Sediment, sorbed hydrophobic halocarbons

Sorption of hydrophobic halocarbons onto suspended sediments, biota, or NOM can have complex effects on photoreaction rates and quantum efficiencies. Hydrophobic or ionic halocarbons, with their great tendency to sorb on sediments or NOM, are most likely to be affected by heterogeneous photoreactions. A flurry of publications (e.g., 30-34 and references cited therein) provided abundant experimental evidence that extremely hydrophobic pollutants (e.g., polycyclic aromatic hydrocarbons, DDT, and mirex) have a strong tendency to associate with the particulate and dissolved organic matter in water bodies. 

Halocarbons Sorbed on Sediments. If a significant fraction of halo-carbon is sorbed in an unreactive microenvironment, then the kinetics can become limited by exchange between the unreactive (U-P) and photoreactive (R-P) parts of the system. Intrasorbent transport limitations have been observed for extremely hydrophobic halocarbons sorbed on soils and sediments suspended in water. The photoreactions of DDE in sediment suspensions provide a good example of such transport limitation (Figure 2) (43). Plots of log concentration versus time were linear for DDE photoreaction in water, but nonlinear in the sediment suspensions (Figure 2). The degree of nonlinearity depended upon the equilibration time of the suspensions prior to irradiation. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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