three soils freshly spiked with Na2MoO4.2H2O and equilibrated for 6 or 11 months in the field with free drainage. Total Mo concentrations in soil decreased by leaching, most (up to 98%) in sandy soil and less (54–62%) in silty and clayey soils. Changes in residual Mo toxicity with time were inconclusive in sandy soil. In the other two soils, toxicity of residual total Mo was significantly reduced after 11 months equilibration with a median 5.5-fold increase in ED50s. Mo fixation in soil, i.e. the decrease of soil solution Mo concentrations at equivalent residual total soil Mo, was maximally a factor of 2.1 only. This experiment shows natural attenuation of molybdate ecotoxicity under field conditions is related to leaching of excess Mo and other ions as well as to slow ageing reactions. - Highlights: ► Three molybdate-spiked soils were equilibrated for 6 and 11 months outdoors. ► Mo chronic toxicity to earthworms, enchytraeids, Collembola and four plant species was assessed. ► Mo concentrations in all soils decreased due to leaching. ► Based on actual total Mo remaining in the soil, Mo toxicity decreased by a median factor of 5.5. ► Decreased Mo toxicity was due to leaching as well as slow ageing reactions. - Natural attenuation under field conditions is more related to leaching of excess molybdate than to slow ageing reactions
[en] While nano-Fe2O3(magnetic) is generally considered non-toxic, it could serve as a carrier of other toxic chemicals such as As(V) and enhance their toxicity. The bioaccumulation of nano-Fe2O3(m) with different exposure times, NP concentrations, and pH conditions was investigated using Ceriodaphnia dubia (C. dubia) as the model organism. Under natural pH conditions, C. dubia significantly accumulated nano-Fe2O3(m) in the gut, with the maximum accumulation being achieved after 6 h of exposure. The concentration of nano-Fe2O3 also impacted its accumulation, with the maximum uptake occurring at 20 mg/L or more. In addition, the highest bioaccumulation occurred in a pH range of 7–8 where the highest feeding rate was reported, confirming that the ingestion of NPs is the main route of nano-Fe2O3(m) bioaccumulation. In a clean environment without NPs, depuration of nano-Fe2O3(m) occurred, and food addition accelerated the depuration process. - Highlights: ► Nano-Fe2O3(m) enhances the toxicity of As(V). ► C. dubia significantly accumulate nano-Fe2O3(m) through ingestion. ► The bioaccumulation of nano-Fe2O3(m) is affected by time, NP concentration, and pH. ► Food addition accelerates the depuration process of accumulated nano-Fe2O3(m). - Nano-Fe2O3(m) could enhance the toxicity of As(V) due to the significant accumulation of nano-Fe2O3(m) along with sorbed As(V) by C. dubia through ingestion.
[en] Endocrine disrupting chemicals (EDCs) found in wastewater treatment plant (WWTP) effluents have been shown to cause adverse effects, but the uptake of EDCs from effluents (measured in fish muscle) are not known. In this study, the biological effects and bioaccumulation of steroidal and phenolic EDCs were assessed in high-back crucian carp (Carassius auratus) exposed to WWTP effluents for 141 days. Compared with fish controls caged in Dianchi Lake, a significant reduction in gonadosomatic index (GSI) and increase in hepatosomatic index (HSI) and plasma vitellogenin (VTG) levels were observed in effluent-exposed fish. The concentrations of steroids and phenols in effluent-exposed fish showed time-dependent increase during the exposure. In addition, bioconcentration factors (BCFs) for steroids and phenols were between 17 and 59 on day 141. The results confirm that steroids and phenols bioconcentrate in fish muscle and this accumulation may account for the biological effects associated with exposures to WWTP effluents. - Highlights: ► We assess the potential risk of WWTP effluents to fish. ► We investigate the biological responses of EDCs in fish exposed to effluents. ► We estimate the uptake of EDCs originating from WWTP effluents in fish. ► The bioaccumulation of EDCs may account for the biological effects of effluents. - Bioaccumulation of endocrine disrupting chemicals in WWTP effluent-exposed fish.
[en] Global fate and transport of γ-HCH and DDT was studied using a global multicompartment chemistry-transport model, MPI-MCTM, with and without inclusion of land ice (in Antarctica and Greenland) or snow cover (dynamic). MPI-MCTM is based on coupled ocean and atmosphere general circulation models. After a decade of simulation 4.2% γ-HCH and 2.3% DDT are stored in land ice and snow. Neglection of land ice and snow in modelling would underestimate the total environmental residence time, τov, of γ-HCH and overestimate τov for DDT, both on the order of 1% and depending on actual compartmental distribution. Volatilisation of DDT from boreal, seasonally snow covered land is enhanced throughout the year, while volatilisation of γ-HCH is only enhanced during the snow-free season. Including land ice and snow cover in modelling matters in particular for the Arctic, where higher burdens are predicted to be stored. - Highlights: ► Land ice and snow hosts 2–4% of the global environmental burden of γ-HCH and DDT. ► Inclusion of land ice and snow cover matters for global environmental residence time. ► Including of land ice and snow cover matters in particular for the Arctic. - The inclusion of cycling in temporary snow cover and land ice in the model is found relevant for predicted POPs multicompartmental distribution and fate in the Arctic and on the global scale.
[en] The study is focused on artificial soil which is supposed to be a standardized “soil like” medium. We compared physico-chemical properties and extractability of Phenanthrene from 25 artificial soils prepared according to OECD standardized procedures at different laboratories. A substantial range of soil properties was found, also for parameters which should be standardized because they have an important influence on the bioavailability of pollutants (e.g. total organic carbon ranged from 1.4 to 6.1%). The extractability of Phe was measured by supercritical fluid extraction (SFE) at harsh and mild conditions. Highly variable Phe extractability from different soils (3–89%) was observed. The extractability was strongly related (R2 = 0.87) to total organic carbon content, 0.1–2 mm particle size, and humic/fulvic acid ratio in the following multiple regression model: SFE (%) = 1.35 * sand (%) − 0.77 * TOC (%)2 + 0.27 * HA/FA. - Highlights: ► We compared properties and extractability of Phe from 25 different artificial soils. ► Substantial range of soil properties was found, also for important parameters. ► Phe extractability was measured by supercritical fluid extraction (SFE) at 2 modes. ► Phe extractability was highly variable from different soils (3–89%). ► Extractability was strongly related to TOC, 0.1–2 mm particles, and HA/FA. - Significant variability in physico-chemical properties exists between artificial soils prepared at different laboratories and affects behavior of contaminants in these soils.
[en] The effects of ozone exposure during the cropping season on rice grain quality were investigated in chamber experiments employing four ozone treatments (charcoal filtered air, ambient, 2× ambient, and 2.5× ambient concentration) and six genotypes. The concentrations of protein and lipids in brown rice increased significantly in response to ozone, while starch concentration and thousand kernel mass decreased. Other parameters, including the concentrations of iron, zinc, phenolics, stickiness and geometrical traits did not exhibit significant treatment effects. Total brown rice yield, protein yield, and iron yield were negatively affected by ozone. Numerous genotypic differences occurred in the response to ozone, indicating the possibility of optimizing the grain quality in high ozone environments by breeding. It is concluded that although the concentrations of two important macronutrients, proteins and lipids, increased in ozone treated grains, the implications for human nutrition are negative due to losses in total grain, protein and iron yield. - Highlights: ► Exposure of rice plants to elevated ozone during growth led to altered grain quality. ► Protein and lipid concentration increased whereas starch concentration and thousand kernel weight decreased. ► Rice grain, protein and iron yield tended to decrease in plants exposed to high ozone. ► These effects were responsive to different ozone levels and showed genotypic differences. ► The overall effect of ozone o human nutrition is expected to be negative. - Ozone exposure during growth tends to increase the protein and lipid concentration in rice grains but decreases total grain and nutrient yields. These effects are dependent on ozone level and genotype.
[en] Ecological assessments over large spatial scales require that anthropogenic impacts be distinguishable above natural variation, and that monitoring tools are implemented to maximise impact detection and minimise cost. For three heavily modified and four relatively ‘pristine’ estuaries (disturbance category), chemical indicators (metals and PAHs) of anthropogenic stress were measured in benthic sediments, suspended sediments and deployed oysters, together with other environmental variables. These were compared with infaunal and hard-substrate invertebrate communities. Univariate analyses were useful for comparing contaminant loads between different monitoring tools and identified the strongest relationships between benthic and suspended sediments. However, multivariate analyses were necessary to distinguish ecological response to anthropogenic stressors from environmental “noise” over a large spatial scale and to identify sites that were being impacted by contaminants. These analyses provide evidence that suspended sediments are a useful alternative monitoring tool to detect potential anthropogenic impacts on benthic (infaunal and hard-substrate) communities. - Highlights: ► Ecological assessments require that anthropogenic impacts be distinguishable. ► Contaminant and environmental variables were measured in multiple estuaries. ► Variables were compared with benthic infauna and hard-substrate invertebrates. ► Multivariate analyses of monitoring tools important to explain ecological impacts. ► Suspended sediment a useful alternate monitoring tool in impact assessment. - Anthropogenic impacts can be consistently distinguished from natural environmental variation over large spatial scales using the appropriate monitoring tool for the ecological community.