Reconstructing the Development of Baltic Sea Eutrophication 1850–2006

A comprehensive reconstruction of the Baltic Sea state from 1850 to 2006 is presented: driving forces are reconstructed and the evolution of the hydrography and biogeochemical cycles is simulated using the model BALTSEM. Driven by high resolution atmospheric forcing fields (HiResAFF), BALTSEM reproduces dynamics of salinity, temperature, and maximum ice extent. Nutrient loads have been increasing with a noteworthy acceleration from the 1950s until peak values around 1980 followed by a decrease continuing up to present. BALTSEM shows a delayed response to the massive load increase with most eutrophic conditions occurring only at the end of the simulation. This is accompanied by an intensification of the pelagic cycling driven by a shift from spring to summer primary production. The simulation indicates that no improvement in water quality of the Baltic Sea compared to its present state can be expected from the decrease in nutrient loads in recent decades.     

Selective metal removal from chromium-containing synthetic effluents using Shewanella xiamenensis biofilm supported on zeolite

Environmental Science and Pollution Research - A scheme of selective removal of metal ions from chromium-containing synthetic solutions with the following chemical composition, Cr (VI)-Fe (III), Cr...     

Metabolic and Environmental Control on Methane Emission from Soils: Mechanistic Studies of Mesotrophic Fen in West Siberia

The biological mechanisms regulating methane emission fromnatural wetlands are the focus of this article. A novel techniqueprovides estimates of the distribution of CH₄ sources withinan undisturbed soil profile by recording the transient gasdynamics after soil enclosure by deep (50 cm) chamber. Thecombined use of conventional surface and soil chambers across a200-m fen transect allowed us to relate the observed methaneemission to its instant generation and uptake. Surprisingly, themethane generation was relatively constant (9–12 mg CH₄-C hr^-1 m^-2) and highly variable net emission (0.2–20 mg CH₄-C hr^-1 m^-2) was closely correlated (r = –0.809)with methane uptake. In laboratory incubations, CH₄ uptakefollowed Michaelis-Menten kinetics. Added chloride and nitrateirrespective of the cation's nature suppressed uptake as a strongnoncompetitive inhibitors (K _i 0.5 mM). The methaneformation turned out to be unstable and under anaerobicincubation, the formation of CH₄, CO₂ andH₂displayed sustained weekly oscillations. We conclude that effectsof environmental factors alone are not sufficient topredict the variation in emission, which depends also on metabolic control of respective soil organisms. The multitude ofsuch controls is dependent on diversity of respective soilorganisms and could be grouped into a limited number ofcategories considerably simplifying large-scale simulations.     

Humic-like substances extracted from composts can promote the photodegradation of Irgarol 1051 in solar light

Humic-like substances (HLS) were extracted from a mixture of sewage sludges and trimmings (70-30%, w/w) after different times of composting (0, 70 days and 130 days). HLS were analyzed by elemental analysis, UV-visible and fluorescence spectroscopy and also tested for their ability to photosensitize the degradation of Irgarol. The rate of Irgarol photodegradation in artificial solar light was found to be 2.5- to 4.3-fold higher in the presence of HLS than in buffered Milli-Q water. These results were confirmed by experiments in solar light that evidenced the photodegrading properties of HLS in a more striking way. Using 2-propanol as hydroxyl radical scavenger, we could show that hydroxyl radicals contributed to the photosensitized Irgarol degradation for about 25%. The photodegrading activity of HLS, their absorbance and their emissive properties were all found to increase between 0 and 70 days of composting and to remain quite constant between 70 and 130 days. The degree of humification varied in the same way, linking all these properties to the humification process.     

Modeling water exchange and contaminant transport through a Baltic coastal region

The water exchange of the Baltic coastal zone is characterized by its seasonally varying regimes. In the safety assessment of a potential repository for spent nuclear fuel, it is important to assess the consequences of a hypothetical leak of radionuclides through the seabed into a waterborne transport phase. In particular, estimates of the associated residence times in the near-shore coastal zone are of interest. There are several methods to quantify such measures, of which three are presented here. Using the coastal location of Forsmark (Sweden) as an example, methods based on passive tracers, particle trajectories, and the average age distribution of exogeneous water parcels are compared for a representative one-year cycle. Tracer-based methods can simulate diffusivity more realistically than the other methods. Trajectory-based methods can handle Lagrangian dispersion processes due to advection but neglect diffusion on the sub-grid scale. The method based on the concept of average age (AvA) of exogeneous water can include all such sources simultaneously not only boundary water bodies but also various (fresh)-water discharges. Due to the inclusion of sub-grid diffusion this method gives a smoother measure of the water renewal. It is shown that backward in time trajectories and AvA-times are basically equipollent methods, yielding correlated results within the limits set by the diffusivity.