IMPACT OF ATMOSPHERIC N DEPOSITION ON INORGANIC-N AND ORGANIC-N OUTPUTS IN WATER DRAINING FROM PEAT

Replicate intact peat turf microcosms from nine sites along a nitrogen (N) pollution gradient in Great Britain, from Strathvaich in North-We st Scotland to Hatfield Moor in the English Midlands, have been subjec ted to simulated precipitation for 18 months in an unheated glasshouse in Aberdeen. The rainfall applied to each turf had a composition base d upon that of rainfall at the UK Department of the Environment(DOE) m onitoring sites adjacent to the locations from which the turfs were co llected. After an initial 6-month equilibration, drainage water was ca lculated by difference. Annual N fluxes in the three forms were then c alculated. At low to moderate NO3- inputs, NO3- was largely retained i n the plant soil system, but at higher NO3- inputs, NO3- leaching occu rred. Except at the two most polluted sites, NH4+ leaching exceeded NH 4+ input. To a first approximation, leached organic N increased linear ly with N input, although at higher N inputs, organic N accumulation a pparently became relatively more important. Only at very high N deposi tion rates do the peats appear to be acidifying as a consequence of N deposition.