Volatilization half-live

Mathematical modeling of trichloroethylene volatilization from a rapidly moving, shallow river (1 meter deep, flowing 1 meter per second, with a wind velocity of 3 meters per second) has estimated its half-life at 3.4 hours (Thomas 1982). Measured volatilization half-lives in a mesocosm, which simulated the Narragansett... 

Table II. Volatilization Half-Lives of DBCP Mixed Into 10 cm of Several Kinds of Soils (day)...

Volatilization half-lives from solution 97, 108 min (exptl., calculated, Mackay et al. 1983). 

Pal et al. [368] gave volatilization half-lives reported in the literature for a number of Aroclors, ranging from 10-12 days for pure water and up to 52 days... 

Volatilization is the most important removal process for 1,2-dibromoethane released to surface waters. Volatilization half-lives of 1-16 days have been estimated for flowing and standing surface waters. Sorption to sediment or suspended particulate material is not expected to be an important process (EPA 1987a, 1987b HSDB 1989). 

Mackay and Wolkoff (1973) estimated an evaporation half-life of 10.1 d from a surface water body that is 25 °C and 1 m deep. Singmaster (1975) studied the rate of volatilization of aldrin (1 ng/L) in a flask filled with 0.9 L water obtained from California. The flask was gently stirred and an air stream was passed over the air-water interface. He reported volatilization half-lives of 0.38, 0.59, and 0.60 h from San Francisco Bay, American River, and Sacramento River, respectively. 

The volatilization half-lives of 2-chlorophenol in stirred and static water maintained at 23.8 °C were 1.35 and 1.60 h, respectively (Chiou et al., 1980). 

Surface Water. Plimmer et al. (1973) reported that the photolysis half-life of TCDD in a methanol solution exposed to sunlight was 3 h. Volatilization half-lives of 32 and 16 d were reported for lakes and rivers, respectively (Podoll et ah, 1986). 

TrCDD). Thus, volatilization from the water column is not expected to be a very significant loss process for the TCDD through OCDD congeners as compared to adsorption to particulates. In general, the Henry s law constants decrease with increasing chlorine number as a result of the decrease in vapor pressure and water solubility (Shiu et al. 1988). Volatilization half-lives for 2,3,7,8-TCDD were calculated for ponds and lakes (32 days) and for rivers (16 days) (Podoll et al. 1986). The primary removal mechanism for CDDs from the water column is sedimentation, with 70-80% of the CDDs being associated with the particulate phase (Muir et al. 1992). The remainder was associated with dissolved organic substances. CDDs bound to sediment particles may be resuspended in the water column if the sediments are disturbed. This could increase both the transport and availability of the CDDs for uptake by aquatic biota (Fletcher and McKay 1993). 

Surface water ty, = 24-168 h, based on unacclimated freshwater grab sample data (Hammerton 1955 selected, Howard et al. 1991) and aqueous screening test data (Bridie et al. 1979 selected, Howard et al. 1991) photooxidation t,/, = 2602-104000 h, based on measured rate constant for reaction with hydroxyl radicals in aqueous solution (Dorfman Adams 1973 selected, Howard et al. 1991) estimated volatilization half-lives, = 2.4 h in streams, ty = 3.9 h in rivers and ty = 125.9 h in lakes (Lyman et al. 1982 quoted, Howard 1990). 

The major environmental fate processes for butyraldehyde in water are biodegradation and volatilization. A number of biological screening studies have demonstrated that butyraldehyde is readily biodegradable. Volatilization half-lives of 9h and 4.1 days have been estimated for a model river (Im deep) and an environmental pond, respectively. Aquatic hydrolysis, adsorption to sediment, and bioconcentration are not expected to be important fate processes. 

Vinylidene chloride is a human-made chemical and is not naturally found in the environment. It can be found from the breakdown of polyvinylidene (PVDC) products, and from the biotic and abiotic breakdown of 1,1,1-trichloroethane, tetrachloroe-thene, 1,1,2-trichloroethene, and 1,2-dichloroethane. Biotransformation of the chemical in groundwater can form vinyl chloride through reductive dechlorination, which is subsequently mineralized to carbon dioxide. The major transport process from water, soil and sediment is volatilization. Half-lives of... 

Piwoni et al. (1986) found that nitrobenzene did not volatilize in their microcosms simulating land-application of wastewater, but was totally degraded. Enfield et al. (1986) employed a calculated Henry s law constant of 1.30 x 10 kPa m mol, and arrived at a biodegradation rate coefficient greater than 8 day . They predicted that 0.2% of the added nitrobenzene could be accounted for in volatiles. The EXAMS computer model (Burns et al. 1981) predicts volatilization half-lives of 12 days (river) to 68 days (eutrophic lake) and up to 2% sediment sorption for nitrobenzene. 

Using a two film model, the volatilization half-lives for 2,3,... 

PROBABLE FATE photolysis-, aqueous photolysis is not expected to be important, reaction with photochemically produced hydroxyl radicals has a half-life of 13.44 hr, direct photolysis is not expected to be important since it should not adsorb wavelengths >290 nm oxidation photooxidation is not expected to be important, photooxidation only in atmosphere, photooxidation half-life in air 9.65 hrs-4.02 days hydrolysis very slow, maybe significant, hydrolysis of carbon-chloride bonds, release to water results in hydrolysis with a half-life of 40 days when released to soil, it may hydrolyze hydrolyzed slowly in aqueous dimethylformamide at pH 7, first-order hydrolytic half-life 22yrs volatilization expected to volatilize if released to water, volatilization half-lives from lakes, rivers, and streams 3.5, 4.4, and 180.5 days respectively sorption not an important process biological processes biodegrades in water after several weeks of acclimation, biodegradation not important under natural conditions, no bioaccumulation noted... 

PROBABLE FATE photolysis-, direct photolysis is probably not important, if released to atmosphere, will degrade by reaction with photochemically produced hydroxyl radicals (estimated half-life 1.15 days) oxidation photooxidation in atmosphere can occur, photooxidation half-life in air 4.61-46.1 hrs hydrolysis slow hydrolysis of carbon-chlorine bond, may be important fate mechanism volatilization if released to water, volatilization is expected to be the principle removal process, but may be slow, volatilization half-lives for a model river (1 m deep) and a model environmental pond 13.9 hr, and 6.6 days respectively sorption adsorption on organic matter is possible biological processes no data on bioaccumulation or biodegradation... 

PROBABLE FATE photolysis, may be important, but is probably impeded by adsorption, photooxidation by U.V, in aqueous medium (Ty 90-95°C time for the formation of CO, (% of theoretical) 25% 75.3 hr, 50% 160.6 hr, 75% 297.4 hr, photooxidation half-life in air 6.81 hrs-2.i du>s, degrades quickly by photochemically produced hydroxyl radicals, with an estimated half-life of 29 hr oxidation-, chlorine and/or ozone in sufficient quantities may oxidize fluorene hydrolysis, not an important process volatilization probably not an important transport process, volatilization half-lives from a model river and a model pond 15 and 167 respectively sorption adsorption onto particles, biota, and sediments is probably the dominant transport process, half-life in soil ranges from 2-64 days biological processes bioaccumulation is short-term, metabolization and biodegradation are very important fates in estuarine waters 15pg/L, 12% adsorbed on particles after 3 hr... 

The actual rate of volatilization of plasticizers from water apparently has not been experimentally measured. The rates of volatilization, however, estimated using the Sonth-worth Method to estimate gas-phase and liqnid-phase mass transfer coefficients, were reported in HSDB, and summarized in Table 18.10. VolatiUzation was estimated nnder two scenarios (Figure 18.1) a shallow (1-m deep) river moving at a rate of 1 m/sec below an air mass moving at 3 m/sec. The second scenario was a shallow (1-m deep) lake moving at 0.05 m/sec below a breeze of 0.5 m/sec. The estimated volatilization half-lives of the plasticizers followed the trend established by their Heniy Law constants. Consequently, the predicted half-lives of ditridecyl phthalate, di-(2-ethylhexyl) adipate, di-(2-ethylhexyl) azelate, diundecyl, diisooctyl, dihexyl, dinonyl phthalate were less than 6 days. The same plasticizers would likely be more persistent in the lake scenario. The volatilization rates of the other plasticizers appeared to be much slower, and volatilization from water may not be a significant environmental pathway. Furthermore, the Southworth estimation technique does not take into acconnt sorption of dissolved chemicals by suspended particles. Sorption would increase the residence time of dissolved plasticizers. The predicted volatilization rates, however, were based on Hemy s Law constants which are themselves only estimates. 

Table 18.10. Estimated volatilization half-lives of the 23 plasticizers from water (from...

Chemical/Physical. The reported hydrolysis half-lives of cw-mevinphos and trans-mevinphos at pH 11.6 are 1.8 and 3.0 hours, respectively (Casida et al., 1956). The volatility half-lives for the cis and trans forms at 28°C were 21 and 24 hours, respectively (Casida et al., 1956). Worthing and Hance (1991) reported that at pH values of 6, 7, 9 and 11, the hydrolysis half-lives were 120 days, 35 days, 3.0 days and 1.4 hours, respectively (Worthing and Hance, 1991). 

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