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Abstract: This study was designed to investigate the leaching response of an upland moorland to long-term (10yr) ammonium nitrate additions of 40, 80 and 120kgNha-1yr-1 and to relate this response to other indications of potential system damage, such as acidification and cation displacement. Results showed increases in nitrate leaching only in response to high rates of N input, in excess of 96 and 136kg total N input ha-1yr-1 for the organic Oh horizon and mineral Eag horizon, respectively. Individual N additions did not alter ammonium leaching from either horizon and ammonium was completely retained by the mineral horizon. Leaching of dissolved organic nitrogen (DON) from the Oh horizon was increased by the addition of 40kgNha-1yr-1, but in spite of increases, retention of total dissolved nitrogen reached a maximum of 92% and 95% of 80kg added N ha-1yr-1 in the Oh and Eag horizons, respectively. Calcium concentrations and calcium/aluminium ratios were decreased in the Eag horizon solution with significant acidification mainly in the Oh horizon leachate. Nitrate leaching is currently regarded as an early indication of N saturation in forest systems. Litter C:N ratios were significantly lowered but values remained above a threshold predicted to increase leaching of N in forests. [Copyright &y& Elsevier]

A field-based system used to quantify the response of acid grassland to reduced atmospheric nitrogen and sulphur deposition, and to investigate the effects of elevated soil temperature on acid grassland development is described. The system is based on 12 retractable roofs, covering undisturbed experimental plots of acid grassland and three controls. Nine roofs are used to exclude natural precipitation and three roofs used to retain emitted IR radiation at night. An irrigation system has been developed to simulate natural precipitation, allowing for the application of specific treatment regimes of ambient, reduced nitrogen and reduced nitrogen/sulphur deposition beneath the nine rain exclusion plots. Plant, soil parameters, leachate chemistry and gaseous fluxes are being monitored and initial results on soil water chemistry are described. Warming appeared to enhance nitrate concentrations in soil water but this was not sustained beyond the first year of treatment. In contrast, the deposition reduction treatments decreased soil water nitrate concentrations within a few weeks of reducing deposition. This was not observed for other solutes such as sulphate or ammonium suggesting a more direct link between deposition of nitrate and leaching losses. [ABSTRACT FROM AUTHOR]

Soil- and stream-water data from the Plynlimon research area, mid-Wales, have been used to develop a conceptual model of spatial variations in nitrogen (N) leaching within moorland catchments. Extensive peats, in both hilltop and valley locations, are considered near-complete sinks for inorganic N, but leach the most dissolved organic nitrogen (DON). Peaty mineral soils on hillslopes also retain inorganic N within upper organic horizons, but a proportion percolates into mineral horizons as nitrate (NO), either through incomplete immobilisation in the organic layer, or in water bypassing the organic soil matrix via macropores. This NOreaches the stream where mineral soilwaters discharge (via matrix throughflow or pipeflow) directly to the drainage network, or via small N-enriched flush wetlands. NOin hillslope waters discharging into larger valley wetlands will be removed before reaching the stream. A concept of catchment ‘nitrate leaching zones’ is proposed, whereby most stream NOderives from localised areas of mineral soil hillslope draining directly to the stream; the extent of these zones within a catchment may thus determine its overall susceptibility to elevated surface water NOconcentrations. [ABSTRACT FROM AUTHOR]

Reports on temporal trends in bromine, iron and dissolved organic carbon in peat water. Time-series analysis; Long-term consequences for water quality.

Abstract: Dune slacks are a species-rich habitat controlled largely by water chemistry and fluctuations in groundwater. Changes in water chemistry and water table level were analysed in 8 piezometers and 15 ephemeral surface water locations at a large UK dune system over a 12-month period. Total nitrogen concentrations in groundwater varied from 0.27–8.21 mg N L−1, where dissolved organic nitrogen was dominant at the low nitrogen locations and nitrate was dominant at the high nitrogen locations. Principal components analysis of the water chemistry suggests at least four chemically distinct groundwater signatures. Water levels showed strong temporal heterogeneity. Comparisons of water levels with antecedent rainfall identified a component of year-round groundwater feed and differing seasonal responses overlain by a complex series of lags. In summer, there were lags of four, six and seven months with an additional rapid peaky response to daily rainfall with a one-day lag. In winter, water levels were strongly influenced by exogenous groundwater supply, but again exhibited multiple lags. This study shows that local variations in water chemistry and in hydrological regime can be more complicated than previously thought, with clear implications for optimum management of these high priority habitats for conservation. [Copyright &y& Elsevier]