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Particle‐facilitated Pesticide Leaching from Differently Structured Soil Monoliths
Author(s) -
Gjettermann B.,
Petersen C. T.,
Koch C. B.,
Spliid N. H.,
Grøn C.,
Baun D. L.,
Styczen M.
Publication year - 2009
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2008.0417
Subject(s) - leaching (pedology) , loam , macropore , lessivage , chemistry , leachate , environmental chemistry , pesticide , glyphosate , soil science , environmental science , soil water , agronomy , mesoporous material , biochemistry , biology , catalysis
The leaching of soil particles and surface applied 14 C‐labeled glyphosate and pendimethalin from intact soil columns (height: 50 cm; diameter: 30 cm) were investigated, and the relative significance of particle‐facilitated pesticide transport was quantified. Investigations were performed with a recently plowed (four columns) and an untilled (five columns) sandy loam soil. Leaching was driven by three irrigation events (15 mm h −1 ; 2 h each). Samples of the leachate were filtered immediately (within 1.5 minutes) using 20 nm filters, and the 14 C‐pesticide content was determined for filtered and unfiltered samples. Pesticide leaching was driven by preferential water flow in macropores. For the plowed structure, 68 ± 10% of the leached glyphosate (average of 6 events ± std.) was bound to particles whereas significantly less glyphosate was bound to particles in leachate from minimally disturbed columns (17 ± 12%). Thus, the results suggest that soil structure affected the mode of transport of glyphosate. It is likely that glyphosate sorbed strongly when applied on recently plowed soil ( K d = 503 L kg −1 for the soil), and that it could be mobilized and transported independently of soil particles more easily when applied on the minimally disturbed soil covered in part with crop residues ( K d < 1 L kg −1 for straw). Significantly less amounts of soil particles were leached from minimally disturbed (119–247 mg) than from recently plowed (441–731 mg) columns. The significance of particle‐facilitated pendimethalin leaching could not be accurately quantified due to disagreement between control measurements based on both 14 C‐activity and chemical analyses.