TiO2-induced heterogeneous photodegradation of a fluorotelomer alcohol in air

Degradation of C4F9C2H4OH in air over TiO2 particles was examined in this first report of gas-solid heterogeneous photochemical degradation of fluorotelomer alcohols (FTOHs), which may be precursors of perfluorocarboxylic acids (PFCAs) in the environment. Photoirradiation (>290 nm) of C4F9C2H4OH in air flowing over TiO2 produced CO2, via C4F9CH2CHO, C4F9CHO, CnF(2n+1)COF (n=2 and/or 3), and COF2, in that order. X-ray photoelectron spectroscopy of the Ti02 surface showed a decrease in the amount of fluorine bonded to carbon and an increase in the amount of F- as the degradation of C4F9C2H4OH in air proceeded. Of the carbon content in the initial C4F9C2H4OH (78.8 ppmv), 90.7% was transformed to CO2, and the predominant fluorine species produced on the TiO2 surface was F-. Fluorotelomer unsaturated acids, which are considered to be toxic and have been observed in the biodegradation of FTOHs, did notform. Increased relative humidity in the air accelerated the decomposition of the reaction intermediates, which led to increased CO2 and F- formation. This result indicates that humidity is a key factor for counteracting FTOHs in indoor air. Although perfluoroalkyl substances such as PFCAs in water reportedly undergo little photodegradation over TiO2, our data show that mineralization of C4F9C2H4OH in air can be achieved with TiO2.     

Causes of animal extinction in small irrigation reservoirs in Japan and requirements for future re-establishment

In the past, small irrigation reservoirs were constructed only for rice paddy irrigation in Japan. Many of the watersheds for these irrigation reservoirs were forests. These watersheds have been gradually developed into farmland or housing areas. After World War II, the use of chemical fertilizers, such as ammonium sulphate, became popular in upland fields in Japan. As a result, there are high concentrations of nitrates in groundwater and spring water under upland fields. Hence, irrigation reservoirs that collect water from these watersheds have been polluted by nitrates. High nitrates concentrations in irrigation reservoirs have been found where the watershed is located close to tea yards. However, there has been minimal research into these reservoirs in the fields of limnology and agricultural engineering. We have therefore tried to verify the water‐quality characteristics in irrigation reservoirs from the point of view of water‐quality conservation. In the process of the investigation, we encountered a quite significant reservoir called the Tanno Reservoir that has not seen any forms of life. We examined the causes of this lack of life, as well as measures that could be taken for the remediation of such a reservoir. This paper discusses and clarifies the results of these studies.