RESUMEN
Soil nitrogen (N) budgets are used in a global, distributed flow-path model with 0.5° × 0.5° resolution, representing denitrification and N2O emissions from soils, groundwater and riparian zones for the period 1900-2000 and scenarios for the period 2000-2050 based on the Millennium Ecosystem Assessment. Total agricultural and natural N inputs from N fertilizers, animal manure, biological N2 fixation and atmospheric N deposition increased from 155 to 345 Tg N yr(-1) (Tg = teragram; 1 Tg = 10(12) g) between 1900 and 2000. Depending on the scenario, inputs are estimated to further increase to 408-510 Tg N yr(-1) by 2050. In the period 1900-2000, the soil N budget surplus (inputs minus withdrawal by plants) increased from 118 to 202 Tg yr(-1), and this may remain stable or further increase to 275 Tg yr(-1) by 2050, depending on the scenario. N2 production from denitrification increased from 52 to 96 Tg yr(-1) between 1900 and 2000, and N2O-N emissions from 10 to 12 Tg N yr(-1). The scenarios foresee a further increase to 142 Tg N2-N and 16 Tg N2O-N yr(-1) by 2050. Our results indicate that riparian buffer zones are an important source of N2O contributing an estimated 0.9 Tg N2O-N yr(-1) in 2000. Soils are key sites for denitrification and are much more important than groundwater and riparian zones in controlling the N flow to rivers and the oceans.
Asunto(s)
Desnitrificación/fisiología , Ecosistema , Modelos Teóricos , Ciclo del Nitrógeno , Óxido Nitroso/metabolismo , Suelo/química , Fertilizantes/análisis , Agua Subterránea/química , Estiércol/análisisRESUMEN
New and future health care technology has important implications for the delivery and organization of health care. Furthermore, advances in health care technology are increasingly associated with social, ethical, and economic issues. Effective health planning needs to anticipate future health care technology and take into account such implications. This paper concerns an analysis of future health care technology undertaken in the Netherlands. The study involved: (a) the early identification of future developments in health care technology; and (b) prospective assessments of a number of high-priority technologies. The paper concludes that technology forecasting in health care should become an integral part of overall technology assessment activities in industrialized countries.
