Risk Management/Agricultural Water Pollution Management

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Surface runoff: The hydrological dilemma[edit]

Surface runoff increases disproportionally to rainfall.

Artificial surface waters[edit]

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]

Characteristics[edit]

  • 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]

  • size
  • flow length
  • hydraulic loading rate
  • hydraulic retention time

Retention[edit]

The retention of a chemical or suspended solids can be calculated:

with

Study: a real constructed wetland[edit]

Study Concept[edit]

  • 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]

  • 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]

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