A new tool for laboratory studies on volatilization: extension of applicability of the photovolatility chamber.
Volatilization from soil and plant surfaces after application is an important source of pesticide residues to the atmosphere. The laboratory photovolatility chamber allows the simultaneous measurement of volatilization and photodegradation of 14C-labeled pesticides under controlled climatic conditions. Both continuous air sampling, which quantifies volatile organic compounds and 14CO2 separately, and the detection of surface-located residues allow for a mass balance of radioactivity. The setup of the photovolatility chamber was optimized, and additional sensors were installed to characterize the influence of soil moisture, soil temperature, and evaporation on volatilization. The modified flow profile in the glass dome of the chamber arising from the use of a high-performance metal bellows pump was measured. Diminished air velocity near the soil surface and a wind velocity of 0.2 m/s in 3 cm height allowed the requirements of the German guideline on assessing pesticide volatilization for registration purposes to be fulfilled. Determination of soil moisture profiles of the upper soil layer illustrated that defined water content in the soil up to a depth of 4 cm could be achieved by water saturation of air. Cumulative volatilization of [phenyl-UL-14C]parathion-methyl ranged from 2.4% under dry conditions to 32.9% under moist conditions and revealed the clear dependence of volatilization on the water content in the top layer.
Wolters
André
A
Forschungszentrum Jülich, Institute of Chemistry and Dynamics of the Geosphere IV: Agrosphere, 52425 Jülich, Germany. a.wolters@fz-juelich.de
Kromer
Thomas
T
Linnemann
Volker
V
Schäffer
Andreas
A
Vereecken
Harry
H
D000388:Air / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry*; D002250:Carbon Radioisotopes; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods*; D006813:Humidity; D007306:Insecticides / Q000032:analysis / Q000737:chemistry; D008743:Methyl Parathion / Q000032:analysis / Q000737:chemistry; D009330:Nebulizers and Vaporizers; D015203:Reproducibility of Results; D012987:Soil / Q000032:analysis; D012989:Soil Pollutants / Q000032:analysis; D014835:Volatilization; D014874:Water Pollutants, Chemical / Q000032:analysis
D000393:Air Pollutants; D002250:Carbon Radioisotopes; D007306:Insecticides; D012987:Soil; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D008743:Methyl Parathion