A comparative study of three methods of water removal prior to resin impregnation of two soils

Abstract

The water in replicate samples from sub-surface horizons of a clayey and a fine-silty soil was removed either by oven-drying, freeze-drying or by acetone-replacement prior to resin impregnation. Pore space photograms (pores >60 pm diam.) from thin sections were analysed on a Quantimet 720 image analysing computer following each drying technique. During oven-and freeze-drying the clayey soil contracted considerably and subsequently satisfactory impregnation of these samples was either difficult or impossible. This macro-shrinkage caused a decrease in number and lengths of most planar pores and a decrease in size and number of all intra-aggregate pores. The loss in pore space and continuity obviously affected resin impregnation. The clayey samples in which water was replaced by acetone, and all samples of the silty soil, however pretreated, showed no measurable macro-shrinkage and all impregnated well. Oven-drying the silty soil appears to increase the porosity, causing an increase in size of all pores. A mechanism for this apparent enlargement is proposed. It is evident that acetone-replacement of the soil water prior to resin impregnation is the best of the three methods used here and should be seriously considered when image analysis is to be carried out on resin-impregnated blocks from soils of similar or related textures.Brown (IOYR 513) clay; many fine prominent strong brown (7.5YR 518) and greyish brown (IOYR 512) mottles; moist; moderately developed fine and medium angular blocky with smooth shiny brown (IOYR 513) ped faces; stoneless; abundant fine pores; common former fine root paths outlined in greyish brown; firm; very plastic. very sticky.Hamble (TL7 11673 1/30-39 cm, Eb horizon) Yellowish brown to brown (10-7.5YR 514) silt loam to silty clay loam; many medium dark brown (7.5YR 412) mottles; occasional inclusions of light yellowish brown and dark greyish brown (IOYR 412); moist; weakly developed medium angular blocky; few very small flints; abundant very fine macropores; rare fine roots; friable; common earthworms.The particle size distribution analyses of both horizons are as follows (sand 2 mm to 60 pm; silt 60-2 pm; clay < 2 pm):Windsor: sand 6 per cent, silt 35 per cent, clay 59 per cent. Hamble: sand 16 per cent, silt 66 per cent. clay I8 per cent. SamplingLedges of I x 2 m dimension were exposed at 46 cm depth in the Windsor soil and at 35 cm depth in the Hamble soil. Sixty Kubiena tins, each 7.5 x 6 x 4 cm were inserted into each ledge in groups of three so that large (7.5 x 6 cm) horizontallyoriented thin sections could be prepared. The samples from each group were x e d for oven-drying, freeze-drying and acetone-replacement respectively. Pre-treatmentOven-drying. The soil samples were placed in an oven set at 40°C and leR for 2 weeks before resin impregnation.

Effects of design and kinematic parameters of rotary cultivators on soil structure

“…This was done before and after the passage of the rotary cultivator, and after the passage of the sowing machine. The samples were dried at 40 °C and, according to Murphy (1982), for a low content of clay and organic matter, this low temperature ensures the departure of water without altering soil structure. When dried, the samples were impregnated in a vacuum with the aim that the resin fill the smallest pores possible.…”

Quantification of soil macro pore size and shape using resin impregnation

“…The resin mixture produced for New Zealand conditions had a low viscosity to ensure infiltration into the smallest pores, as well as being able to set when there was some moisture present. To ensure curing of the resin mixture, cores were collected when soil moisture was below and near field capacity and left in a well-ventilated room for 24 h before resin application, allowing for some moisture loss while preventing shrinkage and cracking (Murphy 1982). The method of resin impregnation is more expensive and labour intensive than some traditional methods of measuring soil structure, but offers the advantage of more detailed assessment of soil pore size and shape.…”

Micromorphology of archaeological deposits

“…Existe uma extensa bibliografia disponível sobre secagem e impregnação de amostras de solos para estudos micromorfológicos (Brewer 1964;Conway 1982;Murphy 1982Murphy , 1985Murphy , 1986Castro 1985;Chartres et al 1989;Moran et al 1989;de Paula et al 1991;Carter 1993;Fitzpatrick 1993;Filizola;Gomes 2004), que pode guiar nos procedimentos mais adequados de acordo à natureza das amostras. Não obstante, sempre é recomendável coletar blocos inalterados (1)0 termo "fábrica'' é definido por Bullock et aí.…”

“…Na maioria dos laboratórios a secagem das amostras se realiza ao ar durante aproximadamente 48 horas, ou até que o peso se tome constante, e na estufa a temperatura baixa (40Q C no máximo) até a amostra secar completamente. Este procedimento de secagem é altamente eficiente em areias ou siltes que não sofrem encolhimento na estufa, mas para materiais muito orgânicos ou ricos em argilas expansivas, que na estufa sofreriam severas diminuições no seu volume2 com produção de gretas artefatuais, é recomendado o uso de acetona, especialmente na sua forma liquida, para substituir a água nos poros prévia à impregnação das amostras (para maior informação sobre secagem por substituição com acetona ver Murphy 1982Murphy , 1985Murphy , 1986Conway 1982;Chartres et al 1989;Moran et al 1989;Carter 1993).…”