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Cerro I.,University of the Basque Country | Antiguedad I.,University of the Basque Country | Srinavasan R.,Texas A&M University | Sauvage S.,Ecolab | And 2 more authors.
Journal of Environmental Quality | Year: 2014

The study area (Alegria watershed, Basque Country, Northern Spain) considered here is influenced by an important alluvial aquifer that plays a significant role in nitrate pollution from agricultural land use and management practices. Nitrates are transported primarily from the soil to the river through the alluvial aquifer. The agricultural activity covers 75% of the watershed and is located in a nitrate-vulnerable zone. The main objective of the study was to find land management options for water pollution abatement by using model systems. In a first step, the SWAT model was applied to simulate discharge and nitrate load in stream flow at the outlet of the catchment for the period between October 2009 and June 2011. The LOADEST program was used to estimate the daily nitrate load from measured nitrate concentration. We achieved satisfactory simulation results for discharge and nitrate loads at monthly and daily time steps. The results revealed clear variations in the seasons: higher nitrate loads were achieved for winter (20,000 kg mo-1 NO3-N), and lower nitrate loads were simulated for the summer (<1000 kg mo-1 NO3-N) period. In a second step, the calibrated model was used to evaluate the long-term effects of best management practices (BMPs) for a 50-yr period by maintaining actual agricultural practices, reducing fertilizer application by 20%, splitting applications (same total N but applied over the growing period), and reducing 20% of the applied fertilizer amount and splitting the fertilizer doses. The BMPs were evaluated on the basis of local experience and farmer interaction. Results showed that reducing fertilizer amounts by 20% could lead to a reduction of 50% of the number of days exceeding the nitrate concentration limit value (50 mg L-1) set by the European Water Framework Directive. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Source

Wissenbach D.K.,Helmholtz Center for Environmental Research | Wissenbach D.K.,University Hospital Jena | Winkler B.,Helmholtz Center for Environmental Research | Otto W.,Helmholtz Center for Environmental Research | And 14 more authors.
Air Quality, Atmosphere and Health | Year: 2016

Inhalation is one of the entry ports for different chemicals into the human body. In order to investigate this application route and its negative health effect to humans, the presence of volatile organic compounds (VOCs) in indoor air is monitored since many years. To assess global trends and changes of the distribution and disposition of VOCs and the corresponding personal exposure, this study analyzed annual indoor air concentrations collected over a period of 9 (2006–2014) years in the context of a birth control cohort study of 72 VOCs. Additionally, Short Time-series Expression Model (STEM) was used to identify certain correlation for VOCs from different compound classes. For ~42 % of the compounds, a tendency to lower annual median indoor air concentrations was found, and for ~10 % of the VOCs, a trend to higher annual median indoor air concentrations. No such tendencies were observed for ~22 % of the investigated compounds. For ~26 % of the VOCs, the applied linear regression model was not suitable to predict global trends as annual median values were not linearly distributed. Mann-Kendall test was used to (i) confirm the results from the linear regression model and to (ii) calculate trends for those compounds, where linear regression was found to be unsuitable. Thus, for only approximately four of the investigated VOCs, no prediction was possible using both statistical approaches. STEM analysis revealed the connection of benzene, ethylbenzene, m+p xylene, α-pinene, 3-carene, pentadecane, and decamethlycyclopentasiloxane, in addition to the correlation of 1-butanol, chlorobenzene, heptanal, and 2-ethyl-1-hexanol concentrations. © 2016 Springer Science+Business Media Dordrecht Source

Worrich A.,Helmholtz Center for Environmental Research | Worrich A.,elmholtz Center for Environmental Research | Konig S.,Helmholtz Center for Environmental Research | Miltner A.,elmholtz Center for Environmental Research | And 10 more authors.
Applied and Environmental Microbiology | Year: 2016

Fungal mycelia serve as effective dispersal networks for bacteria in water-unsaturated environments, thereby allowing bacteria to maintain important functions, such as biodegradation. However, poor knowledge exists on the effects of dispersal networks at various osmotic (Ψo) and matric (Ψm) potentials, which contribute to the water potential mainly in terrestrial soil environments. Here we studied the effects of artificial mycelium-like dispersal networks on bacterial dispersal dynamics and subsequent effects on growth and benzoate biodegradation at ΔΨo and ΔΨm values between 0 and-1.5 MPa. In a multiple-microcosm approach, we used a green fluorescent protein (GFP)-tagged derivative of the soil bacterium Pseudomonas putida KT2440 as a model organism and sodium benzoate as a representative of polar aromatic contaminants. We found that decreasing ΔΨo and ΔΨm values slowed bacterial dispersal in the system, leading to decelerated growth and benzoate degradation. In contrast, dispersal networks facilitated bacterial movement at ΔΨo and ΔΨm values between 0 and-0.5 MPa and thus improved the absolute biodegradation performance by up to 52 and 119% for ΔΨo and ΔΨm, respectively. This strong functional interrelationship was further emphasized by a high positive correlation between population dispersal, population growth, and degradation. We propose that dispersal networks may sustain the functionality of microbial ecosystems at low osmotic and matric potentials. © 2016, American Society for Microbiology. Source

Pavlichenko V.V.,Russian Academy of Sciences | Protopopova M.V.,Russian Academy of Sciences | Timofeyev M.,Irkutsk State University | Luckenbach T.,elmholtz Center for Environmental Research
Environmental Science and Pollution Research | Year: 2015

The fauna of Lake Baikal in Eastern Siberia, the largest freshwater body on Earth, is characterized by high degrees of biodiversity and endemism. Amphipods, a prominent taxon within the indigenous fauna, occur in an exceptionally high number of endemic species. Considering the specific water chemistry of Lake Baikal with extremely low levels of potentially toxic natural organic compounds, it seems conceivable that certain adaptions to adverse environmental factors are missing in endemic species, such as cellular defense mechanisms mitigating toxic effects of chemicals. The degree to which the endemic fauna is affected by the recently occurring anthropogenic water pollution of Lake Baikal may depend on the existence of such cellular defense mechanisms in those species. We here show that endemic amphipods express transcripts for Abcb1, a major component of the cellular multixenobiotic resistance (MXR) defense against toxic chemicals. Based on a partial abcb1 cDNA sequence from Gammarus lacustris, an amphipod species common across Northern Eurasia but only rarely found in Lake Baikal, respective homologous sequences were cloned from five amphipods endemic to Lake Baikal, Eulimnogammarus verrucosus, E. vittatus, E. cyaneus, E. marituji, and Gmelinoides fasciatus, confirming that abcb1 is transcribed in those species. The effects of thermal (25 °C) and chemical stress (1–2 mg L−1 phenanthrene) in short-term exposures (up to 24 h) on transcript levels of abcb1 and heat shock protein 70 (hsp70), used as a proxy for cellular stress in the experiments, were exemplarily examined in E. verrucosus, E. cyaneus, and Gammarus lacustris. Whereas increases of abcb1 transcripts upon treatments occurred only in the Baikalian species E. verrucosus and E. cyaneus but not in Gammarus lacustris, changes of hsp70 transcript levels were seen in all three species. At least for species endemic to Lake Baikal, the data thus indicate that regulation of the identified amphipod abcb1 is triggered within the general cellular stress response. This is the first report presenting molecular data on a MXR transporter in amphipods, an ecotoxicologically important but with regard to gene sequence data comparatively little explored taxon. © 2014, Springer-Verlag Berlin Heidelberg. Source

Becker J.M.,elmholtz Center for Environmental Research | Becker J.M.,RWTH Aachen | Liess M.,elmholtz Center for Environmental Research | Liess M.,RWTH Aachen
Proceedings of the Royal Society B: Biological Sciences | Year: 2015

The genetic recovery of resistant populations released from pesticide exposure is accelerated by the presence of environmental stressors. By contrast, the relevance of environmental stressors for the spread of resistance during pesticide exposure has not been studied. Moreover, the consequences of interactions between different stressors have not been considered. Here we show that stress through intraspecific competition accelerates microevolution, because it enhances fitness differences between adapted and non-adapted individuals. By contrast, stress through interspecific competition or predation reduces intraspecific competition and thereby delays microevolution. This was demonstrated in mosquito populations (Culex quinquefasciatus) that were exposed to the pesticide chlorpyrifos. Non-selective predation through harvesting and interspecific competition with Daphnia magna delayed the selection for individuals carrying the ace-1R resistance allele. Under non-toxic conditions, susceptible individuals without ace-1R prevailed. Likewise, predation delayed the reverse adaptation of the populations to a non-toxic environment, while the effect of interspecific competition was not significant. Applying a simulation model, we further identified how microevolution is generally determined by the type and degree of competition and predation. We infer that interactions with other species—especially strong in ecosystems with high biodiversity—can delay the development of pesticide resistance. © 2015 The Authors. Source

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