3 Erosion and Sediment Transport - 3.1 Biogeochemical cycles

Question 1

Learning Objectives

Answer 1

 You understand erosion and sediment transport as natural processes, where matter is relocated within river catchments.

 You know anthropogenic influences on these processes, and measures to control the environmental impact.

 You learn and practise conceptual models of these processes

Question 2

Biogeochemical Cycles at glance

Answer 2

 Definition: fluxes of chemical elements through atmosphere, hydrosphere, lithosphere and biosphere.

 Fluxes can include short-time and long-time reservoirs.

 Biogeochemical cycles are an important prerequisite for life on earth.

 Cycles of matter are closed, because the total matter of the earth is almost constant.
Cycles of energy are open.

 Driving forces are solar radiation, geothermal energy and gravity.

Question 3

Spheres and Fluxes

Answer 3

See pict on slide 4

Question 4

Important Cycles of Matter

Answer 4

 Elements
– calcium, carbon, hydrogen, mercury, nitrogen, oxygen, phosphorus, selenium, sulfur

 Molecules
– silica (SiO2), water (H2O)

 Rocks
– macroscopic cycle including sediments

 Synthetic anthropogenic pollutants
– PCB

Question 5

Biogeochemical Cycles: Scientific Interest

Answer 5

 Transport paths of matter
– Erosion and weathering
– Wind, water, ocean currents
– Metabolism

 Mobility of matter
– Solubility
– Fugacity
– Sorption capacity
– State of matter
– Residence times in reservoirs
– Balance of matter

 Disturbance of cycles by human activity

Question 6

Catchments: Point and Non-point Pollution

Answer 6

 Point sources at catchment scale
– Urban drainage and wastewater treatment
– Industrial emissions
– Contaminated land

 Non-point (diffuse) sources
– Erosion
– Rain wash
– Drainage (a relevant source, which can be located, counts as point source)
– Atmospheric deposition

Note: Emissions from urban areas are usually seen as point sources, whereas emissions from agricultural areas are usually seen as diffuse sources.

Question 7

Rock/Sediment Cycle

Answer 7

See pict on slide 8

Question 8

Erosion and Sediment Transport

Answer 8

• Erosion, transport and sedimentation determine the creation and formation of river beds.
• These are dynamic processes, which relocate natural and anthropogenic matter in catchments.
• Erosion is considered as non-point source of emission, because it cannot be attributed to a single source.
• The processes can be caused, initialized and accelerated by anthropogenic activities.
• Measurement and modelling are challenging and associated with high uncertainty.