Pollution of Water by Agriculture
• Vicki Chapman
• Vanina Guevel
• Anne Newson
• Tony
Situation• Before : organic waste as fertilizers
• environment not a priority
• Now : intensive agriculture
• improved techniques
• mineral fertilizers
• pesticides
• tests available
How serious is the problem?
What factors pollute water?
• Nutrients• Slurry• Pesticides• Chemicals• Milk effluents
• Silage effluents• Animal carcasses• Heavy metals• Erosion• Seeds
Causes of all farm pollution incidents 1987-1991
NutrientsNutrients
• Main nutrients - nitrogen, phosphorus, potassium
• Source - fertiliser, manure, rainfall, sewage, silage, etc.
• EC Limit - rivers must not exceed the 50 mg N /litre of water
• Stimulate crop growth. A limit of 250 kg total N/year/ha is recommended from livestock manures
• The loss of the nutrients through soil percolation and land runoff, into the waterways causes disruption to the balance of the aquatic habitat.
Slurry• Source – a mixture of
animal dung and urine, Est. 200 million tonnes undiluted excreta produced annually in UK, 50% slurries.
• Most slurry stored in earth bank lagoons estimated total volume is 15.5 million m3
• Virtually all livestock waste is recycled to the land causing 17% of water pollution from agriculture to come from slurry.
• There is a restriction of 10m 'no spreading' zone adjacent to all water courses, direct spillage is highly prosecuted.
• Improvements in available grants have improved slurry stores, decreasing incidence from 99 incidents in 1991 to 28 in 1996.
PesticidesPesticides
• Herbicides
• Fungicides
• Insecticides
• Molluscicides
• Rodenticides
• Growth regulators
• Sheep dips
• … about 450 different products
• Get into river by run-off into drains, leaching from soil, spray drift into watercourse, washings
• High persistence and toxicity• Kill fish, amphibians, invertebrates and plants• Accumulation in lipids
and sediments
• Trace concentrations hard to measure• Long-term effects often unknown
Milk and chemicalsMilk and chemicals
• Milking parlour washing effluents
• Waste milk spread on the fields
• Udder wash• 400x more polluting
than untreated domestic sewage
Silage effluent
• Very harmful and concentrated pollutant
• BOD level = 30,000 – 80,000mg/l. Compare to 20-60mg/l for treated sewage.
• Very corrosive. Hard to break down. Kills fish.
Erosion
• = the wearing away of the soil by wind/water
• Soil clogs waterways• Excludes light from
water• Aquatic plants die• No oxygen for fish
and other aquatic life
SummarySUMMARY
Conclusion:How to reduce pollution
• Agricultural animals should have no direct contact with running water courses.
• Silage and slurry containers should be 100% leak-proof.
• Organic wastes, fertilisers, etc. should not be applied closer than 10m from the river (buffer strip) or 50m from wells or bore holes.
• No intensive agriculture in “High risk areas” e.g. frozen ground, floodplain, etc.
• Better use of pesticides
• Plant new crops in stubble to reduce ploughing (see right)
Laws controlling pollution
• Water Act 1989 – Farmers can be fined up to £20,000 for causing pollution!
• Environmental Protection Act 1990 – an integrated pollution control system for safe disposal of wastes.
• Classification of pesticides – – Class I : forbidden (HCH, DDT, etc.)– Class II : to be reduced (PCSDs, etc.)
Hope for the future