Semi-empirical estimation of sorption of hydrophobic pollutants on natural sediments and soils

Methods were developed for estimating the equilibrium sorption behavior of hydrophobic pollutants. At low pollutant concentration (aqueous phase concentration less than half the solubility), sorption isotherms were linear, reversible, and characterized by a partition coefficient, K_p. Partition coefficients normalized to organic carbon, K_OC ($\text{K}{}_{\mathrm{OC}}\text{=}\text{K}{}_{\mathrm{p}}\text{fraction}$ organic carbon), were highly invariant over a set of sediments and soils collected from throughout the nation. Equations for estimating K_OC from water solubility (including crystal energy) and octanol/water partition coefficients were developed. The predictive equations were tested on literature sorption data and found to estimate measured K_OC's generally within a factor of two.     

Photochemistry and environment. VII- The photohydrolysis of chlorobenzene: Studies of the excited state involved

Chlorobenzene excited in dilute aqueous solution is transformed quantitatively into phenol ($\text{ф= 0.10±0.02}$). This reaction involves a triplet state, since it is quenched by biacetyl and sensitized by ketones. Based on quenching experiments, the lifetime of the lowest triplet of chlorobenzene was measured as 30 ns. From the sensitized phosphorescence of biactyl, the quantum yield of intersystem crossing (S₁→T₁) was found to be 0.6 ±0.1. The photophysical characteristics of chlorobenzene are identical in acetonitrile (). Photosensitization of the photohydrolysis is observed with acetone and acetone D6 in aqueous solution. The quantum yield of the sensitized photohydrolysis is limited to 0.06±0.01. Hexadeuterated acetone appeared to be a more specific photosensitizer than acetone.     

Bioaccumulation of pentachlorophenol by killifish (Fundulussimilus)

Killifish ($\text{Fundulus}$$\text{similis}$) were exposed in the laboratory to pentachlorophenol (PCP) at concentrations of 57 to 610 μg PCP/L. Bioaccumulation reached a plateau value of about 53 by 168 hrs and remained at this level for at least 72 hrs. One-half the plateau value was reached in about 25 hrs. Following exposure, fish placed in PCP-free aquaria lost PCP rather slowly ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{～ 4.7}\text{days}$). The depuration data were suggestive of a pool of PCP which was lost more rapidly ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{～ 4.2}\text{hrs}$). The results of this study are compared to similar studies in other species. The bioaccumulation factors measured in this study agree relatively well with those in other marine species, but are lower than reported for fresh water species. Possible reasons for this difference are discussed.     

Blood analysis of rabbits exposed to nitrogen monoxide

Rabbits exposed to NO-containing atmospheres develop an EPR signal in their blood which can be detected with good sensitivity following dithionite reduction and freezing to 160 K. The spectroscopic parameters indicate that NO is bound preferentially to the α chains of hemoglobin in the quaternary T state. The EPR signal intensity increases with time and with the concentration of NO but decreases rapidly ($\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{? 15}\text{min}$) when the rabbits are returned to clean air.