Phosphorus mobilization from various sediment pools in response to increased pH and silicate concentration

Phosphorus (P) release from sediment particles to the interstitial water has been studied extensively, but the contribution of different inorganic P pools in sediment under differing environmental conditions is not fully understood. This study was undertaken to get more detailed information about the chemical mobilization mechanisms. Phosphorus mobilization from reserves bound by Al, Fe, and Ca compounds in response to increased pH and to inorganic silicon (Si) enrichments was investigated using a sequential fractionation analysis and an isotope-labeling technique. The aerobic sediment of Lake Vesij?rvi had a high P retention capacity, and Fe-bound P was the largest inorganic P pool as well as the main source of released P. High Si addition (47 mg Si L-1 sediment) released more P to the interstitial water than did the elevation of pH from 6.6 to 9.5, since Si lowered the resorption of released P onto hydrated Al oxides. This finding reveals that P equilibrium between Fe-bound and Al-bound P in sediments regulates P net mobilization to the interstitial water under aerobic conditions. Furthermore, elevated pH combined with high Si enrichment had a positive synergistic effect, resulting in the most substantial P mobilization. This synergism may cause a self-fueled increase in the internal loading of P. It accentuates the effect of diatom sedimentation on P fluxes in eutrophic lakes with high pH and may favor the appearance of bloom-forming cyanobacteria.     

Enzymatic Degradation of Cellulose-Based Materials

The biodegradability of cellulose-based materials was compared in the standard Sturm test and by enzymatic hydrolysis. Trichoderma reesei culture filtrate, the purified enzymes endoglucanase I and II from T. reesei, and -glucosidase from Aspergillus niger were used in the experiments. The unpurified Trichoderma reesei culture filtrate was found to contain a mixture of enzymes suitable for cellulose degradation. However, when purified enzymes were used the right balance of the individual enzymes was necessary. The addition of -glucosidase enhanced the enzymatic hydrolysis of cellulose materials when both culture filtrate and purified enzymes were used. In the Sturm test the biodegradability of most of the cellulose materials exceeded 70% carbon dioxide generation, but, in contrast, the biodegradability of the highly substituted aminated cellulose and cellulose acetate was below 10%. The results concerning enzymatic hydrolysis and biodegradability were in good agreement for kraft paper, sausage casing, aminated cellulose, and cellulose acetate. However, diverging results were obtained with cotton fabric, probably as a result of its high crystallinity.     

Untersuchungen zur Wirkung von Magnesium-asparaginat auf den Magnesiumgehalt menschlicher Erythrocyten

The Science of Nature -     

Effects of experimental acidification on mobilisation of metals from sediments of limed and non-limed lakes

In order to study the influence of pH on the mobilisation of metals from lake sediments, intact sediment cores with overlying water were sampled from one lime treated lake and one acidified lake. The overlying water of two cores from each lake was successively acidified to pH 4.2 over a period of 3 months. In the acid treated samples from the limed lake, the initial concentrations of Al, Cd, Mn, Pb and Zn in the overlying water were generally lower and the final concentrations were higher than in the acid treated samples from the acidified lake. The labile inorganic fraction of Al (Al(i)) was increasingly dominating as pH decreased. Redox potential and pH in the sediment indicated that the upper two centimetres were involved in the exchange reactions. The experiment showed that mobilisation of metals from sediments can occur and the results indicated that mobilisation could contribute to increased concentrations of metals in lake water during reacidification of formerly lime treated lakes.     

Long-term study of 99Tc in the marine environment on the Swedish west coast

The activity concentration of (99)Tc in brown seaweed (Fucus vesiculosus and Fucus serratus) and seawater were analysed in samples collected in 1991, 1995 and 2001 at several stations along the Swedish west coast. In addition to these locations, a well-defined site (S?rdal, 56.76 degrees N, 12.63 degrees E) was included with (99)Tc activity concentration data in seaweed from 1967 to 2000. Over the years, the major source of (99)Tc in the coastal waters of western Sweden has been the radioactive liquid discharge from the nuclear fuel reprocessing plant in Sellafield (UK) transported via ocean currents in the North Sea. The (99)Tc activity concentration in seaweed at the S?rdal site increased from approximately 30 Bq kg(-1) up to 230 Bq kg(-1) (dry weight) between 1997 and 2000 due to the Sellafield EARP (Enhanced Actinide Removal Plant) discharges in 1995-1996, yielding an approximate transport time of 4-5 years between the Irish Sea and the Kattegat. Due to the very sharp gradient in (99)Tc concentration between the Baltic Sea and the North Sea, (99)Tc is presently one of the best transit tracers for the recent ventilation events in the Baltic Sea.     

Oxygen and Water Barrier Properties of Coated Whey Protein and Chitosan Films

Films of whey protein and chitosan acetic acid salt have lower oxygen permeability than, for example, ethylene-co-vinylalcohol under dry conditions, but water and water vapor seriously impair the gas barrier properties. To reduce the oxygen permeability at 90% relative humidity and the water-vapor transmission rate at 100% relative humidity, the films were coated with an alkyd, a beeswax compound, or a nitrocellulose lacquer. Permeability and transmission rate measurements were performed in accordance with standard methods and showed that the beeswax compound and the nitrocellulose were appropriate as water-vapor barriers. Overall migration to water was measured after 10 days exposure time, with the coated surface exposed to the water, showing that the alkyd-coated and the nitrocellulose-coated films were both below the safety limit for food contact. Water absorbency tests, performed by the Cobb method, showed that the films coated with the beeswax compound or with nitrocellulose lacquer exhibit lower absorbency than the alkyd-coated films.     

The Spatial and Temporal Variation of Measured Urban PM10 and PM2.5 in the Helsinki Metropolitan Area

We have studied particulate matter (PM) concentrations,PM₁₀ and PM_2.5, measured in an urban air qualitymonitoring network in the Helsinki Metropolitan Area during1997–1999. The data includes PM₁₀ concentrationsmeasured at five locations (two urban traffic, one suburbantraffic, one urban background and one regional backgroundsite) and PM_2.5 concentrations measured at twolocations (urban traffic and urban background sites). Theconcentrations of PM₁₀ show a clear diurnal variation,as well as a spatial variation within the area. Bycontrast, both the spatial and temporal variation of thePM_2.5 concentrations was moderate. We have analysedthe evolution of urban PM concentrations in terms of therelevant meteorological parameters in the course of oneselected peak pollution episode during 21–31 March, 1998.The meteorological variables considered included wind speedand direction, ambient temperature, precipitation, relativehumidity, atmospheric pressure at the ground level,atmospheric stability and mixing height. The elevated PMconcentrations during the 1998 March episode were clearlyrelated to conditions of high atmospheric pressure,relatively low ambient temperatures and low wind speeds inpredominantly stable atmospheric conditions. The resultsprovide indirect evidence indicating that the PM₁₀concentrations originate mainly from local vehiculartraffic (direct emissions and resuspension), while thePM_2.5 concentrations are mostly of regionally andlong-range transported origin.