It has been recognised for many years that the first fraction of meltwater from a melting snowpack contains a much higher concentration of ions than that of the bulk (or average) snow of which the pack is comprised (Foster 1978, Johannessen andHenriksen 1978). This process leads to the so called "acid flush" in the spring and can have severe ecological effects on lakes and streams (Hagen and Langeland 1973, Leivestad and Muniz 1976, National Research Council of Canada 1981. We have studied elution of ions through a snowpack on Folgefonna near Bergen, Norway, and in the laboratory. In the field we collected meltwater samples at hourly intervals for a period of 4 d at the start of the melt season, and analyzed them for pH, NO;, SO~-, CI-, Na+, Mg2+, Ca2+ and K+. 2 m cores were also collected at the beginning and end of the experiment in order to study bulk changes in snow composition. The meltwaters showed a diurnal cycle with high ionic concentrations around noon, with NO; and SO;-levels rising by factors of up to four and six-fold compared to the average concentrations on the first day. Cl-levels peaked much later, after the NO; and SO!-levels had decreased, and only reached 2.3 times their lowest concentrations. pH values were strongly correlated with NO; and S02-levels suggesting that a significant proportion of these ani~ns wer~ in the form of strong acids.The laboratory experiments involved slow melting of snow samples collected in the Cairngorm mountai ns, Scotland, and also showed that NO; and SO!-(and also Mg 2 + and K+) ions were removed from the snow preferentially whilst Na+ and Cl-tended to remain longer. The position of H+ within the ion elution sequence is unclear due to uncertainties in the absolute determination of pH in the field measurements, but the laboratory experiments confirm the differential rates of elution shown in the Norwegian snowpack and reaffirms its importance in the acidification of streams during spring. I. INTRODUCTIONPrevious work on Folgefonna (Davies and others 1982) has shown that not only are the majority of ions removed from the overlying snow and firn early in the melt sequence (fractionation), but that some ionic species are removed preferentially (preferential elution) . This suggests that this latter process could result in the early removal of hydrogen ions (relative to other cations), together with SO;-and NO; ions, as strong acids. However the results from the previous study are difficult to interpret as they come from a 60 m core which, in the upper 20 m at least, represents a combination of ice from which the majority of ions would have been removed during a previous melt season and the meltwater percolating downwards from the snow melting near the surface. The experiments described here were designed to look at the processes of preferential elution and fractionation under more controlled conditions, both in the field and in the laboratory.
SummaryPatterns of granular fertiliser deposition differed markedly between a pneumatic boom applicator and a spinning disk machine, both of which were tractor‐mounted. The pneumatic applicator gave relatively even distribution across the boom width. A spinning disk gave more variable deposition and significant amounts were spread further than the expected 12 m overlapping pattern. When operating with a deflector plate on the spinning disk, significant amounts of fertiliser were also spread further than the expected 6 m. However, when operating next to a hedge, there was evidence of fertiliser concentration at the base of the hedge and prevention of granules passing through to adjacent habitat. A peak concentration of up to 150 kg ha‐1 of fertiliser was deposited at the hedge/field edge interface.In a tray experiment on seedling competition and establishment, there was no evidence of nitrogen fertiliser effects, at rates found in the field, on early plant establishment or species diversity. However, in a competition experiment with established plants of four grass species grown in pots, the nitrophilous species Bromus sterilis was able to increase growth at increasing nitrogen level, at the expense of slow‐growing Brachypodium sylvaticum and Anthoxanthum odoratum. Whilst hedges may buffer fertiliser contamination of habitats adjacent to agricultural fields, deposition of concentrated nitrogen fertiliser beside the hedge is likely to encourage the growth of nitrophilous plant species. In the short term, this may not affect botanical composition or diversity, but to reduce the likely long‐term adverse effects of fertiliser misplacement, we recommend that farmers are encouraged to use pneumatic fertiliser applicators and to introduce vegetation buffer strips at field edges.
Under controlled laboratory conditions, artificial rain leaches solute from snow columns, and gives rise to leachate with a composition similar to snowmelt, in addition to the solute initially present in the artificial rain. The initial concentration of ions in the leachate, normalized to the concentration of ions found in the original snow and corrected for the solute present in the artificial rain, is similar to those reported in other laboratory and field studies of snowmelt composition, but there is some evidence that the concentration of leached ions declines more rapidly than during snowmelt. Similarly, as in snowmelt studies, not all ions are leached with the same efficiency. Bearing in mind the confounding influences of snow crystal morphology and snow column hydrology, it seems likely that rain will leach solute from snowpack during rain-on-snow events, in a manner similar to leaching by snowmelt, and that the precise composition of the leachate will depend on the hydrological routing of rain-meltwater mixtures through the snowpack.
It has been recognised for many years that the first fraction of meltwater from a melting snowpack contains a much higher concentration of ions than that of the bulk (or average) snow of which the pack is comprised (Foster 1978, Johannessen andHenriksen 1978). This process leads to the so called "acid flush" in the spring and can have severe ecological effects on lakes and streams (Hagen and Langeland 1973, Leivestad and Muniz 1976, National Research Council of Canada 1981. We have studied elution of ions through a snowpack on Folgefonna near Bergen, Norway, and in the laboratory. In the field we collected meltwater samples at hourly intervals for a period of 4 d at the start of the melt season, and analyzed them for pH, NO;, SO~-, CI-, Na+, Mg2+, Ca2+ and K+. 2 m cores were also collected at the beginning and end of the experiment in order to study bulk changes in snow composition. The meltwaters showed a diurnal cycle with high ionic concentrations around noon, with NO; and SO;-levels rising by factors of up to four and six-fold compared to the average concentrations on the first day. Cl-levels peaked much later, after the NO; and SO!-levels had decreased, and only reached 2.3 times their lowest concentrations. pH values were strongly correlated with NO; and S02-levels suggesting that a significant proportion of these ani~ns wer~ in the form of strong acids.The laboratory experiments involved slow melting of snow samples collected in the Cairngorm mountai ns, Scotland, and also showed that NO; and SO!-(and also Mg 2 + and K+) ions were removed from the snow preferentially whilst Na+ and Cl-tended to remain longer. The position of H+ within the ion elution sequence is unclear due to uncertainties in the absolute determination of pH in the field measurements, but the laboratory experiments confirm the differential rates of elution shown in the Norwegian snowpack and reaffirms its importance in the acidification of streams during spring. I. INTRODUCTIONPrevious work on Folgefonna (Davies and others 1982) has shown that not only are the majority of ions removed from the overlying snow and firn early in the melt sequence (fractionation), but that some ionic species are removed preferentially (preferential elution) . This suggests that this latter process could result in the early removal of hydrogen ions (relative to other cations), together with SO;-and NO; ions, as strong acids. However the results from the previous study are difficult to interpret as they come from a 60 m core which, in the upper 20 m at least, represents a combination of ice from which the majority of ions would have been removed during a previous melt season and the meltwater percolating downwards from the snow melting near the surface. The experiments described here were designed to look at the processes of preferential elution and fractionation under more controlled conditions, both in the field and in the laboratory.
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