1. Modeling diffuse soil contamination from agriculture.

2. introduction SUMMARY:
Soil contamination, as defined in the Soil Thematic Strategy.
Local soil contamination and Diffuse soil contamination
Modeling Tools of Diffuse soil contamination.
SWAT Description
SWAT application, two cases
Leaching Modeling. Pesticide soil contamination.
PRZM and PEARL description
PRZM and PEARL application
Conclusion

3. Soil contamination, as defined in the Soil Thematic Strategy.
introduction
Soil contamination, as defined in the Soil Thematic Strategy.
The introduction of contaminants in the soil may result in damage to or loss of some or several functions of soils and possible cross contamination of water. The occurrence of contaminants in soils above certain levels entails multiple negative consequences for the food chain and thus for human health, and for all types of ecosystems and other natural resources.

4. Local and Diffuse Soil contamination, Sources.
introduction
Local Soil contamination, Sources.
Local (or point source) contamination is generally associated with mining, industrial facilities, waste landfills and other facilities both in operation and after closure.
These activities can pose risks to both soil and water.
Diffuse Soil contamination, Sources.
Diffuse pollution is generally associated with atmospheric deposition, certain farming practices and inadequate waste and wastewater recycling and treatment.

5. Diffuse Soil contamination, Sources.
introduction
Diffuse Soil contamination, Sources.
Atmospheric deposition is due to emissions from industry, traffic and agriculture. Deposition of airborne pollutants releases into soils acidifying contaminants (e.g. SO2, NOx), heavy metals (e.g. cadmium, lead arsenic, mercury), and several organic compounds (e.g. dioxins, PCBs, PAHs).
Production systems where a balance between farm inputs and outputs is not achieved in relation to soil and land availability, leads to nutrient imbalances in soil, which frequently result in the contamination of ground- and surface water.
Pesticides are toxic compounds deliberately released into the environment to fight plant pests and diseases. They can accumulate in the soil, leach to the groundwater and evaporate into the air from which further deposition onto soil can take place.They also may affect soil biodiversity and enter the food chain.
With regard to waste, sewage sludge, the final product of the treatment of wastewater, is also raising concern. A whole range of pollutants, such as heavy metals and poorly biodegradable trace organic compounds, potentially contaminates it what can result in an increase of the soil concentrations of these compounds.

6. Diffuse Soil contamination, Sources.
introduction
Diffuse Soil contamination, Sources.
Production systems where a balance between farm inputs and outputs is not achieved in relation to soil and land availability, leads to nutrient imbalances in soil, which frequently result in the contamination of ground- and surface water.
Modeling the fate of contaminants requires an understanding of the soil-water-air continuum.
The modeling tool should be able to simulated physical, chemical and biological processes occurring in these different compartments.

7. Atmospheric emissions
The modelling approach ...
Simulation of soil processes: organic matter turnover, crop growth, nitrogen uptake, water infiltration, evaporation from crop and soil surface, nitrification, denitrification, interception of precipitation and emissions to the atmosphere.
AIR
Atmospheric deposition
Atmospheric emissions
N fixation
Fertilizer applications
Plants
consumption
Plants consumption
Point discharges
SOIL
Surface and subsurface runoff
N Leaching
NITRIFICATION/ DENITRIFICATIONSTORAGE
RIVER
GROUNDWATER

8. … a nested approach
Vertical flow in the unsaturated zone links the soil processes to the 2-D overland flow and to the 3-D groundwater flow.
A fully distributed physically based model representing variations in catchment characteristics and driving variables by a network of uniform grids or sub-basins.
Estimation of loads at representative sites, aggregation at landscape scale, and upscaling to regions .
Calculation of the impacts of the agricultural sector under selected land use scenarios.

9. An Observational Network of European Watersheds
Scenario analyses (socio-economic, climate, environmental) to improve resource management and provide information that will aid for the sustainable management of the watershed.
Impact assessment of waste management strategies, tourism, urban areas, mining activities, land use changes.

10. Modeling of Diffuse soil contamination.
Modeling tools
Modeling of Diffuse soil contamination.
Modeling Tools: able to considering processes occurring in the soil-water-air compartments in the studied area, mainly used for Nitrogen and Phosphorus modeling.
SWAT (Soil Water Assessment Tool, Blackland Research Centre, Texas US-Arnold et al., 1992)

11. swat main characteristics SWAT description basin-scale continuous time
daily time step
physically based
computationally efficient
long-term simulations
water, sediments, nutrients, pesticides

12. SWAT description
Hydrology
model

13. SWAT
Physical model
hydrology
precipitation
surface
runoff
evapo
transpiration
lateral
flow
infiltration

14. ET is evaluated from soils and plants as well
SWAT
hydrology
Physical model
Surface runoff
use of SCS curve number method to estimate surface runoff
Evapotranspiration
Three methods included in SWAT
ET is evaluated from soils and plants as well
Penman-Monteith
Hargreaves
Priestley-Taylor
Snow melt
melting if the second soil layer temperature exceeds 0 C and proportional to the snow pack temperature

15. SWAT Physical model Soil module SWAT considers: Soil Structure
Water that enters the soil may move along one of several different
pathways. The water may be removed from the soil by plant uptake or
evaporation. It can percolate past the bottom of the soil profile and ultimately
become aquifer recharge. A final option is that water may move laterally in the
profile and contribute to streamflow. Of these different pathways, plant uptake of
water removes the majority of water that enters the soil profile.
SWAT considers:
Soil Structure
Percolation
Lateral Flow

16. Swat considers three phases in the soil:solid, liquid and gas.
hydrology
physical model
Soil Structure
Swat considers three phases in the soil:solid, liquid and gas.
The solid phase consists of minerals and/or organic matter that forms the matrix or skeleton.Between the solid particles, soil pores are formed that hold the liquid and gas phases. The soil solution may saturate the soil completely or partially. Swat calculates the balance in every layer and once (..and if ) this layer reach the saturation moves the water to the next one.

17. percolation SWAT physical model hydrology Percolation
Percolation is calculated for each soil layer in the profile. Water is allowed to percolate if the water content exceeds the field capacity water content for that layer. When the soil layer is frozen, no water flow out of the layer is calculated. The volume of water available for percolation in the soil layer is calculated:
SW ly excess= FC ly – sSW ly if FC ly > SW ly
SW ly excess = 0 , = excess ly if FC ly < or = SW ly
where SWly,excess is the drainable volume of water in the soil layer on a given day (mm H2O), SWly is the water content of the soil layer on a given day (mm H2O) and FCly is the water content of the soil layer at field capacity (mm H2O).
Percolation

18. Lateral Flow SWAT physical model hydrology lateral flow
Lateral flow will be significant in areas with soils having high hydraulic
conductivities in surface layers and an impermeable or semipermeable layer at a shallow depth. In such a system, rainfall will percolate vertically until it encounters the impermeable layer. The water then ponds above the impermeable layer forming a saturated zone of water, i.e. a perched water table. This saturated zone is the source of water for lateral subsurface flow.
lateral
flow

19. SWAT Physical model weather driving variables precipitation
daily measurements
temperature
solar radiation
wind speed
Monthly measurements
relative humidity
In case of missed values, a weather
generator is included in the code

20. MUSLE: Modified Universal Soil Loss Equation
Physical model
swat
sediments
sediment yield
MUSLE: Modified Universal Soil Loss Equation
(USDA, Williams et al. 1977)

21. swat crop growth Physical model solar radiation energy interception
biomass
leaf area
production
index
crop
heat
parameter
units
crop
yield
harvest
index

22. swat nutrients Physical model NITROGEN model in SWAT Residue
harvest
Residue
Plant uptake
Stable organic N
Decay
Mineralization
Mineralization
NO3
Active organic N
Denitrification
Inorganic fertilizer
Organic fertilizer

23. swat nutrients Physical model PHOSPHORUS model in SWAT Residue
Organic fertilizer
Mineralization
Residue
Lumped Active/Stable organic P
harvest
Mineralization
Plant uptake
Sediment-bound labile P
Dissolved labile P
Sediment-bound fixed P
Inorganic fertilizer

24. Models application
TWO EXAMPLES DEVELOPED USING
SWAT COUPLED WITH GIS (ArcInfo and ArcView, ESRI)
OUSE Catchment (UK)
BURANA PO di VOLANO Catchment (IT)
MAIN ISSUES OF THE MODEL APPLICATIONS
Allowing the quantification of the total load of pollutant affecting a watershed. This model should be used to understand how the soil quality and water quantity/quality are affected by agricultural activities.

25. Examples: OUSE Catchment (UK)
Soil Map

26. Examples: OUSE Catchment (UK)
Landuse Map
OUSE Land Use: (%)
FRSE
PAST
RANGE
WWHT
URBAN

27. OUSE WATERSHED MONTHLY TIME STEP SIMULATION(30 years simulation): FLOW OUT [m3/s] and LINEAR CORRELATION

28. OUSE WATERSHED MONTHLY TIME STEP SIMULATION(30 years simulation): TOTAL NITROGEN [Kg]

29. LANDUSE SCENARIO: COMPARISON BETWEEN N EXCESS AND N PLANT UPTAKE WITH
TWO DIFFERENT APPLICATION RATE OF ORGANIC NITROGEN IN THE OUSE WATERSHED

30. AVERAGE ANNUAL CHANGE:
LANDUSE SCENARIO: COMPARISON BETWEEN NO3 TO RIVER AND NO3 LEACHING WITH
TWO DIFFERENT APPLICATION RATE OF ORGANIC NITROGEN IN THE OUSE WATERSHED
210 Kg/ha
ORGANIC NITROGEN
AVERAGE ANNUAL CHANGE:
-6.34 %
170 Kg/ha
ORGANIC NITROGEN

31. Examples: Burana Po di Volano (IT)

32. Examples: Burana Po di Volano(IT)

33. Burana-Po di Volano watershed
Present scenario
Scenario I
Scenario II
GCM Scenario
CGCM1 e HadCM2
year 2050
Influence of Climate Change on Nitrogen Percolation from Soils to Groundwater
Burana-Po di Volano watershed
NO3 leaching
(Kg/ha)

34. Modeling of Diffuse soil contamination.
Modeling tools
Modeling of Diffuse soil contamination.
Leaching Models: applied to determine the quantity of Pesticide leaching thought the soil profile reaching the shallow aquifer.
PRZM2: Pesticide Root Zone Model, Environmental Protection Agency, US - Carsel et al
PEARL: Pesticide Emission Assessment at Regional and Local Scales by Alterra Green World Research.

35. Models application
TWO EXAMPLES DEVELOPED USING
PRZM and PEARL coupled with ARCVIEW GIS
TREVIGLIO Catchment (IT)
EUROPEAN SCALE
MAIN ISSUES OF THE MODEL APPLICATIONS
Models are run at field and regional scale to be tested (PRZM, PELMO) then the necessary information are collected at European level and run with a model like PEARL (able to work with big database) to estimate the persistence of selected substances at European scale.

36. Examples: TREVIGLIO catchment (IT)
Modeling of Diffuse soil contamination.
Regional scale
PRZM2 is a one-dimensional, dynamic, compartmental model that can be used to simulate chemical movement in unsaturated soil systems within and immediately below the plant root zone. It has two major components:
hydrology
chemical transport.
The model was specifically designed to provide loading to selected media, including air, water, groundwater. PRZM2 runs on daily time step. PRZM2 is extensively used from the U.S. Environmental Protection Agency to simulate the transport of field-applied pesticides in the crop root zone.

37. Examples: TREVIGLIO catchment(IT)
Atrazine
(app. Rate 1.5 Kg/ha)
Alachlor
(app. Rate 2.0 Kg/ha)

38. Use a process based model supported by the FOCUS working group that includes all major processes involved with pesticide transformation and fate. For instance, we are currently using the PEARL model which is used to evaluate the leaching of pesticides to the groundwater in support to the European and Dutch pesticide registration procedures.
Bentazone soil concentration 22 and 278 days after application of 0.8 kg/ha of bentazone on field under winter wheat (NL)

39. Deliverable: map of pesticides persistence in the top layer, in the root zone, and leaching below the root zone
Collect the necessary information at European level and run the PEARL model to estimate the persistence of selected substances

40. CONCLUSION:
These kind of modeling tool could be useful to analyze and simulate the water contamination in a medium-big scale watershed.
They are able to determine soil limitations (topography, rooting depth, chemical fertility, organic carbon) of European soils (using harmonised European soil information system).
It is also possible to derive crop suitability zones and compare the capability maps with land use maps.
Useful to make some general conclusion about the effect of the global climate change could be done.
LIMITATIONS:
The calibration of the model is time-consuming and it would need more efficient tools
The quality of the model simulation depends on the quality of the data available.