Mineralization of 14C-ring labelled 2,4-D in Egyptian soils under aerobic and anaerobic conditions.
OBJECTIVE
To study the mineralization of 2,4-D in clay and clay loam Egyptian soils under subtropical conditions over a period of 90 d.


METHODS
Using 14C-ring labelled pesticide, laboratory studies under aerobic and anaerobic conditions were conducted. 14C-activity in solutions was directly determined by liquid scintillation counting. Unextractable soil residues were determined by combustion. The nature of methanolic 14C-residues was determined by thin layer and high performance liquid chromatographic analysis.


RESULTS
Under aerobic conditions 10%-14% of applied dose was mineralized during 90 d irrespective of soil type. The soil extractable pesticide residues decreased with time and the bound residues gradually increased. The highest binding capacity of about 26%-29% was observed in clay soil under aerobic conditions after 90 d. A good balance sheet was obtained and the percentage recovery was generally between 91% and 100%.


CONCLUSIONS
The mineralization of 2,4-D in clay soil was higher than that in clay loam soil under anaerobic conditions. Under aerobic conditions, the soil type had no influence on mineralization capacity of 2,4-D during 90 d. The soil binding increased with time whereby the extractable 14C-residues simultaneously decreased. Chromatographic analysis of the methanol extractable 14C-residues of soils revealed the presence of 2,4-D as a main product together with 2,4-dichlorophenol.
Zayed
S M A D
SM
National Research Center, Dokki, Cairo, Egypt.
Farghaly
M
M
Taha
H
H
D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry*; D000538:Aluminum Silicates; D002250:Carbon Radioisotopes / Q000032:analysis; D000077215:Clay; D004534:Egypt; D006540:Herbicides / Q000737:chemistry*; D010100:Oxygen; D012989:Soil Pollutants / Q000032:analysis*
D000538:Aluminum Silicates; D002250:Carbon Radioisotopes; D006540:Herbicides; D012989:Soil Pollutants; D015084:2,4-Dichlorophenoxyacetic Acid; D010100:Oxygen; D000077215:Clay