摘要:

Treatment with dilute hydrofluric acid, acid precipitation and washing, dialysis, and subfractionation with ultrafiltration membranes were used to prepare humic acids and two subfractions of them with barely detectable ash content. A soil and sediments from nine lakes in different areas and with different chemistry and trophic levles were so treated. Total losses of organic matter averaged 57 percent, with a range of 47 to 67 percent. Losses at each step were determined, the greatest being during ultrafiltration.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Five surface soils from southeastern Montana were studied to determine the influence of autoclaving, metabolic substrate additions, soil moisture status, and soil temperature on the volatilization of mercury from soils amended with methylmercury. Soils were amended to 1.0 part per million of mercury as203Hg-CH3HgCl, and the mercury content was monitored for two months by gamma spectrometry. Mercury losses were stimulated by higher soil temperatures and repressed by glucose and nitrate additions and by excessive moisture or dryness. Highest losses were observed from the strongly alkaline soils.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Soil-nitrification studies were made to examine the possible effect of fosamine ammonium salt (ammonium ethyl carbamoylphosphonate), the active ingredient in Du Pont Krenite brush control agent, on soil bacteria under laboratory conditions. When 0.5, 5, and 20 parts per million of fosamine ammonium were incorporated into two agricultural soils, no effect on the soil-nitrifying process could be found during a 5-week test period.Population and species of soil bacteria and fungi in three agricultural soils were found to be unaltered over an 8-week period after treatment with 10 parts per million of fosamine ammonium. In an agar plate bioassay test, fosamine ammonium showed little or no fungitoxicity at treatment rates up to 100 parts per million.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

We offer a technique to identify the pathways of solute movement down columns of sieved soil aggregates using fluorescent dyes and recording their presence by ultraviolet photography. Pyranine was found to be the most useful dye for short-term laboratory experiments because of its high fluorescence and comparatively low adsorption coefficient.The uneven distribution of pyranine across the Horizontal faces of successive soil sections, as shown by ultraviolet photography, indicated that the solute moved preferentially in some parts of the column. The technique was found to be value in checking the uniform packing of columns of soil aggregates and to have potential use under field conditions (Part 2).

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

A laboratory study was undertaken to test the hypothesis that sulfur is accumulating by sulfate adsorption in a mixed deciduous forest soil. Sesquioxide-rich subsurface soils had a large reservoir of phosphate-soluble, adsorb sulfate-S (2700 kilograms per hectare), but would not permanently adsorb more. Surface soils had no detectable adsorbed sulfate, but a substantial reserve of water-soluble sulfate-S(110 kilograms per hectare). Surface soils were also capable of adsorbing more sulfate into forms not extactable with water of phosphate solution.The high proportion of water-soluble sulfate appears to play an important role in determining sulfate concentrations in headwater streams. During peak storm flow periods, sulfate concentrations in headwater streams increase, and it is hypothesized that this is due to leaching from surface horizons in the variable source areas of the watershed.It is hypothesized further that the water-soluble sulfate pool in surface horizons is active in sulfur-cycling processes, whereas water-insoluble sulfate in subsurface horizons constitutes an inactive, long-term sulfur reserve.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

A simulation model describing water movement through field-cropped soils was developed. The soil water flow equation, which included a root extraction term, was approximated using a finite difference technique. Hydraulic conductivity (K) and diffusivity (D) functions were calculated by using the Millinton-Quirk technique. The chosen boundry conditions, rainfall, evapotranspiration, and a fluctuating water table approximated those existing in the field. Submodels to calculate interception, evaporation, and transpiration were included in the model. Model predictions were in good agreement with field data from a fairly uniform soil. On a soil containing discontinous clay varves the predictions were not satisfactory when the original calculatedKandDfunctions were used. Predicted and measured water content profiles were in closer agreement when theKandDfunctions were modified within the limits of the measured moisture retention curve data.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Infiltration from an intermittently flowing subsurface source of water is compared via numerical methods with a continous source.Though the intermittent source is flowing for only 50 percent of the time on a 4-h cycle, its cumulative infiltration is 80 percent of that for the continous source at 175 h after the initiation of flow. Furthermore, this latter percentage increases with time.This high value is caused by redistribution during no-flow conditions, when flow is reinitiated.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

As a consequence of a pipeline break, approximately 1.9 million liters of kerosene inundated 1.5 hectares of a New Jersey wheat field. After emergency cleanup operations, the hydrocarbon content of the contaminated field was assessed by coring, extraction, and quantitative gas chromatography. A rehabiliation program, consisting of liming, fertilization, and frequent tilling, was initiated, and the decrease of hydrocarbon contaminants in the soil was monitored for a 2-year period. Seed germination and yield data showed that the field returned to a near-normal and productive state 1 year after the spill. The hydrocarbon content of the surface soil decreased to an insignificant level 2 years after the spill. The disappearance rate of the hydrocarbon contaminants showed a definite correlation with the monthly temperature averages. In addition to the rehabiltation program, the oil type and the nature of the contaminated soil both contributed to the relatively rapid recovery of this field.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID