Hamish A. Anderson

Evidence for enhanced atmospheric sulphate interception by Sitka spruce from evaluation of some Scottish catchment study data

Abstract Recent environmental controversy has focused on the role of forestry practices in stream acidification, with conflicting claims regarding interception mechanisms, altered site hydrology, etc. While it is generally accepted that there are strong correlations between some parameters, for example aluminium in stream water and coniferous afforestation, there is less consensus on the reaction of trees to pollutants with consequences on the crucial production and mobility of anions, especially sulphate. Examination of data from Scottish studies has shown that Sitka spruce is capable of intercepting atmospheric SO 2 , leading to accumulations of excess sulphate in tree foliage. This sulphate is readily soluble and when leached by rainfall produces increases in tree throughfall sulphate concentrations in Sitka spruce compared with other species.

Separation and determination of oligomers and homologues of aliphatic alcohol ethoxylates in textile lubricants and lubricant emulsion by high-performance liquid chromatography

Abstract Homologous mixtures of 3,5-dinitrobenzenoates of aliphatic alcohol ethoxylates (AEs) were separated by high-performance liquid chromatography (HPLC) with high resolution using an amino bonded silica column and gradient elution of ternary solvents (hexane-dichloromethane-methanol). When the method was combined with novel sample clean-up and extraction procedures, oligomers of AEs in textile lubricants and a lubricant emulsion were satisfactorily determined with recoveries 75% and good reproducibility. A reversed-phase HPLC method was also developed to characterise the alkyl groups of AEs.

The role of sea-salts in enhancing and mitigating surface water acidity

Enhancement of the acidity of fresh waters due to sea-salt “episodes” has been reported in western regions of Scotland, Ireland and Norway and eastern regions of Canada and the United States of America. In all cases these short-term pH depressions have been ascribed to cation-exchange processes in catchment soils whereby sodium ions displace acidic cations (H+, Al3+) resulting in a lowering of the Na/Cl ratio in run-off water. Studies of sea-salt episodes in different catchment types of similar sensitivity in Scotland show significant variations in chemical responses, especially in terms of acidification status. Catchments with high background salt content, in a low sulphur deposition area, show only a small increase in acidity with negligible aluminium release and most of the sodium retention matched by Ca and Mg release. Catchments in intermediate deposition areas, with low background salt levels, exhibit smaller sodium retention with increased leaching of acidity and labile aluminium. High non-marine S deposition sites, with intermediate background salt levels, reveal high levels of acidity and aluminium leaching associated with some calcium leaching and evidence of Mg retention. Mitigation of acidification occurs at sites with high background sea-salt levels (eg north west Scotland) where acidic deposition is selectively retained in catchment soils. Non-marine sulphate values in run-off are therefore much lower (often producing negative values) than those predicted from current S deposition values. Consequently such sites are presently producing false exceedances of freshwater Critical Loads when current S deposition values are used. Future reductions in S deposition will probably affect the adsorption characteristics at these sites with consequent effects on sulphate leaching.

Assessment of wet deposition mechanisms in an upland Scottish catchment.

A network of collectors were installed at various altitudes and degrees of exposure in the Allt a Mharcaidh catchment, northeast Scotland, in an attempt to obtain an accurate assessment of wet deposition loading. Results indicate that the quantity and quality of bulk deposition is constant over the whole catchment. “Enhancement deposition” as measured by a filter-gauge interception collector indicated that there was greatest deposition at altitude. The concentrations of all elements, except for hydrogen, were greater than that of catchment bulk deposition at the higher altitudes; at lower altitude enrichment was only appreciable for sodium and chloride. Input/output chloride budgets were used to assess catchment evapotranspiration rates and the relative proportions of enhancement deposition within different altitudinal ranges. The calculation gives a catchment evapotranspiration of 18.5% and a chloride enhancement deposition 2.5 times greater at higher altitudes than at lower altitudes. Rainfall chemistry in this high-level Cairngorm catchment appears independent of the positioning of the rainfall collectors. Different altitudes within the catchment receive an additional loading due to enhancement deposition, dependent upon the frequency of cloud/mist cover. This additional loading must be included in the assessment of total catchment loadings and in the calculation of evapotranspiration.

Organic acids from the anaerobic decomposition of Agropyron repens rhizomes.

Abstract Phytotoxicity originating from the anaerobic decomposition of couch grass rhizomes has been studied. Short chain aliphatic (acetic, propionic and butyric) acids appear to be mainly responsible but hexanoic, succinic, phenylacetic, cinnamic, p -coumaric, 4-hydroxyphenylpropionic and 3,4-dihydroxyphenylpropionic acids are also present in the phytotoxic solutions formed during the decomposition.

Humic substances of surface waters litter and soil throughflow relationships in two forested ecosystems

Abstract Humic substances were isolated from the vegetation throughfall, soil drainage waters and adjacent stream waters at two forested sites in the Central Region of Scotland. Fractionation on XAD-8 hydrophobic resin gave three humic substance components and one hydrophilic acid fraction. Norway spruce generally gave 2–3 times more dissolved organic carbon in the litter drainage compared with Sitka spruce, although there was little qualitative difference in organic acidity between the two litterflows. The humic substances in the drainage at ca. 1 m depth (BC horizon) showed considerable differences between sites, reflecting the types of soils and sources of soil water. Phenolic acids released on hydrolysis confirm the differences between sites and may indicate the sources of subsoil water and their relationships with the stream outputs.

Separation of broadly distributed nonylphenol ethoxylates and determination of ethylene oxide oligomers in textile lubricants and emulsions by high-performance liquid chromatography

A simple and rapid high-performance liquid chromatography method is described for separation and determination of ethoxylated nonylphenols. By using an amino bonded silica column with an acetonitrile-water gradient, the oligomers of ethoxylated nonylphenols with an average of 6 EO (ethylene oxide number) up to 40 EO were separated with satisfactory resolution. It was found that the partition of solutes between the stationary and mobile phases, and hydrogen bonding between solutes, solid-phase amino groups, water and acetonitrile were the main factors governing separation. The recoveries of total oligomers of nonylphenol-8 EO from a mixed emulsion with mineral oil, methyl oleate, peanut oil and the textile lubricant Blend 1 were 90.0±10.2, 95.6±7.9, 90.0±9.5 and 107.2±11.4%, respectively. The application of this method can be extended to determine non-ionic surfactants in other matrices.

Temporal changes in soil properties at an upland Scottish site between 1956 and 1997

The aim of this study was to examine the frequency with which soil samples require to be taken in order to determine significant temporal changes in soil properties. The examination was carried out using data from Glensaugh Research Station in north-east Scotland where podzolic soils were sampled in 1956, 1977 and 1997, and by re-analysis of archived material. Significant differences in chemistry due to storage were detected, particularly decreases in pH of air-dried organic soils. In these cases original data were used for statistical analysis to establish changes between 1956 and 1997. Temporal changes were found for exchangeable Ca and Mg which generally decreased with time throughout the soil profile, whereas exchangeable H increased. Derived data, such as percent base saturation, declined dramatically due to decreases in exchangeable base cations. Similar podzolic soils were sampled at an adjacent Environmental Change Network (ECN) site in 1993. Application of statistical techniques to the ECN soil chemistry data allowed an estimation of the detectable change between any two years. These data along with the rates of temporal change from 1956 to 1997 allowed the calculation of the number of years required for measurable changes to be achieved. These changes and sampling intervals vary among different horizons and chemistries. Although they are site-specific, they do confirm that the current ECN protocols of a 5-year and 20-year sampling would be appropriate in order to detect changes in soil properties over time at this site.

Hydrological and hydrochemical fluxes through vegetation and soil in the Allt a' Mharcaidh, western Cairngorms, Scotland: Their effect on streamwater quality

Abstract A detailed investigation of the hydrochemical alteration of input water by vegetation and soils was undertaken in an upland catchment in the Cairngorm Mountain region of Scotland. The composition of catchment outflow water reflects the hydrological routing of water through different soil horizons and the importance of long residence time water. There is uptake of nitrogen and neutralization of incoming anthropogenic acidity by the vegetation, and sulphate adsorption in the mineral soils. Streamwater quality is dominated by the contribution of long residence time water, especially during base flow. Sulphate retention and cation release are the major neutralization mechanisms buffering outflow chemistry at this site.

The relationship between salmonid fish densities and critical ANC at exceeded and non-exceeded stream sites in Scotland

The critical load concept is now accepted throughout Europe as a means of estimating the sensitivity of key components of aquatic and terrestrial ecosystems to atmospheric inputs of sulphur (S) and nitrogen (N). Current UK freshwater maps, based on steady-state water chemistry, are derived using a critical acid neutralising capacity (ANCLIM) value of zero μeql−1, which is based on the probability of occurrence of salmonid fish in lakes. In practice most acidification damage to salmonid fish occurs in nursery streams at the emergence and first feeding stages. In general a clear relationship exists between salmon (Salmo salar L.) and trout (S. trutta L.) densities in Scottish streams and ANC values. However, differences between sites depend on which ANC value is used (eg maximum, minimum or mean). By contrast, when the exceedance of critical loads is compared with salmonid densities the relationship is less clear because many exceeded sites have good salmonid densities. Many of these latter sites are found in north-west Scotland where sea-salt inputs are high and ANC is usually greater than zero μeql−1, although diatom-based studies indicated slight acidification of these waters, with a point of change in diatom flora close to ANC=20 μeql−1. These false exceedances are probably due to preferential adsorption of acidic SO4 deposition which results in an overestimate of exceedance values. All sites with a mean ANC ≤ 0 are fishless but some sites with negative minimum ANC values had normal salmonid densities. Consequently a mean ANCLIM value of zero in the critical load equations for UK freshwaters appears to be too low to protect salmonid stocks. Values between 20–50 μeql−1 represent a more realistic range if prevention of long term damage to salmonid stocks is to be achieved.