Attenuation of groundwater contamination caused by cattle slurry: a plot-scale experimental study

Area of Science:

• Environmental Science
• Soil Science
• Agricultural Science

Background:

• Cattle slurry application is a common agricultural practice.
• Understanding contaminant transport from slurry to groundwater is crucial for environmental protection.

Purpose of the Study:

• To investigate the infiltration and attenuation of contaminants from cattle slurry in a pasture ecosystem.
• To identify the primary mechanisms responsible for contaminant reduction in soil and groundwater.

Main Methods:

• Field experiment on a Lolium perenne L. pasture plot treated with cattle slurry.
• Installation of lysimeters and piezometers for groundwater sampling at various depths.
• Chemical and microbiological analysis of water samples for parameters including nutrients, ions, chemical oxygen demand (COD), and indicator bacteria.

Main Results:

• Contaminant concentrations in shallow soil water (5 cm depth) reached 22-83% of raw slurry levels within 2 hours.
• After 150 mm rainfall, groundwater contaminant levels were below 95% of initial slurry concentrations.
• Most contaminants, except chloride, nitrate, potassium, and COD, returned to pre-application levels within 15 days.
• Mechanical retention attenuated microorganisms and COD; cation sorption attenuated cations; rainwater dilution had a lesser effect.

Conclusions:

• Soil effectively attenuates contaminants from cattle slurry, primarily through mechanical retention and sorption processes.
• While rapid infiltration occurs, groundwater quality is largely restored within a short period post-application.
• Management practices should consider these attenuation mechanisms to minimize environmental impact.