Hysteresis in Reversal of Central European Mountain Lakes from Atmospheric Acidification

Extremely high emissions of S and N compounds in Central Europe (both 280 mmol m^-2 yr^-1) declined by 70and 35%, respectively, during the last decade. Decreaseddeposition rates of SO₄ ^-2, NO₃ ^-, and NH₄ ⁺ in the region paralleled emission declines. The reduction in atmospheric inputs of S and N to mountain ecosystemshas resulted in a pronounced reversal of acidification in the Tatra Mountains and Bohemian Forest lakes. Between the 1987–1990and 1997–1999 periods, concentrations of SO₄ ^-2 and NO₃ ^- decreased (average ± standard deviation) by 22±7 and 12±7 mol L^-1, respectively, in theTatra Mountains, and by 19±7 and 15±10 mol L^-1, respectively, in the Bohemian Forest. Their decrease was compensated in part (1) by a decrease in Ca²⁺ + Mg²⁺ (17±7 mol L^-1) and H⁺ (4±6 mol L^-1), and an increase in HCO₃ ^-(10±10 mol L^-1) in the Tatra Mountains lakes, and (2) by a decrease in Al (7±4 mol L^-1), Ca²⁺ + Mg²⁺ (9±6 mol L^-1), and H⁺ (6±5 mol L^-1), in Bohemian Forest lakes. Despite the rapid decline in lake water concentrations of SO₄ ^-2 and NO₃ ^- in response to reduced S and N emissions, their present concentrations in some lakes are higher than predictionsbased on observed concentrations at comparable emission rates during development of acidification. This hysteresis in chemical reversal from acidification has delayed biological recovery of the lakes. The only unequivocal sign of biological recovery hasbeen observed in erné Lake (Bohemian Forest) where a cladoceran species Ceriodaphnia quadrangular has recentlyreached its pre-acidification abundance.     

Imaging of water flow in porous media by magnetic resonance imaging microscopy

Magnetic resonance imaging (MRI) was used to study the flow of water in a column 14 mm in diameter packed with glass heads. The sample was fully saturated and water was pumped through the column using a peristaltic pump, at flow rates of 125 and 250 mL h(-1). This corresponds to mean velocities of 0.5 and 1 mm s(-1), given a porosity of 0.46 m3 m(-3). Nuclear magnetic resonance (NMR) images of the proton density and velocities within a 2-mm slice were taken at a spatial resolution of 0.15 x 0.15 x 2 mm3. At a mean pore water velocity of 1 mm s(-1) we approximated hydrodynamic dispersion using NMR-measured velocity distributions in a 2-mm slice through the sample. Additionally, we conducted a step pulse tracer experiment with chloride through the same column and at identical initial and boundary conditions. We fitted the convection-dispersion equation to the breakthrough curve and compared the column scale dispersion of the tracer experiment with the respective NMR estimate derived at the slice scale.     

Bewertungsverfahren Verfahren zur Bewertung von immissionsbedingten Stoffanreicherungen in standardisierten Graskulturen

Standardized grass cultures are routinely used to evaluate the accumulation of air pollutants. For the assessment of air pollutant accumulation in grass cultures, it is particularly important to distinguish between “normal” concentrations and the significantly increased accumulation caused by air pollution. This article presents a method to determine “normal” element concentrations (background levels) and define threshold values for the significantly elevated accumulation of pollutants for individual series of grass cultures. By applying the same method for the data from six regional air quality measuring programs, it was possible to derive universally applicable “normal” concentrations and threshold values for grass cultures. The described method is not limited to the evaluation of data from grass cultures but is also suitable for other biological or ecological data. It allows to distinguish between “normal” element concentrations and unusually high or low concentrations.     

Carbon/electron source dependence of polychlorinated biphenyl dechlorination pathways for anaerobic granules

The effect of acclimating anaerobic granules from commercial bioreactors with different carbon/electron sources on their ability to reductively dechlorinate a tri-(2,3,4-CB) and heptachlorobiphenyl (2,2',3,3',4,5,6-CB) was studied. The anaerobic granules were first grown in upflow anaerobic sludge blanket (UASB) reactors fed with two different mixtures of carbon/electron sources, i.e., propionate/butyrate/methanol and formate/methanol. Differences in dechlorination patterns for 2,2',3,3',4,5,6-CB were observed in batch experiments inoculated with granules from these two sets of UASB reactors. Variation of the carbon/electron source, during the dechlorination process, had no effect on the dechlorination pathway, but the extents and rates of dechlorination were highest for ethanol and formate and lowest for pyruvate fed batches. Pre-acclimation of different anaerobic sludges to polychlorinated biphenyls (PCBs) shortened the lag period, but did not influence the PCB dechlorination pathway. This is the first time that similar acclimation conditions for several anaerobic microbial communities prior to inoculation were reported to yield similar substrate specificities for the reductive dechlorination of specific PCB congeners. This research demonstrates a successful strategy for the development of biocatalysts to serve as the inoculum of partially decontaminated sites in order to provide microorganisms with specificities complementary to those of naturally occurring dechlorinators.     

A Knowledge-Based Approach to the Assessment of Watershed Condition

The Ecosystem Management Decision Support (EMDS) system is an application framework for knowledge-based decision support of ecological assessments. EMDS integrates geographic information system and knowledge base system technologies to provide an analytical tool for environmental assessment and monitoring. The basic objective of EMDS is to improve the quality and completeness of environmental assessments and the efficiency with which they are performed. The USDA Forest Service and the U.S. Environmental Protection Agency have cooperatively developed an EMDS knowledge base for watershed condition assessment. Specifically, this knowledge base evaluates watershed processes, patterns, general effects of human activity, and fisheries habitat suitability. Such assessments are based on spatially explicit input data concerning current conditions and reference conditions which are subsequently interpreted by user-defined "fuzzy" membership functions. In this paper we describe basic components of our knowledge base for assessing watershed condition and illustrate its application within northern Idaho and northwestern Montana.     

Adjustment formulae for maternal serum alpha-fetoprotein,human chorionic gonadotropin,and unconjugated oestriol to maternal weight and smoking

Serum levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and un-conjugated oestriol (uE3) were measured in serum samples of 4131 non-smoking and 1018 smoking women during the second trimester of pregnancy. The levels of all three analytes decreased with increasing body weight. The AFP median was significantly increased in smokers in a dose-response association; hCG decreased by 21 per cent and uE3 decreased by 3 per cent in smokers in a non-dose-related fashion. Regression functions for adjustment of serum levels for weight and smoking should be considered in risk estimation for Down syndrome in order to give a woman's individual risk more precisely.