Nutrients: Difference between revisions
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|Description=Human activities have accelerated the Earth’s biogeochemical nitrogen (N) and phosphorus (P) cycles by increasing the use of fertilizers in agriculture (Bouwman et al., 2011). The changes in global nutrient cycles have both positive and negative effects. Increased use of N and P fertilizers has allowed for the production of food required to support a rapidly growing human population, and increasing per-capita consumption of particularly meat and milk(Galloway et al., 2004). This has also contributed to ongoing gains in yields, thereby making agriculture economically viable on an area that expanded much less than the harvested output. A side-effect is that significant fractions of the mobilized N are lost through emissions of ammonia (NH3), nitrous oxide (N2O) and nitric oxide (NO) into the ambient air. Ammonia contributes to eutrophication and acidification when deposited on land. Nitric oxide plays a role in tropospheric ozone chemistry, and nitrous oxide is a potent greenhouse gas. Also, large fractions of the mobilized N and P in watersheds enter groundwater through leaching, and are released to surface water through groundwater transport and surface runoff. Subsequently, nutrients in streams and rivers are transported towards coastal marine systems, reduced by retention but augmented by releases from point sources such as sewage systems and industrial facilities. | |||
This has resulted in numerous negative impacts on human health and the environment, such as groundwater pollution, loss of habitat and biodiversity, an increase in frequency and severity of harmful algal blooms, eutrophication, hypoxia and fish kills (Diaz and Rosenberg, 2008; Zhang et al., 2010). Such harmful effects of eutrophication have been spreading rapidly around the world, with large-scale implications for biodiversity, water quality, fisheries and recreation in both industrialized and developing regions (United_Nations_Environment_Programme_(UNEP), 2002). In freshwater and coastal marine ecosystems it is not only the inputs of nutrients but also the disturbance of the stoichiometric balance of N, P and silica (Si) (Rabalais, 2002) that affect both the total plant production and the species dominating in ecosystems. | |||
To assess eutrophication as a consequence of changing population, economy and technological development, IMAGE 3.0 includes a nutrient model with three submodels: | |||
A. Wastewater model (Figure 6.4.1a), which generates nutrient flows in wastewater discharge; | |||
B. Soil nutrient budget model (Figure 6.4.1b), describing all inputs and outputs of N and P in the soil compartment; | |||
C. Nutrient environmental fate model (Figure 6.4.1c), which describes the fate of soil nutrient surpluses and wastewater nutrients in the aquatic environment. | |||
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Revision as of 12:32, 2 August 2013
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Key policy issues
- How will the increasing use of fertilisers affect terrestrial and marine ecosystems, with possible consequences for human health?
- To what extent can the negative impacts be reduced by more efficient nutrient management and wastewater treatment, while retaining the positive effects on food production and land productivity?
Introduction
"model component" is not in the list (driver component, pressure component, interaction component, state component, impact component, response component) of allowed values for the "FrameworkElementType" property.