Biodegradation of estrogens in stream water

Estrogens of human and animal origin that reach the aquatic environment may enter human or animal organism and act as endocrine disruptors.To investigate the persistency of estrogens in laboratory experiments, estrone respectively 17beta-estradiol were added to stream water sampled from river Spree in Berlin. The concentration of estrone and 17beta-estradiol was quantified using enzyme-immuno-assay. The estrone concentration decreased to less than 5 % of the starting concentration at storage temperature of 5 degrees C within 56 days and at storage temperature of 20 degrees C within 14 days. If the estrone were added to autoclaved stream water, no biodegradation was observed. Biodegradation was enhanced when activated sludge was added. Escherichia coli, Pseudomonas fluorenscens and Aeromonas hydrophila in monoculture did not degrade estrone in autoclaved stream water.The concentrations of 17beta-estradiol and estrone decreased similarly.The logistic function proved to be suitable to describe the course of time for the decrease of concentration.     

Effects of grazing and rainfall variability on root and shoot decomposition in a semi-arid grassland

Overgrazing increasingly affects large areas of Inner Mongolian semi-arid grasslands. Consequences for ecosystem functions and, in particular, for the decomposition as a key process of ecosystem carbon (C) and nitrogen (N) cycling are still unclear.We studied the effects of grazing on shoot and root decomposition with the litter bag method in a long-term grazing exclosure (UG79), a moderate winter grazed (WG) and a long-term heavily grazed site (HG). We separated the effects of local environmental factors and litter quality as altered by grazing. Growing seasons of average and very low precipitation allowed us to study the effect of inter annual rainfall variability on decomposition.Grazing-induced differences in environmental factors of the three studied grassland sites had no effect on decay rates of shoot and root dry mass. Also differences in litter quality among the grazing sites were not reflected by root decomposition dynamics. The accelerated shoot decay at site HG could not clearly be linked to litter quality parameters. Shoot decay rates were more or less constant, even under very dry conditions. This indicates the possibility of photodegradation (solar UV-B radiation) to control aboveground decomposition in this semi-arid ecosystem. By selecting the best predictors of root decomposition from regression analysis, we found that soil water content was the best parameter explaining the dynamics.Net N immobilization was generally not detected during the decay process of shoot and root. It is likely, when root decomposition is strongly reduced in dry periods, shoot decomposition becomes relatively more important for nutrient cycling. A separate analysis of shoot and root decay dynamics is required in order to describe C and N cycling in this semi-arid grassland. The grazing impact on C and N fluxes through decomposition of plant material likely exhibits a strong interaction with seasonal rainfall pattern.     

Metabolism of naturally occurring [13C]glucose given orally to horses

In 5 horses, 13CO2/12CO2 ratios in expired air were determined using isotope mass spectroscopy to investigate metabolism of naturally occurring [13C]glucose. Oral glucose tolerance tests (OGTT) were performed using maize or beet glucose. Maize has a higher 13C concentration than that of most plants. The 13CO2/12CO2 ratios after OGTT was performed using maize glucose were compared with 13CO2/12CO2 ratios in expired air after OGTT was performed using beet glucose. The ratio also was determined during the period horses were not fed. Using OGTT, all horses were glucose tolerant. The OGTT performed using beet glucose led to minimal changes in 13CO2/12CO2 ratios. The 13CO2/12CO2 ratios decreased significantly (P less than 0.01) when horses were not fed. After oral dosing with maize glucose, 13CO2/12CO2 ratios reached maximal increases 5 hours after dosing and reached baseline values 15 hours after dosing.