PHENOLIC HYDROLYSIS PRODUCTS FROM GEL CHROMATOGRAPHIC FRACTIONS OF SOIL HUMIC ACIDS

Humic acids extracted from the Bh horizon of a kauri (Agathis australis) podzol and the A horizon of a yellow-brown earth under hard beech (Nothofagus truncata), both New Zealand soils, were fractionated by a ‘salt boundary’ technique using a dextran gel, and the fractions hydrolysed with 6 M hydrochloric acid. Lignin-derived phenolic acids were analysed by gas chromatography of the ether-soluble hydrolysis products of the humic acids. The lignin derivatives from the kauri podzol humic acid are probably modern products derived from the present-day scrub vegetation, whereas those from the yellow-brown earth humic acid are derived from the deciduous vegetation.     

Distribution coefficients of Cd, Co, Ni, and Zn in soils

Batch adsorption experiments were conducted with a mixture of solutes at low equilibrium concentrations of Cd (0.7-12.6 μg1⁻¹), Co (18-118μg1⁻¹, Ni (22-330 μg 1⁻¹), and Zn (40-1480 μg1⁻¹) in 38 different soils. Statistical correlations indicated that metal sorption onto the soils was influenced by the presence of clays and hydrous oxides of Fe and Mn. Based on calculated distribution coefficients for these metals, Co will generally exhibit the highest mobility in soils, but the mobility of Zn will increase faster with decreasing pH. Two types of empirical relationships are developed from these data to estimate values for the distribution coefficients.     

SULPHUR, CARBON, AND NITROGEN CONTENTS OF ORGANIC FRACTIONS FROM ACETYLACETONE EXTRACTS OF SOILS

Ultrasonic dispersion of acid-pretreated soils in aqueous acetylacetone at pH 8, and at a solvent: soil ratio of about 45: I, extracted from 61 to 97 per cent of the organic sulphur from five Scottish soils. Narrowing the ratio to about 9:1 reduced the proportion extracted but was more convenient for the subsequent isolation of the organic components. Gel permeation chromatography of the extracts yielded materials containing from 14 to 60 per cent of the soil organic sulphur. Most of the soils gave four distinct fractions which contained from 21 to 38 per cent carbon, 0.2 to 2.1 per cent nitrogen, and 0.1 to 0.8 per cent sulphur. There was no consistent similarity between corresponding fractions of the various soils. Considerable amounts of iron and aluminium were extracted, presumably incorporated in organic complexes. Since they were obtained under very mild conditions, the fractions should provide useful starting materials for qualitative investigations on the nature of soil organic sulphur.     

Comparison of the Hydrological Budgets and Detailed Hydrological Responses in Two Forested Catchments

Detailed hydrological budgets for two mature forested catchmentsshow very similar inputs and vegetational throughputs (throughfalland stemflow) for both Norway and Sitka spruce. Stream outflow,equivalent to 1707 mm, is comparable both with measured rainfallinputs (2250 mm) or rainfall in combination with throughfalland stemflow (1826 mm). Soil throughflow from the differingsoil profiles follows similar patterns, in both soil types withinitial flow response at depth (>50 cm). This may increasetowards a maximum for some horizons, and, depending on inputamounts, be followed by a transfer of flow up through the profile.Hydrological responses and their effect on soil temperatureswere again similar at both sites, with no obvious anomalieswhich would explain the resultant differences in stream chemistrybetween these catchments. The observed changes in surface waterchemistry must therefore be primarily due to vegetational orsoil induced chemical processes combined with observed differencesin hydrological fluxes.