Risk Management/Agricultural Water Pollution Management
Appearance
Surface runoff: The hydrological dilemma
[edit | edit source]Surface runoff increases disproportionally to rainfall.
Artificial surface waters
[edit | edit source]Characteristics:
- artificial
- drainage channels
- channelized
- cleared
Differences to natural surface waters:
- lower plant density
- higher flow velocity / lower retention time
- higher flood potential (in downstream regions)
- reduced self purification
Surface waters do not fulfil their full range of ecosystem services to humans and society!
Constructed Wetland (CW)
[edit | edit source]Characteristics
[edit | edit source]- artificial wetland containing vegetation
- created for treating anthropogenic
- discharge (municipal or industrial wastewater)
- storm-water runoff (urban or agriculture)
- decrease of flow velocity / longer residence time
- higher sedimentation rate
- higher metabolisation rates: photodegradation and microbial processes
- integration of nutrients in biomass
- adsorption of chemicals to organic surfaces (e.g., plants or sediment)
Important factors
[edit | edit source]- size
- flow length
- hydraulic loading rate
- hydraulic retention time
Retention
[edit | edit source]The retention of a chemical or suspended solids can be calculated:
with
Study: a real constructed wetland
[edit | edit source]Study Concept
[edit | edit source]- Application of Azinphos-methyl (AZP) to orchards
- Measurement of AZP at inlet and outlet before and after application events
- Calculation of AZP retention
Results
[edit | edit source]- 90% AZP retention in the CW
- Sorption of AZP to aquatic macrophytes
- Retention of > 90% of measured insecticide substances observed
- Sorption of AZP to aquatic macrophytes
Conclusion
[edit | edit source]Constructed wetlands are a good option for agricultural water management
- A case study showed that pesticide retentions ≥ 90% are possible within a CW
- Mortality of aquatic invertebrates was 90% lower at concentrations measured at the CW outlet compared to concentrations measured at the inlet
- Plants play an important role in the retention of pesticides as shown in a meta analysis of literature data