Plastics detritus

Man-made litter is more aesthetically objectionable to humans than biological waste. The reasons for this are deeply rooted in the human subconscious because it is evidently not natural . Plastics detritus is much more noticeable in fields and on the sea-shore and, even when it is ploughed into the soil, it interferes with plant growth. 

Microlitter is inconspicuous, fine plastic detritus with a size range of very fine sand to coarse silt usually found in the marine sediment. On washing it passes through a 500-ttm sieve but is retained on one at 63 p,m. 

Eco-toxicity requirements of degradable plastics in soil Seed germination is compared with that of soil that contains no plastic particles in Table 5 (from unpublished work by Raninger, Section 6.3) for a typical agricultural degradable plastic (EPI TDPA ). It is evident that the plastics detritus has no adverse effect on the germination rate of either seeds. 

The growth rate of typical crop plants in compost to which partially degraded plastics have been added is shown in Table 6 [36] for the same plastics. Again there is no evidence that fragmented plastics have any effect on plant growth and within the limits anticipated from year to year, the loading of plastics detritus appears to make little difference to crop yields. 

Tin appears in seafood as butylated tin compounds and as methyltin compounds in leachate from plastics. Tributyltin was used for many years to control barnacles and other marine growths on the hulls of ships. These organisms attached to the ships increase the drag on the ships and make them less energy efficient. Tributyltin leaches from the paint into the surrounding waters and can reach levels of concern in eonfined areas, such as harbors. Filter feeding organisms, such as oysters and mussels, as well as detritus feeders accumulate butyltin compounds and these compounds... 

Not unexpectedly, in the light of the above, there are no published test methods for the biodegradation of plastics litter. The primary requirement is that the detritus breaks down into small particles in a matter of... 

The terrestrial component of the dust particles embedded in the ice consists of volcanic ash, finegrained dust derived from soil on the continents, carbon particles released by forest fires, biogenic particles (e.g., the skeletons of diatoms, seeds, and pollen grains), aerosol particles of atmospheric origin, including sea-spray particles that nucleate snow flakes (Section 17.10). In addition, the uppermost layer of snow and fim that was deposited after the start of the Industrial Revolution (i.e., post ad 1850) contains anthropogenic detritus such as flakes of metal, paint, and plastics, fly-ash particles and other combustion products, fibers (composed of wood, cotton, and synthetics), industrial contaminants (e.g., lead), and radioactive nuchdes released by the testing of nuclear weapons and by the operation of nuclear reactors (Faure et al. 1997). 

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