The adsorption of sulphate has been studied using alpine and sub-alpine podzolic soils from the Allt a'Mharcaidh catchment, Cairngorms, Scotland, U.K. A detailed investigation of sulphur pools and mechanisms of sulphur retention has revealed that incoming sulphate ion, both marine and anthropogenic, is being retained by a range of adsorption mechanisms. Analysis of the soils has indicated that the sulphur content of the soils is dominated by organic forms of sulphur. Selective chemical fractionation techniques have identified an accumulation of sesquioxides, dominated by amorphous aluminium, in the basal horizons of all the soil profiles. Adsorption of sulphate has been shown to be mainly governed by the quantity and variable charge character of this sesquioxide phase. Fractionation has also suggested that the sesquioxides in the basal horizons of the soils are dominated by a combination of gibbsitic and imogolitic materials, the latter being present as a result of podzolization processes. The generation of sulphate adsorption isotherms has revealed that the organic horizons of the catchment soils show little or no sulphate adsorption capacity, due to a small sesquioxide content. In contrast, the mineral horizons are all capable of adsorbing sulphate, and in most cases this adsorption can be modelled to the Langmuir adsorption equation. The adsorption capacity of particle size fractions of the soils has revealed that even soil particles > 1 mm show an ability to retain sulphate, possibly by physical entrapment of soil solution in mineral pores or amorphous silica gel coatings. The accompanying hydroxyl release that is generally assumed to accompany adsorption of sulphate in the mineral soils was not evident, and unless a ligand exchange reaction was masked by other chemical reactions involving total proton balance, sulphate adsorption in the catchment soils is not due to a specific or 'low affinity' specific mechanism.

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In this study the phase distribution of phosphorus (P) is examined in 7 Scottish East Coast rivers. Rivers with contrasting catchment properties were selected, including pristine highland rivers, lowland rivers with agricultural land use and a range of intermediate rivers. Suspended particulate matter (SPM) was rich in organic P and had total P contents in the range of 0.1 to 1%. Highest total P contents of particles were observed for the river richest in dissolved P. The pristine highland systems showed the lowest total P contents. Large increases in exchangeable P in summer were partly attributable to the presence of phytoplankton. Phytoplankton accounted for less than half and more typically around 20% of organic carbon in SPM. The remainder is likely to consist largely of amorphous, humic substances. Sorption properties (e.g. EPC₀, equilibrium phosphate concentration at zero adsorption) of SPM were examined using adsorption isotherms. Particle concentrations for sorption experiments were kept low (ca. 200 mg/l) to allow extrapolations to natural conditions. SPM from highland rivers showed the largest affinity for P. Lowland rivers displayed a comparatively low affinity for P. EPC₀ values of SPM closely reflected soluble reactive phosphorus concentrations in river water. SPM from highland and lowland rivers showed consistent differences in organic carbon content. Organic carbon content of SPM was correlated to sorption parameters of SPM. The sorption parameters of intermediate rivers could be explained by mixing particles of different affinity, using organic carbon contents to trace the proportions of particle mixing. Under estuarine conditions the affinity of fluvial SPM for P decreases. The magnitude of the change is insufficient to cause desorption in the pristine highland rivers. Up to 80-fold increases in EPC₀ were observed for the remaining rivers suggesting desorption takes place in the estuary.

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It was illustrated that Zn and Cu at or above 1000 and 800 mg kg^-1 respectively were highly toxic to the earthworm studied. Cu was found to be more toxic to the earthworm than Zn in respect to mortality, growth and reproduction parameters in all three different types of soils. The body burdens of earthworms exposed to metal amended soils increased corresponding to the increased concentrations of amended metals irrespective of soils used. It was found that the BCFs in earthworms decreased with the increased concentrations of metals in soils. The higher BCFs is the indication of uptake of higher proportion metals from soil by earthworms. The highest BCFs was found for Ni followed by Zn and Cu indicated their bioavailability to earthworms. The growth (weight) of the earthworms was most affected by Cu. The combined toxicity of Zn:Ni, Zn:Cu and Cu:Ni to reproduction (cocoon production) of earthworms was mainly antagonistic and to some extent additive in both the Insch and Boyndie soils. Zn was more toxic than Cu to the nematodes as the number of nematodes decreased with the increase of metal amendments to soil. It was also found that the number of nematodes increased at the exposure to some lower doses of Cu and Ni. The joint toxicity of Zn:Ni, Zn:Cu and Cu:Ni on the number of nematodes was mainly antagonistic in both the Insch and Boyndie soils. In some cases the combined toxicity of metals to nematodes was not possible to assess because the threshold level was not reached and also due to irregular and inconsistent data. Cruden Bay soil was more vulnerable than Insch and Boyndie soils in evaluating the toxicity of metals to nematodes. Zn was found to be toxic for the <i>lux</i>-marked bacterial biosensor <i>Escherichia coil</i> HB101 pUCD607 and <i>Pseudomonas fluorescens </i>10586r pUCD607 in different soils.

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