Nitrogen processes in aquatic ecosystems

摘要: Nature of the problem * Freshwater ecosystems play a key role in European nitrogen (N) cycle, both as reactive agent that transfers, stores and processes N loadings from atmosphere terrestrial ecosystems, natural environment severely impacted by increase these loadings. Approaches This chapter is review major factors controlling transport transformations for running waters, standing groundwaters riparian wetlands. Key findings/state knowledge The factor freshwater residence time water, which varies widely space time, sensitive to changes climate, land use management. effects increased freshwaters include acidifi cation semi-natural environments, eutrophication more disturbed with associated loss biodiversity cases. An important part transferred surface waters form organic N, dissolved (DON) particulate (PON). Th dominant catchments throughout Europe remains signifi cant component total load even nitrate enriched rivers. In eutrophicated can be limiting or co-limiting biological production, control phosphorus (P) loading oft en needed areas, if ecological quality restored. Major uncertainties/challenges importance storage denitrifi aquifers uncertainty global controls response management changes. some aquifers, concentrations will continue decades efficient mitigation measures are implemented now. Nitrate retention wetlands has been highlighted. However, their must treated caution, since effectiveness difficult predict, side eff ects DON emissions adjacent open N2O atmosphere, biodiversity. fact, character specifi c spatial origins not fully understood, similarly quantitative indirect result leaching losses agricultural soils still poorly known at regional scale. These uncertainties remain due lack adequate monitoring (all forms relevant frequency), especially - but only southern eastern EU countries. Recommendations great variability transfer pathways, buffering capacity sensitivity calls site specific rather than standard ones applied national temporal variations forms, transformation within freshwaters, require further investigation infl uencing ecosystem health better underpinning implementation Water Framework Directive freshwaters.