Polypropylene litter

In the South Pacific, man-made debris was surveyed on 24 islands in the Thousand Island archipelago north of Java in 1985 (66). Polyethylene bags, footwear and polystyrene blocks comprised more than 90% of the 27,600 items. The main source of this debris is the dumping of rubbish and domestic and industrial waste directly into the sea at Jakarta. On New Zealand beaches, plastic litter was widely distributed and predominantly in the form of polyethylene and polypropylene beads. Near Auckland and Wellington concentrations exceeded 10,000 and 40,000 beads m of beach, and the unweathered appearance of the beads implied a nearby source (66). 

The most common litter item are small pieces of plastics whose lengths are on the order of a few millimeters. An important component are thermoplastic resin pellets and beads that are raw materials, mostly polypropylene and polyethylene, intended for manufecture into commercial items. Loss during ship transport and stormwater runoff are major sources of the pellets and beads to the ocean. Densities of 3500 per km have been reported floating on the surfece in the Sargasso Sea. On the beaches of New Zealand located near industrialized areas, concentrations as high as 100,000 per km are now being observed. The pellets and beads are carried by currents until they are either... 

Degradation prodncts from macrolitter have different properties at sea, different effects and different futnies from the original products. Eventually, they form microparticles, usually made of plastic, which constitute a veiy important aspect of the problem of marine litter. They comprise an assembly of objects of varying size, shape, color, density and chemical composition [HID 12]. With densities ranging from 0.8 to 1.4 g cm", the plastics in the sea and on the surface are mainly polyethylene (density 0.92-0.97 g cm ), polypropylenes (0.85-0.94 g cm ) and polystyrenes (from less than 0.05 in the case of foamed polystyrene to 1.00 g cm ) [LES 11]. The denser plastics such as poly (vinyl chloride) (PVC) and polycarbonates, if they do not aggregate with the organic material, tend to sink. 

Table 1. Mass (g diy weight m-2) of remaining and percent (%) of initial mass of exposed natural plant (NPL) and polypropylene (PP) litter during the course of the experiment. Significance of differences between treatments are assessed by non-parametric Wilcoxon Sum-of-Ranks (Mann-Whitney) test. AH data from five natural litter treatments (I Dactylis glomerata II Festuca rubra and III Trijblium pratense), IV mixture of three species I, II and III V mixture of twelve species, IV and nine other meadow plants) were analyzed with the exception of month where only data of treatments I and HI were used. Standard errors in parentheses.

The technology and role of photodegradable plastics is considered and computer models are described to evaluate strategies for litter abatement, and experimental studies of the synthesis and biodegradation of conventional and photodegradable polyethylene, polypropylene, poly(ethylene terephthalate), and polystyrene. 

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