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For a shallow aquifer and a fully penetrating stream, the ideal baseflow curve does not plot as a straight line on semilog paper, and its recession rate continuously decreases with time. For a deep aquifer and a shallow-entrenched stream, the ideal baseflow generally decays exponentially, and its recession rate decreases with increasing stream entrenchment. In the case of loss from evapotranspiration, the baseflow curves steepen progressively with time, and the stream may become influent. In the case of gain from confined aquifers, the baseflow curves become flatter. The recharge results in shifting of the baseflow curves upward in magnitude or laterally in time. The baseflow peak occurs at about 0.75 T from the beginning of recharge to the aquifer, where T denotes the effective duration of recharge. The lag between the total flow peak and the baseflow peak depends on rainfall, soil, and basin factors. The variability of these factors precludes the notion of a constant lag. [ABSTRACT FROM AUTHOR]

It has been known for many years that the eating of leaded paint is the prime cause of lead poisoning and elevated blood leads of children living in deteriorated housing. Recently, there has been speculation that children may eat dirt and dust contaminated with lead exhausted from cars and that this amount of ingested lead is sufficient to contribute significantly to the childhood lead problem. This paper reports on a twopart study conducted to evaluate the validity of the dirt-and-dust hypotheses. The first part of the study was made to determine the source of lead in dirt to which children are normally exposed. Dirt samples were taken in old urban areas around 18 painted frame houses and 18 houses of brick construction. Samples also were taken around seven old frame farmhouses remote from traffic. Based on the fact that lead concentrations in the dirt were similar in city and rural yards at corresponding distances from the houses, it is clear that nearly all of the lead in dirt around these houses is due to paint from the houses. Lead antiknock additives are therefore not a significant contributor to the lead content of dirt around houses where children usually play. The second part of the study used a naturally occurring radioactive tracer (210)Pb to determine the relative amounts of dust and other lead-containing materials (e.g., paint) eaten by young children. This tracer is present in very low concentrations in paint and in significantly higher concentrations in fallout dust. Stable lead and (210)Pb were analyzed in fecal material from eight children suspected of having elevated body burdens of lead and ten children living in good housing where lead poisoning is not a problem. The normal children averaged 4 mug Pb/g dry feces, with a range of 2 to 7. Of the eight children suspected of having elevated lead body burdens, two had fecal lead values within the normal range. However, the remaining six were 4 to 400 times as high. Despite these differences in fecal lead between the two groups, the groups were essentially identified in the (210)Pb content of their feces. The "elevated" children averaged 0.040 pCi of (210)Pb dry feces, while the normal group averaged 0.044 pCi/g. The results provide sound evidence that these children suspected of elevated lead body burden were not ingesting dust or air-suspended particulate.

The major exobiological problem is the detection of life on other planets. The present paper presents experimental data on gas exchange between different samples of terrestrial soils and the atmosphere. The feasibility of applying the gas chromatographic technique to the detection of extraterrestrial life is discussed.

A letter to the editor is presented about the optical properties of fabrics.

The effect of 35 herbicides on the nitrification process was tested both by experiment, and by simulation of possible mechanisms of inhibition in a mathematical model. The model consists of nine equations with six coordinated constant and seven measurable parameters (or initial values), depending on the specific soil. The only free parameters are the initial values of the oxidative enzyme systems, and the parameters which determine the course of possible inhibition effects. For the majority of the herbicides, the inhibitory effects on the NH or NO oxidation were found negligible in the range of practical application. Hypotheses of a completely reversible or partially reversible inhibition of the oxidase systems gave the best correspondence between the model and reality, while an alteration of the growth parameters of the nitrifying populations in the model (death rate, proliferation rate, initial kill) due to the application of herbicides led to strong contrasts between simulated and experimental curves. Significant inhibitory effects became evident only when the hydrogen ion concentration in the soil fell below pH 7. Results with several herbicides indicated that the process of NO oxidation was more sensitive than that of NH oxidation. With a number of herbicides, an accumulation of NO ions was noticed during the course of soil percolation. In consideration of the buffering capacity, the model is applicable to other soils. [ABSTRACT FROM AUTHOR]

Diphenamid (N,N-dimethyl-2,2-diphenylacetamide) in an aqueous solution in plastic bottles was partially detoxified when exposed to sunlight for 1 week. Varying spray volumes from 300 to 1,800 I/ha did not have an appreciable effect on the phytotoxicity of diphenamid, sprayed on a coarse or fine soil surface. The marked dissipation of diphenamid which occurred from the soil surface was attributed to photodecomposition and volatilization. Diphenamid phytotoxicity was greater when the first irrigation after spraying was applied in four increments of 100 m/ha or two increments of 200 m/ha than when it was applied in a single 400 m/h watering; the latter caused more leaching of the herbicide. The diphenamid fraction leached out of a 4-cm soil layer increased as the organic matter content in the soil decreased, from 25% in peat (22.3% o.m.) to >88% in sandy loam (0.9% o.m.). The herbicidal activity remaining after leaching was lower in sandy loam and in peat than in soil with medium organic matter content (11.6% and 6.2%). Diphenamid degradation rate in soil at 50% field capacity moisture level, increased when temperature was increased from 10° to 30°C. After 4 months of incubation at 10°C, 40-50% of the original herbicide was detoxified, while at 20° and 30°C the loss exceeded 90%. Within the range of day-temperatures of 10° to 40°C in soil and of 10° to 35°C in nutrient solution, diphenamid phytotoxicity to tomato seedlings increased with temperature. [ABSTRACT FROM AUTHOR]

The equation of transient flow through a porous medium is dependent upon both the permeability and compressibility of the matrix, two properties that are highly temperature dependent. By formulating this dependence, it is possible to predict the behavior of a consolidating mass subject to specific constant temperature levels. This analysis is extended to predict transient flow behavior for conditions of temperature variations in a given sample, using numerical methods. Temperature increases induced either before or after dissipation of the excess hydrostatic pressure influence the rate of consolidation by increasing the rate of pore pressure dissipation and decreasing the ability of the matrix to assume the stress. An experimental program was established to study the effect of boundary temperature increases on a stressed-saturated clay after pore pressure dissipation. Temperature increases caused immediate volume changes, the magnitudes being primarily dependent upon the magnitude of the temperature change. The magnitude of the initial stress (pore-pressure excess) was seen to have a secondary effect on the magnitude of the volume change. These volume changes are attributed to a transfer of stress between the pore fluid and the matrix, as the increases in temperature increase the pore pressure but decrease the matrix strength. [ABSTRACT FROM AUTHOR]

A new apparatus for studying miscible displacement processes in soils is described. Both the soil water content and the pore water velocity can be controlled within certain ranges. The usefulness of this technique is illustrated by a brief description of: (1) the mixing of Cl− during miscible displacement in a glass bead medium; (2) the movement and adsorption of Atrazine, a herbicide, in soil; and (3) the movement and microbiological nitrification of NH4+−N to NO3−−N during unstaturated flow conditions in soil. [ABSTRACT FROM AUTHOR]

The article reports on the release of pentachlorophenol from pentachlorophenyl laurate due to hydrolysis caused by microbial activity. To prove this hypothesis, a perfusion system was used to experiment on textile samples which are the cotton fabric treated with pure pentachlorophenyl laurate perfused with nutrient salt solution and one treated in exhausted nutrients, metabolic wastes and breakdown products. Both are inoculated with soil. Result shows that hydrolysis of pentachlorophenyl laurate was due to a purely chemical effect caused by a biological activity in the soil.