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Environmental fate & pathways

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The photodegradation of benzophenone in air by reaction with OH radicals was calculated using EPIWIN v4.0, AOPWIN v1.92. Based on the reaction rate constant k(OH)=3.5549 x 10E-12 cm³/molecule x sec and assuming a tropospheric OH radical concentration of 5 x 10E5 radicals/cm³ a half-life t1/2=4.5 d is obtained. After irradiation of aqueous solutions of benzophenone with artificial UV or sunlight 4 -hydroxy and 3 -hydroxybenzophenone were identified as photoproducts. Benzophenone was shown to be photodegraded at low concentrations in pure water as well as in non-polluted surface water from East Lake and Changjiang River (Wuhan, China). The wavelength-averaged (250 -350 nm) quantum yields of benzophenone were determined to be 0.0013 +/- 0.001. Half-life times (1/2) of 16.23, 10.62, and 8.672 h were determined for the photlytic degradation of benzophenone in pure water, East Lake water, and Changjiang water. It could be shown that the presence of Cl(-), Fe(3 +), and humic acids, the initial benzophenone concentration, a continuous benzophenone input, the presence of benzophenone analogues influenced the degradation rate.

In a study conducted according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test), benzophenone proved to be readily biodegradable according to OECD criteria (66 -84% degradation after 28 days). The enrichment culture of the microbial strain MU-1 (black yeast Rhinocladiella aquaspersa) isolated from activated sludge was able to degrade benzophenone: Low benzophenone concentrations were degraded by more than 95% within several days (degradation: 100 mg/L within 3 d; 1000 mg/L within 7 d). Based on GC/MS analysis, benzophenone was degraded into hydrophilic compounds with very low molecular mass via conversion to phenol. Furthermore, low concentrations of benzophenone were found to be biodegraded by microbes occurring in unpolluted natural water samples. The rates of microbial degradation, however, were different due to the different composition and amounts of microbes (East Lake water: ca. 50% degradation after 12 d; Changjiang River water: ca. 25% degradation after 12 d).

Oryzias latipes exposed to benzophenone concentrations of 0.3 and 0.03 mg/L showed low BCF values (BCF=3 -12). Based on these results the potential for bioconcentration in aquatic organisms is low. The Kd of benzophenone for red earth, Australia, was determined to be 2.71 which corresponds to a Koc of about 430. The average of three soils resulted in a Koc of 517. Based on these findings, benzophenone is expected to have moderate to low mobility in soil. The calculation of Henry's Law Constant yielded a value of 0.197 Pa m³/mol which indicates that benzophenone can be regarded as moderately volatile from water surfaces. Benzophenone is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions.

In the years 2001 to 2003 surveys in Italy and Korea were conducted on the occurrence of benzophenone in samples of water, sediment, soil and biota collected from areas polluted both by municipal as well as industrial wastes.

Between October 2001 and July 2002, samples from water, sediment and biota (Mediterranean mussel, Mytilus galloprovincialis) were collected at 4 locations in the Venice lagoon (Italy), a highly urbanized coastal and heavily polluted water ecosystem that receiving both industrial and municipal wastewater effluents. Like most other targeted compounds, benzophenone was found in water and sediment samples in very low concentrations of <2.6–136 ng/L (water; MDL 0.1-2.6 ng/l) and 14–110 μg/kg, dw (sediment; MDL 0.2-5.0 μg/kg dw). Despite its occurrence in water and sediment, benzophenone could not be detected (MDL 0.3 to 5.0 ng/g dw) in the Mediterranean mussel Mytilus galloprovincialis. These results indicate either a very low bioavailability and/or a rapid metabolization of benzophenone even in a species representing a filtering organism of this estuarine ecosystem with a great ability in bioaccumulating persistent pollutants

In 2003, the occurrence of benzophenone was investigated in water and sediment of rivers, lakes as well as industrial effluents (15 sites) in areas of Korea, affected by municipal and recreational wastewater. Benzophenone could not be detected in water samples of lakes (n=6, MDL: 5 ng/L) and rivers (n=25, MQL: 25 ng/L), whereas substance concentrations found in industrial effluent samples ranged from 32 -51 ng/L (mean: 44 ng/L, frequency: 4/7 (57%)). In sediment samples benzophenone concentrations ranged from 1520 -9730 ng/kg (mean: 4730 ng/kg, frequency: 14/15 (93%)). In ground soil samples collected from various areas spread out in residential, park, commercial and industrial areas with dense population (33 sites), benzophenone concentrations ranging from 820 to 16550 ng/kg were detected.