摘要:

A selective dissolution method for the simultaneous quantitation of calcite and dolomite in soils is proposed. This method, which can be used for soil dolomite contents as low as 0.1% (wt/wt), retains the attractive characteristics of simplicity and nonreliance on specialized or expensive equipment, while reducing interferences from noncarbonate sources of Ca, Mg, and alkalinity inherent in previous extractive methods. The expected relative inaccuracy of the proposed method is 3% of the “true” soil calcite or dolomite content if any Ca contributed by gypsum is accounted for independently and if the content of magnesian calcite in the soil is very low.

ISSN:0038-075X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Acidic deposition and forest clear-cutting are disturbances that have resulted in increased, acidification of northeastern forest ecosystems. This study was conducted to evaluate whether acidification processes can significantly affect adsorption processes that are important in regulating sulfate transport and cycling in a Spodosol at the Hubbard Brook Experimental Forest, New Hampshire. The results of adsorption experiments demonstrated that small changes in solution pH have a large effect on sulfate adsorption characteristics of mineral soil at Hubbard Brook. The ability of the soil to remove sulfate from solution increased as the pH of the solution was decreased, with a maximum removal occurring at about pH 4.0. Through the use of initial mass isotherms, we determined that sulfate removal depended upon (1) the ability of the soil to partition sulfate between the soil and solution phases and (2) the amount of reactive native sulfate that is present in the soil. Our analysis demonstrated that both these soil properties depend strongly upon solution pH.

ISSN:0038-075X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

We studied the geomorphological, physical, chemical, and mineralogical properties of 24 soil pedons from montmorillonite-rich parent materials in the Coastal Plains of Alabama to explain their genesis and classification. Most of the geologic strata in the area consist of Upper Cretaceous and Eocene age, siliceous shaly sediments deposited in shallow marine or brackish waters. The soils are on nearly level to strongly sloping upland positions dissected by stream erosion. Most areas are in forest (loblolly pine and hardwoods), and some are in pasture. All soils have very low pH (3.7 to 5.0), clayey control sections (44.5 to 78.3%, clay), and montmorillonitic mineralogy. All but one have base saturation <35%. Despite the udic-thermic regime, the slowly permeable subsoils maintain the soil under water-saturated conditions for most of the year, thus allowing only limited leaching. The slow weathering rates under acid conditions, however, are adequate for pedogenic transformation of smectite to kaolinite, especially in the upper solum horizons. Classification at the subgroup level is based on drainage and expression of vertic properties, and at the series level on the depth to paralithic contact (Cr). Four soil series (Arundel, Halso, Conecuh, Beatrice) have been used to describe these soils. They meet the clayey, montmorillonitic, thermic family criteria, and they are in Typic, Aquic, or Vertic subgroups.

ISSN:0038-075X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

We used the pyrolysis-gas chromatography technique (Py-GC) to characterize mature and immature soil organic matter (PN soil: C/N = 24.8; PS soil: C/N = 12.6). PN produced on pyrolysis an abundance of furfural and phenol, indicating the presence of partially decomposed litter. PS, on the contrary, produced a considerable amount of benzene, which was consistent with a more mature humus.The extracts were fractionated in HAs and FAs and by membrane ultrafiltration, in fractionsA1(mol wt > 105), A2(>104), andR(<104). Extracts and relative fractions were characterized by Py-GC and isoelectric focusing (IEF).The elaboration of the relative abundances and several Py-GC ratios proved to be very appropriate in assessing differences or similarities among soils and their fractions.Independently of the maturity of soil humus, theA1s and HAs were carbohydrate-rich and composed of highly condensed humus; theRs were polyphenol-rich, less condensed, and similar to FAs; the A2s showed intermediate properties. IEF has proved a reliable technique for characterizing structurally different organic fractions.The IEF patterns of the fractions were charge-size depenedent, and, on the basis of the charge and heterogeneity, they supported the Py-GC results.

ISSN:0038-075X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

We measured hydraulic conductivity (K), bulk density, and humification of peat in three soil profiles at a spring fen-raised bog complex in the Lost River Peatland, northern Minnesota. Piezometers were installed at saturated depths ranging from 0.5 to 3.0 m on a raised bog, its external fen margin, and an adjacent spring fen, and fieldKwas determined by time-lag methods. FieldKranges from 2.5 x 10−4to 5.6 x 10−3cm/s on the bog, from 1.5 x 10−3to 2.6 x 10−2cm/s at the fen margin, and from 6.7 x 10−4to 1.6 x 10−2cm/s on the spring fen. TheKdetermined for partially decomposed peat deeper than 1 m is 2 to 6 times greater than previously reported in the literature. There appears to be little correlation ofKwith depth, as suggested by most other workers who have investigated only the uppermost “active‘’ layer, about 50 cm deep. Laboratory analyses ofKfrom peat cores show that the ratio of horizontalK(Kh) to verticalK(Kv) is highly variable throughout the peat column.Khis generally one to two orders of magnitude greater thanKv.Bulk density values are similar to those found for other moderately decomposed peats in Minnesota, ranging from 0.06 to 0.14 g/cm3. Bulk density and humicity do not statistically correlate with depth or withKfor the peats in the Lost River Peatland.This study suggests that humified peat can transmit groundwater more rapidly than previously thought and that the interaction between groundwater in the peat and associated surface waters can be significant.

ISSN:0038-075X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Microflora (bacteria and fungi) distributions in several paleosols from Mount Kenya, East Africa, provide important information about contamination of buried soil horizons dated by radiocarbon. High counts of bacteria and fungi in buried soils provide evidence for contamination by plant root effects or groundwater movement. Profiles with decreasing counts versus depth appear to produce internally consistent and accurate radiocarbon dates. Profiles with disjunct or bimodal distributions of microflora at various depths produce internally inconsistent chronological sequences of radiocarbon-dated buried surfaces. Preliminary results suggest that numbers up to 5 x 102g−1for fungi and 5 x 103g−1for bacteria in buried A horizons do not appear to affect the validity of14C dates. Beyond this threshold value, contamination appears to produce younger dates, the difference between true age and14C age increasing with the amount of microflora contamination.

ISSN:0038-075X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

We determined the relative mobility of Rb+in four similar soils of different structural types by replicated undisturbed and constructed soil columns (repacked). The soils are designated as Cumulic Haplustolls, fine-loamy, mixed, thermic. The soils have similar mineralogical composition and are classed as sandy clay loams. The structural types of the soils were (1) weak, coarse prismatic; (2) moderate, angular blocky; (3) moderate, medium subangular blocky; and (4) moderate, medium granular. Rubidium concentrations were determined in solutions withdrawn via ceramic cups at different depths and times and in sectioned column extracts at the conclusion of the experiment. The data show that Rb+moved 1.4 to 1.6 times deeper in the soils with coarse structural units and that there were no significant differences between the soils with medium-sized structural units and the constructed soil columns.

ISSN:0038-075X    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

We studied the spatial variability of soil temperature along an 80-m transect on a bare field on an Olivier silt loam soil. We measured soil temperature at 68-cm intervals along the transect and at various soil depths. The spatial structure of temperature data was examined by semivariograms and autocorrelograms. Except for 20− and 30-cm soil depths, which exhibited a pure nugget effect, the temperature observations were found to be spatially interdependent. Moreover, a significant trend emerged for temperature measurements at the 10-cm soil depth. The semivariograms exhibited a nugget effect as much as 50% of sample variance. A spherical model was found to describe the overall shape of the semivariograms. The autocorrelation length obtained from a first-order autoregressive model with a white noise was found to describe the spatial structure of the soil temperature and gave results comparable to those obtained from the sphere of influence of semivariograms. The spatial structure was found at two scales: first a spatial dependency at small scale, manifested by the range of influence and autocorrelation length and not exceeding 25 m; and a second spatial structure at relatively larger scale, manifested by periodic behavior in temperature observation at 25 and 50 m.

ISSN:0038-075X    

出版商:OVID    

年代:1986

数据来源: OVID