Soil microbial community structure and functionality changes in response to long-term metal and radionuclide pollution

Microbial communities are essential for a healthy soil ecosystem. Metals and radionuclides can exert a persistent pressure on the soil microbial community. However, little is known on the effect of long-term co-contamination of metals and radionuclides on the microbial community structure and functionality. We investigated the impact of historical discharges of the phosphate and nuclear industry on the microbial community in the Grote Nete river basin in Belgium. Eight locations were sampled along a transect to the river edge and one location further in the field. Chemical analysis demonstrated a metal and radionuclide contamination gradient and revealed a distinct clustering of the locations based on all metadata. Moreover, a relation between the chemical parameters and the bacterial community structure was demonstrated. Although no difference in biomass was observed between locations, cultivation-dependent experiments showed that communities from contaminated locations survived better on singular metals than communities from control locations. Furthermore, nitrification, a key soil ecosystem process seemed affected in contaminated locations when combining metadata with microbial profiling. These results indicate that long-term metal and radionuclide pollution impacts the microbial community structure and functionality and provides important fundamental insights into microbial community dynamics in co-metal-radionuclide contaminated sites

Detailed plan for the COMET WP3 initial research activity - list of research projects and goals, participants and timing

Detailed plan for the COMET Work Package (WP) 3

The Radioecology Exchange

The Radioecology Exchange (www.radioecology-exchange.org) was created in 2011 under the EU FP7 STAR (STrategy for Allied Radioecology, www.star-radioecology.org) Network of Excellence; (2011-2015). This project aims to integrate radioecological research efforts of European organisations into a sustainable network. In 2013, the EU FP7 COMET (COordination and iMplementation of a pan-European instrumenT for radioecology (2013- 2017); www.comet-radioecology.org) project commenced; COMET will build upon the work initiated under STAR. The Radioecology Exchange has therefore become the web resource for activities from both projects which will ultimately be maintained by the European Radioecology Alliance (ALLIANCE; www.er-alliance.org). The Radioecology Exchange is intended to become a ‘gateway’ for information related to European (and wider) radioecological research

Bepaling en belang van de Henry coëfficient van bestrijdingsmiddelen

Bestrijdingsmiddelen worden in de landbouw gebruikt om gewassen te beschermen tegen ziekten, plagen en onkruiden, om zo de opbrengst veilig te stellen. Zowel druppeltjes als vaste deeltjes kunnen na bespuiting getransporteerd worden doorheen de lucht. Ook via verdamping vanop de bodem of het gewas kunnen bestrijdingsmiddelen in de lucht terechtkomen. De atmosfeer fungeert als een belangrijke transportroute waarna bestrijdingsmiddelen via droge of natte depositie op de bodem of in het water kunnen terechtkomen. Bij een groot aantal processen in het milieu speelt de Henry coëfficiënt een belangrijke rol, zoals bijvoorbeeld de uitwassing van bestrijdingsmiddelen uit de lucht. De Henry coëfficiënt kenmerkt de verdeling van een organische component tussen de gas- en waterfase. Voor een groot aantal modellen is het belangrijk een juiste Henry coëfficiënt als parameter in te geven. Theoretisch kan de Henry coëfficiënt berekend worden, maar deze waarde stemt vaak niet overeen met de werkelijkheid. Aangezien de Henry coëfficiënt eveneens een temperatuursafhankelijke parameter is, is het belangrijk dit verband experimenteel te onderzoeken met een eenvoudige methodiek voor verschillende bestrijdingsmiddelen. Reeds bestaande technieken voor de bepaling van de Henry coëfficiënt zijn vaak arbeidsintensief en vereisen meestal een grote hoeveelheid solvent. Er wordt dan ook gezocht naar nieuwe, eenvoudigere technieken die weinig tijdrovend zijn. De EPICS-SPME methode is een nieuwe techniek die al met succes is toegepast om de Henry coëfficiënt van vluchtige organische componenten te bepalen (Dewulf et al., 1999). Er wordt dan ook van deze studie vertrokken om de Henry coëfficiënt van bestrijdingsmiddelen te bepalen. Voor verschillende indicatorstoffen is er getracht om met de EPICS-SPME methode, een aanvaardbare Henry coëfficiënt te bepalen. De aldus bepaalde Henry coëfficiënten hebben een aanvaardbare precisie, maar komen niet overeen met andere waarden uit de literatuur. Uit het onderzoek blijkt dat én of meer systematische fouten hier waarschijnlijk de oorzaak van zijn. Met behulp van het computermodel EMSOFT zijn enkele simulaties uitgevoerd om enerzijds het verband na te gaan tussen de eigenschappen van het bestrijdingsmiddel en de bodemflux na toepassing. Anderzijds wordt met een eenvoudige simulatie het belang aangetoond van de temperatuursafhankelijkheid van de Henry coëfficiënt. Hieruit blijkt duidelijk dat de Henry coëfficiënt, en eveneens de bodemflux, verdubbelen bij een temperatuursstijging van 10 graden

Effects of environmental parameters on Lemna minor growth: An integrated experimental and modelling approach

Pollution of surface waters is a worldwide problem for people and wildlife. Remediation and phytoremediation approaches can offer a solution to deal with specific scenarios. Lemna minor, commonly known as duckweed, can absorb and accumulate pollutants in its biomass. To evaluate if L. minor could be applied for phytoremediation purposes, it is necessary to further investigate its remediation capability and to identify which parameters affect the remediation process. Such a model must include both plant growth and pollutant exchange. A remediation model based on a robust experimental study can help to evaluate L. minor as a proper remediation strategy and to predict the outcome of a L. minor based remediation system. To set up this model, this paper focusses on a detailed experimental study and a comprehensive mathematical modelling approach to represent L. minor growth as a function of biomass, temperature, light irradiation and variable nutrient concentrations. The influence of environmental conditions on L. minor growth was studied, by composing 7 days growth curves. Plants were grown under predefined environmental conditions (25°C, 14h photoperiod, 220 μmol m−2 s−1 light intensity and a modified Hoagland solution with 23.94 mg N L−1 and 3.10 mg P L−1 (N:P ratio of 7.73)) as standard for all experiments. The influence of different temperatures (6, 10, 15, 20, 25, 30 and 35°C), light intensities (63, 118, 170, 220 and 262 μmol m−2 s−1), photoperiods (12h and 14h) and N:P ratios (1.18, 3.36, 7.73 and 29.57) were tested in the model. As a result, a growth model was optimised using separate datasets for temperature, light intensity, photoperiod and nutrients and validated by further integrated testing. The growth model is a stable platform for application in phytoremediation of radionuclides in contaminated water, to be extended in future studies with information of pollutant uptake, pollutant-nutrient interactions and transfer to the biomass

Induction of Oxidative Stress and Antioxidative Mechanisms in Arabidopsis thaliana after Uranium Exposure at pH 7.5

To evaluate the environmental impact of uranium (U) contamination, it is important to investigate the effects of U at ecologically relevant conditions. Since U speciation, and hence its toxicity, strongly depends on environmental pH, the present study aimed to investigate dose-dependent effects of U at pH 7.5. Arabidopsis thaliana plants (Mouse-ear Cress) were exposed for three days to different U concentrations at pH 7.5. In the roots, the increased capacities of ascorbate peroxidase and glutathione reductase indicate an important role for the ascorbate-glutathione cycle during U-induced stress. However, a significant decrease in the ascorbate redox state was observed after exposure to 75 and 100 µM U, indicating that those roots are severely stressed. In accordance with the roots, the ascorbate-glutathione cycle plays an important role in the antioxidative defence systems in A. thaliana leaves exposed to U at pH 7.5 as the ascorbate and glutathione biosynthesis were upregulated. In addition, small inductions of enzymes of the antioxidative defence system were observed at lower U concentrations to counteract the U-induced stress. However, at higher U concentrations it seems that the antioxidative defence system of the leaves collapses as reductions in enzyme activities and gene expression levels were observed

Rhizophagus irregularis MUCL 41833 can colonize and improve P uptake of Plantago lanceolata after exposure to ionizing gamma radiation in root organ culture

Long-lived radionuclides such as 90Sr and 137Cs can be naturally or accidentally deposited in the upper soil layers where they emit β/γ radiation. Previous studies have shown that arbuscular mycorrhizal fungi (AMF) can accumulate and transfer radionuclides from soil to plant, but there have been no studies on the direct impact of ionizing radiation on AMF. In this study, root organ cultures of the AMF Rhizophagus irregularis MUCL 41833 were exposed to 15.37, 30.35, and 113.03 Gy gamma radiation from a 137Cs source. Exposed spores were subsequently inoculated to Plantago lanceolata seedlings in pots, and root colonization and P uptake evaluated. P. lanceolata seedlings inoculated with non-irradiated AMF spores or with spores irradiated with up to 30.35 Gy gamma radiation had similar levels of root colonization. Spores irradiated with 113.03 Gy gamma radiation failed to colonize P. lanceolata roots. P content of plants inoculated with non-irradiated spores or of plants inoculated with spores irradiated with up to 30.35 Gy gamma radiation was higher than in non-mycorrhizal plants or plants inoculated with spores irradiated with 113.03 Gy gamma radiation. These results demonstrate that spores of R. irregularis MUCL 41833 are tolerant to chronic ionizing radiation at high doses