Evaporated residues, fate

On the other hand, the ultimate fate of pelagic tar lumps and other petroleum residues in the ocean is largely unknown. Although tar is found on island beaches, coastal stranding in the open ocean cannot be a major mechanism for removal. For a fraction of the petroleum residues, evaporative weathering (10,11) and microbial degradation (13) appear to be significant mechanisms of removal. Evaporation is normally limited to the more volatile fractions (below Ci6-i8 for paraffins). 

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... 

As other sections of this Handbook indicate, there have been eonsiderable efforts to model and predict the short-term fate of spilled hazardous materials over hours and days. These include estimates of spreading, evaporation, atmospheric dispersion, and flow in surface waters and groundwaters. A major incentive for such models is the protection of the public and remedial action personnel. Less attention is paid to the longer-term fate of the spilled material over months and years. In this section, we review the use of mass balance models to predict the long-term fate of spilled materials. Ultimately, the residual spUled material combines with the existing contaminant burden in the environment to raise general concentration levels and increase overall human exposure. The focus is thus on chronic exposure as distinct from short-term acute exposure, which is the primary initial concern of response agencies. 

Environmental (e.g., surface and crop leaf residues) and work-place exposures (e.g., mixer-loaders, applicators, etc.) may result in the transfer of pyrethroids to skin where they may be absorbed. Dermal PBPK/PD models require compartment/ submodels and additional parameters (e.g., Kp, permeation constants, exposed surface area, evaporation rates, washoff fractions, etc.) to model the fate of pyrethroids deposited on the skin. 

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