The energetics of the TiO2 polymorphs (rutile, anatase, and brookite) were studied by high temperature oxide melt drop solution calorimetry. Relative to bulk rutile, bulk brookite is 0.71 ؎ 0.38 kJ͞mol (6) and bulk anatase is 2.61 ؎ 0.41 kJ͞mol higher in enthalpy. The surface enthalpies of rutile, brookite, and anatase are 2.2 ؎ 0.2 J͞m 2 , 1.0 ؎ 0.2 J͞m 2 , and 0.4 ؎ 0.1 J͞m 2 , respectively. The closely balanced energetics directly confirm the crossover in stability of nanophase polymorphs inferred by Zhang and Banfield (7). An amorphous sample with surface area of 34,600 m 2 ͞mol is 24.25 ؎ 0.88 kJ͞mol higher in enthalpy than bulk rutile.

No abstract

No abstract

No abstract

No abstract

No abstract

The sorption and degradation of the rice pesticides fipronil and thiobencarb on 2 Australian rice-growing soils were investigated. Greater sorption of both pesticides occurred on the soil containing less organic carbon, possibly as a result of the type of organic carbon present, rather than the absolute amount. While sorption tended to appear greater in the 0–10 mm layer than the 10–20 mm layer, analysis showed the difference was not significant (P > 0.05). Under aerobic conditions, a lag period of 20 days in the degradation of thiobencarb occurred on the Yanco soil, but rapid degradation occurred on the Coleambally soil, and, while unlikely, may have been a consequence of preconditioning of the Coleambally soil microbial population. Degradation of thiobencarb under both non-flooded anaerobic and flooded anaerobic conditions differed significantly (P < 0.05) compared to aerobic conditions. Conversely, fipronil degraded rapidly over the first few days and then slowed, and was attributed to the co-metabolism of fipronil by soil microbes. While fipronil sulfide was produced under all oxic/anoxic conditions, its concentration was greatest under flooded anaerobic conditions, possibly as a result of greater exclusion of oxygen from the soil by the floodwater.

No abstract