Long-term effects of sulfidized silver nanoparticles in sewage sludge on soil microflora.

The use of silver nanoparticles (AgNPs) in consumer products such as textiles leads to their discharge into wastewater and consequently to a transfer of the AgNPs to soil ecosystems via biosolids used as fertilizer. In urban wastewater systems (e.g., sewer, wastewater treatment plant [WWTP], anaerobic digesters) AgNPs are efficiently converted into sparingly soluble silver sulfides (Ag2 S), mitigating the toxicity of the AgNPs. However, long-term studies on the bioavailability and effects of sulfidized AgNPs on soil microorganisms are lacking. Thus we investigated the bioavailability and long-term effects of AgNPs (spiked in a laboratory WWTP) on soil microorganisms. Before mixing the biosolids into soil, the sludges were either anaerobically digested or directly dewatered. The effects on the ammonium oxidation process were investigated over 140 d. Transmission electron microscopy (TEM) suggested an almost complete sulfidation of the AgNPs analyzed in all biosolid samples and in soil, with Ag2 S predominantly detected in long-term incubation experiments. However, despite the sulfidation of the AgNPs, soil ammonium oxidation was significantly inhibited, and the degree of inhibition was independent of the sludge treatment. The results revealed that AgNPs sulfidized under environmentally relevant conditions were still bioavailable to soil microorganisms. Consequently, Ag2 S may exhibit toxic effects over the long term rather than the short term. Environ Toxicol Chem 2017;36:3305-3313. © 2017 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Evaluation of the hazard potentials of river suspended particulate matter and floodplain soils in the Rhine basin using chemical analysis and in vitro bioassays.

The purpose of the present study was to assess the hazard potentials of contaminated suspended particulate matter (SPM) sampled during a flood event for floodplain soils using in vitro bioassays and chemical analysis. Sediment-contact tests were performed to evaluate the direct exposure of organisms to native soils and SPM at two different trophic levels. For comparison, acetonic extracts were tested using both contact tests and additionally two cell-based biotests for cytotoxicity and Ah receptor-mediated activity (EROD-Assay). The sediment-contact tests were carried out with the dehydrogenase assay with Arthrobacter globiformis and the fish embryo assay with Danio rerio. The results of this study clearly document that native samples may well be significantly more effective than corresponding extracts in the bacteria contact assay or the fish embryo test. These results question the commonly accepted concept that acetonic extracts are likely to overestimate the toxicity of soil and SPM samples. Likewise, the priority organic compounds analyzed failed to fully explain the toxic potential of the samples. The outcomes of this study revealed the insufficient knowledge regarding the relationship between the different exposure pathways. Finally, there is concern about adverse effects by settling suspended particulate matter and remobilized sediments in frequently inundated floodplain soils due to an increase of the hazard potential, if compared with infrequently inundated floodplain soils. We showed that the settling of SPM and sediments revealed a significant impact on the dioxin-like potencies of riparian soils.

Total aortic arch replacement: superior ventriculo-arterial coupling with decellularized allografts compared with conventional prostheses.

BACKGROUND: To date, no experimental or clinical study provides detailed analysis of vascular impedance changes after total aortic arch replacement. This study investigated ventriculoarterial coupling and vascular impedance after replacement of the aortic arch with conventional prostheses vs. decellularized allografts. METHODS: After preparing decellularized aortic arch allografts, their mechanical, histological and biochemical properties were evaluated and compared to native aortic arches and conventional prostheses in vitro. In open-chest dogs, total aortic arch replacement was performed with conventional prostheses and compared to decellularized allografts (n = 5/group). Aortic flow and pressure were recorded continuously, left ventricular pressure-volume relations were measured by using a pressure-conductance catheter. From the hemodynamic variables end-systolic elastance (Ees), arterial elastance (Ea) and ventriculoarterial coupling were calculated. Characteristic impedance (Z) was assessed by Fourier analysis. RESULTS: While Ees did not differ between the groups and over time (4.1±1.19 vs. 4.58±1.39 mmHg/mL and 3.21±0.97 vs. 3.96±1.16 mmHg/mL), Ea showed a higher increase in the prosthesis group (4.01±0.67 vs. 6.18±0.20 mmHg/mL, P<0.05) in comparison to decellularized allografts (5.03±0.35 vs. 5.99±1.09 mmHg/mL). This led to impaired ventriculoarterial coupling in the prosthesis group, while it remained unchanged in the allograft group (62.5±50.9 vs. 3.9±23.4%). Z showed a strong increasing tendency in the prosthesis group and it was markedly higher after replacement when compared to decellularized allografts (44.6±8.3 dyn·sec·cm(-5) vs. 32.4±2.0 dyn·sec·cm(-5), P<0.05). CONCLUSIONS: Total aortic arch replacement leads to contractility-afterload mismatch by means of increased impedance and invert ventriculoarterial coupling ratio after implantation of conventional prostheses. Implantation of decellularized allografts preserves vascular impedance thereby improving ventriculoarterial mechanoenergetics after aortic arch replacement.

Incorporating availability/bioavailability in risk assessment and decision making of polluted sites, using Germany as an example.

Nearly all publications dealing with availability or bioavailability of soil pollutants start with the following statement: the determination of total pollutant content will lead to an over-estimation of risk. However, an assessment of contaminated sites should be based on the determination of mobile fractions of pollutants, and the fractions with potential for mobilisation that threaten groundwater and surface water, and the actual and potential fractions available for uptake by plants, soil microflora and soil organisms. After reviewing the literature for method proposals concerning the determination of available/bioavailable fractions of contaminants with respect to leaching, plants, microorganisms (biodegradation) and soil organisms, we propose a testing and assessment scheme for contaminated sites. The proposal includes (i) already accepted and used methods, (ii) methods which are under standardisation, and (iii) methods for which development has just started in order to promote urgently needed research.

Applicability of non-exhaustive extraction procedures with Tenax and HPCD.

Chemical extraction techniques like non-exhaustive extraction with Tenax or hydroxypropyl-ß-cyclodextrin (HPCD) have been shown to measure the biodegradable fraction of aromatic contaminants like PAHs in soil. However, there is little research on the chemical prediction of aliphatic hydrocarbon degradation. The aim of this study was to investigate the potential for HPCD and Tenax extractions to predict PAH and petroleum hydrocarbon biodegradation in soil. 11 historically contaminated soils with PAH concentrations between 74 and 680 mg/kg and concentrations of petroleum hydrocarbons from 330 to 4,704 mg/kg were analysed. Both non-exhaustive extraction procedures showed promising results for estimating the available contaminant fraction of both contaminant groups concerning the feasibility, reproducibility and correlation with soil biodegradation applying single point testing. Both methods have the potential to be used to assess the biodegradable hydrophobic organic pollutant fraction in contaminated soils. In a direct comparison of the two extraction procedures, Tenax extraction is assessed to be more time-consuming than HPCD extraction. Furthermore, a sufficient soil/Tenax ratio has to be considered.

Effects of silver nanoparticles and silver nitrate in the earthworm reproduction test.

The widespread use of silver nanoparticles (Ag-NPs), for example, in textiles and cleaning products, means that they are likely to reach the environment via biosolids or the effluent from wastewater treatment plants. The aim of the present study was to determine the ecotoxicity of Ag-NPs in the earthworm reproduction test using Eisenia andrei. In addition to the usual endpoints, the authors also investigated the uptake and accumulation of Ag by adult earthworms and the concentration of free Ag(+) in soil pore water. Silver nanoparticles and Ag nitrate showed similar toxicities in the earthworm reproduction test. The uptake of Ag from Ag-NPs in the earthworm was slightly higher than the uptake of Ag from Ag nitrate. Spiked soils showed a concentration-dependent effect on reproduction, but there was no concentration-dependent increase in the amount of Ag in earthworm tissues. The authors noted a concentration-dependent increase in the levels of free Ag(+) in the soil pore water regardless of the Ag source. The number of juveniles is a more suitable endpoint than biomass or mortality. The uptake of Ag does not appear to inhibit reproduction. Instead, inhibition seems to reflect Ag(+) released into the soil pore water, which affects cocoons and juveniles in the soil. Analysis of transformed Ag-NPs after purification in wastewater treatment plants would provide additional information.

Derivation of soil values for the path 'soil-soil organisms' for metals and selected organic compounds using species sensitivity distributions.

BACKGROUND, AIMS AND SCOPE: According to the German Federal Soil Protection Act, the natural function of soil as a habitat for human beings, animals, plants and soil organisms is, among other things, to be protected by deriving soil values for important chemicals regarding their amounts in the environment, their persistence and/or their toxicity. This contribution presents the results of the mathematical derivation of such values for nine metals and ten organic substances from soil ecotoxicological effect values available in the literature for microbial processes, plants and soil invertebrates. MATERIAL AND METHODS: Ecotoxicological data were mostly extracted from published papers and reports and had to originate from valid studies that were performed according to internationally standardised guidelines (e.g. ISO) or were otherwise well documented, plausible and performed according to accepted laboratory practice. As test results, both structural (i.e., effects on mortality, growth or reproduction) and functional (i.e., effects on microbial activity or organic matter breakdown) parameters were included. The derivation of soil values was performed using the distribution based extrapolation model (DIBAEX) and EC(50)s (Effective Concentration) as input data. RESULTS: For 19 compounds, soil values could be calculated. In 18 of these 19 cases clear laboratory ecotoxicological effects (i.e., EC50 values) below the calculated soil value have been found in the literature. DISCUSSION: In those few cases where a comparison with field studies is possible, effects have been observed in the same order of magnitude as the calculated soil values. A comparison with other similar approaches confirmed the plausibility of the calculated values. CONCLUSIONS: The DIBAEX-method is a feasible and widely accepted method for deriving soil values from ecotoxicological input data. Data availability was already satisfactory for some substances, but other substances, especially organics, were only poorly covered. The soil values presented here were based on EC50 input data. However, depending on the protection level aimed at by using soil values in legislation, it might be appropriate to use other input data such as NOECs in the derivation process. RECOMMENDATIONS AND PERSPECTIVES: It is recommended to generate an appropriate number of data for further relevant substances by means of a test battery or multi-species approaches such as terrestrial model ecosystems. These tests should also consider the influence of the bioavailability of substances. A final recommendation for legally binding soil values demands a plausibility check of the mathematically derived values. This should include a comparison with natural background concentrations, soil values for other pathways and soil values used in legislation of other countries. Finally, expert judgement always has to be considered.

Scrapie Agent (Strain 263K) can transmit disease via the oral route after persistence in soil over years.

The persistence of infectious biomolecules in soil constitutes a substantial challenge. This holds particularly true with respect to prions, the causative agents of transmissible spongiform encephalopathies (TSEs) such as scrapie, bovine spongiform encephalopathy (BSE), or chronic wasting disease (CWD). Various studies have indicated that prions are able to persist in soil for years without losing their pathogenic activity. Dissemination of prions into the environment can occur from several sources, e.g., infectious placenta or amniotic fluid of sheep. Furthermore, environmental contamination by saliva, excrements or non-sterilized agricultural organic fertilizer is conceivable. Natural transmission of scrapie in the field seems to occur via the alimentary tract in the majority of cases, and scrapie-free sheep flocks can become infected on pastures where outbreaks of scrapie had been observed before. These findings point to a sustained contagion in the environment, and notably the soil. By using outdoor lysimeters, we simulated a contamination of standard soil with hamster-adapted 263K scrapie prions, and analyzed the presence and biological activity of the soil-associated PrP(Sc) and infectivity by Western blotting and hamster bioassay, respectively. Our results showed that 263K scrapie agent can persist in soil at least over 29 months. Strikingly, not only the contaminated soil itself retained high levels of infectivity, as evidenced by oral administration to Syrian hamsters, but also feeding of aqueous soil extracts was able to induce disease in the reporter animals. We could also demonstrate that PrP(Sc) in soil, extracted after 21 months, provides a catalytically active seed in the protein misfolding cyclic amplification (PMCA) reaction. PMCA opens therefore a perspective for considerably improving the detectability of prions in soil samples from the field.