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Arsenic-contaminated ground- and drinking water is a global environmental problem with about 1-2Prozent of the world's population being affected. The upper drinking water limit for arsenic (10 Micro g/l) recommended by the WHO is often exceeded, even in industrial nations in Europe and the USA. Chronic intake of arsenic causes severe health problems like skin diseases (e.g. blackfoot disease) and cancer. In addition to drinking water, seafood and rice are the main reservoirs for arsenic uptake. Arsenic is oftentimes of geogenic origin and in the environment it is mainly bound to iron(III) minerals. Iron(III)-reducing bacteria are able to dissolve these iron minerals and therefore release the arsenic to the environment. In turn, iron(II)-oxidizing bacteria have the potential to co-precipitate or sorb arsenic during iron(II)- oxidation at neutral pH followed by iron(III) mineral precipitation. This process may reduce arsenic concentrations in the environment drastically, lowering the potential risk for humans dramatically.The main goal of this study therefore is to quantify, identify and isolate anaerobic and aerobic Fe(II)-oxidizing microorganisms in arsenic-containing paddy soil. The co-precipitation and thus removal of arsenic by iron mineral producing bacteria will be determined in batch and microcosm experiments. Finally the influence of rhizosphere redox status on microbial Fe oxidation and arsenic uptake into rice plants will be evaluated in microcosm experiments. The long-term goal of this research is to better understand arsenic-co-precipitation and thus arsenic-immobilization by iron(II)-oxidizing bacteria in rice paddy soil. Potentially these results can lead to an improvement of living conditions in affected countries, e.g. in China or Bangladesh.
The decomposition of terrestrial organic material such as leaf litter represents a fundamental ecosystem function in streams that delivers energy for local and downstream food webs. Although agriculture dominates most regions in Europe and fungicides are applied widely, effects of currently used fungicides on the aquatic decomposer community and consequently the leaf decomposition rate are largely unknown. Also potential compensation of such hypothesised adverse effects due to nutrients or higher average water temperatures associated with climate change are not considered. Moreover, climate change is predicted to alter the community of aquatic decomposers and an open question is, whether this alteration impacts the leaf decomposition rate. The current projects follows a tripartite design to answer these research questions. Firstly, a field study in a vine growing region where fungicides are applied in large amounts will be conducted to whether there is a dose-response relationship between the exposure to fungicides and the leaf decomposition rate. Secondly, experiments in artificial streams with field communities will be carried out to assess potential compensatory mechanisms of nutrients and temperature for effects of fungicides. Thirdly, field experiments with communities exhibiting a gradient of taxa sensitive to climate change will be used to investigate potential climate-related effects on the leaf decomposition rate.
Chromium (Cr) is introduced into the environment by several anthropogenic activities. A striking ex-ample is the area around Kanpur in the Indian state of Uttar Pradesh, where large amounts of Cr-containing wastes have been recently illegally deposited. Hexavalent Cr, a highly toxic and mobile contaminant, is present in significant amounts in these wastes, severely affecting the quality of sur-roundings soils, sediments, and ground waters. The first major goal of this study is to clarify the solid phase speciation of Cr in these wastes and to examine its leaching behavior. X-ray diffraction and synchrotron-based X-ray absorption spectroscopy techniques will be employed for quantitative solid phase speciation of Cr. Its leaching behavior will be studied in column experiments performed at un-saturated moisture conditions with flow interruptions simulating monsoon rain events. Combined with geochemical modeling, the results will allow the evaluation of the leaching potential and release kinetics of Cr from the waste materials. The second major goal is to investigate the spatial distribution, speciation, and solubility of Cr in the rooting zone of chromate-contaminated soils surrounding the landfills, and to study the suitability of biochar as novel soil amendment for mitigating the deleterious effects of chromate pollution. Detailed field samplings and laboratory soil incubation studies will be carried out with two agricultural soils and biochar from the Kanpur region.
The nature of the microbial communities inhabiting the deeper soil horizons is largely unknown. It is also not clear why subsurface microorganisms do not make faster use of organic compounds under field conditions. The answer could be provided by a reciprocal soil transfer experiment studying the response of transferred soils to fluctuations in microclimate, organic inputs, and soil biota. The subproject P9 will be responsible for the establishment of reciprocal transfer experiments offering a strong link between subgroups interested in organic matter quality, transport of organic substances, as well as functions of the soil microbial community. A single, high molecular weight substrate (13C labelled cellulose) will be applied at two different levels in the pre-experiment to understand the dose-dependent reaction of soil microorganisms in transferred surface and sub-soils. Uniformly 13C labelled beech roots - representing complex substrates - will be used for the main reciprocal soil transfer experiment. We hypothesize that transferring soil cores between subsoil and surface soil as well as addition of labelled cellulose or roots will allow us to evaluate the relative impact of surface/subsurface habitat conditions and resource availability on abundance, function, and diversity of the soil microbial community. The second objective of the subproject is to understand whether minerals buried within different soil compartments (topsoil vs. subsoil) in the field contribute to creation of hot spots of microbial abundance and activity within a period of two to five years. We hypothesize that soil microorganisms colonize organo-mineral complexes depending on their nutritional composition and substrate availability. The existence of micro-habitat specific microbial communities could be important for short term carbon storage (1 to 6 years). The third objective is to understand the biogeography and function of soil microorganisms in different subsoils. Parent material as well as mineral composition might control niche differentiation during soil development. Depending on size and interconnectedness of niches, colonization and survival of soil microbial communities might be different in soils derived from loess, sand, terra fusca, or sandstone. From the methodological point of view, our specific interest is to place community composition into context with soil microbial functions in subsoils. Our subgroup will be responsible for determining the abundance, diversity, und function of soil microorganisms (13C microbial biomass, 13C PLFA, enzyme activities, DNA extraction followed by quantitative PCR). Quantitative PCR will be used to estimate total abundances of bacteria, archaea and fungi as well as abundances of specific groups of bacteria at high taxonomic levels. We will apply taxa specific bacterial primers because classes or phyla might be differentiated into ecological categories on the basis of their life strategies.
In this project we experimentally explore the transport of engineered inorganic nanoparticles (EINP) through soils. This is done for original EINPs and some pre-aged form. Transport of NPs in soil is expected to be different from that of reactive solutes, in that hydrodynamic drag, inertial and shear forces as well as the affinity to water-gas interfaces are expected to be more relevant. Hence, the mobility of EINPs in soil is highly sensitive to the morphology of the porous structure and the dynamics of water saturation.This project provides the pore network structure for natural soils using X-ray micro-tomography to allow for an up-scaling of pore-scale interactions explored by project partners to the scale of soil horizons. The pore structure is represented by a network model suitable for pore scale simulations including the dynamics of water-gas interfaces.Pore network simulations will be compared to column experiments for conservative tracers as well as for unaltered and pre-aged EINPs (obtained from INTERFACE). This includes steady state flow scenarios for saturated (ponding) and unsaturated conditions as well as for transient flow to explore the impact of moving water-gas interfaces. The final goal is to arrive at a consistent interpretation of experimental findings and numerical simulations to develop a module for modelling EINP transfer through soil as a function of particle properties, soil structural characteristics and external forcing in terms of flux boundary conditions.
Sekundäre Partikelneubildung ist eine Hauptquelle für atmosphärische Partikel mit wichtigen Folgen für das Klima und die menschliche Gesundheit. Dieses Vorhaben untersucht die Rolle von Luft Ionen bei der sekundären Partikelneubildung in Flussreaktor- und Aerosolkammer-Experimenten unter kontrollierten Laborbedingungen. Trotz beträchtlicher Fortschritte in der Messtechnik zur Untersuchung der atmosphärischen Nukleation und des Partikelwachstums bestehen weiterhin Verständnislücken hinsichtlich der grundlegenden physikalischen und chemischen Prozesse. Insbesondere die möglichen Effekte von Ionen-Partikel-Wechselwirkungen und von Ionenchemie auf die Partikelneubildung werden kontrovers diskutiert. In Ergänzung zu bestehenden Forschungsprogrammen hinsichtlich der Rolle von Ionen im initialen Nukleationsschritt wird vorgeschlagen, Ionen-Partikel-Wechselwirkungen während des anschließenden Partikelwachstums zu untersuchen und sich dabei auf direkte Messungen des Ladungszustands, der Wachstumsraten und der chemischen Zusammensetzung von sekundärem organischem Aerosol zu konzentrieren. Hierzu werden der Ladungszustand und die Wachstumsraten von Partikelpopulationen mit einem modifizierten Mobilitätspartikelspektrometer unter wohldefinierten Randbedingungen in Laborexperimenten quantifiziert. In einem nächsten Schritt werden die neuartigen Messmöglichkeiten unseres Aerosol-Massenspektrometers CAChUP voll ausgeschöpft, um den Beitrag verschiedener organischer Vorläufergase zur chemischen Zusammensetzung von sekundärem organischen Aerosol bei variierenden Ladungszuständen zu quantifizieren. Schließlich werden die Ergebnisse dieser Experimente durch Messungen zur sekundären organischen Partikelbildung bei wohldefinierten Ionenkonzentrationen an einer Aerosolkammer überprüft. Die vorgeschlagene Forschungsagenda ist somit darauf abgestimmt, mögliche ladungs-katalysierte chemische Mechanismen bei der sekundären Aerosolbildung besser einzuordnen.
In the context of global change, marine organisms are subjected not only to gradual changes in abiotic parameters, but also to an increasing number of extreme events, such as heatwaves. However, we still know little about the influence of heatwaves on the structure of marine communities, and experimental studies are needed to test the impact of heatwaves alone, and in combination with other environmental drivers. Here, we conducted a mesocosm experiment and applied an integrated multiple driver design to assess the potential impact of heatwaves under ambient and future environmental conditions on natural coastal plankton communities. To represent future environmental conditions, temperature and pH were manipulated based on the Representative Concentration Pathway 8.5 proposed by the IPCC for 2100, and dissolved N:P ratios were increased to simulate the conditions expected in European coastal zones. Throughout the experiment, we measured abiotic conditions as well as the abundance of bacterioplankton, phytoplankton, and microzooplankton.
We experimentally manipulated the presence of light and light intensity (F = 36.7 μmol m⁻² s⁻¹; D = 0 μmol m⁻² s⁻¹; L = 4.8 μmol m⁻² s⁻¹; M = 21.4 μmol m⁻² s⁻¹) and tested their effects on the vertical positioning of the freshwater jellyfish (Craspedacusta sowerbii) medusae. For the experiments, approximately 100 C. sowerbii medusae were collected in August 2017 in two lakes (Haager Weiher and Leitner Weiher) in Bavaria, Germany. Testing was carried out at Seeon Limnological Station in close vicinity to the collection site. The experimental columns were 7.4 cm in diameter and 170 cm high and were marked with horizontal lines every 5 cm for visual position estimation. Four replicates run in parallel. One C. sowerbii medusa was used in each experimental column. Data cover three light treatments, each run twice: 1) 16:8 h full light (F)–dark (D) light intensity cycles (nF = 716, nD = 428), 2) 16:8 h full light (F)–full dark (D) light intensity cycles complemented with low (L) and medium (M) light intensities (nF = 96, nM = 96, nL = 48, nD = 288), and 3) altered light intensities in approximately 2-hour periods randomly among dark, low, medium, and full light intensities (nF = 96, nM = 76, nL = 72, nD = 336). Results show that light alone was sufficient to trigger a vertical position change of jellyfish towards the water surface, especially high light.
Cherry leaf roll virus (CLRV) is a plant pathogen of economic and ecologic importance. It is globally distributed in a wide range of forest, fruit, and ornamental trees and shrubs. In several areas of cherry and walnut production CLRV causes severe losses in yield and quality. With current reference to the rapid dissemination and strong symptom expression in Finnish birches and the Germany-wide distribution of CLRV in birches and elderberry, we continuously investigate and gradually reveal CLRV transmission pathways as by pollen, seeds or water. However, modes and interactions responsible for the wide intergeneric host transmission as well as for the exceptional CLRV epidemic in Fennoscandia still remain unknown. In this project systematic studies shall investigate biological vectors as a causal agent to finally derive control mechanisms and strategies to avoid new epidemics in different hosts and geographic regions. Detailed monitoring of the invertebrate fauna of birch stands/forests and elderberry plantations in Germany and Finland shall reveal potential vectors to subsequently study them in detail by approved virus detection methods and transmission experiments. Molecular analyses of the CLRV coat protein shall prove its role as a viral determinant for a virus/vector interaction. Consequently, this project essentially will contribute important answers on the CLRV epidemiology, and this will be a key element within the first network of research on plant viral pathogens in forest trees.
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