Heterogeneous weathering of polypropylene in the marine environment.

Polypropylene (PP) inkjet cartridges spilled during January 2014 in the northwest Atlantic Ocean from a container ship and subsequently retrieved from beaches around Europe and the Azores along with a matching reference cartridge that had not been exposed to the environment were physically and chemically characterized. Compared with the reference, the cartridges retrieved from the marine environment exhibited considerable cracking-fracturing, discoloration, surface roughness, loss of gloss and staining. Infrared analysis revealed that weathering was highly heterogeneous, with the carbonyl index ranging from <0.1 to >0.9 over areas of sub-mm-dimensions. The high degree of weathering was partly attributed to the presence, quality, and distribution of the titanium dioxide pigment, TiO2. Thus, in the absence of sufficient protection by encapsulation or addition of antioxidants, the ultraviolet light-absorbing pigment promoted the formation of free radicals and photocatalytic oxidation. The results of this study show that consumer plastics containing TiO2 for coloration or tinting purposes, when not designed for exterior use (in the absence of encapsulation or antioxidants), may experience accelerated weathering in the marine environment, and that estimates of plastic persistence should factor in the role of additives that promote photoactivity.

Survival and drifting patterns of grass carp eggs and larvae in response to interactions with flow and sediment in a laboratory flume.

A series of laboratory experiments was conducted to better understand the behavior of grass carp eggs and larvae in moving water in order to develop and implement new strategies for control and prediction of their dispersal and drift at early life stages. Settling velocity and density of a representative sample of eggs were estimated, and three trials of flume experiments with different flow conditions were conducted with live eggs in a temperature-controlled setting with a mobile sediment bed. In these trials, egg and larval stages were continuously analyzed over periods of 80 hours; and eggs and larvae interactions with the flow and sediment bed were monitored and characterized qualitatively and quantitatively. Survival rates were quantified after each trial, highlighting physical causes for increased mortality. Detailed flow analysis was correlated to the observed drifting and swimming behavior of eggs and larvae, to estimate distributions across the water depth, as well as traveling and swimming speeds. Evidence of the influence of mean and turbulent flow in the suspension and transport of eggs are reported, and swimming patterns of larvae at different developmental stages are described. These findings support the development of new strategies for monitoring the spread of grass carp eggs and larvae in rivers, and provide new inputs to predict conditions favorable for spawning and hatching, allowing for mitigation measures at early life stages, which are critical to control their dispersal.