An advanced analytical approach to assess the long-term degradation of microplastics in the marine environment

Abstract Determining the hazards posed by microplastics (MPs, <5 mm) requires an understanding of plastic degradation processes when exposed to environmental weathering forces. However, despite their perceived risks, limited information exists on the natural weathering progression of microplastics in marine environments. Our findings from environmentally realistic conditions reveal that long-term marine weathering resulted in significant degradation of plastic surfaces and bulk-phases, which varied by time and plastic polymer type. Plastics displayed biofouling, and an altered surface morphology, thermal stability and chemical signature. Secondary micronanoplastics (MNPs, <1 µm) were formed from weathered plastic surfaces, supported by a significant reduction in the size of PCL and PVC pellets. Using real world data, we reveal that plastic surfaces can degrade at a rate of up to 469.73 µm per year, 12 times greater than previous estimates. Our time-series data contributes valuable information towards developing plastic specific risk assessment frameworks and future plastics policy

How small is the big problem? Small microplastics <300 μm abundant in marine surface waters of the Great Barrier Reef Marine Park.

Particle size plays an important role in determining the behaviour, fate and effects of microplastics (MPs), yet little is known about MPs <300 μm in aquatic environments. Therefore, we performed the first assessment of MPs in marine surface waters around the Whitsunday Islands region of the Great Barrier Reef Marine Park, Australia, to test for the presence of small MPs (50-300 μm) in-situ. Using a modified manta net, we demonstrate that MPs were present in all marine surface water samples, with a mean sea surface concentration of 0.23 ± 0.03 particles m-3. Microplastics were mainly blue, clear and black fibres and fragments, consisting of polyethylene terephthalate, high-density polyethylene and polypropylene plastic polymers. Tourism and marine recreation were considered the major contributing sources of MPs to surface waters around the Whitsunday Islands. Between 10 and 124 times the number of MPs exist in the 50 μm-300 μm size class, compared with the 1 mm-5 mm size range. This finding indicates that the global abundance of small MPs in marine surface waters is grossly underestimated and warrants further investigation. Research into the occurrence, characteristics and environmental fate of MPs <300 μm is needed to improve our understanding of the cumulative threats facing valuable ecosystems due to this smaller, potentially more hazardous size class

Physical stature in nineteenth-century new zealand: A preliminary interpretation

During the late nineteenth century, the physical stature of New Zealand-born men stagnated, despite an apparently beneficial public health environment and growth in per-capita incomes. We examine trends and differentials in male stature through World War I enlistment and casualty records. Stature varied by social class, with professionals and men in rural occupations substantially taller than their peers. There is not enough evidence to show that the indigenous Maori population differed in height from men of European descent. Stagnation in stature in late nineteenth-century New Zealand is consistent with patterns observed in Australia, North America, and Western Europe. © 2010 The Authors. Australian Economic History Review© Blackwell Publishing Asia Pty Ltd and the Economic History Society of Australia and New Zealand 2010