Nutrients/Description: Difference between revisions
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|Description=<h2> A. Wastewater nutrient model</h2> | |Description=<h2> A. Wastewater nutrient model</h2> | ||
Urban wastewater contains N and P emitted by households and industries that are connected to a sewage system, and households with sanitation but lacking a sewage connection. N discharges to surface water ( in kg per person per year) is calculated as follows ([[Van Drecht et al., 2009]]): | Urban wastewater contains N and P emitted by households and industries that are connected to a sewage system, and households with sanitation but lacking a sewage connection. N discharges to surface water ( in kg per person per year) is calculated as follows ([[Van Drecht et al., 2009]]): | ||
{{FormulaAndTableTemplate|Formula1_N}} | {{FormulaAndTableTemplate|Formula1_N}} | ||
where is human N emissions (kg per person per year), D is the fraction of the total population that is connected to public sewerage systems (no dimension), and R N is the overall removal of N through wastewater treatment (no dimension). Total P emissions to surface water are calculated in a similar way, but also include estimates of P emissions to surface water resulting from the use of P-based dishwasher and laundry detergents. Nutrient removal by wastewater treatment R is based on the relative contribution of four classes of treatment (none, primary, secondary and tertiary treatment). D (calculated from the fraction of households with improved sanitation) and R (by treatment class) are scenario variables. | where is human N emissions (kg per person per year), D is the fraction of the total population that is connected to public sewerage systems (no dimension), and R N is the overall removal of N through wastewater treatment (no dimension). Total P emissions to surface water are calculated in a similar way, but also include estimates of P emissions to surface water resulting from the use of P-based dishwasher and laundry detergents. Nutrient removal by wastewater treatment R is based on the relative contribution of four classes of treatment (none, primary, secondary and tertiary treatment). D (calculated from the fraction of households with improved sanitation) and R (by treatment class) are scenario variables. | ||
==B. Soil nutrient budget model== | ==B. Soil nutrient budget model== | ||
The soil budget approach ([[Bouwman et al., 2009]]; [[Bouwman et al., 2011]]) includes the N and P input and output for IMAGE grid cells. Soil N budgets are calculated for two production systems (see figure on the right, B.), i.e. mixed and pastoral livestock production systems ([[Livestock]]). N input includes application of synthetic N fertiliser (Nfert) and animal manure (Nman), biological N fixation (Nfix), atmospheric N deposition (Ndep). Output includes N withdrawal from the field through crop harvesting, hay and grass cutting, and grass consumed by grazing animals (Nwithdr). The soil N budget (Nbudget) is calculated as follows: | The soil budget approach ([[Bouwman et al., 2009]]; [[Bouwman et al., 2011]]) includes the N and P input and output for IMAGE grid cells. Soil N budgets are calculated for two production systems (see figure on the right, B.), i.e. mixed and pastoral livestock production systems ([[Livestock]]). N input includes application of synthetic N fertiliser (Nfert) and animal manure (Nman), biological N fixation (Nfix), atmospheric N deposition (Ndep). Output includes N withdrawal from the field through crop harvesting, hay and grass cutting, and grass consumed by grazing animals (Nwithdr). The soil N budget (Nbudget) is calculated as follows: | ||
{{FormulaAndTableTemplate| | {{FormulaAndTableTemplate|Formula2_N}} | ||
For P the same approach is used, P input being animal manure and fertiliser. The soil nutrient budget ignores nutrient accumulation in soil organic matter in case of a positive budget (surplus), and soil organic matter decomposition and mineralisation. With no accumulation, a surplus represents a potential loss to the environment (for N this includes NH3 volatilisation ([[Emissions]]), denitrification, surface runoff and leaching; for P this is surface runoff). | For P the same approach is used, P input being animal manure and fertiliser. The soil nutrient budget ignores nutrient accumulation in soil organic matter in case of a positive budget (surplus), and soil organic matter decomposition and mineralisation. With no accumulation, a surplus represents a potential loss to the environment (for N this includes NH3 volatilisation ([[Emissions]]), denitrification, surface runoff and leaching; for P this is surface runoff). | ||
For a spatial allocation of the nutrient input to IMAGE grid cells, the crop groups in IMAGE (temperate cereals, rice, maize, tropical cereals, pulses, roots and tubers, oil crops, other crops, energy crops) and grass are aggregated to form five broad groups, including grass, wetland rice, leguminous crops, other upland crops and energy crops, within mixed and pastoral production systems. | For a spatial allocation of the nutrient input to IMAGE grid cells, the crop groups in IMAGE (temperate cereals, rice, maize, tropical cereals, pulses, roots and tubers, oil crops, other crops, energy crops) and grass are aggregated to form five broad groups, including grass, wetland rice, leguminous crops, other upland crops and energy crops, within mixed and pastoral production systems. | ||
Revision as of 12:22, 16 December 2013
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