Influence of plants on the methane emission from sediments

The previous theory [Chem. Global Change Sci. 3 (2001) 33; Chemosphere 50 (2003) 191] of methane emission is applied to vegetated sediments. The presence of roots in a sediment is taken into account. It is assumed that methane and nitrogen enter a sediment through channels existing in plants and roots. The rate of methane and nitrogen transport through plants and roots is proportional to the difference in concentrations in the layer and on the upper surface. It is established that as the vegetation density increases, the rate of methane transport increases so that with sufficient vegetation density, almost all methane passes to the atmosphere through plants. In this case, the value of bubble emission decreases to zero. The nitrogen transport rate through plants first increases and then decreases with increasing the vegetation density. The theory qualitatively and quantitatively describes the dependence of methane concentration on depth in the presence of plants. A comparison with the available experimental data on dissolved methane concentration and bubble composition indicates satisfactory agreement.     

Bronchial dosimeters for radon progeny for Chinese males and females

Bronchial dosimeters have been designed for adult Chinese males and females for home and mine exposures, which can give the bronchial doses from radon progeny by direct measurements. The bronchial dosimeter for home exposures consists of five 400-mesh wire screens. With a sampling face velocity of 3.3 cm s(-1) for Chinese males and 2.7 cm s(-1) for Chinese females, the deposition pattern on the wire screens were found to satisfactorily match the variation of the dose conversion coefficients (in units of mSv WLM(-1)) with the size of radon progeny from 1 to 1000 nm. The bronchial dosimeter for mine exposures consists of four 250-mesh wire screens. With a sampling face velocity of 3.3 cm s(-1), the deposition pattern on the wire screens were found to satisfactorily match the variation of the dose conversion coefficients for both Chinese males and females. In this way, the bronchial dosimeters directly give the bronchial doses from the alpha counts recorded on the wire-screens.     

90Sr migration to the geo-sphere from a waste burial in the Chernobyl exclusion zone

Results are presented from an ongoing field-scale experimental study (namely the Chernobyl Pilot Site project) aimed at characterization of processes controlling (90)Sr releases from a shallow trench containing nuclear fuel particles, and subsequent radionuclide transport in the underlying sandy aquifer at the Chernobyl nuclear power plant site. Microscopic analyses of waste material and leaching experiments have shown that 10-30% of the radioactive inventory is associated with chemically extra-stable Zr-U-O particles. The largest fraction of (90)Sr activity in the trench ( approximately 30-60%) is currently associated with relatively slowly dissolving non-oxidized UO(2) matrix fuel particles. The (90)Sr migration velocity in the eolian sand aquifer is retarded by sorption to approximately 9% of groundwater flow velocity (K(d) approximately 2 ml/g). The dispersivity values for non-reactive solute transport in the aquifer predicted by geostatistics (i.e. 0.8 6 cm) were confirmed by a natural gradient tracer test using (36)Cl. The observed negative correlation between hydraulic conductivity and K(d) of aquifer sediments suggests that (90)Sr could be subjected to larger dispersion in the subsurface compared with (36)Cl.     

239+240Pu, 90Sr and 137Cs inventories in surface soils of Vietnam

Fallout 239+240Pu, 238Pu, 90Sr and 137Cs inventories in surface soils were measured for 20 locations in northern Vietnam yielding the mean values (+/- standard error) of 26.5+/-3.8 Bq m(-2) for 239+240Pu, 1048+/-143 Bq m(-2) for 137Cs and 212+/-28 Bq m(-2) for 90Sr. The concentrations of 137Cs and plutonium isotopes strongly correlate with each other resulting in a stable 239+240Pu/137Cs inventory ratio of 0.025+/-0.002. Among soil parameters, organic matter and fulvic acids strongly correlate with caesium and plutonium isotopes, especially in the 0-10 cm layer. 137Cs and 239+240Pu are distributed rather similarly over the 0-10 cm and 10-20 cm layers. At locations with high contents of sand (82-93%) along the South China Sea coast, the downward percolation by rainwater results in a higher accumulation of 239+240Pu and 137Cs in the 10-20 cm layer. The mean 137Cs/ 90Sr inventory ratio is 9.3+/-2.2, and the correlation is weak between these isotopes.     

Lake fish as the main contributor of internal dose to lakeshore residents in the Chernobyl contaminated area

Two field expeditions in 1996 studied 137Cs intake patterns and its content in the bodies of adult residents from the village Kozhany in the Bryansk region, Russia, located on the shore of a drainless peat lake in an area subjected to significant radioactive contamination after the 1986 Chernobyl accident. The 137Cs contents in lake water and fish were two orders of magnitude greater than in local rivers and flow-through lakes, 10 years after Chernobyl radioactive contamination, and remain stable. The 137Cs content in lake fish and a mixture of forest mushrooms was between approximately 10-20 kBq/kg, which exceeded the temporary Russian permissible levels for these products by a factor of 20-40. Consumption of lake fish gave the main contribution to internal doses (40-50%) for Kozhany village inhabitants Simple countermeasures, such as Prussian blue doses for dairy cows and pre-boiling mushrooms and fish before cooking, halved the 137Cs internal dose to inhabitants, even 10 years after the radioactive fallout.     

Sensory influence upon grasshopper stridulation

The Science of Nature -     

Provisioning behavior and the estimation of investment ratios in a solitary bee,Calliopsis (Hypomacrotera) persimilis (Cockerell) (Hymenoptera: Andrenidae)

Summary One aspect of behavioral ecology that has received considerable attention, especially by students of social insects, is the relative amount of energy invested by parents in the rearing of male versus female offspring. Sexual selection theory makes predictions about how individuals should allocate their total investment in the sexes. To test these predictions we must accurately quantify the relative cost incurred by a parent in the production of an average individual of either sex. Body weight ratios are the most common estimate of cost ratio, but the correspondence between offspring body weight and energetic investment on the part of the parent has rarely been determined. Calliopsis (Hypomacrotera) persimilis is a solitary, ground-nesting bee whose natural history makes it particularly convenient for studies of investment patterns and foraging behavior. Each day females construct and provision from 1 to 6 cells in linear, closely-spaced series. Each cell is provisioned with pollen from Physalis Wrightii flowers, which is collected on two or three foraging trips. However, the temporal sequence in which two- and three-trip foraging bouts occur is not random. Females invariably begin each day provisioning cells with three trips worth of pollen and usually switch to provisioning the latter cells of the day with just two trips worth of pollen. The sex of the offspring within the same co-linear series of cells also varies non-randomly — female offspring predominate in the first cells of each series and male offspring in the latter cells. The correspondence between the number of foraging trips to provision a cell, the total time spent foraging, and offspring sex was determined for 36 cells. The data indicate a close, though not absolute, relationship between the number of foraging trips and the sex of the offspring: males usually received two trips of pollen, though some received three, whereas female offspring invariably received three trips worth of pollen. A number of potential estimates of the relative cost of female and male offspring production were calculated. Estimates of the cost ratio based on the amount of time spent foraging, adult dry body weight, and pollen ball dry weight all give similar values. Female offspring receive an energetic investment of from 1.3 to 1.5 times that of males. These results support the use of adult dry body weight ratios in the estimation of cost ratios.