EFFECT OF LIGHT ON BIODEGRADATION OF ESTRONE, 17β-ESTRADIOL, AND 17α-ETHINYLESTRADIOL IN STREAM SEDIMENT1

Biodegradation of [A-ring C-14] Estrone (E1), 17-estradiol (E2), and 17-ethinylestradiol (EE2) to (CO2)-C-14 was investigated under light and dark conditions in microcosms containing epilithon or sediment collected from Boulder Creek, Colorado. Mineralization of the estrogen A-ring was observed in all sediment treatments, but not epilithon treatments. No difference in net mineralization between light and dark treatments was observed for C-14-E2. Net mineralization of C-14-E1 and C-14-EE2 was enhanced in light treatments. Extents of (CO2)-C-14 accumulation and rates of mineralization were significantly greater for E2 than E1 under dark conditions, but were comparable under light conditions. These results indicate substantial differences in the uptake and metabolism of E1 and E2 in the environment and suggest biorecalcitrance of E1 relative to E2 in light-limited environments. The extent of (CO2)-C-14 accumulation and rate of mineralization for EE2 in dark treatments were less than half of that observed for E2 and generally lower than for E1, consistent with previous reports of EE2 biorecalcitrance. However, (CO2)-C-14 accumulation and rates of mineralization were comparable for EE2, E2, and E1 under light conditions. These results indicate photoactivation and/or phototransformation/photodegradation processes can substantially enhance heterotrophic biodegradation of estrogens in sunlit environments and may play an important role in estrogen transport and attenuation.