Comparative effectiveness of natural by-products and synthetic sorbents in oil spill booms.

Sorbent booms are considered a 'first line of defence' technology used for containing and minimizing the impacts of crude oil spills. Booms containing human hair waste as sorbent were compared to other natural sorbents, including cotton by-product, recycled cellulose, as well as booms containing synthetic polypropylene, in order to evaluate their effectiveness in adsorbing petroleum crude oil pollution, remaining buoyant, and adsorbing seawater. A series of oceanic mesocosm experiments were used to simulate oil spill pollution events and to test sorbent effectiveness. Hair by-product was found to be significantly better at adsorbing crude oil on average (i.e. 0.84 g of crude oil per 1 g of sorbent) than all other materials, although it had wider variation in adsorbency likely associated with the non-homogeneous nature of mixed human hair. Hair sorbent was also observed to be less naturally buoyant than other materials, potentially due to low surface tension or increased porosity.

Differences in leaf flammability, leaf traits and flammability-trait relationships between native and exotic plant species of dry sclerophyll forest.

The flammability of plant leaves influences the spread of fire through vegetation. Exotic plants invading native vegetation may increase the spread of bushfires if their leaves are more flammable than native leaves. We compared fresh-leaf and dry-leaf flammability (time to ignition) between 52 native and 27 exotic plant species inhabiting dry sclerophyll forest. We found that mean time to ignition was significantly faster in dry exotic leaves than in dry native leaves. There was no significant native-exotic difference in mean time to ignition for fresh leaves. The significantly higher fresh-leaf water content that was found in exotics, lost in the conversion from a fresh to dry state, suggests that leaf water provides an important buffering effect that leads to equivalent mean time to ignition in fresh exotic and native leaves. Exotic leaves were also significantly wider, longer and broader in area with significantly higher specific leaf area-but not thicker-than native leaves. We examined scaling relationships between leaf flammability and leaf size (leaf width, length, area, specific leaf area and thickness). While exotics occupied the comparatively larger and more flammable end of the leaf size-flammability spectrum in general, leaf flammability was significantly correlated with all measures of leaf size except leaf thickness in both native and exotic species such that larger leaves were faster to ignite. Our findings for increased flammability linked with larger leaf size in exotics demonstrate that exotic plant species have the potential to increase the spread of bushfires in dry sclerophyll forest.