Indirect photolysis half-life

Illustrative Example 16.2 Estimating the Indirect Photolysis Half-Life of Atrazine in a Shallow Pond Reactions with Singlet Oxygen ( 02)... 

The indirect photolysis half-life of atrazine (assuming that reaction with HO is the dominant process) is then given by (Eq. 16-7) ... 

Estimating the Indirect Photolysis Half-Life of Atrazine in a Shallow Pond... 

It was previously noted that no evidence for direct photolysis for PFOS or PFOA has been observed experimentally. In aqueous solutions alone and in the presence of hydrogen peroxide (H2O2), iron oxide (Fe203) or humic material, PFOS has been observed to undergo some indirect photolysis [28] whereas PFOA did not undergo indirect photolysis [29]. Using an iron oxide photo-initiator matrix model, the indirect photolytic half-life for PFOS was estimated to be > 3.7 years at 25 °C. The half-life of PFOA was estimated to be > 349 d. 

PROBABLE FATE photolysis, photooxidation to chlorinated biphenyls and benzophe-nones probable, indirect photolysis may be significant based on the behavior of the related compound DDT, direct photolysis half-life in water >150 yrs, photooxidation half-life in air 13.3-133 hrs oxidation, not an important process, vapor phase half-life in the atmosphere 1.71 days from reaction with photochemically produced hydroxyl radicals hydrolysis, not an important process, will not hydrolyze in soil volatilization expected to be an important process, evaporation half-life 1.82 days from a river 1 m deep, flowing at Im/sec with a wind velocity of 3 m/sec sorption is an important process, expected to adsorb to sediment if released to water biological processes biotransformation and bioaccumulation are important processes biodegradation expected to be slow... 

PROBABLE FATE photolysis no direct photolysis, half-life from surface waters 3500 hr, indirect photolysis is too slow to be important, photodegradation by hydroxyl radicals will occur with a half-life of 23.8 hrs oxidation not an important process, photooxidation half-life in air 4.7 days-46.6 days hydrolysis too slow to be important under natural conditions, first-order hydrolytic half-life 1163 days volatilization possible, but not important sorption sorption onto particles and biota and complexation with humic substances principal transport mechanism, little adsorption to soil or sediment is expected to occur biological processes bioaccumulation, biodegradation, and biotransformation by many organisms (including humans) are very significant fates... 

Theoretical calculations indicate a low stability for 21128 . The above reaction was examined by the technique of flash photolysis and kinetic mass spectrometry and a strong signal for the species C2H2S was observed, with a decay half-life of ca. 2 sec. Indirect, though compelling, evidence was presented to the effect that the signal was not due to a thioketene intermediate, CH2-C-S. Thiirene reacts rapidly with triple bonds to produce thiophenes, viz. 

PROBABLE FATE photolysis direct photolysis is slow, indirect photolysis may be important, vapor phase aldrin residues expected to react with photochemically produced hydroxyl radicals with a half-life of 35.46 min oxidation reacts to form dieldrin, photooxidation by ultraviolet light in aqueous medium 90-95°C forms 25% CO2 in 14.1 hr, 50% CO2 in 28.2 hr, 75% CO2 in 109.7 hr, photooxidation half-life in air 0.9-9.1 hrs hydrolysis too slow to be an important process volatilization an important process, evaporation rate from water 3.72x10 m4ir, will volatilize from soil surfaces sorption an important process, adsorption to sediment is... 

PROBABLE FATE photolysis, direct photolysis is improbable, indirect photolysis is too slow to be important, aqueous photolytic half-life 100 yrs oxidation could occur, but could probably not compete with degradation, photooxidation half-life in air 2.5 days hydrolysis too slow to be important, half-life is greater than 100 days volatilization not expected to be a likely transport process, will volatilize under windy conditions or from shallow waters sorption sorption onto particulates and complexation with organic substances are dominant transport processes, expected to adsorb if released to soil biological processes bioaccumulated and metabo-... 

PROBABLE FATE photolysis photooxidation to DDE occurs slowly, indirect photolysis may be important oxidation photoxidation occurs, photooxidation half-life in water 7-350 days, photoxidation half-life in air 7.4 days hydrolysis may be an important process under certain conditions, first-order hydrolytic half-life 22 yrs volatilization is an important process, some will evaporate from soil and surface water into the air sorption is an important process, will adsorb very strongly to soil if released to the soil, will adsorb very strongly to sediments if released to water biological processes biotransformation and bioaccumulation are important processes, may be subject to biodegradation in flooded soils or under anaerobic conditions, may be significant in sediments... 

PROBABLE FATE photolysis no direct photolysis, indirect photolysis too slow to be environmentally important, photooxidation half-life in water 2.4-12.2 yrs, photooxidation half-life in air 7.4 hrs-2.5 days oxidation not important, reaction with photochemically produced hydroxyl radicals gives a half-life of 18 hrs hydrolysis hydrolysis (only in surface waters) believed to be too slow to be important, first-order hydrolytic half-life 10 yrs volatilization not expected to be an important transport process sorption sorption onto particulates and com-plexation with organics are dominant transport processes biological processes bioaccumulated in many organisms, biodegraded rapidly in natural soil, some biotransformation, all biological processes are important fates... 

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