Polycyclic aromatic hydrocarbons (PAH) in different forest humus types

The behavior of 20 PAH in the organic layers of a L mull, an Of mull and a mor was assessed by a combined approach of a soil profile study, and the analysis of particle-size separates. Increasing PAH concentrations with depth in the mor profile (L, 866 μg kg⁻³; Of, 2902 μg kg⁻¹; Oh, 10489 ug kg⁻¹) were assigned to selective enrichment during organic matter decomposition. PAH were further highly enriched within the finer separates. For the L horizons, significant positive correlations were established between the enrichment of individual PAH (as observed from the decomposition gradient between the >2-mm fraction and the < 0.05-mm fraction), and the K_OW for each compound. The slope of the regression line, m, described the degree of differentiation between low- and high-molecular PAH during litter decomposition. Since m was greatest in the most biologically active humus type (L mull, 0.33) and smallest in the most inactive (mor, 0.20), microbial breakdown was assumed as the dominating process for this differentiation. The results also indicated that decomposition processes had already taken place in the L horizons, leading to morphological and chemical changes of organic matter, and to an enrichment of high molecular PAH.     

Managing the cooling capacity of the upper rhine: A case study

In most industrialized countries, environmental standards exist which prescribe the maximum allowable man-made increase in water temperature of a river. Together with flowrate and weather conditions, these standards determine the rate at which waste heat may be discharged into a river at any moment. Power generating stations with variable cooling systems can adjust their heat discharge into the river in compliance with environmental standards and by doing so exert an influence on power generation capacity. In this paper, a scheme is developed that allows a chain of power stations discharging into the same river to operate their cooling systems such that the output of total electricity is maximized and water temperature standards are accomodated. The optimum balance between stations is determined through dynamic programming. From the results of a simulation model using historical data, simple decision rules for day-to-day operation are abstracted. These rules are based solely on the river flow rates at each power station.     

Homing pigeons (<Emphasis Type="Italic">Columba livia</Emphasis> f. <Emphasis Type="Italic">domestica</Emphasis>) can use magnetic cues for locating food

An experimental group of homing pigeons (Columba livia f. domestica) learned to associate food with a magnetic anomaly produced by bar magnets that were fixed to the bowl in which they received their daily food ration in their home loft; the control group lacked this experience. Both groups were trained to search for two hidden food depots in a rectangular sand-filled arena without obvious visual cues; for the experimental birds, these depots were also marked with three 1.15 × 10⁶ μT bar magnets. During the tests, there were two food depots, one marked with the magnets, the other unmarked; their position within the arena was changed from test to test. The experimental birds searched within 10 cm of the magnetically marked depot in 49% of the test sessions, whereas the control birds searched there in only 11% of the sessions. Both groups searched near the control depot in 11 and 13% of the sessions, respectively. The significant preference of the magnetically marked food depot by the experimental birds shows that homing pigeons cannot only detect a magnetic anomaly but can also use it as a cue for locating hidden food in an open arena.     

Succinate-bonded pullulan: An efficient and reusable super-sorbent for cadmium-uptake from spiked high-hardness groundwater

Chemically modified pullulan was evaluated for its sorption efficiency and selectivity to remove cadmium(Cd) from spiked high-hardness groundwater(GW). Pullulan esterified with succinic anhydride using dimethylaminopyridine showed a fairly high degree of substitution value as confirmed by1 H NMR spectroscopy. Pullulan succinate(Pull-Suc) was converted into the sodium salt(Pull-Suc-Na). The effect of contact time(5–200 min) and p H(2–8) on Cd-uptake by the sorbent(Pull-Suc-Na) was investigated. The sorbent showed more than 90% Cd-removal in first 15 min from distilled water(DW) and GW solution,respectively. Comparison of Pull-Suc-Na with other polysaccharidal sorbents suggested its high efficiency(DW 476.2 mg/g and GW 454.5 mg/g) and selectivity for the removal of Cd by an ion exchange mechanism, which is further supported by the negative Gibbs free energy values calculated from Langmuir isotherms. A Langmuir isotherm kinetic model provided the best fit for the sorption of Cd using Pull-Suc-Na. The sorbent showed a negligible decrease in Cd-uptake over three regeneration cycles. The thermal stability testing of the sorbents indicated that Pull-Suc-Na(sorbent) is more stable than Pull-Suc.