The use of volcanic soil as mineral landfill liner--I. Physicochemical characterization and comparison with zeolites.

The main physicochemical characteristics of the volcanic soil of Southern Chile, with allophane as the main pedogenic mineral phase were analysed and compared with common zeolites (clinoptilolite) of the European market. The ultimate goal of this study was to test volcanic soil for the use as mineral landfill liner. The main results indicated that the clay and silt fractions together of the volcanic soil were between 38 and 54%. The buffering capacity of the volcanic soil was higher compared with the studied zeolites, whereas the cationic exchange capacity of the volcanic soil (between 5.2 and 6.5 cmol + kg(-1)) is of the same order of magnitude of the studied zeolites (between 9.7 and 11.4 cmol + kg(-1)). Moreover, the anionic exchange capacity of the volcanic soil was higher compared to the zeolites analysed. The hydraulic conductivity of the volcanic soil, measured in the laboratory at maximum proctor density, ranges between 5.16 x 10(-9) and 6.48 x 10(-9) m s(-1), a range that is comparable to the value of 4.51 x 10(-9) m s(-1) of the studied zeolite. The Proctor densities of the volcanic soil are in a lower range (between 1.11 and 1.15 g ml(-1)) compared with zeolites (between 1.19 and 1.34 g ml(-1)). The volcanic soil physicochemical characteristics are comparable to all the requirements established in the Austrian landfill directive (DVO, 2000). Therefore, the use as mineral landfill basal sealing of the analysed volcanic soil appears reasonable, having a pollutant adsorption capacity comparable to zeolites. It is of special interest for Southern Chile, because there are no alternative mineral raw materials for basal liners of landfills.     

Hormonaktive Xenobiotika

Developmental and reproductive processes are most sensitive to the toxic effects of environmental chemicals. Especially alarming is the fact that many groups of industrial chemicals and pesticides are capable of disrupting the endocrine system in man and animals. Of great concern is the reduction in the sperm count in Europe, but also the worldwide increase in a great number of reproductive and developmental disturbances observed in both man and wildlife. A correlation to a high chemical burden has been demonstrated for many different animal species as well as for women. An important consideration in assessing the potential effects of environmental chemicals on the endocrine system is the time at which such an exposure occurs. In the adult organism, hormones initiate functional processes; these effects are usually transient. In early life, hormones control developmental processes and are capable of producing permanent changes in organ structure and function (organizational effects). Therefore, chemical disruption of hormonal functions during development can result in permanent functional changes of the afflicted organ.     

Genetic engineering for practical application

Genetic engineering has ushered in a new era in biology. Although many problems are still to be solved, there are examples that point to a possible later application for the benefit of mankind: Bacteria can be manipulated to degrade crude-oil spillages, to produce human insulin and to bind nitrogen from the air. If all the bacteria that are indigenous to agricultural soils could be made to bind nitrogen, an increase in soil fertility might well result.     

Operating characteristics of a fabric filter on a peaking/cycling boiler without auxiliary preheat or reheat

A fabric filter has been on-line for one year on a coal-fired boiler that is primarily a peaking unit within the power schedule. For the first six months, Eastern Kentucky coal with 2.5% sulfur was the fuel source for 30% of the time, with low-sulfur Montana coal constituting the remaining fuel during the operation period. Bag life has been excellent with no bag failures reported to date, and the pressure drops have been low. There has never been an auxilliary heat source to preheat the fabric filter for start-up, nor to reheat the fabric filter when operating at reduced load with associated low back-end temperatures. Conclusions are that the filter cake formed does protect the bags from blinding at low load conditions, and a special acid-resistant finish applied to the glass fibers protects the bags when high-sulfur coal is burned at low temperatures. Overall, this installation provides an excellent data base for cycling service and high-sulfur coal usage with a fabric filter.     

Food-exchange by foragers in the hive – a means of communication among honey bees?

Dancing and trophallactic behaviour of forager honey bees, Apis mellifera ligustica >Spinola, that returned from an automatic feeder with a regulated flow rate of 50% weight-to-weight sucrose solution (range: 0.76–7.65 μl/min) were studied in an observation hive. Behavioural parameters of dancing, such as probability, duration and dance tempo, increased with the nectar flow rate, though with very different response curves among bees. For trophallaxis (i.e. mouth-to-mouth exchange of food), the frequency of giving-contacts and the transfer rate of the nectar increased with the nectar flow rate. After unloading, foragers often approached other nest mates and begged for food before returning to the food source. This behaviour was less frequent at higher nectar flow rates. These results show that the profitability of a food source in terms of nectar flow rate had a quantitative representation in the hive through quantitative changes in trophallactic and dancing behaviour. The role of trophallaxis as a communication channel during recruitment is discussed. Received: 14 January 1995/Accepted after revision: 14 August 1995